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This letter presents a dual-polarized low-profile linear phased array antenna design achieving one-dimensional wide-angle scanning with high polarization isolation. The dual-polarized antenna is constructed based on a metasurface serving different purposes for two polarization cases to achieve high polarization isolation while providing a low profile as a whole. It works as artificial magnetic conductor for x-polarization and radiator for y-polarization. To achieve wide-angle scanning, surface wave effect is exploited for x-polarization while for y-polarization widebeam active element patterns is implemented with a small array spacing of 0.42 λ0 applied. To verify the design, a 1×8 linear array was fabricated and tested. Measured and simulated results both demonstrate that, within a wide operating band, the proposed dual-polarized antenna has a high port-to-port polarization isolation over 29 dB with a low profile of 0.06 λ0. The measured results show that for x-polarization, the linear array can steer its main beam up to 81°, while for y-polarization, it can steer the main beam up to 70°. The cross-polarization levels can maintain below −20 dB during scanning in the general. [ABSTRACT FROM AUTHOR]

A magnetic Yagi-Uda antenna applying higher order mode in millimeter-wave (mm-Wave) band with vertically polarized endfire radiation is proposed in this article. Surface wave mode analysis is applied to spot TE mode for magnetic Yagi-Uda antenna in contrast to TM mode for electric Yagi-Uda antenna. A modified structure evolved from conventional U-shaped cavity is used to address the reversed current issue for higher order mode, which exhibits a more uniform phase distribution at the Yagi-Uda array end. Then, a composite end-feeding structure with reflector integrated is further introduced to minimize its parasitic effects for practical antenna design in mm-Wave band. To validate the design, a prototype with a size of 2.7 $\lambda _{\mathbf {0}}\times1.25\lambda _{\mathbf {0}}\times0.088\lambda _{\mathbf {0}}$ is fabricated and tested. It can achieve anendfiregain of 8–11 dBi within 24–26 GHz with –10 dB impedance band covering an even wider frequency range. The measured front-to-back ratio (FBR) is larger than 16.1 dB. Vertically polarized radiation is realized with cross-polarization level lower than –20 dB atendfiredirection. [ABSTRACT FROM AUTHOR]

A design approach of triband conformal monopolar antenna combining cavity mode and equivalent circuit (Ec) is proposed. First, based on mode analysis, two lower and closer resonant frequencies in the VHF-band are generated by introducing two slot rings and two circles of short vias to a circular parallel-plate structure. Second, its Ec is extracted and modified. Then, the geometry structure is improved accordingly. An inverted truncate cone is introduced to modify the characteristic impedance of the monolithic radial transmission line to obtain an available band in the middle frequency (UHF). Finally, a high-frequency (L) antenna is embedded into the truncate cone and excited by a novel composite feeding structure. Furthermore, the conformal performance of the triband antenna is investigated. The conformal antenna prototype is fabricated and achieves a triband within 69.3–72.5 MHz, 317–348 MHz, and 1.38–1.71 GHz with a size of $0.42\lambda _{0}\times 0.42\lambda _{0}\times 0.014\lambda _{0}$ (maximum wavelength). The realized gain in triband is −7.6 to −5.9, 4.7–5.4, and 4.7–5.9 dBi, respectively. For a 6 cm-thick FR-4 substrate combined with shorted metal columns, the triband conformal antenna has the potential on serving as a vehicle roof to bear the load, and it is attractive in vehicle communication too. [ABSTRACT FROM AUTHOR]

A Ku-band electronic 2-dimensional (2-D) beam-scanning transmitarray employing a new reconfigurable dual-layer Huygens element is developed in this article. The Huygens element consists of two metallic crosses printed on two layers of a dielectric substrate, which enables a near nonreflection Huygens resonance. A 1 bit phase compensation with low transmission loss is realized by controlling two p-i-n diodes on the element. Compared with many other reconfigurable transmitarray elements using multilayer structures with metallic vias, the proposed reconfigurable Huygens element has a much simpler configuration with a simpler biasing network, and it is not affected by multilayer alignment errors. This particularly facilitates large aperture array development at higher frequencies. To validate the design concept, an electronically reconfigurable transmitarray with the proposed element is fabricated at 13 GHz. Good agreement between the measured and simulated results is found, showing 2-D scanning beams within ±50° in the E-plane and ±40° in the H-plane with a maximum realized gain of 18.4 dBi. [ABSTRACT FROM AUTHOR]

