A novel pattern-reconfigurable dielectric resonator antenna (DRA) with compact structure and high efficiency is proposed in this letter by introducing a pair of switchable directors. The switchable directors are arranged on both sides of an omnidirectional DRA, which operates in the TE01δ mode. Their directing function can be controlled by switching the on / off status of the p-i-n diodes so that one omnidirectional radiation pattern and two unidirectional endfire patterns are provided in the azimuthal plane. To verify this idea, a prototype of the proposed antenna is fabricated and measured. Good agreement between the simulated and measured results can be observed. The peak gain in endfire status reaches 4.5 dBi and the front-to-back ratio is more than 12 dB. Meanwhile, the gain variation of the omnidirectional pattern in the azimuth plane is less than 2 dB, which shows good omnidirectional radiation performance.

A novel pattern-reconfigurable dielectric resonator (DR) antenna with endfire beam-scanning feature is proposed in this letter. The proposed antenna consists of a DR, a switchable director with 10 p-i-n diodes, and a differential feeding structure. The differential-fed DR operating in TE _01δ mode can provide a primary endfire pattern with wide beam. Based on this, a large-coverage beam-scanning performance can be obtained by introducing a switchable director placed in front of the DR. A prototype is fabricated and measured to verify the proposed design. By switching the p-i-n diodes of the switchable director, the proposed antenna enables a near-continuous beam scanning from −48° to +48° in the azimuth plane with a gain fluctuation of less than 0.5 dB. Besides, the 3 dB scanning coverage is up to 164° (from −82° to +82°), which shows good beam-scanning performance.

This letter proposes an asymmetrical low-radar cross section (RCS) frequency selective surface (FSS)-based low band (LB: 1.7-2.7 GHz) antenna for the application in tri-band shared-aperture array. In the array, high band 1 (HB1: 3.3-3.8 GHz) antennas and HB2 (4.8-5 GHz) antennas are distributed on the two sides of the asymmetric LB antenna with four FSS unit cells. The bandpass property of the FSS unit cell is formed after inserting a patch into the square loop, meanwhile, it can be controlled by cutting the patch into more pieces. To respectively suppress the blockage effect of the LB antenna on the two-side HB1 and HB2 antennas, a low-RCS FSS-based LB antenna is constructed asymmetrically by placing two kinds of low-RCS FSS unit cells with different patch pieces. Importantly, the low-RCS characteristic of the FSS unit cells on both bands and LB working performance can be independently controlled, so that good performance for both of them can be obtained, without timeconsuming optimization. Finally, the LB blockage effect on the entire HB1 and HB1 has been significantly reduced as expected and good agreement is achieved between the simulation and experiment.

This letter proposes a microstrip switchable dual balun using a symmetrical three-coupled-line structure, which is used as a feeding network for designing a pattern-reconfigurable endfire antenna. By adding p-i-n diodes to the ends of the coupled quarter-wavelength lines, the proposed balun enables three-status operation while it has compact size and simple configuration. Based on this, a pattern-reconfigurable endfire antenna is designed, fabricated, and measured. Good agreement between the simulated and measured results can be observed. The peak gain of two directional statuses reaches 5.8 dBi and the front-to-back ratio (F/B) is more than 18 dB. Meanwhile, the peak gain of bidirectional status reaches 2.7 dBi and the F/B is less than 0.5 dB.

This paper presents a design approach of broadband filtering quasi-Yagi DRR Antenna using a strip-loaded dielectric ring resonator (DRR) and near-zero-index (NZI) metamaterial (NZIM). The ring strip is loaded to the inside wall of the DRR so that the TE _01δ and TE _21δ modes of the DRR can be close. Meanwhile, they function as a dual-mode magnetic dipole (M-dipole) driver and can be differentially excited at the same time for designing a wideband quasi-Yagi antenna. Benefiting from the dual-mode operation of the strip-loaded DRR, the end-fire gain across the operating band of the antenna is stable with preliminary bandpass filtering characteristics. To improve the in-band gain and enhance the filtering capability, a new coplanar NZIM with wideband NZI characteristic and dual transmission notches in the lower and upper stopbands of the preliminary gain passband, is introduced and put in the front of the DRR driver. To verify the proposed design concept, an X-band filtering quasi-Yagi antenna with the NZIM is fabricated and measured. Good agreement between the simulated and measured results can be observed. The wideband antenna has a measured -10 dB impedance bandwidth of about 16% (8.5 - 10 GHz). Within it, the peak gain of antenna reaches 8.3 dBi and 1-dB gain fractional bandwidth is about 10.8%. Meanwhile, it exhibits good gain bandpass response due to the transmission notches of the NZIM.