This communication proposes the wideband circularly polarized (CP) phased array antenna system for wide axial ratio scanning. For mobile satellite communication, the low-profile CP antenna with a wide axial ratio scanning region in wide frequency bandwidth is necessary, but the antenna with the required axial ratio performance is rarely reported. In this communication, the proposed CP phased array antenna system with an axial ratio control scheme has a wide axial ratio scanning region in the wide frequency bandwidth. In the proposed axial ratio control scheme, the amplitude and phase of the received signals are controlled to compensate for the difference between dual polarizations. The proposed antenna system is designed at 5.8 GHz and has a fractional frequency bandwidth of 20%. In a simulation, the axial ratio is under 1 dB at the elevation scanning region from −60° to 60° at every 360° azimuth angle in the operating frequency bandwidth. For validation, the $1\times 8$ CP phased array antenna system was implemented. The measured axial ratio is under 2 dB at the elevation scanning region from −57° to 57° in the operating frequency bandwidth.

Minimizing the size of mobile antennas is necessary for integrating the components inside a mobile device. Wideband and multiband antennas are also required to cover various 5G mobile communication frequency spectra. This article presents a vertically stacked dipole antenna array operating in the 28/38 GHz dual-band. The proposed antenna is small and satisfies the need for wide bandwidth in the form of a dual band. The antenna structure has symmetric 38 GHz band radiators positioned above and below a multilayer substrate, and a 28 GHz band radiator positioned on the middle plane, providing a dual-band antenna structure with small lateral width. Herein, two types of antenna structures are proposed, each with a single-ended and differential feed structure for compatibility with various RF front ends. The single antenna yields −10 dB bandwidth for return loss of 23.9% and 14.4%, and gain of 4.8 and 4.6 dBi at 28 and 38.5 GHz, respectively. The 4-element antenna array yields a gain of 9.0 dBi at 28 GHz and 10.3 dBi at 38.5 GHz. It was fabricated on a flexible substrate and can be bent and inserted into the lateral edge of the terminal. The proposed antenna elements and arrays satisfy the performance factors requisite for millimeter wave 5G communication including compact size, wideband, dual-band, and adequate gain.

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.

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.

For Internet of Things (IoT) applications. The proposed antenna has stub structures for generating additional resonant mode, by which two polarization components orthogonal to each other are realized within the impedance bandwidth. By the combination of the two modes, circularly polarized radiation is generated. The impedance bandwidth increase by the additional resonant mode, and the proposed stub structures act as a capacitive loading contributing to the miniaturization of the antenna. For validation of the proposed antenna, simulations were conducted, and the antenna was fabricated and measured. The fabricated antenna size is 0.23λ0 × 0.23λ0 × 0.04λ0, showingasignificantly compact size compared to the conventional structures. The measured results confirm that the antenna has a impedance bandwidth from 896 to 958 MHz, and 3 dB axial ratio (AR) bandwidth is about 5 MHz. The measured peak gain and AR at 915 MHz are 2.4 dBic and 0.6 dB, respectively.

This communication presents a shorted trapezoidal substrate integrated waveguide (SIW) antenna with a quasi-hemispherical pattern composed of a 64-element (8 $\times $ 8) 2-D planar phased array. The proposed low-profile SIW antenna is analyzed in terms of resonating mode and magnetic current and is simulated. The proposed antenna is composed of a trapezoidal patch and shorting vias. The upper side of the trapezoid is the shorting wall, and the middle of the bottom side provides shorting with a via. The resonance produced by the structure causes the magnetic currents to have three different directions. Hence, the single element has a quasi-hemispherical beam pattern on a large ground. The 64-element (8 $\times $ 8) 2-D planar phased array was implemented and measured. Because the constituent elements have a quasi-hemispherical pattern, the phased array antenna has a wide scanning range in all azimuth directions. The measured scanning range with 5 dB gain fluctuation in the $\phi = 0^\circ $ plane, $\phi = 45^\circ $ plane, and $\phi = 90^\circ $ plane are 170°, 143°, and 168°, respectively.