Nonlinear coupled transmission line analysis for second harmonic generation in traveling-wave GaAs MESFET´s

A coupled nonlinear transmission line analysis for second harmonic generation from a traveling-wave field-effect transistor is presented. In the formulation, three main nonlinearities, namely the Schottky-barrier capacitance, the transconductance and the draincon-ductance, are considered. The coupled nonlinear differential equations are solved under a weak-coupling approximation with the help of the Weierstrassian elliptical function. It is observed that the second harmonic gain is significant after (where is the transverse length of the transistor). After this value of x, the amplitude at second-harmonic level increases sharply and follows almost a square-law behavior. It is found that the output drain conductance emerges as a large contributor to harmonic generation. The possibility of an image gate as drain conductivity modulator or phase velocity synchronizer is proposed. It is confirmed that travelling-wave MESFET\´s can also be used as harmonic generators.