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Digital RF bandpass filter for FM radio translators

Question asked by Doug2D on Oct 13, 2014
Latest reply on Oct 16, 2014 by Doug2D



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.