In this paper, a leaky-wave antenna (LWA) based on a double-layer dual-periodic (DL-DP) spoof surface plasmon polaritons (SSPPs) structure is proposed, which enables full-space beam scanning capability. The proposed antenna consists of a DL-DP SSPPs composite structure and two sets of spiked modulation modules. The top-layer SSPPs structure is arranged with a period of p1, while the bottom-layer SSPPs structure has a period of p2, where p2 = 2p1. The DL-DP SSPPs composite unit consists of a it-shaped element on the top layer and a T-shaped element on the bottom layer in a complementary arrangement. This design effectively suppresses the open stopband (OSB) effect. Owing to the unique T-it complementary configuration, the electric field coupling is significantly enhanced, resulting in stronger slow-wave characteristics compared to single-layer T-shaped or it-shaped units, thereby improving the scanning rate of the LWA. Two sets of spiked modulation modules are used to respectively excite the -1st harmonics of the SSPPs on the top and bottom layers, thereby radiating electromagnetic (EM) energy. Measured results show that within the frequency range of 7.1 GHz to 10.2 GHz (a relative bandwidth (BW) of 35.8 %), the antenna achieves full-space beam scanning with a relative scanning rate of 5.02 degrees/% BW and a peak gain of 10.5 dBi.

In this paper, a bidirectional multibeam folded transmitarray antenna (FTA) with low sidelobes is proposed. The FTA is composed of two different metasurfaces and a dual-polarized metal-only magneto-electric dipole antenna. A transmission unit with the characteristic of polarization conversion is designed, and the unit has high transmission magnitude and stable radiation performance. Different transmissive metasurfaces are formed by the same polarization conversion transmission unit. The dual-polarized metal-only magneto-electric dipole antenna is used as the feeding source to achieve forward and backward radiation when two ports are fed respectively. Different phase compensation distributions for the upper and lower transmissive metasurfaces are designed to achieve multibeam characteristics. Taylor distribution is applied to the lower transmissive metasurface to reduce the sidelobe levels of the transmitted beam. The antenna achieves a peak gain of 22.1 dBi and a peak aperture efficiency exceeding 30% during forward radiation. In backward radiation, the beam has a low sidelobe level and exhibits a 3-dB gain bandwidth of 33%.The proposed FTA has the advantages of high gain, high aperture efficiency, miniturization and low-sidelobes, making it suitable for bidirectional wireless communication scenarios.

This paper presents a wideband dual-circularly polarized dual-beam transmitarray antenna with linear polarization feeding source. A transmitting-receiving structure is designed for the low-profile transmissive element, and the linearly-polarized incident wave is converted into left-handed and right-handed circularly polarized waves by means of the polarization decomposition principle. To improve the performance of the dual beams, a dual-frequency phase error optimization scheme is adopted to optimize the initial phase distribution according to the phase compensation principle. The measurement results show that from 9.5 to 13.5 GHz, the 1 dB bandwidths of the left-handed and right-handed circularly polarized waves are 18.2% and 17.9% respectively, and the 3 dB gain bandwidths are 29.8% and 30.6%. The relative bandwidth with an aperture efficiency better than 30% is 27.6%, verifying the reliability of the optimization scheme for improving the performance of the dual beams.

A dual-band reconfigurable reflectarray antenna (RRA) employing all-metal waveguide elements is proposed in this paper. The element adopts a three-layer nested rectangular cavity structure, enabling independent phase manipulation in two separated frequency bands: 12–18 GHz (lower band) and 24–28 GHz (upper band). By utilizing the cutoff frequency and mode separation principles of rectangular waveguide resonators, the outer and inner cavities separately control the phase responses at low and high frequencies, respectively, with negligible mutual interference. The low-band phase is tuned by shifting the middle cavity, while the high-band phase is adjusted by moving the inner metal post. Both bands achieve full 360° phase coverage with stable reflection magnitude. This paper presents the design and simulation a 20×20 reflectarray antenna. The results show that the peak gain reaches 27.5 dBi at the low frequency band and 27 dBi at the high frequency band. The antenna achieves a maximum beam scanning angle of 50° in the low band and 30° in the high band. Throughout the scanning process, the sidelobe level remains at a relatively low level. Featuring low loss, high power handling capacity and stable dual-band operation, the proposed antenna is suitable for broadband wireless communication systems.

