海中低频水平磁偶极子在空气中产生的电磁场

Electromagnetic Field in Air Produced by Low Frequency Horizontal Magnetic Dipole Submerged in Sea

采用电磁波进行跨海水-空气界面通讯时,合理的天线形式是影响通信性能的重要因素之一。为了研究环形天线在跨海水-空气界面通讯中的特点,根据磁偶极子性能,考虑海底-海水-空气三层各向同性的分层模型,推导出置于海水中的水平磁偶极子空气中激发的电磁场分量的解析表达式。进一步采用数值方法,计算了顶层空气中电磁场的分布和传播规律。结果表明,海水中的低频水平磁偶极子在空气中激发的电磁场的各个分量在垂直面内有不同的方向性,且在距发射源较近时有快速的衰减,随着距离增大,衰减逐渐减缓,但在一定高度和水平范围内有可测量的量级,说明环形天线在此类型通讯中是可行的。

Referring to the communication between seawater and air by using electromagnetic wave, reasonable antenna form plays an important role in communication performance. In order to figure out the feature of loop antenna in undersea - to - air communication, the electromagnetic fields in air due to a horizontal magnetic dipole submerged in the sea layer were derived. The Analytical expressions were obtained with the model of a three - layered conduc- ting medium. Furthermore, the integral results in air were numerically calculated to present the propagation curves and the distribution patterns of the electromagnetic fields which are different from each other in vertical plane. The results in air show the rapid attenuation near the dipole and the gradually slow attenuation with greater distance. How- ever, the magnitudes of the electromagnetic fields in air are measurable for some altitude and distance. It is conclu- ded that loop antenna is feasible in undersea - to - air communication.