Aperture efficiency analysis of reflectarray antennas

Advanced Electromagnetics, 2016

This paper presents an analysis and design for a reflectarray antenna composed of an array of rectangular patches printed on a grounded dielectric slab. A simple analytical technique based on equivalent surface impedance is used to determine the reflection of the elements in reflectarray antenna. This equivalent surface impedance is obtained analytically in a closed form. The effect of the angle of incidence on each element in the reflectarray is included in calculations. To author’s knowledge, this property has not been included in previous analysis techniques of reflectarray antenna.

International Journal of Antennas and Propagation, 2012

Recent work on dual-reflector antennas involving reflectarrays is reviewed in this paper. Both dual-reflector antenna with a reflectarray subreflector and dual-reflectarrays antennas with flat or parabolic main reflectarray are considered. First, a general analysis technique for these two configurations is described. Second, results for beam scanning and contoured-beam applications in different frequency bands are shown and discussed. The performance and capabilities of these antennas are shown by describing some practical design cases for radar, satellite communications, and direct broadcast satellite (DBS) applications.

ijeei.org

Lumped components are used to represent the reflectarrays designed using different commercially available materials. The loss performance and the effect of material properties on the reflectarray antennas are discussed in terms of the lumped components which are used in the equivalent circuit analysis. The bandwidth performance of reflectarrays designed with different materials is discussed using reflection loss and reflection phase plots obtained by equivalent circuit analysis. Furthermore the results obtained by equivalent circuit modeling are compared with the results obtained using CST Microwave Studio simulations and a close agreement between all the results has been demonstrated. The dielectric permittivity (ε r ) of materials investigated in this work ranges between 2.08 to 13 and the loss tangent (tanδ) values vary from 0.0003 to 0.025 while the reflection loss values obtained by equivalent circuit analysis varied from 0.179 dB to 6.875 dB and a variation in 10% and 20 % bandwidth is observed from 84 MHz to 360 MHZ and 126 MHZ to 540 MHz respectively based on the respective material properties.

2016

The reflectarray combines much of the simplicity of the reflector antenna with the performance of the array antenna. This paper presents an analysis and design of unit cell of reflectarray antenna using a square patch and square loop radiating elements and the steps taken in the design of a reflectarray unit cell operates in X -Band (8-12 GHz) at the center frequency of 10 GHz. The result of an analysis is generated from the Computer CST Microwave Studio using the approach of Floquet. This model takes into account a mutual coupling between elements, and is an efficient way to accurately characterize reflectarray elements.

Progress In Electromagnetics Research C, 2011

A bandwidth improvement method in reflectarray antennas by using closely space elements, i.e., unit-cell sizes smaller than λ/2, has been investigated both numerically and experimentally in this paper. A new definition of phase error has been introduced to analyze the broadband mechanism of closely spaced phasing elements. Through full wave EM simulations, it is revealed that closely spaced elements achieve a smaller phase error over the band. Based on these theoretical studies two Ka-band reflectarrays were fabricated and their performance was measured across the frequency range of 30 to 34 GHz. It is demonstrated that the reflectarray designed with closely spaced elements achieves a notable improvement in gain bandwidth performance.

International Journal of Grid and Distributed Computing, 2016

In this paper a new cell is proposed for reflectarray antenna and is used to design the antenna to obtain to maximum gain and efficiency using phase synthesis in a frequency band of 11 GHz up to 11.7 GHz for different beam angles. The proposed cell is a double ring of hexagon which introduces multiple resonances which can provide more than 360 degrees phase variation by changing the loop size. Design method is based on phase-only algorithm where amplitude of the field on the reflectarray surface is forced by the feed. A 1.2 m reflectarray is designed for different beam directions. The results show maximum directivity of 42 dB and maximum efficiency of 73% for the required bandwidth. Focal length is 1.5 m which is set for maximum efficiency.

IEEE Transactions on Antennas and Propagation, 2013

A dual-offset reflectarray demonstrator has been designed, manufactured and tested for the first time. In the antenna configuration presented in this paper, the feed, the subreflectarray and the main-reflectarray are in the near field one to each other, so that the conventional approximations of far field are not suitable for the analysis of this antenna. The antenna is designed by considering the near-field radiated by the horn and the contributions from all the elements in the sub-reflectarray to compute the required phase-shift on each element of the main reflectarray. Both reflectarrays have been designed using broadband elements based on variable-size patches in a single layer for the main reflectarray and two layers for the sub-reflectarray, incident field. The measured radiation patterns are in good agreement with the simulated results. It is also demonstrated that a reduction of the cross-polarization in the antenna is achieved by adjusting the patch dimensions. The antenna measurements exhibit a 20% bandwidth (12.2GHz-15GHz) (with a reduction of gain less than 2.5 dB) and a cross-polar discrimination better than 30 dB in the working frequency band. Index Terms-Reflectarray, cross-polarization reduction, broadband reflectarray and dual-reflectarray I. INTRODUCTION EFLECTARRAY antennas have demonstrated their benefits with respect to classic reflector antennas for certain applications. Reflectarrays exhibit capabilities to provide high-gain focused beams in large apertures [1], contoured

