11 and 15 GHz PCM Radio-Relay Systems

This paper describes the 11 GHz and 15 GHz PCM radio relay systems, capable of conveying 65 Mb/s per radio channel, developed by Nippon Telegraph and Telephone Public Corporation NTT). The system employs 4-phase digital modulation and coherent detection. Radio equipment is fully solid-stated, using IMPATT diodes in the power amplifier. They are mainly. used for transmission circuits between telephone offices in large cities and for short haul transmission. The test results showed that compatible operation between 65 Mb/s PCM system and 2700 CH FDM-FM systems is possible, using the existing 11 and 15 GHz FDM-FM system frequency arrangement. These systems are now in use in 40 stations in Japan.