An h.f. channel simulator using a new Rayleigh fading method

The paper describes a new method of producing a discrete-level approximation to a Rayleigh fade by means of a quasi-random digital process. This offers considerable advantages over existing methods in cost, simplicity and flexibility, having an exactly repeatable fading pattern and a fading rate which may be easily changed by varying the digital clock rate. Mathematical analysis and experimental evidence show that the output closely approximates to a Rayleigh fade in all respects. A description is given of a prototype h.f. ionospheric channel simulator incorporating the design. In addition to Riceian fading the prototype allows the simulation of two-path propagation, Doppler shift, and additive Gaussian noise. Some practical applications of the simulator are discussed.