Learning Objectives - Texas Instrumentsprocessors.wiki.ti.com/images/9/9e/04_-_RF_Basics.pdfRF Basics Introduction In this module, we’ll take a look at some basic RF issues that

RF Basics

Introduction In this module, we’ll take a look at some basic RF issues that you’ll need to deal with when designing a wireless project. We’ll also take a look at the differences between the CC24xx and CC25xx series radios. Finally we’ll run a quick lab using SmartRF Studio.

Learning Objectives • Radio types

• RF Environment

• Antennas

• SmartRF Studio

Low Power RF Solutions - RF Basics 4 - 1

Module Topics

*** oh yeah, 2.4GHz, baby! ***

4 - 2 Low Power RF Solutions - RF Basics

Module Topics

Module Topics RF Basics.................................................................................................................................................... 4-1

Module Topics......................................................................................................................................... 4-3 Radio Types and 802.15.4....................................................................................................................... 4-5 DSSS and RF Environment ..................................................................................................................... 4-6 EM Spectrum and ISM/SRD.................................................................................................................... 4-7 Output Power.......................................................................................................................................... 4-8 Antennas.................................................................................................................................................. 4-9 Interference and Fading.........................................................................................................................4-11 SmartRF Studio......................................................................................................................................4-12 Lab4 – SmartRF Studio..........................................................................................................................4-13

Description: .......................................................................................................................................4-13 Hardware list: ....................................................................................................................................4-14 Software list:......................................................................................................................................4-14 Procedure...........................................................................................................................................4-15


Module Topics

*** I hear it’s nice in Nice, this time of year ***


Radio Types and 802.15.4

Radio Types and 802.15.4 2.4GHz Radio Types

CC2420

CC2400

DSSS (Direct Sequence Spread Spectrum)802.15.4 compliantTI-MAC, ZigBee, Z-AccelAES-128 security

Non-802.15.4 applicationsSimpliciTI and other proprietary protocols

CC2520

CC2500CC251x

CC24xx – First generation CC25xx – Second generation

(Improved link budget)

CC243xCC2480

Transceiver

SoC

802.15.4 …2

IEEE 802.15.4-2003

11 17 18 19 20 21 22 23 24 25 2612 13 14 15 16

2405

MH

z -

2410

MH

z -

2480

MH

z -

Worldwide 2.4GHz Channels

250 kbps2.0 Mchip/sO-QPSKHalf-sine pulse shaping-85 dBm

DSSS …3


DSSS and RF Environment

DSSS and RF Environment Spread Spectrum Implementation

DSSS (Direct Sequence Spread Spectrum)Implemented in hardware4 bits are coded into 32 chips

Correct chip sequence for nibb le = 5:0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0

Incoming chip sequence (value is 5, but with 8 faulty chips):0 1 1 1 0 1 1 1 0 0 0 0 0 0 1 0 0 1 1 0 0 0 0 1 0 0 1 1 1 1 0 0

Nibble Correlationvalue Comparison (EXOR) with all possible chip sequences value

0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 181 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 162 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 143 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 124 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 0 1 1 145 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 246 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 167 1 0 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 148 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 149 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 16

10 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 1411 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 2012 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 0 1 1 0 1413 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 1 0 0 1 1214 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 1 1 0 0 2015 1 1 0 0 1 0 0 1 0 1 1 0 0 0 0 0 0 1 1 1 0 1 1 1 1 0 1 1 1 0 0 0 18

Environment …4

Typical Office Radio Environment

EM Spectrum …5


EM Spectrum and ISM/SRD

EM Spectrum and ISM/SRD Electromagnetic Spectrum

Source: JSC.MIL

SOUND LIGHTRADIO HARMFUL RADIATION

VHF = VERY HIGH FREQUENCYUHF = ULTRA HIGH FREQUENCYSHF = SUPER HIGH FREQUENCY EHF = EXTREMELY HIGH FREQUENCY

4G CELLULAR56-100 GHz

2.4 GHzISM band

ISM bands315-915 MHz

UWB3.1-10.6 GHz

ISMUWB

= Industrial, Scientific and Medical= Ultra Wide Band

ISM/SRD …6

Unlicensed ISM/SRD BandsUSA/Canada:

Europe:

Japan:

ISMSRD

260 – 470 MHz (FCC Part 15.231; 15.205)902 – 928 MHz (FCC Part 15.247; 15.249)2400 – 2483.5 MHz (FCC Part 15.247; 15.249)

