Contents i度 8 DESIGN OF DIGITAL FILTERS 614 8.1 General Considerations 614 8.1.1 Causality and Its Implications.615 8.1.2 Characteristics of Practical Frequency-Selective Filters.619 8.2 Design of FIR Filters 620 8.2.1 Symmetric and Antisymmetric FIR Filters.620 8.2.2 Design of Linear-Phase FIR Filters Using Windows.623 8.2.3 Design of Linear-Phase FIR Filters by the Frequency-Sampling Method.630 8.2.4 Design of Optimum Equiripple Linear-Phase FIR Filters.637 8.2.5 Design of FIR Differentiators,652 8.2.6 Design of Hilbert Transformers.657 8.2.7 Comparison of Design Methods for Linear-Phase FIR Filters.662 8.3 Design of IIR Filters From Analog Filters 666 8.3.1 IIR Filter Design by Approximation of Derivatives.667 8.3.2 IIR Filter Design by Impulse Invariance.671 8.3.3 IIR Filter Design by the Bilinear Transformation.676 8.3.4 The Matched-Transformation.681 8.3.5 Characteristics of Commonly Used Analog Filters.681 8.3.6 Some Examples of Digital Filter Designs Based on the Bilinear Transformation.692 8.4 Frequency Transformations 692 8.4.1 Frequency Transformations in the Analog Domain.693 8.4.2 Frequency Transformations in the Digital Domain.698 8.5 Design of Digital Filters Based on Least-Squares Method 701 8.5.1 Pade Approximation Method.701 8.5.2 Least-Squares Design Methods.706 8.5.3 FIR Least-Squares Inverse (Wiener)Filters,711 8.5.4 Design of IIR Filters in the Frequency Domain.719 8.6 Summary and References 724 Problems 726 9 SAMPLING AND RECONSTRUCTION OF SIGNALS 738 9.1 Sampling of Bandpass Signals 738 9.11 Representation of Bandpass Signals.738 9.1.2 Sampling of Bandpass Signals,742 9.1.3 Discrete-Time Processing of Continuous-Time Signals,746 9.2 Analog-to-Digital Conversion 748 9.2.1 Sample-and-Hold.748 92.2 Quantization and Coding.750 9.2.3 Analysis of Quantization Errors,753 9.2.4 Oversampling A/D Converters,756