Automatic detection of moving person and/or vehicle - using receiver-mixer diodes spaced by quarter wavelength, checking mixer signals to determine which changes first, analysing sequence of Doppler signals and duration of Doppler oscillations, and performing adaptive averaging

摘要

Continuous microwaves in the GHz region are directed towards the person and/or vehicle (2). The reflected signal is detected by a microwave sensor (1) contg. two receiver-mixer diodes mutually spatially displaced by a quarter wavelength. The amplified mixed signals are evaluated. To decide whether there is an object present and moving in a defined direction, e.g. towards or away from the sensor, the sequence of Doppler signals (FM3,FM4) and the duration of the individual Doppler oscillations are derived. Both mixed signals are checked to determine which changes first. Individual time periods are selected. When a positive selection occurs the signal is subjected to adaptive averaging, the average value can be used to indicate the speed and/or to control further display devices. USE/ADVANTAGE - Pref. for use with local traffic, e.g. pedestrian, bicycle, bus, lorry of rail vehicle. Enables speed and direction of object to be detected in most traffic situations and when object has just entered detection region.