# Broadband Flexible Microstrip Antenna Array with Conformal Load-Bearing Structure
## 4 Analysis of Simulation and Measurement Results
### Mechanical Properties  
In order to validate the mechanical properties of the designed antenna, three-point bending and the mechanical experiment approach were employed in the following structure, including the single-layer honeycomb sandwich panel and double-layer honeycomb sandwich panel, respectively. Meanwhile, the quasi-static compression of the proposed antenna array structure has been simulated and measured. In the experiment, in order to avoid the concentration of stress, the multilayer structure composed of the substrate and the honeycomb is adhered by glue.  
Figure 18 is the three-point bending experiment and simulation of the structure with a single honeycomb core layer. According to the three-point bending deformation of the single-layer honeycomb sandwich panel in Figure 18a,b, it can be found that the honeycomb core layer and substate layers have obvious deformation, and the upper and lower substrates and honeycomb core layer are not unglued. Figure 18c shows the force-displacement curve during the three-point bending of the single-layer honeycomb sandwich panel. During the bending process, there is a sudden drop in the acting force at approximately 1.3 mm, and then it becomes smooth. The force acting in bending 1.3 mm is approximately 140 N. Moreover, the three-point bending test of the double-layer honeycomb sandwich panel is shown in Figure 19. Based on the deformation of Figure 19a,b, it can be noted that both honeycomb core layers and substrate layers are in line with obvious deformation, and the middle substrate layer shows a debonding phenomenon with the lower honeycomb core layer. In addition, Figure 19c details that the force of bending displacement of 1 mm is 263 N. Comparison of the results with a single-layer honeycomb sandwich panel confirms that the proposed antenna array structure is better for load bearing and bending resistance. Furthermore, the quasi-static compression test of the proposed antenna structure has been shown in Figure 20. Observed from Figure 20a, the deformation of the double-layer honeycomb panel is mainly the deformation of the honeycomb core layer. Moreover, the honeycomb deformation of the upper layer is more obvious than that of the lower layer. Figure 20c indicates that the maximum pressure that the structure can bear in the elastic deformation stage is approximately 1800 N.  
Figure 17: Simulated and measured results for gain radiation patterns and cross-polarization radiation patterns of the proposed antenna array in flat state and under various bending states at 12.5 GHz(**a**–**h**) E-plane and H-plane with various states.  
Figure 19: The three-point bending test of double-layer honeycomb sandwich panel, (**a**) simulation model (**b**) experiment environment, and (**c**) load–deflection relationships.  
Figure 20: The quasi-static compression test of double-layer honeycomb sandwich panel, (**a**) simulation model (**b**) experiment environment, and (**c**) load–deflection relationships.  
In general, the simulated and measured results of the proposed antenna element and antenna array are in great agreement with each other. At the same time, the validity of the equivalent model has also been verified in measured results. The electrical performance of the antenna element and antenna array are stable whether in flat state or in deformation. Owing to the loading of physical deformation molds, the accuracy of simulation, and the measurement environment, slight deviations occur. Compared with the similar antennas in Table 4, the proposed antenna array fulfills wider bandwidth and a lower SLL than others. It can be applied in the complicated and composite platform with potential due to its simplicity in structure, light weight, and integration with functions.