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Low Power RF

Low Power RF. RF Basics and Getting Started. May 2012. everything. Wirelessly connecting everywhere. Abstract. This presentation serves as an overview of the parameters and considerations a designer would use to select a low-power wireless solution.

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Low Power RF

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  1. Low Power RF RF Basics and Getting Started May 2012 everything Wirelessly connecting everywhere.

  2. Abstract This presentation serves as an overview of the parameters and considerations a designer would use to select a low-power wireless solution. It also highlights the devices and tools from TI and how they fit in a typical design.

  3. Broad range of applications Consumer / personal networking Shipmentmonitoring Industrial remote monitoring • Information transmitted wirelessly is protected via encryption for more secure systems • Location, tamper detection and temperature monitoring • Low power sensor networks for innovative applications like remote monitoring for stress cracks • Harvest energy from motion, vibration and heat • Watch/shoe combination for monitoring of miles and calories • Enough processing for wireless networking and batteries that 10+ years 3

  4. TI’s portfolio: The industry’s broadest 13.4KHz /13.56MHz Sub 1GHz 2.4GHz to 5GHz Satellite Wi-Fi 802.11a/b/g/n Wi-Fi + Bluetooth® technology ZigBee® 6LoWPAN RF4CE RFID NFC ISO14443A/B ISO15693 SimpliciTI 6LoWPAN W-MBus SimpliciTI PurePath™ Wireless GPS Bluetooth® technology Bluetooth® low energy ANT™ Example applications Product line up TMS37157 TRF796x TRF7970 CC1101 CC1110 CC430 CC1190 CC11xL CC112x CC2500 CC2510 CC2590 /91 CC8520 /21 CC8530 /31 CC2560/7 CC2540 CC2570/1 CC2520 CC2530 CC2530ZNP CC2531 CC2533 WL1271/3 WL1281/3 WL1281/3 NL5500

  5. Definitions RF Systems Introduction to digital communication Radio Frequency: Spectrum Tools Agenda

  6. Basic system parameter definitions • RF power • RF power is typically measured in dBm (dB relative to 1mW) • Link budget • Difference between input sensitivity and output power in (dB) • PER • Packet Error Rate, % of packets not successfully received • Sensitivity • Lowest input power with acceptable link quality, typically 1% PER • Blocking/selectivity • How well a chip works in an environment with interference • Deviation/separation • Frequency offset between a logic ‘0’ and ‘1’ using FSK modulation

  7. Typical power levels • dBm– power referred to 1 mW, PdBm=10log(P/1mW) • 6dB increase in link budget => twice the range

  8. Sensitivity and Saturation Sensitivity CC1120 (868/915 MHz) Receiver Sensitivity The minimum signal power required by receiver to demodulate the received information with less than 1% bit error rate (BER) -103 dBm @200 kbps -110 dBm @50 kbps -114 dBm @4.8 kbps -123 dBm @1.2 kbps Saturation Highest input power level the receiver can demodulate correctly Data rate Minimum useable sensitivity (ETSI EN 300 V2.3.1 limit) 10log[RX BWkHz/16] – 107 dBm Dynamic Range = Saturation - Sensitivity

  9. Selectivity / Blocking Describes how well interfering signals are rejected For a receiver with very poor selectivity, frequency hopping will not help much, as even off-frequency interference is not attenuated sufficiently Jamming signal CC2500 performance: 31dB Jammer is 1259 times stronger than the wanted signal Selectivity Desired channel -89 dBm Simple FM, wide bandwidth: 0dB Frequency 31 dB ~ 36 times the distance Frequency offset (1 MHz)

  10. Definitions RF Systems Introduction to digital communication Radio Frequency: Spectrum Tools Agenda

  11. Typical Decision Parameters Highest Data Rate WLAN/UWB (Video) CC8520 wireless audio Bluetooth (Audio) Highest Battery Life CC430/SimpliciTI ZigBee/802.15.4 Bluetooth Low Energy ANT+ Longest Range CC112x based Sub1GHz solutions CC430/CC1101 based Sub1GHz solutions

  12. RF-IC Transmitter/Reciever Transceiver System-on-Chip (SoC); typicallytransceiver with integrated microcontroller Crystal Reference frequency for the LO and the carrier frequency Balun and Matching Balanced to unbalanced Impedance matching circuit Filter Used if needed to pass regulatory requirements / improve selectivity Antenna Basic Building Blocks

  13. Typical RF-IC block diagram 16 bit ULP MCU running from ROM =>new performance features: RX sniff mode, eWor Full digital signal processing =>stable performance over temperature, voltage and processvariation Ultra low phasenoise synth => Full RF regulatory compliance 90dB dynamic range ADC => Enables filtering of strong interferers with accurate digital filters

