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Radio Transceiver With High-Speed Serial Interface

Example System for Functional Test of Radio Transceiver

Transformation of Digital Technology

Fundamentals of High-Speed Serial

Options for Implementing High-Speed Serial in Functional Test Systems

Implementing 10 GbE in Your Test System

Changing Protocols and Settings in Vivado

Benefits of an NI Test System With High-Speed Serial Instruments

APPLICATION NOTE

High-Speed Serial Communication in Radio Transceiver Functional TestOverviewThis application note describes a reference design for implementing high-speed serial protocols like 10 Gigabit Ethernet, Xilinx Aurora, Serial RapidIO, or Common Public Radio Interface (CPRI) into functional test systems for radio transceivers and other similar RF systems (software-defined radio, signal intelligence [SIGINT], transmit and receive [TR] modules, remote radio heads, and radar systems). Learn how you can use NI high-speed serial instruments, LabVIEW software, and tools from Xilinx to implement numerous industry-standard and custom protocols in your test system.

CONTENTS

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Radio Transceiver With High-Speed Serial InterfaceThis paper shows the implementation of high-speed serial communication to test the functionality of a radio transceiver that uses an FPGA for IO and data processing. The system has inputs and outputs for DC power, RF transmit and receive signals, general-purpose input/output (GPIO), and a high-speed serial interface.

The power management segment supplies power for all other components of the system and regulates power usage. The Rx and Tx nodes receive and transmit modulated radio signals. There are two portions of digital data inputs and outputs on this module. The GPIO on this device is used for controlling the operating modes and reading registers from the radio transceiver system. An onboard processor is used to synthesize outgoing waveforms and perform signal processing on incoming waveforms.

This system can also be used to test remote radio heads, TR modules, SIGINT, and radar systems, which all include similar building blocks of radio transmission and reception as well as onboard signal processing.

Figure 1. A radio transceiver can be represented with a few simple components and is similar to other RF systems.

RADIO TRANSCEIVER

LO

GPIO

MultigigabitTransceivers

PowerManagement

ADC

DAC

FPGA

10 GbE

Tx

Rx

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Example System for Functional Test of Radio TransceiverA functional test system for this radio transceiver requires a number of measurement types and instruments. You can use this system for functional test of many radio systems from SIGINT transceivers to radio heads and TR modules.

Hardware

■■ PXI Express Chassis—PXIe-1085 Gen 3

■■ PXI Express Embedded Controller—PXIe-8880 with Xeon Processor

■■ High-Speed Serial Instrument—PXIe-6592R 10.3 Gbps with 4 Tx/Rx SFP+

■■ RF Signal Generator—PXIe-5654 with 250 kHz to 20 GHz generation range

■■ RF Signal Analyzer—PXIe-5668R with 20 Hz to 26.5 GHz acquisition range and 750 MHz of instantaneous analysis range

■■ Precision System Source Measure Unit (SMU)—PXIe-4139 with 20 Watt operating range and up to 500 Watt pulsing range

■■ Digital Instrument—PXIe-6556 with 200 MHz rate and PMU capability Software

Figure 2. A system advisor on ni.com can help you to configure and view your test system before purchase. This system contains all necessary instruments to test RF system functionality.

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High-Speed Serial Communication in Radio Transceiver Functional Test4

Software

■■ LabVIEW

■■ LabVIEW FPGA Module

■■ LabVIEW Instrument Design Libraries for High-Speed Serial Instruments

■■ NI DCPOWER instrument driver

■■ NI-HSDIO instrument driver

■■ NI-RFmx instrument driver

■■ TestStand

The high-speed serial instrument is used to stream data to and collect data from the DUT. Data sent to the transceiver includes signal data for pulsed and continuous waveforms. Acquired data contains radio signal information and is processed to determine that the assembly is working properly.

Read an introduction to NI’s high-speed serial instruments.

The RF signal generator is used to simulate incoming signal data that the radio transceiver interprets and processes, like detecting unexpected signal content. The RF signal analyzer is used to measure output transmission signals from the subsystem.

Learn more about NI’s RF instruments at ni.com/rf.

A system SMU provides input power to the system at all times and takes voltage and current measurements throughout the test to verify proper power consumption.

See why NI SMUs are the best for test on the market at ni.com/smu.

Figure 3. The major functions of a radio transceiver can be tested with a few fundamental instruments.

