## 3 Simulation and Experiment
### Measurement and Analysis of Matrix-Type Coding Metasurface  
To further verify the theoretical assumptions and numerical simulation, as shown in Figure 7a,b, two MS samples of coding \(a\) and \(b\) were fabricated and measured. The area of MS is 300 \(\times\) 300 mm\({}^{2}\), and the thickness of overall design is 3.57 mm. Each sample consists of 6 \(\times\) 6 supercells and each supercell consists of 5 \(\times\) 5 basic units of \"0\" or \"1\". As shown in Figure 7c, the two samples were measured in the EM anechoic chamber, the transmitting and receiving horns were fixed on the same height level in front of the foam tower. The horn antenna connected to Agilent Technologies N5244A Vector Analyzer was used to measure the RCS of samples. Firstly, the empty darkroom was calibrated before measuring the MS sample. Secondly, the metal ball was placed on the foam tower for calibration as a reference. Thirdly, the MS sample and metal plate were placed on the foam tower for testing to get the RCS value. In measurement, the area of the MS sample was the same as the metal plate. Finally, the RCS reduction of MS sample plate could be obtained by comparing the RCS value of the MS with the metal plate.  
The reflectance of simulation and experiment at \(x\)- and \(y\)-polarized wave incidence are shown in Figure 8a,b. The simulated results are slightly different from the measured ones, which is mainly due to the error occurring in preparation, such as the flatness and the thickness of samples. On the whole, the simulated and measured curves of coding \(a\) and \(b\) are cons  
Figure 6: 2D scattering patterns of the coding \(a\) and metal plate in the _xoz_-plane at: (**a**) 5 GHz; (**b**) 8 GHz; (**c**) 9.5 GHz; (**d**) 10 GHz; (**e**) 13 GHz; and (**f**) 16 GHz.  
Figure 7: The matrix-type random coding MS templates: (**a**) coding \(a\); (**b**) coding \(b\); and (**c**) the measurement setup at microwave anechoic chamber.  
frequency range of 2-18 GHz, which reveals the polarization-insensitivity of matrix-type random coding MS. The reflectance of coding \(a\) and \(b\) are less than \(-10\) dB on average in the frequency range of 5.8-15.5 GHz under normal incidence, which presents an excellent broadband RCS reduction characteristic compared with other works [6; 7; 8].  
Figure 9a,b shows the RCS reduction of the MS samples under oblique incidence. The RCS reduction is greater than 10 dB in the frequency range of 5.5-15 GHz under normal incidence. For a small oblique incidence of \(10^{\circ}\), the average magnitude of RCS reduction is basically consistent with the one of \(0^{\circ}\). With the incident angle increasing to \(20^{\circ}\) and \(30^{\circ}\), the RCS reduction effect is suppressed obviously. However, it still presents a more than 5 dB of RCS reduction in a broadband frequency range. A comparison of performance (Table 1) shows that our design has a superior performance in bandwidth and magnitude of RCS reductions compared with the previous reported works [22; 33; 41; 42]. In other words, a considerable RCS reduction of matrix-type random coding MS can be achieved in oblique incident case, which further verifies the excellent RCS reduction characteristic within a wide range of incident angles compared with previous works [17; 18].  
\begin{table}
\begin{tabular}{c c c c} \hline
**Ref.** & **O. BW. (GHz)** & **R. BW. (\%)** & **RCS R. (dB)** \\ \hline
[33] & 3.1–3.4 & 9.2 & 10 \\
[41] & 6–18 & 100 & 5 \\
[42] & 9.9–19.4 & 64.8 & 10 \\
[22] & 17–42 & 84.7 & 10 \\ This work & 5.5–15 & 92.7 & 10 \\ \hline \end{tabular}
\end{table}
Table 1: Comparison of the designed metasurface with similar works presented in the literature.  
Figure 8: The simulated and measured reflectances of the MS samples at \(x\)- and \(y\)-polarized wave incidence: (**a**) coding \(a\); and (**b**) coding \(b\).  
Figure 9: Measured RCS reduction of samples under normal incidence and oblique incidence of \(10^{\circ}\), \(20^{\circ}\), and \(30^{\circ}\): (**a**) coding \(a\); and (**b**) coding \(b\).