A wideband and low-profile folded transmitarray antenna (FTA) is proposed for K-band application in this paper. To ensure high gain and reduce the profile of antenna system simultaneously, both the transmissive metasurface and reflective metasurface with polarization conversion function are employed to construct multiple reflection paths for near-field electromagnetic waves, and a conventional widebeam open-ended waveguide is adopted as the feed source. The phase compensation of the transmissive surface is optimized using the Genetic Algorithm to reduce the quantization error caused by the state discreteness of the transmission unit, thus widening the gain bandwidth. For the fabricated prototype, the upper transmissive metasurface consists of 27×27 units and the lower reflective metasurface consists of 24×24 units. The antenna profile is 1.5λ0, and the height-to-diameter ratio is only 0.19. Measurement results show that the 3-dB gain bandwidth is 36.4% (18.8–27 GHz) and the peak gain is 23.3 dBi. The proposed FTA is a promising candidate for future wireless communication systems.

A highly integrated circularly polarized (CP) filtering dielectric resonator antenna (DRA) array based on a folded helical structure is proposed in this paper. The antenna element mainly consists of a half-wavelength folded metal helical strip and a hollow cylindrical dielectric resonator. The Hybrid Electric Magnetic (HEM) mode of the DRA can be regarded as an equivalent magnetic current (MC), which is excited by the electric current (EC) on the helical strip. Based on the magneto-electric currents combination (MECC) method, MC and EC with appropriate amplitude ratio and phase difference are designed to realize CP performance. According to the fusion method, an electromagnetic coupling excitation structure combining substrate integrated waveguide (SIW) and embedded coplanar waveguide (CPW) is adopted to regulate the internal field resonance mode of the SIW cavity, enabling the antenna to successfully possess bandpass filtering characteristics. The antenna element is excited by a microstrip power divider above the slot and expanded into a 2 x 2 array. The prototype of the antenna has been fabricated, and measured results demonstrate that the proposed antenna has a relative impedance bandwidth of 11.2% and an axial ratio bandwidth of 6.2%, with radiation nulls at both sides of the passband. Measurement results show gains of 7.42 dBi (element) and 9.28 dBi (2 x 2 array). The proposed antenna is suitable for ground-based equipment in C-band satellite communication systems.

To explore higher-performance satellite communication antennas, a dual-frequency dual-circularly polarized antenna based on a Fabry-Perot (F-P) resonant cavity is proposed in this letter. An artificial magnetic conductor (AMC) is loaded onto the resonant cavity as a partial reflection surface (PRS) to reduce the profile. The electromagnetic (EM) waves from the feeder are reflected multiple times within the cavity and subsequently superimposed in phase, thereby enabling dual-frequency operation and high gain. Right-handed circularly polarized (RHCP) and left-handed circularly polarized (LHCP) waves are respectively generated in the lower and higher frequency bands by incorporating a dual-frequency polarization conversion surface (PCS). Two rectangular microstrip patch antennas with a simple feeding network are employed as the feeder for RHCP and LHCP, respectively. The measurement results show that the operating bandwidth is 4.77% (12.47-13.08 GHz) for the low-frequency band and 5.36% (16.51-17.42 GHz) for the high-frequency band. The maximum gains of 14.91 dBi and 14.33 dBi are achieved for the lower and higher frequency bands, respectively. The proposed antenna fulfills the requirements of the frequency division duplex satellite communication system, providing a promising candidate for ground equipment in high-speed satellite Internet applications.

