Stable‐multiband frequency reconfigurable antenna with improved radiation efficiency and increased number of multiband operations

Abstract

In this study, a multiband frequency reconfigurable antenna is presented. The proposed antenna can switch among fixed GSM850/900 MHz, LTE1600/1700/1800 MHz and ISM2400 MHz bands through switchable, single, three double, and two triple band modes. The multiband operation is obtained using a spline-based radiator and two open-ended rectangular slot-resonators (RSRs). Three series configurations of PIN diode radio-frequency (RF) switches are integrated into RSRs to activate and deactivate it. The position of RSRs and RF switches is precisely optimised to obtain the desired operating bands and the input scattering parameter ( S 11) below −10 dB. RF switches #1–3 are turned ON and OFF to transfigure the current distributions on the radiator resulting in the frequency band-switching operation. It is shown that the integration of RSRs and PIN diode RF switches into the antenna structure degrades the radiation efficiency. To improve the radiation efficiency, the antenna is fabricated on a low dielectric constant multilayered substrate built using RT/Duroid 5880 laminates and an air gap. The increased multiband operation, good radiation efficiency, omnidirectional radiation pattern, and sufficient co-cross polarisation isolation are obtained in all operating bands. The prototype of the antenna is fabricated and fairly good agreement is seen amongst simulated and measured results.