Large-Signal MESFET Parameter Extraction Techniques

Much publicity has surrounded the recent introduction of nonlinear microwave CAD tools into the marketplace. However, active device modeling remains as the major limitation of these tools. Furthermore, techniques that characterize nonlinear microwave devices in a systematic, accurate, and repeatable manner still must be developed in order to assure effective and proper use of the new CAD tools. Two techniques that offer the promise of practical device characterization are discussed in this paper. The flrst technique makes use of time-domain signal sampling to "extract" the nonlinear behavior of a device in terms of device model parameters. The second technique d e s use of load-pull measurements. In exploring the two techniques, we have made use of the harmonic-balance program NANA to fit large-signal model parameters to the load-pull and time-domain data. The resulting parameters presumably represent the true large-signal operation of the device under study.