high-speed, real-time recording systems, first edition

7/27/2019 High-Speed, Real-Time Recording Systems, First Edition

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PPPPPentek, Inc.entek, Inc.entek, Inc.entek, Inc.entek, Inc. One Park Way, Upper Saddle River, NJ 07458 Tel: (201) 818-5900 Fax: (201) 818-5904 Email: [email protected] http://www.pentek.com

11111

High-Speed, Real-Time Recording Systems

High-Speed, RHigh-Speed, RHigh-Speed, RHigh-Speed, RHigh-Speed, Real-eal-eal-eal-eal-TimeTimeTimeTimeTimeRRRRRecording Systemsecording Systemsecording Systemsecording Systemsecording Systems

First Edition

RRRRRecording Systemsecording Systemsecording Systemsecording Systemsecording Systems

TTTTTalonalonalonalonalonTMTMTMTMTM RRRRRecordersecordersecordersecordersecorders

ApplicationApplicationApplicationApplicationApplication

Appendix AAppendix AAppendix AAppendix AAppendix A: High-Speed A/D Conver: High-Speed A/D Conver: High-Speed A/D Conver: High-Speed A/D Conver: High-Speed A/D Converterstersterstersters

Appendix B: Switched Serial FAppendix B: Switched Serial FAppendix B: Switched Serial FAppendix B: Switched Serial FAppendix B: Switched Serial FabricsabricsabricsabricsabricsLinksLinksLinksLinksLinks

by

RRRRRodger Hodger Hodger Hodger Hodger H. Hosking. Hosking. Hosking. Hosking. HoskingVice-President & Cofounder of Pentek, Inc.

PPPPPentek, Inc.entek, Inc.entek, Inc.entek, Inc.entek, Inc.One Park Way, Upper Saddle River, New Jersey 07458

Tel: (201) 818-5900 Fax: (201) 818-5904

Email: [email protected] http://www.pentek.com

Copyright 2011 Pentek Inc.

Last updated: December 2011

All rights reserved.

Contents of this publication may not be reproduced in any form without written permission.

Specifications are subject to change without notice.

Pentek, GateFlow, ReadyFow and VIM are registered trademarks of Pentek, Inc.


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Preface

In todays world of high-speed A/D converters operating in the gigahertz range, real-time signal recording has become achallenging task that requires specialized hardware and intelligent application software. When designing a real-time recorder

capable of streaming sustained data to disk at rates of up to 2 GB/sec and higher, the system developer has to consider thelimitations presented by the recorders operating and file systems, the limitations of disk drive technology, the hardware interfaces,

and the RAID controller technology.

Fortunately for the application developer, serial fabrics have emerged to provide the high-speed interfaces required to movethis data; disk drive and RAID HBAs (Host-Bus Adapters) have begun to exploit serial interfaces; finally, the emergence of SSD(Solid State Drive) technology provides a performance level previously unattainable in real-time recording systems. Developing

software that can take advantage of these new technologies presents a challenge that can be met by understanding some keyconcepts required to build a high-speed, real-time recording system.

In this handbook, we will look at some of these techniques and will discuss some of the features that are widely desired insuch a system, including the use of a non-proprietary file system, the use of a client-server architecture, and the presence of a user-friendly API (Application Programming Interface). Finally, we will highlight the latest Pentek TalonTMHigh-Speed Recording

and Playback Systems and an application based on one of them.

More information on high-speed A/Ds is presented in ourCritical Techniques for High-Speed A/D Converters in Real-Time Systemshandbook.More information on high-speed interfaces and gigabit serial links is presented in our

Switched Serial Fabrics Improve System Design handbook.Links to download these and our other handbooks are included on the last page of this handbook.


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Figure 1 Figure 2

IntroductionIntroductionIntroductionIntroductionIntroduction RRRRReal-eal-eal-eal-eal-Time RTime RTime RTime RTime Recordingecordingecordingecordingecording

Desired sustained data transfers up to 2 GB/sec

Limitations to such transfers are presented by the:

Operating system

File system

Disk drive technology

Hardware interfaces

RAID controller technology

Serial fabrics and RAID HBAs provide the high-

speed interfaces to move this data

Solid State Drives provide performance levels

previously unattainable

Real-Time recording captures every sample

provided by the front-end without loss

Desire to move data faster today than could be

done yesterday

The commercial server PC market provides an

excellent choice as a recording platform

CPU technology is constantly advancing in

architecture and processing speed

Memory interfaces can stream data at 10 GB/sec

Serial fabrics provide PCI Express capable of data

rates of 8 GB/sec

When designing a real-time recording system capableof streaming sustained data to disk at rates of up to2 GB/sec, the system developer has to consider the limita-tions presented by the recorders operating and filesystems, the limitations of disk drive technology, thehardware interfaces, and the RAID controller technology.

The high-speed A/D converters we review in

Appendix A that operate at sampling frequencies inexcess of 100 MHz, present real-time signal recordingwith a challenging task that requires specialized hardwareand intelligent application software.

Fortunately for the application developer, the serialfabrics we present in Appendix B provide the high-speedinterfaces required to move this data.

The disk drive and RAID HBAs (Host-Bus Adapt-ers) we will discuss in this chapter also exploit serialinterfaces; finally, the emergence of solid-state drive

technology provides a performance level previouslyunattainable in real-time recording systems.

Developing software that can take advantage ofthese new technologies presents a challenge that can bemet by understanding some key concepts required tobuild a real-time recording system.

In order for a recording system to be consideredreal-time, it must capture every sample of data providedby the front-end with absolutely no loss. This musthappen consistently to create confidence that the systemwill perform in the most mission-critical situations.

When choosing a platform to develop the recordingsystem, it is important to consider the constant requiremen

to move data faster today than could be done yesterday.With this in mind, the commercial server PC marketprovides an excellent platform choice as it benefits fromthe consumer-driven requirement to move, process andstore greater and greater amounts of data every day.

Within the server PC, microprocessor technology isconstantly advancing in both processing speed and inarchitecture. Memory interfaces are capable of streamingdata at rates of 10 GB/sec and higher. Serial fabrics haveprovided PCI Express Gen. 2 with x16 interfaces capableof maximum data rates of 8 GB/sec. Finally, SATA II

provides disk storage rates of 3 Gb/sec to a single drive.

The latest Intel processors are approaching 4 GHzclock rates with hex and octal cores, while memorycontinues to get smaller, cheaper and faster. This providesus with a solid foundation to build on, one that we cangrow with as new high-speed digitizers are introduced.


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Figure 3

Pentek Recording System

RRRRRecording System Overecording System Overecording System Overecording System Overecording System Overviewviewviewviewview

Once the foundation of our recorder is established,it is essential to provide a front-end I/O device that iscapable of steaming data in real-time. As shown in theabove figure, this front-end device typically consists of

one or more high-speed A/D converters or digitalinterfaces that acquire data at a constant rate, and a setof DMA engines that move data off the device. In a real-time system, these DMA engines are the most criticalfeature of the I/O device, since their design dictates howwell this hardware can stream the data and maintain itsreal-time performance requirement.

While the DMA engines are responsible for movingdata off the device, it is the PCI Express engine, inherentwithin the device that provides the path to the serverPCs system memory. It is here that the data is buffered

and made available to the storage device. The server PCsPCIe interface is the path from the I/O device to thesystems memory. It is essential that our I/O deviceprovides a sufficiently fast PCIe interface with thebandwidth required to maintain the data rates of thefront-end.

It is also essential that the I/O device has the abilityto stream data continuously with no software interven-

tion, allowing the hardware to be solely responsible forthe data movement. The latest high-performance I/Odevices provide intelligent DMA chaining that allow thesystem developer to custom-tailor the data flow to

maximize performance and assure the system meets thereal-time requirements.

The DMA engine should allow the user to chainlarge buffers of data and should provide many chains ina link list. If this is provided, it is the applicationdevelopers responsibility to create a large circular buffer,consisting of many chains, each of considerable size.Buffering this data in such a way will allow the system toabsorb any momentary latency hits, which can be causedby a number of external factors.

Buffered data must be sent to disk at data rates that

match those of the front end I/O device. Utilizing off-the-shelf high-performance RAID HBAs, allows thedeveloper to take advantage of the inherent features andfunctionality provided, including selectable RAID-levelcontrol and automated disk recovery facilities. Thechallenge in selecting the best RAID controller lies infinding one that reliably meets the sustained streamingread/write requirements of the system.


