A Large-Signal Behavioural Modeling Approach of GaN HEMTs for Power Amplifier Design

A new method to simulate the large-signal behaviour of GaN HEMTs is presented along with the two 15W X-band MMIC Class AB power amplifier (PA) designs using the same methodology. Proposed modeling approach is based on curve-fitting transistor performance parameters in the load impedance plane, while transistor's behaviour in the source impedance space is calculated using a virtual source-pull technique. Good agreement with the results of two fabricated GaN PA MMICs demonstrate the accuracy of the method in simulating P-out, G(t) and PAE of the amplifiers at any given compression level. This approach is distinguished from conventional modeling methods with its minimal measurement requirements, ease of model development, and generic nature while accurately predicting the large-signal response, thus is suitable to use for PA design, under the lack of a more comprehensive transistor model.