A new CPM modem for radio applications using differential detection

A new digital CPM modem for low capacity (nx2 Mb/s) radio systems operating in the frequency bands 10 GHz up to 55 GHz is presented. Emphasis in the system design was put on immunity against system imperfections specifically in the RF section such as oscillator frequency jumps and nonlinearities. The system concept allows for inexpensive RF parts whose imperfections can be compensated using sophisticated signal processing algorithms such as joint differential multistage Viterbi detection and additionally concatenated FEC. These are implemented with fully digital low cost ASICs. Furthermore very good BER performance is achieved requiring less than 10dB E/sub b//N/sub o/ for BER=10/sup -5/. Concerning resistance against carrier frequency jumps a quite impressive value of up to 200 kHz can be tolerated without any bit error.