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Figure 4

Hard Disk DriveHard Disk DriveHard Disk DriveHard Disk DriveHard Disk Drive HDD RHDD RHDD RHDD RHDD Read/Write Read/Write Read/Write Read/Write Read/Write Ratesatesatesatesates

Figure 5


A hard disk drive (HDD or hard drive or hard disk)is a non-volatile, random access digital data storagedevice. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data ismagnetically read from and written to the platter by read/

write heads that float on a film of air above the platters.

Hard disk drives have decreased in cost and physical

size over the years while dramatically increasing in capacity.Hard disk drives have been the dominant device for datastorage in general-purpose computers since the early 1960s.They have maintained this position because advances intheir recording density have kept pace with storage require-ments.Todays HDDs operate on high-speed serialinterfaces, such as SATA (Serial ATA).

The factors that limit the time to access the data ona hard disk drive are mostly related to the mechanicalnature of the rotating disks and moving heads. Seek timeis a measure of how long it takes the head assembly to

travel to the track of the disk that contains data. Rotationallatency is incurred because the desired disk sector maynot be directly under the head when data transfer isrequested. These two delays are on the order of millisec-onds each.

When developing a recording system, it is importantto recognize the non-linearity of the HDD.

Since the density of an HDD remains constantthrough the disk and the rotation speed remains constant,the read and write rates of a disk fall as HDD accessesmove from the outer edge of the disk to the inner edge.This is due to the fact that the circumference of the

outer edge of a disk is longer than the circumference ofthe inner edge. Since the disk rotates at the same speedfor either edge and the density is the same, the disk willprovide many more bytes per second on the outer edgethan the inner edge.

Since disks present their logical addressing from theouter edge to the inner edge, disk read and write ratesfall as a disk fills up. This can be seen in the above screenplot. RAIDs* built on several HDDs, provide a similarnon-linearity in their data rates. Because of this, it isimperative that the system developer either provide

enough drives in the RAID to meet the maximum data-rate requirement for the entire volume, or limit the sizeof the drive volume to the percentage of disk space thatwill meet the systems data-rate requirement.

* RAID, acronym for Redundant Array of IndependentDisks, is a storage technology that provides increasedreliability and functions through redundancy.


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Figure 6Figure 7

(Courtesy of Intel)

RAID ArrayRAID ArrayRAID ArrayRAID ArrayRAID Array Solid-State DriveSolid-State DriveSolid-State DriveSolid-State DriveSolid-State Drive


As we said previously, RAID arrays built on severalHDDs display a similar non-linearity in data rates.

For example, lets consider the case of designing arecording system that would maintain 500 MB/sec datatransfer rates. The drive volume should be formatted touse about 50% of the available disk capacity. This isdone simply by formatting the drive to the appropriate

size within the operating system.

It is important to leave a sufficient amount of overhead,when selecting the formatted disk amount. In this case,while the system may keep up with the 500 MB/secrequirement for almost seventy percent of the drive volume,fifty percent is a much safer number, provided it suppliesenough storage for the application.

There are other critical factors to consider to assurereal-time performance when designing a recording system.When dealing with non-real-time operating systems like

Windows and Linux, it is important to minimize theoperating systems impact on the recording application.The amount of processor intervention in the recordingsoftware can be minimized by dedicating the data transfersto the DMA controllers and simply leaving the processorto manage the data flow. The developer should also elevatethe priorities of real-time tasks within the applicationand keep background tasks at lower priorities to avoidimpacting the recorders performance.

A solid-state drive (SSD) is a data storage device thatuses solid-state memory to store data with the intentionof providing access in the same manner as a traditionalHDD. SSDs are distinguished from traditional HDDs,which are electromechanical devices containing spinningdisks and movable read/write heads. Instead, SSDs usemicrochips which retain data in non-volatile memory

chips and contain no moving parts.Compared to HDDs, SSDs are typically less susceptible

to shock and vibration, are silent, have much lower accesstime and latency, do not display data rate non-linearity,and typically support a limited number of writes over thelife of the device. SSDs use the same interface as hard diskdrives, thus easily replacing them in most applications.

Most SSDs use NAND-based flash memory, whichretains memory even without power. SSDs using volatilerandom-access memory (RAM) also exist for situationswhich require even faster access, but do not necessarily need

data persistence after power loss, or use external poweror batteries to maintain the data after power is removed.

A hybrid drive combines the features of an HDDand an SSD into one unit, containing a large HDD, witha smaller SSD cache to improve performance of frequentlyaccessed files. These are not suitable for data-intensivework, nor do they offer the other advantages of SSDs.


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Client-SerClient-SerClient-SerClient-SerClient-Server Architecturever Architecturever Architecturever Architecturever Architecture

Figure 8

Local or Remote Socket

connection

SERVER

Sockets

Record/Play Server Application

Server Operating System

NTFS

Record/Play Client Application

Sockets

Client Operating System

NTFS

CLIENT

API

Client API

When designing a real-time recorder, it is importantto provide the user a control interface that is intuitiveand easy to use. The easiest way to achieve this is througha GUI (Graphical User Interface). A GUI enables theuser to control the recorder by pushing virtual buttonswith a mouse or via a touch screen. The GUI shouldallow the user to not only control the recorder, but shouldalso provide facilities to manage the data files, utilities tomonitor and analyze the signals being recorded, andshould provide constant status information to the user.

The GUI should have the ability to run either locallyon the recorder or remotely on an independent PC orother device. Being able to run on a remote device allowsthe user the ability to put the recorder in an environmentthat may not be appropriate for the operator. This allowsthe recorder to be close to the sensor or antenna source,placing the A/D or digital I/O interface near the signalof interest.

The best way to provide both local and remote controlof the recorder is through a client-server architecture.This architecture provides a socket-based communicationlink between the client GUI and the server recordingapplication, separating the real-time portion of therecorder (the Server) from the non-real-time portion(the Client). The client can then connect to the server,whether the client sits on the server PC itself or on a PCthat is connected to the server over Ethernet.

By sending messages to the server, the client GUIcan control all aspects of the recorder. This includes theability to start and stop recordings, to set up front-endhardware parameters, to monitor incoming signal infor-mation and to request status information from the server.The interface for this messaging structure should bedefined in an API (Application Programming Interface).While the API is used by the GUI to communicate withthe server, it can also be provided to the user in a formatthat allows the recorder to be integrated into a larger system.

(More on the next page


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User APIUser APIUser APIUser APIUser API

By providing a user API, the recorder becomes more

than a stand-alone system, it serves as a user developmentplatform as well. This allows different types of users theflexibility they may desire, while providing the out-of-the-box experience of a system all in one product.

In order to define an API that can be easily integratedinto a larger application, it is important to define theAPI routines in a simple and straightforward manner.These routines should abstract the user from the detailsof the message building, the socket interface and otherintricacies of the recording architecture. Error checkingshould be included in the recording server, allowing the

user to receive error codes in response to failed messages.

The API should not only contain routines thatcontrol the interface, but should also contain routinesthat obtain general status information, perform built-in-test facilities and allow the user to view snapshots of thedata prior to and during recording. Combining thesefacilities provides the user with the ability to create a well-featured recorder application as part of a bigger system.

Other Design ConsiderationsOther Design ConsiderationsOther Design ConsiderationsOther Design ConsiderationsOther Design Considerations

One of the problems engineers often have to dealwith after recording data in the field is the issue ofoffloading the mission data to a system that will performthe analysis, post-processing and archiving. This processshould be made simple and quick, minimizing thedown-time that field engineers have during the offloadprocess. There are several strategies to consider here.

The use of a non-proprietary file system, such asNTFS, to record data provides the ability to avoid theoffload process required by systems that use a proprietaryfile system. In this situation, the user can instantly accessrecordings as standard files on the recording device itself.By providing the disk storage as hot-swappable SATAdrives, field engineers can simply swap out disks filledwith mission data for fresh ones and transport only thedata disks to their analysis system. By adding a RAIDcontroller to the analysis system, similar to the one

designed into the recorder, data can instantly be accessed

on the analysis machine, avoiding the offload processcompletely. Additionally, the recorder is instantlyavailable to collect new data as soon as the disk swap ismade, allowing for almost no downtime in the field.

