A FREQUENCY-SELECTING TECHNIQUE FOR MOBILE HANDSET ANTENNAS BASED ON CAPACITANCE SWITCHING

This paper introduces a mobile switchable antenna for long term evolution (LTE) of the 4th generation (4G), applicable to all mobile service bands. The validity of this antenna is assessed by design, realization, and measurement. A new frequency-selecting method is used in the proposed antenna, based on capacitance switching among four states. Due to the limited antenna space in existing terminals, it is quite difficult to cover the entire low band with a single antenna. To overcome this difficulty, three single-pole double-throw (SPDT) switches, one 74HC04, and four capacitors are used. The resulting antenna covers the LTE (698-798 MHz) and GSM (824-960 MHz) bands in the low-band characteristic by realizing four capacitance states and at the same time covers the DCS (1710-1880 MHz)/PCS (1850-1990 MHz)/WCDMA (1920-2170 MHz) bands in the high-band characteristic. The antenna provides a gain of -1.04-6.00 dBi, a radiation efficiency of 32.73-74.99%, and omni-directional characteristics in the H-plane. Because of this outstanding performance, it is expected that the new frequency-selecting technique will be applied in 4G mobile communication terminals.