S-band GaN based low noise MMIC amplifier design and characterization

Abstract

Low Noise Amplifiers (LNA) are widely preferred components in receiver frontend modules. The received signal level is generally very low and amplifying it without adding too much noise is very crucial in communication systems. In this thesis study design, fabrication and test of three Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) based Monolithic Microwave Circuit (MMIC) LNAs are presented. Inductive source feedback topology is used to obtain both better input return loss and noise figure. All three designs achieve higher than 20 dB gain, better than 10 dB input return loss and their noise figure values are 2 dB, 1.5 dB and 1 dB in S-band. High resistive gate biasing is utilized at third design to increase input power handling. Size reduction is very important in MMIC technology. The first design is 3 x 5 mm and the second design is 2 x 3.5 mm, % 46 size reduction is achieved. In GaN technology controlling SiN layer thickness is very problematic and this fabrication step affects capacitor values. The second and third LNA designs presented in this research, matching circuitries and implicitly overall characteristics are not in uenced too much by a change of capacitor values. Targeted bandwidth is 2.7-3.5 GHz, achieved frequency range is 1.5 GHz (from 2.5 GHz to 4 GHz). The three LNA designs have 28.1 dBm, 33.4 dBm, and 35.9 dBm output third-order intercept point respectively. Output powers at 1-dB compression points are 18.2 dBm, 23.4 dBm and 25.9 dBm. For all three LNA designs, group delay is less than 0.3 nanoseconds.