Reconfigurable Reflectarrays and Array Lenses for Dynamic Antenna Beam Control: A Review

Advances in reflectarrays and array lenses with electronic beam-forming capabilities are enabling a host of new possibilities for these high-performance, low-cost antenna architectures. This paper reviews enabling technologies and topologies of reconfigurable reflectarray and array lens designs, and surveys a range of experimental implementations and achievements that have been made in this area in recent years. The paper describes the fundamental design approaches employed in realizing reconfigurable designs, and explores advanced capabilities of these nascent architectures, such as multi-band operation, polarization manipulation, frequency agility, and amplification. Finally, the paper concludes by discussing future challenges and possibilities for these antennas.Comment: 16 pages, 12 figure

Efficient Spectral Domain MoM for the Design of Circularly Polarized Reflectarray Antennas Made of Split Rings

The method of moments (MoM) in the spectral domain is used for the analysis of the scattering of a plane wave by a multilayered periodic structure containing conducting concentric split rings in the unit cell. Basis functions accounting for edge singularities are used in the approximation of the current density on the split rings, which makes it possible a fast convergence of MoM with respect to the number of basis functions. Since the 2-D Fourier transforms of the basis functions cannot be obtained in closed-form, judicious tricks (controlled truncation of infinite summations, interpolations, etc.) are used for the efficient numerical determination of these Fourier transforms. The implemented spectral domain MoM software has been used in the design of a circularly polarized reflectarray antenna based on split rings under the local periodicity condition. The antenna has been analyzed with our spectral domain MoM software, with CST and with HFSS, and good agreement has been found among all sets of results. Our software has proven to be around 27 times faster than CST and HFSS

Wideband Circularly Polarized Elements and Arrays for Wireless Systems

Circularly polarized (CP) antennas have received increasing interest during recent decades due to their unique features such as the mitigation of multi-path fading, reduction of the "Faraday rotation" effect when signals propagate through the ionosphere and immunity of the polarization mismatching between transmitting and receiving antennas. Due to the requirements of high date rate and large system capacity, CP antennas deployed in various wireless systems are always demanded to have wide bandwidth. Furthermore, other system requirements such as polarization diversity, wide-angle beam scanning and low power consumption impose additional requirements to CP antennas. Therefore, it is becoming a more stringent requirement to design wideband CP antennas with diverse features to fulfil the requirements of various wireless systems. In this thesis, six different types of wideband CP antenna elements and arrays are designed, fabricated and characterized to meet the different demands of wireless systems. Chapters 3-5 investigate three different types of wideband CP antenna elements while Chapters 6-8 investigate three different kinds of wideband CP array antennas. In Chapter 3, an ultra-wideband CP element with a bandwidth of 100% (3:1) is proposed. It over-comes the problem of limited 3 dB axial ratio (AR) bandwidth for single-feed CP antennas and achieves high front-to-back ratio (FBR) by using a novel ground plane with simple configuration, which makes it a good candidate for high-performance Global Navigation Satellite System (GNSS) receivers. Chapter 4 presents a wideband loop antenna with electronically switchable circular polarizations. It solves the issue of narrow overlapped bandwidth under different polarization states for a polarization reconfigurable CP antenna. Because of the available orthogonal polarizations across a wide bandwidth, this antenna can be deployed in wireless communications which implement polarization diversity. The third antenna element investigated in Chapter 5 tackles the difficulty of designing wide-band wide AR beamwidth CP antennas. It achieves wide AR beamwidth within a 42% bandwidth, which is suitable for wideband wide-angle CP beam-scanning applications. The second main part of this thesis focuses on the investigation of wideband CP arrays. In Chapter 6, a dual-CP beam-scanning array is investigated, which can scan its beam independently in right-hand circular polarization (RHCP) and left-hand polarization (LHCP) from 27 GHz to 30 GHz. It tackles the problem of low isolation between the two orthogonally polarized ports across a wide bandwidth at Ka-band. A single-layer high-efficiency CP reflectarray is proposed in the following Chapter. The proposed design solves the issues of bandwidth limitation and low aperture efficiency for single-layer CP reflectarrays. It achieves the widest bandwidth compared with other CP reflectarrays reported in terms of 3 dB AR bandwidth, 3 dB gain bandwidth, larger than 50% aperture efficiency and undistorted radiation pattern bandwidth. In Chapter 8, we investigate the first application of tightly coupled array (TCA) concept into ultra-wideband arrays with CP radiation. Instead of trying to reduce the mutual coupling among the elements, it exploits the strong mutual coupling to improve the bandwidth of a CP array. By using the strong coupling in a constructive way, it overcomes the bandwidth limitation of CP arrays which are constituted by narrow-band elements

Polarization diversity and adaptive beamsteering for 5G reflectarrays: a review

The growing demands of advanced future communication technologies require investigating the possible enhancement in the current features of a reflectarray antenna. Its design and experimental features need a thorough investigation before a plausible transition towards millimeter wave frequencies. This paper provides a detailed review covering various fundamental and advanced design tactics for polarization diversity and beamsteering in the reflectarray antenna. The diversity in the polarization has been discussed for linear and circular polarized designs in reflectarrays. The importance of electronically tunable materials and different lumped components for adaptive beamsteering in reflectarrays has also been highlighted. Each design has been critically analyzed and possibilities of its compatibility with future 5G systems have been provided

Technologies for Near-Field Focused Microwave Antennas

This paper provides a review spanning different technologies used to implement near-field focused antennas at the microwave frequency band up to a few tens of GHz: arrays of microstrip patches and printed dipoles, arrays of dielectric resonator antennas, reflectarrays, transmitarrays, Fresnel zone plate lenses, leaky-wave antennas, and waveguide arrays

