GaN-Based Low Noise Flat Gain Amplifier for X-Band Applications

This paper describes the design of a low noise amplifier (LNA) monolithic microwave integrated circuit based on GaN-on-SiC technology. The amplifier operates in the frequency range of 9.5 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-11.5\ \text{GHz}$</tex>. The design topology and careful choice of HEMTs ensure high gain and low output power at 1-dB compression point <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathbf{P}_{1\text{dB}}). \mathbf{P}_{1\text{dB}}$</tex> and saturated output power <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathbf{P}_{\mathbf{sat}})$</tex> have a direct relation with each other. The low <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{P}_{\text{sat}}$</tex> feature is desired to safely integrate GaN LNAs with subsequent circuitry in the radar receiver systems. The proposed LNA consists of two stages, having 300 μm periphery at the first stage and 200 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu\mathbf{m}$</tex> periphery at the second stage. The low periphery device provides better gain, lower output power, and hence lower <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{P}_{1}\text{dB}$</tex>. The amplifier provides a gain of 20.9 dB with +/- 0.2 dB gain ripple. Its input and output reflection coefficients are better than -9.6 dB and -11 dB, respectively. The overall chip size is 2.9 mm x 1.5 mm.