All Solid State 1800-Channel Transmitter-Receiver for 6 ~ 8 GHZ Radio Relay Systems

This paper describes an all solid-state heterodyne transmitter-receiver in the 6 to 8 GHz band with a capacity of up to 1800 telephone channels. The equipment is fitted with an NEC-0.5 micron gate GaAs MESFET pre-RF amplifier having a noise figure of less than 2.5 dB at 6 GHz, and with an RF amplifier formed by two Si DDR IMPATT diodes for producing an output of 4W. After the discussion of thermal noise and intermodulation noise, the results of the system test are described. In the system test conducted for six hops in the 8 GHz band, a 0.9 pWop/km for 1800 telephone channels was achieved.