Transferring the growing amount of data calls for wider bandwidths in new wireless standards. For the mobile antennas, which have to be squeezed to a very limited space, this poses quite a challenge for impedance matching, if efficiency is not to be sacrificed. Earlier, wideband matching was studied as a rather theoretical problem, but this work takes a practical viewpoint to produce readily applicable results. The goal is to utilize circuit elements to improve the performance of handset antennas. Because the number of matching elements is to minimized in practical designs, this work focuses particularly on three-element matching circuits. The presented efficient procedure for determining the available bandwidth with a certain matching topology, i.e., the bandwidth estimator, enable accounting for the matching circuit from the beginning of the antenna design process. Furthermore, evaluating the potential of different radiating structures becomes feasible. In mobile systems, the desired frequency band consists of two passbands, and therefore finding methods for dual-band matching is reasonable. This work presents how any two matching circuits designed separately for frequencies f1 and f2 can be converted into a dual-band matching circuit operating both at f1 and f2. In addition, simple design equations for dual-band matching are given. A dual-band matching can be realized also with two radiating elements. This widens the study to illustrate how bandwidth estimators can be used to design matching circuits for multiple ports. Moreover, it is shown that bandwidth estimator analysis offers a suitable starting point for practical design - the simulations and measurements are in good agreement. Finally, the work introduces other ways to improve antenna performance with aid of circuit elements and bandwidth estimators.
|Translated title of the contribution||Laajakaistaisten sovituspiirien hyödyntämisestä älypuhelimien antennien suunnittelussa|
|Publication status||Published - 2015|
|MoE publication type||G5 Doctoral dissertation (article)|
- impedance matching
- mobile antennas
- capacitive coupling element