Transmission Phase Range Research Articles

Realization of Focused Beam and Shaped Beam Transmitarrays Based on Broadband Unit Cells

A focused beam and a shaped beam four-layer transmitarray (TA) antenna operating in the $K$ -band have been designed, fabricated, and measured. Four-layer unit cells allowing a transmission phase range of 360° are used. The gain of the beam-focusing TA is 30.3 dB at 19 GHz with an aperture efficiency of 34.9%. Compared with TAs proposed in the literature, the presented antenna bandwidth is almost two times larger with a −1 dB gain bandwidth of 18% and a −3 dB gain bandwidth of 25.5%. A second TA radiating a shaped beam was designed, and its measured pattern correlates well with theoretical calculations. The sensitivity of the proposed unit cells to fabrication errors and the effect of oblique incidence are also studied.

Analysis and Design of Transmitarray Antennas

In recent years, transmitarray antennas have attracted growing interest with many antenna researchers. Transmitarrays combines both optical and antenna array theory, leading to a low profile design with high gain, high radiation efficiency, and versatile radiation performance for many wireless communication systems. In this book, comprehensive analysis, new methodologies, and novel designs of transmitarray antennas are presented. Detailed analysis for the design of planar space-fed array antennas is presented. The basics of aperture field distribution and the analysis of the array elements are described. The radiation performances (directivity and gain) are discussed using array theory approach, and the impacts of element phase errors are demonstrated. The performance of transmitarray design using multilayer frequency selective surfaces (M-FSS) approach is carefully studied, and the transmission phase limit which are generally independent from the selection of a specific element shape is revealed. The maximum transmission phase range is determined based on the number of layers, substrate permittivity, and the separations between layers. In order to reduce the transmitarray design complexity and cost, three different methods have been investigated. As a result, one design is performed using quad-layer cross-slot elements with no dielectric material and another using triple-layer spiral dipole elements. Both designs were fabricated and tested at X-Band for deep space communications. Furthermore, the radiation pattern characteristics were studied under different feed polarization conditions and oblique angles of incident field from the feed. New design methodologies are proposed to improve the bandwidth of transmitarray antennas through the control of the transmission phase range of the elements. These design techniques are validated through the fabrication and testing of two quad-layer transmitarray antennas at Ku-band. A single-feed quad-beam transmitarray antenna with 50 degrees elevation separation between the beams is investigated, designed, fabricated, and tested at Ku-band. In summary, various challenges in the analysis and design of transmitarray antennas are addressed in this book. New methodologies to improve the bandwidth of transmitarray antennas have been demonstrated. Several prototypes have been fabricated and tested, demonstrating the desirable features and potential new applications of transmitarray antennas.

All-Metal Transmit-array for Circular Polarization Design Using Rotated Cross-Slot Elements for High Power Microwave Applications

Transmit-array (T-A) design for circular polarization made by all metal is presented in this communication. The proposed T-A consists of numerous cross-slot elements. The simulation results indicate that rotating the cross slot on the element, a full transmission phase range of 360° can be achieved for a transmission magnitude better than −0.6 dB at 9.375 GHz. A T-A has been designed, simulated, and measured in x-band. The measurement results show that the T-A can radiate the wave in the desired direction with an enhanced gain. They are in agreement with the theoretical and simulation results. Furthermore, the all-metal T-A presented in this communication has the application potentials for high-power microwave applications.

Novel High-Gain Circularly Polarized Lens Antenna Using Single-Layer Transmissive Metasurface

Abstract A high-gain lens antenna employing single-layer focusing metasurface (MS) is proposed in this article. The single-layer element achieves a 360° transmission phase range with a transmission magnitude better than 0.9. And the focusing MS consists of 169 elements was designed by utilizing the technique of varying rotation angle to compensate the phase delay. Thus, a lens antenna is constructed by placing a circularly polarized (CP) patch antenna at the focal point of the MS. The fabricated lens antenna demonstrates a good performance of 4.6 % 3-dB axial ratio bandwidth and 6 % 1-dB gain bandwidth, respectively. Moreover, the maximum gain is 18.3 dBic at 15 GHz, which is enhanced by 11.4 dBic compared with the patch antenna. Due to the single-layer structure, this design has a low profile and easy fabrication process compared with the conventional designs, making it an attractive alternative to compact high-gain antenna.