Data files that are provided to the analysis systemmust contain critical information related to the record-ing event itself. This can be accomplished by adding asmall header to the beginning of each data file. Theparameters stored in this header should be well-defined,containing all of the critical information about therecording, including time-stamping, I/O module

settings, and general information about the recordingsession itself. Additionally, user-settable fields should bereserved, allowing the user to add other information tothe file header.

The information stored in the file header can beused by system analysis and signal visualization tools.Integrating these tools into the recorder provides arobust product; one that allows field engineers the abilityto verify their signal integrity prior to, during, and aftera recording session.

SummarSummarSummarSummarSummaryyyyy

It is important to consider all of the qualities inherentin a high-performance, user friendly system, when creatinga real-time recorder. The use of a high-performance PCallows us to take advantage of the latest technology, whilethe use of a non-proprietary file system provides us withthe convenience of immediate access to the data files. AGUI provides an easy-to-use control panel, while theavailability of a user API enables the integration of therecorder into a larger system application.

By building this platform on a well-defined client-server architecture, the developer can provide both ofthese facilities to the user. Integrating this with a high-performance front-end I/O module and the latest technol-ogy offered by the PC market assures that the system willprovide a satisfying experience with excellent reliability.



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TTTTTalonalonalonalonalonTMTMTMTMTM RRRRRecordersecordersecordersecordersecorders

TTTTTalonalonalonalonalonHigh-Speed RHigh-Speed RHigh-Speed RHigh-Speed RHigh-Speed Recording Systems: Flexible and Deployable Solutionsecording Systems: Flexible and Deployable Solutionsecording Systems: Flexible and Deployable Solutionsecording Systems: Flexible and Deployable Solutionsecording Systems: Flexible and Deployable Solutions

Systems Include: High-performance Windowsworkstation

High-performance Intelprocessor

Pentek SystemFlowrecording software with

graphical user interface

SystemFlow virtual oscilloscope and spectrum

analyzer

Supported RAID levels of 0, 1, 5, 6, 10 and 50

Time stamping support

Detailed technical documentation

Systems Benefits: Complete turnkey systems

Rack-mountable and portable form factors

C-callable API for integration into application

Sustained recording rates of up to 2 GB/sec

Recording to non-proprietary NTFS file system for

easy and immediate data access

Ideal for communications, radar, wireless, SIGINT,

telecom and satcom

They are easy to use right out-of-the-box

Can be controlled over the Ethernet or the Internet

Figure 9 Figure 10

Talon High-Speed Recording Systems eliminate thetime and risk associated with new technology systemdevelopment. With increasing pressure in both thedefense and commercial arenas to get to the market first,todays system engineers are looking for more completeoff-the-shelf system offerings.

Out of the box, these systems arrive complete with afull-featured virtual operator control panel ready forimmediate data recording and/or playback operation.

Because they consist of modular COTS board-levelproducts and flexible control software, they are easilyscalable to larger multichannel data acquisition andrecording applications requiring sustained, aggregaterecording rates of up to 2 GB/sec.

For example, they can be used as the data acquisi-tion resource for embedded systems in real-time digitalsignal processing applications. A complete suite ofsoftware development tools simplifies custom system

integration.

Depending on model, the Pentek offerings are fullyintegrated systems featuring a range of A/D and D/Aresources or digital I/O with high-speed disk arrays.

Since these systems are built on a Windowsworkstation, users can easily install post-processing andanalysis tools to operate on the recorded data.

Pentek systems provide a flexible architecture thatcan be easily customized to meet user needs. MultipleRAID levels of 0, 1, 5, 6, 10 and 50, provide a choicefor the required level of redundancy.

Penteks High-Speed Recording Systems are availableas Lab Systems, Portable Systems and Rugged Systems.

RTS Lab Systems are housed in a 19 in. rack-mount-

able chassis in a PC server configuration. They aredesigned for commercial applications in a lab or officeenvironment.

RTS Portable Systems are available in a smallbriefcase-sized enclosure with an integral LCD displayand keyboard. They, too, provide a PC server configura-tion and are designed for commercial field applications wheresize and weight is of paramount importance.

RTR Rugged Systems are housed in a 19 in. rack-mountable chassis in a PC server configuration. Theyare built to survive shock and vibration and they targetoperation in harsh environments and remote locationsthat may be unsuitable for humans.

RTS High-Speed RecordingSystems are designed forcommercial applications.

RTR High-Speed RecordingSystems are designed for harsh

environments.


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PPPPPentek SystemFlow Architectureentek SystemFlow Architectureentek SystemFlow Architectureentek SystemFlow Architectureentek SystemFlow Architecture

Figure 11

Local or Remote Socketconnection

SERVER

Sockets

WindowsDrivers

SystemFlowCommand

Processor

SystemFlow Record/Play

Server Application

Windows Operating System

NTFS

User

Control

Block

User

Proc.Block

LabVIEW

SignalViewer

SystemFlow JAVA

Record/Play GUI Application

SocketsSystemFlow JAVA

Client API

Client Operating System(Windows/Linux/Other)

NTFS

CLIENT

API

TTTTTalon Ralon Ralon Ralon Ralon Recordersecordersecordersecordersecorders

Client/Server Architecture

As shown above, the SystemFlow architectureprovides for easy communication between the recording

system Client PC on the left and the Server on the right.

Client/Server Communication

Client and Server communicate through a standardsocket connection. This arrangement enables the Server toprovide real-time recording and playback functions that canbe controlled from a local or a remote Client. It also allowsClient and Server to run on different operating systems.

Function Libraries

The function libraries and tools for controlling therecording and playback functions include the Applica-tion Programming Interface, the Graphical User Inter-face and the integrated Signal Viewer.

SystemFlow API

The SystemFlow API allows developers to configure andcustomize the system interfaces and operation. Source code issupplied for all client API functions. A well-defined set ofplugins allows the user to extend server API functions.

SystemFlow GUI

The SystemFlow architecture features a Windows-based GUI that provides a simple means to configure

and control the system. Custom configurations can bestored as profiles and later loaded when needed, allowingthe user to select preconfigured settings with a single click.

SystemFlow Signal Viewer

SystemFlow also includes signal viewing and analysistools that allow the user to monitor the signal prior to,during, and after a recording session. These tools includea virtual oscilloscope and a virtual spectrum analyzer.More information on the Signal Viewer is provided onthe next page.

NTFS File System

The NTFS file management system provides immediateaccess to the recorded data, thereby eliminating time-consuming data conversion processes required withproprietary file management systems. It also eliminatesthe need for custom hardware and software platformswhere the recorded data may need to be physicallytransported for conversion.


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PPPPPentek SystemFlow Graphical User Interentek SystemFlow Graphical User Interentek SystemFlow Graphical User Interentek SystemFlow Graphical User Interentek SystemFlow Graphical User Interfacefacefacefaceface

Figure 12

Signal Viewer

Recorder Interface Hardware ConfigurationInterface


The SystemFlowSignal Viewerincludes a virtualoscilloscope and spectrum analyzer for signal monitoringin both the time and frequency domains. It is extremelyuseful for previewing live inputs prior to recording, andfor monitoring signals as they are being recorded to helpensure successful recording sessions. The viewer can alsobe used to inspect and analyze the recorded files after therecording is complete.

Advanced signal analysis capabilities include automaticcalculators for signal amplitude and frequency, secondand third harmonic components, THD (total harmonicdistortion) and SINAD (signal to noise and distortion).With time and frequency zoom, panning modes and dualannotated cursors to mark and measure points of interest,the SystemFlow Signal Viewer can often eliminate theneed for a separate oscilloscope or spectrum analyzer inthe field.

The Pentek SystemFlow recording software providesall the tools for controlling all Pentek high-speed real-time data acquisition and recording systems. SystemFlowsoftware allows developers to configure and customizesystem interfaces and behavior.

TheRecorder Interface includes configuration, record,playback and status screens, each with intuitive controlsand indicators. The user can easily move between screensto set configuration parameters, control and monitor arecording, play back a recorded signal and monitorboard temperatures and voltage levels.

The Hardware Configuration Interface providesentries for input source, center frequency, decimation, aswell as gate and trigger information. All parameterscontain limit-checking and integrated help to provide aneasier-to-use, out-of-the-box experience.


