K‐band frequency‐selective limiter using an injection locked oscillator for blocker cancellation

Abstract

A frequency-selective limiter (FSL) using an injection locked oscillator (ILO) is proposed for a blocker cancellation, which employs an ILO in the feedforward path as a high-Q notch filter to select and amplify the blocker from the input signal. The ILO also functions as a phase shifter providing a proper phase delay so that two blockers in the feedforward and thru paths cancel each other out in the combining node. The proposed FSL is fabricated in a commercial 0.15 μm GaAs pHEMT process with a maximum blocker suppression of 27 dB in the 50 MHz spacing two-tone measurement at the K-band. Thus, it provides a blocker suppression higher than 20 dB over the 250 MHz blocker bandwidth.