Pulse or digital communications – Transmitters – Antinoise or distortion
Patent
1994-09-29
1997-05-27
Chin, Stephen
Pulse or digital communications
Transmitters
Antinoise or distortion
375272, 375275, 375278, 375303, 375340, 375348, 332100, 332124, 455 44, 455110, 36472416, H04K 102
Patent
active
056338937
ABSTRACT:
Continuous phase modulated (CPM) signals, such as quaternary CPFSK signals, are filtered to limit their bandwidth while simultaneously minimizing the amount of amplitude modulation and intersymbol interference introduced by this filtering process. By designing a modulation filter such as a finite impulse response (FIR) filter to add only a nominal, controlled amount of amplitude modulation, high efficiency, nonlinear power amplifiers may be employed to transmit the filtered CPFSK signals. Although the filter adds a small amount of amplitude modulation and intersymbol interference, digital signal processor-based receivers satisfactorily demodulate this type of signal using sequence estimation algorithms such as the Viterbi algorithm. Thus, the filtering of CPM signals permits narrowing of the transmitted signal spectrum while managing the intersymbol interference resulting from the controlled amount of amplitude modulation added by filtering. Narrowed bandwidth along with high efficiency, nonlinear power amplifiers make the present invention particularly well suited to narrowband mobile radio communications.
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Chen Jyun-chen
Lampe Ross W.
Chin Stephen
Ericsson Inc.
Le Amanda T.
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