In this letter, a direction-finding compensation method of nonideal modulation pulse for direction finding with the time-modulated array is investigated. With the transmission signal's increasing bandwidth, the conventional rectangular pulse cannot effectively describe the practical modulation pulse envelope shape, which will introduce the direction-finding error caused by the different harmonic characteristics. For compensating the error, a modeling method for the practical modulation pulse envelope shape is investigated and its harmonic expression is also deduced. Compared with the direction-finding method considering the rectangular pulse, numerical simulation, and experiment results are provided to verify the effectiveness of the proposed compensation method. [ABSTRACT FROM AUTHOR]

Frequency-multiplexing metasurfaces are typically attributed to the integration of multiple resonators, where mode coupling may significantly affect their performances. In this communication, we develop a dispersion-assisted dual-phase hybrid strategy for dual-frequency independent control of amplitude and phase with a single resonance. Therein, the frequency and phase decoupling can be achieved by precise dispersion control between two frequency states, while the amplitude distribution of each meta-atom can be controlled by properly allocating the energy of copolarized and cross-polarized waves. As a proof of concept, a bi-functional meta-mirror shaping multifocal points at two different frequencies have been experimentally demonstrated. The measured results are in good agreement with simulated results, showing the diffraction efficiencies (DEs) of 38% and 45%, and a signal-to-noise ratio (SNR) of 8.36 and 10.35 at $f_{1}$ and $f_{2}$ , respectively. In addition, another three meta-mirrors with tailorable amplitudes at dual frequencies are designed to further verify our strategy. This method offers an alternative platform for designing high-performance devices with dual-frequency wavefront manipulations, which may find potential applications in microwave integrated systems and wireless communication systems. [ABSTRACT FROM AUTHOR]

A novel low-profile phased antenna with dual-port and its two types of 1-D linear array to 2-D space wide-angle beam scanning are proposed. The antenna unit is composed of fishbone structure and rhombus parasitic patch, which is folded into n-shaped to low profile $0.08\lambda $. By adjusting the phase difference ($\Delta \varphi$) from 0° to 180°, the antenna working mode is changed from even mode to hybrid mode and to odd mode eventually. Therefore, the proposed antenna unit realizes wide-angle scanning characteristics and continuous switching state from broadside lobe to endfire lobe. Furthermore, the proposed phased antenna element is extended to two kinds of 1-D linear phased array (Array#1 and Array#2) based on the generalized principle of the pattern multiplication. The fabricated Array#1 can realize beam scanning range $- 116^{\circ }< \theta _{\mathrm {m}} < 0^{\circ }$ (xo z plane), $0^{\circ }< \theta _{\mathrm {m}} < 63^{\circ }$ (yo z plane), and $90^{\circ }< \Phi _{\mathrm {m}} < 169^{\circ }$ (xoy plane) and the fabricated Array#2 can achieve $0^{\circ }< \theta _{\mathrm {m}} < 60^{\circ }$ (xo z plane), $0^{\circ }< \theta _{\mathrm {m}} < 65^{\circ }$ ($\text{y}{o}\text{z}$ plane), and $90^{\circ }< \Phi _{\mathrm {m}} < 152^{\circ }$ (xoy plane). The proposed phased antenna unit and its 1-D array can realize 2-D space wide-angle scanning, improving scanning performance and expanding scanning dimensional space in phased array. [ABSTRACT FROM AUTHOR]

A 2-D scanning phased array with large element spacing using pattern reconfigurable stacked patch antenna at Ka-band is presented. The pattern reconfigurable stacked patch antenna is composed of four patches on the top integrated with four p-i-n diodes and a driven patch on the lower layer, where the top patches are located along the diagonals of the proposed antenna. By switching the reverse/forward bias states of p-i-n diodes, the phase gradients in different directions are generated and beam steering on the E-, D-(diagonal), and H-planes can be delivered. Subsequently, a 2-D scanning $4\times 4$ phased array with large element spacing is proposed by applying the pattern reconfigurable stacked patch antenna. The 2-D space is divided into nine subsets and covered by nine states of the proposed antenna. The measured results show that a scanning range of ±55° on the E-, D-, and H-planes can be provided. The maximum realized gain is 20.9 dBi at 26.5 GHz with an aperture efficiency of 62.0%. Compared with conventional half-wavelength phased array, the complexity and cost can be reduced for 2-D scanning phased array by introducing the proposed pattern reconfigurable stacked patch antenna. [ABSTRACT FROM AUTHOR]

