Journal of the Japanese Society for Technology Education

Number 4
Volume 39


The Transmission Characteristics and a Design for a Chebyshev-Type Low-Pass Filter with Complex Poles

A design and the transmission characteristics for a low-pass filter which has Chebyshev-type attenuation characteristics and complex poles on the complex frequency plane is presented. When comparing to circuits of the same order, this low-pass filter is an improvement over an ordinary Wegner-type low-pass filter or a conventional Chebyshev-type low-pass filter with regard to the delay characteristics (the linear phase characteristics). In addition, it has better slope characteristics than the Wagner-type low-pass filter. The ordinary Chebyshev function used in a lumped-element circuit was developed into a new type Chebyshev function which has conjugate complex poles ( four poles ) both in the right half and in the left half of the complex frequency plane. We obtained an attenuation amount and an amplitude function for the low range filter motion. We calculated this and arrived at the design formula for the low-pass filter which fulfilled the specifications. A design based on actual specifications for this low-pass filter is provided. The circuit was realized with an active circuit using IC operational amplifiers.

Key words :low-pass filter, complex poles, delay characteristics, attenuation characteristics, IC operational amplifier, circuit synthesis