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In monolithic integration of cable-modem RF tuners a double-conversion receiver architecture is used. In this paper we present a prototype design of an upconverter and a downconverter unit. The upconverter upconverts a channel from 47-862 MHz input band to around 1575 MHz intermediate frequency. The image-reject downconverter shifts the channel to 36.125 MH.. (EU) or to 43.75 MHZ (' US). The upconverter includes a variable-gain low-noise amplijier, a double-balanced mixer, a three-stage VCO bank for LO generation and a divide-by-two circuit for driving an external PLL. The downconverter includes a LNA, image-reject mixers in Hartley conJguration, a 3-stage polyphaseJlter, an IFamplijier and a SAW driver. For LO generation the circuit includes a 6-GHz on-chip VCO, a divide-by-four circuit for quadrature LO and a divide-by-1 6 for feeding an external PLL. Signal reversal switching in the LO buffer can be used for the selection of LSB/USB injection. All building blocks are presented in this paper and experimental results are given from the upconverter, downconverter, ' and RF tuner demonstrator including SA W filters with center frequencies at 1575 M H . and 44 MHz. The circuits are fabricated in a 0 . 9 -p SiGe bipolar process.

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