Dichroic Subreflector Research Articles

Challenges & opportunities in frequency selective surfaces for EMI shielding application: A theoretical survey

FSS provides enormous applications such as radomes, stealth technology, dichroic sub-reflector, photonic sub-reflector, military applications, antenna Technology and earth observing remote sensing instruments. Apart from this, Electromagnetic Interference shielding is the hottest research area due to advancement of mobile communication technology. The growing radiations from these mobile communication can be suppressed by transforming entire or aperture of wall in to FSS surface to protect highly sensitive equipment and human from health hazards. So this article presents the basics concepts, types and challenges of FSS especially for EMI shielding application and its theoretical investigations. Hence the various stop band filters have analyzed particularly in terms of unit cell dimension, element type and angular stability. Apart from these, tunable FSS are also discussed.

Inductive Frequency Selective Surface: An Application for Dichroic Sub-Reflectors

An Inductive Frequency Selective Surface (IFSS) self-standing dichroic sub-reflector is presented, which allows the transmission of two frequency bands and reflection of a third band. The operating frequency of the sub-reflector is designed to work at Ku, K and Ka frequency bands, intended for earth to space and space to earth satellite communications. The proposed unit cell is a Jerusalem cross intertwined with an Brigid’s cross. The IFSS is investigated using transmission line theory, along with equivalent-circuit model technique. It has been designed, and simulated using CST Microwave Studio and Advance Design Simulator (ADS). The cascade configuration of the IFSS is also investigated to improve frequency roll-off and bandwidth of the reflection and transmission coefficients. The IFSS has been manufactured using two-sided Photo Chemical Machining (PCM) technique, and has been experimentally characterized using an optical configuration, comprising two double ridged horn antennas connected to a VNA and a rotation system. Measured results are in good agreement with theoretical and simulation data, which validates the reliability of the design and manufacturing process.

Sharp transition frequency selective surface with concentric double fractal elements

A lightweight, low-cost, and single-layer frequency selective surface (FSS) with the concentric double fractal elements was designed for the dichroic sub-reflector of a dual-band high gain reflector antenna. This frequency selective sub-reflector diplexes the transmit (11.7–12.2 GHz) and receive (14–14.5 GHz) bands of a domestic satellite antenna, so both bands share the same large main reflector. It exhibits a sharp transition from stop-band to pass-band and a stable performance with varying incident angles and polarizations. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1388–1390, 2016

Multiband feed using coaxial configuration

We present design, analysis and test results of a dual-aperture coaxial multiband feed horn that operates at S, Ku, K and Ka bands. The design objectives are to achieve aperture efficiencies of 85% for S and Ku bands and 60% for K and Ka bands and cross-polarization level of −20 dB within 30 degree off-boresight for all bands. These values are deduced primarily from the reflector geometry, −10 dB reflector edge taper and moderate cross-polarization requirements for the secondary patterns. In our design the Ku, K and Ka bands are launched through a multiflared circular horn while the S band is launched through a coaxial horn. A method of moment based software is developed to analyze the structure including mutual coupling between the apertures. It is found that the aperture impedance significantly affects the S-band performance. For the high frequency bands, the mutual coupling between the circular and coaxial apertures plays an important role. The simulated results including mutual coupling effects agree well with the measured data. The multiband feed design allows a compact, low weight, single offset reflector configuration as opposed to a Cassegrain antenna system that requires two separate feeds and a dichroic subreflector to accommodate such widely separated bands. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. © 2011 Wiley Periodicals, Inc.

Scattering Analysis of Dichroic Subreflectors

ABSTRACT This paper presents an efficient technique developed to analyse dual reflector antenna systems operating with double curved dichroic subreflectors. The analysis is based on the Physical Optics integration of proper equivalent currents computed on the subreflector surface. The possibility of determining the optimum position of the dichroic subreflector in the antenna system, taking conveniently into account its finite thickness, is also discussed and evidenced through a meaningful example of design analysis. The same example gives to the reader an idea about the high performance achievable by dichroic antennas.

Analysis and design of double-layer frequency-selective surfaces

A dichroic structure consisting of two parallel arrays of crossed dipoles supported by various dielectric sheets is investigated. An efficient analysis method, based on a modal expansion that takes into account the interaction of the reactive field between the gratings, is outlined for this purpose. The method uses a Galerkin procedure combined with a generalised wave-matrix formulation. The analysis method is also implemented in a systematic design procedure, and the design of a double-layer grating structure intended for a dichroic subreflector operating at 10.7–11.7 GHz and 18.1–20.1 GHz is carried out.

Design of a dichroic Cassegrain subreflector

The design of a dichroic subreflector for a dual-frequency reflector antenna is described. This antenna consists of a Ku -band Cassegrain feed requiring the subreflector surface to be highly reflective at 13-15 GHz and a primary focus S -band feed requiring the subreflector to be transparent at 2.0-2.3 GHz. Such a performance is achieved by a surface of crossed dipoles printed on a dielectric sheet. The influence of parameters, dipole length, width and spacing, and the dielectric constant and thickness of the sheet on the reflection and transmission coefficients is experimentally evaluated. An analysis based upon the Floquent mode theory is shown to correctly predict the experimental results. The construction of a hyperbolic subreflector using the selected surface parameters is briefly described. As compared to a solid subreflector of identical shape, this dichroic subreflector produced a negligible loss (less than 0.1 dB) over a 13-15 GHz band. At the S band the loss was less than 0.2 dB over narrow selected bands and the axial ratio deterioration was also no more than 0.2 dB.