433.050 – 434.790 MHz (ETSI EN 300 220)863.0 – 870.0 MHz (ETSI EN 300 220)2400 – 2483.5 MHz (ETSI EN 300 440 or ETSI EN 300 328)

315 MHz (Ultra low power applications)426-430, 449, 469 MHz (ARIB STD-T67)2400 – 2483.5 MHz (ARIB STD-T66)2471 – 2497 MHz (ARIB RCR STD-33)

= Industrial, Scientific and Medical= Short Range Device

Output Power …7


Output Power

Output Power

Additional regional restrictions must be met

2.4 GHz Output Power

10mW nominal100mW for some applicationsEU

USA1mW nominal1W for some applications

Antennas …8


Output Power

Antennas

PCB antennasNo extra costLarge in size at low frequenciesGood performance possibleComplicated to make good designs

Whip antennasExpensiveGood performanceHard to fit in many applications

Chip antennasExpensiveOK performance

Commonly Used Antennas

PCB Antennas …9

PCB Antennas

Chip antennaCompressedInverted-F

Antenna design is NOT easyAt 2.4 GHz: We have many reference designs3rd party design houses can provide additional support

Folded Dipole

Inverted-F

Pinyon Antennas …10


Output Power

Pinyon AntennasResonant slot technology2x previous range at same powerWill be available on several TI reference designs

Gain Patterns

Azimuth

Elevation

Half Size Single Slot Antenna

Full Size Single Slot Antenna

3.8 x 1.5 x 0.062 inches96 × 37.5 × 1.6 mm

Part No- AWP1SS24NBDHF V4A

2.26× 1.05 × 0.062 inches57.4 × 26.7 × 1.6 mm

Part No-AWP1SS24EHF V5

Interference and Fading …11


Interference and Fading



Interference2.4 GHz

WLAN, Bluetooth, analog video, microwave ovens, other ISM systems etc

Fading:Reflections from walls etc. signals can add in opposite phase (destructively) and cancel out at a point in space

Solution: Spread Spectrum

Solutions …12

DSSSCoding gain from Forward Error Detection and Correction (FEDAC)Increased sensitivity/resistance to narrow-band interferenceWider bandwidth required

Frequency hoppingSynchronization requiredCould fit well with TI-MAC Beaconed networkSleeping devices problematic

Frequency agilityAutomatic or manual channel migrationSleeping devices problematic

Antenna DiversityAn RF switch connected to two antennas spaced½ wavelength apart

Solutions

SmartRF Studio …13


SmartRF Studio

SmartRF Studio

Converts physical units, e.g. RF frequency, to associated chip register values.Allows remote control/configuration of the SmartRF® chip when connected to a DK.Supports quick and simple performance testingOffers export/import of formatted register files, C-code snippet (chip register structure/table)

SmartRF® Studio

14

Normal View – register calculator.

Filemenu – register/code export/import.

Normal View – predefined testing.

Normal View – physical units.

Status View – register monitor.

SmartRF® Studio

Lab Time ...15


Lab4 – SmartRF Studio


Description: Are you ready for some RF work? Let’s take SmartRF Studio for a spin and see what it can do.

Lab 4 – SmartRF Studio

Set your channelPerform SmartRF Studio TX/RX tests

Your instructor will assigna channel to each group. Write yours down. 244018 (0x12)7

243517 (0x11)6243016 (0x10)5242515 (0x0F)4242014 (0x0E)3241513 (0x0D)2241012 (0x0C)1

Freq(MHz)ChannelWorkgroup

16



Hardware list:

2 SmartRF05EB boards 2 CCMSP-EM430F2618 boards 2 CC2520EM boards 2 Antennas 3 USB A/B cables Metalized anti-static bag 4 AA Batteries MSP-FET430UIF and ribbon cable

Software list:

SmartRF Studio version 6.10.2 (You will find a shortcut for the above application on the desktop)



Procedure

Hardware

1. Disconnect the previous hardware If you haven’t dome so already, carefully disconnect the eZ430-RF2500 boards and USB extender cable and move them aside for safe-keeping. We’ll use them later.

2. Find the SmartRF04/CC2520EM boards Identify 2 SmartRF05EB boards. They look like this:

Identify 2 CC2520EM boards. They look like this:



3. Connect the Boards Carefully connect an EM board to each SmartRF05 board as shown below:

Then carefully connect the antennas. Do not over-tighten as it is possible to torque the connector right off the board!

