Application of a C-tuner to Aperture Tuning of a Handset Antenna Inspired by Characteristic Modes

In this paper, an approach to develop a tunable antenna for small terminals or smartphones is presented. Instead of tuning a self resonant antenna structure, a generic setup with a capacitive coupling element as common in current mobiles is used. To tune this antenna, the promising approach of aperture tuning is implemented. To realize this, a 5 bit C-tuner is used as tunable element at the antennas aperture. The positioning of the tuning element is shown based on a development process combining characteristic modes, full-wave field simulations and circuit simulations with Advanced Design System (ADS). Combined with a switched impedance tuning circuit, it is possible to tune this generic antenna element for low- and midband operation.