Numerical simulation and measurement of Gunn device dynamic microwave characteristics

Important characteristics of Gunn devices such as output power, efficiency, and stability are determined by the large-signal dynamic admittance of these devices. Previous attempts to correlate theoretical and measured values in absolute terms for this parameter have met with limited success due to modeling approximations and numerical simulation problems. An improved, implicit numerical simulation scheme has been devised that requires fewer approximations, that gives higher accuracy results with less computational time, and that encounters fewer problems of simulation convergence. For a 10-µm-long GaAs device operating at 10 GHz at a 10-V dc bias, this numerical model predicted results agreeing well with the measured results of device negative conductance that fell from -4.64 to-2.46 mΩ and device capacitance that decreased from 0.701 to 0.691 pF as the RF voltage amplitude increased from 7.72 to 8.71 V. The observed results agreed with the theoretical values to within 6 percent for the negative conductance and to within 15 percent for the device capacitance and represent the best agreement yet achieved between a first principles theoretical model and actual data taken on an oscillating device.