Tim Brown's Thesis - Antenna Diversity for Mobile Terminals

My thesis is entitled antenna diversity for mobile terminals with the aim to create a new modelling means by which the designer can analyse the properties of mobile terminal antennas as a means of optimising their diversity performance and also the efficiency and mean effective gain.

The thesis itself can be downloaded in pdf from here (3MB)


Antenna diversity has been used at the base station in mobile communications as a way to reduce the impact of multipath fading for many years. At present, network operators in the Far East have also implemented antenna diversity at the mobile and it is likely that with upcoming third generation and fourth generation mobile networks this will become more common. Despite being already used, the mechanisms for successful diversity antennas at the mobile are largely unstudied and how their performance can be optimised is not well understood. Therefore there is a need for a new method from which the designer can evaluate the diversity performance of mobile antennas and use the results to determine how they are performing.

This thesis presents a new diversity modelling technique that can be used to evaluate the main antenna diversity contributions at a mobile terminal namely spatial, polarisation and angular diversity. Many mobile terminals will consist of a combination of all three and so evaluating them will assist the designer to find why there is diversity. Further to this it will present simulations that show how the results should be interpreted correctly for the benefit of the designer. Optimising the efficiency as well as the diversity is an important factor at the mobile, which will also be considered.

Results are also presented for two case study applications of the evaluation method. The first is a typical mobile handset with a diversity antenna and the other examines the diversity potential of an Intelligent Quadrifilar Helix Antenna. Finally the thesis ends with a proposal for a mobile fading environment simulator to verify the diversity performance of mobile handsets with different angle of arrival environments that will be of benefit in the future.

Key words: Antenna diversity, complex correlation, envelope correlation, spatial diversity, angular diversity, polarisation diversity, angle of arrival, cross-polar ratio, mean effective gain, intelligent quadrifilar helix antenna

Summary of Original Contributions to Knowledge

1. Modelling and characterising polarisation diversity of both mobile and static fading environments.
2. Derivation of spatial diversity at the mobile for both horizontally and vertically spaced points at the mobile such that the diagonal spatial correlation can be evaluated.
3. Calculation of spatial diversity produced at the receiver in the presence of mutual coupling and impedance differences in the antennas.
4. Derivation of angular diversity characteristics at the output port of the antennas with impedance effects considered.
5. The method for evaluation of diversity at the mobile from measurements or simulations carried out.
6. Analysis of the contributions of spatial, angular and polarisation diversity and how they interact to affect the overall diversity performance.
7. Evaluation of the diversity characteristics of a typical mobile handset and what the main contributions are.
8. Analysis of the diversity potential of an Intelligent Quadrifilar Helix Antenna (IQHA).

Tim Brown