Modulators – Phase shift keying modulator or quadrature amplitude modulator
Patent
1997-01-27
1998-07-21
Grimm, Siegfried H.
Modulators
Phase shift keying modulator or quadrature amplitude modulator
332149, 375261, 375268, 375298, 375300, 36472413, H04L 2720, H04L 2736
Patent
active
057839743
ABSTRACT:
Methods and apparatus for converting a relatively low frequency signal, e.g., a 1.5 MHz signal, to a high frequency signal, e.g., a 30-100 MHz signal, in the digital domain. An interpolation technique is used to convert the low rate digital signal to a high rate signal and to shift the carrier to a desired frequency. This is accomplished, by first positioning the information signal, e.g., the digital wave form to be modulated on a carrier at a relatively low rate using a digital mixer operating at a fraction of the ultimate digital to analog conversion frequency. The relatively low rate signal generated by the mixing operation is then converted to a high rate signal by one or more interpolation stages. An adjustable passband filter circuit is included in each interpolation stage for selectively filtering out the signal or images created as a result of a signal padding operation performed as part of each interpolation stage. The interpolator of the present invention can be used in a modulator to translate the output of the mixer to the modulator's ultimate carrier frequency.
REFERENCES:
patent: 5412352 (1995-05-01), Graham
patent: 5534828 (1996-07-01), Okada et al.
Koslov Joshua L.
Lane Frank A.
Scarpa Carl G.
Grimm Siegfried H.
Hitachi America Ltd.
Michaelson Peter L.
Straub Michael P.
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