rf basics and getting started

7/29/2019 RF Basics and Getting Started

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RF basics & getting started

www.anaren.com/AIR

[email protected]

c nowe gemen : os o e n orma on n s presen a on s prov e

courtesy of Texas Instruments, and is intended for general educational purposes.
http://www.anaren.com/AIRmailto:[email protected]:[email protected]://www.anaren.com/AIR


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Abstract

This presentation serves as an overview of

the parameters and considerations a

designer would use to select a low-power

wireless (LPRF) solution.

It also highlights the devices and tools from

the Anaren Integrated Radio (AIR) module

product line and how they fit in a typical LPW

design.


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RF definitions

Radio modulation schemes

Radio frequency spectrum

Stack considerations

Network types

Development tools and EVMs

Outline


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RF definitions


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RF power definitions

dBm power referred to

1 mW

PdBm=10log(P/1mW)

0dBm = 1mW

20 dBm = 100mW

30 dBm = 1W

Example:

-110dBm = 1E-11mW = 0.00001nW

Power = V*V / R:

50 W load : -110dBm is 0.7uV

Rule of thumb:6dB increase => twice the range

3dB increase => roughly doubles the

dbm power

= dBm


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dBm to Watt

About dBm and W

Voltage Ratio aV = 20 log (P2/P1) [aV] = dB

Power Ratio aP = 10 log (P2/P1) [aP] = dB

Voltage Level V = 20 log (V/1V) [V] = dBV

Power Level P = 10 log (P/1mW) [P] = dBm

Example: 25mW is the maximum allowed radiated (transmitted)

power in the EU SRD band

P = 10 log (25mW/1mW) = 10 * 1.39794 dBm ~ 14 dBm


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dBm Typical Values


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Radio performance definitions

Packet Error Rate (PER)The percentage (%) of packets not received successfully (This

includes packets lost and packets received with a CRC error).

SensitivityLowest input power with acceptable link quality (typically

1% PER)

Deviation/SeparationFrequency offset between a logic 0 and 1 using FSK

modulation scheme

Blocking/selectivityHow well a chip works in an environment with interference on

the same channel/Frequency.


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Radio modulation schemes


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Wireless communication systems

Low Frequency

Information Signal(Intelligence)

High Frequency

Carrier

Modulator Amplifier

Transmitter

Communication

Channel

AmplifierDemodulator

(detector)

Output

transducer

Receiver

Amplifier


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Modulation methods

Starting point: We have a low frequency signal and want to

send it at a high frequency

Modulation: The process of superimposing a low

frequency signal onto a high frequency carrier signal

Three modulation schemes available:

1. Amplitude Modulation (AM): The amplitude of the carrier varies in

accordance to the information signal

2. Frequency Modulation (FM): The frequency of the carrier varies inaccordance to the information signal

3. Phase Modulation (PM): The phase of the carrier varies in

accordance to the information signal


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Digital Modulation ASK

The modulation of digital signals is known as Shift Keying

Amplitude Shift Keying (ASK/OOK): Pros: Simple, duty cycling (FCC), lower transmit current Cons: susceptible to noise, wide spectrum noise

Rise and fall rates of the carrier's amplitude can be adjusted to reduce the spectrumnoise at low to medium data rates. This is called Shaped OOK

Common Use: Many legacy wireless systems

Signal Space Diagram

Each axis represents a symbol

OOK has two basis functions: sinusoid &

no sinusoid

OOK has two symbols: carrier & no carrier

Distance between symbols predicts BER

10

carrier

digital

data

OOK

modulation

OOK

10

ASK10 10 10 10 10


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Digital Modulation - FSK

Frequency Shift Keying (FSK): Pros: Less susceptible to noise

Cons: Theoretically requires largerbandwidth/bit than ASK

Popular in modern systems

Gaussian FSK (GFSK) has better spectraldensity than 2-FSK modulation, i.e.more bandwidth efficient FSK modulation

FrequencyfcFc-df Fc+df

DIO=low DIO=high

Frequency deviation

Frequency separation

= 2 x df

1

0

Signal Space Diagram / Signal

Constel lat ion


Each basis function is orthogonal


freq1

carrier

digita

l

data

FSK

mod

freq2

carrier


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Digital modulation - PSK

Phase Shift Keying (PSK):

Pros:

Less susceptible to noise Bandwidth efficient

Cons: Require synchronization in frequency and phasecomplicates receivers and transmitter

10


Constel lat ion




freq

1

carrier

d

igital

data

PSK

mod

freq2

carrier


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Digital modulation - MSK

Minimum Shift Keying (MSK):

