智能反射面阵元互耦与共存干扰研究

Research on IRS’s Elemental Coupling and Induced Co-site Interference

智能反射面(Intelligent Reflecting Surface,IRS)是由大量无源反射元件呈阵列排列构成的智能超表面,其阵元间距是相位控制的关键技术参数,在小于半波长时存在不可忽略的互耦效应。本文针对多网运营的应用环境,考虑IRS反射阵元之间存在相互耦合的情况,研究系统间共存干扰与阵元间距、工作频段、物理位置的关联关系。针对发射机、接收机和IRS之间自阻抗和互阻抗的建模需求,将互耦效应进行量化转换,以阻抗的形式将其数据化,结合阵元反射增益和相位参数的作用因素,建立了远场条件下基于阻抗电路的共存干扰传播模型。针对IRS接收,由发射天线电流与IRS互阻抗的乘积得到再辐射矩阵;针对IRS反射,由IRS负载电流与接收天线互阻抗的乘积得到接收端负载电压。应用阵元等效阻抗法,通过等效阻抗的可重构性,最大化有用信号的接收功率,推导得到信干比(Signal to Interference Ratio,SIR)的计算表达式。进一步分析了共存系统的工作频段、IRS反射单元间隔、IRS的反射阵元数量、IRS与非目标收发机之间距离等因素对共存干扰产生的影响。数值仿真表明互耦偏差随阵元间距减小而增大,半波长的偏差为28%;不同载频系统的SIR表明,共存干扰的互耦效应显著且不可忽略,高频系统对低频系统产生的共存干扰对信号传输质量影响更为显著。

An intelligent reflecting surface is an intelligent surface composed of numerous passive reflecting elements arranged in an array.Mutual coupling of less than half of the carrier wavelength is a nonnegligible factor in phase controlling due to the element spacing of IRS.Focusing on the application environment of multi-network operations and considering the mutual coupling between IRS reflecting elements,this study explored the correlations between the co-site interference and the distance of elements,working frequency band,and physical location.To model the self-impedance and mutual-impedance between the transmitter,receiver,and IRS,the mutual coupling was quantified into data in the form of impedance.The co-site interference propagation model based on an impedance circuit under far field conditions was established by combining the factors of the reflection gain and phase parameter of the element.For IRS reception,the reradiation matrix was obtained by multiplying the transmitting antenna current and the IRS mutual-impedance.For IRS reflection,the load voltage of the receiver was obtained by multiplying the IRS load current and the mutual-impedance of the receiving antenna.The element equivalent impedance method was used to maximize the power of the desired signal through the reconfigurability of the equivalent impedance,and the computational expression of signal to interference ratio was given.The influence of the carrier frequency band,distance between elements,number of reflecting units,and distance between the IRS and non-target transceiver on the co-site interference were further analyzed.A numerical simulation shows that the deviation caused by mutual coupling increases with a decrease in the distance of IRS reflecting elements,and the value at the half of the carrier wavelength is 28%.It is also shown by SIR among different carrier systems that the mutual coupling contribution to co-site interference is significant and non-negligible.The co-site interference of the high-frequency system to the low-frequency system has a more significant impact on signal transmission quality.