Modulation Considerations for a 91 Mbit/s Digital Radio

The DRS-8 is a 91 Mbit/s long haul digital radio system designed for use in the Canadian 8 GHz frequency band. This paper discusses the considerations which lead to the choice of Quadrature Partial Response Signaling (QPRS) for this application. A method of implementing QPRS that circumvents power amplification difficulties and permits the use of simple conventional filtering and equalization is presented. The computer analysis program and the design strategy used in the system filter design are described. Details of the signal shaping filters as well as details of carrier and clock synchronization are given. Finally, measured system performance is presented and compared with computed performance.