A wideband with profile-reduced transmitarray antenna based on phase-shifting elements is proposed in this letter. The element of transmitarray comprises three metal layers with a double-slotted metal ring aperture and two dielectric layers. The stable transmission coefficient is achieved with compact coupled structures. The simulated electric field on the reference plane is analyzed to optimize the focal-to-diameter (F/D) ratio. Furthermore, a precise optimization method by reducing the phase error in the phase compensation scheme is designed to improve the gain bandwidth of antenna. The optimized transmitarray is fabricated and measured, which consists of 20 x 20 elements. The F/D ratio is reduced by 27%, and the 1-dB and 3-dB gain bandwidths are 22.90% and 28.75%. The peak aperture efficiency reaches 43.06%. The optimization scheme can be applied for broadbanding design of transmitarray with a limited profile height.

In this paper, a dual-band, dual-linearly polarized multibeam transmit-reflect-array (TRA) antenna is proposed. The dual-beams with different polarizations can be transmitted in the lower frequency band and reflected in the higher frequency band. The element comprises three metallic layers separated by substrate, enabling independent control of vertically and horizontally polarized waves in both the reflective and transmissive bands. Due to the frequency and polarization independence of the element, phase compensations are designed for vertically and horizontally polarized waves in each band, respectively. The circular aperture TRA is illuminated with a rotated linearly polarized horn, thereby generating dual-beams with different directions and polarizations in both the transmissive and reflective modes. The measurement results show that the peak aperture efficiency is 43.6 % and 36.0 % for the reflection band and transmission band. For the transmission band, the 3 dB gain bandwidths are 11.2 % (21-23.5 GHz) for horizontal polarization and 16.1 % (20-23.5 GHz) for vertical polarization. The 3 dB gain bandwidths for the reflection band are 12.1 % (27-30.5 GHz) for both the horizontal and vertical polarizations. The TRA antenna emerges as a promising contender for the implementation of bidirectional wireless communication.

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.

This paper proposes a circularly polarized (CP) filtering dielectric resonator antenna (DRA) based on a substrate-integrated waveguide (SIW) cavity. The antenna is fed by a stacked feeding network to excite the dipole and DRs. The current is generated by a pair of dipoles and the equivalent magnetic current is generated by DRs. In one cycle, the current and the equivalent magnetic current operate alternately along the same direction with a phase difference of 90°, resulting in a circularly polarized wave. SIW cavity has high-pass transmission characteristics. The reflection coefficient and gain of the antenna show some sideband selective characteristics, which indicates that the antenna has a filtering function. The antenna obtained a relative impedance bandwidth of 26.51% (5.04-6.58 GHz) and an axial ratio bandwidth of 15.6% (5.26-6.16 GHz). With outstanding CP performance and compact size, the proposed CP filtering DRA is an attractive candidate for satellite communications.

This paper presents a new design of dual polarization near-field focused metasurface for high-efficiency wireless power transfer with multi-focus characteristics. The metasurface element consists of Jerusalem structure and four accompanying resonators surrounding them, and the linearity of the phase curve is improved by adjusting the ratio of the center resonator of the metasurface element to the accompanying resonator length, avoiding the impact of reducing the physical manufacturing accuracy on the focusing effect. In terms of focus phase synthesis of reflective metasurface, the metasurface with independent regulation of dual polarization is introduced to realize multi-focus and high-efficiency wireless power transfer. The dual polarization single-feed two-focus metasurface working at 11 GHz and 14 GHz with 15×15 elements are designed, fabricated and measured by planar near-field scanning experiments. Through full-wave simulation of two cases, operating at 11 GHz and 14 GHz, dual polarization single-feed two-focus can realize the maximum focusing efficiency of 69.8% and 70.8%, respectively. The relative bandwidth with 50% power focusing efficiency of these two cases are all over 18%. The measured results are in good agreement with the theoretical designs and simulated results, which verify the feasibility and correctness of the proposed approach in this paper.