4. Switch Positions Check the positions of the Power switch and Power Source jumper on the board. The switch is located below the bottom left of the LCD display. The switch should be in the OFF position (left) and the Power Source jumper should be on the rightmost two pins:

Just to the right of the Power Source jumpers is the EB Mode Selection switch. Make sure that it is in the JOYSTICK position (right), like the photo below:

5. Connect the USB Cables Using the two USB A/B cables, connect both boards to open ports on your PC.



6. Power up the Boards and Load Drivers Switch the Power switch on one of the boards to ON (right). The SmartRF05EB LCD should display “Texas Instruments SmartRF05 EB CC2520” and you should hear the Windows (ba-bump!) sound indicating that the board has been recognized. The Found New Hardware Wizard window should open on your desktop (unless your instructor arrived very early yesterday and did all this for you, which isn’t very likely). Select No, not this time and click Next. When the next window appears, select Install from a list or specific location and click Next. When the next window appears, check Search for the best driver in these locations, uncheck Search removable media …, check Include this location… and browse to C:\Program Files\Texas Instruments\Extras\Drivers. Then click Next. Finally, click Finish. Repeat this procedure for the other board.

7. Start SmartRF Studio Double-click on the desktop shortcut to start SmartRF Studio.

A window should open on your desktop much like the screenshot below:

Note that both boards have been recognized by SmartRF Studio. The USB device ID (USB DID) is the same as the serial number printed on the bottom of the SmartRF05EB. Using the Post-it™ notes, label each board on top with the last three digits of its serial number. Also label one TX and the other RX.



8. Start with the RX board In SmartRF Studio, select the board that you labeled RX and click Start. Select your workgroups’ channel number from the pull-down menu:

Then click on the Packet RX tab near the middle of the window:

Also, make sure the High Gain Mode checkbox (for the CC2591) is unchecked:

9. Now the TX board Resize the SmartRF Studio window so that you can see the window shown back in step 7. Select the TX board from the list, and click Start. Again, select your workgroups’ channel number from the pull-down menu, and then click on the Packet TX tab. Resize both TX and RX windows so that you can see them at the same time, like below, with the TX and the left and RX on the right:



10. Start the Test In the right (RX) window, click the Start packet RX button, then in the left (TX) win-dow, click the Start packet TX button. I got the following results with my boards about 1 meter apart:

11. Lower the TX Output Power

In the left (TX) window, change the RF output power to -18dBm. That’s as low as we can go:

and re-run the test as shown in the previous step. Here’s what I got:

At -54dBm, the PER was 7%. If all of your packets didn’t get through, click the Stop RX button.



12. Bag it Let’s decrease the signal even more. Place a metalized anti-static bag over the TX an-tenna. Don’t worry about shorting anything out with the bag; the resistance of the bag is very, very high. Repeat the test. Here’s what I got:

At -65dBm, my PER was 11%. Of course, this number depends greatly on the RF envi-ronment in which you are operating.



13. TX Test modes If you’re an RF geek, (of course, what would you be doing in THIS class? ☺), note the TX Test modes tab. With these test modes, you can observe the Unmodulated carrier and the Modulated spectrum on an attached spectrum analyzer. To do this test correctly, you’ll need to attach a very expensive analyzer to the BNC output of the CC2520EM board with a cable. I don’t have such an analyzer (or a cable, for that matter), so I used my Wi-Spy v1 2.4GHz Spectrum Analyzer (US$199) from metageek.net. My RF envi-ronment was pretty noisy at 2410MHz (which is probably why my packet error rates seemed high), so I moved the frequency up to a cleaner area at IEEE 802.15.4 channel 22 (0x16). Anyone care to guess at what frequency my Wi-Fi is set? RF Environment (no signal)

Unmodulated Carrier at 802.15.4 channel 22 (0x16)

Modulated Spectrum at 802.15.4 channel 22 (0x16)



14. Let’s Go Mobile The MSP430F2618 on the CCMSP-EM430F2618 is pre-programmed with the Packet Error Rate (PER) test. Let’s run that now. Disconnect the SmartRF05EB boards from the USB cables and carefully remove the CC2520EM boards from them (Don’t put any pressure on the antennas). Insert the CCMSP- EM430F2618 boards into the connectors on both SmartRF05EB boards, then connect the CC2520EM boards to the top of the CCMSP boards. Your two stacks should look like this:

Pre-programmed PER Test Did I say pre-programmed? The PER test is pre-programmed when you pull the board out of its’ anti-static bag for the first time. But there’s no telling what state the last person to use these boards left them in. We’ll have to re-load the PER test.

