High power GaN oscillators using field-plated HEMT structure

5 GHz MMIC GaN oscillators based on AlGaN/GaN HEMTs are presented. The use of field-plated HEMT structures in these oscillators resulted in increased output power and dc-to-RF efficiency. An oscillator using an AlGaN/GaN HEMT with 0.5 mm gate width and 1.1 μm field-plate extension, biased at V_ds = 40 V and V_gs = -4.5 V, delivers 1.9 W of output power with a dc-to-RF efficiency of 21.5%. Phase noise was measured to be -132 dBc/Hz at a 1 MHz offset frequency. The oscillator output power density was found to be 3.8 W/mm and is the highest yet reported. Studies of the output power, dc-to-RF efficiency, and phase noise with different field-plate extensions are also presented.