A New Generation of Digital Microwave Radios for U.S. Military Telephone Networks

A new, versatile digital microwave radio has been developed for the U.S. Government under the Digital Radio and Multiplexer Acquisition (DRAMA) Program, which will convert transmission facilities of the Defense Communication System from analog to digital signal format. The radio can be configured for either space or frequency diversity in either the 4 or 8 GHz military bands. A choice of quadriphase shift keying or quadrature partial response signaling provides bandwidth efficiencies of 1.0 and 1.9 bits/s/Hz of occupied RF bandwidth. The design of the radio is presented through detailed descriptions of the multiplexer, modem, RF, protection, and timing subsystems. Major tradeoffs leading to the selection of the modulation types and spectral filtering method are discussed.