Spring 2006 EE 548 Ultra Wideband Radio: Ranging Spring 2006

Approaches to ranging (IEEE TG4) The ranging subcommittee has identified 5 different techniques or doing ranging. Time of Arrival Ranging Angle of Arrival Ranging Time Difference of Arrival Ranging Signal Strength Ranging Near Field EM Ranging

Spring 2006 Ranging: time of arrival Node L

Spring 2006 Ranging: critical issues Detecting the peak of the received signal Correlating the received signal with the transmitted signal Mitigation of the effects of noise and jitter

Spring 2006 Ranging: why use UWB? Wide bandwidth and short pulse duration provide –More target information –Improve range accuracy –Improve resilience to passive scatterers (clutter) –Mitigate destructive multipath effects from ground reflection –Enable a narrow antenna beam pattern

Spring 2006 Ranging use short duration pulses: traditional RADAR approach

Spring 2006 Errors in time of arrival ranging: Cramer-Rao lower bound (CRLB)

Spring 2006 CRLB for square pulses

Spring 2006 CRLB for square pulses (II)

Spring 2006 CRLB for square pulses: example Assume UWB, B= = 7.5GHz PSD = FCC max 2G 0 =9.86x joules/Hz N 0 =2x W/Hz, at room temp and 7dB noise figure

Spring 2006 Improving the accuracy in TOA ranging Need to accurately compare received pulse with transmitted pulse to determine time delay Use correlation techniques –Slide correlation window in time –Look for maximum

Spring 2006 Correlation technique for TOA based ranging T Rectangular pulse of duration T s(t)

Spring 2006 Output of matched filter for square wave pulse 2T0 R S (  T

Spring 2006 Early-late gate synchronizer Exploits correlator output –Measures output at symmetric points in time relative to expected peak value –Then evaluates the difference When the samples are made at points that are symmetric about the peak,  R=0 When there is an unknown delay ,  R is not zero

Spring 2006 Effect of unknown delay on the output of early-late gate synchronizer 2T0 R S (  T RR  Measurement of  R enables calculation of 

Spring 2006 Lower bound on ranging errors Use multiple, repetitive pulses to average out jitter and noise to increase accuracy, at the expense of processing time

Spring 2006 Time integrating correlator (TIC) Received signal s(t) stored Reference code moved past the analog input signal Product of received signal and code are summed in a bank of parallel analog integrators Each correlator uses same code, but shifted in time When received signal is aligned with proper code, the integrator output reaches as maximum

Spring 2006 Pulse pair, offset spreading sequences, and TIC output

Spring 2006 UWB ranging is relatively immune to multipath

Spring 2006 In-building multipath measurements

Spring 2006 Through-wall sensing: RadarVision Specifications Size:56 cm x 35.5 cm x 20.3 cm Weight: 3 Hours Rechargeable Time: +/- 60 degree Vertical Field of View: > +/- 45 degree Line of Sight: 20 meter through Wood, Brick, Gypsum Wall & 20 cm Solid Concrete Shock/Vibration: Drop tested at 2 meters Humidity: 0% to >90% (non-condensing) Liquid: Water resistant (not submersible) Operating Temperature: -10 degree C to +50 degree C Store Temperature: -20 degree C to 60 degree C Emission Type: Coded ultra wideband pulses Pulse Rate: 10 Million pulses per second Transmit Power: 1.5 mW Bandwidth: GHz

Spring 2006 Example locator system Micro Air Vehicle Collision Avoidance System WeightLess than 50g SizeSmall Resolution+/- 1 foot Range50 feet Span360 degrees Update rate1000 times/sec