Design of conformal antennas for telephone handsets

Student: Andrew Causley

Supervisor: Marek Bialkowski

Category: Engineering Thesis Project - Communications

Modern cellular phone systems currently operate at a number of frequency bands, the most common being 900MHz, 1.8GHz and 2.0GHz. As mobile phones are becoming smaller it is not feasible to simply equip the handset with an array of antennas, each tuned to a specific frequency band. This has resulted in a demand for antennas that can operate at multiple bands without the need for multiple antennas. The Inverted-F Antenna (IFA) has been demonstrated to be capable of operating at multiple frequencies with the initial results very encouraging.

Another approach available in dealing with the ever-diminishing space available on handsets is to conform the antenna. This involves wrapping the microstrip antenna around a cylindrical surface. The results of this approach using the IFA are encouraging, especially in terms of space minimization, bandwidth enhancement and return loss reduction.

The purpose of this thesis is to design a conformal antenna for a mobile handset. The first step was to choose a suitable planar triple-band antenna capable of operating at 900MHz, 1.8GHz and 2.0GHz. The antenna that was selected for this thesis is the E-shaped planar IFA. This antenna can easily be tuned for correct frequency operation and possess a compact design. The design was created using FEKO, an electromagnetic simulation software package. Once the planar version of the antenna was simulated, the antenna was made conformal.

By using the optimised dimensions obtained from the planar IFA and applying them to the conformal IFA, it was found that there was a reduction in quality of the far-field patterns and the return loss values for similar resonant frequencies. Therefore further work is required to refine the conformal IFA.

Thesis Document (PDF)