In this letter, a 2×2 shared-aperture dual-band array antenna is presented, which utilizes gap waveguide technology to achieve wide bandwidth. The proposed dual-band radiating element consists of two layers of open radiating cavities and a metal cover plate. The cavities are designed as hexagonal structures of different sizes. The lower and upper radiating cavities operate in X-band and Ku-band, respectively. The upper cavity is placed orthogonally relative to the lower cavity for generating different line polarizations and improving the isolation between them. Each cavity is fed by a separate groove gap waveguide. An array is formed and simulated using the proposed dual-band radiating elements. The simulation results show that the -10.0 dB impedance bandwidth of the proposed antenna are 9.8-11.0 GHz in X-band and 14.7-19.0 GHz in Ku-band, respectively. The realized gains are 14.7 dBi (at 10.0 GHz) and 16.7 dBi (at 15.5 GHz) in two different polarizations.

A wideband high-efficiency metal-only folded reflectarray antenna using 3-D subwavelength detachable trapezoidal grooved element is proposed in this communication. The presented element is made up of two orthogonally rectangular metal plates etched with two trapezoidal grooves. It allows reflection phases of the two linearly polarized waves to be shifted independently by varying the lengths of the grooves. To make a detachable structure, a sliding groove is employed on one of the two metal plates to help assembly. By setting the period to a subwavelength, smooth phase-shift response is obtained to extend the bandwidth. In addition, a large reflection phase variation of 670° at 10.0 GHz and low element loss of nearly 0 dB are obtained to further enhance the gain. Then, a 35 × 35 element reflective aperture spatially fed by a 3-D printed pyramidal horn antenna is designed and measured to verify the performance. The measured results exhibit that a wide 1-dB gain bandwidth of 26.5% is achieved. To reduce the profile, a wideband triple-layer polarization selector suspended on the reflective aperture is designed to achieve a folded reflectarray antenna prototype. It features a maximum gain of 29.2 dBi corresponding to an aperture efficiency of 51.8%, and a 3-dB gain bandwidth of over 34.2%. These results indicate that this metal-only folded reflectarray antenna has advantages on wide bandwidth and high efficiency.

This brief presents a miniaturized wideband circularly polarized magneto-electric dipole antenna using Ψ-shaped phase shifter. Its magneto-electric dipole structure utilizes four L-section patches attached to outer edges of four square patches to achieve miniaturization. A parasitic patch positioned above the dipole structure is employed as an impendence transformer to extended the bandwidth. Meanwhile, a notched cavity equivalent to four magnetic dipoles is set around the dipole structure to enhance the beamwidth. To achieve circularly polarized wave, a feeding network composed of four-order Wilkinson power divider and Ψ-shaped phase shifter is designed to realize two equal-amplitude outputs with 90∘ phase difference. The Ψ-shaped phase shifter utilizes an open-short stub combining open circuit and short circuit, then achieving 106.9% impendence bandwidth with low insertion loss of 0.03 dB at 1.5 GHz. Then, the proposed antenna is fabricated with a compact size of 0.5λ0×0.5λ0×0.3λ0 (λ0 at 1.5 GHz). The measured results show that its impedance bandwidth is 94.6% while the 3-dB axial ratio bandwidth reaches 107.1%. The maximum half-power beamwidth reaches 144∘/135∘ at -45∘/45∘ -plane within the band from 0.78 GHz to 2.15 GHz while maximum axial ratio beamwidth respectively obtains 182∘/203∘ in -45∘/45∘ -planes.

