j. gerrits fm-uwb slide 1 john f.m. gerrits 1, john r. farserotu 1, catherine dehollain 2, norbert...

J. Gerrits FM-UWB Slide 1

John F.M. Gerrits1, John R. Farserotu1, Catherine Dehollain2, Norbert Joehl2, Michel Declercq2.

1Wireless Communications SectionCentre Suisse d’Electronique et de Microtechnique S.A.

2Electronics Laboratory (LEG), EPFL

UWB4SN WorkshopLausanne

4 November 2005

FM-UWB: a constant-envelope UWB communications system for short-range LDR applications


Motivation for frequency domain approach for low complexity UWB

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.

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.

More established modulation schemes may/should be used to generate a UWB signal.


Short range (1-10m) wireless applications and services for monitoring and control:

Home automationSecurity and alarmsHealth monitoringSports training

These require:

Low cost, low power systemsPortable (ideally go anywhere)Robust and reliableGood coexistence with other RF systemsFast access (short synchronization time)

Applications for LDR FM-UWB


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.


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(f + fm)

This gives approximately N = 2 f/fmod sidebands of almost equal strength in which no carrier can be distinguished.

PSD is lowered by 10 log10(f/fm) = 28 dB

600 MHz 1 MHz


FM-UWB transmitter

FSK FM

)ff(f)(B mmRF 212


FM-UWB Spectral properties

Good co-existence Best use of spectral mask Dynamic interference mitigation


FM-UWB receiver


Wideband FM demodulator

This demodulator has been fully integrated in Si-Ge BiCMOS.

C

21

FMDEMOD f

f

2Ncos

2

AfV


Measured results

sensitivity: -46 dBm without LNA -68 dBm with 25 dB LNA(5 m in office environment)


FM-UWB access schemes

A multi-user system may use: FDMA at RF carrier level FDMA at sub-carrier level (TDMA)


FM sub-carrier techniques

FM-UWB exploits sub-carrier FDMA techniques.Users have their individual subcarrier frequencyand data rate if required.NMAX = 150 @ 1 kbps, NMAX = 15 @ 100 kbps


Power Consumption Projections

System Subsystem Blocks Current consumption [uA]

@ VDD = 1 V

Transmitter Subcarrier oscillator

DDS6

DAC3

Low pass filter

100100200

RF oscillator RF VCO (wideband)Output amplifier (wideband)LF ADCLF DAC

15001500<10100

Receiver Receiver RF front-end

LNA (wideband)Wideband FM demodulatorAntenna switch

20003000---

Sub-carrier processing

Sub-carrier quadr. LO Anti Aliasing FilterMixersLPFLimiter amplifiersFSK demodulator

70010002005005010

Common 20 MHz Quartz osc.

Quartz oscillator.1 80

3.5 mW

7.5 mW


FM-UWB performance in AWGN

Data rate R

[kbit/s]

SNRRF

[dB]

PL

[dB]

dFS

[m]

1 -22 90 183

10 -17 85 106

100 -11 79 52

1000 -5 73 25

processing gain = BRF/BSUB

500 MHz / 2R


Receiver synchronization time

Raw data right instantaneously, bitsynchronizer limited


Robustness to MB-OFDM UWB signals

c)

SIR = -10 dB

BER < 1x10-6


Which IC technology is required?

A good CMOS or BiCMOS techno (fT = 100 GHz),

low VT and low VDD (1 V),

on-chip passives with moderate Q factor.

Tx Rx


IC implementation of the FM-UWB Transmitter in 0.18um CMOS Technology

Electronics Laboratory of EPFL

Catherine Dehollain (Speaker)Norbert Joehl and Michel Declercq

([email protected]; Tel: 0041 (0) 21 693 69 71)

mailto:[email protected]


Principle of the FM-UWB Transmitter

1.25 GHz

FSK Modulation FM Modulation

FSK Modulation

FM Modulation


Specifications

Sub-carrier oscillator Frequency range: 0.8 f – 1.2 f with f = 100 kHz to 10 MHz. Waveform: triangular signal. External capacitor. VDD = 1.5V

RF oscillator Frequency range: from 0.75 GHz to 1.75 GHz. VDD = 1.5V.


Building blocks of the UWB Transmitter

Relaxation Oscillator Ring Oscillator


Sub-carrier signal at 80- 120kHz


Sub-carrier signal at 8 – 12MHz


RF signal at 1.25 GHz center frequency

At the output of the integrated circuit


Filtered RF signal at 1.25 GHz center frequency

Across the 50 Ohm radiation resistance of the antenna: 3.5 mW


Current consumption of the building blocks

Simulation results in UMC 0.18um CMOS with RF options

• VDD = 1.5V.• Sub-carrier oscillator: 0.2 mA.• RF oscillator: 3 mA.• Output buffer: 4 mA.


Layout of the FM-UWB Transmitter in UMC 0.18um CMOS

GND RF-OUT GND

VH

VL

Ibias

Osc-en

VDD

Rv-moy

Isub Vcycl Csub

Surface: 0.7mm X 0.7mm


Next steps

UMC 0.18um CMOS Techno.• Manufacturing of the FM-UWB Transmitter.• Test of the FM-UWB Transmitter.

0.13um CMOS or 0.35 um, 0.25 um BiCMOS SiGe 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 slide 1 john f.m. gerrits 1, john r. farserotu 1, catherine dehollain 2, norbert...

Documents