A channel select filter circuit is disclosed using a current-mode transconductance-capacitor
(gm-C) architecture, which is tuned by digitally controlled capacitor arrays. The
main filter includes at least one transconductor-capacitor (gm-C) filter and a
transresistance amplifier. A replica transconductor-capacitor (gm-C) filter and
a phase detector are used to establish any phase shift in an input signal, and
a state machine adjusts capacitor arrays in the the replica transconductor-capacitor
(gm-C) filter and the at least one transconductor-capacitor (gm-C) filter in order
to set a cut-off frequency of the channel select filter.