A COMPACT AND WIDEBAND FLAT LENS ANTENNA BASED ON APERTURE COUPLED PATCHES FOR X-BAND APPLICATIONS

This paper presents a wideband and compact flat lens antenna for X-band applications. An 8×8 array of this antenna is designed and realized by using aperture coupled patches from the multilayer Frequency Selective Surface concept. The basic antenna element configuration of this design consists of two back-to-back printed patches with a common ground plane coupling. A pair of identical slots is embedded on the ground plane to provide the necessary phase error compensation between receive and transmit apertures. The lengths of the two slots are varied simultaneously to investigate how much phase shift range can be achieved with this simple design structure. The antenna elements are simulated using the electromagnetic simulation software CST Microwave Studio. A 209° transmission phase range was achieved with transmission coefficient variations of better than -2.25 dB. The gain of the feeding horn antenna used is 9 dB at 10 GHz. Upon the implementations of the lens structure, the gain of the overall antenna system has increased to 16 dB. Our simulation shows a 3-dB transmission bandwidth of around 33% could be achieved for the unit cell. Radiation pattern simulation of the antenna system shows a good symmetry between E and H-plane with a half-power beamwidth of 19.2° and 19.0° in E-plane and H-plane respectively. The gain is greater than 9 dB from 8 to 12 GHz with maximum gain of 16 dB is achieved at 10 GHz. The proposed antenna design uses a simple and less fabrication complexity mechanism for phase error correction.

A WIDEBAND TRANSMITARRAY USING DOUBLE-PETAL LOOP ELEMENTS

In this letter, a four-layer transmitarray operating at 9.5 GHz is designed using a double- petal loop element as the unit cell. A configuration of the double-petal loop elements is used to increase transmission phase variation while maintaining a wide transmission magnitude bandwidth of the unit cell, and a full transmission phase range of 360 ◦ is achieved for a transmission magnitude equals to or better than −2.4 dB. Furthermore, the oblique performance of the unit cell is also good. Then, a prime- focus 676-element microstrip transmitarray with the proposed element is fabricated and measured. The highest measured gain is about 22.15 dBi at 9.8 GHz, resulting in a 31% aperture efficiency. The antenna bandwidth of 10.2% (from 9.3 to 10.3 GHz) for 1-dB gain is achieved in this design.

Bandwidth Improvement Methods of Transmitarray Antennas

Despite several advantages of planar transmitarray antennas compared to conventional lens antennas, they have a narrow bandwidth. The goal of this paper is to improve the bandwidth of transmitarray antennas through the control of the transmission phase range and the optimization of the phase distribution on the transmitarray aperture. To validate the proposed approaches, two quad-layer transmitarrays using double square loop elements have been designed, fabricated, and tested at Ku-band. The transmission phase distribution is optimized for both antennas, while they differ only in the transmission phase ranges. It is shown that the transmitarray antennas designed using the proposed techniques achieve 1-dB gain bandwidth of 9.8% and 11.7%, respectively. The measured gains at 13.5 GHz are 30.22 and 29.95 dB, respectively, leading to aperture efficiencies of 50% and 47%, respectively.

Transmission Phase Limit of Multilayer Frequency-Selective Surfaces for Transmitarray Designs

Many transmitarray antennas are designed with multilayer frequency-selective surface (M-FSS) type elements. The goal of this paper is to reveal the transmission phase limit of M-FSS for transmitarray antenna designs. An analytical study of the transmission coefficient of multiple conductor layers separated by dielectric materials has been carried out, and the maximum transmission phase range has been determined according to the number of layers, substrate permittivity, and separation between conductor layers. It is revealed that the -1-dB transmission phase limits are 54°, 170°, 308°, and full 360 °for single-, double-, triple-, and quad-layer FSS consisting of identical layers, respectively. Furthermore, it is shown that if -3-dB criteria is used, a triple-layer FSS is sufficient to achieve the full 360 ° phase range. The effectiveness of the analytical study has been validated through numerical simulations of several representative FSS examples.

High-Gain and Broadband Transmitarray Antenna Using Triple-Layer Spiral Dipole Elements

A triple-layer transmitarray antenna has been designed, fabricated, and tested at X-band. Using a spiral-dipole element, a full transmission phase range of 360 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> is achieved for a transmission magnitude equal to or better than -4.2 dB. The transmission phase distribution of the transmitarray elements has been optimized to reduce the effects of the lossy elements with low transmission magnitudes on the antenna gain, leading to an average element loss as low as 0.49 dB. The measured gain of the transmitarray prototype is 28.9 dB at 11.3 GHz, resulting in a 30% aperture efficiency. Antenna bandwidths of 9% for 1-dB gain and 19.4% for 3-dB gain are achieved in this design.