Bandwidth-optimal single-tunable-element matching network for antenna tuning in mobile handsets

This paper presents a single-tunable-element matching network that is optimized for the GSM850 and GSM900 bands. It is designed to counteract the detuning of mobile handset antennas by optimizing the transducer gain of the network. A simple model that emulates the antenna detuning effects based on extensive measurements from the literature is first presented. Based on this model it is shown that a matching network with a single tunable element suffices to cover the two aforementioned bands. Implementations for a planar inverted-F antenna (PIFA) as well as a proof-of-concept for the iPhone 4™ antenna are presented. The measured results, in good agreement with the modeled data, indicate that transducer gain improvements of up to 3.5 dB (53%) and 5.6 dB (57%) can be obtained for the PIFA and iPhone 4™ implementations, respectively.