How do radar detectors work?
In a nutshell: Modern radar detectors are superhetrodyne receivers, similar to a scanner. First, they use a microwave horn antenna to receive the radar signal. The radar signal is generally passed on to a first mixer stage, where it is mixed with a first local oscillator to produce an IF. The IF is generally passed on to one or two more mixer and IF stages depending on the design. Finally the signal is detected, and then handled by the processing and control circuitry to produce a visual and audible alert. Radar detectors usually sweep the first LO (and sometimes the 2nd or third too) in order to sweep the different police radar bands for a signal. They will also contain multiple filter and amplifier stages.
