K Band Miniaturized Low-noise Amplifier Design

This paper discusses the total design flow of a K-band LNA . The circuit design, layout design and simulation result are introduced. A novel feedback configuration is presented to achieve the requirement of gain and gain flatness.A K-band LNA based on GaAs HEMT is designed. A structure with three cascaded circuits is used for low noise figure (NF) and high gain. Bias circuits are designed for each stage. Microstrip lines are used for matching networks. Input and output ports are both matched to 50Ω.To improve the circuit's performance, a feedback network is experimented to obtain a better gain flatness and a enough gain, and a novel feedback topology is presented. A feedback network consisting of a resistance and a capacitance in series is added at the second and third stage's sources, the first stage as the same as the conventional method. Finally, the layout is optimized for best simulation result.As a result, the K-band LNA achieved a low noise figure of less than 2 dB,a high small signal gain of over 30 dB, a good gain flatness of less than±1 dB, as well as good input VSWR and output VSWR of less than 1.5 from 19.5 to 21.5 GHz, The simulation results indicate that the circuit satisfies the design demands.