In this letter, a 1-thru deembedding method for one-port microwave device characterization is presented. Only one standard “thru” is used in the proposed deembedding process. Reliable device models can be developed by the proposed method for EM/circuit cosimulation. The proposed method is verified by the deembedding process of a surface-mount p-i-n diode. Furthermore, the deembedded results are utilized in the EM/circuit cosimulation of a reconfigurable filter. The reconfigurable filter is fabricated and measured for verification. Good agreement is achieved between the experimental and simulated results. [ABSTRACT FROM AUTHOR]

An m-shapedspoof surface plasmon polaritons (SSPPs) structure as well as its application into end fire antenna with vertical polarization, low profile and compact size are proposed to be conformal with vehicle shell. Beside the primary odd SSPPs mode in the center, extra even mode at the top horizontal arms and odd mode at the end of the arms are introduced through folded arms. Consequently, the end-fire pattern can be adjusted by varying the aperture size. The multiple modes of SSPPs structure enable the antenna to operate in dual bands. The 1st mode operates from 447 to 515 MHz while the 2nd mode works from 0.97 GHz to 1.81 GHz simultaneously in simulation. The profile of the manufactured prototype antenna is merely 0.1 ${{\rm{\lambda }}_0}$ (@ 487 MHz). It achieves a measured gain peak of 8.4 dBi with HPBW 111.9 $^\circ $ in the 1st mode around 500 MHz and gain peak of 9.2 dBi at 1.6 GHz in the 2nd mode. It can be a very promising candidate for conformal antenna being embedded into the thin shell to high load bearing application on the high-speed vehicles for mobile communication. [ABSTRACT FROM AUTHOR]

An improved modulation module for beam steering in time-modulated array (TMA) is presented and investigated. The general improved module deploys parallel submodules consisting of several delay lines and imposes proper time delay to each submodule, enabling simultaneous improvement of modulation efficiency and allowed radio frequency (RF) signal bandwidth when utilizing the first positive harmonic for beam steering. Analysis of equivalent time sequence, modulation efficiency, and allowed signal bandwidth are provided, followed by several simulations of signal transmission and harmonic beam steering. Compared to the state-of-the-art TMAs, the proposed module shows obvious advantages on the modulation efficiency, especially on the remarkable allowed signal bandwidth when considering the limit of switching speed in RF switches. [ABSTRACT FROM AUTHOR]

An elevation and azimuth direction-finding (DF) method is presented by introducing the pattern reconfigurable antenna (PRA) into a two-element array. An equivalent multidimensional array is built by the two-element PRA array with switchable beams of same or opposite directions. With the introduction of same- and opposite-direction modes of PRAs, the elevation and azimuth angles are estimated by the methods of time-modulated array (TMA) and amplitude comparison, respectively. Meanwhile, a 2-D lookup table is built to correct the coning-error effect of the amplitude comparison. Compared with the conventional 2-D DF method with two orthogonal linear arrays, only a single linear array with not less than two elements is needed in the proposed method. Hence, it has the advantages of simple structure, compact size, and low cost. Simulated results are provided to verify the proposed 2-D DF method, and an S-band two-element PRA array is constructed to demonstrate its experimental feasibility. [ABSTRACT FROM AUTHOR]

This communication presents a gain-equalized $K_{a}$ -band Rotman lens-fed antenna by using phase gradient transmission lines (PGTLs). With PGTLs, the variation trend of the output progressive phase differences among the feeding ports is inverted. The aperture loss of the planar antenna array is then partially compensated by the efficiency of the lens when performing a wide-angle beam scanning. Hence, gain equalization is achieved among multiple beams with an acceptable gain degradation. To reduce the total size, the Rotman lens with PGTLs, the feeding networks, and the antenna array are stacked vertically. Meanwhile, the feeding network is implemented with substrate integrated coaxial lines, suppressing the parallel-plate mode inside the multilayer structure. In order to validate the proposed design, a compact Rotman lens-fed antenna operating at 24.75–27.5 GHz (FBW = 10.5%) is designed and fabricated. The results show that the gain drop of the Rotman lens-fed multibeam antenna is reduced from 4.4 to 1.5 dB at the design frequency of 26 GHz, covering a wide angular range between ±56°. [ABSTRACT FROM AUTHOR]

