FPGA resources for simple heterodyne filter

A very simple heterodyne tunable filter can be designed with up-samplers, two heterodyne units, two low pass filters, a single prototype filter and a down-sampler. A complicated prototype band pass filter can be tuned over a range of 90-degrees in the unit circle by simply changing the heterodyne frequency. The simple heterodyne tunable filter offers hardware savings over the other heterodyne filters at the cost of a smaller tuning range and the need for the fixed low-pass filters to remove images.