# Design and Experiment of Magnetic Antenna Vibration and Noise Reduction System
## 3 Analysis and Design of Damping System
### Identification of Mechanical Characteristic Parameters of Silicone Rubber Elastic Elements  
In order to prevent the magnetic field in the space near the antenna of the designed damping system from changing caused by vibration, non-magnetic materials must be selected to design the antenna damping system, including elastic elements and corresponding transition structures. In order to make sure the stiffness of the damping system is low enough in a limited space, it is necessary to take a silicone rubber strip with small cross-sectional size and relatively small hardness as an elastic element. Considering that rubber and non-metal antennas and mounting bases cannot be vulcanized and fixed, if the pressure is used to make the connection fixed, when the pressure is excessive, the local stress would be too large to cause defects. When the pressure is too small, due to the creep of the rubber material, the fixed points of the damping system would be slack and unstable after operating for a long time. Therefore, in this paper, the silicone rubber strip is designed into a loop, and the two ends are respectively suspended on the antenna and the suspension rod of the mounting base, it can keep balance naturally under the effect of gravity, without excessive pressing force for fastening. When this scheme is adopted to design a silicone rubber strip, the following factors must be taken into consideration:  
1. The silicone rubber strip must have sufficient load-bearing capacity. In other words, the tensile stress cannot be too large, which means that the cross-sectional size of the silicone rubber strip cannot be too small;
2. There is a nonlinear relationship between the deformation of the silicone rubber strip and the stress it is subjected to. Knowing that the antenna and the mounting base satisfy minimum spacing constraint in the static equilibrium state, the stress-strain relationship is required to reverse the initial free length and section size of the silicone rubber strip;
3. The static stiffness and dynamic stiffness of the silicone rubber strip are quite different, while the damping performance depends on its dynamic stiffness. Therefore,  
Figure 3: The matching curve of radial composite stiffness-damping rate of the vibration damping system. the precise design of the vibration damping performance needs to be based on the relationship between its dynamic stiffness and stress. Based on the above analysis, in order to make the antenna damping system using a silicone rubber strip meet the space layout constraints and the damping performance indicators, it is necessary to accurately obtain the static and dynamic mechanical properties of the selected silicone rubber strip material. For this reason, first, for the silicon rubber strip material to be used, a sample of a certain length and cross-sectional size is selected, and its static stress-strain relationship is obtained through a static loading test. Then, a number of the sample suspension masses are used to test the vibration isolation natural frequency to obtain the dynamic stiffness characteristics of the silicone rubber strip samples under different loads. Further, data processing is used to obtain material dynamic mechanical characteristic parameters that are not related to geometric dimensions, which is called dynamic Young's modulus-stress characteristic curve, providing a basis for the subsequent new-size silicone rubber driving stiffness estimation and antenna vibration damping performance evaluation. We chose a sample of a rectangular cross-section silicone rubber strip with a Shore hardness of 40 HA, a density of \(\rho=1.1\times 10^{3}\) kg/m\({}^{3}\), and the cross-sectional area in the free state was \(s_{0}=1.05\times 10^{-4}\) m\({}^{2}\). We took four pieces of the aforementioned silicone rubber strip samples of a certain length. One end of each sample was fixed on the same rigid base, and the other end was fixed to the four corners of the rectangular plate-shaped metal load, respectively.