A microstrip low-pass filter (LPF) using reformative stepped impedance resonator (SIR) and defected ground structure (DGS) is proposed in this paper. The proposed filter not only possesses the advantage of high frequency selectivity of SIR hairpin LPF with internal coupling, but also possesses the large stop-band (SB) bandwidth by adjusting the number and area of DGS units. The LPF proposed in this paper possesses the properties of miniaturization, wide SB, high selectivity, and low pass-band ripple (PBR) simultaneously. The characteristic parameters of the proposed LPF is that: the pass-band (PB) is 0~2 GHz, the PBR is 0.5 dB, the SB range is from 2.4 GHz to 9 GHz when the attenuation is under 20 dB, and the maximal attenuation could reach 45 dB in the SB. The size of this proposed LPF is 0.13 $\lambda$ $\times$ 0.09 $\lambda$ ; $\lambda$ is the corresponding wavelength of the upper PB edge frequency of 2 GHz.

In this brief, we propose a logarithmic converter for floating-point numbers based on the piecewise linear (PWL) approximation method. The proposed method is applicable to any customized floating-point format with a mantissa length of 16-23 bits and a maximum absolute error (MAE) larger than 10 ^-6 . The logarithmic function is automatically segmented into several maximal subsections by a software-based segmentation scheme with the restriction of a predefined MAE and a fractional word length for the computing units. Then, we make a tradeoff between the piecewise number and the fractional word length. Based on the results of the segmentor, our design is coded in the Verilog hardware description language. The synthesized results show that our design consumes less area, time, and power without compromising accuracy compared to existing techniques based on the COordinate Rotation Digital Computer (CORDIC) and PWL methods.

The range of the power transmission region can be effectively enlarged by a multiple-transmitter (TXs) and single-receiver (RX) magnetic wireless power transfer (WPT) system. However, the power transfer efficiency (PTE) of the WPT system with two TXs and a single RX has been intensively studied in the past few years. Therefore, a deep analysis of multiple-TX WPT systems needs to be implemented urgently to achieve the highest PTE in a wider range of power transmission. This paper analyzes a general multiple-TX single-RX system in detail based on the circuit model. Two optimal conditions, in which the feeding amplitude ratios need be equal to the mutual inductance ratios and the optimal load should be connected to RX, are derived to obtain the highest PTE. In the experiment part, the feeding amplitude ratios for multiple TXs are implemented by a proposed lumped transformer for the first time. The use of the lumped transformer reduces the complexity compared with the use of multiple inverters to achieve predetermined feeding amplitude ratios. Multiple-TX systems are designed and measured to validate the theoretical analysis. Experimental results agree very well with theoretical calculations.

Three-resonator wireless power transfer (WPT) systems have been proposed to improve the power transfer efficiency (PTE) and power delivered to the load (PDL) in recent years. However, analysis formulas of a three-resonator WPT system are complicated, and the parameters for clarifying the transfer characteristics of this system are difficult to extract. In this paper, concise formulas for analyzing PTE and PDL of the three-resonator system are derived by introducing three factors. Diagram discriminance based on the derived formulas is proposed to obtain the frequency splitting criterions of PTE and PDL in this system. Further, at the transfer distances, where the PTE and PDL are low at original frequency due to frequency splitting phenomenon, the two predetermined-goals of maximizing PTE and PDL are achieved by optimizing coupling strength between the three resonators. The third predetermined-goal of obtaining a constant amount of PDL transfer at maximum PTE is also implemented based on basic algorithms in numerical software. Finally, Simulation and measurement results verify the correctness of analyzing the transfer characteristics of three-resonator WPT system using the presented concise formulas and discriminance. Moreover, effectiveness of realizing the three predetermined-goals via the proposed optimization method is confirmed with experiments.

This paper provides a sound wireless power transfer (WPT) recharging solution for onroad automated guided vehicle (AGV) system. In this solution, multiple transmitting coils serve as power transmitters (TXs), and a receiving coil in AGV serves as a power receiver (RX). The multiple TXs are along a straight track for dynamic charging to AGV. The circuit model of multiple-TX and single-RX WPT system is first constructed based on circuit theory (CT), and then current-optimized scheme based on Lagrangian multiplier method is proposed to tune the currents in multiple TXs to maximize the power delivered to the load (PDL). The equal current (EC Case) flowing through each TX is compared with the optimal current (OC Case). Through contrastive analysis, the OC Case shows its advantages in PDL. Finally, the theoretical analysis results are confirmed by the results of full-wave electromagnetic simulation.

Wireless power transfer (WPT) system with multiple transmitters (TXs) and one receiver (RX) can effectively enlarge the range of power transmission region. The power delivered to load (PDL) and power transfer efficiency (PTE) of two‐TX WPT system has been intensively studied in the past few years. To achieve a wider range of power transmission, the multiple‐TX system should be investigated urgently. Using Kirchhoff's voltage law (KVL) and RX‐side reflected load theory (RLT), this study analyses a general multiple‐TX and single‐RX systems in detail. The explicit closed‐form equations for the highest PDL, PTE and corresponding optimal loads are derived from the two methods. The constraint of feeding amplitude ratios need be equal to the mutual inductance ratios for the highest PTE deduced from KVL; on the other hand, inspired by TX‐side RLT using in the multiple‐RXs system, RX‐side RLT is first proposed and can readily derive the highest PDL, PTE and optimal loads compared with KVL. Numerical simulations for three‐ and four‐TX systems are implemented to intuitively illuminate the theoretical analysis. Experiments for two‐, three‐ and four‐TX systems have verified the accuracy of the proposed analysis.