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A reconfigurable transmitarray antenna (RTA) with 360° continuous transmission phase controlling capability is designed and experimentally validated in this letter. The proposed RTA element is based on the receiver-transmitter structure. A compact varactor-based analog phase shifter using a coupled-line structure is utilized to provide a 0° to 180° continuous transmission phase. Two PIN diodes integrated on the active transmitter patch are alternatively turned on to generate an additional 180° phase shift using the current reversal mechanism. The element simulations show a magnitude insertion loss varying from 0.95 to 1.35 dB at 5.6 GHz, and a wide 3-dB transmission bandwidth of 16.7%. A prototype composed of ${\rm{16 \times 16}}$ elements is fabricated and measured. The measured broadside gain is 23.7 dBi at the design frequency with a 3-dB gain bandwidth of 15.7%. Good two-dimensional (2-D) beam steering capability within ±60° is also experimentally verified. [ABSTRACT FROM AUTHOR]

A 1 bit reconfigurable reflectarray antenna with independent dual-band phase controlling and large-angle beam scanning capabilities is designed and experimentally verified. By exploiting polarization orthogonality, the proposed element achieves 1 bit phase shift at 12.5 GHz for x-polarization and at 14.25 GHz for y-polarization with only two p-i-n diodes in each element. The element structure and biasing circuits are optimized. Low element magnitude loss, cross polarization, and out-of-band interference are verified. A prototype with 256 elements is fabricated and tested. The measured gains are 22.3 dBi at 12.6 GHz and 22.5 dBi at 14.25 GHz, respectively. 2-D scanned beams up to ±60° at both frequencies are measured to demonstrate the independent dual-band beam scanning capability. The proposed design can transmit and receive orthogonally polarized signals simultaneously and is believed to be a promising candidate for the point-to-point full-duplex mobile communication applications. [ABSTRACT FROM AUTHOR]

A novel 1 bit reconfigurable transmitarray antenna (RTA) using an equivalent magnetic dipole element for wide-angle beam scanning at Ku-band is presented. The RTA element consists of a rectangular patch and a side-shorted patch with an equivalent magnetic dipole radiation. A 1 bit phase difference is achieved by controlling two p-i-n diodes on the side-shorted patch based on the current reversal mechanism. The half-power beamwidth of the presented antenna element is 142° in E-plane, which is significantly larger than other conventional elements. A RTA prototype with $16\times16$ elements is designed, fabricated, and tested. The measured results show good beam scanning capabilities of the 1 bit RTA. The measured gain in the broadside direction is 21.4 dBi, and the scan gain loss is 3.6 dB for the 60° scanned beam in E-plane. [ABSTRACT FROM AUTHOR]

A shared aperture quad-band high-gain reflectarray antenna (RA) is proposed. It has a stacked structure consisting of a Ka-band dual-band circularly polarized RA, a Ku-band wideband linearly polarized RA, and a triband double-screen frequency-selective surface in between. It is able to simultaneously transmit and receive signals at both Ku- and Ka-bands. A prototype with a circular aperture of 400 mm in diameter is designed, fabricated, and tested for experimental verification. The measured gains are 31 dBi at 12.5 GHz, 32 dBi at 14.25 GHz, 36.1 dBic at 20.4 GHz, and 39.4 dBic at 30.2 GHz, respectively, and the corresponding aperture efficiencies are 45.6%, 44%, 56%, and 54.8%, respectively. The radiation performance demonstrated in this communication validates the feasibility of the proposed quad-band RA design for the future satellite communications at both Ku- and Ka-bands. [ABSTRACT FROM AUTHOR]

Combining a reflectarray and a transmitarray together, a novel array antenna with bidirectional high-gain beams is proposed in this paper. A novel single-layer metal-only defected square-ring slot element, which has a near-zero thickness, is introduced as the phasing element. Full 360° phase shift range is achieved by utilizing the cross-polarized field of the phasing element. As a bidirectional high-gain antenna (bi-HGA), a transmit-reflect-array using the proposed elements is then designed, fabricated, and measured. It is only composed of a thin metallic sheet with 420 mm side length, spatially fed by a corrugated horn. Well-defined pencil beams are formed in broadside directions on both sides. The measured gains of the transmitted and reflected beams at 10 GHz are 25.5 dBi with 15% 1 dB gain bandwidth and 25 dBi with 14% 1 dB gain bandwidth, respectively. The proposed bi-HGA exhibits distinctive advantages of being ultrathin $(0.0067\lambda _{0})$ , lightweight, and low cost without using dielectric substrates, and is a promising candidate for bidirectional wireless communication applications. [ABSTRACT FROM AUTHOR]

Design of a C-band reconfigurable reflectarray antenna (RRA) is presented. The RRA element consists of a fixed upper patch and a tunable slotted patch. By mechanically controlling the height of the slotted patch, the RRA element has a phase shift range of 324° with small element loss. A prototype with 408 elements is designed and fabricated. The measurements show that the gain of the 20° scanned beam is 25.7 dB and the aperture efficiency is 48.6%. The large-angle beam-scanning capability of the RRA is also verified within ±60° angular range, and well-defined scanned beams are obtained with maximum scan gain loss of 3.4 dB. [ABSTRACT FROM AUTHOR]

