Doppler radar for distinguishing between approaching and receding targets and having increased frequency response

摘要

CW is beamed continuously by a radar and is sampled continuously in the radar; the radar continuously senses reflections that are returned to the radar. Only if the distance to a reflecting target is changing significantly per unit time is there an output generated; the output is a positive DC voltage if the distance is closing and a negative DC voltage if the distance is opening. An annunciator arrangement responds to the output DC voltage. Reflection frequency energy is mixed with a sampling of the CW to obtain the difference frequency. At the same time, reflection frequency energy is mixed with +90 degrees phase advanced sampling of the CW to obtain the difference frequency. The phase angle between the two difference frequency outputs is increased by +90 degrees and then are channeled to an analog multiplier. The DC output of the analog multiplier operates an annunciator. A much wider range of doppler frequency (viz. 100:1) is obtained by use of a plurality of processing circuits, connected in parallel and designed for response to overlapping frequency bands, the respective DC outputs of the parallel connected circuits are summed. The overall response is approximately flat over the wide frequency range.