PXI TEST SYSTEM

Embedded Controller

RF Signal Analyzer

RF Signal Generator

High-Speed Serial

Instrument

DigitalInstrument

Source Measure

Unit

PXI CHASSIS

FPGA,DIO,

MGTs

PowerManagemet

RF In and Out

RADIO TRANCEIVER

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A digital instrument programs registers for preconfigured states and settings of the device and reads back values of those registers to confirm proper behavior of the device. The digital instrument could also be used to confirm the ability of the device to communicate in a range of clock rates and voltage settings and monitor power draw on the digital pins through its PMU capabilities.

See the breadth of NI’s digital instrument offering at ni.com/digital-instruments.

This paper outlines the proper steps to implement the high-speed serial link to the radio transceiver from the test system. To accomplish the functional test in its entirety, the high-speed serial instrument has to transmit and receive data from the radio transceiver across a 10 Gigabit Ethernet link.

Transformation of Digital TechnologyIn a world of “big data,” we have seen a drastic change of digital communication buses shifting from parallel to serial buses starting in the early 2000s. More and more devices with many points of I/O that include high-speed serial communication are entering the market every day and few vendors have the ability to integrate all of these test capabilities into a single system.

Serial buses overcome the line-rate and density constraints existing in parallel digital buses as they exceed 1 GHz line rates. The transition from parallel buses to high-speed serial buses has led to devices with much smaller footprints, much higher data throughput, and lower power requirements—enabling many of the technologies such as 10 GbE, Serial RapidIO (SRIO), JESD, or PCI Express that consumers take advantage of today.

TREND: PARALLEL TO SERIAL

Parallel Serial

SATAParallel IDE

JESD204Parallel Clock and Data

PCI EXPRESSPCI

1985 1990 1995 2000 2005 2010 2015

ADC and DAC Interfaces

Hard Drive Interfaces

Computer Buses

Figure 4. High-speed serial buses started to emerge when parallel data buses encountered speed limitations.

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Fundamentals of High-Speed SerialHigh-speed serial can best be described by the three fundamental layers that comprise the data interface: the physical layer, data link layer, and application layer.

Functional testing that includes the full high-speed serial link requires a higher level of sophistication than testing only the physical and data link layers. The ability to implement application-layer logic and standards on a test instrument is key to verifying the functionality at the highest level. The better the test equipment can emulate the real-world conditions of the system pieces, the more confident test engineers can be in the final product. The flexibility of user-programmable FPGA solutions gives the test solution the ability to be closer to the final deployed system solution. Learn more about high-speed serial communication.

Options for Implementing High-Speed Serial in Functional Test SystemsEngineers use two common methods to implement high-speed serial interfacing into a test system:

1. A commercial off-the-shelf (COTS) solution that uses industry-standard hardware and software tools in integrated hardware form factors

2. Stand-alone components or vendor-provided evaluation boards that can be used to design an instrument that meets the needs of the system

Figure 5. NI offers two models of high-speed serial instruments in the PXI platform. The PXIe-6592R high-speed serial Instrument uses four industry-standard SFP+ connectors with maximum 10.3125 Gbps line rates. The PXIe-6591R uses two Mini-SAS HD connectors capable of 12.5 Gbps line rates on 8 Channels (Tx/Rx).

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Some test engineers explore the possibility of making their own test equipment, and this is an option for high-speed serial interfacing. NI provides a COTS solution intended to provide a similar level of flexibility (through an open, user-programmable FPGA), without the need for a test engineer to start from scratch. After considering the work to lay out a printed circuit board (PCB) that includes an FPGA, maybe DRAM (and the memory interface logic to that DRAM), a PCI-Express interface to a host computer, and I/O connectivity, that is about 90 percent of the work compared to just bringing in IP for a serial protocol.

NI also accelerates development with LabVIEW FPGA, which greatly simplifies design challenges such as clock domain crossing, DRAM interfacing, and DMA transfers to computers. With the combination of a solid hardware starting point and accelerated software development, engineers can complete their designs faster and with a smaller team. In addition, NI has a large community of users, reference designs, and support networks to help engineers with any challenges they might run into along the way. Finally, the COTS provider can handle all the component life-cycle management to ensure the long-term ability to manufacture and globally distribute a standard product.

Implementing 10 GbE in Your Test SystemCommon in both defense and commercial technology, the 10 GbE high-speed serial protocol is capable of high-throughput data streaming and can be implemented using VHDL and Verilog IP cores for FPGAs.

