A novel quasi-Yagi antenna is proposed for millimeter-wave (mmWave) 5G cellular handsets operating in the 28-GHz band. The proposed antenna is designed to be compact through modification of the planar folded dipole topology so that it can be mounted inside a compact mobile terminal. A vertically stacked structure utilizing a multi-layer printed circuit board (PCB) and via holes is applied to the antenna topology to minimize the antenna lateral width while maintaining the characteristics of the planar folded dipole antenna. A single antenna yields a -10-dB bandwidth for a return loss of 12.3 % (26.3 to 29.75 GHz) and a gain of 5.51 dBi at 28 GHz. The change in beam patterns due to the chassis effect when 4-element linear arrays are inserted into the upper and side edge inside the terminal is analyzed.

In this letter, the microwave power transfer (MPT) system with the optimal number of rectenna arrays for mid-range applications is proposed, theoretically analyzed, and verified. Retrodirective power transmitter is designed to overcome the degradation by the near-field effect and enhance the power transfer efficiency. The implemented transmitter is composed of 16 × 1 patch antennas with a $\lambda$/2 spacing and each of the antennas has a circuit for simultaneously detecting and shifting the phase, and operates at a frequency of 2.45 GHz. To further improve the power transfer efficiency, the parallel dc combining rectenna array is designed since conventional RF combining rectenna has several problems in the case of mid-range. The fabricated rectenna array consists of 8 × 1 rectennas with a $\lambda$/2 spacing and a dc power management circuit. In addition, the optimal number of rectenna arrays is proposed, considering the size of the receiver. In the experiments, the optimal number of rectennas is 3 when the transfer distance is 1 m. The achieved power transfer efficiency from 3-arrayed rectennas is 4.47%, while the efficiency of 5.01% is achieved from 8-arrayed rectennas. Experimental results from the implemented MPT system show good agreement with the proposed theory.

This paper proposes a pattern reconfigurable high gain spherical dielectric resonator antenna (DRA) operating on higher-order mode. Two microstrip patches were used to excite TE301 mode in the different direction. A reconfigurable switch network was designed and it has three switching modes for selecting each patch alone or selecting them simultaneously. The proposed antenna can reconfigure its radiation pattern by using a feeding structure which is consist of two microstrip patches and the reconfigurable switch network. A prototype antenna operating on TE301 mode at 5.8GHz was fabricated by ceramic material. By experiment, we validated the new concept of pattern reconfigurable spherical DRA.

Using a current-controlled loop with a loaded capacitance, we experimentally demonstrated distance-insensitive wireless power transfer (WPT) and near-field communication (NFC) without additional tuning network and algorithms. The proposed loop can achieve the uniform mutual inductance within the operating distance by controlling the ratio of the current flowing through the forward and reverse loops according to the loaded capacitance. By reducing the impedance mismatch within the operating distance ranging from 0 to 7 cm, the proposed loop can provide the transfer efficiency over approximately 60% for WPT and a stable channel bandwidth for NFC operating modes. In particular, when the receiving antenna is close proximity to the transmitting antenna, the transfer efficiency of the proposed loop is up to nearly six times higher than that of conventional loop.

In this paper, a coupler integrated microstrip patch linear phased array is proposed as a new self-calibration system. The proposed coupler placed along the edge of the microstrip patch antenna is weakly coupled to the antenna array. This allows self-calibration without affecting the radiation performance of the antenna array. A 1x4 coupler integrated patch linear phased array and a beamformer operating at 5.8 GHz were implemented to verify the new self-calibration system. The measurement result using the self-calibration is very close to the result with a vector network analyzer. The coupler integrated patch linear phased array proposed as a new self-calibration system has 0.22dB RMSE(root mean square error) magnitude and 1.2 RMSE phase. The calibration method using a proposed antenna array is expected to on-site calibration.