Patent ID: 7941476

Claim:
A method of designing a passive RC complex filter, comprising the steps of: designing a lowpass transfer function F(p) for a prototype lowpass filter having poles on a circumference of a unit circle in a complex plane, the lowpass transfer function F(p) corresponding to a real coefficient rational function of second-order or higher related to a complex variable “p”; deriving a complex transfer function G(s) whose numerator is a complex coefficient and denominator is a real coefficient, and which corresponds to the same-order rational function as the lowpass transfer function F(p) and has poles different from each other on a negative real axis and a zero point on an imaginary axis on the complex plane, by performing a transformation of a variable of p=j(s−j)/(s+j) related to a complex variable “s” with respect to the lowpass transfer function F(p) for the prototype lowpass filter; and configuring the passive RC complex filter to include a plurality of filter elements by calculating a complex transfer function H(s) of the same order as the transfer function F(p) and configuring the filter elements with respective elements values such that the filter elements correspond to an equal arrangement of coefficients of the complex transfer function G(s) and the complex transfer function H(s) in the passive RC complex filter.