In this article, a dual-polarized planar phased array with high polarization isolation and low cross-polarization is presented operating from 4 to 18 GHz, i.e., 4.5:1. The proposed array is comprised of tightly coupled dipoles with integrated coupled-Marchand baluns. To improve the uniformity of fields distributed on the array, the center-feeding dipole is used in this design instead of the conventional edge-feeding one at first. Then, the outer conductors of the feed are composed of a group of shorted vias with the proper number and position. Based on these methods, the output balance of the balun is significantly improved, resulting in high isolation between ports with different polarization modes. Furthermore, this feed has a natural ability to suppress the D-plane common mode resonance. The capacitive metallic annular plate over adjacent radiating elements and the thick aluminum plate with an air cavity placed under the array are employed together to suppress the in-band coupled-loop modes. The infinite array simulation indicates that the array can achieve transmit (Tx)/receive (Rx) isolation more than 48 dB at broadside. Isolation better than 32 and 30 dB can be achieved when scanning to 45° in E-/H-planes and 60° in E-plane, respectively. The cross-polarization level is below −54 dB at broadside and remains below −29 dB when scanning to 60° in E-plane as well as 45° in H-plane. A $12\times12$ dual-polarized antenna array is fabricated and measured to validate the correctness of this design. This type of antenna can be applied in wideband simultaneous transmit and receive (STAR) monostatic systems.

Planar Ultra-Wideband and Wide-Scanning Dual-Polarized Phased Array With Integrated Coupled-Marchand Balun for High Polarization Isolation and Low Cross-Polarization

In this article, an ultra-wideband and wide-angle insensitive absorber is proposed. The unit cell of the proposed structure consists of a tightly coupled dipole array (TCDA2) under another TCDA (TCDA1) that is twice the height of TCDA2 (TCDA-under-TCDA structure). TCDA1 of the unit cell acts as either a lossless (or lossy) antenna when the frequency is out of (or in) the operating frequency range of TCDA2. Reciprocity is applied to design TCDA1 as an absorber when the frequency is out of the operating frequency range of TCDA2 (lossless antenna region). On the other hand, the multisection impedance matching technique is applied for TCDA1 to be an absorber when the frequency is in the operating region of TCDA2 (lossy antenna region and reciprocity cannot be applied). In addition, a metasurface (MS) and vertical metal strip (VMS) are employed to develop the wide-angle insensitivity absorber. A −10 dB reflection bandwidth of 0.63–6.55 (10.4:1) is achieved with a $0.126\lambda _{\mathrm {low}}$ at the lowest operating frequency under normal incidence. The bandwidth is moderately reduced to 0.69–6.75 (9.78:1) with a $0.138\lambda _{\mathrm {low}}$ for the TE mode and 0.75–6.22 (8.29:1) with a $0.150\lambda _{\mathrm {low}}$ for the TM mode under 45° oblique incidence. The measured results of the fabricated absorber using the transverse electromagnetic (TEM) cell are in good agreement with the simulated results.

Ultra-Wideband and Wide-Angle Insensitive Absorber Based on TCDA-Under-Tightly Coupled Dipole Array

A dual-polarized ferrite-loaded ultrawideband tightly coupled dipole array (TCDA) with an extremely low profile is presented. A novel ferrite grid with high relative permeability and permittivity characteristic is loaded between the antenna and the ground plane, which expands the low-end of operation bandwidth and reduces the overall profile, simultaneously. An X-shaped frequency selective surface (FSS) is utilized as a special band-stop filter to improve the realized gain at higher frequencies. Meanwhile, the proposed array utilizes a microstrip (MS) to coplanar stripline (CPS) uniplanar double-Y balun to achieve unbalance&#x2013;balance transformation and impedance matching. A thin meta-surface-based wide-angle impedance matching (MS-WAIM) layer is introduced to improve the beam-scanning ability. Simulated results show that the proposed antenna is able to operate over a 10:1 bandwidth (0.2&#x2013;2 GHz) with active VSWR &#x003C; &#x0007B;2, 2.6, 3.4&#x0007D; while scanning up to &#x0007B;broadside, 45&#x00B0;, 60&#x00B0;&#x0007D;, respectively. Most of all, the overall antenna profile is only 62.5 mm (<inline-formula> <tex-math notation="LaTeX">$0.042\lambda _{\mathrm {L}}$ </tex-math></inline-formula>) at the lowest operating frequency, which is known to be the thinnest 10:1 ultrawideband array with wide angle scanning (&#x00B1;60&#x00B0; in E- and H-plane) performance. A prototype of <inline-formula> <tex-math notation="LaTeX">$6 \times 8$ </tex-math></inline-formula> array is simulated, fabricated, and measured. Good agreement is achieved between the simulated and measured results. 

