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

A review of wideband reflectarray antennas for 5G communication systems

The advancement in the current communication technology makes it incumbent to analyze the conventional features of reflectarray antenna for future adaptability. This work thoroughly reviews the design and experimental features of reflectarray antenna for its bandwidth improvement in microwave and millimeter wave frequency ranges. The paper surveys the fundamental and advanced topologies of reflectarray design implementations which are needed particularly for its broadband features. The realization of its design approaches has been studied at unit cell and full reflectarray levels for its bandwidth enhancement. Various design configurations have also been critically analyzed for the compatibility with the high frequency 5G systems

Beam-Steerable and Reconfigurable Reflectarray Antennas for High Gain Space Applications

Reflectarray antennas uniquely combine the advantages of parabolic reflectors and phased array antennas. Comprised of planar structures similar to phased arrays and utilizing quasi-optical excitation similar to parabolic reflectors, reflectarray antennas provide beam steering without the need of complex and lossy feed networks. Chapter 1 discusses the basic theory of reflectarray and its design. A brief summary of previous work and current research status is also presented. The inherent advantages and drawbacks of the reflectarray are discussed. In chapter 2, a novel theoretical approach to extract the reflection coefficient of reflectarray unit cells is developed. The approach is applied to single-resonance unit cell elements under normal and waveguide incidences. The developed theory is also utilized to understand the difference between the TEM and TE10 mode of excitation. Using this theory, effects of different physical parameters on reflection properties of unit cells are studied without the need of full-wave simulations. Detailed analysis is performed for Ka-band reflectarray unit cells and verified by full-wave simulations. In addition, an approach to extract the Q factors using full-wave simulations is also presented. Lastly, a detailed study on the effects of inter-element spacing is discussed. Q factor theory discussed in chapter 2 is extended to account for the varying incidence angles and polarizations in chapter 3 utilizing Floquet modes. Emphasis is laid on elements located on planes where extremities in performance tend to occur. The antenna element properties are assessed in terms of maximum reflection loss and slope of the reflection phase. A thorough analysis is performed at Ka band and the results obtained are verified using full-wave simulations. Reflection coefficients over a 749-element reflectarray aperture for a broadside radiation pattern are presented for a couple of cases and the effects of coupling conditions in conjunction with incidence angles are demonstrated. The presented theory provides explicit physical intuition and guidelines for efficient and accurate reflectarray design. In chapter 4, tunable reflectarray elements capacitively loaded with Barium Strontium Titanate (BST) thin film are shown. The effects of substrate thickness, operating frequency and deposition pressure are shown utilizing coupling conditions and the performance is optimized. To ensure minimum affects from biasing, optimized biasing schemes are discussed. The proposed unit cells are fabricated and measured, demonstrating the reconfigurability by varying the applied E-field. To demonstrate the concept, a 45 element array is also designed and fabricated. Using anechoic chamber measurements, far-field patterns are obtained and a beam scan up to 25o is shown on the E-plane. Overall, novel theoretical approaches to analyze the reflection properties of the reflectarray elements using Q factors are developed. The proposed theoretical models provide valuable physical insight utilizing coupling conditions and aid in efficient reflectarray design. In addition, for the first time a continuously tunable reflectarray operating at Ka-band is presented using BST technology. Due to monolithic integration, the technique can be extended to higher frequencies such as V-band and above

Analysis, Design and Applications of Reflectarrays

A brief overview of reflectarray antennas mainly focused on some efficient analysis and design techniques and on recent developments has been presented. A technique based on the local periodicity and Method of Moments in Spectral Domain has been presented as very efficient for the analysis of reflectarray antennas. The technique has been validated by comparing simulations and measurements in several breadboards. Based on the previous analysis technique, several design procedures have been implemented for different antenna performances, including requirements of broad-band, dualfrequency and stringent contoured beams. Finally some recent developments for applications in space and LMDS antennas are presented

