Reconfigurable antennas for GSM and WLAN applications

Abstract

Design of a frequency reconfigurable antenna that could switch between GSM 900MHz and WLAN 2400 MHz is presented. The switchable antenna is realized in the form of GSM and WLAN patches. The design presents a novel nested patches structure with a proper slot width to isolate the two nested patches.

A probe feed is used to feed the antenna structure. Determination of a single common suitable location to feed to feed both the patches was undertaken. This feed location satisfies the impedance matching criterions.

Simulations were carried out with ideal switches that switch the antenna between GSM and WLAN bands. When GSM band is desired, the switches used are conducting stubs whereas in the WLAN mode the conducting stubs were removed leaving a bare open slot between the two patches. Optimum number of switches and locations of the switches were determined through to obtain the best performance in GSM band with minimal trade-off for the performance in the WLAN band.

A prototype antenna was fabricated with commercially available diodes used for switching between the two frequency bands. DC biasing lines were drawn from the top surfaces of the nested antenna. Measurement results demonstrate the correct switching between the two frequency bands. Good reflection coefficients were observed.