Dongping Xiao

Determination and Validation of New Nonlinear FinFET Model Based on Lookup Tables

The Fin field effect transistor (FinFET) is a multiple gate structure, which is recently emerging as a leading structure to continue the scaling of CMOS technology into the nanometer regime. This promising multiple gate structure has not only the advantage of reducing short channel effects but also of being compatible with the conventional planar CMOS technology. To our knowledge, this is the first letter addressing the nonlinear FinFET model validated by large signal network analyzer measurements. Here, we present a nonlinear FinFET model which is based on lookup tables. The accuracy of the developed model is completely and successfully verified through the comparison with nonlinear FinFET measurements

GaN power amplifier design based on artificial neural network modelling

GaN field effect transistors (FETs) have a strong potential for high-power applications. However the RF performance of these devices often experiences limitation due to trapping effects and self-heating. These complicate the development of accurate large-signal models for GaN FETs. To simplify this process, a state-space modelling technique using an artificial neural network (ANN) is used in this work to model the large signal behaviour of the GaN device. In this way, the model is constructed directly from large-signal measurement data collected while the device is in an operating mode close to its application, i.e., class AB power amplifier (PA). To demonstrate the approach, a hybrid power amplifier based on GaN FETs was designed and fabricated. The good agreement between measurements and simulation results verifies the proposed approach. It is the first time that this modelling approach is used in circuit design.

Efficiency Enhancement of Harmonic-Tuned GaN Power Amplifier Using Doherty like Load Modulation

In this paper, the Doherty like load modulation has been implemented in second-harmonic-tuned gallium nitride (GaN) power amplifiers (PAs) to further improve their performance. Both harmonic tuning and load modulation are based on an accurate large-signal model extracted for the GaN devices. Two devices of identical size are used. In previous research works, the use of load modulation on two identical size devices always results in decreases in output power, gain, or even linearity, although improvements in efficiency are shown. Besides that, the influence of the offset line on linearity is not covered. In this experiment, by optimizing the load modulation and properly designing the offset line, a power added efficiency (PAE) of 65%, a linear gain of 16 dB, and an output power of 40.5 dBm have been achieved at 2 GHz. Compared with those of a balanced power amplifier, the load modulated PA shows superior power performance both in efficiency (more than 10% improvement in PAE) and in linearity. Moreover, its output power and gain maintain as high as that of the balanced PA.