Broadband Approaches And Beam-Scanning Techniques For Reflectarray Antenna

Reflectarray antennas combine the numerous advantages of reflector antennas and phased array antennas and create a hybrid high-gain antenna with a low-profile, low-mass, easy-fabrication, and diversified radiation performance. However, it still has some inherent drawbacks, such as limited bandwidth and scanning range, which are targeted in this dissertation. At first, the array theory approach for radiation analysis of reflectarray antennas is described and implemented. Numerical results are then presented and compared with reference results to confirm its reliability. As the most critical influential factor to the reflectarray bandwidth, the element bandwidth was studied at first, and the effects of element shape and substrate thickness were investigated. Then, a comprehensive study was performed to investigate the bandwidth performance of reflectarrays on the system level. The effect of aperture size, element bandwidth and phase synthesis method was discussed in sequence. Particularly, a novel phase synthesis approach was proposed, which enables reflectarray to achieve a significant bandwidth improvement even with elements of narrow bandwidth. Prototypes are fabricated and tested to validate the idea. Since the reflectarray antenna is a hybrid product of reflector and phased array antennas, its main beam could be steered by either rotating its feed or reconfiguring its element phases. The former way was explored at first. An improved phase design was proposed for reflectarrays mimicing parabolic-cylindrical reflectors to expand its scanning range. The published achievements of reconfigurable reflectarrays design are revieand it is found that currently efficiency is a big problem. A 1-bit 10ã—10 reconfigurable reflectarray using pin diode was designed, fabricated and measured to explore the energy loss, and experimental results shothat 14% efficiency could be reached. In summary, some improved designs regarding bandwidth and scanning performance for reflectarrays are proposed in this dissertation. Various factors affecting reflectarray bandwidth are investigated, which shall provide some guidelines regarding bandwidth improvement. On the other hand, two designs are presented to explore the beam scanning characteristic of reflectarray antenna, by mechanical and electrical ways respectively. Several prototypes have been fabricated and measured, demonstrating the novel features and potential applications of reflectarray antennas

Advanced Design Methodologies and Novel Applications of Reflectarray Antennas

Reflectarray antennas combine the numerous advantages of printed antenna arrays and reflector antennas and create a hybrid high-gain antenna with a low-profile, low-mass, and diversified radiation performance. Reflectarrays are now emerging as the new generation of high-gain antennas for long-distance communications. In this dissertation, some advanced concepts demonstrating novel features of reflectarray antennas are presented. • First, various approaches for radiation analysis of reflectarray antennas are described and implemented. Numerical results are then presented for a variety of systems and the advantages, limitations, and accuracy of these approaches are discussed and compared with each other. • A broadband technique by using sub-wavelength elements is proposed and prototypes are fabricated and tested. This technique enables the reflectarray to achieve a significant bandwidth improvement with no additional cost. • Infrared reflectarrays antennas are studied for possible applications in concentrating solar power systems. Material losses, an important design issue at infrared frequencies, are investigated and reflectarrays consisted of dielectric resonant elements are proposed with low-loss features at infrared. • Multi-beam reflectarray antennas are studied and it is demonstrated that by optimizing the phase of the elements, a desirable multi-beam performance can be achieved using a single-feed. Local and global phase-only optimization techniques have been implemented. Two Ka-band quad-beam prototypes with symmetric and asymmetric beams have been fabricated and tested. • Different approaches for beam-scanning with reflectarray antennas are also revieand it is shown that for moderately wide angle beam-scanning, utilizing a feed displacement technique is more suitable than an aperture phase tuning approach. A feed displacement beam-scanning design with novel aperture phase distribution is proposed for the reflectarray antenna, and is further optimized to improve the performance. A high-gain Ka-band prototype achieving 60 degrees scan range with side-lobe levels below 15 dB is demonstrated. • The feasibility of designing reflectarray antennas on conformal surfaces is also studied numerically. A generalized analysis approach is presented and the radiation performance of reflectarray antennas on singly-curved conformal cylindrical platforms are studied and compared with their planar counterpart. It is revealed that conformal reflectarray antennas are a suitable choice for a high-gain antenna where curved platforms are required. In summary, different challenges in reflectarray analysis and design are addressed in this dissertation. On the element design challenges, bandwidth improvement and infrared operation of reflectarray antennas have been studied. On the system level challenges, multi-beam designs, beam-scanning performance, and conformal platforms have been investigated. Several prototypes have been fabricated and tested, demonstrating the novel features and potential applications of reflectarray antennas