Optimal Sharpening of Compensated Comb Decimation Filters: Analysis and Design

Comb filters are a class of low-complexity filters especially useful for multistage decimation processes. However, the magnitude response of comb filters presents a droop in the passband region and low stopband attenuation, which is undesirable in many applications. In this work, it is shown that, for stringent magnitude specifications, sharpening compensated comb filters requires a lower-degree sharpening polynomial compared to sharpening comb filters without compensation, resulting in a solution with lower computational complexity. Using a simple three-addition compensator and an optimization-based derivation of sharpening polynomials, we introduce an effective low-complexity filtering scheme. Design examples are presented in order to show the performance improvement in terms of passband distortion and selectivity compared to other methods based on the traditional Kaiser-Hamming sharpening and the Chebyshev sharpening techniques recently introduced in the literature

Applications of MATLAB in Science and Engineering

The book consists of 24 chapters illustrating a wide range of areas where MATLAB tools are applied. These areas include mathematics, physics, chemistry and chemical engineering, mechanical engineering, biological (molecular biology) and medical sciences, communication and control systems, digital signal, image and video processing, system modeling and simulation. Many interesting problems have been included throughout the book, and its contents will be beneficial for students and professionals in wide areas of interest

The influence of the hysteresis comparator delay on the central frequency of an asynchronous sigma-delta modulator

U radu su opisane osnovne karakteristike sinkronog i asinkronog sigma-delta (ASD) modulatora i dan je pregled trenutnog stanja u području primjene sigma-delta (SD) modulatora. U svrhu usporedbe, opisane su osnovne razlike izmeñu sinkrone i asinkrone izvedbe SD modulatora. Provedena je analiza utjecaja vremena kašnjenja komparatora s histerezom na radne značajke ASD modulatora. Matematičkim proračunima, računalnom simulacijom i izvedenim mjerenjima na modelima pokazano je smanjenje središnje frekvencije zbog utjecaja vremena kašnjenja. Za smanjenje nepoželjnog utjecaja vremena kašnjenja na radne značajke ASD modulatora predložene su dvije metode. Prva metoda se zasniva na ograničenju izlaznog signala iz integratora, čime se ostvaruje povećanje izlazne frekvencije (metoda 1), dok se kod druge metode uvodi amplitudna modulacija napona pragova histereze koja izlazni signal integratora postavlja unutar vrijednosti proračunatih napona pragova histereze. Na temelju matematičkog modela ASD modulatora, za potrebe simulacije utjecaja vremena kašnjenja i metoda za poboljšanje (metoda 1 i metoda 2), kreiran je Simulink model u programskom alatu Matlab®. U Matlab okruženju simuliran je i sklop za pretvorbu 1- bitovnog ASD signala govornog pojasa (frekvencija do 4 kHz) u sinkroni PCM m-bitovni digitalni signal. U simulacijskom programu Multisim Analog Devices Edition simulacijski model ASD modulatora primijenjen je na pojačalo snage D klase na kojem je takoñer ispitana metoda 2. Za verifikaciju matematičkih modela mjerenjima izrañen je laboratorijski model ASD modulatora s mogućnošću primjene metode 1 i 2. Rezultatima mjerenja na laboratorijskom modelu ASD modulatora potvrñeno je poboljšanje radnih značajki ASD modulatora primjenom navedenih metoda. Na sklopu pojačala snage D klase izmjereno je ukupno harmonijsko izobličenje izlaznog signala. Dokazano je da se primjenom metode 2 faktor ukupnog harmonijskog izobličenja smanjuje u cijelom rasponu amplituda ulaznog signala.The basics properties of the synchronous and asynchronous sigma-delta (ASD) modulators have been described and current state-of-art in sigma-delta modulation applications has been reported. For comparison, the major differences between synchronous and asynchronous SD modulators have been described. Analysis of hysteresis comparator propagation delay influence to the ASD modulator performances has been provided. The mathematical analysis, computer simulations and measurement results confirm the central frequency detoriation due to propagation delay influence. For propagation delay compensation two methods have been proposed. The first method is based on limitation of the integrator output voltage (method 1), which increses ASD central frequency, while second method introduce hysteresis threshold voltage amplitude modulation which keeps the integrator output voltage within calculated hysteresis threshold levels. Based on the mathematical model of the ASD modulator, for simulation purposes of the propagation delay influence and the proposed method for propagation delay compensation (method 1 and method 2), Simulink model in Matlab® has been created. Matlab implementation of the A/D converter circuit for 1-bit ASD signal to synchronous PCM m-bit digital word for voice-band applications has also been proposed. Using Multisim Analog Devices Edition, simulation model of ASD modulator has been applied to class-D power amplifier for method 2 verification. For measurement results, the ASD modulator ciruit has been implemented with possibility for method 1 and method 2 application. The measuerment results on the ASD circuit confirm the mathematical analysis for the propagation delay influence and compensation method contributions which improve ASD modulator performances. For ASD modulator application in class-D power amplifier, total harmonic distorsion has been measured. It has been shown that method 2 implementation reduces total harmonic distorsion of output signal for full range of input signal amplitudes

Ultrasound Imaging

In this book, we present a dozen state of the art developments for ultrasound imaging, for example, hardware implementation, transducer, beamforming, signal processing, measurement of elasticity and diagnosis. The editors would like to thank all the chapter authors, who focused on the publication of this book