This paper presents a novel technique for high efficiency and compact size wireless power transfer (WPT) systems. These systems are based on coupled defected ground structure (DGS) resonators. Two types of DGSs (H-shape and semi-H-shape) are proposed. The semi-H-shaped DGS realizes larger inductance value, and this results in higher WPT efficiency. Instead of using an inductive-fed resonant coupling, we propose capacitive-fed resonant coupling, which reduces the design complexity and enhances the efficiency further. The DGS resonator of both the systems is loaded by chip capacitors for miniaturization. An equivalent circuit using approximate quasi-static modeling is extracted. An analytical design procedure is developed to calculate the optimum design parameters for the proposed WPT systems. The optimized structures are fabricated and measured. The simulation and measurement results are in good agreement. The proposed semi-H-shaped DGS WPT system has a peak efficiency of 73% at a transmission distance of 25 mm. In turn, the figure of merit becomes the highest among the WPT systems proposed so far.

Conventional resonant inductive coupling wireless power transfer (WPT) systems encounter performance degradation while energizing biomedical implants. This degradation results from the dielectric and conductive characteristics of the tissue, which cause increased radiation and conduction losses, respectively. Moreover, the proximity of a resonator to the high permittivity tissue causes a change in its operating frequency if misalignment occurs. In this report, we propose a metamaterial inspired geometry with near-zero permeability property to overcome these mentioned problems. This metamaterial inspired geometry is stacked split ring resonator metamaterial fed by a driving inductive loop and acts as a WPT transmitter for an in-tissue implanted WPT receiver. The presented demonstrations have confirmed that the proposed metamaterial inspired WPT system outperforms the conventional one. Also, the resonance frequency of the proposed metamaterial inspired TX is negligibly affected by the tissue characteristics, which is of great interest from the design and operation prospects. Furthermore, the proposed WPT system can be used with more than twice the input power of the conventional one while complying with the safety regulations of electromagnetic waves exposure.

In this letter, we propose a compact size, small insertion loss 60 GHz on-chip H-shaped resonator bandpass filter (BPF) using 0.18 μm standard CMOS technology. The BPF Size is miniaturized by loading the H-shaped resonator with metal-insulator-metal capacitors at its ends. Besides, two defected ground structure cells are etched under the coupled lines to improve the filter insertion loss. Furthermore, selectivity is enhanced by loading the center of the H-shaped resonator with two unsymmetrical meander line stubs generating two transmission zeroes at 50 and 70 GHz. The fabricated BPF chip size is 240 × 650 μm ² . The measured insertion loss and fractional bandwidth are 2.5 dB at 60 GHz and 21%, respectively.

This brief proposes a design methodology based on the admittance (J-) inverters for a dual-band wireless power transfer (WPT) system that employs two cascaded circulars defected ground structure (DGS) resonators with different capacitive loading to guarantee distinct resonances. A single microstrip line excites the two DGSs, and when two DGS resonators are coupled back to back, it transforms to a dual band pass filter leading to WPT at both bands. Each of the DGS resonators has independent coupling. Thus, the realized J-Inverters are designed independently. Also, we employ a single stub for the matching. This stub appears with a different length according to the operating frequency; hence, an independent external coupling is achieved at both frequencies. A compact size of 30 mm × 15 mm is fabricated achieving a WPT efficiency of more than 71% at a power transfer distance of 16 mm for both bands (0.3 and 0.7 GHz).

This letter presents a 60-GHz ultracompact on-chip bandpass filter (BPF). The designed filter is based on a unique structure, which consists of two overlapped broadside-coupled open-loop resonators, achieving a high level of miniaturization. Moreover, each resonator is loaded by a metal-insulator-metal capacitor to get further miniaturization. Defected ground structure pattern is constructed under the filter structure to enhance the insertion loss (IL). This BPF is designed and fabricated using a standard 0.18-μm complementary metal-oxide-semiconductor technology for millimeter-wave applications. The fabricated BPF chip size is 240 × 225 μm ² including pads. The measured results agree well with the simulation ones and show that the BPF has an IL of 3.3 dB at 59.5-GHz center frequency, and a bandwidth of 12.9 GHz.

This paper presents a high-efficiency CMOS rectifier based on an improved dynamic threshold reduction technique (DTR). The proposed DTR consists of a clamper circuit that biases the gates of pMOS diode switches through a capacitor and diode-connected pMOS transistor. The clamper is used to insert a negative dc level to the input RF signal; therefore, more negative RF signal can be obtained to bias the gates of the main rectifying pMOS devices during its conduction phase. This mechanism reduces the threshold voltage of the main pMOS transistors and increases their sensitivity to the RF input signal. The proposed rectifier is implemented in a 0.18-μm CMOS technology and tested. The measurement shows a peak power conversion efficiency of 86% and an output voltage of 0.52 V at an input power of -16.5 dBm and an input frequency of 402 MHz. The core area of chip excluding measurement pads is 0.024 mm ² .