Microstrip Reflectarray Antenna Research Articles

Light-Controlled Large-Scale Wirelessly Reconfigurable Microstrip Reflectarrays

In this article, the concept and design of light-controlled large-scale wirelessly reconfigurable microstrip reflectarrays are proposed. Unlike conventional electrically reconfigurable microstrip reflectarray antennas (RAs) that control the aperture phase distribution by conducting wires for transmitting control signals, the proposed method utilizes light to control the ON- and OFF-state of the integrated positive-intrinsic-negative (p-i-n) diodes wirelessly and binaurally through light-sensitive resistance of photodiodes (PDs). The concept is validated by simulation first, where a 1 bit 32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times32$ </tex-math></inline-formula> wirelessly reconfigurable microstrip RA is designed at 10 GHz with a beam-steering range of ±60° for sidelobe levels < −10 dB, marking a record of 1024 elements with a tri-layer configuration. Experimentally, the light-control scheme is further validated by a smaller porotype of 256 elements, where a light-controlled beam steering from 30° to 45° is demonstrated. Compared with conventional wired reconfigurable microstrip RAs, the proposed method resolves the wire-routing complexity on the RA and offers a new possibility for further improving the maximum directivity, upper operating frequency, and the number of independently controllable polarizations of reconfigurable microstrip reflectarrays, paving the way for developing very-large reconfigurable intelligent surfaces (VRIS). Also, the proposed concept provides a new infrastructure for information exchange between light and microwaves.

Development of microstrip reflectarray based monostatic STAR antenna

A co-polarized microstrip reflectarray antenna for monostatic simultaneous transmit and receive (STAR) applications is proposed. It is developed with a single broadside radiation and realized by double-layered variable-sized stacked square patches. Two feeding horns, one is for transmitting while the other one is for receiving, are placed mirrored on the reflectarray aperture by comprehensively considering the spillover loss, the blockage and the focal-diameter ratio as well as the isolation between the two horns. To verify the proposed antenna, a Ku-band demonstrator is developed and examined. Measurements show that the developed antenna achieves a high isolation of over 35 dB from 14 GHz to 16 GHz, the maximum isolation is up to 54 dB at 15.9 GHz, and the measured maximum gain is up to 25.1 dBi. The proposed reflectarray antenna based monostatic scheme features simple architecture, high gain, high isolation, and low sidelobe, which could be an attractive candidate for STAR applications.

Low-mutual-coupling reflectarray antenna based on random fragmented elements with square loops

ABSTRACT A novel microstrip reflectarray antenna constructed by elements of random fragmented patches with square loops attached to the edge is proposed in this paper. The fragmented patch is gridded into 2 N × 2 N pixels, each of which is randomly assigned either conducting or non-conducting property. In this case, a variety of different reflection phases can be obtained due to the structural differences between the elements. To suppress the mutual coupling between elements, each fragmented unit is integrated with a metal square loop, and the reduction of the mutual coupling is indirectly analyzed across the frequency characteristics of the reflection phase for the combined elements. A prototype antenna with 7 × 7 elements was designed, fabricated, and measured. Both the simulation and measurement results show that the microstrip reflectarray antenna possesses a high gain of 19.7 dBi at its working frequency of 5.8 GHz, which is 2 dB higher than that of the reflectarray elements without square loops. Meanwhile, this antenna achieves an impedance bandwidth (|S| < − 10 dB) of 5.6%, side-lobes 13.1 dB below the main lobe, and with the cross-polarization level less than −18 dB.

POSIBILITY OF CREATING A PRINTED SINGLE-LAYER TRANSREFLECTOR WITH INCREASED PHASE EFFICIENCY

A new type of single‑layer transrefleсtor structure based on microstrip reflective antenna array is described. The developed device is a single‑layer printed circuit board on one side of which a system of printed reflectors is located, and on the other is a polarization structure consisting of parallel metal conductors, in contrast to a microstrip reflectarray antenna. The shape and geometrical dimensions of printed reflectors arranged in a rectangular or hexagonal (triangular) pattern are chosen in such a way that they transform a spherical front of an incident vertically polarized electromagnetic wave into a flat front of reflected wave. In the case of irradiation of the developed transreflector with a horizontal polarization wave, the printed structure makes minimal electromagnetic energy loss during its passage. The results of characteristics modeling (including phase curves) of an element of the reflective lattice in the W‑band for different angles of incidence of the wave on the planar structure under study are given. Based on the results obtained, the sizes of the reflective elements of the transreflector, which provide for the correction of the incident wave with the necessary phase discrete, are determined and an electrodynamic model of the transreflector antenna is built. The simulation of the main radiation characteristics of the antenna with the developed single‑layer transreflector was carried out.

