Skip to Main Content
A novel long haul 5 GHz 16 QAM digital radio system, which has 200 Mbit/s transmission capacity within the 40 MHz interleaved channel allocation, is proposed and described. It is designed to be overbuilt on existing FDM-FM routes with an approximately 50 km repeater spacing. To achieve the 5 bit/s/Hz RF spectral efficiency, the 16 QAM modulation and Nyquist cosine roll-off spectral shaping techniques ( ) are investigated. Then a new signal shaping filter, differential encoding and carrier recovery techniques are presented. Finally, the effects of TWT amplifier nonlinearity on a 16 QAM signal are experimentally investigated.