Power-amplifier design using negative-image device models

Abstract

points on the PSTD grids over whole domain will be needed for PSTD updating, including those in the FEM region (updated from the FEM results) and inside scatter (where the E-field vanishes). NUMERICAL EXPERIMENTS AND DISCUSSIONSFor purposes of demonstration, a 6-cm-diameter metallic-cylinder scatterer embedded in a free-space medium is adopted. The Gaussian excitation has a carrier frequency of 5 GHz, t o ϭ 480 ps and ϭ 160 ps. For fruitful comparison, the grid resolution for FDTD is selected as dx ϭ 3 mm, whereas the PSTD is taken as 5 dx. The time step is chosen as 1 ps for the central-difference algorithm as well as for Newmark method for easy comparison. With dx selected, the FEM will result in 691 elements. The computational domain is truncated using the 8-layer UPML, with each layer being dx thick. Figure 3 shows a comparison of the FEM-FDTD, PSTD, and MIE series, and the TDFEM-PSTD algorithm, whereas Table 1 depicts a comparison of the computational time taken for all these methods. From the figure, we notice that PSTD suffers severely from its inability to model curvilinear boundary. In comparison with FEM-FDTD, similar accuracy is obtained by our proposed algorithm. From the table, our proposed algorithm outperforms the FEM-FDTD method in terms of the CPU time taken. As compared to FEM-FDTD, fewer cells are needed for our algorithm. Figure 4 shows the results of two different source-introducing methods. One approach is to apply the Dirichlet boundary condition on the FEM boundary as a source, the other one is to use the boundary integral in Eq. (3). As we can see, the former will result in a late-time effect, and the latter one has better stability. CONCLUSIONIn conclusion, an efficient and stable hybrid TDFEM-PSTD method has been proposed. The proposed TDFEM-PSTD was found to be more robust and efficient than FEM-FDTD and PSTD. The proposed algorithm consumes a lower number of cells than the FEM-FDTD method and is more accurate than the PSTD method. Increasing demand and market trends for high-power amplifiers require designers to obtain optimum performance from power devices, and predict obtainable circuit performance in the beginning stage of a circuit design. A traditional key requirement for power amplifiers is to extract maximum output power with high efficiency from power devices. With the development of multicarrier communication systems, nonlinear characteristics of power amplifiers are becoming more critical parameters in the evaluation of power amplifiers. Since the power amplifier is one of the most critical components with regard to system performance and cost, engineers are increasingly challenged to extract optimal performance from cost-competitive devices [1]. Several techniques have been developed in the past to aid in building wireless power amplifiers with required performance. In [2,3], a load-line method for power transistors has been introduced to determine optimum load resistance for maximum output power. When used with small-signal-device equivalent circuits, the method is gener...

Design of class-E power amplifier for zero-current switching operation with MOSFET nonlinear output parasitic capacitance

“…The main key issue to improve the overall efficiency of the modern microwave system is the efficiency of the power amplifiers . High‐power conversion efficiency and high operating frequency are the most important figure of merits for evaluating of the power amplifier . The switch‐mode operation is an efficient technique to obtain the high‐efficiency performance at high operating frequency that the transistor is assumed to act like a short circuit and an open circuit for the on‐state and off‐state, respectively.…”