Multiplex communications – Generalized orthogonal or special mathematical techniques – Plural diverse modulation techniques
Patent
1997-08-04
1999-08-31
Hofsass, Jeffery A.
Multiplex communications
Generalized orthogonal or special mathematical techniques
Plural diverse modulation techniques
370208, 375326, 375327, H04J 1100
Patent
active
059462922
ABSTRACT:
A digital receiver uses a local oscillator to down-convert an orthogonal frequency-division multiplexed signal that has been modulated by differential phase-shift keying, and performs further processing to obtain a differentially demodulated array of phase values. According to a first aspect of the invention, the digital receiver detects a carrier offset, applies a corresponding phase correction to the values in the array, then shifts the entire array by an amount corresponding to the carrier offset. As a result, the local oscillator need be tuned only in a frequency range equal to the subcarrier spacing. According to a second aspect of the invention, the local oscillator is tuned within a range equal to the subcarrier spacing multiplied by a certain integer, the array is shifted by a multiple of this integer, and the phase correction is eliminated.
REFERENCES:
patent: 4894845 (1990-01-01), Janssen et al.
patent: 5371761 (1994-12-01), Daffara et al.
Ohkubo Tadatoshi
Ohsuga Yoshiharu
Taura Ken-ichi
Tsujishita Masahiro
Hofsass Jeffery A.
Mitsubishi Denki & Kabushiki Kaisha
Townsend Clement
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