IEEE Antennas and Wireless Propagation Letters, 2010

IEEE Antennas and Wireless Propagation Letters, 2015

Multi-element approach is utilized to increase the phase variation range of a square-ring sub-wavelength unit cell (UC) from 313° to more than 560°. Radiation characteristics of three thin reflectarray antennas (TRAs) constructed with the proposed UCs are investigated. This investigation demonstrates that to achieve a broadband highly efficient TRA, the employed λ/5-UC must have reflection loss considerably less than 0.1 dB and its constructing elements should also scatter the incident fields in the same fashion, i. e., the current distributions of all parts of the multi-element UC are of the same shape and cophased.

IEEE Transactions on Antennas and Propagation, 2013

A new design methodology is proposed for high-gain beam-scanning reflectarray antennas. Various approaches for designing beam-scanning reflectarray antennas are first reviewed and it is shown that for limited scan coverage, utilizing the feed displacement technique is a convenient design approach. To improve the scan coverage, a single-reflector bifocal aperture phase distribution is proposed for the reflectarray antenna, and is further optimized to improve the beam-scanning performance. Four reflectarray prototypes, each corresponding to a specific aperture phase distribution, have been fabricated and tested. A Ka-band reflectarray antenna with 60 degrees scan coverage achieving 30-dB gain and side-lobe level below 15 dB is demonstrated.

AEU - International Journal of Electronics and Communications, 2018

this paper presents a comprehensive and accurate algorithm based on circuit model to design reflect-array antennas (RAAs). The proposed algorithm can extract geometry of RAA structure corresponding to radiation parameters without employing any approximation or optimization intervention into the algorithm. Simulation results for some comprehensive examples, verify the validity of the proposed algorithm. This method is simple, fast, accurate, and can be expanded to all species of RAAs with arbitrary geometries. One of the main problems confronted in RAAs is low bandwidth characteristics. To attain wide bandwidth, we exploited the proposed algorithm with combination of multi-layer design of RAAs and subwavelength element. Convergence is observed between simulation and fabrication results, asserting good accuracy in method. In 10-15 GHz band, the maximum gain and-1dB bandwidth of two-layer antenna is 31.4 dB and 18.5%, respectively.

2022

IEEE Antennas and Propagation Magazine, 2000

In this paper, a modular technique is described for the analysis of dual-reflector antennas using a reflectarray as a subreflector. An antenna configuration based on a sub-reflectarray and a parabolic main reflector provides better bandwidth than a single reflectarray, and has a number of advantages compared with a conventional dual-reflector antenna. Examples include the possibility of beam shaping by adjusting the phase on the sub-reflectarray, and potential capabilities to scan or reconfigure the beam. The modular technique implemented for the antenna analysis combines different methods for the analysis of each part of the antenna. First, the real field generated by the horn is considered as the incident field on each reflectarray element. Second, the reflectarray is analyzed with the same technique as for a single reflectarray, i.e., considering local periodicity and the real angle of incidence of the wave coming from the feed for each periodic cell. Third, the main reflector is analyzed using the Physical Optics (PO) technique, where the current on the reflector surface is calculated by summing the radiation from all the reflectarray elements. Finally, the field is calculated on a rectangular periodic mesh at a projected aperture, and then a time-efficient fast Fourier transform (FFT) algorithm is used to compute the radiation pattern of the antenna. The last step significantly improves the computational efficiency. However, it introduces a phase error, which reduces the accuracy of the radiation patterns for radiation angles far away from the antenna's axis. The phase errors have been evaluated for two integration apertures. It has been demonstrated that accurate patterns are obtained in an angular range of ±6°, which is sufficient for large reflectors. The method of analysis has been validated by comparing the results with simulations obtained from GRASP8. Finally, the theoretical beam-scanning performance of the antenna is analyzed.

IEEE Access

This paper describes a general framework for the optimization of very large reflectarrays for space applications. It employs the generalized Intersection Approach (IA) as optimizing algorithm, integrating a number of techniques that substantially improve the baseline algorithm by accelerating computations while preserving the accuracy of the electromagnetic analysis. In particular, a learning algorithm based on Support Vector Machines (SVMs) is used to obtain a surrogate model of the reflectarray unit cell accelerating the analysis more than three orders of magnitude. For the optimization, the gradient computation is accelerated by employing the technique of differential contributions on the radiated field, which avoids the use of the Fast Fourier Transform (FFT) in the computation of the far field. Finally, to improve the cross-polarization performance, instead of optimizing the crosspolar pattern, the crosspolar discrimination or crosspolar isolation are optimized, improving both the antenna and algorithm performance. Relevant numerical examples are provided to show the capabilities of the proposed framework for a Direct Broadcast Satellite (DBS) mission, showing how to design a contoured beam reflectarray with a European footprint with two different coverage zones. In addition, a complete study of computing time is carried out to analyse the impact of each technique in the optimization process.

Microwave and Optical Technology …, 2011