Transmission characteristics of a triple tuned coupled band-pass filter and their dependences on terminating resistances

In this paper, we present the relationship between the transmission function and the, terminating resistances of a triple tuned coupled band-pass filter. It is possible to estimate the change of the transmission function by changing only the terminating resistances continuously while keeping the other equivalent circuit parameters fixed. The following results were obtained. When terminating resistances are changed continuously over a wide range, the well-known equal ripple, maximally flat and flat delay characteristics appear dispersedly. There is a combination of parameters which shows the group delay resembling a Gaussian distribution. The group delay at the center frequency becomes minimum when the filter function exhibits the maximally flat in attenuation. It is convenient that the terminating resistances can be changed continuously as an independent variable, because it enables some evaluation criteria to be satisfied.