Heterogeneous mixtures for synthetic antenna substrates

Heterogeneous mixtures have the potential to be used as synthetic substrates for antenna applications giving the antenna designer new degrees of freedom to control the permittivity and/or permeability in three dimensions such as by a smooth variation of the density of the inclusions, the height of the substrate and the manufacture the whole antenna system in one process. Electromagnetic, fabrication, environmental, time and cost advantages are potential especially when combined with nano-fabrication techniques. Readily available and cheap materials such as Polyethylene and Copper can be used in creating these heterogeneous materials. These advantages have been further explained in this thesis. In this thesis, the research presented is on canonical, numerical and measurement analysis on heterogeneous mixtures that can be used as substrates for microwave applications. It is hypothesised that heterogeneous mixtures can be used to design bespoke artificial dielectric substrates for say, patch antennas. The canonical equations from published literature describing the effective permittivity, ε_eff and effective permeability, μ_eff of heterogeneous mixtures have been extensively examined and compared with each other. Several simulations of homogenous and heterogeneous media have been carried out and an extraction/inversion algorithm applied to find their ε_eff and μ_eff. Parametric studies have been presented to show how the different variables of the equations and the simulations affect the accuracy of the results. The extracted results from the inversion process showed very good agreement with the known values of the homogenous media. Numerically and canonically computed values of ε_eff and μ_eff of various heterogeneous media were shown to have good agreement. The fabrication techniques used in creating the samples used in this research were examined, along with the different measurement methods used in characterising their electromagnetic properties via simulations and measurements. The challenges faced with these measurement methods were explained including the possible sources of error. Patch antennas were used to investigate how the performance of an antenna may be affected by heterogeneous media with metallic inclusions. The performance of the patch antenna was not inhibited by the presence of the metallic inclusions in close proximity. The patch measurement was also used as a measurement technique in determining the ε_eff of the samples

Microstrip patch antennas on substrates with metallic inclusions

This paper considers the design of microwave patch antennas using bespoke substrates. The permittivity of the substrate is controlled by inserting small scale metallic inclusions into a host medium and can be obtained using an S-parameter inversion algorithm on the results of plane-wave simulations. Electromagnetic simulations have been used to compare the performance of the patch on the heterogeneous substrate to standard homogeneous substrate

EM properties of synthetic media

EM properties, dielectric constant and radiation, of spherical and cuboidal particle inclusions forming volumetric media will be shown. Examples of a dielectric resonator and patch antenna will be discussed in the full paper

Antenna performance on quasi synthetic media

While we seem to be experiencing a material evolution by applying unique properties of metamaterials, such as negative constitutive parameters and to some extent cloaking phenomena, not much attention has been paid in the practical suitability of synthetic materials towards antenna designs. The antenna designer is often faced with a judicious choice of:- complexity in the conducting/radiating shape, substrate and radome parameters, cost as well as ever increasing environmental effects both in the construction but also in the disposal of the antenna as part of a recycling process. This paper will outline some of the hypotheses and processes that underpin our terminology of quasi synthetic media and will proceed to illustrate how one can obtain a variety of dielectric (and magnetic) effective contrasts from 3-D structures containing either dielectric or conducting micro particles. Some representative patch designs are considered to indicate how one could replace cumbersome conventional design and manufacturing processes by using nanotechnology and additive manufacturing

Microwave antennas and heterogeneous substrates using nanomaterial fabrication techniques (Invited paper for ICEA11)

By exploiting the enhanced physical properties of nanomaterials and the advancement in nanotechnology, alternative methods of fabricating microwave antennas can be conceived. This paper will discuss the potential manufacturing advantages as well as different fabrication methods. By controlling the location of metallic and dielectric particles, integrated antennas and substrates can be made in one process. Electromagnetic advantages result from being able to add inclusions with different electrical properties into the host substrate and thereby create a new effective permittivity and permeability. This paper will review and analyse methods for calculating these effective properties

Patch antennas with heterogeneous substrates and reduced material consumption enabled by additive manufacturing techniques

This paper investigates the concept of creating substrates with heterogeneous dielectric properties. By suitably locating areas of low and high permittivity, the second resonance can be moved closer to the 1st resonance and multiband antennas can be created. By combining, the resonances, the bandwidth of the antenna can be increased

An analytical approach to modifying the properties of dielectric substrates composed of nanomaterials

The aim of this research is to fabricate antennas and dielectrics out of nanomaterials. This method has the potential of integrating the whole antenna structure into one process. Since nanomaterials are extremely small, larger structures (~mm) can be created by suitably arranging many such particles (metallic and/or non-metallic), and thus resonance at microwave frequencies can be achieved. Fabrication and physical advantages include potentially faster fabrication processes and reduced production costs [1]. Using nanomaterial fabrication methods will enable novel and bespoke substrate properties, by controlling the size and volume ratio of the particles. Electromagnetic advantages (bandwidth, size and efficiency) can be achieved by varying the local permittivity with the local electric field strength, or by creating substrates with equal permittivity and permeability

Study on the variation in dielectric properties of heterogeneous substrates composed of nanomaterials

An analytical study of heterogeneous substrates created by including small particles arranged in a cubic lattice within a host medium is presented in this paper. Rapid advances in nanomaterial fabrication techniques will allow in the near future, heterogeneous samples to be created with nano or microsized inclusions, and this paper investigates the electromagnetic (EM) properties of these structures. Analytical equations by various authors for the effective permittivity and permeability of such artificial materials have been analysed and compared over microwave frequencies. The particle size, spacing and frequency were examined individually to understand their role in determining the effective EM parameters of the heterogeneous mixture. Furthermore, results from FDTD simulations with micro-sized cuboids were processed using an inverse scattering algorithm to obtain the effective permittivity and permeability of these heterogenous structures using a complimentary technique. The canonical formulations showed reasonable agreement with the EM simulations and the two methods can be used to design novel dielectric substrates

Designing multi-band and high bandwidth antennas with heterogeneous substrates

This paper investigates the concept of creating substrates with heterogeneous dielectric properties. By suitably locating areas of low and high permittivity, the second resonance can be moved closer to the 1st resonance and multiband antennas can be created. By combining, the resonances, the bandwidth of the antenna can be increased

Designing multi-band and high bandwidth antennas with heterogeneous substrates

This paper investigates the concept of creating substrates with heterogeneous dielectric properties. By suitably locating areas of low and high permittivity, the second resonance can be moved closer to the 1st resonance and multiband antennas can be created. By combining, the resonances, the bandwidth of the antenna can be increased