Telecommunications – Receiver or analog modulated signal frequency converter – Frequency modifying or conversion
Patent
1997-08-08
1999-10-26
Urban, Edward F.
Telecommunications
Receiver or analog modulated signal frequency converter
Frequency modifying or conversion
455302, 375332, 329306, 327113, H04B 116
Patent
active
059743069
ABSTRACT:
An image-rejecting receiver comprises a tunable mixer stage, a time-share I-Q mixer stage, a complex filter, and an image rejector. The time-share I-Q mixer stage includes a switch assembly, inphase and quadrature polarity inverters, and a clock generator. The switch assembly generates pulses and distributes them in alternation to the polarity inverters. Performing distribution prior to polarity inversion preserves the orthogonality of the inphase and quadrature target signal components despite pulse-to-pulse bleeding. Charge accumulated at the distributor switch input is dumped between pulses to further minimize such bleeding. A current-mode field-effect-transistor implementation ensures unity gain across each polarity inverter so that they are gain-matched. Gain matching and preservation of orthogonality optimize the conditions for the complex filter to attenuate and for the image rejector to cancel an image signal. The polarity inverters are switched in quadrature to relax polarity-inverter transition timing tolerances, decreasing costs and increasing reliability.
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Hornak Thomas
Knudsen Knud
Hewlett--Packard Company
Urban Edward F.
LandOfFree
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