Mutual fluctuations between carriers in a broadband millimeter-wave communication system

Mutual fluctuations between two carriers in a broadband millimeter-wave communication system may be observed from the heterodyne signal spectrum of the carriers. Laboratory measurements made on equipment developed for local multipoint distribution system (LMDS) applications indicated the degradation in the heterodyne spectrum was mainly in the form of increased background noise with L(f) close to the beat-tone carrier essentially unaffected. Synchronization and orthogonal relationship between the carriers are therefore well preserved by the millimeter-wave link. This property is a key requirement for supporting modulation schemes with high spectral efficiency.