Transmitarray work begins with the setting up of a database of transmission coefficients versus element parameters. This database has to be inverted as part of the design process. It is shown that inverse neural networks are well-suited to do this, even when the inverse relationships are multivalued.

Transmitarray Antenna Design Using Forward and Inverse Neural Network Modeling

Fractal-Inspired Multifrequency Structures for Piezoelectric Harvesting of Ambient Kinetic Energy

A printed dual band notched ultra wideband monopole antenna with a single perturbed Hilbert curve slot is presented which exhibits 121% impedance bandwidth. A single modified Hilbert curve slot provides dual band notch characteristics in the range of 3.3–3.7 GHz (WiMAX), 3.7–4.2 GHz (C-Band), and 5.15–5.825 GHz (WLAN) which makes the notch design process simpler than other dual band notched antennas. The gain of the proposed antenna varies from 3 to 4 dBi over its operating frequency range, except at the rejection bands. Suitable radiation characteristics are obtained throughout its operating band. Simulation and measured results of the proposed antenna are in good agreement.

An UWB antenna using modified Hilbert curve slot for dual band notch characteristics

This paper presents a thorough review of the techniques involved in the enhancement of the efficiency performance of the reflectarray antenna. The effect of the selection of a suitable patch element or a proper feeding mechanism on efficiency improvement is studied in detail. Reflectarray loss quantification is examined in relation to the design techniques involved in the efficiency improvement. A low loss patch element with a wide reflection phase range and a properly illuminated reflectarray aperture are supposed to offer high efficiency performance. Additionally, the placement, the orientation and the position of a patch element on the reflectarray surface can also affect its efficiency performance. Mathematical equations were developed to estimate the efficiencies of circular and square aperture reflectarray antennas by considering their feed footprints. Moreover, a step by step practical method of predicting and measuring the total efficiency of a reflectarray antenna is presented. The two selected apertures of the reflectarray consisting of the square patch element configuration are fabricated and measured at a frequency of 26 GHz. Their measured efficiencies have been estimated using the derived equations, and the results were compared and validated using the efficiencies obtained by the conventional gain-directivity relation.

https://www.mdpi.com/2079-9292/9/11/1887/pdf

Aspects of Efficiency Enhancement in Reflectarrays with Analytical Investigation and Accurate Measurement

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.

/pdf/efficient-design-of-the-microstrip-reflectarray-antenna-by-3ax4nikwli.pdf

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

This article explores designing wideband microstrip antennas utilizing fractal geometries. A novel microstrip monopole antenna using the geometry of the fractal binary tree is presented. To achieve a wide impedance bandwidth, the proposed microstrip fractal antenna is optimized in an automated design, making use of the genetic algorithm with the full-wave electromagnetic simulation and cluster parallel computation. A design result is presented. A prototype of the designed antenna has been fabricated and tested. Good agreement is obtained between numerical calculated and measured results, and results show the proposed fractal antenna obtains a quite promising S11 < −10-dB impedance bandwidth, which surpasses 42.8% (from 2.46 GHz to 3.80 GHz).

A Novel Wideband Microstrip Fractal Antenna Based on the Fractal Binary Tree

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.

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

A reflectarray antenna using sub-wavelength fragmented elements is proposed. The size of the element is at the working frequency of 5.8 GHz. A full 360° phase range is achieved due to the flexibili...

Xing Chen

Papers

A Novel Wideband Microstrip Fractal Antenna Based on the Fractal Binary Tree

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

A low mutual coupling reflectarray antenna using sub-wavelength fragmented elements with isolation walls based on H-shaped unit cells