Pulse or digital communications – Repeaters – Testing
Patent
1988-08-29
1990-01-23
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
329308, 375 84, 375 97, H03D 318, H03K 904, H04L 2722
Patent
active
048963364
ABSTRACT:
A digital modem is provided for demodulation of differential phase-shift keyed (DPSK) signals in a land mobile satellite receiver. The DPSK demodulator comprises a coarse frequency and lock detect module for identifying and estimating the frequency of the input signal, a numerically controlled oscillator (NCO) for generating in-phase and quadrature signals from the input signal, one pair each of delayed and non-delayed integrate and dump (I&D) modules, a symbol timing module for achieving symbol synchronization by determining the dump time of the I&D modules, a dot product detector for receiving the output of the non-delayed I&D modules and providing a detected data output, and an AFC loop comprising a cross product detector and an AFC loop filter that provides feedback to the NCO and lock detect module. The DPSK demodulator achieves symbol synchronization independent of carrier phase or frequency and at low signal-to-noise ratios. Overall, the modem achieves the theoretical bit error rate capability of DPSK on a narrow band, white Gaussian noise channel with minimal implementation loss.
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J. F. Roesch, Jr., "An All Digital Demodulator Using Off-the-Shelf VLSI Technology," Milcom Trans., vol. 3, pp. 46.4.1-46.4.5, Oct. 1986.
F. D. Natali, "Noise Performance of a Cross-Product AFC With Decision Feedback for DPSK Signals," IEEE Trans. Commun., vol. COM-34, No. 3, pp. 303-307, Mar. 1986.
Henely Steven J.
Walby Mark D.
Hamann H. Fredrick
McFarren John C.
Murrah M. Lee
Rockwell International Corporation
Safourek Benedict V.
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