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RRRRRecording Dataflowecording Dataflowecording Dataflowecording Dataflowecording Dataflow

Figure 13

System Memory

Recording System SBC/MB

CPURecording System

RAID Controller

200 MHZ

16-Bit A/D

200 MHZ

16-Bit A/D

Pentek Transceiver Board TIMING BUS GENERATOR

Clock / Sync / Gate / PPS

PCI Express

Interface

RF/IFAnalog Input

Channel # 1

RF/IFAnalog Input

Channel # 2

Sample Clk/Reference Clk In

Gate/Trigger/Sync/PPS

A/D Clock/Sync Bus

Digital IF

Channel # 1

Digital IF

Channel # 2

2 Channels of Digital Data

Being Transferred Over APCI Express Interface


Being Transferred Over ASATA Interface

PCI Express Interface PCI Express Interface

RAIDController

SATAInterface

DDC

#1

DDC

#2

Single

VolumeRAID 0Storage

Array


Shown in this diagram is the dataflow during atypical recording session.

The Pentek Transceiver Board contains a 2-channel200 MHz A/D for digitizing two input analog channels.The digitized outputs are downconverted by the twoDDCs (Digital Downconverters) and moved on to thePC system memory via the PCI Express interface. Both

the DDCs and the PCIe interface are implemented inthe boards FPGA.

Data then moves from the system memory to theRecording System RAID Controller and is then recordedto disk via the SATA interface. DMA controllers conductall data transfers, bypasssing the CPU for guaranteed real-time operation.


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System Memory

Playback System SBC/MB

CPUPlayback System

RAID Controller

800 MHZ

16-Bit D/A

800 MHZ

16-Bit D/A

Pentek Transceiver Board TIMING BUS GENERATOR

Clock / Sync / Gate / PPS

PCI Express

Interface

RF/IFAnalog Output

Channel # 1

RF/IFAnalog Output

Channel # 2

Sample Clk/Reference Clk In

Gate/Trigger/Sync/PPS

D/A Clock/Sync Bus

Digital IF

Channel # 1

Digital IF

Channel # 2


Being Transferred Over APCI Express Interface


Being Transferred Over ASATA Interface

PCI Express Interface PCI Express Interface

RAIDController

SATAInterface

DUC

#1

DUC

#2

Single

VolumeRAID 0Storage

Array

Playback DataflowPlayback DataflowPlayback DataflowPlayback DataflowPlayback Dataflow

Figure 14


During a playback session, data stored on disk movesthrough the SATA interface of the Playback SystemRAID Controller. From there, data is passed to the PCsystem memory through the PCIe interface and then tothe Pentek Transceiver board through its PCIe interface, allvia hardware DMA controllers for real-time operation.

This board also contains DUCs (Digital Upconverters)which upconvert the data to the original IF frequencybands. Two 800 MHz D/As convert the data to analogform and provide signals that are identical to theanalog signals that were originally recorded.

These can be further analyzed with any Windows-compatible analysis software.


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Figure 15

2-2-2-2-2-Channel RF/IF 125 MS/sec RChannel RF/IF 125 MS/sec RChannel RF/IF 125 MS/sec RChannel RF/IF 125 MS/sec RChannel RF/IF 125 MS/sec Rack-mount Rack-mount Rack-mount Rack-mount Rack-mount Recorderecorderecorderecorderecorder

Model RTS 2701Model RTS 2701Model RTS 2701Model RTS 2701Model RTS 2701

CH 1In

125 MHz14-bit A/D

MODEL

7641-420

CH 2In

Out

125 MHz14-bit A/D

SampleClock A In

CLOCK &SYNC

GENERATOR

Clock/SyncBus

XTALOSC B

XTALOSC B

Sample

Clock B InTTL Gate/TriggerIn

TTL SyncIn

DIGITALDOWN-

CONVERTER

DIGITALDOWN-

CONVERTER

DIGITALUPCONVERTER

INTELPROCESSOR

SYSTEM DRIVE

A

500 MHz16-bit D/A

DDRSDRAM

HOST PROCESSOR

RAID

DATA DRIVES DATA DRIVES


MODEL RTS 2701

USB

GigabitEthernet

PS/2Keyboard

PS/2Mouse

VideoOutput


The Talon RTS 2701 is a turnkey, multiband record-ing and playback system that allows the user to recordand reproduce high-bandwidth signals. The RTS2701 provides sustained recording rates of up to 480MB/sec in a dual-channel configuration and is ideal for theuser that requires a powerful rack-mount recording system.

The heart of the RTS 2701 is the Pentek Model7641-420 multiband transceiver, which includes A/Dand D/A converters, digital upconverters (DUCs),

digital downconverters (DDCs), and an FPGA-installedIP core. The architecture allows the system engineer to takefull advantage of modern technology in a turnkey system.

Optional GPS time and position stamping allowsthe user to record this critical signal information.

Included with this system is Penteks SystemFlowRecording Software. A software API is provided that

allows users to integrate control of this system intotheir system. Built on a Windows XP Professionalworkstation, the RTS 2701 allows the user to install postprocessing and analysis tools to operate on the recordeddata. The RTS 2701 records data to the native NTFSfile system, providing immediate access to the recordeddata. Data can be offloaded via gigabit Ethernet, or USB2.0 ports. Additionally, data can be copied to disk, usingthe 8X double layer DVD+R/RW drive.

A high-performance PCI Express SATA RAIDcontroller connects to multiple SATA hard drives tosupport storage to 4 terabytes and real-time sustainedrecording rates to 480 MB/sec.

Penteks multiband recorder system provides a flexiblearchitecture that is easily customized to meet the usersneeds. Multiple RAID levels, including 0, 1, 5, 6, 10 and50, provide a choice for the required level of redundancy


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Figure 16

Channels

In

Channels

Out

200 MHz

16-bit A/D0 to 8

Channels

DIGITALDOWN-

CONVERTERDecimation:2 to 65,536

INTELPROCESSOR

SYSTEM DRIVEDDR

SDRAM

HOST PROCESSOR

RUNNING SYSTEMFLOW

UP TO 20 TB RAID



MODEL RTS 2706

USB 2.0

GigabitEthernet

PS/2Keyboard

PS/2Mouse

Video

Output

2

6

eSATA2

GPS

Antenna(Optional)

800 MHzor 1.25 GHz16-bit D/A

0 to 8

Channels

DIGITAL

UP-CONVERTERDecimation:2 to 65,536


8-8-8-8-8-Channel RF/IF 200 MS/sec RChannel RF/IF 200 MS/sec RChannel RF/IF 200 MS/sec RChannel RF/IF 200 MS/sec RChannel RF/IF 200 MS/sec Rack-mount Rack-mount Rack-mount Rack-mount Rack-mount Recorderecorderecorderecorderecorder

Model RTS 2706COTS

Model RTS 2706Rugged


The Talon RTS 2706 is a turnkey, multibandrecording and playback system for recording andreproducing high-bandwidth signals. The RTS 2706uses 16-bit, 200 MHz A/D converters and providessustained recording rates up to 1600 MB/sec in four-channelconfiguration.

The RTS 2706 uses Penteks high-powered Virtex-6-basedCobalt modules, that provide flexibility in channel count,with optional DDC (Digital Downconversion) capabilities.

Optional 16-bit, 800 MHz D/A converters with DUC(Digital Upconversion) allow real-time reproduction ofrecorded signals.

A/D sampling rates, DDC decimations and band-widths, D/A sampling rates and DUC interpolations areamong the GUI-selectable system parameters, providinga fully-programmable system capable of recording andreproducing a wide range of signals.

Included with this system is Penteks SystemFlowrecording software. Optional GPS time and positionstamping allows the user to record this critical signalinformation.

Built on a Windows 7 Professional workstation withhigh performance Intel CoreTM i7 processor the RTS 2706allows the user to install post processing and analysistools to operate on the recorded data. The system recordsdata to the native NTFS file system, providing immediate

access to the recorded data.

The RTS 2706 is configured in a 4U 19" rack-mount-able chassis, with hot-swap data drives, front panel USBports and I/O connectors on the rear panel. Systems arescalable to accommodate multiple chassis to increasechannel counts and aggregate data rates. All recorderchassis are connected via Ethernet and can be controlledfrom a single GUI either locally or from a remote PC.


