Application Note 27A
June 1988
A Simple Method of Designing Multiple Order All Pole
Bandpass Filters by Cascading 2nd Order Sections
Nello Sevastopoulos
Richard Markell
INTRODUCTION DESIGNING BANDPASS FILTERS Filter design, be it active, passive, or switched capacitor,
is traditionally a mathematically intensive pursuit. There
are many architectures and design methods to choose
from. Two methods of high order bandpass filter design
are discussed herein. These methods allow the filter
designer to simplify the mathematical design process
and allow LTC’s switched capacitor filters (LTC®1059,
LTC1060, LTC1061,LTC1064) to be utilized as high quality
bandpass filters. Table 1 was developed to enable anyone to design Butterworth bandpass filters. We will discuss the tables in
more detail later in this paper, but let’s first design a filter. AN27A is the first of a series of application notes from
LTC concerning our universal filter family. Additional notes
in the series will discuss notch, lowpass and highpass
filters implemented with the universal switched capacitor
filter. An addition to this note will extend the treatment of
bandpass filters to the elliptic or Cauer forms.
This note will first present a finished design example and
proceed to present the design methodology, which relies on …