Numerical analysis and simulation optimization design of coplanar waveguide in electro-optic sampling system

Coplanar waveguide is one of the key devices in the electro-optic sampling system, which directly affects the signal modulation effect of the system. In this paper, the LiTaO3 coplanar waveguide (characteristic impedance is 50Ω) is numerically analyzed and simulated. Firstly, the effective permittivity and characteristic impedance of coplanar waveguide are calculated by the elliptic integral method of conformal transformation. The relationship between the characteristic impedance and the structural parameters (dielectric thickness, central electrode width and dielectric bottom plate width) can be obtained by numerical analysis. Secondly, using the electromagnetic simulation software to simulate the electromagnetic characteristics of the designed coplanar waveguide, the results could be seen as the guidance to acquire the optimal structural design parameters. Accordingly, the essential parameters of designed LiTaO3 coplanar waveguide characteristic impedance, can meet the design requirements of the electro-optic sampling system, for transmission parameters and attenuation parameters.