This paper describes the overall architecture of the first long‐distance microwave telephone transmission system to use Single‐Sideband Amplitude Modulation in the microwave transmission path. Compared with commonly used frequency modulation systems, the AR6A Single‐Sideband Microwave Radio System more than doubles the number of telephone circuits that can be carried per unit of microwave bandwidth. Included in the description are the system design model, performance objectives, and the allocation of performance impairments. Also discussed are the computer‐controlled automated maintenance features and the results of laboratory and field tests.

An adaptive Volterra linearizer for reducing channel nonlinearities in QAM data transmission systems is described and its performance is evaluated. The linearizer is implemented as a modem receiver digital circuit which employs two read-only memories that are programmed to cancel either third or fifth order nonlinearities. The memory outputs are scaled by adaptive coefficients which minimize the channel nonlinearity. In a 64-QAM digital radio system, the linearizer is shown to reduce nonlinear residual error rates by five orders of magnitude.

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