Design of a circularly polarized reconfigurable reflectarray antenna (RRA) at X band is presented. The RRA element employs concentric dual split rings, and can be mechanically rotated to obtain continuous 360° phase coverage with negligible element loss. A prototype with 15\times15 manually rotated elements is first computed, simulated, and measured. Full-wave simulations show that the gain of the beam focused in ( \theta =20^{\circ } , \varphi = 0^{\circ } ) direction is 25.8 dB and the 1-dB gain bandwidth is over 28.6%. The measured results show that the beam at ( \theta = 20^\circ , \varphi = 0^\circ ) direction achieves the maximum gain of 25.6 dB, corresponding to an aperture efficiency of 51.8%. The beam-steering capability of the RRA is measured within ±60° angular range, and well-defined scanned beams are obtained with maximum scan loss of 3.7 dB. The versatile beam-forming capability of the RRA is also verified by synthesizing a square shaped beam and a cosecant shaped beam. Another micromotor-controlled prototype with 756 elements on an octagonal aperture is fabricated and its measured radiation performance validates the feasibility of the proposed design as well. [ABSTRACT FROM PUBLISHER]

A novel design methodology for single-layer dual-band reflectarray antennas with wide frequency ratios is proposed by exploiting the unique reflection phase properties of Phoenix elements. Full 360° phase ranges at both frequency bands are achieved simultaneously by using only one element set. Compared to conventional approaches that use two sets of elements for dual-band operation, physical and electromagnetic mutual interferences between the elements operating at different frequency bands can be completely avoided. A detailed design procedure for single-layer dual-band reflectarrays with a wide frequency ratio up to 2.5 is presented, and a set of three center-fed dual-band reflectarrays operating at 15/10, 20/10, and 25/10 GHz, respectively, are designed and numerically verified using full-wave simulations. Furthermore, an offset-fed single-layer dual-band reflectarray operating at 20/10 GHz with a circular aperture of 400 mm in diameter is designed, fabricated, and tested for experimental verification. The measured gains are 36.1 dBi with an aperture efficiency of 58.0% at 20 GHz and 30.3 dBi with an aperture efficiency of 61.1% at 10 GHz, respectively. The measured 1-dB gain bandwidth is 9.1% and 14.0% at the upper and lower bands, respectively. Both the simulated and measured results successfully demonstrate the effectiveness of the proposed design methodology. [ABSTRACT FROM PUBLISHER]

An electronically reconfigurable reflectarray antenna (RRA) with 10\times10 elements is presented with a detailed design procedure for an improved beam-scanning performance. The element, designed at Ku band using a simple patch structure with one PIN diode and two substrate layers, can be electronically controlled to generate two states with 180° phase difference and low reflection loss. A reflectarray prototype is fabricated and experimentally studied for proof of principle. The limitations of the small aperture size are analyzed in detail, and synthetic optimizations of both feed location and aperture phase distribution are used to improve the beam-scanning performance of the prototype. Experimental results agree well with the full-wave simulations, and scan beams within {\pm}{50}^\circ range are obtained with a maximum aperture efficiency of 17.9% at 12.5 GHz. Consistent scan beams are obtained from 11.75 to 13.25 GHz. Furthermore, the versatile beam-forming capability of the RRA is also demonstrated by a wide-beam pattern synthesis. A fast beam-switching time (12\;\upmu \text{s}$) is theoretically analyzed and verified by the measurement. [ABSTRACT FROM PUBLISHER]

A novel slot-type phoenix element is proposed for low-cost metal-only reflectarray designs. Due to its unique rebirth capability, a full 360° phase coverage is obtained by the proposed phasing element, which can effectively resolve the phase range limitation commonly seen in slot-type metal-only reflectarray elements. A Ku-band offset-fed reflectarray prototype with a circular aperture of 516 mm in diameter is designed, fabricated, and tested for verification. The measured gain is 33.9 dBi at 12.5 GHz with the aperture efficiency of 53.8%, and the 1-dB gain bandwidth is 12.8%. The proposed metal-only reflectarray achieves good radiation performance and is suitable for high-gain antenna applications with stringent requirements on cost and/or working environment. [ABSTRACT FROM AUTHOR]

A novel transmitarray element consisting of only two layers of modified Malta crosses printed on a dielectric substrate is proposed, and vias are employed to augment the transmission magnitude and enhance its phase shift range. A prototype transmitarray with a circular aperture of 338 mm in diameter is then designed, fabricated, and tested to validate the proposed design. The simulation and measurement results show good radiation characteristics with measured gain of 33.0 dBi at 20 GHz and aperture efficiency of 40%. The proposed element considerably simplifies the complexity of a transmitarray, reducing its thickness, mass, and cost. [ABSTRACT FROM PUBLISHER]