  14. Provides reference frequency for Local Oscillator (LO) and the carrier frequency Important characteristics: Price, often a price vs. performance trade-off Size Tolerance[ppm], both initial spread, ageing and over temperature Crystals

  15. Crystal Accuracy Compromise between RF performance and crystal cost Receiver channel filter BW Frequency offset -2·X ppm 0 +2·X ppm Total error of 4·X ppm Less expensive crystals can be used IF the system employs a frequency calibration / correction

  16. Balun and Matching circuit There are different balun implementations Trade-off: PCB area versus cost Microstripdelay line Discrete balun IC balun

  17. PCB antennas Little extra cost (PCB) Size demanding at low frequencies Good performance possible Complicated to make good designs Whip antennas Expensive (unless piece of wire) Good performance Hard to fit in may applications Chip antennas Expensive OK performance Small size Antennas, commonly used

  18. Definitions RF Systems Introduction to digital communication Radio Frequency: Spectrum Tools Agenda

  19. Wireless Communication Systems

  20. 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 signal • Three modulation schemes available: • Amplitude Modulation (AM): the amplitude of the carrier varies in accordance to the information signal • Frequency Modulation (FM): the frequency of the carrier varies in accordance to the information signal • Phase Modulation (PM): the phase of the carrier varies in accordance to the information signal

  21. Digital Modulation – ASK vcc • AM = analog message Vm(t) • ASK/OOK = digital message Vm(t) PA Vm(t) 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 spectrum noise at low to medium data rates. • This is called Shaped OO • Common Use: Many legacy wireless systems 0 0 1 1 ASK OOK • Signal Space Diagram • Each axis represents a ‘symbol’ • OOK has two symbols: carrier & no carrier • Distance between symbols predicts BER

  22. Amplitude Modulation (lab) AM– 50% in Time Domain AM– 50% in Frequency Domain • Amplitude Modulation • 915MHz, 10kHz modulation sine wave 22

  23. 250kbps OOK modulation 99% OCBW = 1754kHz 90% OCBW = 229kHz Average TX current = 50% ACI = ~50dBc (1MHz off) AM modulator (sim)

  24. Digital Modulation - FSK Voltage Controlled Oscillator PA Vm(t) • Frequency Shift Keying (FSK): • Pros: Less susceptible to noise • Cons: can take more bandwidth/bit than ASK • Popular in modern systems • Gaussian FSK (GFSK) has better spectral density than 2-FSK 0 1 • Signal Space Diagram / Signal Constellation • Each axis represents a ‘symbol’ • Each basis function is ‘orthogonal’ • Distance between symbols predicts BER

  25. Frequency Modulation (lab) FM – Time Domain Waveform FM – Freq Domain Waveform at m=2 FM – Freq Domain Waveform at m=10 FM – Freq Domain Waveform at m=0.2 • Frequency Modulation - 25

  26. 250kbps 2FSK modulation 99% OCBW = 508kHz 90% OCBW = 268kHz Average TX current = 100% ACI = ~57dBc (1MHz off) FM modulator

  27. 250kbps 4FSK modulation 99% OCBW = 321kHz 90% OCBW = 215kHz Average TX current = 100% ACI = ~55dBc (1MHz off) 4 level FM modulator

  28. Digital Modulation - nFSK FSK – Time Domain Waveform 4FSK 2FSK GFSK • Various types of Frequency Shift Keying modulation 28

  29. Digital Modulation – QPSK/OQPSK 01 10 11 00 • Quadrature Phase Shift Keying • Pros: Symbol represents two bits of data • Cons: Phase in the signal can jump as much as 180O causing out of band noise • Offset Quadrature Phase Shift Keying • Pros: Offsetting the signal limits the phase jump to no more than 90O • Example: IEEE 802.15.4 / ZigBee http://en.wikipedia.org/wiki/Phase-shift_keying

  30. 250kbps OQPSK modulation 99% OCBW = 4720kHz 90% OCBW = 3072kHz Average TX current = 100% ACI = ~30dBc (5MHz off) OQPSK modulator

  31. The modulation, bit rate, frequency deviation are exactly the same in simulation and on a CC1101 device 4FSK on the left (limited by modulation accuracy) 2FSK on the right (limited by noise floor in output) Comparison of Simulation to real data

  32. If we compare the 99% OCBW to the achieved bit rate you get a measure of spectral efficiency. Zigbee OQPSK is worst because it uses a spreading of 8 No surprising 4GFSK is best at almost “1” Summary of modulation analysis

  33. Demodulation Requirements • Signal Synchronization methods • Bit synchronization • Byte synchronization • Comparison of Signal to noise performance of different modulation methods.

