QPSK transmission system having phaselocked tracking filter for

Details QPSK transmission system having phaselocked tracking filter for QPSK transmission system having phaselocked tracking filter for

1985-10-25

1988-04-12

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

331 17, 332 16R, 375 67, H03C 302

Patent

active

047379685

ABSTRACT:
A system for transmitting digital data employs an angle modulated carrier signal having constant amplitude and a limited spectrum. The system comprises an offset quadrature phase shift key (QPSK) modulator with a "tracking filter" phaselocked loop at the output of the QPSK modulator. The phaselocked loop has a voltage controlled oscillator which produces a constant amplitude carrier signal at the output of the loop, and also has a low pass loop filter which reduces the spectrum of the phase modulated carrier signal. Additional spectrum shaping is obtained by connecting L-R-C circuits to the low pass loop filter to eliminate predetermined frequency components from the output of the loop.

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patent: 4528526 (1985-07-01), McBiles
patent: 4594555 (1986-06-01), Hilton

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