一种基于缝隙天线阻抗的带缝腔体谐振频率计算方法

电磁波经缝隙进入机箱腔体后，会在某些频率点形成驻波而发生电磁谐振，导致腔体屏蔽效能急剧下降.为快速准确预测谐振频率以指导屏蔽腔体设计，本文基于缝隙天线阻抗理论提出一种带缝腔体谐振频率的计算方法.将电磁场用自由空间和腔体格林函数表示，根据缝隙处的边界条件建立等效磁流源的积分方程.通过矩量法求解积分方程，计算出腔体输入阻抗.根据谐振发生时电抗为零或电阻最小，可从频率-阻抗曲线获得谐振频率.本文方法不仅能预测缝隙谐振和低阶模式腔体谐振，还能预测出高阶谐振.与实验和CST仿真结果对比验证了本文方法的准确性及快速性.最后用本文方法分析了腔体和缝隙尺寸以及缝隙位置对谐振频率的影响.

A Method for Resonant Frequencies Calculation Based on the Impedance of Cavity-Backed Slot Antenna

An efficient and accurate technique based on the impedance theory of cavity-backed slot antenna is introduced to calculate the resonant frequencies of a rectangular enclosure with a slot on its wall.Expressing electromagnetic fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure,an integral equation for equivalent magnetic current is obtained by enforcing the boundary condition across the slot.The Method of Moments is used to solve the integral equation for the input impedance.We can get resonant frequencies from the zero reactance or the minimum resistance on the frequency-impedance curves.Our method is verified successfully by experimental results and CST.The effects of the cavity size,of the slot length,and of the slot offset on the resonant frequency are discussed.