Electromagnetic Absorber-Embedded Ka-Band Double-Layer Tapered Slot Antenna for the Reduced Radar Cross Section at X-Band  
[PERSON]  
1 Department of Electrical Engineering, Chungnam National University, Daejeon 34134, Republic of Korea; [EMAIL_ADDRESS]  
[PERSON]  
2 LIG Nex1 Co., Ltd., Yongin-si 16911, Republic of Korea; [EMAIL_ADDRESS] (YK.); [EMAIL_ADDRESS] (H.-D.C.); [EMAIL_ADDRESS] (J.J.); [EMAIL_ADDRESS] (J.-B.K.)  
[PERSON]  
2 LIG Nex1 Co., Ltd., Yongin-si 16911, Republic of Korea; [EMAIL_ADDRESS] (Y.K.); [EMAIL_ADDRESS] (H.-D.C.); [EMAIL_ADDRESS] (J.J.); [EMAIL_ADDRESS] (J.-B.K.)  
[PERSON]  
2 LIG Nex1 Co., Ltd., Yongin-si 16911, Republic of Korea; [EMAIL_ADDRESS] (Y.K.); [EMAIL_ADDRESS] (H.-D.C.); [EMAIL_ADDRESS] (J.J.); [EMAIL_ADDRESS] (J.-B.K.)  
[PERSON]  
1 Department of Electrical Engineering, Chungnam National University, Daejeon 34134, Republic of Korea; [EMAIL_ADDRESS]  
Footnote 1: email: {[EMAIL_ADDRESS], jjkkwon007@ligneexl.  
been interesting efforts to place radar absorbing materials (RAMs) around the TSAs [13; 14] to reduce the RCS. In [13], an RAM plane is modified with an array of metamaterial unit cells, and is placed orthogonally to the back-end of a TSA. From the simulated results, it was found that the monostatic RCS is reduced for the cross-polarized incoming waves, but at the expense of an antenna gain degradation of about 1.2 dB. The RCS measured for the incoming E-field standing perpendicular to the E-plane of the antenna is called cross-polarized RCS. In [14], the RAM was mounted on the double exponentially tapered slots. But the overall radiation efficiency is still degraded by 20% because the current flowing over the radiating aperture is impeded. The maximum gain was degraded from 7.4 dBi to 6.3 dBi. In [15], magnetic absorbing material was utilized to cover the ground plane of a TSA array in a triangular grid form for the effective attenuation of the scan blindness. The scan blindness is one of the important parameters in the design of array antennas. It is a phenomenon mainly caused by mutual coupling, which almost cancels the radiation characteristics at a certain scan angle [16]. Such significant radiation performance degradation of an array antenna should be avoided. In [15], the scan blindness and the beam scanning performance were mainly studied and specific measured or simulated results on the cross-polarized RCS reduction were not provided.  
Under this background, we propose a novel configuration of a Ka-band double-layer TSA (DLTSA), in which EM absorbers are embedded for reducing the X-band cross polarization monostatic RCS. It is found that the current flow along the feedline and the tapered radiating aperture is well maintained even with the presence of the EM absorbers in the proposed design. It results in the non-degradation of the antenna gain and beam direction when compared to those of the original DLTSA without the EM absorbers, while reducing the cross polarization monostatic RCS at the X-band. Such performance is demonstrated with a 4-by-4 DLTSA array. All the computed expectations in this work were carried out using the CST Studio Suite 2023, and the results are verified experimentally.