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Modified current model has been developed to more accurately model the current-voltage characteristics of GaAs pHEMTs over a wide range of temperature. In particular, the modeling accuracy of knee, saturation and subthreshold regions has been greatly improved. These results are achieved by introducing the polynomial expression on the bias conditions. The verification is performed by fabricated pHEMTs at different temperature. Good agreement is obtained. [ABSTRACT FROM AUTHOR]

One of the most critical hardware components for the performance of the Ground-Penetrating Radar (GPR) system is the antenna and the resistive loaded antenna is one of common antennas used in the GPR system. The authors extend the Wu-King linear current distribution to the double exponential current distribution, modify the inaccurate part of the Wu-King loading profile and deduce an improved resistive loading profile with high efficiency. The broadband performance of the improved resistive loading profile has been studied; the concept of lengthening coefficient is created and the optimum parameter designing curve of the antenna is provided. Numerical calculation shows that the maximum bandwidth and efficiency of antenna can be achieved with the improved loading profile simultaneously. The impedance bandwidth is as high as 40:1, which is much greater than the 3:1 bandwidth of Wu-King distribution when the voltage standing wave ratio is below 3. It exhibits better efficiency and bandwidth than Wu-King loading profile. The loading profile can reduce the late-time ringing, enhance the pulse radiation characteristics and be widely applied to other resistive loading antenna for GPR applications. [ABSTRACT FROM AUTHOR]