A wide-angle reconfigurable reflectarray antenna (RRA) was designed and experimentally verified utilizing a miniaturized ring patch efficiently controllable with a single bit. Based on the merits of the miniaturization of the radiating element and an elaborate study of the quantization efficiencies of the asymmetric phase differences between the on/off states of the unit cell by optimizing a reference phase on the metasurface, highly directive beam scanning is achieved in a wide ±60˚ range in both the H-and Eplanes. Furthermore, the illumination and spillover efficiencies and focal diameter ratio (F/D) are carefully optimized, resulting in a low profile configuration with F/D=0.36. The fabricated RRA prototype was measured at 9.85 GHz (X-band) with the highest aperture efficiency of 28% and a 1 dB gain bandwidth of 530 MHz, respectively.

The development of biomedical devices benefits patients by offering real-time healthcare. In particular, pacemakers have gained a great deal of attention because they offer opportunities for monitoring the patient’s vitals and biological statics in real time. One of the important factors in realizing real-time body-centric sensing is to establish a robust wireless communication link among the medical devices. In this paper, radio transmission and the optimal characteristics for impedance matching the medical telemetry of an implant are investigated. For radio transmission, an integral coupling formula based on 3D vector far-field patterns was firstly applied to compute the antenna coupling between two antennas placed inside and outside of the body. The formula provides the capability for computing the antenna coupling in the near-field and far-field region. In order to include the effects of human implantation, the far-field pattern was characterized taking into account a sphere enclosing an antenna made of human tissue. Furthermore, the characteristics of impedance matching inside the human body were studied by means of inherent wave impedances of electrical and magnetic dipoles. Here, we demonstrate that the implantation of a magnetic dipole is advantageous because it provides similar impedance characteristics to those of the human body.

This article presents design methods for a transmissive metasurface antenna composed of four layers of meta-structures based on the deep neural network (DNN). Owing to the structural complexity as well as side effects such as couplings among the adjacent meta-structures, the conventional design of metasurface unit cell strongly relies on the researcher’s intuition as well as time-consuming iterative simulations. A design method for a metasurface antenna unit cell with a size of a quarter wavelength operating at a frequency of 5.8GHz is presented. We describe two unique implementations for designing the target metasurfaces: 1) utilizing the inverse network 2) data augmentation by the forward network and a random search algorithm. With the usage of the two DNNs, the average transmittance of the unit cells is improved by about 0.024 than that of the unit cells designed by the conventional approach. This research invokes the application of DNN in designing antennas and other structures operating at radio frequency.

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A hybrid reflectarray antenna (RA) composed of passive and active unit cells that can steer a beam into two selected directions with high aperture efficiencies is designed and experimentally verified. The hybrid RA is implemented by a combination of one-bit active and passive unit cells, which enables the quantization of phase profiles of the reflection coefficients on the antenna surface to 120°. This combination can improve the quantization efficiency of the conventional one-bit reconfigurable RA quantized with 180°. A combination of the passive unit cells of which the phases of reflection coefficients are 180° is determined to be included simultaneously in two quantized phase profiles for two-direction beam steering. As a proof of concept, the hybrid RA is designed to steer the beam to the vertical angles 𝜃 of -18° and 18° on the E-plane. By comparing them with those of the one-bit RA, we confirmed that the aperture efficiencies are improved by 41.85% and 69.41% in simulations and by 37.19% and 60.19% in measurements for the vertical angles 𝜃 of -18° and 18°, respectively.