How Passive Radar Works

#1

Post by surprisetalk » Thu, Apr 09, 2026, 12:35 PM UTC

How Passive Radar Works
passiveradar.com

Re: How Passive Radar Works

#2

Post by sebasv_ » Sat, Apr 11, 2026, 11:29 AM UTC

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?

Re: How Passive Radar Works

#3

Post by quantum_state » Sat, Apr 11, 2026, 11:30 AM UTC

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.

Re: How Passive Radar Works

#4

Post by quantum_state » Sat, Apr 11, 2026, 11:38 AM UTC

sebasv_ wrote: post #2

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?

Would suggest to take a look at Jackson’s book on classical electrodynamics to get some intuition.

Re: How Passive Radar Works

#5

Post by Chrisszz » Sat, Apr 11, 2026, 11:50 AM UTC

a website for passive radars, cool xD

Re: How Passive Radar Works

#6

Post by lormayna » Sat, Apr 11, 2026, 11:59 AM UTC

sebasv_ wrote: post #2

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?

This is a very good point to start: https://www.rtl-sdr.com/tag/passive-radar/

If you have more than one receiver, the main issue is time sincronisation between the receivers.

Using the two transmitters will complicate things a lot

Re: How Passive Radar Works

#7

Post by smartscience » Sat, Apr 11, 2026, 12:34 PM UTC

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?

Re: How Passive Radar Works

#8

Post by willis936 » Sat, Apr 11, 2026, 1:03 PM UTC

lormayna wrote: post #6

sebasv_ wrote: post #2

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?

This is a very good point to start: https://www.rtl-sdr.com/tag/passive-radar/ If you have more than one receiver, the main issue is time sincronisation between the receivers. Using the two transmitters will complicate things a lot

For this kind of thing you need to step up to the kraken.

Re: How Passive Radar Works

#9

Post by [deleted] » Sat, Apr 11, 2026, 1:17 PM UTC

smartscience wrote: post #7

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?

[deleted]

Re: How Passive Radar Works

#10

Post by vscode-rest » Sat, Apr 11, 2026, 1:18 PM UTC

smartscience wrote: post #7

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?

Lots of clever tricks, all ITAR controlled.