Improving intrusion detection radar

The first monostatic microwave intrusion detection sensor with range cutoff was introduced in 1984. This range cutoff circuit as used in the Model 375 and 385 has proven very effective in preventing nuisance alarms beyond a user-defined range. The Intrepid Digital Transceiver introduced in this paper builds upon this proven technology with the addition of a unique digital signal processing routine that measures range to the intruder. Intrepid Digital Transceiver alternately transmits pulses at two discrete frequencies within K-Band. When an intruder enters the detection zone, the Doppler response at each frequency is digitally recorded. The difference between the two frequencies is controlled so that the phase angle between the two Doppler responses can be used to determine the unambiguous range to the target. As a byproduct of the process targets approaching the transceiver can be distinguished from those moving away from the transceiver. Range information is used to enhance the signal processing. The amount of signal integration is increased with range in proportion to the width of the detection pattern so as to optimize the signal to noise ratio (SNR).