Device for the coherent demodulation of time-frequency interlace

Details Device for the coherent demodulation of time-frequency interlace Device for the coherent demodulation of time-frequency interlace

1992-01-14

1994-04-26

Chin, Stephen

Pulse or digital communications

Repeaters

Testing

375 59, 375 94, 370 20, H04K 110, H04L 2728

Patent

active

053073762

ABSTRACT:
A method and apparatus for the coherent demodulation of a digital signal constituted by digital elements distributed in the time-frequency space and transmitted in the form of symbols constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of said digital elements and broadcast simultaneously, the digital signal also including reference elements having a known value position in said time frequency space. The method includes a Fourier transform of at least samples of said digital signal containing said reference elements from a frequency domain into a temporal domain, a weighting of the transformed samples in the temporal domain by a rectangular temporal window f.sub.n, a thresholding of the transformed samples in the temporal domain to eliminate any samples below a predetermined threshold, and a reverse Fourier transform of the samples remaining after said weighting and thresholding from the temporal domain into the frequency domain for projection onto said digital signal. The threshold level can be fixed or varied based on the power level of the noise affecting the transmission channel or an estimated pulse response of the transmission channel.

REFERENCES:
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patent: 4802109 (1989-01-01), Machida
patent: 4881241 (1989-11-01), Pommier et al.
M. Alard and R. Lassalle, Principles of modulation and channel coding for mobile receivers, EBU Review-Technical; Aug. 1987, pp. 168-189.
Robert C. DiPietro, An FFT Based Technique for Suppressing Narrow-Band Interference in PN Spread Spectrum Communications Systems, IEEE 1989, 19891 pp. 1360-1363.
Aiichiro Tsuzuku and Yoshihiko Ishikawa, Mobile Teletext Reception Using Signal Processing in Frequency Domain, IEEE 1989; pp. 0422-0425.
Schaller, "Verwendung der schnellen Fouriertransformation in digitalen Filtern", (Nachrichtentechnische Zeitschrift, vol. 27, No. 11, Nov. 1974, pp. 425-431.

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