Digital filter design for frequency-hopping receivers

A direct-synthesis frequency synthesiser has been built which simulates the IF signal expected in the frequency-hopping radio. Adjacent channel amplitudes are programmable and are programmed to change every hop period. The center channel amplitude is programmable in both amplitude and envelope. In this way, both filter designs have been tested on the bench and will be tested as part of the radio system in the future. The filter configuration may also be used for continuous signals and thereby reduce the latency between input and output. Even high-order filters may be designed using this technique since the depth of the FIFOs allows over 1000 convolution products to be retained.<>