文档介绍：Copyright © 2005. Shi Ping CUC
Chapter 7 IIR Filter Design
Content
Preliminaries
Characteristics of Prototype Analog Filters
Analog-to-Digital Filter Transformations
Frequency Transformations
Copyright © 2005. Shi Ping CUC
Preliminaries
How to design a digital filter
First: Specifications
The design of a digital filter is carried out in three steps:
Before we can design a filter, we must have some specifications. These specifications are determined by the applications.
Second: Approximations
Once the specifications are defined, we use various concepts and mathematics e up with a filter description that approximates the given set of specifications. This step is the topic of filter design.
Copyright © 2005. Shi Ping CUC
Preliminaries
Third: Implementation
The product of the above step is a filter description in the form of either a difference equation, or a system function, or an impulse response. From this description we implement the filter in hardware or software on puter.
In this and the next chapter we will discuss in detail only the second step, which is the conversion of specification into a filter description.
Copyright © 2005. Shi Ping CUC
Preliminaries
In many applications, digital filters are used to implement frequency-selective operations;
Therefore, specifications are required in the frequency-domain in terms of the desired magnitude and phase response of the filter;
Generally a linear phase response in the passband is desirable;
An FIR filter is possible to have an exact linear phase;
An IIR filter is impossible to have linear phase in passband. Hence we will consider magnitude-only specifications.
The specifications
Copyright © 2005. Shi Ping CUC
Preliminaries
There are two ways to give the magnitude specifications
Absolute specifications
Provide a set of requirements on the magnitude response function and generally used for FIR filters.
Passband
Stopband
Transition band
The ending frequency of the passband. Bandwidt