MOTION DETECTOR UNIT

摘要

A unit for detecting a moving person or object by means of doppler frequency shift. The unit comprises a microwave circuit board (1) accommodating an oscillator and a mixer, and an antenna board (2) carrying transmit (8) and receive (7) patch arrays. In the assembled unit the two boards (1, 2) are intimately secured together. Coupling between the microwave circuit and the antenna arrays is achieved by two slots (5, 6) resonant at the oscillator fundamental frequency, formed in the ground plane (4) of the microwave board (1). Feed striplines (9, 10, 17, 19) on the two boards lie orthogonal to and sandwich the slots (5, 6). The stripline/slot arrangement suppresses emission at the oscillator second harmonic frequency.