说明：  本函数在matlab实现阻抗圆图，通过调用switch（）函数，可以得出传输线的反射系数，以及支节匹配等参数，本函数可以实现单、双和三支节匹配。
(The realization of the impedance function in matlab circle map, by calling the switch () function of transmission line can be drawn of the reflection coefficient, as well as the support section to match the parameters, this function can achieve a single, double and three matching section.)