The processing of modulation signal for digital radio transmission

The paper summarizes the basic problems of the digital transmission of voice signals over radio channels. It points out demands regarding the bandwidth of transmission channel and the kind of modulation to fulfill compatibility of the digital and analog transmission through standardized channels. The premodulation filtering of the digital modulation signal based on the weighted response of the ideal lowpass filter is described. There are given technical possibilities how to realize the digital premodulation filter with the memory (ROM) or the shift register with analog weighted taps. At the end the realization of the filter with CMOS circuits is given.