基于旋转永磁体的低频通信技术研究

As a new type of low-frequency magnetic antenna, the rotating permanent magnet antenna overcomes the disadvantages of large volume, high power consumption and low efficiency of traditional low-frequency coils, and is mainly applied in near-field low-frequency magnetic communication. In this paper, FEKO is used to analyze the variation law of the magnetic field in the near zone of the antenna with the direction, and the influence of the infinite ground plane on the magnetic field distribution in the near zone of the antenna in the near field range is explored. The results show that the radiation intensity of the antenna is the largest in the radial direction and the smallest in the axial direction. And within a relatively close communication distance range, the influence of the ground on the magnetic field signal is small. The relationship between the moment of inertia and the magnetic moment is analyzed, the structural parameters of the permanent magnet are optimized, two prototypes are developed, and the power consumption of the rotating permanent magnet antenna before and after optimization is tested. The experimental results show that in the case of a mass of 30 g, the optimized permanent magnet antenna has an average power consumption about 5.5 W lower than that of the antenna before optimization. Using the 2FSK modulation of the magnetic field in the direct antenna modulation mode, the symbol information is recovered by non-coherent demodulation. The test results show that in a complex electromagnetic environment, the optimized permanent magnet antenna can achieve ultra-low frequency communication with a symbol rate of 3.5 bps within a range of 20 m.

旋转永磁体天线作为一种新型低频磁天线,克服了传统低频线圈体积大、功耗高、效率低的缺点,主要应用于近场低频磁通信中。该文利用FEKO分析了天线近区磁场随方向的变化规律,探究了近场范围内无限大地面对天线近区磁场分布的影响,结果表明:天线在其径向辐射强度最大,在其轴向辐射强度最小。并且在较近的通信距离范围内,地面对磁场信号的影响较小。分析了转动惯量和磁矩之间的关系,对永磁体结构参数进行了优化,研制了两款样机,并对优化前后的旋转永磁体天线功耗进行测试,实验结果表明:在质量大30 g的情况下,优化后的永磁体天线比优化前的天线平均功耗低5.5 W左右。利用直接天线调制方式磁场的2FSK调制,通过非相干解调恢复码元信息,测试结果表明:复杂电磁环境下,优化后的永磁体天线可以在20 m范围内实现码元速率为3.5 bps的超低频通信。