Reflection loss and bandwidth performance of X‐band infinite reflectarrays: Simulations and measurements (original) (raw)
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Investigation into Bandwidth Limitations of Microstrip Reflectarrays
2008
The paper describes theoretical investigations into the bandwidth limitations of a microstrip reflectarray which uses variable size antenna elements for its phasing. Three main factors limiting the bandwidth are considered. The first one is related to the phase compensation that is required to convert a spherical wavefront launched by the feed into a planar wavefront. The second one is linked to the limited phase range of typical microstrip antenna elements. The third one is related to the match between the required phase as a function of frequency and the fixed size elements' phase characteristics. The three factors are responsible for the reflectarray phasing errors that reduce its gain as the frequency departs from the centre frequency. It is shown that the first factor puts an upper limit to the reflectarray operational bandwidth, while the second one has a less profound impact. The third factor is influenced by choice of the element's shape. It is shown that circular and square patches offer better match than printed dipoles to the required phase slopes.
Optimum Design of Broad-Beam Microstrip Reflectarray
2007
The reflectarray's elements arrangement for generating an arbitrary phase distribution in the antenna aperture and thus a wide beamwidth of far field pattern are presented. The desired phase delay of reflectarray elements, which are duplicated the same radiating aperture as parabolic backscatters, are determined on the construction of the curvature of a shaped backscatter surface with the help of Snell's law for beam forming to cover a broad area. The method of moment (MoM) and the infinite-array are applied to calculate reflection phase characteristic. The optimized feed distance is calculated from the aperture efficiency with considering feed blockage efficiency and has investigated the influence of the feed position on the -3 dB beamwidth and gain performance. Having confirmed the validity of this approach, the X-band antenna prototype is designed and developed. This reflectarray is tested experimentally and shows good performance.
Design of broad-beam microstrip reflectarray
WSEAS Transactions on Communications
The reflectarray's elements arrangement for generating an arbitrary phase distribution in the antenna aperture and thus a wide beamwidth of the far field pattern is presented. The desired phase delay of reflectarray elements, which duplicated the same radiating aperture as backscatters, is determined on the construction of the curvature of a shaped backscatter surface with the help of Snell's law for beam forming to cover a broad area. The Method of Moments (MoM) and the infinite-array are applied to calculate reflection phase characteristics. The phase and radiation pattern synthesis method for microstrip reflectarray that has to illuminate a predefined circular area are presented by using a variety of discretization of elementary geometrical functions such as, triangular, quadratic, circular, gaussian, cosine, squared cosine, and parabolic distributions. These backscatter functions are discussed in terms of merits and demerits to find appropriate radiation characteristics ...
Implementation of an Innovative Method to Design Reflectarray Antennas
International Journal of Antennas and Propagation, 2012
A novel computed aided technique for designing reflectarray antennas is presented. The developed approach automatically generates the geometrical model of reflectarray antennas taking into account some input parameters, such as, the unit cell type and dimensions, frequency, focal length, periodicity, dielectric materials, and desired main beam radiating direction. The characteristics of the reflecting elements are selected considering the spatial phase delay at each unit cell to achieve a progressive phase shift. The implemented procedure also provides the phase characteristic of the unit element, which is rapidly computed by using a parallelized Moment Method (MoM) approach. The MoM is also used to obtain the radiation pattern of the full reflectarray antenna. In order to evaluate the new technique, a dual-interface prototype has been designed and simulated showing high-performance capability.
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
Bandwidth Improvement of Reflectarray Antennas Using Closely Spaced 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.
Analysis of a dual-reflectarray antenna
IET Microwaves, Antennas & Propagation, 2011
A modular technique for the analysis of a dual-reflectarray antenna (DRA) configuration is presented. The proposed analysis method has been used to design a DRA that emulates previous dual-reflector antennas in Ku-and W-bands including a reflectarray as a sub-reflector. The results for the DRA compare very well with those of the parabolic reflector and reflectarray sub-reflector; radiation patterns, antenna gain and efficiency are practically the same when the main parabolic reflector is substituted by a flat reflectarray, the gain being reduced by a few tenths of a dB as a result of the ohmic losses in the reflectarray. The phase adjustment on two surfaces provided by the dual-reflectarray configuration can be used to improve the antenna performance in some applications requiring multiple beams, beam scanning or shaped beams.
BANDWIDTH CONSIDERATIONS FOR A MICROSTRIP REFLECTARRAY
Progress in Electromagnetics Research B, 2008
Abstract—The paper describes a theoretical investigation into a limited bandwidth operation of a microstrip reflectarray. Two main factors limiting the bandwidth are considered. One is related to the requirement of phase compensation to convert a spherical wavefront launched by a feed into a planar wavefront. The other one is linked to the limited phasing range of microstrip antenna elements. The two factors contribute to the reflectarray phasing errors that in turn reduce its gain as a function of frequency. Simple formulas for an upper bound of gain bandwidth are derived, assuming the phase compensation by the elements is independent of frequency changes and verified against the results produced by other researchers. It is shown that the phase errors incurred in the path equalization to obtain conversion from spherical to planar wavefronts have a more profound effect on the reduction of operational bandwidth of the reflectarray than the phase truncation implemented on the required phase from each element.