Ultra-Thin Mm-Wave Filtering Antenna with Improved Bandwidth and Frequency Selectivity

In this paper, an ultra-thin millimeter-wave filtering antenna with improved bandwidth and frequency selectivity is proposed. The antenna is composed of a 0.3 mm thick substrate integrated cavity (SIC) with a crossed slot etched on the top and a probe feed, featuring a very simple structure and reduced profile. In this design, the resonant modes of the cavity, the probe feed and the crossed slot are innovatively combined to form a 3<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup>-order filtering response without resorting to extra resonant structure. Due to the opposite current induced by the crossed slot, two radiation nulls are introduced at the lower and higher band edges, resulting in a very sharp roll-off between the pass and stop bands. The principles of the antenna are analyzed with a detailed parametric study. For demonstration, the antenna is fabricated and tested. The results show an impedance bandwidth of 24.1-25.5 GHz and a gain of 5.7 dBi. The gain suppression is more than 10 dB within 250 MHz (FBW<1%).