Studies On Equivalent Circuits Of Periodic Metal Rod Arrays As Transmission Lines

In the transmitting link of electromagnetic energy, wave-guiding structures are important components. These components assume the task of transmitting signals, whose performance and volume can directly affect the performance and load of the whole system. Periodic metal rod arrays not only can be used to fabricate Yagi-Uda antenna of high directivity, but also can be used as guiding structures which transmit electromagnetic waves effectively in certain frequency bands. Compared to traditional guiding structures such as metallic waveguides, periodic metal rod arrays have the advantages of light weight, small volume and capability of being embedded in a lightweight media such as styrofoam. Bend or twist of periodic metal rod arrays has relatively small effect on the transmitting performance of the arrays.The method of moment (MoM) and approximate solution obtained by Floquet theory have long been the main methods of analyzing the guiding property of periodic metal rod array. When the number of rods in the array is large, MoM will be very inefficient since it costs much storage space and long computation time. Floquet theory method can be employed to predict the guiding property of a finite array containing many rods by analyzing an infinite periodic rod array. However, it is only valid for lossless rods and requires much cumbersome computation. In view of these difficulties, this dissertation proposes to study the guiding performance of periodic metal rod array using its equivalent circuit. With equivalent circuit method, it is propitious to understand the physical process of electromagnetic wave's traveling along the array and the center frequencies of passing bands can be calculated quite fast and accurately.Although many scholars have presented various kinds of equivalent circuit models for a single dipole made of a metal rod, no equivalent circuits can describe the guiding property of periodic metal rod array well so far. According to the equivalent circuit model of a single dipole presented by predecessors, a detailed method to extract the element parameters of the equivalent circuit is given in this dissertation. The equivalent circuit of periodic metal rod array is constructed based on the equivalent circuits of dipoles and passive guiding rods and coupling capacitors. The guiding property of the equivalent circuit is quite in agreement with simulation and measured results, which validates the correctness of the equivalent circuit. This work also lays a foundation for analyzing the guiding property of large scale carbon nanotube array using equivalent circuit method by adding the unique quantum effect of carbon nanotube in the future.