ABSTRACT A reconfigurable reflective metasurface design is proposed in this letter, allowing for beam scanning capabilities. This paper integrates a tunable capacitor into the metasurface unit. This paper integrates a tunable capacitor into the metasurface unit. The resonant characteristics of the metasurface unit are controlled by the tunable capacitor, which can be adjusted by changing the rotation angle of the metal plate on the tunable capacitor. By rotating the metal plate of the capacitor, it achieves state 1 at maximum capacitance and state 0 at minimum capacitance, resulting in a phase difference of 180° ± 20° between the states, thereby enabling 1-bit phase control. Leveraging the principle of phase compensation, the phase distribution of the array is designed to exhibit directional radiation characteristics. A reflective metasurface composed of a 20 × 20-element array is designed and simulated with these characteristics. The simulation results indicate that the scanning angle of the array-reflected beam can reach ± 50°, with a peak gain exceeding 14.6 dBi, an average gain of 13.8 dBi, and a gain loss of 1.5 dB. The beam’s 3 dB beamwidth exceeds 15°, enabling broader coverage. Joint simulations in typical indoor scenarios confirm the improved signal strength, highlighting the array’s versatility. This design allows the reflective array to function as a passive reflector relay, effectively improving signal coverage in indoor NLOS.

ABSTRACT In this paper, a miniaturized 5 G microstrip lumped hybrid dual-band bandpass filter (BPF) with ideal transmission response, simple structure, and compact size is proposed and characterized. The conversions from lumped elements to microstrip lines are analyzed and demonstrated by utilizing the ideal theoretical circuit model and EM field model. The center frequency of 0.57 GHz and the second passband located at 1.29 GHz are implemented by the proposed dual-band BPF with 3 dB fractional bandwidths of 59.6% and 15.5%, respectively. Additionally, five transmission zeros are strategically positioned on both sides of the passband. The prototype filter with minimized circuit size on occupies 0.05λ g × 0.06λ g is fabricated and verified that minimum insertion losses in the passbands are separately 0.83 dB and 0.52 dB. Ideal agreement between the simulated and measured results confirms the reliability of the design approach.

ABSTRACT A circularly polarized (CP) filtering dielectric resonator antenna (DRA) array is proposed based on the magneto-electric currents combination (MECC) method in this paper. The array consists of four rectangular DRAs, four hook-shaped electric dipoles (HSED), and two layers of substrate integrated waveguide (SIW) cavities. The electric current (EC) on the HSED is excited by the slot aperture of the SIW cavity, and the equivalent magnetic current (MC) is simultaneously generated with HSED in the DRA. Based on the surface current regulation, the EC and MC are adjusted to achieve appropriate amplitudes and phases, thereby realizing wideband CP radiation. The filtering function is realized with the high-pass characteristics of the SIW and the effective suppression of the higher-order modes in the resonance cavity. Due to the presence of an air gap between the DRAs and HSED, the higher modes of the DRA are designed for bandwidth enhancement. The prototype of the DRA array has been fabricated and measured, exhibiting a relative bandwidth of 26.1% and an axial ratio bandwidth of 17.77%, with radiation nulls present at either side of the passband. With the advantages of wide bandwidth and high gain, the proposed DRA array can be applied to satellite communications.

ABSTRACT This paper presents a circularly polarized (CP) monopulse slot array antenna based on gap waveguide (GWG) technology. The proposed monopulse antenna is composed of a 4 × 4 array antenna fed by the monopulse comparator network in a compact three-layer structure. To achieve a broad axial ratio (AR) bandwidth of right-handed circular polarization (RHCP) in the sum radiation pattern, a septum polarizer is used in the radiating aperture. Based on this approach, horizontal transition structures are used to excite the radiating array from the WR-28 waveguide to the GWG, which helps to reduce the reflection loss and expand the impedance bandwidth. Experimental results show that the impedance bandwidth is 30.5 GHz to 40 GHz, which is 27.1%. The 3 dB AR bandwidth is 31%. The measured null depth is −40 dB, and the maximum measured gain in the sum pattern is 22 dBi at 34 GHz, while the antenna efficiency is greater than 86%. The advantages of low loss, broad bandwidth, and compact structure make the proposed antenna a competitive candidate for millimeter-wave (mmWave) monopulse direction-finding applications.

