A low power receiver front-end design with tunable notch filter for tx leakage and blocker suppression

Abstract

An active transmitter self-leakage suppressor for frequency-division duplex transceivers is presented. A wideband active notch filter is implemented at the mixer IF ports to suppress out the transmitter leakage. Since the active notch filter is operating at IF frequencies, its noise, power, and area consumption penalty for the overall transceiver is negligible, and it does not require any complicated amplitude and phase calibration circuitry that is necessary for the cancelers which operate at RF frequencies. Due to the transfer function seen by the active notch-filter, its noise and distortion contribution is shaped and reduced further. The proposed design is implemented in a 65 nm standard CMOS process for an LTE receiver and provides minimum of 5 dB attenuation at duplex distance for E-UTRA band 20. For the same frequency band, it enhances the IIP2 and IIP3 of the receiver with a minimum of 12 and 6 dB, respectively. The active filter consumes only 1.1 mA/channel from a 2.5 V supply and occupies 0.078 mm (2) /channel. Its noise contribution is within the NF measurement error, thus negligible. The design is intended and tested for transmitter self-interference and wideband ACS blockers.