Quadrature amplitude modulator including a digital amplitude modulator as a component thereof
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United States of America Patent
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Sep 12, 1995
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N/A
app pub date -
Apr 14, 1993
filing date -
Apr 14, 1993
priority date (Note) -
Expired
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Abstract
The invention provides various embodiments of a balanced modulator, each of which involves one or more individual amplitude modulators which, individually, do not provide suppressed-carrier outputs. A first embodiment employs a single amplitude modulator whose carrier input is selectively delayed by a half wavelength, depending on the polarity of the input modulating signal, and whose amplitude input receives the absolute value of the modulating input signal. A second embodiment involves summation of the outputs of two amplitude modulators whose carrier inputs are responsive to carrier signals offset by a half carrier wavelength and whose modulating signal inputs are responsive only to signals of respectively opposite polarity. Further, quadrature amplitude modulation (QAM) modulators are provided by a combination of the above-described modulators. Moreover, another embodiment of the QAM modulator involves use of an amplitude modulator operating on polar coordinate representations of the input modulating signal. The invention is useful in single sideband modulation, up-conversion, down-conversion, synchronous detection, product detection, and the like.
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