A Reconfigurable PIFA Using a Switchable PIN-Diode and a Fine-Tuning Varactor for USPCS/WCDMA/m-WiMAX/WLAN

A reconfigurable planar inverted-F antenna using a switchable PIN-diode and a fine-tuning varactor is presented for mobile communication applications. Selection of operating modes is achieved by switching the PIN-diode between radiators and tuning the varactor on an antenna's shorting line. Mode I, with the PIN-diode off and tuning the varactor, operates for USPCS (1.85-1.99 GHz), WCDMA (1.92-2.18 GHz), and WLAN (5.15-5.825 GHz). As a result, the varactor used to achieve frequency fine-tuning does not need a DC bias circuit and can expand the bandwidth without increasing the physical size. Mode II, with the PIN diode on and the fixed 0-V varactor, operates for USPCS and m-WiMAX (3.4-3.6 GHz). To optimize the antenna structure, a parametric analysis is performed by sweeping the length and width of the radiators. Furthermore, equivalent models of a PIN diode and a varactor are presented for accurate prediction of antenna performances which are also analyzed by varying diode parameters. All simulated results are confirmed with measured data. The peak gains show 2.84, 2.81, 1.25, and 1.49 dBi at USPCS, WCDMA, m-WiMAX, and WLAN, respectively.