Design and evaluation of a wideband reflectarray antenna using cross dipole with double‐ring elements

This article reports the design and analysis of a wideband, single layer, and dual-polarized microstrip reflectarray for Ku-band applications. The array element is constructed using a crossed dipole enclosed by two cross dipole loops. The element is optimized to exhibit a linear phase response and wide reflection phase range. The reflection characteristic of the unit cell is analyzed using an infinite array approach and the results are presented. A 324-element Ku-band microstrip reflectarray antenna of size 20 × 20 cm2 is simulated, fabricated, and experimentally evaluated. The 2.9-dB gain-bandwidth and aperture efficiency of the reported reflectarray are 45.3% and 35%, respectively. The reflectarray operates in the frequency range of 10.6 to 16.8 GHz.

Full-Wave Simulation-Based Phasing Characteristics of Microstrip Patches for Reflectarray Optimization with Neural Network

Microstrip reflectarray antennas (RAs) are able to provide equivalent performance of a traditional parabolic reflector, but with simple and light electromagnetic and mechanical structures; this can be achieved by an effective control of the phase response of each microstrip element on the reflecting surface. Thus the main problem is the fast and accurate modelling of the unit microstrip patch to be used in the array optimization. Since using simulators in the optimization procedure is computationally very ineffective, herein artificial intelligence is used as a rapid and accurate tool for characterization of the reflection angle of the microstrip unit element in terms of its geometry, substrate parameters and frequency. For this purpose, modelling of Omega shaped patch within the X-band is considered using Multilayer Perceptron (MLP) neural network trained the 3D CST microwave Studio simulator data. Validation of the MLP model is also worked out successfully with the 3D CST data. Thus a continuous function is obtained for the reflection angle in the geometry, substrate and frequency domain of the microstrip patch unit element that ensures the reflectarray optimization procedure as fast as using the analytical functions and as accurate as the 3D simulators. In the paper, full-wave simulation- based MLP modelling of the omega shaped microstrip patch is given in details.

A wideband, single layer reflectarray antenna with cross loop and square ring slot loaded patch elements

AbstractThis paper presents the design and analysis of a wideband X/Ku and Ku band reflectarray antenna. The proposed unit cell of the reflectarray antenna comprises a patch loaded with two distinct slots, viz. a square ring and a cross loop, printed on a low loss substrate, which is backed by a foam-loaded ground plane. The unit cell element offers a linear and large dynamic reflection phase range, which is achieved by optimizing the shape, location, and geometrical parameters of the two slots loaded on the patch. A 324 element microstrip reflectarray antenna of size 200 × 200 mm2 is constructed and analyzed for its radiation characteristics by simulation and measurement. The reflectarray offers a 3 dB gain bandwidth of 50.75% with the operating frequency range of 10–16.8 GHz. It offers a peak gain and aperture efficiency of 25.4 dB and 40% at 12.6 GHz, respectively. The cross-polarization level is below −40 dB over the entire operating frequency range.

Reflection phase analysis of reflectarray antenna based on paper substrate materials

&lt;span&gt;This article presents an analysis of reflection loss and reflection phase behavior of a novel microstrip reflectarray antenna, embedded on paper substrate material. Two different paper substrates were first analyzed for dielectric material properties. A detailed analysis of scattering parameters of rectangular patch element with variable substrate heights has been carried out. Rectangular patch elements fabricated using adhesive copper tape over the paper substrate, show that a wide bandwidth is achieved compared to available conventional substrate materials. Fabricated patch elements over paper substrate material show a broadband frequency response of 340 and 290 MHz. It has also been demonstrated that the measured reflection phase ranges for both the substrate cover 310º and 294º at low phase gradients of 0.12 and 0.24 º/MHz respectively.&lt;/span&gt;

Performance Enhancement of Wideband Reflectarray Antennas Embedded on Paper Substrate Materials

This research presents an innovative solution to address the bandwidth limitation of microstrip reflectarray antennas. Organic substrate materials with controlled compositions have been characterized to be employed as substrate materials for microstrip reflectarrays. The three proposed materials show low dielectric permittivity values of 1.81, 1.64 and 1.84 along with loss tangents of 0.053, 0.047 and 0.057 respectively. The proposed substrate materials have been verified by modelling reflectarray unit elements in CST MWS and measured using a waveguide simulator technique. The comparison between measured and simulated results show a good agreement with promising broadband performance of 312, 340 and 207 MHz for S1, S2 and S3 substrate materials respectively.

