Monopulse azimuth radar system for automotive vehicle tracking

Abstract

A monopulse vehicular radar system for tracking a target about an automotive vehicle senses a transmitted signal reflected back from the target and received at two different locations, determines the sum and the difference of the reflected signals sensed at the two locations, and compares the sum and difference to determine the deviation of the target from a reference azimuth. A source frequency provided by a Gunn diode is applied to and transmitted by a two-lobe monopulse antenna. The antenna lobes detect the reflected signals from the target by sensing them at the two different lobes. A hybrid junction provides sum and difference signals to mixers which homodyne the signals to produce sum and difference Doppler frequency signals using the source frequency. The Doppler frequency signals are amplified and then compared to determine the deviation of the target from the reference azimuth. The comparison process can be done digitally by converting the amplified frequency signals to digital signals which are then processed in a digital signal processor, or the comparison may be done in analog fashion using a phase/quotient detector. The range or distance of the target is determined by shifting the source frequency between two frequencies during transmission and frequency shifting the sum and difference Doppler frequency signals in similar fashion following reception by the antenna.