Single-Layer Wideband Circularly Polarized High-Efficiency Reflectarray for Satellite Communications

This paper presents a single-layer circularly polarized (CP) reflectarray which achieves large bandwidth in terms of axial ratio (AR), gain, aperture efficiency and radiation pattern. By using a novel wideband S-shaped phasing element, an offset-fed reflectarray with 20° offset beam is designed based on the element angular rotation method. Theoretical analysis is given to analyze the effect of angular rotated elements on the performance of the reflectarray, which indicates that the AR bandwidth of the reflectarray can exceed the AR bandwidth of the feed horn. Furthermore, the influence of the differential spatial phase delay is analyzed quantitatively, and the performance of S-element-based reflectarrays with different aperture sizes are investigated and discussed. To verify these concepts, a 180mm×180mm prototype with 15×15 elements is fabricated and measured. The measured results confirm that the proposed reflectarray achieves a 68.5% 3-dB AR bandwidth (7.0 GHz to 14.3 GHz) and a 47.8% 3-dB gain bandwidth (8.6 GHz to 14 GHz). Moreover, the aperture efficiency is larger than 50% in a 33% bandwidth and larger than 30% in a 64% bandwidth

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications

Dual-band beam scanning reflectarrays and novel wideband and polarization diversified planar antennas

The reflectarray antenna has been considered as a suitable candidate to replace the traditional parabolic reflectors because of its high-gain and low-profile features. Beam scanning capability and multi-band operation are the current trends of the reflectarray design. It is desired to implement these functionalities with simple and effective techniques. Narrow bandwidth is the main issue which restricts the applications of the microstrip antennas. New microstrip slot antennas and polarization diversified planar antennas are introduced as the solutions to the issue of narrow bandwidth in this dissertation. A dual-band beam scanning reflectarray has been developed. It is the first offset-fed reflectarray that has been ever practically developed to emulate a cylindrical/parabolic type of reflector. Unlike other beam scanning reflectarrays which integrate phase tuning devices into the reflectarray elements and control the reflection phase, the beam scanning capability of this reflectarray is provided by its feed array. This method significantly reduces the complexity of the design of the beam scanning reflectarray. A new dual-band reflectarray configuration is also developed to eliminate the possible top layer blocking effects in the dual-layer reflectarray configuration. Perforated patches loaded with slots on the ground plane and rectangular patches loaded with slots on the patches are adopted as the low and high frequency bands, respectively. It is guaranteed that no physical contact between any two elements will occur. The bandwidth of the conventional microstrip antenna is small. A new wideband circularly polarized microstrip slot antenna is introduced in this dissertation. Very wide 3-dB axial ratio bandwidth is observed for the proposed antenna. The antennas are assembled in triangularly arranged array with sequential rotation feed technique. Polarization polarity is an alternative solution to the narrow bandwidth. A reconfigurable circularly polarized microstrip antenna is proposed. The antenna has both right-hand and left-hand circular polarizations which are controlled by two piezoelectric transducers. In addition, a dual-band dual-linearly-polarized planar array is designed based on the concepts of polarization diversity and multi-band operation. The research presented in this dissertation suggests useful techniques for reflectarrays and novel antenna designs. The results should have many applications for the modern wireless communication and radar systems

A millimeter wave reflectarray antenna with tilted side patch elements for fifth generation communication systems

A flat surface reflectarray antenna is becoming an impending competitor for fifth generation (5G) communications among the generally known conventional antenna systems. Its narrow bandwidth and high loss performance lead to restrict its gain and effciency at millimeter wave frequencies. Additionally, high design sensitivity is also an issue at millimeter waves that can trigger the problem of imperfect fabrications. Therefore, a simple design of reflectarray patch element is required with wide reflection phase range to achieve wideband and high gain performance. Effciency of reflectarray antenna is also needed to be formulated properly to acquire polarization diversity. In this work, a new reflectarray patch element with a tilted side is recommended for a wideband dual resonance operation within 24 GHz to 28 GHz frequency range. Dual resonance of the tilted side patch element offers a reflection phase range of more than 600' and a reflection loss of 1.6 dB with a novel design. Simulated results of the patch element have been verified by the scattering parameter measurements using a waveguide simulator. Additionally, a mathematical relationship has been formulated to predict the effciency of the reflectarray antenna based on its aperture shape and feed distance. It has been found that, a circular aperture reflectarray attains 21.46% higher effciency than its equivalent square aperture reflectarray of the same feed distance. Consequently, a circular aperture reflectarray consisting of 332 variable size tilted side patch elements has been designed and tested at 26 GHz with various possible configurations. The high cross polarization issue due to the asymmetric design of the tilted side patch element has been tackled by mirroring the orientations of the elements on the surface of reflectarray. Moreover, circular ring slots with variable radius have been embedded in reflectarray ground plane for gain improvement. Experimental results show that, the slotted ground reflectarray antenna offers a 3.5 dB higher gain with 22.9% higher effciency and 3% wider bandwidth than a full grounded reflectarray antenna. A maximum of 26.1 dB gain with 41.3% effciency and 11.5% (3 GHz) bandwidth has been acquired with the slotted ground reflectarray antenna. The tilted side patch reflectarray has offered dual linear polarization when its elements are mirrored to each other and dual circular polarization when its elements are not mirrored to each other. Its main beam has been numerically steered up to +20' by a progressive phase shift of 80'. The acquired parameters of the tilted side patch reflectarray antenna fit within the requirements of the 5G communication systems