Frequency-tunable mobile phone antennas with matching circuits

Cognitive Radio systems require antennas and microwave components to be actively tuned for different parts of the frequency spectrum. In this paper results of a study of two antenna tuning techniques are presented. The first antenna is a dual-port antenna which is comprised of two capacitive-fed plates sharing one lower-band patch, operating at 5 mobile phone bands (GSM850/900/1800/1900/UMTS). The third port incorporating matching circuits will also be presented covering 2400–3600MHz, and at the same time, to obtain acceptable mutual couplings between ports with a low profile. The second antenna is a compact single-port PIFA antenna with a tunable matching network integrated into the feed line, enabling the impedance bandwidth to gradually operate at the DVB-H (Digital Video Broadcasting — Handheld) band 470–702MHz.