Zone Plate Reflector Research Articles

Bi-functional metamaterial quadrilateral array with non-interfering anisotropy

We propose an anisotropic metamaterial quadrilateral array with metallic wires inserted in the perforated dielectrics over a ground plane, possessing the gradient index property and the epsilon-near-zero characteristic respectively in different polarization directions. As a result, such a metamaterial array possessing the non-interfering anisotropy features would be able to collimate electromagnetic fields as a zone plate reflector when we feed it at the focus in the broadside direction, while being capable of generating four directive beams as an ENZ lens when excited in the center. The proposed design of metallic-wire embedded perforated dielectrics can be effectively applied to building up versatile devices with more advanced functionalities that are fundamentally dependent on the anisotropic properties of hybrid metamaterials.

Bifunctional Broadband Zone Plate for Highly Directive Broadside Emissions and Endfire Radiations

Zone plate reflectors for the highly directive broadside radiations are investigated in this letter, where we show that such a reflector could also function as a lens with endfire emissions when integrated with a dielectric phase compensation layer. More specifically, we employ additional dielectrics to collimate electromagnetic fields radiating through the radial direction of the original zone plate reflector, and obtain well-collimated beams as a lens without degrading the performances of the zone plate as a reflector. We practically implement the proposed design through drilling subwavelength holes with different sizes in a dielectric host medium, and the perforated zone plate demonstrates the functionalities of generating both broadside and endfire radiations in a broadband frequency range.

Field imaging near to the surface of terahertz reflective optics using a vector network analyzer.

A vector network analyzer-based quasi-optical measurement system that is suitable for mapping electric field intensity and phase near to the surface of terahertz reflective optics is presented. The system uses a fixed five parabolic mirror and transmitter/receiver head arrangement that has the benefit of requiring only the sample to be swept during measurement. The system has been tested with a micromilled aluminum zone plate reflector used as an exemplar structure. The measured focal point of the zone plate reflector, at its designed frequency of 1THz, is shown to correspond well to both finite difference time-domain simulations and analytical theory.

A 100-GHz Metal-Only Reflectarray for High-Gain Antenna Applications

A 100-GHz metal-only reflectarray antenna is designed, fabricated, and tested. The required phase shift is achieved by simply tuning the metal block height, aiming to eliminate dielectric losses at high frequencies. An equivalent circuit model is employed to analyze the element reflection performance. A prototype reflectarray with a 30-mm square aperture is then fabricated and tested using near-field measurement setup. The measured results show an aperture efficiency of 50.1% at 100 GHz, and the measured radiation patterns agree very well with the full-wave simulation results. To compare the radiation performances, a parabolic reflector, a Fresnel zone plate reflector, and an unwrapped reflectarray of same size are also evaluated. The full-wave simulation results demonstrate that the proposed design not only achieves good radiation performance, but also exhibits advantages such as low profile, easy fabrication, and low cost.

The analysis and comparison of two novel kinds of focusing elements as reflectors

In this article, two novel kinds of focusing elements as reflectors are analyzed and compared. One is the grooved Fresnel zone plate reflector with continuous phase-correcting. The other called subzone paraboloid reflector, has the profile that consists of a series of paraboloids. Their diffraction efficiencies and bandwidths are described. The two elements still preserve the advantages of Fresnel zone plates, namely, low profile, high efficiency, and simple fabrication. Two dual-reflector antennas using the proposed focusing elements as the main reflectors are simulated and the results show that these antennas have good radiation performances. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:101-108, 2015.

Broadband design of a low‐profile reflector antenna

This work presents the design and analysis of a modified Fresnel zone plate reflector for broadband operation. A new technology based on slight deformations on a flat metallic surface is applied to obtain the geometrical model of the proposed flat reflector antenna. In comparison with reflectarrays, Fresnel zone reflectors are lossless, low cost, easy to fabricate and broadband. According to the specifications of a previously published reflectarray, a centre-fed prototype whose dimensions are 28 × 21 cm has been designed and analysed showing a maximum gain of 28.06 dBi at 12.5 GHz and a 32.8% 3 dB gain bandwidth in the range between 10.4 and 14.5 GHz. A second prototype has been designed and analysed to evaluate the performance of the proposed design method compared with a previous design of a Fresnel zone reflector. Better results in terms of gain and antenna efficiency have been obtained.

