Analysis and Design of a 6-18 GHz Multi-Stage Wideband GaN LNA with 16.5 dBm OP1dB and over 42 dBm Survivability

A 6-18 GHz multi-stage wideband Gallium Nitride (GaN) Low Noise Amplifier (LNA) with high linearity and high robustness is presented. A feedback amplifier circuit with gain enhancement and reactive impedance matching networks can compensate for transistors gain roll-off with frequency to achieve a better gain-flatness and extend overall bandwidth. The feedback values are chosen different for each stage by optimizing the frequency response of each unit cell to obtain low noise, good return loss, high gain and high linearity simultaneously. The 1-dB compression point output power (OP1dB) contours and Gp circles are drawn on the same load impedance complex plane to identify optimum impedance for the last stage. The LNA in 0.25 µm GaN pHEMT process achieves 2-2.7 dB noise figure (NF), 25.4 dB average gain with ±1.3 dB gain-flatness, 10.5 dB input return loss and 12 dB output return loss. The LNA exhibits OP1dB of 16.5 dBm, output third-order intercept point (OIP3) of 30 dBm and robustness up to 42 dBm input power level, showing the strong potential for radar and electronic warfare (EW) applications.