Broadband tuning of mobile terminal antennas

Risto Valkonen, Jari Holopainen, Clemens Icheln, and Pertti Vainikainen

In the paper, broadband frequency tuning of mobile handset antennas using switches and passive reactances is studied. The idea is applied to a compact coupling element antenna, for which a dual-band (E-GSM900 and GSM1800) tuning circuit is designed and prototyped. The objective was to have a sufficient impedance bandwidth and good efficiency. The 6-dB bandwidth requirement is fulfilled at both frequency bands and the measured maximum total efficiency at both frequency bands is about 50 %.

Using better switches and an optimised tuning topology could still improve efficiency. However, the results of the study indicate that broadband frequency tuning of small antennas is possible.