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
Low Power RF Solutions - RF Basics
4-3
Module Topics
*** I hear it’s nice in Nice, this time of year ***
4-4
Low Power RF Solutions - RF Basics
Radio Types and 802.15.4
Radio Types and 802.15.4
2.4GHz Radio Types
CC2420
CC2520
CC243x
CC2480
Transceiver
DSSS (Direct Sequence Spread Spectrum)
802.15.4 compliant
TI-MAC, ZigBee, Z-Accel
AES-128 security
CC2400
CC2500
SoC
CC251x
Non-802.15.4 applications
SimpliciTI and other proprietary protocols
CC24xx – First generation
CC25xx – Second generation
(Improved link budget)
802.15.4 …
2
IEEE 802.15.4-2003
Worldwide 2.4GHz Channels
250 kbps
2.0 Mchip/s
2480 MHz -
2410 MHz -
2405 MHz -
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
O-QPSK
Half-sine pulse shaping
-85 dBm
DSSS …
3
Low Power RF Solutions - RF Basics
4-5
DSSS and RF Environment
DSSS and RF Environment
Spread Spectrum Implementation
DSSS (Direct Sequence Spread Spectrum)
Implemented in hardware
4 bits are coded into 32 chips
Correct chip sequence for nib b 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
Incom ing chip se que nce (va lue is 5, but w ith 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
Nib b le
value
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Comparison
1 1 0 1
1 1 1 0
0 0 1 0
0 0 1 0
0 1 0 1
0 0 1 1
1 1 0 0
1 0 0 1
1 0 0 0
1 0 1 1
0 1 1 1
0 1 1 1
0 0 0 0
0 1 1 0
1 0 0 1
1 1 0 0
(E XOR) with
1 0 0 1
1 1 0 1
1 1 1 0
0 0 1 0
0 0 1 0
0 1 0 1
0 0 1 1
1 1 0 0
1 1 0 0
1 0 0 0
1 0 1 1
0 1 1 1
0 1 1 1
0 0 0 0
0 1 1 0
1 0 0 1
all
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
possible
1 0 0
0 0 1
1 0 1
1 1 0
0 1 0
0 1 0
1 0 1
0 1 1
0 0 1
1 0 0
0 0 0
0 1 1
1 1 1
1 1 1
0 0 0
1 1 0
chi p sequences
0 0 1 1 0
1 1 0 0 0
1 0 0 1 1
1 1 0 1 1
1 1 1 0 1
0 0 1 0 1
0 0 1 0 0
0 1 0 1 0
0 1 1 0 0
1 0 0 1 0
1 1 0 0 1
1 0 0 0 1
1 0 1 1 1
0 1 1 1 1
0 1 1 1 0
0 0 0 0 0
1
0
1
0
1
1
0
0
0
1
0
1
0
0
1
1
0
1
0
0
0
1
1
1
0
1
0
0
0
1
1
1
1
1
0
1
1
0
0
0
0
0
1
0
0
1
1
1
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
0
1
0
1
1
0
1
0
1
0
1
0
0
1
1
0
1
0
0
0
1
1
1
0
1
0
0
0
1
1
0
1
1
0
1
1
0
0
1
0
0
1
0
0
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
0
1
0
1
1
1
1
0
1
0
1
0
0
1
1
0
1
0
0
0
1
1
1
0
1
0
0
0
1
0
0
1
1
0
1
1
0
1
1
0
0
1
0
0
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
0
1
0
1
0
1
1
0
1
0
1
0
1
1
1
0
1
0
0
0
1
1
1
0
1
0
0
0
0
0
0
1
1
0
1
1
1
1
1
0
0
1
0
0
Correlation
value
18
16
14
12
14
24
16
14
14
16
14
20
14
12
20
18
Environment …
4
Typical Office Radio Environment
EM Spectrum …
5
4-6
Low Power RF Solutions - RF Basics
EM Spectrum and ISM/SRD
EM Spectrum and ISM/SRD
Electromagnetic Spectrum
SOUND
RADIO
VHF = VERY HIGH FREQUENCY
UHF = ULTRA HIGH FREQUENCY
SHF = SUPER HIGH FREQUENCY
EHF = EXTREMELY HIGH FREQUENCY
LIGHT
HARMFUL RADIATION
2.4 GHz
ISM band
ISM bands
315-915 MHz
4G CELLULAR
56-100 GHz
UWB
3.1-10.6 GHz
ISM = Industrial, Scientific and Medical
UWB = Ultra Wide Band
Source: JSC.MIL
ISM/SRD …
6
Unlicensed ISM/SRD Bands
USA/Canada:
260 – 470 MHz
902 – 928 MHz
2400 – 2483.5 MHz
(FCC Part 15.231; 15.205)
(FCC Part 15.247; 15.249)
(FCC Part 15.247; 15.249)
Europe:
433.050 – 434.790 MHz
863.0 – 870.0 MHz
2400 – 2483.5 MHz
(ETSI EN 300 220)
(ETSI EN 300 220)
(ETSI EN 300 440 or ETSI EN 300 328)
Japan:
315 MHz
426-430, 449, 469 MHz
2400 – 2483.5 MHz
2471 – 2497 MHz
(Ultra low power applications)
(ARIB STD-T67)
(ARIB STD-T66)
(ARIB RCR STD-33)
ISM = Industrial, Scientific and Medical
SRD = Short Range Device
Output Power …
7
Low Power RF Solutions - RF Basics
4-7
Output Power
Output Power
2.4 GHz Output Power
EU
USA
10mW nominal
100mW for some applications
1mW nominal
1W for some applications
Additional regional restrictions must be met
Antennas …
8
4-8
Low Power RF Solutions - RF Basics
Output Power
Antennas
Commonly Used Antennas
PCB antennas
No extra cost
Large in size at low frequencies
Good performance possible
Complicated to make good designs
Whip antennas
Expensive
Good performance
Hard to fit in many applications
Chip antennas
Expensive
OK performance
PCB Antennas …
9
PCB Antennas
Antenna design is NOT easy
At 2.4 GHz: We have many reference designs
3rd party design houses can provide additional support
Folded Dipole
Compressed
Inverted-F
Chip antenna
Inverted-F
Pinyon Antennas …
10
Low Power RF Solutions - RF Basics
4-9
Output Power
Pinyon Antennas
Resonant slot technology
2x previous range at same power
Will be available on several TI reference designs
Gain Patterns
Azimuth
Elevation
3.8 x 1.5 x 0.062 inches
2.26× 1.0 5 × 0.062 inches
9 6 × 37.5 × 1.6 mm
5 7.4 × 26.7 × 1.6 mm
Pa rt No - AWP1SS24NBDHF V4A
Part No -AWP1SS24EHF V5
Full Size Single