NI provides a reference design for implementing 10 GbE that is installed with the LabVIEW Instrument Design Libraries for High Speed Serial Instruments. This driver provides additional functionality for LabVIEW and LabVIEW FPGA to interface with these high-speed serial instruments. Read about LabVIEW Instrument Design Libraries for High Speed Serial Instruments.

The reference designs for high-speed serial instruments that NI provides show the necessary steps to implement any industry-standard or custom protocol with existing Xilinx FPGA IP. The radio transceiver uses a 10 GbE data link so the high-speed serial instrument requires a 10 GbE implementation to communicate with the DUT.

Protocol Where to Access

Xilinx Aurora 64b/66b LabVIEW Instrument Design Libraries for High Speed Serial Instruments 14.0 or later

Xilinx Aurora 8b/10b NI Community

10 Gigabit Ethernet LabVIEW Instrument Design Libraries for High Speed Serial Instruments 15.5 or later

CPRI PXIe-6592R CPRI Bundle

Table 1. NI high-speed serial instruments support numerous industry-standard and custom protocols. Reference designs for protocols in this table are provided by NI on the instrument driver and at ni.com.

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Figure 6. NI high-speed instrument drivers install reference designs for 10 GbE and other protocols.

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This reference design comes ready to transmit and receive data bits over a preconfigured 10 GbE data link. 10 GbE is a well-defined and standardized protocol, but what if the module you were testing used a different protocol? Although 10 GbE is a common high-speed serial protocol used in radio systems, there are numerous other protocols, including Xilinx Aurora and SRIO, commonly used in these systems.

Aurora is a flexible protocol and can be easily modified because Xilinx has designed the IP core to be configurable for most settings of the multigigabit transceivers (MGTs) on Xilinx FPGAs. Aurora works with a wide variety of interfaces with different line rates or lane widths. Changes to these settings require design tools like Xilinx Vivado to configure the protocol IP core. Read more about making these customizations in Vivado in the following section.

The system or module often has additional, higher level application layers to correctly manage data transmitted and received by 10 GbE. Adding these layers is simplified using the existing LabVIEW and LabVIEW FPGA Module code in the reference design with some additional steps for data packetizing and depacketizing. Read more about implementing an application layer in the Implementing the Application Layer section.

Figure 7. The 10 GbE reference design includes all necessary VIs to start streaming data.

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Changing Protocols and Settings in VivadoTo interface with a DUT, the high-speed serial instrument’s interface has to match the one on the radio transceiver. Assume that a different radio head uses the Xilinx Aurora protocol. The Aurora reference design that is included in the LabVIEW Instruments Design Libraries for High Speed Serial Instruments has settings that might need to be altered to match the DUT’s interface. Changes to the protocol often have to be made in low-level VHDL design tools like Xilinx Vivado, which is included with the NI compilation tools for LabVIEW. Vivado can also be used to alter FPGA IP cores for industry-standard and custom protocols.

The Xilinx Vivado design tool for use with NI hardware can be downloaded on ni.com. Read this guide to download the correct version of these tools to work in your project.

With Vivado, you can create a new Aurora project that is built for the specific FPGA on the NI high-speed serial instrument or you can access prebuilt files from the Aurora LabVIEW sample project and make the necessary edits to the Aurora core. An experienced user could also start a project from Vivado and integrate the generated files into the high-speed serial instrument reference designs. Figure 8 shows the two different IP cores for Aurora: one that implements 64b/66b encoding, and another that uses 8b/10b encoding.

For more detailed information and instructions on using the Vivado tool with your LabVIEW FPGA project, see Generating and Integrating Aurora IP Into Your LabVIEW Project.

Figure 8. Vivado is a powerful tool for making FPGA designs and is installed with NI drivers.

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Implementing the Application LayerThe radio transceiver in this test uses the VITA 49 Radio Transport data framework as a main component of the application layer. VITA 49 is a common data standard used in radio systems and includes rules for packing data specific to radio systems. The standard defines separate data packets for signal data used for direction finding (DF), TDOA, beamforming, and other emitter localization techniques, as well as context packets to convey a comprehensive set of receiver attributes: frequency, bandwidth, gain, delays, sample rates, geo-location, and inertial navigation parameters. It also includes stream identifiers (SID) to associate packets from the same signal source and provide multiplexing capability across a link, as well as the method for associating signal data packets with context packets.

The VITA 49 packet format is added to the 10 GbE reference design using LabVIEW and LabVIEW FPGA. This requires LabVIEW FPGA logic that packetizes pulsed and waveform RF data being generated in the test system and streamed to the DUT. It must also include depacketizing information for translating data coming from the radio transceiver.