ABSTRACT A novel wideband circularly-polarized (CP) MIMO filtering array antenna with dual-layer circular cross-slotted patch is introduced. The presented element consists of a two-way feeding structure designed with equal amplitude and 90° phase difference, and a dual-layer circular cross-slotted patch structure. An aperture-couple-driven patch is positioned between a cross-slotted patch and a dual-feed structure. It facilitates magnetic coupling to achieve a high-frequency resonant mode and radiation null. Meanwhile, four arc-shaped patches are electrically coupled to the driver patch by surrounding it with four shorting vias to improve the bandwidth. In multiple-input multiple-output (MIMO) wireless systems, a two-port MIMO dual-CP filtering array antenna for the Sub-6 G band is proposed. The design utilizes four proposed CP antenna elements and a dual-port transmission structure. The dual-port transmission structure consists of two sets of T-junction power dividers that are 180° phase shifted with opposite polarization. The dual-CP MIMO filtering array antenna of the impedance bandwidth is 21.8% (3.1 ~ 3.9 GHz). The AR bandwidth is 13.1% (3.3 ~ 3.7 GHz), while the gain bandwidth is 20.1%. Additionally, the isolation between the antenna elements is less than −15.0 dB. The envelope correlation coefficient between its two ports is less than 0.02.

ABSTRACT A novel method is proposed to achieve a low-profile miniaturized dual-band dielectric resonator antenna (DRA) for wireless communication applications. The cylindrical dielectric resonator (DR) is fed by a microstrip loop on the top surface of the substrate and a mountain shaped ground on the bottom surface of the substrate. This structure not only effectively transfers energy to the DR but also plays a pivotal role in establishing a lower resonance frequency of 1.73 GHz, achieving this with a compact structure (0.21λ 0 × 0.18λ 0 × 0.02λ 0, and λ 0 is the free-space wavelength at 1.73 GHz). HEM11δ mode of the cylindrical DR is employed to cover the upper frequency band of 2.8 GHz. Ultimately, the effectiveness of our suggested approach and the antenna’s performance are confirmed through the measurement.

ABSTRACT In this paper, an efficient feed network for small secondary surveillance radar (SSR) antennas is introduced. It integrates all three required beams (SUM, DIFF, and CTRL) into a single-sheet design. The architecture employs a side element to generate the control (CTRL) beam for a 7-element 1.5-meter SSR antenna array. The target performance includes keeping the gain above 15 dBi and a side lobe level exceeding 20 dB at 1030 MHz and 1090 MHz for the SUM port while reducing the loss of the CTRL beam. In this work, a modified Gyzel unequal power combiner replaced the conventional Wilkinson power combiner to adjust the feed network’s power-sharing. Also, a practical method for implementing a high coupling value of 7 dB in a directional coupler is presented as one of the key steps to achieve a very low loss of 2.9 dB in the CTRL path (2.4 dB improvement). Simulation and measurement results validate the proposed feed network’s performance.

ABSTRACT It has become a common challenge on how to measure radiation patterns of massive antenna arrays working at high frequency with high efficiency and accuracy, which has attracted huge interest from both academia and industry. In this paper, a highly accurate and efficient far field (FF) pattern reconstruction strategy through conducting single cut near field (NF) to FF transformation algorithm based on spherical wave expansion (SWE) is proposed for fast measurements of large base stations (BSs) operating at mid-band. Our objective is to design a compact multi-probe setup to measure key radiation parameters of the massive array, with low-cost and high-efficiency. A BS of 16 × 16 elements operating at mid-band is adopted as the device under test (DUT) in this paper. Analysis is conducted on the impact of measurement distance, sampling range and sampling density on the reconstruction accuracy of the algorithm in the compact multi-probe anechoic chamber setup, demonstrating that the required key information of the main lobe of the DUT can be accurately reconstructed when the measurement range R = 1/20 FF distance, sampling resolution ∆θ = 3°, and sampling range θ ∈ [75°, 105°] are selected, respectively. The impact of phase center offset on the accuracy of FF pattern reconstruction is analyzed when only one sub-array is enabled, demonstrating the effectiveness of the algorithm for sub-array measurements.

ABSTRACT A beam-reconfigurable millimeter-wave (mm-wave) antenna is proposed, constructed with a dodecagonal substrate integrated waveguide (SIW) structure and a cavity-backed U-slot SIW switch. The SIW switch consists of a U-shaped slot in the ground plane, a p-i-n diode, and a pair of metallic vias, primarily operated by controlling the impedance of the U-shaped slot. Six SIW switches are employed to enable six-beam switchable reconfiguration. Correspondingly, six 4 × 4 SIW slot subarrays are equiangularly arranged along the periphery of the dodecagonal substrate, acting as the main radiators. By carefully controlling the excitation phase and magnitude of the slot elements in the subarrays, a tilted beam of approximately θ = 19° can be produced in measurement with switchable reconfigurable beams 1‒6 steering along the azimuth plane at discrete angles of approximately ϕ = 90°, 150°, 210°, 270°, 330°, and 30°, respectively. The measured results indicate that the overlapped impedance bandwidth (|S11|<-10 dB) of the proposed antenna is across 25.63‒26.08 GHz with a relative bandwidth of 3.7%. The measured antenna peak gains for beams 1‒6 can reach up to 8.0 dBi.