This paper proposes a low-distortion sine wave generator using logic circuits and relatively simple analog filter for analog device testing. Our proposed circuit cancels 3rd-order harmonic distortion (HD3) and 5th-order harmonic distortion (HD5) by summing multiple rectangular waveforms of fundamental and higher frequencies. These rectangular waves are generated by appropriately dividing the rectangular wave from a digital automatic test equipment (ATE). The other higher order odd harmonics are removed by the following simple analog low-pass filter (LPF). We have implemented its prototype whose measurement results show the generation of a sine wave with harmonics of less than -95dBc.

Based on an auxiliary differential equation (ADE) and new weighted Laguerre polynomials (WLPs), an efficient 3-D finite-difference time-domain method (FDTD) with factorized-splitting (FS) scheme is proposed to calculate wave propagation in general dispersive materials. The ADE technique is introduced to model general dispersive materials. Using a new temporal basis, the new WLPs can improve computational efficiency and save computing resources. The FS scheme is used to efficiently solve the huge sparse matrix equation. A numerical example is given to verify the accuracy and the efficiency of the proposed method. The results show its superiority compared with existing methods.

In the traditional digital finite impulse response (FIR) filter design, there exist some limitations. For instance, unwanted signals cannot be filtered out by using these FIR filters. Therefore, to break these limitations, this paper proposes an optimization method for designing digital FIR filters based on the back propagation neural network (BPNN) algorithm. Firstly, an amplitude response model has been established based on the linear properties of the digital FIR filters. Then, the BPNN algorithm has been used to minimize the estimation error between the ideal and the actual amplitude response such that the optimal coefficients of the digital FIR filter can be obtained. Finally, several design examples are used to verify the performance of our proposed optimal design based on BPNN. The simulation results show that, compared with the optimal designs based on the sequential and rectangular window, our proposed optimal design based on BPNN can achieve better filtering effectiveness but at the cost of larger computational complexity.

Wireless power transfer technology is installed in various devices such as smartphones and smart watches. The misalignment of devices and the increase in the number of dedicated chargers pose problems in terms of convenience and the room landscape. In this letter, we propose a parabolic spiral coil transmitter with a uniform magnetic field that is robust against misalignment and can charge multiple devices at the same time with one transmitter coil. The verification results show that the coefficients of variations of the magnetic flux density of the conventional transmitter and the proposed transmitter are 0.380 and 0.245, respectively, indicating that the proposed transmitter has a small magnetic field fluctuation.

Traditional double-loop PI control strategy (DLPI) is adopted in PMSG system, which has slow response speed and complex parameter design. In this paper, an improved single-loop model predictive control strategy (SLMPC) is proposed for PMSG system, which improves system response speed, and reduces parameter design difficulty. Two improvements are as follows. First, a single-loop control structure is established based on the deduced second-order speed model, which simplifies cascaded double-loop control structure and improves system transient performance. Second, an integral and differential discretization method is adopted to simplify design difficulty for FCS-MPC without measuring dT_m/dt and tracking d²ω_r/dt². Finally, simulation and experiment are carried out to verify the proposed strategy.