I might explain more what I'm trying to implement here... I've got a bit of experience using DSP's, FPGA's and microcontrollers, but what I'm not that familiar with is radios. What I want to be able to implement is a variable bandpass filter... so say it accepts an input from an aerial, then the user can select a frequency and bandwidth to filter. I'd like it ro run into the microwave spectrum, so say any signal between 20GHz or so down to maybe 10kHz? So say you could set it to accept 720 kHz with a bandwidth of 45kHz, or maybe 12GHz with a bandwidth of 1GHz.