Slot Antenna
Half Size Single
Slot Antenna
Interference and Fading …
11
4 - 10
Low Power RF Solutions - RF Basics
Interference and Fading
Interference and Fading
Interference and Fading
Interference
2.4 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
Solutions
DSSS
Coding gain from Forward Error Detection and Correction (FEDAC)
Increased sensitivity/resistance to narrow-band interference
Wider bandwidth required
Frequency hopping
Synchronization required
Could fit well with TI-MAC Beaconed network
Sleeping devices problematic
Frequency agility
Automatic or manual channel migration
Sleeping devices problematic
Antenna Diversity
An RF switch connected to two antennas spaced
½ wavelength apart
SmartRF Studio …
13
Low Power RF Solutions - RF Basics
4 - 11
SmartRF Studio
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 testing
Offers export/import of formatted register files, C-code snippet (chip register
structure/table)
14
SmartRF® Studio
Filemenu – register/code export/import.
Normal View – register calculator.
Status View – register monitor.
Normal View – physical units.
Normal View – predefined testing.
Lab Time ...
15
4 - 12
Low Power RF Solutions - RF Basics
Lab4 – SmartRF Studio
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 channel
Perform SmartRF Studio
TX/RX tests
Your instructor will assign
a channel to each group.
Write yours down.
Workgroup
1
2
3
4
5
6
7
Channel
12 (0x0C)
13 (0x0D)
14 (0x0E)
15 (0x0F)
16 (0x10)
17 (0x11)
18 (0x12)
Freq(MHz)
2410
2415
2420
2425
2430
2435
2440
16
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4 - 13
Lab4 – SmartRF Studio
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)
4 - 14
Low Power RF Solutions - RF Basics
Lab4 – SmartRF Studio
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:
Low Power RF Solutions - RF Basics
4 - 15
Lab4 – SmartRF Studio
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.
4 - 16
Low Power RF Solutions - RF Basics
Lab4 – SmartRF Studio
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.
Low Power RF Solutions - RF Basics
4 - 17
Lab4 – SmartRF Studio
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:
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Low Power RF Solutions - RF Basics
Lab4 – SmartRF Studio
10. Start the Test
In the right (RX) window, click the Start packet RX button, then in the left (TX) window, 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.
Low Power RF Solutions - RF Basics
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Lab4 – SmartRF Studio
12. Bag it
Let’s decrease the signal even more. Place a metalized anti-static bag over the TX antenna. 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 environment in which you are operating.
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Low Power RF Solutions - RF Basics
Lab4 – SmartRF Studio
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 environment 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)
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Lab4 – SmartRF Studio
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 Hardware 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.
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Low Power RF Solutions - RF Basics
Lab4 – SmartRF Studio
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 contains only the executable output of the PER project that I built earlier.
Click the Stop Debugging
Low Power RF Solutions - RF Basics
button.
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Lab4 – SmartRF Studio
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.
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Low Power RF Solutions - RF Basics
Lab4 – SmartRF Studio
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 enter 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 selection 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 selection 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 Button 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.
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Lab4 – SmartRF Studio
25. PER Test
The transmitter is now configured for the PER test. Start the test by moving the joystick 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 somewhere 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 determine 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 Examples Users Guide document. This document also describes how to download the application 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 everything aside for safe-keeping. We’ll use this hardware again later.
You’re done
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