How Passive Radar Works

I read a lot about passive radars trying to leech off of opportunistic waves, and lots about actual troops preferring to play hide-and-seem with anti-radiation weapons just to use active machines.

A config that strikes me as obvious but doesn’t seem to be popular would be just bistatic where you fire your own transmitter far away from yourself?

There’s got to be a reason, but it seems like best of both worlds.

If one visualizes the electromagnetic field in the environment, including all objects in it and any changes, one would naturally come across many applications in sensing the associated changes in the field. One classic example is the eavesdropping case at Moscow US embassy in the former Soviet Union.

What's this website? Who put it up?

Those have always been good questions to ask, but especially these days.

Are there any clever tricks for the data processing involved here, given that the delay is a shift in the time domain and the Doppler effect is a shift in the frequency domain? Maybe involving fractional Fourier transforms, or wavelets?

I wonder if the many Starlink satellites can be used for this? True, the signals are low and are steered, but the nature of steering creates many side lobes that will be useable in this manner. It would be a complex computational task with satellites in motion as well as ground stations transmitting on offset frequencies. I suspect various research/military labs are playing with this?

I want this, but I do not have the experience with radio signals to build this myself without more guidance. Is there a DIY proof of concept I could lean on? How much more challenging will this be if you are in an area with overlapping FM signals from 2 transmitters sending the same signal?

a website for passive radars, cool xD