A matched filter communication system for multipath channels

A matched filter communication system is described whose underlying principles are based on the Rake. The point-to-point synchronous teletype system employs complex lumped-parameter networks to generate and receive a pair of long-duration, broadband signals representing Mark and Space respectively. The receiver contains a pair of matched filters whose output is a narrow pulse when the matching waveform is applied. One advantage of the system, arising from the long duration of the signals, is an increase in energy per teletype baud when operating under a peak power limitation. Another is that multiple propagation paths due to ionospheric reflection are resolved by the broadband signals, resulting in the appearance of the multipath pattern at the output of the Mark or Space matched filter. Recombination of paths is achieved by means of a recirculating delay line tuned to the teletype baud rate in conjunction with parallel multiplier-integrators in the Mark and Space channels. The combination acts as a self-adjusting correlation detector for the multipath pattern.