A High Performance 8 GHz, 8 PSK Digital Radio

Rapid growth and modernization of microwave communications is currently taking place in the commercial and military environments. Much of this growth is being accomplished through digital transmission and calls for efficient utilization of frequency spectrum allocated for LOS communications. As the bit efficiency and data rates of digital radio systems have increased, the problems associated with multipath phenomena have become more evident. To minimize outages and to meet path availability objectives diversity protection alone, in many instances, is not sufficient. However, diversity protection coupled with an adaptive equalizer will meet the objective in all but a few severe cases. This paper describes a digital radio system in the 8 GHz band with 8 PSK modulation and nominal data rates of 45 Mb/s and 90 Mb/s. Multipath propagation and its effects on digital transmission are discussed. Improvements in bit error rate threshold with the use of an adaptive equalizer designed into the receiver are also presented.