A Ferrite-Loaded Ultralow Profile Ultrawideband Tightly Coupled Dipole Array

A low-profile, wide-scan antenna array operating in the 6–12 GHz band with planar and conformal variants is reported in this letter. The design comprises capacitively coupled dipoles, integrated with an artificial magnetic conductor layer to achieve a low profile ( h ). A patch with feed via is used as a conventional feed balun. In addition, a via fence is employed for resonance mitigation and improved impedance matching at the lower end of the frequency band. The array exhibits a wide-angle scan capability (±60°) in E-, H-, and D-plane for active voltage standing wave ratio (VSWR) h ) and 8 × 8 planar array configurations, is simulated and analyzed. The measurement results of the conformal array prototype show good agreement with the simulations in terms of VSWR, radiation pattern, and realized gain. Therefore, the proposed design is an attractive candidate for planar and conformal wireless devices at C , X -band frequencies.

A Low-Profile, Wide-Scan, Cylindrically Conformal X -Band Phased Array

Within the context of modern digital phased array (DPA) radios, differential Radio Frequency (RF) front-ends provide much greater immunity to noise and distortion by suppressing second order harmonics. Recent advancements in differential RF front-ends offer high dynamic range, high linearity, and low noise in the transceiver chain. However, a major roadblock to fully differential systems is the presence of common-mode resonances. In this article, we present a novel wideband differential feed for dipole arrays that overcomes this bottleneck. Our dipole array is developed for the L-S band ( viz. 1.05 GHz to 3.2 GHz) with emphasis on dual-linear polarization and resonance-free scanning to low angles. The novelty of this article is the Balanced Wideband Impedance Transformer (BWIT) feed that mitigates common-mode currents across the entire band while scanning to low angles. Array simulations are verified with measurements of an $8\times 8$ prototype in a volume of 384mm $\times 384$ mm $\times 57$ mm. The array achieves resonance-free scanning across a 3:1 impedance bandwidth with VSWR $\theta = 0^{\circ }$ (Broadside), 45° (D-plane), 60° (E-plane) and across a 2.37:1 impedance bandwidth with VSWR < 3 for the case of 45° (H-plane). Measured gain achieves near-theoretical values across the operating band.

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Wideband Dipole Array With Balanced Wideband Impedance Transformer (BWIT)

An ultrawideband, tightly coupled balanced antipodal dipole array (TC-BADA) with low cross-polarization characteristic is presented. The proposed array achieves a low cross-polarization level by printing a pair of tightly coupled antipodal dipoles on two substrates to form a balanced radiating structure. The antenna elements are fed by a tapered balun with six pairs of vias placed at the balun edges. A meta-surface-based wideangle impedance matching (MS-WAIM) layer is designed based on the equivalent circuit model and current distribution, which improves the beam scanning ability and reduces the antenna profile simultaneously. The simulated results show that the proposed TC-BADA is able to operate over a 5:1 bandwidth (2.05–10.3 GHz) with active VSWR $0.51\lambda _{\mathrm {H}}$ at the highest operating frequency. A prototype of $16 \times 16$ array is fabricated and the central 8 $\times $ 8 elements are measured. Good agreement is achieved between the simulated and measured results.

