Evaluation of the position of the connection point of the coaxial probe to the rectangular printed antenna

Abstract

The input impedance of the printed antenna depends on the feed connection coordinate. It is often possible to provide the required level of the voltage standing wave coefficient of a simple printed antenna by correctly selecting the connection coordinate of the feeding coaxial probe. The selection of the coordinate of the coaxial probe connection by analytical calculations is usually inconvenient due to its complexity, so often numerical calculation methods are used to optimize printed antennas, such as the method of finite differences in the time domain, the method of moments, and others. The paper deals with the problem of selecting the connection point of a feeding coaxial probe to a rectangular printed antenna using the finite difference time domain method, the cavity model method, and a combination of these two methods. It has been established that the finite differences time domain method requires large computing power, since the selection of the coordinate of the connection of the coaxial probe requires a complete solution of the electrodynamic problem for each case of feed connection. The cavity model method allows us to estimate the position of the power point almost in real time with minimal computing power, but it has much less accuracy compared to the finite difference time domain method. It is possible to reduce the number of iterations in the process of selecting the coordinate of connecting the coaxial probe using the finite difference time domain method due to its joint use with the cavity model method. In this case, the first (initial) coordinate of the coaxial probe connection is determined using the cavity model. After that, optimization algorithms are applied together with the finite difference time domain method. The paper presents the results of comparing the required number of iterations for convergence of the optimization algorithm based on the confidence domain method when using the finite difference method in the time domain and the joint use of the cavity model and the finite difference time domain when solving the problem of selecting the feeding coordinate.