1. Need for a new approach Noisy traffic environment – radiation as well as sound. Deceivability by similar type of device equipped on other vehicles. Vulnerability to weather conditions like foam, raining, high temperature and air blowing. Real time application so target must be continuously observed to take control action. Phase delay based collision avoidance RADAR for smart automobiles IIIT Allahabad Previous approaches Time of flight method RTT too small for EM waves so requires high clock speed. Pulses must be separated by at least RTT (which is unknown) otherwise gives wrong results. Hence continuous monitoring not possible. Sonar:- highly vulnerable to environmental noise and weather conditions, Frequency changes significantly due to doppler effect; so sharp filtering not possible.

2. Our approach… Transmitted signal :- Y t = A sin(ωt) Returned signal :- Y r = B sin(ωt - 2KD – Ø) Where:- Ø = phase change occurred due to reflection at target surface (π for perfect reflectors but not for all). phase difference between transmitted and returned signal: ∆ψ= 2KD + Ø = (4πD/c).f + Ø So distance: D = (c/4π).d(∆ψ)/df = (c/8π).|d(VPHS)/df | Absolute value of ∆ψ can not be measured but ∆ψ%2π can be measured using phase detector.

3. Implementation Operates in world wide free ISM band (2.4 GHz). Frequency kept variable to overcome deceivability. Extra VCO is used to provide settling time. Dynamic frequency filter - realized using Super Heterodyne receiver’s principle. Compensation for additional phase delay in transmitting and receiving paths. Works in wide range D(min) = c/( ∆f *2 25 ) D(max) = c/(8∆f) (using 24 bit ADC) ∆f = freq. step increment