Pulse or digital communications – Transmitters – Quadrature amplitude modulation
Patent
1994-10-27
1997-02-04
Chin, Stephen
Pulse or digital communications
Transmitters
Quadrature amplitude modulation
332103, 375308, H04L 2736, H04L 2720
Patent
active
056006780
ABSTRACT:
A programmable digital modulator and methods of modulating digital data for transmission by a communication system according to operating parameters selected for various applications are provided. A two-chip system is utilized by a preferred embodiment of the invention. One chip comprises a PROM for storing impulse response data which would result from filtering the data to be transmitted. The second chip comprises a data interface for accepting input data, an address generator for generating an address of the PROM where the impulse response data is stored which corresponds to the data input to the chip and for causing the PROM to output the impulse response data stored at the address generated, and a data modulator for modulating a carrier signal with the impulse response data provided by the PROM. To account for intersymbol interference which occurs in some types of digital communications, an accumulator is further provided by the second chip for summing impulse response data associated with more than one input where the impulse response data overlap in time. An interpolator is also provided by the second chip to generate additional data samples to be used to modulate the carrier signal enabling a greater output sample rate. A data scrambler is also provided to scramble either binary data or data symbols according to the particular mode of communication selected.
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Petranovich James E.
Rhodes F. Matthew
Chin Stephen
Jaquez Martin J.
Pacific Communication Sciences, Inc.
Phan Hai H.
Richman, III Merle W.
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