VITA 49 RADIO TRANSPORT (VRT) FRAMEWORK

Header (1 word, mandatory)

Stream Identifier (1 word, optional)

Class Identifier (2 words, optional)

Integer-Seconds Timestamp (1 word, optional)

Fractional-Seconds Timestamp (2 words, optional)

Data Payload (variable, mandatory)

Trailer (1 word, optional)

Figure 9. VITA 49 is a radio data standard that governs how important data is packetized.

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The radio transceiver under test can transmit and receive multiple channels of data. The test system has to be able to correctly bundle and debundle the data to effectively communicate with the radio transceiver. The first step for sending transmit data to the transceiver is splitting the interleaved signal data stream into manageable packets defined by the VITA 49 data standard. Each data packet then receives a header. Finally the data is managed based on the stream ID in the data packet and collated to form a full set of streaming channel data. Receiving data from the radio transceiver would be the reverse process of applying the same rules to get a full set of signal data.

Download an RF data channelizer reference architecture to get these VIs for packetizing and depacketizing VITA 49 data in LabVIEW FPGA on the NI Community.

Sample Test Program of RF SubsystemNow that the 10 GbE link is ready and the test system can packetize and depacketize VITA 49 data, you are ready to begin testing units. A simple example of testing the important functionality of a radio transceiver includes powering on the device, configuring the transceiver operating mode to accept digital data over the 10 GbE data link, streaming VITA 49 packetized signal data to the radio transceiver and transmitting that signal, measuring the known signal with an RF signal analyzer and performing channel power and frequency measurements, then moving on to the next functional test or powering off the transceiver if the full test sequence is complete. Throughout this test, instrumentation verifies the functional operation of all parts of the system.

TestStand is test executive software that provides a graphical test sequencing editor, test flow control, test parameters and limit checking, report and results logging and processing, resource scheduling, and user management. The sequence in Figure 11 shows more detail on each of the example test steps.

VITA 49 RADIO TRANSPORT (VRT) FRAMEWORK

Interleaved Data Packetizer Inject Header Data Modify Stream Identifier

Figure 10. Performing these three functions in LabVIEW FPGA packetizes data into a format the radio system can interpret.

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Each step in the sequence calls a code module that performs the actions and any data processing needed to obtain the test result. The test step to perform a signal measurement and analysis is a multipurpose measurement and analysis code module that collects channel data, processes the contents of the channel, and delivers the resultant data as well as a visual representation of the channel.

Figure 11. This is a simple test sequence that would be used to test the generation capability of a radio transceiver using a signal sweep with known output signal content as an example.

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This sample test sequence and code module are only a subset of the functionality of this radio transceiver. Functionality like signal acquisition and multiple operating frequency ranges would have to be tested to confirm proper working order of the system.

TestStand and LabVIEW are COTS, industry-standard tools for test management and instrument control that can test sophisticated systems and functionality. These software tools integrate seamlessly with test instruments, especially instruments on the PXI platform.

Benefits of an NI Test System With High-Speed Serial InstrumentsA platform-based test system that includes COTS software and hardware results in less time to develop a working system; long, vendor-supported lifetimes; extensible and reusable hardware with many vendor options; and tightly integrated measurement functions using internal device triggers and data streaming. With high-speed serial instruments in PXI, engineers can integrate all of the instruments needed to test a radio transceiver in a tightly synchronized hardware platform and a single test software framework that includes all of the data processing and instrument connectivity for a full functional test system.

Figure 12. The code module used to measure and analyze the signal collects data from the RF signal analyzer and then logs that data while also displaying results in real time.

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High-Speed Serial Communication in Radio Transceiver Functional Test

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Additional Resources■■ Get the channelizer reference design for 10 GbE streaming of VITA 49 packetized RF data

■■ Learn more about high-speed serial digital communication

■■ Read more about NI high-speed serial instruments

■■ Learn more about the open, modular instrumentation platform, PXI

■■ See the high-speed serial reference design for Aurora 8b/10b

■■ Download the LabVIEW Instrument Design Libraries for High Speed Serial Instruments to see the 10 Gigabit Ethernet reference design

■■ Explore the Advanced Architecture Series for TestStand best practices and advanced topics

Next Steps■■ Shop the PXI platform

■■ See options for NI high-speed serial instruments

■■ Try a free trial of LabVIEW or TestStand