plane form a loop, serve as an inductor , and are mainly controlled by changing the distance between two vias. The inner conductive layer increases the capacitance to the antenna, increasing the total capacitance . Therefore, the shifts toward to the low-frequency band. In other words, the iscontrolledbothbytheparameters and .Fig.3shows the simulated results of the input impedances of the proposed RFID tag antenna with different interlayer lengths . From the figure, we observe that the large interlayer length indeed results in lower self-resonant frequency that is achieved by increasing the capacitance of the RFID tag antenna.