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Figure 17


2-2-2-2-2-Channel 10 Gigabit Ethernet RChannel 10 Gigabit Ethernet RChannel 10 Gigabit Ethernet RChannel 10 Gigabit Ethernet RChannel 10 Gigabit Ethernet Rack-mount Rack-mount Rack-mount Rack-mount Rack-mount Recorderecorderecorderecorderecorder

Ch 1In / Out 10G

Ethernet INTELPROCESSOR

SYSTEM DRIVEDDR

SDRAM

HOST PROCESSOR

RUNNING SYSTEMFLOW

UP TO 20 TB RAID



MODEL RTS 2715

USB 2.0

GigabitEthernet

PS/2Keyboard

PS/2Mouse

VideoOutput

2

6

eSATA2

GPSAntenna(Optional)

Ch 2In / Out 10G

Ethernet


The Talon RTS 2715 is a complete turnkey recordingsystem for storing one or two 10 gigabit Ethernet (10 GbE)streams. It is ideal for capturing any type of streamingsources including live transfers from sensors or data from othercomputers and supports both TCP and UDP protocols.

Two rear panel SFP+ LC connectors for 850 nmmulti-mode or single-mode fibre cables, or CX4 connec-tors for copper twinax cables accommodate all popular10 GbE interfaces.

Optional GPS time and position stamping accuratelyidentifies each record in the file header.

The RTS 2715 includes the SystemFlow RecordingSoftware that provides a simple and intuitive means toconfigure and control the system. Custom configurations canbe stored as profiles and later loaded as needed, allowing theuser to select preconfigured settings with a single click.

Built on a server-class Windows 7 Professionalworkstation, the RTS 2715 allows the user to installpost-processing and analysis tools to operate on therecorded data. The RTS 2715 records data to the nativeNTFS file system, providing immediate access to therecorded data.

The RTS 2715 is configured in a 5U 19" rack-mount-able chassis, with hot-swap data drives, front panel USBports and I/O connectors on the rear panel. The 24 hot-

swappable HDDs provide a storage capacity of 20 TB.

Systems are scalable to accommodate multiple chassis toincrease channel counts and aggregate data rates. All recorderchassis are connected via Ethernet and can be controlled froma single GUI either locally or from a remote PC.


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Figure 18

2-2-2-2-2-Channel RF/IF 125 MS/sec PChannel RF/IF 125 MS/sec PChannel RF/IF 125 MS/sec PChannel RF/IF 125 MS/sec PChannel RF/IF 125 MS/sec Pororororortable Rtable Rtable Rtable Rtable Recorderecorderecorderecorderecorder


CH 1In

125 MHz14-bit A/D

MODEL

7641-420

CH 2

In

Out

125 MHz14-bit A/D

SampleClock A In

CLOCK &

SYNCGENERATOR

Clock/SyncBus

XTALOSC B

XTALOSC B

Sample

Clock B InTTL Gate/TriggerIn

TTL SyncIn

DIGITALDOWN-

CONVERTER

DIGITAL

DOWN-CONVERTER

DIGITAL

UPCONVERTER

INTEL

PROCESSOR

SYSTEM DRIVE

A

500 MHz16-bit D/A

DDRSDRAM

HOST PROCESSOR

RAID



HIGH RESOLUTIONVIDEO DISPLAY

MODEL RTS 2721

USB

Gigabit

Ethernet

PS/2

Keyboard

PS/2Mouse

Aux VideoOutput


The Talon RTS 2721 is a turnkey real-time record-ing and playback instrument supplied in a convenientbriefcase-size package that weighs just 30 pounds. Builton the Windows XP professional workstation, it includesa dual-core Xeon processor, a high-resolution 17-inchLCD monitor and a high-performance SATA RAIDcontroller.

The RTS 2721 utilizes the Model 7641 multibandtransceiver PCI module with two 14-bit 125 MHzA/Ds, ASIC DDC, and DUC with two 16-bit 500 MHzD/As. The factory-installed IP core 420 provides adual wideband DDC and expands the decimation rangeof the ASIC DDC. The core also includes an interpola-tion filter that expands the interpolation factor of theASIC DUC.

The Model 7641-420 combines downconverter andupconverter functions in one PCI module and offersreal-time recording capabilities.

Fully supported by Penteks SystemFlow recordingsoftware, the RTS 2721 uses a native NTFS record/play-back file format for easy access by user applications foranalysis, signal processing, and waveform generation.File headers include recording parameter settings andtime stamping so that the signal viewer correctly formatsand annotates the displayed signals.

A high-performance PCI Express SATA RAIDcontroller connects to multiple SATA hard drives tosupport storage to 3 terabytes and real-time sustainedrecording rates up to 480 MB/sec.

Penteks portable recorder instrument provides aflexible architecture that is easily customized to meetspecial needs. Multiple RAID levels, including 0, 1, 5, 6,10 and 50, provide a choice for the required level ofredundancy. With its wide range of programmabledecimation and interpolation, the system supports signalbandwidths from 8 kHz to 60MHz.


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INTEL CORE i7PROCESSOR

SSDSYSTEM DRIVE

DDRSDRAM

WINDOWS HOST PROCESSOR

RAID DATA STORE

S SD DRIVES S SD DRIVES

SSD DRIVES SSD DRIVES

HIGH RESOLUTIONVIDEO DISPLAY

8x USB 2.0

1x GigabitEthernet

Aux VideoVGA Output

MODEL RTR 2726

ChannelsIn

ChannelsOut

2x eSATA 3

200 MHz16-bit A/D

Up to 4Channels

DIGITAL DOWNCONVERTER

DEC: 2 to 64K

800 MHz16-bit D/A

Up to 2Channels

DIGITAL UPCONVERTER

INT: 2 to 512K

2x USB 3.0

4-4-4-4-4-Channel RF/IF 200 MS/sec RChannel RF/IF 200 MS/sec RChannel RF/IF 200 MS/sec RChannel RF/IF 200 MS/sec RChannel RF/IF 200 MS/sec Rugged Pugged Pugged Pugged Pugged Pororororortable Rtable Rtable Rtable Rtable Recorderecorderecorderecorderecorder

Model RTR 2726Model RTR 2726Model RTR 2726Model RTR 2726Model RTR 2726


Figure 19

The Talon RTR 2726 is a turnkey, multiband record-ing and playback system that allows the user to recordand reproduce high-bandwidth signals with a lightweight,portable and rugged package. The RTR 2726 providessustained recording rates of up to 1600 MB/sec in a four-channel system and is ideal for the user who requiresboth portability and solid performance in a compactrecording system.

The RTR 2726 is supplied in a small footprintportable package measuring only 16.9" W x 9.5" D x13.4" H and weighing just 30 pounds. With measurementssimilar to a small briefcase, this portable workstationincludes an Intel Core i7 processor a high-resolution17" LCD monitor, and a high-performance SATA RAIDcontroller.

At the heart of the RTR 2726 are Pentek Cobalt

Series Virtex-6 software radio boards featuring A/D andD/A converters, DDCs (Digital Downconverters),

DUCs (Digital Upconverters), and complementaryFPGA IP cores. This architecture allows the systemengineer to take full advantage of the latest technologyin a turnkey system.

Optional GPS time and position stamping allowsthe user to record this critical signal information.

Built on a Windows 7 Professional workstation,the RTR 2726 allows the user to install post processingand analysis tools to operate on the recorded data. The

RTR 2726 records data to the native NTFS file system,providing immediate access to the recorded data.

Because SSDs operate reliably under conditions ofvibration and shock, the RTR 2726 performs well inground, shipborne and airborne environments. Theeight hot-swappable SSDs provide a storage capacity of upto 4 TB. The drives can be easily removed or exchangedduring or after a mission to retrieve recorded data.


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Figure 20


8-8-8-8-8-Channel RF/IF 200 MS/Sec RChannel RF/IF 200 MS/Sec RChannel RF/IF 200 MS/Sec RChannel RF/IF 200 MS/Sec RChannel RF/IF 200 MS/Sec Rugged Rugged Rugged Rugged Rugged Rack-mount Rack-mount Rack-mount Rack-mount Rack-mount Recorderecorderecorderecorderecorder

ChannelsIn

ChannelsOut

200 MHz16-bit A/D

0 to 8Channels

DIGITALDOWN-


INTELPROCESSOR

SYSTEM DRIVEDDR

SDRAM

HOST PROCESSOR

RUNNING SYSTEMFLOW

UP TO 24 TB RAID



MODEL RTR 2746

USB 2.0

GigabitEthernet

PS/2Keyboard

PS/2Mouse

VideoOutput

2

6

eSATA2

GPS

Antenna(Optional)

800 MHzor 1.25 GHz16-bit D/A

0 to 8Channels

DIGITALUP-



The Talon RTR 2746 is a turnkey, multiband recordand playback system that is built to operate under harshconditions. Designed to withstand high vibration andoperating temperatures, the RTR 2746 is intended formilitary, airborne and UAV applications requiring a ruggedsystem. With scalable A/Ds, D/As and SSD (solid-statedrive) storage, the RTR 2746 can be configured to streamdata to and from disk at rates as high as 1600 MB/sec.

