Practical Evaluation Method for Large IRS: RCS Pattern Synthesis of Sub-IRS with Mutual Coupling

Intelligent reflecting surfaces (IRSs) have recently been attracting attention as solutions for coverage hole problems in mobile communication areas. To utilize the IRS for mobile networks, the reflecting signal strength of IRS is evaluated in advance to estimate the improvement of coverage and interference with other wireless systems. In order to evaluate an actual IRS precisely, the reflecting phase and amplitude should be evaluated considering the mutual coupling effect. In addition, a large measurement system is required to satisfy the far-field conditions of IRS. This makes the evaluation of large IRS difficult. To solve this problem, we propose a practical evaluation method of a large IRS by synthesizing RCS patterns of small IRSs (sub-IRS). To verify the validity, we also formulate mutual coupling effects on the IRS. Through numerical evaluation, the influence of mutual coupling between each sub-IRS is reduced by increasing the size of the sub-IRS. In addition, through evaluation with the electromagnetic simulator, the RCS pattern of the proposed method reproduced that of a large IRS.