Digital premodulation filter.

摘要

A programmable premodulation filter (163,165,167) having a finite impulse response to digitally filter a digital data signal (154) to provide a modulation signal for modulating an RF carrier signal is described. A digital summer (163) and accumulator (165) are programmed to provide a finite impulse response to a bimodal impulse signal which represents the input digital data signal (154). Several impulse response functions g(t) are stored in a ROM (or RAM) (155) and may be selected to reprogram the digital filter (163,165,167) to provide a desired modulation format. When a RAM (155) is used, additional impulse response functions may be input (184) to the RAM (155) and the stored impulse response functions may be dynamically modified to provide the desired modulation format.