In this paper, a rotman lens of multi-beam feed that can be applied to a car collision avoidance radar is designed using nonradiative dielectric (NRD) guide appropriate to the millimeter wave frequency. For the optimum condition, NRD guide at the transmission lines of input and output ports is designed to obtain low loss, small coupling between the transmission lines, and dominant mode operation. The rotman lens is also optimized so as to minimize sidelobe of array factor. To prevent beam pattern from being distorted, multiple-reflection from sidewall has been eliminated by corrugated sidewall.

In this paper, a compact controlled reception pattern antenna (CRPA) array based on a mu-zero resonance (MZR) antenna is proposed for a global positioning system (GPS). The MZR antenna can be minimized by designing structure based in mu-negative (MNG) transmission line. The MNG transmission line can be implemented by a gap structure for the series capacitance and a shorting via for a short-ended boundary condition. The CRPA array, which operates in L1 (1.57542GHz) and L2 (1.2276GHz) bands, is designed as a cylinder with a diameter and a height of 127mm (5 inches) and 20mm, respectively, and is composed of seven radiating elements. To design the compact CRPA array with high performance attributes such as an impedance matching (VSWR) value of less than 2, an isolation between array elements (<-12dB), an axial ratio (<5dB), and a circular polarization (CP) gain (>-1dBic: L1 band and >-3dBic: L2 band), we employ two orthogonal MZR antennas, a superstrate, and chip couplers. The performances of the CRPA antenna are verified and compared by an analytic analysis, a full-wave simulation, and measurements.

This paper presents a meta-structured circular polarized array antenna with wide scan angle. In order to widen the scanning angle of array antennas, this paper investigates unit antenna beamwidth and the coupling effects between array elements, both of which directly affect the steering performance. As a result, the optimal array distance, the mode configuration, and the antenna structure are elucidated. By using the features of the miniaturized mu-zero resonance (MZR) antenna, it is possible to design the antenna at optimum array distance for wide beamwidth. In addition, by modifying via position and gap configuration of the antenna, it is possible to optimize the mode configuration for optimal isolation. Finally, the 3dB steerable angle of 66° is successfully demonstrated using a 1x8 MZR CP antenna array without any additional decoupling structure. The measured beam patterns at a scan angle of 0°, 22°, 44°, and 66°agree well with the simulated beam patterns.

A penta-band antenna based on the mu-negative transmission line is presented for radio frequency (RF) energy harvesting application. The antenna utilizes five radiation modes; two quarter wavelength resonances, three quarter wavelength resonance, zeroth order resonance, and first order resonance. The parasitic radiating strip antenna generates quarter wavelength resonance radiation. The dual band antenna based on two unit cell mu-negative (MNG) transmission line gives birth to the zeroth order resonance (ZOR) mode and the first order resonance (FOR) mode. The parasitic radiating strip and dual band antenna based on two unit mu-negative (MNG) transmission line are magnetically coupled by a feed monopole with gap. This feed monopole, simultaneously, radiates at quarter and three quarter wavelength resonance frequency to cover the other bands. The multi-mode coupling mechanism of this penta-band antenna is well modeled by our derived equivalent circuit. The measured radiation efficiencies are more than 87% over the entire penta-band.

This paper presents a low profile high-efficiency transmitarray (TA) antenna based on a hybrid frequency selective surface (FSS). The hybrid FSS consists of two types of unit cells that have different incident angles and TE/TM polarization. This design minimizes the performance degradation caused by the oblique incident angle when designing a low profile TA antenna. In addition, the set of transmission phases to minimize transmission loss is selected by employing the optimal output phase reference. To verify its feasibility, a low profile TA (focal length/diameter of FSS =0.24) antenna that employs a unit patch antenna with a low gain and wide beamwidth as a feed antenna without an additional structure is designed. The simulated and measured results are in good agreement. In particular, the high simulated and measured aperture efficiencies of 42.7% and 41.9%, respectively, are obtained at 10GHz, respectively.

In this paper, we present the effects of finite superstrates and asymmetrical grounds on the performance of high gain superstrate antennas. First, when the source of a superstrate antenna is located at an edge of a ground plane, that is, an asymmetric ground plane, the gain of the superstrate antenna can be made to match the gain of the superstrate antenna with a symmetrical ground plane using the PEC (E-plane asymmetric) or the AMC wall (H-plane asymmetric) near the edge. Second, the gain of the superstrate antenna, which has a ground plane with dimensions sufficiently close to infinite, is found to be roughly proportional to the reflection magnitude of a partially reflective surface (PRS). It is found that when the square ground size has a finite dimension of two wavelengths or less, the reflection magnitude of the PRS should have the optimum value for achieving maximum gain. Finally, the gain of the superstrate antenna is studied when the ground plane differs from a PRS. For the above three cases, the performances of the superstrate antenna are verified and compared by analysis, full-wave simulation, and measurement.

This paper presents a capacitor-loaded 4x4 planar loop array for three-dimensional near-field beamforming of magnetic resonance wireless power transfer (WPT). This planar loop array provides three important functions: beamforming, selective power transfer, and the ability to work alignment free with the receiver. These functions are realized by adjusting the capacitance of each loop. The optimal capacitance of each loop that corresponds to the three functions can be found using a genetic algorithm (GA); the three functions were verified by comparing simulations and measurements at a frequency of 6.78MHz. Finally, the beamforming mechanism of a near-field loop array was investigated using the relationship between the current magnitude and the resonance frequency of each loop, resulting in the findings that the magnitude and the resonance frequency are correlated. This focused current of the specified loop creates a strong magnetic field in front of that loop, resulting in near-field beamforming.

This paper presents a conformal retrodirective metagrating with multi-azimuthal-angle operating ability. First, a flat metagrating composed of a periodic array of single rectangular patch elements, two-layer stacked substrates, and a ground plane is implemented to achieve one-directional retroreflection at a specific angle. The elevation angle of the retroreflection is manipulated by precisely tuning the value of the period. To control the energy coupling to the retrodirective mode, the dimensions of the length and width of the rectangular patch are investigated under the effect of changing the substrate thickness. Three values of the length, width, and thickness are then chosen to obtain a high retroreflection power efficiency. Next, to create a conformal design operating simultaneously at multiple azimuthal angles, the rectangular patch array using a flexible ultra-thin guiding layer is conformed to a dielectric cylindrical substrate backed by a perfect electric conductor ground plane. Furthermore, to further optimize the retroreflection efficiency, two circular metallic plates are added at the two ends of the cylindrical substrate to eliminate the specular reflection inside the space of the cylinder. The measured radar cross-section shows a power efficiency of the retrodirective metagrating of approximately 91% and 93% for 30° retrodirected elevation angle at the azimuthal angles of 0° and 90°, respectively, at 5.8GHz.

A new ramped-square sustain waveform is proposed to improve both the luminance and the luminous efficiency of an alternate current plasma display panel (ac PDP). The luminous characteristics such as the luminance and luminous efficiency have been measured with a square-voltage and a ramp-voltage (or voltage slope) of the proposed sustain pulse. With an increase in the square-voltage of a ramped-square sustain waveform, the luminance increases but the luminous efficiency decreases. On the other hand, with an increase in the ramp-voltage of a ramped-square sustain waveform, both the luminance and the luminous efficiency increase. When compared with the conventional square sustain waveform, an improved luminance of 22% and luminous efficiency of 36% are simultaneously obtained based on the proper adjustment of the square-voltage and ramp-voltage of the ramped-square sustain waveform in a 4-inch ac PDP test panel at a frequency of 62 kHz.