This communication presents a differential dual-polarized filtering dielectric resonator antenna (DRA). In this antenna, a four-leafclover shaped dielectric resonator (DR) is excited with two groups of outof- phase modes. The novel configuration and differential feeding provide the DRA with high isolation for input ports, and the elaborately designed feeding strips ensure controllable input impedances for integration applications. After integrating with a pair of filtering baluns on the opposite side of the reflecting ground, the proposed DRA also exhibits good out-of-band rejection for each port with a wide stopband and two radiation nulls at band edges. A prototype has been designed and implemented, and reasonable agreement between the measured and simulated results can be observed.

Planar spoof surface plasmonic polaritons (SPPs) have attracted much attention due to the features of the subwavelength confinement and low transmission loss. The later feature is highly desired in millimeter wave and terahertz band. In this communication, a novel method is proposed to convert bounded spoof SPPs mode to radiation mode. An equivalent radiating aperture is formed by gradually decreasing the grooves of an odd-mode plasmonic structure. The mechanism of SPPs wave radiating out through the aperture is clarified by referring to a horn antenna. Further, a spoof SPPs traveling-wave antenna prototype is designed and measured to validate the concept. Measured results show that the antenna has a high gain (~15 dB) and high radiating efficiency (~90%) at millimeter-wave frequency. The measured narrow beamwidth in endfire direction indicates that it can be used to construct switched-beam arrays for 5G applications.

The shared aperture antenna is regarded as one of the promising approaches to support new frequencies with very efficient space utilization. To the best of the authors’ knowledge, there are few shared aperture antennas that include both the sub-6 GHz antenna and the millimeter-wave (mm-wave) beam-steering array for broadside applications. In this article, a broadside sharing aperture technique is developed so that a 2 $\times4\,\,26$ GHz beam-steering substrate-integrated DRA (SIDRA) array can be integrated into a 3.5 GHz bandwidth enhanced perforated patch antenna in a coplanar and aperture-shared way. The proposed solution benefits from several aspects. First, the 3.5 GHz antenna features a compact size as this part is built on the substrate (where the mm-wave SIDRA is constructed) with a high permittivity. Second, the mm-wave SIDRA is a 3-D-type device, and in the case of coplanar integration, its height can be freely adapted to the thickness of 3.5 GHz antenna without concerning the impact from surface waves as many 2-D-type antennas have to do. Third, the antenna can be implemented with the multi-layer printed circuit board (PCB) process, yielding a high integrity level. The dual-frequency antenna was designed, fabricated, and measured. The performances of the antenna are reported with reasonable agreement between the measured and simulated results observed.

This communication presents a differential dual-band dual-polarized dielectric resonator antenna (DRA) with high isolation and low cross polarization using a cross-shaped DR. In the differential DRA, some of the higher order modes are eliminated and electromagnetic fields of each excited mode have no interaction with its corresponding orthogonal mode. Two groups of modes are utilized to realize dual-band characteristic and each group with two orthogonal modes is used to supply dual-polarized function. Differential feeding provides the DRA with suppression of unwanted modes, much higher isolation and lower cross-polarization in both frequency bands, compared with the traditional single-end feeding. The experimental prototypes of the proposed differential DRA and its single-ended counterpart are designed and implemented. The comparison between them is also made in reflection coefficient, isolation, and radiation properties. Both simulated and measured results show significantly improved performance of the proposed differential DRA.

This brief presents a new and effective approach for designing a high-selectivity tunable balanced bandpass filter (BPF) with constant absolute bandwidth (ABW). The filter is composed of two open-loop resonators with a pair of symmetrically loaded varactor diodes to obtain tunable responses. The major design concept relies on choosing the particular position on the resonator for loading the varactor diodes. The desired variation slopes of the external quality factor and coupling coefficient can be easily obtained for realizing the constant ABW of the tunable BPF. Frequency-dependent source-load coupling between the feed lines are introduced for realizing two adaptive transmission zeros (TZs) on both sides of the tunable passband. Thus, during the frequency-tuning process, high selectivity of the proposed filter can be kept. Meanwhile, the common-mode suppression is optimized to an acceptable level in the frequency-agile range of the differential-mode passband by loading the stub and resistor in the series at the center of the resonator. For demonstration, a tunable balanced BPF with the constant ABW and two TZs is designed and implemented. The simulated and measured results are presented, showing good agreement.