15. Connect the MSP-FET430UIF Emulator and Load Drivers

Using a USB A/B cable, plug the emulator into an open USB port. When the Found New Hard-ware wizard window appears, select No, not this time and click Next. When the next window appears, select Install the software automatically and click Next. If you are notified that the software has not passed logo testing, click Continue anyway. Then, click Finish. The Found New Hardware wizard window will appear again. Follow the same procedure.



16. Connect the Emulator and SmartRF05EB

Connect the ribbon cable from the MSP-FET430UIF to the emulator port of one of the CCMSP boards as shown below. Connect the SmartRF05EB to a USB port and make sure the power switch is on.

17. IAR Embedded Workbench Start IAR Embedded Workbench and click Open existing workspace. Navigate to: C:\Texas Instruments\SimpliciTI-1.0.6\Projects\Examples\Peer applications\ eZ430RF\Lab4 , select PER_test.eww and then click Open.

Click the Debug button. The program will be quickly downloaded to the board. I set this project up as an Externally Built project so that you wouldn’t have to fool with settings, options, paths, etc in order to reprogram the board. Basically, the project con-tains only the executable output of the PER project that I built earlier. Click the Stop Debugging button.



18. Second Board Move the USB cable and Emulator over to the second board. Make sure the power switch on the SmartRF05EB board is on and click the Debug button in IAR Embedded Workbench. When the download is complete, click the Stop Debugging button. Remove the USB cable and Emulator from the SmartRF05EB board. Close IAR Embedded Workbench.

19. Battery Power

On both boards, make sure that your power switchs are OFF, and move the Power jumper to the leftmost two pins, unlike what’s shown below:

Insert two AA batteries into the holder on the bottom of the SmartRF05 board. Be sure to observe proper polarity. We could have powered the boards via the USB port, but we want to be mobile.



20. Switch on Power on both boards and the PER test should start. The LCD will display the screen shown below. Press Button 1 (bottom right of the SmartRF05 board) to en-ter the menu on both boards.

21. Set your Channel

Select your workgroups’ channel on both boards by moving the joystick left or right. Confirm your selec-tion by pressing Button 1. If you make a mistake at any point, you can start over by pressing the EM RESET button.

22. Select Transmitter/Receiver

Select one board to be the Receiver and the other to be the Transmitter with the joystick. Confirm your selec-tion with Button 1. The Receiver is now ready to receive packets.

23. Select Output Power On the Transmitter, select 0dBm as your output power and confirm with Butt

on 1.

24. Burst Size

Set the burst size (the # of packets to transmit) to 1000 and confirm with Button 1. Your choices are 1000, 10,000, 100,000 and 1,000,000.



25. PER Test The transmitter is now configured for the PER test. Start the test by moving the joy-stick up. You can stop it by moving the joystick down. The test will display the total PER and the moving average RSSI on the display. It will also display the number of packets received during the PER test. With the boards sitting on the same table, you should get 0 for the PER, an RSSI some-where in the 20’s and 1000 packets received. If your results are wildly different, start over and re-check your channel settings. If you still get odd results; notify your instructor.

26. Mobile

Follow the earlier procedure to set up the PER test, but this time pick 1,000,000 for the burst size, That will give you enough time to wander around with the receiver and de-termine the limits of this RF setup. Do that now. When the RSSI gets down to -80dBM or so, you should start picking up a lot more errors. Remember that the PER is x/1000, not x/1,000,000 , and is a percentage, not the actual number of errors (unless the burst size is 1000)

27. Shut Down

The PER test and other software examples are documented in the CC2520 Software Ex-amples Users Guide document. This document also describes how to download the appli-cation to the MSP430 microcontroller on the CCMSP-EM430F2618. Shut down all the SmartRF Studio windows on your desktop, power off the SmartRF05EB boards, remove the batteries, disconnect the USB cables and put every-thing aside for safe-keeping. We’ll use this hardware again later.

You’re done


Documents

Learning Objectives - Texas Instrumentsprocessors.wiki.ti.com/images/9/9e/04_-_RF_Basics.pdfRF Basics Introduction In this module, we’ll take a look at some basic RF issues that