The RTR 2746 uses Penteks high-powered Virtex-6-

based Cobalt boards, that provide flexibility in channelcount with optional digital downconversion capabilities.Optional 16-bit, 800 MHz D/A converters with digitalupconversion allow real-time reproduction of recorded signals.

A/D sampling rates, DDC decimations and band-widths, D/A sampling rates, and DUC interpolations areamong the GUI-selectable system parameters, providing afully programmable system.

The RTR 2746 is delivered in a 4U 19" rugged rack-mountable chassis. Designed to MIL-STD-810F, it is builtto survive shock and vibration. Stress to the motherboard andCPU heatsink is mitigated by multipe attachment points tostabilize the PCB. All fasteners and connectors are retainedwith locking mechanisms and shock-isolated drive bays.

High-speed, high-volume, thermally-controlled fansoffer maximum airflow and are designed for long life.Additionally, extended temperature operation is possible

with an optional high-temperature CPU.

All recorder chassis are connected via Ethernet and canbe controlled from a single GUI either locally or from aremote PC. Multiple RAID levels, including 0, 1, 5, 6, 10and 50, provide a choice for the required level of redundancy.Up to 48 removable SATA SSD drives are available,allowing up to 24 terabytes of real-time data storage spacein a single 4U chassis.


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2-2-2-2-2-Channel 10 Gigabit Ethernet RChannel 10 Gigabit Ethernet RChannel 10 Gigabit Ethernet RChannel 10 Gigabit Ethernet RChannel 10 Gigabit Ethernet Rugged Rugged Rugged Rugged Rugged Rack-mount Rack-mount Rack-mount Rack-mount Rack-mount Recorderecorderecorderecorderecorder


The Talon RTR 2755 is a complete turnkey recordingsystem for storing one or two 10 gigabit Ethernet (10 GbE)streams. It is ideal for capturing any type of streamingsources including live transfers from sensors or data from othercomputers and supports both TCP and UDP protocols.

Using highly-optimized solid-state drive storagetechnology, the system guarantees loss-free performanceat aggregate recording rates up to 2 GB/sec.

Two rear panel SFP+ LC connectors for 850 nmmulti-mode or single-mode fibre cables, or CX4 connec-tors for copper twinax cables accommodate all popular10 GbE interfaces.

Optional GPS time and position stamping accuratelyidentifies each record in the file header.

The RTR 2755 includes the SystemFlow RecordingSoftware that provides a simple and intuitive means to

configure and control the system. Custom configurations canbe stored as profiles and later loaded as needed, allowing theuser to select preconfigured settings with a single click.

Built on a server-class Windows 7 Professionalworkstation, the RTR 2755 allows the user to installpost-processing and analysis tools to operate on therecorded data. The RTR 2755 records data to the nativeNTFS file system, providing immediate access to therecorded data.

Because SSDs operate reliably under conditions ofvibration and shock, the RTR 2755 performs well inground, shipborne and airborne environments. Thetwelve hot-swappable SSDs provide a storage capacity ofup to 3 TB. The drives can be easily removed or exchangedduring or after a mission to retrieve recorded data.

Figure 21

Ch 1In / Out 10G

Ethernet INTELPROCESSOR

SSDSYSTEM DRIVE

DDRSDRAM

WINDOWS HOST PROCESSOR

RAID DATA STORE



MODEL RTR 2755

USB 2.0

GigabitEthernet

PS/2Keyboard

PS/2Mouse

VideoOutput

2

6

eSATA2

GPSAntenna(Optional)

Ch 2In / Out 10G

Ethernet


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3-3-3-3-3-Channel Phase-Synchronous Scanning and RChannel Phase-Synchronous Scanning and RChannel Phase-Synchronous Scanning and RChannel Phase-Synchronous Scanning and RChannel Phase-Synchronous Scanning and Recording Systemecording Systemecording Systemecording Systemecording System


Figure 22

Ethernet Hub

Ethernet

Ethernet

Ethernet

Ethernet

RF Tuner #1

RF Tuner #2

#1 In

#3 In

#2 In

RF Tuner #3

Antenna #1

Antenna #2

Antenna #3

RF

RF

IF

IF

CLK

CLK

RefClock

IF Out

IF Out

IF Out

Ext Ref In

10 MHzRef Out

GPS Antenna

TALON

RTS 2706

RECORDER

KVM Switch

USB

KVM Output

Utilizing the Talon RTS 2706 Configurable Record-ing System discussed previously, this system provides theability to scan three RF channels synchronously andrecord the digitized signals to disk.

In addition to the RTS 2706, this system includesthree commercially available rack-mount RF tuners anda KVM switch. An Ethernet hub is included to allow theRTS 2706 to control the tuners through their Ethernetinterface. Each tuners RJ45 Ethernet port is wired to theEthernet hub which, in turn, is wired to one of theEthernet ports of the RTS 2706.

The KVM switch is wired directly to one of theUSB ports of the RTS 2706. This connection allows forthe RTS 2706 to be controlled from a keyboard and

mouse attached to the KVM switch. An LCD displaycan also be attached to this switch for viewing the signalsbefore, during and after the recording.

The three RF tuners are set up to have their IFoutputs connected to the three input channels of theRTS 2706 recorder. The recorder is equipped with theCobalt Model 78621 PCIe 3-Channel 200 MHz A/Dwith factory-installed 3-Channel DDC in the Virtex-6FPGA. The DDCs offer a decimation range of 2x to65,536x providing a wide range to satisfy most applications.

The 10 MHz reference clock is distributed to the A/Dsof the 78621 and also to RF Tuner #1 which, in turn,supplies it to RF Tuners #2 and #3. In addition, the RFLO and the IF LO are distributed from RF Tuner #1 tothe others. This arrangement achieves phase-synchronousscanning to meet the specification of this application.

The 10 MHz reference clock is generated by the

GPS board which is located in one of the PCIe slots ofthe RTS 2706 recorder. A GPS antenna is supplied withthe system and provides for accurate position and time-stamping of each recording.


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3-3-3-3-3-Channel Phase-Synchronous Scanning and RChannel Phase-Synchronous Scanning and RChannel Phase-Synchronous Scanning and RChannel Phase-Synchronous Scanning and RChannel Phase-Synchronous Scanning and Recording Systemecording Systemecording Systemecording Systemecording System

Figure 23

FREQUENCYBAND

TIMEFigure 24

#3

#3

#3

#1#1

#1#2

#2

#2

The Pentek SystemFlow recording software suppliedwith this system provides all the features discussedpreviously. In addition, controls for a scanning facilityare included. The screen shot shown here allows the userto define the start and stop frequencies of the scan, thefrequency bin size, dwell time, and other scan parametersthat may be important to a particular scan.

A typical example of a three-channel phase-synchro-nous scan is shown above.

This system has been succesfully built, tested anddelivered by Pentek as Model RTS 2706-013.


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High Speed A/D ConverHigh Speed A/D ConverHigh Speed A/D ConverHigh Speed A/D ConverHigh Speed A/D Converter Markter Markter Markter Markter Marketsetsetsetsets


Figure 25

New Monolithic A/D TNew Monolithic A/D TNew Monolithic A/D TNew Monolithic A/D TNew Monolithic A/D Technologyechnologyechnologyechnologyechnology

Figure 26

Markets for high-speed A/D converters are significantin size and many are growing rapidly. New marketsemerge regularly based on A/D technology advances,lower costs, and the general trend of replacing oldermechanical and analog systems with DSP (digital signalprocessing) systems.

DSP offers significant advantages for handling signalcomplexity, communications security, improved accuracy

and reliability, reduced size, weight and power.Commercial users of high-speed A/Ds include

wireless mobile communication systems, airline radarsystems, air traffic control towers, ship communications,and wireless networks for home, office and public facilities.