A Novel Single-Layer Unit Structure for Broadband Reflectarray Antenna

A novel X-band single-layer unit-cell structure with enhanced bandwidth for linearly polarized microstrip reflectarray antenna is proposed. The unit-cell structure is composed of two circular rings, each with a pair of gaps that are orthogonally placed, and two identical phase-delay lines attached to the outer circular ring. With this novel structure, a linear phase response ranging about 550° is achieved by varying the length of the phase-delay line. An offset-fed reflectarray antenna composed of 277 elements forming an octagon-shape aperture is designed, fabricated, and measured to verify the broadband characteristic of the proposed unit cell. Measurement results show that 20% 1-dB gain bandwidth is realized. Moreover, the maximum gain at 10 GHz is about 26.38 dBi, which means about 51.3% efficiency is achieved. At the same time, the sidelobe level and cross polarization for E-plane are also measured which are below −17.5 and −26 dB, respectively.

Circularly Polarized Transparent Microstrip Patch Reflectarray Integrated with Solar Cell for Satellite Applications

Circularly polarized (CP) transparent microstrip reflectarray antenna is integrated with solar cell for small satellite applications at 10 GHz. The reflectarray unit cell consists of a perfect electric conductor (PEC) square patch printed on an optically transparent substrate with the PEC ground plane. A comparison between using transparent conducting polymers and using the PEC in unit-cell construction has been introduced. The waveguide simulator is used to calculate the required compensation phase of each unit cell in the reflectarray. The radiation characteristics of 13 × 13 CP transparent reflectarray antenna are investigated. A circularly polarized horn antenna is used to feed the reflectarray. The solar cell is incorporated with the transparent reflectarray on the same area. The solar-cell integration with the reflectarray reduces the maximum gain by about 0.5 dB due to the increase in the magnitude of the reflection coefficient. The results are calculated using the finite integral technique (FIT).

A broadband KU‐band microstrip reflectarray antenna using single‐layer fractal elements

ABSTRACTA novel single‐layer microstrip reflectarray element with fractal structure is proposed. Ansoft HFSS is used to analyze the reflect phase for the fractal element in honeycomb lattice. A 469‐element prime focus microstrip reflectarray antenna composed of the proposed fractal elements is designed, manufactured, and measured. The measured gain level of 29.8 dB is obtained at the center frequency of 13.58 GHz with 1‐dB gain bandwidth of 15.3%. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:658–662, 2016

Efficient Design of the Microstrip Reflectarray Antenna by Optimizing the Reflection Phase Curve

The microstrip reflectarray antenna is an attractive directional antenna combining advantages of both the reflector and the microstrip array antenna. For the design of this kind of antenna, the conventional method, which is based on the reflection phase curve, may not be effective because of the approximations made in the design procedure. The common optimization method that employs an optimization algorithm in conjunction with the full-wave simulation to optimize the antennas’ structural parameters is able to achieve better performances in comparison with the conventional method; but it is impractical for large-scale microstrip reflectarray antennas due to too many structural parameters from variable reflection elements. To tackle the design problem of the microstrip reflectarray antenna, a new method is proposed for the first time. It optimizes the reflection phase curve rather than the structural parameters and then utilizes the optimized reflection phase curve to design the antenna. A microstrip reflectarray antenna working at 5.8 GHz and with a fixed size of 300 mm × 300 mm is designed for high gain as a sample design. The results show that the proposed method has greatly improved the antenna’s gain over 2.2 dB (from 19.7 dBi to 21.9 dBi) in comparison with the conventional design method, and it only needs to optimize 6 structural parameters, in contrast to 22 for the common optimization method.

A X/Ku dual‐band reflectarray design with cosecant squared shaped beam

ABSTRACTA X/Ku dual‐band center‐fed microstrip reflectarray antenna with cosecant squared shaped beams has been developed. The circular reflectarray has a radius of 0.3 m and a flat aperture that emulates a cylindrical reflector antenna. The reflectarray is designed for two frequency bands: 10 GHz (X band) and 15 GHz (Ku band). Cross‐dipole elements and double‐ring elements are uniquely applied on a dual‐layer structure to achieve the desirable dual‐band operations. As the two operation frequency bands are close to each other, the coupling effects of the dual‐band reflectarray elements are investigated, and the unit cell design is optimized in simulations to suppress the interband interference. A phase‐only synthesis technique for cosecant squared patterns is also discussed and realized. For demonstration purpose, prototype antenna is fabricated and measured and the measured results are compared with the simulation results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2028–2034, 2014

