Funnily enough, we did discuss such a project during the EW course I did about a decade ago.
It's easy enough to deduce from the size of a typical radar gun that they use a wavelength in the low centimetric region - any longer, and the beamwidth from such a small antenna would be too broad. Indeed, a quick dig online confirms that they are typically Ku and Ka band, i.e. 1-2 cm. The easiest way for such a device to work is by measuring the Doppler shift of the returned signal, as this gives you the speed, which is after all what you want. (This also explains why radar guns need regular calibration, as without this their accuracy is doubtful.)
Our preferred solution was not to jam the system altogether, which would be difficult and probably require a lot of power. Rather, we proposed a variant of a jamming system called a velocity gate stealer. A VGS generates an artificial return which is 'captured' by the threat radar tracking algorithms; by slowly changing the frequency, it seduces the tracking algorithm away from the weaker real return. We imagined a similar system that would generate an artificially strong echo with a frequency shift such that it presented an apparent Doppler corresponding to some ludicrously high speed. PC Plod would either be tapping the radar gun in confusion or would have to stand up in court and assert that the suspect 1986 Ford Orion had been doing 230 mph up the A17.
It's easy enough to deduce from the size of a typical radar gun that they use a wavelength in the low centimetric region - any longer, and the beamwidth from such a small antenna would be too broad. Indeed, a quick dig online confirms that they are typically Ku and Ka band, i.e. 1-2 cm. The easiest way for such a device to work is by measuring the Doppler shift of the returned signal, as this gives you the speed, which is after all what you want. (This also explains why radar guns need regular calibration, as without this their accuracy is doubtful.)
Our preferred solution was not to jam the system altogether, which would be difficult and probably require a lot of power. Rather, we proposed a variant of a jamming system called a velocity gate stealer. A VGS generates an artificial return which is 'captured' by the threat radar tracking algorithms; by slowly changing the frequency, it seduces the tracking algorithm away from the weaker real return. We imagined a similar system that would generate an artificially strong echo with a frequency shift such that it presented an apparent Doppler corresponding to some ludicrously high speed. PC Plod would either be tapping the radar gun in confusion or would have to stand up in court and assert that the suspect 1986 Ford Orion had been doing 230 mph up the A17.
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