Doppler Speed Sensors for Automotive Applications

The problem of wheel and vehicle speed measurements in automotive antiskid systems is discussed and a microwave doppler radar solution proposed. A straightforward design approach for self-mixing Gunn device radar detectors using a new current waveform approximation is presented allowing simple observation of the effects of device and circuit parameter variations on the overall performance of the detector. The operation of transferred-electron and baritt devices is compared with particular reference to sensitivity and reliability under the strict environmental conditions imposed by the application. The use and performance of fully integrated microstrip circuitry is considered in the light of the cost/performance ratios required in the motor industry, the result being a hybrid integrated circuit with the oscillator, antenna and amplifier located on the same substrate.