Pros: Difference in Frequency is Half the bit rate

Very bandwidth efficient

Reduced Spectrum noise

Cons: Require synchronization in frequency and phase

complicates receivers and transmitter

10


Constel lat ion




freq1

carrie

r

digital

d

ata

MSK

mod

freq2

carrier


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Digital modulation QPSK/OQPSK

Quadrature Phase Shift Keying: Pros: Symbol represents two bits

of data Cons: Phase in the signal can jump

as much as 180O causing out ofband noise

Offset Quadrature Phase Shift Keying:

Pros: Offsetting the signal limitsthe phase jump to no more than90O

Example: IEEE 802.15.4 / ZigBee

http://en.wikipedia.org/wiki/Phase-shift_keying

2

CA

1

2

2

CA

11

10

00

01

Continues, next slide >>>


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Digital modulation QPSK/OQPSK

http://en.wikipedia.org/wiki/Phase-shift_keying


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Preamble

The Preamble is a pattern of repeated 1s and 0s

4 bytes / 8 bytes

Which can be used by Receiver to pull Received Signal

Strength Information (RSSI)

to trigger a Carrier Sense (CS) Flag

to qualify Sync Word to protect from false triggers

An extended preamble can be sent by sending an STX strobe

with no data in the TX Buffer (or by not triggering the DMA inthe RF SoCs)

For data rates less than 500kb/s, a 4 byte Preamble is

recommended, at 500kb/s, 8 bytes is recommended


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Clock and data recovery

Data is asynchronous, no clock signal is transmitted

Clock is recovered (trained) with the Sync WordReceived Data Train

1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 0 0 1 1 0 0 1 0 1 0

Expected Sync Word

4 clocks 2 clocks 1 clock

Recovered Clock Bit Time

Sync Word is 2 Bytes Programmable & can be repeated

default 0xD391: 1101001110010001

An 8 bit Sync Word can be accomplished by Extending the Preamble

with the Sync MSB


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Radio Frequency Spectrum


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Electromagnetic spectrum

Source: JSC.MI

SOUND LIGHTRADIO HARMFUL RADIATION

VHF = VERY HIGH FREQUENCY

UHF = ULTRA HIGH FREQUENCY

SHF = SUPER HIGH FREQUENCY

EHF = EXTRA HIGH FREQUENCY

4G CELLULAR

56-100 GHz

2.4 GHz

ISM band

ISM bands

315-915 MHzUWB

3.1-10.6 GHz
http://www.ntia.doc.gov/osmhome/allochrt.htmlhttp://www.ntia.doc.gov/osmhome/allochrt.html


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United States / Canada

315/433/915 MHz

2.4 GHz

European Union

433/868MHz 2.4 GHz

Japan

426MHz

2.4 GHz (Some restrictions)Other national requirements exist

Regional comparisons


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2.4 GHz ISM-band devices

Source: Eliezer & Michael, TI

Due to the world-wide availability of the 2.4GHz ISM band it

is getting more crowded day by day Devices such as Wi-Fi, Bluetooth, ZigBee, cordless

phones, microwave ovens, wireless game pads, toys, PC

peripherals, wireless audio devices occupy the 2.4 GHz

frequency band

Power

Microwave

oven

Cordless Frequency802.11b/g


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Bl h 802 11


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Bluetoothversus 802.11


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The ISM bands under 1 GHz are not world-wide

Limitations vary a lot from region to region andgetting a full overview is not an easy task

Sub 1GHz Pros

Better range than 2.4 GHz with the same output powerand current consumption (assuming a good antennanot easy for a limited space)

Sub 1GHz Cons Since different bands are used in different markets it is

necessary with custom solutions for each market

More limitations to output power, data rate, bandwidthetc. than the 2.4 GHz

Duty cycle restrictions in some regions

Interferers are present in most bands

Sub-1GHz ISM bands

S b 1GH ISM b d i USA


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Sub-1GHz ISM bands in USA

902-928 MHzis the main frequency band

The 260-470 MHz range is also available, but with morelimitations on output power / duty cycling.

