DESIGN OF DIELECTRIC MULTILAYER BANDPASS-FILTERS USING ARBITRARY THICKNESS OF LAYERS

The design of dielectric multilayer bandpass filters using arbitrary t hickness of layers was investigated in order to improve the design acc uracy of conventional methods. The actual design procedure, the layer structure, necessary formula in the design, the conditions of paramete r selection, and the design examples are presented. Furthermore, 900 B utterworth and Chebyshev filters consisting of SiO2 and TiO2 layers we re designed for a center wavelength of 1.3 mu m. The applicable range of the present method, the design error distribution, and number of la yers are presented. Using these results, the present method is compare d with an earlier method that used only the fundamental thickness of l ayers. The applicable range of the present method with respect to the percentage bandwidth is within 6%, which is narrower than the 10% of t he previous method. However, the relative error of percentage bandwidt h is less than 10(-5) using the present method, which is a marked impr ovement over the 0.1-0.2 obtained using the previous method. The maxim um ripple values of the Chebyshev filters are 0.5-0.7 dB using the pre sent 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 m ethod. The number of layers does not differ much between the two metho ds. (C) 1997 Scripta Technica, Inc.