An integrated receiver with channel selection and image rejection
substantially implemented on a single CMOS integrated circuit is
described. A receiver front end provides programable attenuation and a
programable gain low noise amplifier. Frequency conversion circuitry
advantageously uses LC filters integrated onto the substrate in
conjunction with image reject mixers to provide sufficient image frequency
rejection. Filter tuning and inductor Q compensation over temperature are
performed on chip. The filters utilize multi track spiral inductors. The
filters are tuned using local oscillators to tune a substitute filter, and
frequency scaling during filter component values to those of the filter
being tuned. In conjunction with filtering, frequency planning provides
additional image rejection. The advantageous choice of local oscillator
signal generation methods on chip is by PLL out of band local oscillation
and by direct synthesis for in band local oscillator. The VCOs in the PLLs
are centered using a control circuit to center the tuning capacitance
range. A differential crystal oscillator is advantageously used as a
frequency reference. Differential signal transmission is advantageously
used throughout the receiver.
