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Echo Distortion in the FM Transmission of Frequency-Division Multiplex

1952; Institute of Electrical and Electronics Engineers; Volume: 40; Issue: 3 Linguagem: Inglês

10.1109/jrproc.1952.273790

2162-6634

W. J. Albersheim, Jens Schäfer,

Full-Duplex Wireless Communications

The composite multiplex signals generated by frequency-division methods long standard in telephone communication, can be transmitted by the new transcontinental broad-band FM radio relays. Signal intermodulation by echoes must be minimized. Such intermodulation is investigated in this paper experimentally and analytically. Two types of echoes are considered: (1) Weak echoes with delays exceeding 0.1 microseconds, caused mainly by mismatched long lines; and (2) Powerful echoes with delays shorter than 0.01 microseconds, caused by multipath transmission, and leading to selective fading. Using random noise signals, the distortion is evaluated as a function of various parameters of the echo, the baseband and the rf modulation.