## 3 Validation Analysis, Results, and Discussion  
The characteristics and performance of the proposed antenna have been researched in this section. The design analysis process includes the various parameters analysis, the performance with simulation, and measurement results. Figure 3 demonstrates the reflection coefficient's performance with the comparison of simulation and measurement for the proposed dual-band monopole antenna. The validation result agrees with the result simulated and measured. The validation tool employed an EM simulator for simulation results and a vector network analyzer as the equipment of Agilent E7071C for measurement results. The measured impedance bandwidths are defined by 3:1 VSWR, widely used for the internal WWAN antenna design specification [26; 27; 28; 29; 30]. The antenna bandwidth defined by VSWR is 3:1 to match the CTIA specification standard with the built-in WWAN antenna design integrated RF active circuit application. Thus, under 6 dB reflection coefficient conduction, the operating frequency can reach the lower band of 2000-2742 MHz and the higher band of 4062-8000 MHz. The bandwidth of the lower band can achieve 31.22%, and the bandwidth of the upper band has an incredible bandwidth of 65.29%. Therefore, the proposed antenna with a dual-band design is suitable for multi-functional wireless communication system standards in autonomous vehicles' communication system devices. Figure 2: Surface current distribution analysis at: (**a**) 2350 MHz; (**b**) 2450 MHz; (**c**) 5080 MHz; (**d**) 5500 MHz; (**e**) 5890 MHz; (**f**) 6500 MHz; (**g**) 7150 MHz. The progressive analysis of antenna architecture characteristics is shown in Figure 4. Strip 1 has three types to analyze the return loss effect is presented in Figure 4a. The upper operating band is controlled by strip 2 when only strip 2 is without the strip 1 condition as the type 1 structure. Type 2 is with both strip layouts, which can generate the lower and upper operating band. Moreover, the end of strip 1 has been designed with progressive impedance change from narrow to wide, the performance of return loss can achieve a better impedance for the suggestion antenna design as the type 3 antenna configuration is shown in Figure 4a. Discuss that the length change of W9 has a significant influence on the high-frequency response, as shown in Figure 4b. Therefore, the length of W9 equal to 5.5 mm is the best impedance matching response. The antenna radiation performance verification uses the AMS-8100 model anechoic chamber antenna measurement system manufactured by ETS-Lindgren, as shown the Figure 5.The simulation and measurement radiation patterns are presented in Figure 6, including four operating bands with 2450, 5500, 6500, and 7500 MHz. The radiation results reach omnidirectional modes are good agreement with simulated and measured. Furthermore, the antenna gains and efficiencies are also shown in Figure 7. The results are demonstrated that both performances achieve very close with simulation and measurement. The gain can obtain about 2.7 dBi in the lower band, and the gain can get about 6.75 dBi in the upper band. Thus, the antenna efficiency can reach 91% for the lower band, and the antenna efficiency can achieve 93% for the upper band. In addition, the proposed antenna was also compared with recent literature and listed the bandwidth and dimensions, as the Table 1 The proposed antenna characteristic is shown as compact and widely operating bands. This table uses the journal papers of the past two years for antenna design comparison. The proposed antenna design has a larger bandwidth than the literature [26; 27; 28; 29; 30]. The antenna's gain also has a comparable measurement result to the literature [26; 27; 28; 29; 30]. The antenna size of the proposed antenna is smaller than in the literature [26; 27; 28; 29; 30]. The system ground size is smaller than the literature [26; 30]. The overall antenna size is smaller than in the literature [26; 28; 30].