Academic White Papers

Helical Lensed Ridged Horns

Synopsis

This white paper describes an antenna aimed at high power, ultra-wide band, circular polarisation applications. It is an unusual design, benefitting from the design capabilities of modern antenna design software and experience in both lensed and ridged horns. Modern manufacturing techniques are available for making such a design practicable. There are many types of circularly polarised antennas, but few capable of both ultra-wide bandwidth (e.g. 2-18 GHz), moderately high gain and high power. This antenna uses a conical helical ridge within a closed horn structure, together with a low dielectric constant internal lens. The basic idea is fairly clear, but design is not straightforward due to the very complicated internal mode structure. We have found that the use of a low dielectric insert can concentrate the field sufficiently to reduce unwanted modes to acceptable levels.

As far as we are aware, the design of a helical ridged antenna with an integral dielectric lens is quite new. An example of such an antenna is presented below. We would welcome the opportunity to develop this antenna if there was interest.

Effective parameter permittivity and user guide_epsmuest.jpg

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Dual polarisation monopulse feeds and applications

Synopsis

This white paper describes a minimal monopulse feed capable of producing sum and difference patterns in both azimuth and elevation directions with arbitrary polarisation over an extended ultra-wide band, 6-16 GHz. It may be used as a common feed as part of a parabolic reflector system. The feed is 4-fold rotationally symmetric with 8-ports and may be used in a number of configurations. Some of these configurations may be used to generate non-zero orbital and spin angular momentum radiation patterns for use in optimal communication and physics experiments.

Effective parameter permittivity and user guide_epsmuest.jpg

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Effective parameter (permittivity and permeability) estimator formulation and user guide

Synopsis

This user guide describes the basic algorithm, and the use of software using this algorithm, for estimating the relative complex permittivity and relative complex permeability of a slab of material in space. It is assumed that the material is homogeneous on a wavelength scale, but not necessarily on a sub-wavelength scale. This allows the method to be employed for meta-materials.

Effective parameter permittivity and user guide_epsmuest.jpg

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The mathematical formulation of QDAS, Q-par Dichroic Array Software

Synopsis

The document provides a detailed description of the more important elements of the math-ematical formulation. It should be of use to anyone seeking to write their own software and demonstrates the underlying capabilities of QDAS.

The mathematical formulation of QDAS_fssman.jpg

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The theory and design of provably optimal bandwidth Radar Absorbment Materials (RAM) using dispersive structures and / or Frequency Selective Surfaces (FSS)

Synopsis

Performance coefficients, design tools and analysis is provided for the synthesis of optimal radar absorbment materials (RAM). The importance of equivalent circuits is emphasised. The basic theory is quite general and valid for the metamaterial and frequency selective surfaces (FSS) composites containing piece-wise isotropic layered materials.

Provably optimal RAM using dispersive structure and  or FSS_fssram_iceaa.jpg

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The Physics of helicopter blade scintillation and some possible methods of investigation

Synopsis

The generation of light of the kind observed and under the conditions described can plausibly be explained using well known mechanisms. Basically, under most conditions any kind of friction caused by collision between non-conducting materials of different kinds, or between non-conducting materials and conductors, results in the accumulation of electric charge on one or the other material involved. This effect is known as triboelectric charging and is a well known mechanism for coronal discharges on aircraft. Unless there is a mechanism for immediate transfer of charge after the collisional event, the charge remains and can build up to levels sufficient to produce a visible corona discharge.

The Physics of helicopter blade scintillation.jpg

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Bianisotropic multilayer analysis software formulation and user guide

Synopsis

This document describes the formulation of theory for the plane wave excitation of multi-layered structures containing bianisotropic materials and surface impedance sheets. It also provides a user guide for the software constructed around the method and examples showing its use. One example shows the design of a novel octave bandwidth linear-to-circular reflector polariser.

Bianisotropic multilayer_layer.pdf

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Dispersion requirements of low-loss negative refractive index materials and their realisability

Synopsis

A necessary dispersion requirement is given for the effective relative permeability, μr(ω) and permittivity ǫr(ω) as a function of frequency for low-loss homogeneous dis-persive materials and negative refractive index materials in particular, if they exist at some dimensional scale D. The requirements are valid both for isotropic and uniaxial materials, the latter defined by material properties that are invariant under a rotation about a principal axis. Using asymptotic requirements at zero frequency and Foster’s reactance theorem, the general band-gap structure is given for low-loss materials. It is shown that such materials can only be achieved if the material exhibits finite band-gaps separating regions of positive and/or negative refractive index regions.

Dispersion requirements of low-loss negative refractive_negrefr.jpg

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User Guide for Q-par PO reflector analysis software (QPORAS)

Synopsis

This report documents our own in-house software (which, in this report, we will call QPO-RAS) intended for this purpose. This is not intended to compete with GRASP or similar general purpose analysis software, but it is adaptable and can be added and modified as and when desired. It is written in FORTRAN for use on a Linux platform, but may be ported to other systems since no system-dependent calls are implemented.

User Guide for Qpar_PO_userg.jpg

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Squint reduction in spiral antennas using unbalanced feeds

Synopsis

This document describes squint problems with spiral antennas using an unbalanced feed line. It includes a dual mode analysis, a description of the physics of the problem based on empirical evidence and an approximate field model. Examples are presented showing how squint reduction can be achieved.

Squint reduction in spiral antennas using_repnote_squint.jpg

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On the possibility of UWB passive microwave imagery from static discharge effects.

Synopsis

It is well known that spark transmitters can be sources of ultra wide band (UWB) radiation. It is also known that high voltage low energy static discharges are ubiquitous in nature, whenever there is friction
between surfaces. We provide a simple electromagnetic model and suggest that it is feasible to construct an ultra wide band correlator capable of imaging a region of space containing such sources. This would permit a new window of observation on several physical processes, with applications ranging from observations of ice flows to covert operations..

On the possibility of UWB passive microwave_spark1.jpg

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To find out more about Steatite Antennas or discuss specific requirements please contact on +44(0)1568 617920, or email  sales.antennas@steatite.co.uk 

For further information on all capabilities please download Steatite Company Overview.


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