While electromagnetic (EM) metasurfaces have been extensively studied for wavefront manipulations, the real 3-D manipulation of wavefront remains challenging. In this article, an advanced strategy of noninterleaved multitasked metaplexer for 3-D manipulation of dual-helical EM wavefronts is reported. We first develop a general method to derive the metasurface phase distribution required to form the desired 3-D electric field patterns. Then, the spin-decoupled meta-atoms are designed to achieve this goal and further increase the degrees of freedom in EM manipulation. As a proof of concept, cascaded multiplane digital images in the propagation direction are employed as the 3-D wavefronts, which are encoded into the spin-decoupled meta-atoms array, making the outputting circularly polarized waves carrying different image information at different planes. Both the simulations and experiments verify the desirable 3-D wavefront manipulation capacities of our strategy for dual-helical states. Besides, this scheme can be further extended to achieve arbitrary energy allocation in 3-D space for dual-helical EM waves. Our strategy paves an alternative route for applications such as multiple-input multiple-output (MIMO) communications, multitarget radar detection, information storage, as well as 3-D microwave imaging. [ABSTRACT FROM AUTHOR]

A grating lobe suppression approach based on the null scanning antenna (NSA) for a sparse phased array is proposed. The NSA provides continuous null scanning and beam steering on two orthogonal planes, by connecting four varactor loaded impedance reconfigurable circuits to the four edges of a square patch antenna, respectively. The NSA is introduced into a sparse phased array and the grating lobe is suppressed by keeping the radiation pattern null of NSA pointing at the angle of the grating lobe during beam scanning. Meanwhile, the beam direction of NSA is steered to a wider angle with the variation of null angle. The main lobes during beam scanning are located within the 3 dB beamwidth of NSA. Thus, the sidelobe level (SLL) and scan loss over the wide scanning region are improved considerably. A $2\,\,\times \,\,4$ sparse phased array with NSA is designed and measured for verification. Both simulated and measured results indicate that the SLL of the sparse phased array with NSA can be suppressed below −9.3 dB within the scan range from −76° to 75°. The maximum realized gain during beam scanning is 17 dBi, with an aperture efficiency of 69.86% and a maximum gain fluctuation of 4.4 dB. [ABSTRACT FROM AUTHOR]

A novel dual-port phase antenna is proposed to realize 2-D scanning. The antenna consists of two monopoles on both sides and a fishbone structure in the middle. By changing the phase difference ${\Delta \varphi }$ between two monopoles, energy is coupled to the proposed structure, exciting different degrees of superposition of even and odd modes. The continuous switching from the broadside lobe to the end-fire lobe is realized, and it has the characteristic of 2-D scanning. Furthermore, to provide an in-depth insight into the 2-D scanning mechanism, two linear arrays (Array 2 and Array 3) based on the proposed antenna element and a generalized principle of pattern multiplication (GPPM) are developed. The fabricated Array 2 can offer scanning angles of 0°–73° along the $\theta $ -direction with the gain of 6.5–10.4 dBi and 90°–140° along the $\Phi $ -direction with the gain of 6.1–11.7 dBi. Its scanning coverage of 3 dB beamwidth is $0^{\circ } < \Phi < 140^{\circ }$ , $0^{\circ } < \theta < 90^{\circ }$. The manufactured Array 3 can scan 0°–90° along $\theta $ -direction with the gain of 8.2–11.1 dBi and 50°–90° along the $\Phi $ -direction with the gain of 6–9.36 dBi, and its 3 dB coverage of the main beam scanning is $0^{\circ } < \Phi < 180^{\circ }$ , $0^{\circ } < \theta < 90^{\circ }$. Consequently, the proposed antenna and GPPM can be readily extended to wide-angle scanning phased arrays. [ABSTRACT FROM AUTHOR]