Receiver unit in radio communication system

Details Receiver unit in radio communication system Receiver unit in radio communication system

1984-11-23

1986-12-30

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

375 39, 375 98, 375102, 455 46, 455 60, 455202, H04B 168, H04B 1500

Patent

active

046334840

ABSTRACT:
A receiver unit in a radio communication system in which a transmitter unit outputs transmission data, modulated in accordance with a multilevel QAM method and containing a leakage carrier by addition of a DC offset signal to either one of the quadrature components forming the transmission data, to the receiver unit through a transmission line, including: means for receiving the transmission data; means for branching a signal received at the transmission data receiving means into first and second signal components forming the multilevel QAM data, each including the leakage carrier having a phase difference of .pi./2 radian; first channel means for demodulating the first branched signal component and including a first synchronous detection circuit and a first discriminator; second channel means for demodulating the second branched signal component and including a second synchronous detection circuit and a second discriminator; and means for recovering the carrier including a control circuit, for cancelling a noise component contained in the output signal from either one of the first and second synchronous detection circuits and for providing only a DC component representing a phase difference between a leakage carrier and a reference carrier, and a phase-locked loop (PLL) circuit, for controlling the phase difference to zero and for providing phase-locked leakage carriers to the reference carriers, having a phase difference of .pi./2 radian, to the first and second synchronous detection circuits.

REFERENCES:
patent: 3196352 (1965-07-01), Hopner et al.
patent: 3518680 (1970-06-01), McAuliffe
patent: 3818347 (1974-06-01), Holsinger
patent: 3849730 (1974-11-01), Ho
patent: 3959726 (1976-05-01), Hinoshita et al.
patent: 4114710 (1978-09-01), Katoh et al.
patent: 4355397 (1982-10-01), Stuart
patent: 4358853 (1982-11-01), Qureshi
patent: 4470145 (1984-09-01), Williams
Fukuda et al., "Design of 64 QAM Modem for High-Capacity Digital Radio Systems", IEEE, 1983, pp. 865-869.

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