# Design and Experiment of Magnetic Antenna Vibration and Noise Reduction System
## 1 Introduction  
In recent years, with the development of deep-sea exploration technology, the influence of the ocean on electromagnetic waves has become the focus of attention for many researchers [1]. The low-frequency electromagnetic wave has the advantages of low attenuation and strong anti-interference ability in seawater [2], as a reliable means of underwater electromagnetic signal detection. Compared with traditional underwater detection methods, magnetic antenna has many advantages in detection depth, direction, size and use mode, making it gradually become the main means of deep-sea detection. A magnetic antenna is essentially a device for receiving electromagnetic waves in space; by winding two separate coils around a magnetic bar, it can receive electromagnetic signals of femto-tesla level. However, once the weak vibration in the environment is transmitted to the antenna, it will cause the antenna to cut the geomagnetic field movement, resulting in electromagnetic induction noise, and then affect the performance of the magnetic antenna. For example, when an underwater vehicle's engine is working or encounters the impact ofocean current, the magnetic antenna will produce large electromagnetic noise. Therefore, the suppression of this kind of motion induced noise becomes the key to the design and application of magnetic antenna. In order to study the source of motion-induced noise and find the methods to suppress motion-induced noise, researchers have carried out a lot of research and experiments. In 1971, [PERSON] (1971) analyzed the vibration characteristics and noise of flexible ring antenna and pointed out that under the action of random fluctuating stress of seawater, the transverse vibration, longitudinal vibration and torsional vibration generated by magnetic antenna directly related to the performance of magnetic antenna by cutting the geomagnetic field and producing electromagnetic induction noise. Three years later, [PERSON] (1971, 1972) proved that transverse vibration is the main cause of electromagnetic induction noise in antenna background noise by analyzing the motion-induced noise of magnetic antenna. [PERSON] et al. (2016) studied the motion-induced noise and magnetostrictive noise of underwater antenna, analyzed the generation mechanism and calculation method of the motion-induced noise of antenna by electrodes, established the calculation formula of random pulsating pressure spectrum density of fluid, and obtained the estimation formula of electromagnetic noise of magnetic antenna. [PERSON] et al. (2017) investigated vibration-induced noise in extremely low frequency magnetic receiving antennas. The results show that the received useful signal would be easily lost within the antenna noise due to vibration of the antenna. Once proper vibration reduction technology is adopted, the antenna electromagnetic noise caused by vibration can been alleviated effectively. Many studies have reported the improvement of vibration isolation performance (2016, 2017, 2018, 2019). Quasi-zero stiffness techniques by using nonlinear X-shape structures (2018), cam-roller-spring mechanisms (2019), and bio-inspired structures (2019, 2020) were proposed to acquire ultra-low vibration transmissibility in various applications. Despite the wide applications, most of them achieve quasi-zero stiffness by contacting-form structures, and suffer from friction, backlash, and space consuming. Magnetic negative stiffness mechanisms were proposed to counteract the positive stiffness so as to obtain quasi-zero stiffness without disturbances such as friction and backlash (2019, 2020). However, they introduce significant magnetic disturbance which will deteriorate the performance of the magnetic antenna. A vibration isolation system with ultra-low vibration transmissibility and zero magnetic disturbance is urgently required in the application of magnetic antenna.