Circuit Techniques for Enhanced Channel Selectivity in Passive Mixer-First Receivers

Two techniques are proposed to enhance channel selectivity in passive-mixer first receivers. Positive capacitive feedback and/or a shunting notch provides steeper baseband, and thus RF, impedance roll-off and improved adjacent-channel linearity. The receiver operates at RF frequencies from 2-11GHz and achieves a blocker PldB compression of +1.8dBm and IIP3 of +20dBm for a blocker frequency-offset of 70MHz (BBBW=30MHz) at f
_RF
=5GHz. The NF ranges from 9±ldB to 11±ldB over the frequency range of f
_RF
=2-8GHz. The chip has been fabricated in a 130nm SiGe BiCMOS technology.