1. School of Electronics,
Electrical Engineering and
Computer Science
Queen’s University Belfast
ELE8060 MSc Project
Project Title: Planar Spirals for Multiband Antenna Radiators
Student Name: Evangelos Stergiou
Student Registration Number: 40118088
Project Supervisor: Dr A. Schuchinsky
Project Moderator: Dr R. Cahill
4 September 2014

2. i
Abstract
The objective of this project is to design Paired Spiral Resonator (PSR) structures to
operate as multiband radiators. Squared Spiral PSRs will be used to regard the
dimensions of the ground plane, substrates, spirals width and gap as previously
reported in [10] and [11]. Designs of Single Arm PSR and Dual Arms PSR will be
analysed considering the two main types of feeding, edge discrete port and coaxial
probe feeding techniques, as previous studies have demonstrated that these two
techniques present considerably better performance compared to others and their
radiation characteristics are approximately similar.
Each technique has advantages and disadvantages in terms of convenience of
implementation and radiation characteristics. An analysis based on antenna parameters
such as radiation pattern and efficiency, mismatch losses, directivity, 3dB beamwidth,
polarization pattern and current distribution will be held in order to investigate the
performance of the PSRs. Improvements in the performance of the designed PSRs will
be further investigated, by rotating the alignment of the bottom spiral in each case.
The design of the PSRs and their simulations will be supported with the use of CST
Microwave Studio 2011 (Computer Simulation Technology).

3. iii
Project Outline
The purpose of this report is to present all the key aspects which are about to be
analysed in the MSc Final Year Project, entitled ‘’Planar Spirals for Multiband Antenna
Radiators’’. Planar spirals constitute one of the major basic elements of printed circuit
and antennas, in the recent years. The structure and the advantages of the stacked and
interwoven planar spirals make them suitable for the design of frequency sensitive
surfaces (FSS) and radiating elements of substantially sub-wavelength size. The design
of these structures contributes additional degrees of freedom in tailoring multiband
antennas and their radiation patterns.
The purpose and the objectives of this project are to investigate configurations of
stacked and interwoven pair spiral resonators (PSR) for multiband and tunable antenna
radiators. The impact on the antenna’s parameters will be analysed in order to achieve
the high performance of the interwoven and stacked spirals. The planar resonator
designs and the configurations will be implemented with the use of electromagnetic
simulators and especially through the use of Computer Simulation Technology (CST)
Microwave Studio 2011. The optimization of the layout and the design will be based on
physically realizable geometries accordant to modern fabrication techniques. The
design, the configurations and the measurement of the performance will be based on
different types of feeding techniques and proposing methods to improve the
performance of the PSRs.
The learning outcomes of this project are:
1. The properties of the convoluted spiral resonators and the basic principles of
their design for antenna applications.
2. The modelling concepts for the design of complex electromagnetics structures,
antenna radiating elements and feeders.
3. Skills in operating the full-wave electromagnetic simulation tools (CST
Microwave Studio) and their use for the design of microwave antennas.

4. v
Table of Contents
Abstract ............................................................................................................................ i
Declaration of Originality ................................................................................................. ii
Project Outline ................................................................................................................ iii
Acknowledgements ........................................................................................................ iv
Table of Contents ............................................................................................................ v
List of Figures ................................................................................................................ vii
List of Tables ................................................................................................................... x
1 Introduction in Rings and Spirals Resonators ........................................................... 1
1.1 Split Ring Resonators ......................................................................................... 1
1.2 Multiple Split-Ring Resonators ........................................................................... 1
1.3 Spiral Resonators ............................................................................................... 2
2 Definitions of Antenna Terms .................................................................................... 4
2.1 Radiation Pattern ................................................................................................ 4
2.2 Directivity and Radiation Density ........................................................................ 4
2.3 Radiation Pattern Lobes and Beamwidth ........................................................... 5
2.4 Antenna Efficiency .............................................................................................. 6
2.5 Gain .................................................................................................................... 6
2.6 Bandwidth ........................................................................................................... 6
2.7 Return Loss ........................................................................................................ 7
2.8 Polarisation ......................................................................................................... 7
3 Feeding Techniques.................................................................................................. 9
3.1 Edge Discrete Feeding ....................................................................................... 9
3.2 Coaxial Probe Feeding ..................................................................................... 10
3.3 Proximity Coupled Feeding .............................................................................. 11
3.4 Aperture Coupled Feeding ............................................................................... 12
4 Single Arm Stacked PSR with Edge Discrete Port Feeding .................................... 14
4.1 Single Arm Pair Spiral Resonator Configuration ............................................... 14
4.2 Edge Discrete Port Feeding ............................................................................. 16
4.3 Effect of Variation in Length of Inner Arm ......................................................... 21
4.4 Effect of Bottom Spiral Rotation ....................................................................... 23

5. 4.5 Effect of Differentiation in Materials .................................................................. 27
5 Single Arm Stacked PSR with Coaxial Probe Feeding ........................................... 31
5.1 Coaxial Probe Feeding at the Terminal of the Spiral ........................................ 31
5.2 Effect of Bottom Spiral Rotation ....................................................................... 35
5.3 Coaxial Probe Feeding at the Centre of the Spiral ........................................... 37
6 Dual Arms Stacked Pair Spiral Resonators ............................................................. 40
6.1 Dual Arms PSR Configuration .......................................................................... 40
6.2 Coaxial Probe Terminals Fed Dual Arms PSR ................................................. 42
6.3 Edge Discrete Port Fed Dual Arms PSR .......................................................... 46
6.4 Coaxial Probe Centres Fed Dual Arms PSR .................................................... 50
6.5 Coaxial Probe Terminal and Centre Fed Dual Arms PSR ................................ 55
6.6 Effect of Bottom Spiral Rotation ....................................................................... 59
6.6.1 Bottom Spiral Rotation in Coaxial Probe Centres Fed Dual Arms PSR ..... 59
6.6.2 Bottom Spiral Rotation in Coaxial Probe Centre and Terminal Fed Dual
Arms PSR ............................................................................................................... 61
6.7 Effect of Shorting-Pin ........................................................................................ 62
6.7.1 Coaxial Probe Centre Fed Dual Arms PSR, Shorting-Pin at the Centre .... 62
6.7.2 Coaxial Probe Terminal Fed Dual Arms PSR, Shorting-Pin at the Centre . 64
6.8 Effect of Shorting Pin with Bottom Spiral Rotation ............................................ 66
6.8.1 Bottom Spiral Rotation in Coaxial Probe Centre Fed Dual Arms PSR,
Shorting-Pin at the Centre ....................................................................................... 66
6.8.2 Bottom Spiral Rotation in Coaxial Probe Terminal Fed Dual Arms PSR,
Shorting-Pin at the Centre ....................................................................................... 68
7 General Discussion ................................................................................................. 70
8 Conclusions ............................................................................................................ 71
9 References .............................................................................................................. 73
Appendices .................................................................................................................... 75
Appendix I – Absolute Radiation Patterns of Single Arm Edge Discrete Port Fed PSR
under Real and Ideal Conditions ................................................................................ 75
Appendix II – Absolute Radiation Patterns of Dual Arms Coaxial Probe Centre Fed
PSR, Shorting-Pin at the Centre under Real and Ideal Conditions ............................ 84
Appendix III – Absolute Radiation Patterns of Dual Arms Coaxial Probe Terminal Fed
PSR, Shorting-Pin at the Centre under Real and Ideal Conditions ............................ 89
vi