Dual Band Cavity-Backed Filtering Antenna with Modified Coupling Slot Structure

In this study, the loading stub technique is proposed to convert a wideband $2 \times 2$ full metal cavity-backed antenna into a dual band antenna for satellite communication (SatCom) systems. A wideband $2 \times 2$ cavity-backed antenna is converted to a dual-band antenna by simply adding stubs to the conventional coupling slot structure, which act as a filter. The filtering antenna does not change the wideband antenna’s lateral and longitudinal dimensions and does not distort gain and radiation characteristics within in-band frequency regions. By integrating these stubs, the undesired frequency band of 12.5 - 13.75 GHz between Rx (10.7 - 12.5 GHz) and Tx (13.75 - 14.5 GHz) in-bands at Ku -band is effectively suppressed, which improves isolation and lowers interference. The simulated fractional bandwidths (FBW) for $\left|S_{11}\right|\lt -10$ dB are 15.78% $(10.68-12.51 \mathrm{GHz})$ and $8.1 \%(13.74-14.9 \mathrm{GHz})$ at the Rx and Tx bands, respectively. The peak gain values range from 13.06 to 13.92 dBi at Rx and 13.57 to $\mathbf{1 4. 2 4} \mathbf{~ d B i}$ at Tx bands. Besides, the out-of-band rejection level reaches 20.7 dB at 13 GHz while covering the entire Rx and Tx bands of the Ku-band.