## 3 Integrating the Antennas for RF Sensing and Communication and Experiments
This 8 dB jump indicates that when the reflecting surface is intentionally built for tilting the angle of reflection and gathering the electromagnetic flux more on to the reflection segment for either a sensing or communication link, the signal strength can be as high as the level of the LoS even when taking a detour, such as with the RIS. Two useful pieces of information are obtained in the following paragraphs. The first piece of information is related to the following mathematical expressions:  
\[P_{RF\_RX}|_{Dist\_Ref}=\zeta\times\frac{|E_{0}|_{Freq.}}{Dist\_Ref}^{2} \tag{1}\]  
\[P_{RF\_RX}|_{Dist\_New}=\zeta\times\frac{|E_{0}|_{Freq.}}{Dist\_New}^{2} \tag{2}\]  
\[\Delta P_{RF\_RX}[\mathrm{dB}]=P_{RF\_RX}|_{Dist\_New}[\mathrm{dB}]-P_{RF\_RX }|_{Dist\_Ref}[\mathrm{dB}]=10 log\_10\,\frac{Dist\_New}{Dist\_Ref}^{2} \tag{3}\]  
where \(P_{RF\_RX}\), \(|E_{0}|_{Freq. }\), and \(\zeta\) imply the RF power of the received signal expressed in S21, the initial value of the RF power, and the coefficient of the electromagnetic radiated power, respectively. The difference between the RX power levels from the LoS link with \(Dist\_Ref=1\) m and \(Dist\_New=1.5\) m is \(3.5\) dB according to the calculation. This is pretty much the same as the difference between the signal strengths. as the peaks of the S21 curves were observed to be \(-\)21.5 dB in Figure 6a and \(-\)25.1 dB in Figure 6g. The experiments comply with the theories, and it is possible to guess the change in the signal path length by watching the power level in this sort of measurement. The second piece of information is that though the sensing block and communication block are assembled as one planar stru1 cture, the interference to other operating frequencies is very low, at \(-\)50 dB at 28 GHz for the 24 GHz radiation and \(-\)65 dB at 24 GHz for the 28 GHz radiation. This results from the separation of the frequencies even at the mmW band and due to the generation of high-directivity beam patterns from the physically small antennas. Figure 6: _Cont._  
Figure 6: _Cont_. Figure 6: The results of testing various links between the TX and RX as the integrated module of the communication and surface-sensing antennas by observing S\({}_{21}\) as the transfer coefficient. (**a**) Sensing signal LoS of \(Dist_{LoS}=10^{3}\) mm. (**b**) Sensing signal reflection by the metal plane with \(Dist_{RoundT}=10^{3}\) mm vs. LoS. (**c**) Sensing signal reflection by RS01 as the metasurface with \(Dist_{RoundT}=10^{3}\) mm vs. reflection by the metal plane vs. LoS. (**d**) Comm. signal LoS of \(Dist_{LoS}=10^{3}\) mm. (**e**) Comm. signal reflection by the metal plane with \(Dist_{RountT}=10^{3}\) mm vs. LoS. (**f**) Comm. signal reflection by RS01 as the metasurface with \(Dist_{RoundT}=10^{3}\) mm vs. reflection by the metal plane vs. LoS. (**g**) Sensing signal LoS of \(Dist_{LoS}=1.5\times 10^{3}\) mm. (**h**) Sensing signal reflection by the metal plane with \(Dist_{RoundT}=1.5\times 10^{3}\) mm vs. LoS. (**i**) Sensing signal reflection by RS01 as the metasurface with \(Dist_{RoundT}=1.5\times 10^{3}\) mm vs. reflection by the metal plane vs. LoS. (**j**) Comm. signal LoS of \(Dist_{LoS}=1.5\times 10^{3}\) mm. (**k**) Comm. signal reflection by the metal plane with \(Dist_{RoundT}=1.5\times 10^{3}\) mm vs. LoS. (**l**) Comm. signal reflection by RS01 as the metasurface with \(Dist_{RoundT}=1.5\times 10^{3}\) mm vs. reflection by the metal plane vs. LoS.