A Reconfigurable SIW Cavity-Backed Slot Antenna With One Octave Tuning Range

A reconfigurable Substrate Integrated Waveguide Cavity-Backed Slot (SIW-CBS) antenna is presented with one octave tuning range and six different tuning states using a new tuning method. The method is based on loading the SIW cavity with shortening posts and manipulating the field distribution within the cavity. This tuning method shifts up the operating frequency of the antenna. Based on the number of the posts and their location, this frequency shift can be controlled. Benefiting from a two-layer structure and therefore being totally isolated from the biasing circuit, the CBS antenna can be easily tuned by switching the posts using p-i-n diodes. Using this technique a frequency tuning ratio (f_TR = f_up/f_low) as high as an octave (1.1-2.2 GHz) is achieved. The impedance and radiation characteristics of the CBS antenna are presented and discussed. The antenna shows similar radiation patterns with low cross-polarization levels and high front to back ratio for all six states. To the authors´ knowledge this is the first presentation of a SIW-CBS tunable antenna with one octave tuning and also the technique used for antenna tuning.