Low Cross-Polarization Ultrawideband Tightly Coupled Balanced Antipodal Dipole Array

The invention discloses a dual-polarization strong-coupling ultra-wideband phased-array antenna loaded with an electromagnetic metamaterial. The antenna comprises a strong-coupling folding dipole unit, a feed balun, a metamaterial wide-angle impedance matching layer, a microstrip transition line and a reflection floor, wherein the tail end of the strong-coupling folding dipole unit is slotted forfacilitating the dual-polarization design. A dipole and the designed feed balun are integrated on the same dielectric substrate, and the bottom of the dipole and the bottom of the designed feed balunare vertically embedded in the reflection floor; the wide-angle impedance matching layer is arranged at the top of the strong-coupling dipole unit, and the lower part completes the coaxial electric connection with the balun by bending the microstrip transition line, thereby achieving the impedance matching effect at the same time. The dual-polarization characteristic is achieved through the careful design of the tail end of the dipole, and a strong coupling folded dipole form is introduced; a novel wide-angle impedance matching layer structure is loaded to achieve the physical characteristicsof low profile and light weight and the excellent radiation performance of ultra wide band, low cross polarization and the like.

Dual-polarization strong-coupling ultra-wideband phased-array antenna loaded with electromagnetic metamaterial

The invention discloses a low-cross-polarization ultra-wideband strong-coupling opposite-dipole phased array antenna. The antenna comprises an opposite strong-coupling dipole unit, an impedance matching layer and a reflection ground plate; the bottom of the opposite strong-coupling dipole unit is vertically embedded in the reflection ground plate; and the impedance matching layer is arranged at the top of the opposite strong-coupling dipole unit and is parallel to the reflection ground plate. According to the low-cross-polarization ultra-wideband strong-coupling opposite-dipole phased array antenna of the invention, two dielectric substrates and the opposite-dipole structure are adopted, so that the intrinsic defect of low cross polarization of a traditional vertical strong coupling phasedarray antenna can be eliminated; unique metal vias are designed at feed Balun portions connected with two dipole patches so as to suppress the resonance of the array at high frequencies and improve the degree of isolation between array units to some extent; and the open-loop metamaterial wide-angle impedance matching layer at the upper part of the antenna is adopted to replace a traditional puredielectric wide-angle impedance matching layer, and therefore, the antenna of the invention has the advantages of light weight, easiness in realizing conformality, modularity and the like.

Low-cross-polarization ultra-wideband strong-coupling opposite-dipole phased array antenna

In this paper, an ultra-wideband long slot antenna array based on a novel artificial magnetic conductor (AMC) with air substrate is proposed. The proposed antenna is intended to operate in a wide frequency band (0.9-2.4GHz), which utilizes a carefully designed AMC reflector to achieve low profile property (about 0.22λ height at 2.4 GHz). An air substrate is introduced in the design procedure of AMC reflector to widen the in-phase reflection bandwidth. Simulation result shows that this antenna is able to realize a 2.67:1 bandwidth (VSWR<3) while scanning to ±45°. Owing to the attractive wide bandwidth and low-profile configuration, the proposed antenna is potential to apply on radar and communication systems.

Low-Profile Wideband Long Slot Phased Arrays Based on Novel AMC Reflectors

The invention discloses a wing-borne low-scattering ultra-wideband conformal phased array based on a strong coupling effect. The whole antenna structure of the array is subjected to conformal processing, and +/-45 degree scanning in the arraying direction is realized within a broadband of 0.5-2GHz. Compared with the traditional planar ultra-wideband phased array, the phased array disclosed by theinvention has significant low-scattering characteristics inside and outside the working band of the antenna. The whole antenna structure mainly includes a coaxial feeding structure of an antenna radiation unit, a gradient line balun used for connecting an antenna radiation patch and the feeding structure, a metal ground plate which is conformal with a flight carrier, a parasitic metal block located on the metal ground plate, a conformal dielectric substrate used for supporting the radiation structure of the whole phased array, connected long-slot conformal radiation patches based on the strongcoupling effect, a conformal dielectric substrate used for supporting a resistive electromagnetic metamaterial, a circular resistive electromagnetic metamaterial with an ultra-wideband electromagnetic wave absorbing effect and parasitic slots on both sides of the antenna radiation unit.

Bingjun Wang

Papers

Low Cross-Polarization Ultrawideband Tightly Coupled Balanced Antipodal Dipole Array

Dual-polarization strong-coupling ultra-wideband phased-array antenna loaded with electromagnetic metamaterial

Low-cross-polarization ultra-wideband strong-coupling opposite-dipole phased array antenna

Low-Profile Wideband Long Slot Phased Arrays Based on Novel AMC Reflectors

Wing-borne low-scattering ultra-wideband conformal phased array based on strong coupling effect