Design and development of an annular slot antenna (ASA) with a reconfigurable radiation pattern

This paper discusses the use of pin diodes to modify the radiation pattern of an annular slot antenna (ASA) keeping constant the frequency of operation. The planar antenna is fabricated on the top side of a Duroid substrate and the microstrip feeding line with the matching network is fabricated on the back side of the board. The design frequency is 5.8 GHz. Pin diodes are used to short the ASA in pre-selected positions along the circumference. As a result of the short, the direction of the null in the plane defined by the circular slot changes. As a proof of concept two pin diodes are placed symmetrically to the feeding line and 45 degrees away from the feeding line direction. As a result, the direction of the null shifts and is aligned with the direction defined by the circular slot center and the diode. Consequently a reconfigurable radiation pattern is accomplished. Return loss and radiation pattern measurements and simulations are presented and demonstrate a very good agreement.