A system for tuning a radio-frequency signal includes a first input path,
a second input path, a common reference generator, a selector, a mixer,
and a filter. The first input path and the second input path propagate a
first single-ended input signal and a second single-ended input signal,
respectively, to the selector. The selector converts the first
single-ended input signal and the second single-ended input signal into a
first differential input signal and a second differential input signal,
respectively, using a reference signal generated by the common reference
generator.
The selector selectively couples one of the first and the second input
path to an input of the mixer. The mixer downconverts a selected on of
the differential input signals received from the selector. The filter
attenuates a portion of the downconverted input signal outside a passband
associated with the filter.