Closed-Form Analysis of Reflection Losses in Microstrip Reflectarray Antennas

Microstrip reflectarray antennas consist of a grounded quasi-periodic array of printed elements able to compensate the phase displacement of a non-coherent electromagnetic excitation generated by a feeder. The design of reflectarray antennas is usually accomplished by tracing the reflection phase diagram of the periodic version of the printed surface, which is analogous to a high-impedance surface (HIS). Reflection losses of this periodic structure are here analyzed through a simple equivalent transmission line model. The analytical expressions of the surface impedance offered by a HIS (real and imaginary part) as a function of the imaginary part of the dielectric permittivity of the substrate are derived through well justified approximations. Some useful practical examples are then presented both for verifying the accuracy of the derived closed-form expressions and for studying the effect of the geometrical and electrical parameters of the periodic surface on the reflection losses. The dependence of the input impedance on the capacitance associated with the printed pattern is highlighted, demonstrating that highly capacitive elements (tightly coupled subwavelength elements) are preferable for minimizing reflection losses.

Dual Layer Microstrip Refflectarray Composed of Two Stacked Arrays with Minkowski and Square Shaped Radiating Element

A dual layer microstrip reflectarray composed of two stacked arrays with Minkowski and square patches of variable dimension is presented. The reflection phase coefficients on the reflector surface is achieved by tuning the dimensions of the patches. This technique is to broaden the bandwidth and to extend the reflection phase range compare to a conventional single layer reflectarray. From the simulation results of a unit cell composed of two stacked arrays of Minkowski and square patch showed that, 415° reflection phase range is achieved and lower insertion loss which is lower than 0.9 dB. Base on the simulated reflection phase coefficient, a dual layer microstrip reflectarray antenna with Minkowski and square radiating shape elements have been design and model using commercially available computer models of CST Microwave Studio. The reflectarray has been constructed using Taconic RF-35 substrate. From the radiation pattern at 11 GHz frequency, it shows that the HPBW of 4.7º in both plane, a side lobe level (SLL) of –17 dB and a maximum directivity of 26.1 dBi.

Design of Microstrip Reflectarray Antenna Using a Genetic Algorithm Based Optimization Method

The design of the microstrip reflectarray antenna is commonly based on the reflection phase curve, but this is not an accurate method, as many parameters have been neglected in the design procedure. This work explores the genetic algorithm in conjunction with full-wave simulation and the cluster parallel computation to design a microstrip reflectarray antenna. A microstrip reflectarray antenna, which consists of a 7 × 7 rectangular-patch/ring-combination reflection elements and is illuminated by a patch antenna, is designed for high gain. Results demonstrate that in comparison with the design method based on the reflection phase curve, the proposed optimization method is able to design a microstrip reflectarray antenna with better performances; e.g., the gain has been considerably improved (from 18.1 dBi to 19.5 dBi) at the design frequency of 5.8 GHz.

Low Cross-Polarization Reflectarray Antenna

A low cross-polarization center-fed microstrip reflectarray antenna is presented. The cross-polarization elimination is accomplished by a particular arrangement of the elements. Using this technique, a center-fed reflectarray antenna has been designed at center frequency of 11.7 GHz. Measurement results are compared with that of a previously reported reflectarray antenna. Both antennas are exactly the same in every aspect except for the elements arrangement. Measurement results show 1 to 12 dB reduction in cross-polarization level and a notable enhancement in the new antenna's overall gain.

Novel Broadband Reflectarray Antenna with Two-Type Elements for Millimeter-Wave Application

A novel broadband millimeter-wave microstrip reflectarray antenna with square-annular patches and combined patches has been presented, aiming to solve the problem of how to obtain a full 360° range of phase shifts for single-layer. The choice of these two-type elements can make the phase shift smoother and increased up to 360°, leading to broader bandwidth. Based on this technique, a single-layer microstrip reflectarray antenna operating at 94 GHz has been designed. The computed results demonstrate the agreement of the main beam steering with the design requirement, and a 1-dB gain bandwidth close to 10% is obtained. The simulation results verify the feasibility of this design.

A Dual-Mode Millimeter-Wave Folded Microstrip Reflectarray Antenna

A dual-mode folded microstrip reflectarray antenna was developed and demonstrated in this paper. The proposed folded reflectarray antenna contains three parts: a planar main reflector, a planar subreflector, and printed feed antennas. The main reflector is used to produce twisted reradiated fields and to provide phase compensation for focusing. The subreflector parallel with the main reflector is made of a substrate printed with high-density metal grid lines, which is transparent to perpendicularly polarized fields, but would reflect the parallel ones. Three fixed-position patch antennas with polarization parallel to the grid lines are created for the radar mode, so that the radiation beam is switchable. Another patch with perpendicular polarization is designed for communication. A simple approach was proposed for simulating and designing the folded reflectarray. Measured results show good agreement with the calculated ones.