X-band CPW high power amplifier design by GAN based MMIC technology

Abstract

The developments in defense industry, telecommunication and satellite systems have gradually increased the necessities for the small and compact Power Ampli- fiers (PAs) with high output powers and gains. Monolithic Microwave Integrated Circuits (MMICs), that are fabricated by using Gallium Nitride (GaN) on Silicon Carbide (SiC) substrate, achieve the system requirements. GaN based MMIC technology gives chance to produce high power capable and compact PAs. Moreover, suitable Wilkinson Power Dividers (WPDs) with low Insertion Loss (IL) assist in transferring output power of the device with combining MMIC PAs. Presented designs in this thesis work have been fabricated in Bilkent University NANOTAM with GaN on SiC process. Fabricated X-band Coplanar Waveguide (CPW) PA works from 7.9 GHz to 8.4 GHz as intended and its efficiency equals to 40 % at 8.4 GHz under 2.1 dB compression. Measurements of fabricated PA show that output power of the device is equal to 37.8 dBm under 2.1 dB compression and it has 9.8 dB minimum gain in the operating band. Furthermore, equal, three-way WPD device was designed and fabricated with the same process and it works at wide-band range with approximately 0.9 dB IL. It is advantageous that the total dimension of paralleled MMIC PAs can be adjusted by scaling branches of the designed WPD with the aim of performance optimization.