Study Of Equivalent Circuits For Coplanar Waveguides

As most of devices planar microwave integrated circuits are complex and it isdifficult to design the structure directly.While the equivalent circuit, which simulatesthe microwave planar integrated circuit propagation characteristics, can efficientlyoptimize the microwave integrated structure. Therefore it is important to design anequivalent circuit of high accuracy and good adaptability.As one of planar transmission lines, coplanar waveguide (CPW) is widely used forits low-loss and high transmission efficiency. Based on the principle of extractingequivalent circuit on static field, this thesis design the equivalent circuits of manyCPW lumped elements and verified the validity of these circuit models. Besides, thisthesis also analyzed the influence of changes main physical dimensions of CPW onthe extracted RCL values and studied the influence of main LC values on equivalentcircuit characteristic. The purpose of above is used to adjust coplanar waveguidestructure.This thesis mainly analyzes the following coplanar lumped elements: impedancetransformer, inductance connected to ground, interdigital capacitor, square spiralsnductor. Several CPW structures are designed based on the equivalent circuits ofsome coplanar lumped elements extracted from above. These structures include:parallel structure of inductance connected to ground, square spiral inductor andinterdigital capacitor series structure, resonant structure based on impedancetransformer. After verifying the validity of these structures, this thesis presentsthe corresponding adjustment process under the guidance of the principle that theequivalent circuit transmission characteristics vary with the main circuit components.Thus, relatively ideal transmission characteristics of CPW structures are achieved.The results shows that the equivalent circuit model of various coplanarwaveguide structures designed in this thesis are of good adaptability which haspractical significance in the design and adjustment of coplanar waveguide structures.