## 5 Conclusions  
In this paper, we presented a Ka-band DLTSA with EM absorbers for reducing the RCS for the cross-polarized incident wave at the X-band, such that the original radiation and impedance matching performance of an antenna without the absorbers are maintained. A double-layer tapered slot design was adopted to the DLTSA in this regard. It was found that the gain and maximum beam direction, as well as the impedance matching, show little difference after embedding the EM absorber layer to both sides of the tapered radiating slots. The thickness of the EM absorber layer was chosen to be as long as possible, while not affecting the radiating characteristics. The gain and radiation efficiency of the single DLTSA are 7.0 dBi and 88%, respectively. For comparison, refs. [13,14] showed more than 1 dB gain degradation by applying an absorber to TSAs.  
The RCS reduction characteristic of the DLTSA with an EM absorber layer was verified in a 4-by-4 array design with two 1-by-4 power dividers. It was found that the simulated reflection coefficients and radiation pattern show good agreement with the measurements, and the radiation patterns were maintained with the absorber layer in presence. The measured monostatic RCS was successfully reduced by 6.5 dB on average along the X-band for the cross-polarized incident waves. Although there is a quantitative difference in the values due to the measurement environment and size of the AUT, this work shows the high possibilities of applying EM absorbers at the front of a missile seeker designs with end-fire radiating elements. Extending the proposed design to a larger array with beam steering capability, while considering the environmental design considerations such as thermal and mechanical effects, remains as future work.  
Figure 11: Beam steering simulation results. (**a**) Phase excitation by 90\({}^{\circ}\). (**b**) Simulated 3D pattern at 35 GHz.  
**Author Contributions:** Conceptualization, W.K. and I-J.Y.; methodology, W.K., Y.K. and I-J.Y.; software, W.K., H.-D.C. and I-J.Y.; validation, W.K., J.J. and I.-J.Y.; formal analysis, W.K., Y.K., H.-D.C. and I-J.Y.; investigation, W.K., J.-B.K. and I-J.Y.; resources, W.K., Y.K., H.-D.C., J.-B.K. and I.-J.Y.; data curation, W.K., J.J. and I-J.Y.; writing--original draft preparation, W.K.; writing--review and editing, I.-J.Y.; visualization, W.K.; and supervision, I.-J.Y. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported in part by LIG Nex1, and in part by the BK21 FOUR Program of Chungnam National University Research Grant, 2022.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** The authors declare that they have no known competing financial interests or personal relation-ships that could have appeared to influence the work reported in this paper. [PERSON], [PERSON], [PERSON], [PERSON] are employees of LIG Nex1 Co., Ltd. The authors declare that this study received funding from LIG Nex1 Co., Ltd. The funder had no role in the design of the study; in the collection, analysis, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.