Close-range radar to detect electrical devices in the surrounding area via non-linear mixing of multiple RF signals.
It works by flooding the target area with two separate RF carriers.
One is an unmodulated CW carrier at around 14 GHz and the other is an AM modulated carrier at around 2 GHz.
These two RF carries "mix" within the electronics of the target device, provided it contains non-linear electrical components like diodes or transistors - and is unshielded.
The result of the two RF carriers mixing is a third RF signal at either 12 or 16 GHz containing the AM modulated tone. For this example, we'll use the 12 GHz signal as that is a common satellite band and receiver technology for that frequency is very common.
The AM modulated 12 GHz carrier is then filtered and downconverted to baseband by mixing it with a low-power sample of the transmitted RF carriers.
The baseband signal is then processed to detect if the audio tone is present, indicating that a potential target is within the beamwidth of the antennas.
