Pin diodes and their impact on reconfigurable compact microstrip antennas with high frequency-ratio

This work presents a study of the impact of PIN diodes on the performance of reconfigurable compact microstrip antennas with high frequency-ratio. To this purpose, two frequency reconfigurable microstrip antennas with a frequency-ratio of 3 (868 MHz and 2.45 GHz ISM bands) and a different degree of compactness have been designed and measured for various PIN-diode configurations. The results show the derivative effects of using PIN diodes in the conditions mentioned, namely current cancelation, power dissipation, and frequency shift, and how to reduce their impact. The most significant repercussion is in the radiation efficiency, which can be enhanced from 46 to 74% using a less compact design, and by reducing the forward resistance of the PIN diode, what increases the radiation efficiency by a factor of 4.