Digital filter design for spread-spectrum receivers

A direct-synthesis frequency synthesizer has been built which simulates the IF signal expected in the frequency-hopping radio. The inherent latency in a FIR filter design can be reduced to the time taken for a single multiply and accumulate operation. This design is part of a frequency-hopping radio system which generates the final product term in less than 1 microsecond. The use of a programmable digital signal processor is compared to a solution which uses discrete components. 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.<>