The 902-928 MHz band is covered by FCC CFR 47, part 15

Sharing bandwidth is done in the same way as for 2.4GHz:

Higher output power is allowed if you spread your transmittedpower and dont occupy one channel all the time FCC CFR 47

part 15.247 covers wideband modulation Frequency Hopping Spread Spectrum (FHSS) with 50

channels are allowed up to 1 W, FHSS with 25-49 channels upto 0.25 W

Direct Sequence Spread Spectrum (DSSS) and other digitalmodulation formats with bandwidth above 500 kHz are allowed

up to 1W FCC CFR 47 part 15.249

Single channel systems can only transmit with ~0.75 mWoutput power


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Sh t i l i


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Short-range wireless comparison

Different Value Drivers fo r Different Applicat io ns

1000m

Headsets

PC Peripherals

PDA/Phone

Building Automation

Residential Control

Industrial

Tracking Sensors

Home Automation / Security

Meter Reading

Data Rate

(bps)100k 1M 10M10k1k

Range

100m

10m

1m

ZigBee/802.15.4

PC Networking

Home Networking

Video Distribution

Wi-Fi/802.11

Proprietary Low Power Radio

Gaming

PC Peripherals

Audio

Meter Reading

Building Mgmt.

Automotive


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Network types


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Network types: mesh


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Network types: mesh

= end device

= router

= coordinator

Re-Connect

= data path

Mihir: Will need to clean this one

(re: symbol key)

L i l t k


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Low-power wireless networks

Point to Point

Proprietary or

IEEE 802.15.4

PHY + MAC

Star Network

Proprietary or

IEEE 802.15.4

PHY+ MAC

Multihop Mesh and cluster

tree Networks

ZigBee or based on ZigBee

technology


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M h t k


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Mesh network

Pros

self healing easily extendable throughmultiple hops

end devices can be batteryoperated

easy to deploy

can be ZigBee compliant

Cons router nodes needs to be

mains powered

Example lighting applications

building automation

ZigBee Coordinator

ZigBee Router

ZigBee End Device


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SimpliciTI is all about


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Low Power: a TI proprietarylow-power RF network protocol

Low Cost: uses


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Some available Low-power RF tools

Software Stacks


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Software Stacks

Z-Stack - ZigBee Protocol Stack from TI One of the first ZigBee stacks to be certified for the ZigBee 2006 certification

Supports multiple platforms such as CC2480, CC2431 and CC2520+MSP430

platform

ZigBee 2007/PRO available on CC2530 and MSP430 platform

TIMAC A standardized wireless protocol for battery-powered and/or mains powered

nodes

Suitable for applications with low data-rate requirements Support for IEEE 802.15.4-2003/2006

SimpliciTI Network Protocol RF Made Easy A simple low-power RF network protocol aimed at small RF networks

Typical for networks with battery operated devices that require long battery life,

low data rate and low duty cycle

RemoTI Remote control Compliant with RF4CE V1.0

Built on mature 802.15.4 MAC and PHY technology

Easy to use SW, development kits and tools
http://www.ti.com/z-stackhttp://www.ti.com/timachttp://www.ti.com/simplicitihttp://www.ti.com/rf4cehttp://www.ti.com/rf4cehttp://www.ti.com/simplicitihttp://www.ti.com/timachttp://www.ti.com/z-stackhttp://www.ti.com/z-stackhttp://www.ti.com/z-stack


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Mini-development kits


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Mini-development kits

Inexpensive, flexible development platform

for TI's CC2510Fx RF SoC solution:

CC2510Fx- 26MHz single-cycle 8051 CC2500

RF transceiver

- FLASH, RAM, 5 DMA channels, ADC,

PWM, UART, SPI, I2S, 4 timers, and 21

GPIO pins

The target board in this kit is very close to areal product and features:

- PCB antenna pre-tested for ETSI and

FCC compliance

- battery holders for 2x AAA or 1x CR2032

coin-cell operation

- footprint for 2.54 mm connector to

CC2510Fx GPIO pins

- 2 buttons & 2 LEDs for simple applicationdevelopment

- pre-programmed with Link Test for RF

range measurement


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SmartRF Studio


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S a t Stud o

SmartRF Studio is a PC application to be used togetherwith TIs development kits forALL CCxxxx RF-ICs.

Converts user input to associated chip register values RF frequency

Data rate

Output power

Allows remote control/configuration of the RF devicewhen connected to the PC via a SmartRF EvaluationBoard

Supports quick and simple performance testing Simple RX/TX

Packet RX/TX

Packet Error Rate (PER)


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Packet Sniffer


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Packet Sniffer

Captures and parses packets going over the air

Useful debugging tool for any protocol/SW designer PC Tool available for FREE

Supported protocols

SimpliciTI RemoTI (RF4CE)

ZigBee

Generic protocol

Hardware required for packet sniffing CC2430DB

SmartRF04EB + CC1110/CC2510/CC2430

SmartRF05EB + CC2520/CC2530

Packet Sniffer


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Packet Sniffer


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Getting started with AIR / Questions?Email us at [email protected]

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