## 4 Conclusions  
As a primary work to build an ISAC system, the sensing and communication antennas have been designed and integrated into a module. With the elemental components of the ISAC module developed in this paper applied to 6G fast data transmission and resolution-improved RF sensors, 4-branch and 128-branch power dividers and 1X4 and 8X16 array antennas have been realized to work at 28 GHz and 24 GHz as mmW frequencies, respectively. The components show good impedance matching performance at the aforementioned frequencies by overcoming high and harsh attenuation along the transmission lines embedded in the ordinary substrate. The 1D array antenna generates a fan beam typically used for 5G and 6G terminals, and the 2D array antenna radiates a very pointy beam, as presented in the design procedure for sensing. The 8 dBi 28 GHz antenna is helped by the 19 dBi 24 GHz antenna in setting the direction of communication. After making the module with these elements, their functions were verified in various tests of the LoS, reflection by a metal plane and the reflection with RS01 as the metasurface in sensing mode, communication mode, and in terms of the change in the total distance. Because of the highly directive beams for the sensing and communication links, the tests with the distance of 1m to 1.5 m, considering wavelengths 12.5 \(\times\) 10\({}^{-3}\) m and 10.7 \(\times\) 10\({}^{-3}\) m, do not show rapid degradation. According to the experiments, when the straight path of the LoS is bent to the round-trip path by the conductor plane or the metasurface, the strength of the returned signal tends to decrease in a non-ignorable scale. However, the measurement of the received signal at 28 GHz reveals that if the boundary condition of the reflecting surface is engineered to prevent power loss, it can be improved, seeing as there was an increment of 8 dB compared to the typical metal plane. Additionally, low interference from one operating frequency to another has been verified as an advantage of the proposed design. Inter-frequency isolation is over 15 dB. This research is applicable to the initial work for realizing an mmW ISAC device where the fixed angles of the radiated waves from the antennas and a relatively large area, which are limitations of the present structure, are enhanced by using beamformer chips and optimized size reduction.  
Conceptualization, S.K., Y.S. and J.K.; methodology, S.K., Y.S. and J.K.; software, W.K.; validation, J.K., H.P. and W.K.; formal analysis, W.K.; investigation, J.K., Y.S., S.S. and S.K.; resources, S.K.; data curation, H.P. and W.K.; writing--original draft preparation, J.K.; writing--review and editing, S.K.; visualization, J.K. and W.K.; supervision, S.K.; project administration, S.K. funding acquisition, S.K.. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Technology Innovation Program (Project Code: 20016463) and funded by the Ministry of Trade, Industry, and Energy (MOTIE, Republic of Korea).  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
[PERSON] as the lead author mentions that this research was supported by the MSIT (Ministry of Science and ICT), Korea, under the ITRC (Information Technology Research Center) support program (IITP-2023-RS-2023-0025906112182103820101,) supervised by the IITP (Institute for Information & Communications Technology Planning & Evaluation.  
The authors declare no conflicts of interest.