Multi-functional RF Filter with Co-Designed Low Noise Amplifier and RF Switching Capabilities

This paper presents a co-designed RF bandpass filter and low-noise amplifier (BPF-LNA) with quasi-elliptic transfer function and RF switching capabilities for sub-6 GHz communications. The BPF-LNA concept is based on complex-matched bandpass filtering matching networks (BPF-MN) that directly match the transistor impedances while at the same time achieving bandpass filtering; thus, eliminating the need for RF filters in the RF front-end. Frequency-dependent inter-resonator coupling elements are used in the BPF-MN to enhance the transfer function selectivity by means of transmission zeros (TZs). The concept has been validated at C-band through the design, manufacturing and testing of a BPF-LNA with fcen of 4.63 GHz, noise figure (NF) of 2.52 dB and one TZ at the lower side of the passband and a BPF-LNA with two symmetrically-allocated TZs and NF of 2.26 dB. By removing the DC biasing, the BPF-LNAs can be intrinsically switched-off with an isolation > 25 dB within an ultra-broad range.