Multiplex communications – Wide area network – Packet switching
Patent
1991-07-31
1993-10-05
Safourek, Benedict V.
Multiplex communications
Wide area network
Packet switching
370 70, 370123, 4551891, 455324, H04J 100
Patent
active
052512185
ABSTRACT:
A digital radio frequency (RF) or intermediate frequency (IF) receiver for frequency division multiplexed (FDM) signals contained in a predetermined FDM band including an RF amplifier, an RF bandpass anti-alias filter, and an analog-to-digital (A/D) converter. The sample frequency F.sub.s of the A/D converter is lower than the lowest frequency in the predetermined FDM band and is selected to meet certain specified conditions based on the passband and stop band edges of the anti-alias filter so that the output of the A/D converter contains a non-distorted aliased frequency down converted digital version of the predetermined FDM band which is located between 0 Hz and one-half the sampling frequency. A digital complex mixer responsive to the digital output of the A/D converter translates the spectrum of the sampled digital received signal to center the desired FDM channel at zero frequency (DC). Digital low pass filtering isolates the desired channel centered at DC, and a digital complex mixer can be used to translate the isolated selected channel to a predetermined IF frequency. The in-phase portion of the digital IF centered selected channel or the DC centered complex envelope selected channel can then be provided to appropriate demodulation or decoder networks.
REFERENCES:
patent: 4312062 (1982-01-01), Bellanger et al.
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patent: 4590595 (1986-05-01), Morimura
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patent: 4884265 (1989-11-01), Schroeder et al.
patent: 4912775 (1990-03-01), Matsuura
"Multirate Digital Signal Processing", Crochiere and Rabiner, Prentice-Hall, Inc., Englewood Cliffs, N.J. 07632, 1983, pp. 42-47.
Devendorf Don C.
Ichiroku Kikuo
Kelley Edwin A.
Stone Wade J.
Denson-Low W. K.
Grunebach Georgann S.
Gudmestad Terje
Hsu Alpus H.
Hughes Aircraft Company
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