Greetings, On Wed, 19 Jan 2022, Masataka Ohta wrote:
Jay Hennigan wrote:
Radar receivers are typically some form of direct conversion with rather good selectivity, synchronized to the frequency of the transmitted pulse.
No. Direct conversion stage has no inherent frequency selectivity and is subject to saturation by noise of any frequency unless the noise is removed in advance.
Selectivity can be enjoyed only after successful unsaturated conversion, direct or to IF.
But, the solution is to put an LC band pass/stop filter between an antenna and a receiver, though I have no idea on the difficulty to obtain FAA/FCC approval to do so.
By adding an LC bandpass filter will add to the propogation delay of the receiver. When the round-trip time of the echo at 1000 feet is only 2 microseconds, that added delay will throw the RA out of calibration. Perhaps the calibration circuitry can deal with this added delay. --- Jay Nugent WB8TKL