Need for a new approachNeed 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 approachesPrevious approachesTime 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.

Our approach…Our approach…

Transmitted signal :- Yt = A sin(ωt)Returned signal :- Yr = 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.

ImplementationImplementation•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 SuperHeterodyne receiver’s principle.•Compensation for additional phase delay in transmitting and receiving paths.•Works in wide rangeD(min) = c/( ∆f *225)D(max) = c/(8∆f)(using 24 bit ADC)∆f = freq. step increment