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Digital RF bandpass filter for FM radio translators


There was no response to this problem in DSP, so I thought maybe someone involved with RF or software-defined radio might be able to help.

Our public radio station uses an FM translator to receive a 91.5 MHz signal and rebroadcast it at 106.7 MHz.  The problem is that there is a nearby station on 91.1 MHz causing interference, and our RF analog bandpass filter skirts are only -10 dB down at that frequency.  Using multiple tuned RF filters in series helps, but the filter response of our cavity filters vary too much with temperature.

Is it possible to implement a digital RF bandpass filter for this?  It wouldn't need to be tuned, and I was wondering if it's possible to apply a (FIR?) 500 kHz bandpass filter at 91.5 MHz.  I think we'd need to sample at 275 MHz, and our 91.5 MHz analog bandpass filter could function as the anti-alias filter.  Since our translator/amplifier input is 91.5 MHz, is it possible to do this at RF, without any downconversion and upconversion to/from baseband?

Does Analog Devices have a demo board that can do this?  I started looking at software-defined radio systems, but don't know if any can receive and transmit at 91.5 MHz simultaneously.