W-Band Fresnel Zone Plate Reflector for Helicopter Collision Avoidance Radar

A high gain Fresnel zone plate reflector is presented for helicopter collision avoidance radar at 94 GHz. The antenna system consists of a compact, airtightness and low return loss primary source illuminating a printed reflector with Fresnel plate zone phase correction. In order to increase the overall efficiency, the reflector combines 8 correcting zones in its center and 4 on the border. Reflected phase of over 360deg is achieved by means of circular ring or combined circular and ring patches. The reflector is fabricated using standard photolithographic techniques. The primary source consists of a small FSS made by a double slot array antenna pasted on the aperture of a standard WR-10 waveguide. Antenna measurements were conducted using a compact base arrangement. The antenna performs 37.8 dBi at the center frequency of 94 GHz with a maximum value of the return loss value not exceeding -25 dB. The frequency bandwidth at -3 dB in gain and return loss is of 9%

94 GHz zonal ring reflector for helicopter collision avoidance

A single-layer reflector antenna combining eight and four correcting Fresnel zones is presented. The progressive phase shift is achieved by circular and annular patches. The choice of a quarter-wavelength thickness substrate provides naturally 0 and 180° correcting zones that simplify the reflector design. A prototype of reflector antenna working at 94 GHz has been designed, built and measured. Measurement results show 70% improvement of antenna aperture efficiency compared to the half-wave Fresnel zone plate reflector .

Design of mm-wave phase-correcting fresnel zone plate reflector antenna with continuous structure

Based on scalar diffraction optics theory, a new type of mm-wave antenna(diffraction antenna) phase-correcting Fresnel zone plate with continuous structure is described in this paper. It has the advantages of thinner thickness, lighter weight and design flexibility. The design theory and space shadow are discussed in details, and the measured results are presented. The results show that the properties of this kind of antenna is closed to paraboloid reflector.

Multilayer offset Fresnel zone plate reflector

An offset phase-correcting Fresnel zone plate (FZP) reflector antenna based on the multilayer configuration is presented. The reflector consists of a conducting ground and four layers of conducting patterns separated by four dielectric substrates. An experimental prototype designed at 10.39 GHz was fabricated and tested. With a 0.32 m by 0.34 m elliptical reflector aperture and a pyramidal feedhorn, the antenna achieved -20-dB sidelobe level and 61% maximum efficiency. Compared with a phase reversal FZP of the same size, a 3.3-dB gain improvement and significant sidelobe reduction were obtained. >

Fresnel zone plate reflector incorporating rings

A novel high-efficiency Fresnel zone plate reflector antenna is presented. The reflector consists of an inhomogeneous array of circular conducting rings printed on a grounded substrate. By adjusting the geometrical parameters of the rings and the distances between them, the reflector provides a space-varying phase correction required for focusing an incoming plane wave. Compared with a phase reversal zone plate, an average of 3-dB gain improvement and significant sidelobe reduction have been obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multilayer phase correcting fresnel zone plate reflector antennas

AbstractOwing to its flat nature and light weight etc., the Fresnel zone plate antenna is becoming very attractive for such applications as DBS reception and receive‐only VSAT. The disadvantages of low efficiency and high sidelobes of the simple and the phase reversing zone plates can be improved by using phase correcting techniques. In this paper, a systematic investigation on the efficiency and sidelobe performance of subzone phase correcting zone plate antennas is presented. The design of a form of multilayer phase correcting zone plate reflector is described. A quarter‐wave zone plate reflector constructed with three dielectric layers and metallized rings is reported, with measured peak efficiency of 55 per cent.

A high-efficiency quarter-wave zone plate reflector

A multilayered quarter-wave zone plate reflector antenna operating in the microwave range is presented. The theory for designing the reflector and experimental results are given. An efficiency of 55% was obtained with a prototype reflector antenna. >