Characterization and modeling of intermodulation distortion asymmetry in HBT using large-signal model

Asymmetrical behaviors of intermodulation distortion (IMD) in microwave active devices are often observed when the terminating impedance at baseband frequency contains a reactive component. This phenomenon sometimes induces misunderstanding of distortion performance unless the baseband impedance effects are properly accounted for. The distortion asymmetry appears in not only small-signal regime but also large-signal regime. Therefore, a unified approach which can predict IMD asymmetry over a broad range of output power levels is in critical demand. In this context, the usefulness of nonlinear large-signal model is addressed when predicting IMD asymmetries. Extensive measurement results are compared to simulation results to demonstrate the usefulness. Moreover, the origin of distortion asymmetry is discussed with time-domain envelope simulation.