Industrial uses include medical imaging systems andprocess control systems for manufacturing.

Government systems account for many of the high-end applications such as phased-array military radar,communications countermeasure systems, global military

radio networks, unmanned aerial vehicles and intelligencegathering systems.

Because of the complexity of these market segments,wideband A/D converters have made significant advancesin recent years.

This is due partly to silicon process improvementsand also to many applications that require direct samplingof IF signals well above 100 MHz.

One of the most important advances is the sample-and-hold (or track-and-hold) circuitry at the front end.

Just as important, are new sample clock interfacesand drivers.

At these speeds, you need state-of-the-art flash andmultistage flash conversion techniques.

New techniques in digital error code correction andthermal compensation circuitry help eliminate errors inbit accuracy, linearity and gain.

Lastly, these new devices are more immune to powersupply and system noise.


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Monolithic A/Ds for Fs > 100 MHz, bitsMonolithic A/Ds for Fs > 100 MHz, bitsMonolithic A/Ds for Fs > 100 MHz, bitsMonolithic A/Ds for Fs > 100 MHz, bitsMonolithic A/Ds for Fs > 100 MHz, bits >>>>> 88888

Figure 27

Monolithic A/D ConverMonolithic A/D ConverMonolithic A/D ConverMonolithic A/D ConverMonolithic A/D Converterstersterstersters

ManufacturerManufacturerManufacturerManufacturerManufacturer PPPPPararararart Not Not Not Not No..... Sample FSample FSample FSample FSample Freq.req.req.req.req. ChannelsChannelsChannelsChannelsChannels BitsBitsBitsBitsBits Input BWInput BWInput BWInput BWInput BW

TI-National ADC12D1800 3,600 MHz 1 12 1,750 MHz

Linear Tech. LTC2380-16 2,000 MHz 1 16 34 MHz

e2v AT84AS008 2,000 MHz 1 10 3,000 MHz


Linear Tech. LTC2379-18 1,600 MHz 1 18 34 MHz

Maxim MAX108 1,500 MHz 1 8 2,200 MHz


e2v AT84AD001B 1,000 MHz 2 8 1,500 MHz

Maxim MAX101A 500 MHz 1 8 1,200 MHz

e2v AT84AD004 500 MHz 2 8 1,000 MHz

Texas Instr. ADS5463 500 MHz 1 12 750 MHz



Analog Dev. AD9480 250 MHz 1 8 400 MHz




Linear Tech. LTC2255 125 MHz 1 14 300 MHz

Shown in the table above are some representativeexamples of commercially available, monolithic A/Dconverters with sampling rates greater than 100 MHz andresolution of at least 8 bits.

All these devices are potential candidates for board-level products for embedded systems, such as those madeby Pentek.

Many of them are indeed used in current Pentekboard-level A/D converter and software radio products;some of them are also used in Pentek recording systems,

We have listed the input bandwidth in this table tohighlight the importance of these A/Ds in direct IFsampling applications, also known as undersampling.

In the next section, well discuss in some detail theprinciples and rules of sampling.



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Direct Baseband RF Signal AcquisitionDirect Baseband RF Signal AcquisitionDirect Baseband RF Signal AcquisitionDirect Baseband RF Signal AcquisitionDirect Baseband RF Signal Acquisition Analog RF FAnalog RF FAnalog RF FAnalog RF FAnalog RF Frequency Trequency Trequency Trequency Trequency Translationranslationranslationranslationranslation

Figure 28 Figure 29


Most receiver systems start with a signal originatingfrom an antenna thats often in the microvolt level, so itmust first be amplified by an RF amplifier stage.

The amplifier is usually a tuned RF circuit whichonly passes the frequency band of interest, providingsignal gain within that band and rejecting noise andunwanted signals in adjacent frequency bands.

If the RF input signal is at a low enough frequency,it can be digitized directly by an A/D converter, and noanalog translation is necessary.

For example, you can usually perform directbaseband sampling on HF signals with no translationrequired, since the frequency content is below 30 MHz.

In the case where the antenna signal frequency is toohigh to be digitized directly by the A/D converter, it hasto be translated down using an analog mixer and localoscillator.

The top diagram shows a simplified representationof this analog translation to baseband with a low passfilter following the mixer.

The bottom diagram shows the translation to anintermediate frequency or IF this is quite common.In this case, the filter is a bandpass filter centered at theIF frequency.

So far, weve discussed three types of front endcircuitry:

1) Direct sampling with no translation

2) Analog translation to baseband

3) Analog translation to IF

But how do we design the filters in each case?

Lets go back to review some fundamental samplingtheory.


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FFFFFiltering Helps Ailtering Helps Ailtering Helps Ailtering Helps Ailtering Helps Avoid Noise and Aliasingvoid Noise and Aliasingvoid Noise and Aliasingvoid Noise and Aliasingvoid Noise and Aliasing FFFFFananananan-f-f-f-f-fold Pold Pold Pold Pold Paper Model to Visualize Samplingaper Model to Visualize Samplingaper Model to Visualize Samplingaper Model to Visualize Samplingaper Model to Visualize Sampling

Figure 30 Figure 31


Filters ahead of the A/D are needed primarily fortwo reasons: to eliminate out-of-band noise and toeliminate out-of-band signals that can cause aliasing.

Nyquist tells us that whenever you sample a signalwith an A/D, the bandwidth of that signal must be lessthan half the sampling frequency of the A/D.

Filters help us guarantee that this rule is met.Sometimes the bandwidth is already limited by thesignal source, like the output of an IF stage that takesadvantage of the IF filter bandwidth. But each case hasto be analyzed individually.

The design of the filter is also critically linked to thesampling mode. Here weve listed three fundamentalsampling modes:

1) Basebandwidebandsampling

2) Baseband preselectsampling

3) Undersampling, which is also sometimes calledsubsampling

To help you get a feel for the filter requirements ofeach mode, we present a convenient tool for analyzingthe effects of sampling in the frequency domain.

This simple technique has been very useful to ourcustomers and our own applications engineers to helpthem understand what happens during sampling.

Imagine that we have a stack of the old fan-foldcomputer printer paper but with transparent sheets.

Now, we assign the frequency axis along the bottom

edge of this paper, scaled so that multiples of the sam-pling frequency line up with the backward folds of thepaper, as shown.

Using that frequency scale, we plot out the spectrum ofthe signal we want to sample with amplitude plotted onthe vertical axis.


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High-Speed A/D ConverHigh-Speed A/D ConverHigh-Speed A/D ConverHigh-Speed A/D ConverHigh-Speed A/D Converterstersterstersters

FFFFFan-fold Pan-fold Pan-fold Pan-fold Pan-fold Paper Model to Visualize Samplingaper Model to Visualize Samplingaper Model to Visualize Samplingaper Model to Visualize Samplingaper Model to Visualize Sampling Baseband Sampling of WBaseband Sampling of WBaseband Sampling of WBaseband Sampling of WBaseband Sampling of Wideband Signalsideband Signalsideband Signalsideband Signalsideband Signals

Figure 32 Figure 33

Now, lets collapse the stack of transparent paper flattogether and hold the stack up to a light so we can seethrough all the sheets.

We are now looking at the frequency plot of thesampled signal at the output of the A/D converter.

Notice that weve lost a lot of information becausewe cant tell which sheet a particular signal is on. And,unfortunately, after sampling that information is lostforever.

Weve also contaminated any particular signal withsignals from other sheets which have folded on top of it.

Not only that, weve also folded the noise from allthe sheets so they pile up in the region between DC andthe half sampling rate, potentially ruining the signal tonoise ratio.

How do we avoid this mess in each of the threesampling modes?

For the baseband wideband sampling mode, wherewe want to look at everything from DC up to a frequencybelow the half sampling rate, we can install a low passfilter with a cutoff frequency, Fc, located below Fs/2.

The frequency response of the filter is shown in green

Now, all of the out-of-band signals and noise on thepages above Fs/2 are eliminated so that when the foldingoccurs, it doesnt corrupt the baseband signal.


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Baseband Sampling of PBaseband Sampling of PBaseband Sampling of PBaseband Sampling of PBaseband Sampling of Preselect Signalsreselect Signalsreselect Signalsreselect Signalsreselect Signals PPPPPrinciples of Undersamplingrinciples of Undersamplingrinciples of Undersamplingrinciples of Undersamplingrinciples of Undersampling

Figure 34 Figure 35


For the baseband preselectsampling mode, we needto use a bandpass filter with the frequency responseshown in green.

