FMUWB a constantenvelope UWB communications system for shortrange
FM-UWB: a constant-envelope UWB communications system for short-range LDR applications John F. M. Gerrits 1, John R. Farserotu 1, Catherine Dehollain 2, Norbert Joehl 2, Michel Declercq 2. 1 Wireless Communications Section Centre Suisse d’Electronique et de Microtechnique S. A. 2 Electronics Laboratory (LEG), EPFL UWB 4 SN Workshop Lausanne 4 November 2005 J. Gerrits FM-UWB 1
Motivation for frequency domain approach for low complexity UWB Pulses that have been optimized for radar-like applications have not necessarily the best characteristics for a communiciations system. Realization of low power and fully integrated pulse generation circuits is not trivial. Since the definition of a UWB signal does not specify a particular air interface or modulation scheme, many different techniques may be applicable to a UWB signal. More established modulation schemes may/should be used to generate a UWB signal. J. Gerrits FM-UWB 2
Applications for LDR FM-UWB Short range (1 -10 m) wireless applications and services for monitoring and control: Home automation Security and alarms Health monitoring Sports training These require: Low cost, low power systems Portable (ideally go anywhere) Robust and reliable Good coexistence with other RF systems Fast access (short synchronization time) J. Gerrits FM-UWB 3
FM-UWB features True low complexity system compatible with IC technology Relaxed hardware specs (phase noise, component tolerances) No local oscillator No carrier synchronization CSMA/DAA techniques can enhance performance Antennas are not critical Steep spectral roll-off Robustness to interference and multipath Localization compatibility A 3 - 5 GHz COTS-based laboratory prototype exists in our labs Key building blocks already available in Si-Ge, down-scaled transmitter under integration in CMOS. J. Gerrits FM-UWB 4
FM-UWB principle A high modulation index FM signal modulated by a low-frequency signal (fm) may be seen as an analog spread spectrum system lowering the power spectral density of the transmitted signal. BRF = 2(Df + fm) This gives approximately N = 2 Df/fmod sidebands of almost equal strength in which no carrier can be distinguished. PSD is lowered by 10 log 10(Df/fm) = 28 d. B 600 MHz J. Gerrits 1 MHz FM-UWB 5
FM-UWB transmitter FSK J. Gerrits FM FM-UWB 6
FM-UWB Spectral properties Good co-existence Best use of spectral mask Dynamic interference mitigation J. Gerrits FM-UWB 7
FM-UWB receiver J. Gerrits FM-UWB 8
Wideband FM demodulator This demodulator has been fully integrated in Si-Ge Bi. CMOS. J. Gerrits FM-UWB 9
Measured results sensitivity: -46 d. Bm without LNA -68 d. Bm with 25 d. B LNA (5 m in office environment) J. Gerrits FM-UWB 10
FM-UWB access schemes A multi-user system may use: FDMA at RF carrier level FDMA at sub-carrier level (TDMA) J. Gerrits FM-UWB 11
FM sub-carrier techniques FM-UWB exploits sub-carrier FDMA techniques. Users have their individual subcarrier frequency and data rate if required. NMAX = 150 @ 1 kbps, NMAX = 15 @ 100 kbps J. Gerrits FM-UWB 12
Power Consumption Projections System Subsystem Blocks Transmitter Subcarrier oscillator DDS 6 DAC 3 Low pass filter 100 200 3. 5 m. W RF oscillator RF VCO (wideband) Output amplifier (wideband) LF ADC LF DAC 1500 <10 100 Receiver RF front-end LNA (wideband) Wideband FM demodulator Antenna switch 2000 3000 --- 7. 5 m. W Sub-carrier processing Sub-carrier quadr. LO Anti Aliasing Filter Mixers LPF Limiter amplifiers FSK demodulator 700 1000 200 50 10 Common 20 MHz Quartz oscillator. 1 J. Gerrits Current consumption [u. A] @ VDD = 1 V 80 FM-UWB 13
FM-UWB performance in AWGN Data rate R SNRRF PL d. FS [kbit/s] [d. B] [m] 1 -22 90 183 10 -17 85 106 100 -11 79 52 1000 -5 73 25 processing gain = BRF/BSUB 500 MHz / 2 R J. Gerrits FM-UWB 14
Receiver synchronization time Raw data right instantaneously, bitsynchronizer limited J. Gerrits FM-UWB 15
Robustness to MB-OFDM UWB signals SIR = -10 d. B BER < 1 x 10 -6 J. Gerrits c) FM-UWB 16
Which IC technology is required? Rx Tx A good CMOS or Bi. CMOS techno (f. T = 100 GHz), low VT and low VDD (1 V), on-chip passives with moderate Q factor. J. Gerrits FM-UWB 17
IC implementation of the FM-UWB Transmitter in 0. 18 um CMOS Technology Electronics Laboratory of EPFL Catherine Dehollain (Speaker) Norbert Joehl and Michel Declercq (catherine. dehollain@epfl. ch; Tel: 0041 (0) 21 693 69 71) J. Gerrits FM-UWB 18
Principle of the FM-UWB Transmitter FSK Modulation FM Modulation 1. 25 GHz FSK Modulation FM Modulation J. Gerrits FM-UWB 19
Specifications · Sub-carrier oscillator - · Frequency range: 0. 8 f – 1. 2 f with f = 100 k. Hz to 10 MHz. Waveform: triangular signal. External capacitor. VDD = 1. 5 V RF oscillator - Frequency range: from 0. 75 GHz to 1. 75 GHz. - VDD = 1. 5 V. J. Gerrits FM-UWB 20
Building blocks of the UWB Transmitter Ring Oscillator Relaxation Oscillator J. Gerrits FM-UWB 21
Sub-carrier signal at 80 - 120 k. Hz J. Gerrits FM-UWB 22
Sub-carrier signal at 8 – 12 MHz J. Gerrits FM-UWB 23
RF signal at 1. 25 GHz center frequency At the output of the integrated circuit J. Gerrits FM-UWB 24
Filtered RF signal at 1. 25 GHz center frequency Across the 50 Ohm radiation resistance of the antenna: 3. 5 m. W J. Gerrits FM-UWB 25
Current consumption of the building blocks Simulation results in UMC 0. 18 um CMOS with RF options • VDD = 1. 5 V. • Sub-carrier oscillator: 0. 2 m. A. • RF oscillator: 3 m. A. • Output buffer: 4 m. A. J. Gerrits FM-UWB 26
Layout of the FM-UWB Transmitter in UMC 0. 18 um CMOS GND RF-OUT GND VH Osc-en VL VDD Ibias Rv-moy Surface: 0. 7 mm X 0. 7 mm Isub J. Gerrits Vcycl FM-UWB Csub 27
Next steps UMC 0. 18 um CMOS Techno. • Manufacturing of the FM-UWB Transmitter. • Test of the FM-UWB Transmitter. 0. 13 um CMOS or 0. 35 um, 0. 25 um Bi. CMOS Si. Ge Techno. • Target: the UWB frequency band (3. 1 – 10 GHz) • Design of the new FM-UWB Transmitter using: - Digital sub-carrier generation - 3 -5 GHz and 6 -9 GHz RF oscillator and output stage J. Gerrits FM-UWB 28
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