4.1. Introduction – Digital Filters Design for Signal and Image Processing

4.1. Introduction

The synthesis of digital filters has benefited from research done with continuous-time filters. So, to make this text comprehensive, in this chapter we will start with a brief summary of continuous-filter synthesis, which is carried out using analog components such as resistances, inductances, condensers and even active components.

In this chapter, the main methods to design continuous-time filters are introduced and the different families of filters that have been developed are presented. We will first discuss Butterworth, Cauer and Chebyshev filters (these last of types I and II). The frequency responses of Type I (resp. Type II) Chebyshev low-pass filters exhibit ripple in the passband (resp. in the stopband). We also will discuss Bessel-Thomson and Papoulis filters.

The main points covered in this chapter will be taken up again in Chapter 6, which presents information on infinite impulse response digital filters.