Investigation of IMD asymmetry in microwave FETs via Volterra series

IMD asymmetry generation and its asymmetrical behaviour are discussed and clarified in this contribution using a Volterra series approach. The approach has been applied to a power PHEMT device for X-band application. The effects of harmonic terminations have been clarified, stressing the relevance of baseband terminations and in particular of the output susceptance. Simplified expressions are inferred to clarify the effects of output terminations. Finally, the opportunity to choose a suitable fundamental and second harmonic output termination to reduce intermodulation asymmetry is discussed.