We get the same benefits as the previous case forout-of-band signals and noise above Fs/2, but moreimportantly, we can keep large adjacent signals like theone shown, from getting to the A/D converter.

The reason for this is that if the large unwantedsignal gets through to the A/D converter, it uses up itsdynamic range.

For applications where there are known, strongunwanted signals, this technique can be extremely usefulin improving the signal-to-noise ratio of the smallersignal of interest.

The third sampling mode, called undersampling orsubsampling, is ideal for many systems that use ananalog RF translator front end. These receivers usuallydeliver IF outputs, often at 21.4 or 70 MHz, with

bandwidths ranging from a few kilohertz to tens ofMHzdepending on the receiver.

If we wanted to perform baseband sampling on a70 MHz signal, we would have to choose a samplingrate of well over 140 MHz. This may require an A/Dthat adds significant cost and power to the system.

However, because the IF signal is inherentlybandlimited, we can take advantage of the foldingcaused by sampling and use a lower frequency A/D.

This is a little tricky since you have to carefully

choose the sampling frequency and filtering according tothe signal frequency and bandwidth.

Lets see how.


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PPPPPrinciples of Undersampling Design: Step 1rinciples of Undersampling Design: Step 1rinciples of Undersampling Design: Step 1rinciples of Undersampling Design: Step 1rinciples of Undersampling Design: Step 1 PPPPPrinciples of Undersampling Design: Step 2rinciples of Undersampling Design: Step 2rinciples of Undersampling Design: Step 2rinciples of Undersampling Design: Step 2rinciples of Undersampling Design: Step 2

Figure 36 Figure 37

Here are some tradeoffs to consider:

With a higher sampling rate, the pages are wider andthe filter becomes less complex. Also, there is a lower noisedensity folded into the 0 to Fs/2 band after sampling.

At higher sampling rates, however, the A/D is moreexpensive and the number of bits of accuracy drops off.

You also need to be sure that the A/D has a goodwideband input stage to handle the IF signal withminimum distortion.

Equally important is the aperture uncertainty orphase jitter of the sample-and-hold amplifier, which isusually part of the A/D.

To make this job easier, many A/D converters are now

specifically characterized to operate in undersamplingapplications.

The fan-fold paper really comes in handy here.

First, design a bandpass filter that rejects unwantedsignals and noise.

This is often fully satisfied by the standard IF filterin the RF translator, but you do have to check this.

Sharper filters add cost and maintenance but theydo let you get away with a lower sampling rate as wellsee in the next figure.

Second (top of next column), choose a samplingfrequency so that the passband of the filter, along withits skirts, falls entirely on a single page of fan fold paper.

There are many possible solutions to each case, soyou have to pick the one that works best. You may have

to go back and forth a few times to readjust the filterand sampling rate to get the best scheme.


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Undersampling PUndersampling PUndersampling PUndersampling PUndersampling Perererererforms Fforms Fforms Fforms Fforms Frequency Trequency Trequency Trequency Trequency Translationranslationranslationranslationranslation Guidelines for Sampling and UndersamplingGuidelines for Sampling and UndersamplingGuidelines for Sampling and UndersamplingGuidelines for Sampling and UndersamplingGuidelines for Sampling and Undersampling

Figure 38 Figure 39

The effect of undersampling, as you probably expectedby now, is that the IF signal is folded down to the firstpage. This is really an automatic frequency translation,performed for free by the sampling process.

For the signals on every odd numbered sheet, the

effect is a frequency translation by a multiple of Fs. Forthe signals on even numbered sheets, there is a reversal ofthe frequency axis on that sheet, followed by a transl-ationby an odd multiple of Fs/2. Again, this is much easier tofollow by visualizing the fan-fold model.

This undersampling technique is extremely popularin software radio systems which almost always follow theA/D converter with a DDC (digital downconverter).

Regardless of where the undersampling foldingprocess translated the signal of interest, the DDC cantranslate it down to 0 Hz as a complex baseband signal.Once the complex signal is at baseband, the reversal ofthe frequency axis is easily undone by simply changingthe sign of the Q component.

There are usually several different sample clockfrequencies that will work for undersampling. While thefan-fold paper model can show all of the correct frequencyplans, the best choice will usually be determined by severalother important practical considerations shown above.

Some A/D converters are specifically characterizedfor undersampling applications, while others are designedonly for baseband sampling. Make sure to verify thespecifications.

Noise and distortion of the input signal must beminimized so these components dont fold into thesampled signal. Special care must be taken to preservethe purity of the sample clock signal.

Undersampling can be an extremely valuable toolfor software radio applications, since it can eliminate atleast one additional stage of analog frequency translationand simplify system design.

Undersampling allows you to use an A/D converterwith a lower sampling rate, which usually means morebits of resolution and better dynamic range. This lowersample rate also reduces the cost and complexity of thenext stage of digital signal processing, recording, storage,or transmission.


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Gigabit serial links send data over a pair of wires using differentialsignaling

Sequential 1s and 0s are sent over the pair of wires at a fixed bit rate

Popular serial rates: 10 MHz, 100 MHz, 1 GHz, 2.5 GHz, 3.125 GHz, etc.

The clock, data, and data word framing are encoded into the serial

bits stream, typically using 8B10B coding:

10 bits of serial transmission are required to deliver 8 bits of data

Extra 2 bits maintain synchronization, framing and DC line balance

SERDES - Serializer / Deserializer

Serializer: Encodes clock, frame, and 8 bits of data into a 10-bit stream

Deserializer: Decodes clock, frame and 8 bits of data from a 10-bit stream

Usually combined into one device for full duplex operation

serial linkSerializer

Parallel

local

data out

clock

serial pair xmit

8 bits

De-

serializer

Parallel

local

data in

clock

serial pair recv

8 bits

1010010010

10 bits

Too many different I/O technologies per system

FPDP, PCI, VME, Ethernet, RS-232, FibreChannel,

SCSI, PMC, IP, 1553, LVDS, ATM, etc.

Bus backplanes are major data bottlenecks

All boards must share a common bus, one at a time!

Parallel switched fabrics are expensive

RACEway was controlled by one vendor

Cabling increases system cost and complicates maintenance

Cables and connectors can be a major factor in MTBF

Software upgrades are difficult for specialized interfaces

Performance goals require software tuning of signal paths

Need a better solution for moving data !

Fast, flexible, open, and inexpensive

Appendix B: Switched Serial FAppendix B: Switched Serial FAppendix B: Switched Serial FAppendix B: Switched Serial FAppendix B: Switched Serial Fabricsabricsabricsabricsabrics

High-Speed Switched Serial InterHigh-Speed Switched Serial InterHigh-Speed Switched Serial InterHigh-Speed Switched Serial InterHigh-Speed Switched Serial InterfacefacefacefacefacesssssSwitched Serial Gigabit InterSwitched Serial Gigabit InterSwitched Serial Gigabit InterSwitched Serial Gigabit InterSwitched Serial Gigabit Interfaces - Why?faces - Why?faces - Why?faces - Why?faces - Why?

Figure 40 Figure 41

The VMEbus still serves as the dominant busstructure for high-performance real-time embedded systems.As requirements grew following its introduction,VME acquired new interfaces such as VSB, RACEway,RACE++, VME64 et al. that provided improved perfor-mance.

All these different I/O technologies caused new

problems with backplanes creating data bottlenecks andinterfaces controlled by one vendor. System costs increaseddue to cabling, maintenance and software upgrades. Abetter solution for moving data was needed and it had tobe fast, flexible, and inexpensive.

The answer turned out to be Switched Serial GigabitInterfaces.

A switched serial fabric system connects devicestogether to support multiple simultaneous data transfers,usually implemented with a crossbar switch. Usingdifferential signaling, data is sent over a pair of wiresat a fixed bit rate such as 100 MHz, 1 GHz, 2.5 GHz,3.125 GHz, etc.

The clock, data, and data word framing are encoded

into the serial stream, usually with 8B10B coding. Tenbits of serial transmission deliver eight bits of data. Theextra two bits maintain synchronization, framing andDC line balance.

The Serializer shown in Figure 17 encodes clock,frame, and eight bits of data into a 10-bit stream. TheDeserializer decodes the 10-bit st

high-speed, real-time recording systems, first edition

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