  34. Bit synchronization (Preamble) • The Preamble is a pattern of repeated 1’s and 0’s, which is a representation of the modulation 4 bytes / 8 bytes • Which can be used by Receiver to pull Received Signal Strength Information (RSSI) • To trigger a Carrier Sense Flag • To qualify Sync Word to protect from false triggers • For data rates less than 500kb/s, a minimum 4 byte Preamble is recommended, at 500kb/s, a minimum 8 byte Preamble is recommended

  35. Byte synchronization (Sync Word) • Data is asynchronous, no clock signal is transmitted. • Clock is recovered (trained) with the Sync Word. Received Data Train 1 1 1 1 1 1 1 1 0 0 0 0 1 0 0 0 0 0 1 1 0 0 1 1 0 0 1 0 Expected Sync Word 1 clock 4 clocks 2 clocks 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

  36. WaveMatch; Advanced DSP Detector • There are numerous benefits to this technology • Ultra high sensitivity, down to -127dBm at 1.2kbps • Extremely quick settling: 0.5 byte preamble (only needed for gain settling – AGC) including AFC • Immune to noise, will not give false sync from noise • Can also be used as a highly reliable preamble detector WaveMatch detector • SYNC DETECTED • Bit Timing Found • Frequency Offset found • Data Demodulation Start We have designed the next generation radios where sensitivty and robustness is not limited by the sync detector! Using state-of-the-art digital signal processing we have designed a highly robust, extremely sensitive waveform detector; WaveMatch

  37. Compare sensitivity of 2FSK-4FSK “Waterflow graph” of a 2FSK and a 4FSK system Each “o” represent asystem simulation result 100000 symbols each Versus Eb/No (dB) Results are 2FSK is between 2-3dBbetter sensitivity than4FSK ~3dB ~2dB

  38. Definitions RF Systems Introduction to digital communication Radio Frequency: Spectrum Tools Agenda

  39. Regulations ISM/SRD Bands

  40. United States 315/915MHz 2.4 GHz Europe 433/868MHz 2.4 GHz Japan 426MHz 2.4 GHz Other National Requirements exist Regional Comparisons

  41. The 2400–2483.5 MHz band is available for license-free operation in most countries 2.4 GHz Pros Same solution for all markets without SW/HW alterations Large bandwidth (83.5MHz) available, allows many separate channels and high datarates 100% duty cycle is possible More compact antenna solution than below 1 GHz 2.4 GHz Cons Shorter range than a sub 1 GHz solution (same output power) Many possible interferers are present in the band The “World-Wide” 2.4 GHz ISM Band

  42. Unlicensed ISM/SRD bands: USA/Canada: 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) Europe: 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) Japan: 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) ISM = Industrial, Scientific and Medical SRD = Short Range Devices Frequency Spectrum Allocation

  43. Sub 1GHz ISM Bands • 902-928 MHz is the main frequency band • The 260-470 MHz range is also available, but with more limitations • The 902-928 MHz band is covered by FCC CFR 47, part 15 • Sharing of the bandwidth is done in the same way as for 2.4 GHz: • Higher output power is allowed if you spread your transmitted power and don’t occupy one channel all the timeFCC 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 up to 0.25 W • Direct Sequence Spread Spectrum (DSSS) and other digital modulation 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 mW output power

  44. Definitions RF Systems Introduction to digital communication Radio Frequency: Spectrum Tools Agenda

  45. Development kits TRXEB with: 2x CC110L EM 1x CC113L EM 1x CC115L EM • Value Line CC110LDK-868-915 development kit contains • 2x TRXEB (new transceiver evaluation board) • 2x CC110L EM • 1x CC113L EM • 1x CC115L EM • All EMs with PCB antennas • Cables and docs • Software needed for one way link & PER test • Easy RF development with SmartRF Studio • Value Line 433MHz CC110LEMK-433 kit contains • 2x CC110L EM-433 • 1x CC113L EM-433 • 1x CC115L EM-433 • Based on existing CC1101 ref design

  46. SmartRF Studio version 7 SmartRF Studio is a PC application to be used together with TI’s development kits for ALL CCxxxx RF-ICs. Converts user input to associated chip register values RF frequency, Data rate, Output power Allows remote control/configuration of the RF device when connected to the PC via a SmartRF Evaluation Board Supports quick and simple performance testing Packet RX/TX Packet Error Rate (PER)

  47. SmartRF Studio

  48. Getting Started with TI LPRFQuestions?

  49. Backup

  50. LPRF Value Line Tools Introduction • Booster pack EM for MSP430 launch pad • Pair of compact CC110L-868-915 transceiver modules with PCB antenna mounted on PCB board for easy connection to MSP Launchpad • Completely integrated module design • Including RF certification for quickest time to market • Module targeted to be used for development & volume production • Module developed & certified by 3rd party

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