Broadband Low-Noise Amplifier Based on Unconventional Matching Networks

This work focuses on designing, fabricating, and testing a broadband low-noise amplifier (LNA) by exploiting dissipative reciprocal matching networks. With reference to a broadband power amplifier, the critical theoretical aspects of the proposed approach have already been presented in a previous publication from the same authors. Herein, the mathematical aspects to extend the applicability of the approach to an LNA are briefly analyzed, and a sample project is discussed in detail. Compared to the cited work, the theoretical impedances needed for the flat-gain condition happen to be more critical in this particular case, imposing the adoption of a more complex base cell, i.e., a cascode pair, and an unconventional output matching network built on a Guanella transformer. The amplifier showed a measured input-output return loss better than 10 dB, a gain of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.5\pm 1.5$ </tex-math></inline-formula> dB, and a noise figure better than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5\pm 0.5$ </tex-math></inline-formula> dB over the subband 4–35 GHz.