Novatel Communications Ltd.

Harris Canada, Inc.

Darrell W Barabash

John Godfrey McRory

Theo J Smit

Alan D McGrath

A cellular subscriber modem for receiving CCITT-type quadrature amplitude modulated (QAM) signals. The cellular modem includes a novel symbol detector that converts received symbol information to polar notation. The detector's constellation thresholds include a circular threshold having a radius greater than the magnitude of the innermost symbols, but less than the magnitude of the outermost symbols, and radially spaced thresholds, which further discriminate between the outermost symbols. As a result, special cellular-compatible modem equipment need not be connected between the public-access switched telephone network and the computer equipment at the other end, which means that a CCITT-compatible cellular subscriber modem can then be treated as any other type of CCITT-modem. The detector may be implemented in the software of a standard modem processor, or as several analog comparator circuits.

QAM detector which compensates for received symbol distortion induced by

A cellular-telephone transmitter (10) employs a vector modulator (14). An integrating circuit (52) generates the integral of the message signal and applies it to circuitry (54, 56) for generating in-phase and quadrature modulation signals representing the cosine and sine, respectively, of the integrating-circuit output. The vector modulator (14) produces the desired FM signal by adding together quadrature and in-phase versions of a carrier in proportion to the values that the quadrature and in-phase modulating signals represent.

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Calgary, Canada

Darrell W Barabash