In order to meet the demand of high capacity and high speed transmission of satellite communication system, a wideband dual-circularly polarized dielectric resonator antenna (DRA) array is proposed based on the traveling wave principle. Four DRA elements with slot-coupling excitation are sequentially placed on the ground, and the feeding network is designed to realize the two orthogonal circular polarization radiation waves. A notched copper loop (NCL) around the antenna array is adopted to improve the radiation performance. Depending on the operation of the two ports, the NCL generates the induced currents which rotates clockwise/counterclockwise, increasing the axial ratio bandwidth. In order to further improve the gain stability, the copper sheets are embedded on the top surface of each radiation element, and the copper cylinders perturb the internal field distribution of the DRA to introduce higher-order modes. The measurement results show that the left-hand circular polarization and the right-hand circular polarization operating bandwidths are 11.8% (14.97-16.85 GHz) and 12% (14.91-16.82 GHz). The antenna gain achieves 9.0 dBic. This DRA array can be applied for the vehicle mounted RF terminals in satellite communication.

A hybrid dielectric resonator antenna (DRA) array is proposed for the wideband millimeter-wave communication. The radiator is composed with a pair of stacked dielectric resonators (DRs), which are H-shaped and Hexagon-shaped DRs, respectively. The dual-slots on the substrate integrated waveguide (SIW) cavity are utilized for higher mode generation in the DRA element. The antenna bandwidth is improved by the stacked DRs and dual-slot feeding. The structural characteristics and key parameters of feeding slots are discussed in detail. The DRA array fed with parallel power distribution feeding network is fabricated and measured to verify the reliability of the simulations, and the simulations and measurements have reasonable consistency. The impedance bandwidth is from 23.55 GHz to 27.28 GHz (14.7%), and the measured gain ranges from 13.1 dBi to 15.7 dBi. The radiation patterns are stable in the operation band. The proposed DRA array has a promising application prospect for 5 G communication system.

A partial-annular directional antenna with wide bandwidth and high gain is proposed in this paper. The radiator is a simple partial-annular metal microstrip loaded with hexagonal patch, which is exited with coaxial cable. The ground is reduced to a rectangular patch with small area, which is required by the deployment. As the reflector, the circular Aluminum plate is λ/10 below the radiator to enhance the antenna gain and front-to-back ratio (FBR). The air gap between the semi-annular antenna and the reflector is also helpful for the improvement of impedance math. The simulation results show that the relative bandwidth of the proposed antenna is 46.6% (3.85 – 6.19 GHz), and the gain varies from 7.91 to 9.93 dBi. Due to the semi-annular strip structure and defected ground, the proposed antenna could be used for the limited deployment space, such as radio wave detection, terminal of mobile communication, and so on.

A directional dielectric resonator antenna (DDRA) for 5G mobile communication system is proposed. The antenna is side-fed with the metal probe to make it work in quasi-TE delta 11 mode, so as to realize the characteristics of directional radiation. The stacked structure is adopted, and the two side walls of the rectangular dielectric resonator parallel to the microstrip line are grooved to improve the frequency bandwidth of the antenna. Furtherly, the Koch snowflake fractal is used for the second iteration of the top cylindrical dielectric resonator, and the parasitic metal columns inside the DRA are also helpful for the enhancement of bandwidth. The prototype was fabricated and tested to verify the design, and the measured results show -10 dB impedance bandwidth of about 23% and an average gain of 5.2 dBi within the operation band.

In this letter, a UHF-RFID tag antenna with a size of 40 × 40 × 3.2 mm 3 is proposed for metallic objects. It is composed of a modified folded dipolar antenna (MFDA) and an embedded 2 × 2 artificial magnetic conductor (AMC) array with shorting vias. Multiple slots are etched on the MFDA and AMC to increase the current path, where the slots on the MFDA is vertical to that on the AMC so that the currents on the MFDA and AMC do not affect each other. Thus, the slots can be adjusted independently without affecting the resonant feature of the MFDA. Equivalent circuit models are also presented to understand the impedance characteristics. A prototype mounted on a 20 × 20 cm 2 metal plate has been manufactured and measured. It is demonstrated that the proposed tag antenna shows a 3.9 dB gain enhancement comparing with the MFDA without AMC and a maximum gain of −1 dBi at 919 MHz. Moreover, a maximum reading distance of about 14.2 m can be obtained.