Butterworth filter

About: Butterworth filter is a research topic. Over the lifetime, 6187 publications have been published within this topic receiving 69070 citations.

A new class of two-channel biorthogonal filter banks and wavelet bases

Abstract: Proposes a novel framework for a new class of two-channel biorthogonal filter banks. The framework covers two useful subclasses: i) causal stable IIR filter banks. ii) linear phase FIR filter banks. There exists a very efficient structurally perfect reconstruction implementation for such a class. Filter banks of high frequency selectivity can be achieved by using the proposed framework with low complexity. The properties of such a class are discussed in detail. The design of the analysis/synthesis systems reduces to the design of a single transfer function. Very simple design methods are given both for FIR and IIR cases. Zeros of arbitrary multiplicity at aliasing frequency can be easily imposed, for the purpose of generating wavelets with regularity property. In the IIR case, two new classes of IIR maximally flat filters different from Butterworth filters are introduced. The filter coefficients are given in closed form. The wavelet bases corresponding to the biorthogonal systems are generated. the authors also provide a novel mapping of the proposed 1-D framework into 2-D. The mapping preserves the following: i) perfect reconstruction; ii) stability in the IIR case; iii) linear phase in the FIR case; iv) zeros at aliasing frequency; v) frequency characteristic of the filters. >

Polyphase quadrature filters--A new subband coding technique

Abstract: A new method of implementing filter banks for subband coding of speech is presented. First, Esteban's Quadrature Mirror Filter principle is extended to allow the direct synthesis of filter banks with any number of equal size filter bands. Then, by combining the quadrature filter characteristic with the polyphase network implementation of filter banks, a new filter bank structure is obtained which requires 35% fewer computations than existing designs. In this paper the theory of operation of the Polyphase Quadrature Filter is presented and techniques for its efficient implementation are described. Then, examples of filter banks using this approach are shown and compared with other designs, and a simulation of a 16 Kbits/s coder using these filters is presented.

Analog filter design

Abstract: 1. Introduction 2. Resistor Op-Amp Circuits 3. Bilinear Transfer Functions and Frequency Response 4. Cascade Design with First-Order Circuits 5. The Biquad Circuit 6. Butterworth Low-Pass Filters 7. Butterworth Band-Pass Filters 8. The Chebyshev Response 9. Sensitivity 10. Delay Filters 11. Frequency Transformation 12. Highpass and Band-Elimination Filters 13. Inverse Chebyshev and Cauer Filters 14. Prototype and Frequency-Transformed Ladders 15. Ladder Design with Simulated Elements 16. Leapfrog Simulation of Ladders 17. Switched Capacitor Filters 18. Delay Equalization 19. Op-Amp Oscillators 20. Better Op-Amp Models APPENDIX: SCALING REFERENCES

Application of filter sharpening to cascaded integrator-comb decimation filters

Abstract: A new architecture for the implementation of high-order decimation filters is described. It combines the cascaded integrator-comb (CIC) multirate filter structure with filter sharpening techniques to improve the filter's passband response. This allows the first-stage CIC decimation filter to be followed by a fixed-coefficient second-stage filter, rather than a programmable filter, thereby achieving a significant hardware reduction over existing approaches. Furthermore, the use of fixed-coefficient filters in place of programmable-coefficient filters improves the overall throughput rate. The resulting architecture is well suited for single-chip VLSI implementation with very high data-sample rates. We discuss an example with specifications suitable for use in a wideband satellite communication subband tuner system and for signal analysis.

New microstrip "Wiggly-Line" filters with spurious passband suppression

Abstract: In this paper, we present a new parallel-coupled-line microstrip bandpass filter with suppressed spurious passband. Using a continuous perturbation of the width of the coupled lines following a sinusoidal law, the wave impedance is modulated so that the harmonic passband of the filter is rejected while the desired passband response is maintained virtually unaltered. This strip-width perturbation does not require the filter parameters to be recalculated and, this way, the classical design methodology for coupled-line microstrip filters can still be used. At the same time, the fabrication of the resulting filter layout does not involve more difficulties than those for typical coupled-line microstrip filters. To test this novel technique, 3rd-order Butterworth bandpass filters have been designed at 2.5 GHz, with a 10% fractional bandwidth and different values of the perturbation amplitude. It is shown that for a 47.5 % sinusoidal variation of the nominal strip width, a harmonic rejection of more than 40 dB is achieved in measurement while the passband at 2.5 GHz is almost unaltered.