Design of dielectric multilayer bandpass filters using arbitrary thickness of layers

Abstract

The design of dielectric multilayer bandpass filters using arbitrary thickness of layers was investigated in order to improve the design accuracy of conventional methods. The actual design procedure, the layer structure, necessary formula in the design, the conditions of parameter selection, and the design examples are presented. Furthermore, 900 Butterworth and Chebyshev filters consisting of SiO2 and TiO2 layers were designed for a center wavelength of 1.3 μm. The applicable range of the present method, the design error distribution, and number of layers are presented. Using these results, the present method is compared with an earlier method that used only the fundamental thickness of layers. The applicable range of the present method with respect to the percentage bandwidth is within 6%, which is narrower than the 10% of the previous method. However. the relative error of percentage bandwidth is less than 10−5 using the present method, which is a marked improvement over the 0.1–0.2 obtained using the previous method. The maximum ripple values of the Chebyshev filters are 0.5–0.7 dB using the present method when the objective ripple value is 0.5 dB, which is also a marked improvement over the 0.15–2.0 dB obtained using the previous method. The number of layers does not differ much between the two methods. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 2, 80(1): 46–58, 1997