Co-Designed Quasi-Reflectionless Low-Noise Amplifier With Bandpass Filter and RF Switching Functionalities

Abstract

In this letter, a reflectionless low-noise amplifier (LNA) filter (RLNAF) is presented, incorporating four distinct functions: 1) filtering; 2) reflection cancellation; 3) low-noise amplification; and 4) RF switching within a single component. It is comprised of a transmissive path and two absorptive paths. Specifically, a complex-termination methodology is applied to the transmissive path incorporating a bandpass filter (BPF) and LNA functionalities, removing the need for additional interstage matching networks (MNs). The absorptive paths are composed of a bandstop filter terminated with a loading resistor in one port to selectively dissipate the out-of-band reflected RF signals. Moreover, switch-off functionality is demonstrated by reconfiguring the bias of the transistor. For proof-of-concept validation purposes, two RLNAF prototypes are designed, manufactured, and measured at C-band. The RF characteristics are given as follows: RLNAF I: $f_{cen} = 4.65$ GHz, gain = 15.8 dB, noise figure (NF) = 2.07 dB, and quasi-reflectionless characteristics better than 10 dB from DC to 4.27 and 4.34 GHz to 6.42 GHz and at least 9.8 dB from 4.27 to 4.34 GHz; RLNAF II: $f_{cen} = 3.7$ GHz, gain = 15.3 dB, NF = 1.09 dB, and quasi-reflectionless characteristics better than 10 dB from DC to 4.75 and 5.75 GHz to 7.03 GHz and at least 6 dB from 4.75 to 5.75 GHz.