Digital Filters

The new technology advances provide that a great number of system signals can be easily measured with a low cost. The main problem is that usually only a fraction of the signal is useful for different purposes, for example maintenance, DVD-recorders, computers, electric/electronic circuits, econometric, optimization, etc. Digital filters are the most versatile, practical and effective methods for extracting the information necessary from the signal. They can be dynamic, so they can be automatically or manually adjusted to the external and internal conditions. Presented in this book are the most advanced digital filters including different case studies and the most relevant literature

Digital Filter Design Using Improved Teaching-Learning-Based Optimization

Digital filters are an important part of digital signal processing systems. Digital filters are divided into finite impulse response (FIR) digital filters and infinite impulse response (IIR) digital filters according to the length of their impulse responses. An FIR digital filter is easier to implement than an IIR digital filter because of its linear phase and stability properties. In terms of the stability of an IIR digital filter, the poles generated in the denominator are subject to stability constraints. In addition, a digital filter can be categorized as one-dimensional or multi-dimensional digital filters according to the dimensions of the signal to be processed. However, for the design of IIR digital filters, traditional design methods have the disadvantages of easy to fall into a local optimum and slow convergence. The Teaching-Learning-Based optimization (TLBO) algorithm has been proven beneficial in a wide range of engineering applications. To this end, this dissertation focusses on using TLBO and its improved algorithms to design five types of digital filters, which include linear phase FIR digital filters, multiobjective general FIR digital filters, multiobjective IIR digital filters, two-dimensional (2-D) linear phase FIR digital filters, and 2-D nonlinear phase FIR digital filters. Among them, linear phase FIR digital filters, 2-D linear phase FIR digital filters, and 2-D nonlinear phase FIR digital filters use single-objective type of TLBO algorithms to optimize; multiobjective general FIR digital filters use multiobjective non-dominated TLBO (MOTLBO) algorithm to optimize; and multiobjective IIR digital filters use MOTLBO with Euclidean distance to optimize. The design results of the five types of filter designs are compared to those obtained by other state-of-the-art design methods. In this dissertation, two major improvements are proposed to enhance the performance of the standard TLBO algorithm. The first improvement is to apply a gradient-based learning to replace the TLBO learner phase to reduce approximation error(s) and CPU time without sacrificing design accuracy for linear phase FIR digital filter design. The second improvement is to incorporate Manhattan distance to simplify the procedure of the multiobjective non-dominated TLBO (MOTLBO) algorithm for general FIR digital filter design. The design results obtained by the two improvements have demonstrated their efficiency and effectiveness

Wavelet Theory

The wavelet is a powerful mathematical tool that plays an important role in science and technology. This book looks at some of the most creative and popular applications of wavelets including biomedical signal processing, image processing, communication signal processing, Internet of Things (IoT), acoustical signal processing, financial market data analysis, energy and power management, and COVID-19 pandemic measurements and calculations. The editor’s personal interest is the application of wavelet transform to identify time domain changes on signals and corresponding frequency components and in improving power amplifier behavior

Integration of broadband direct-conversion quadrature modulators

To increase spectral efficiency, transmitters usually send only one of the information carrying sidebands centered around a single radio-frequency carrier. The close-lying mirror, or image, sideband will be eliminated either by the filtering method or by the phasing method. Since filter Q-values rise in direct relation to the transmitted frequencies, the filtering method is generally not feasible for integrated microwave transmitters. A quadrature modulator realizes the phasing method by combining signals phased at quadrature (i.e. at 90° offsets) to produce a single-sideband (SSB) output. In this way output filtering can be removed or its specifications greatly relieved so as to produce an economical microwave transmitter. The proliferation of integrated circuit (IC) technologies since the 1980s has further boosted the popularity of quadrature modulator as an IC realization makes possible the economical production of two closely matched doubly balanced mixers, which suppress carrier and even-order spurious leakage to circuit output. Another strength of IC is its ability to perform microwave quadrature generation accurately on-chip, and thereby to avoid most of the interconnect parasitics which could ruin high-frequency quadrature signaling. Nevertheless, all quadrature modulator implementations are sensitive to phasing and amplitude errors, which are born as a result of mismatches, from the use of inaccurate differential signaling, and from inadequacies in the phasing circuitry itself. A 2° phase error is easily produced, and it reduces the image-rejection ratio (IRR) to −30 dBc. Therefore, as baseband signals synthesized by digital signal processing (DSP) are sufficiently accurate, this thesis concentrates on analyzing and producing the microwave signal path of a direct-conversion quadrature modulator with special emphasis on broadband, multimode radio-compatible operation. A model of the direct-conversion quadrature modulator operation has been developed, which reveals the effect the circuit non-linearities and mismatch-related offsets have on available performance. Further, theoretical proof is given of the well-known property of improving differential signal balance that cascaded differential pairs exhibit. Among the practical results, a current reuse mixer has been developed, which improves the transmitted signal-to-noise-ratio (SNR) by 3 dB, with a maximum measured dynamic range of +158 dB. The complementary bipolar process was further used to extend the bipolar push-pull stage bandwidth to 9.5 GHz. At the core of this work is the parallel switchable polyphase (PP) filter quadrature generator that was developed, since it makes possible accurate broadband IQ generation without the high loss that usually results from the application of PP filtering. Two IQ modulator prototypes were realized to test simulated and theoretically derived data: the 0.8 µm SiGe IC achieves an IRR better than −40 dBc over 0.75-3.6 GHz, while the 0.13 µm digital bulk CMOS IC achieves better than −37 dBc over 0.56-4.76 GHz. For this IRR performance the SiGe prototype boasts the inexpensive solution of integrated baluns, while the CMOS one utilizes a coil-transmission line hybrid transformer at its LO input to drive the switchable PP filters.Taajuuksien käytön tehostamiseksi lähettimet lähettävät yleensä vain toisen informaatiota sisältävistä sivukaistoistaan yhdelle radiotaajuuksiselle kantoaallolle keskitettynä. Viereinen peilitaajuus eli sivukaista vaimennetaan joko suodattamalla tai vaiheistamalla signalointia sopivasti. Koska suodattimen hyvyysluvut nousevat suorassa suhteessa käytettyyn taajuuteen, ei suodatusmenetelmä ole yleensä mahdollinen mikroaaltotaajuusalueen lähettimissä. Kvadratuurimodulaattori toteuttaa vaiheistusmenetelmän yhdistämällä 90-asteen vaihesiirroksin vaiheistetut signaalit yksisivukaistaisen lähetteen tuottamiseksi. Näin voidaan korvata lähdön suodatus joko kokonaan tai lieventämällä vaadittavia suoritusarvoja, jolloin mikroaaltoalueen lähetin voidaan tuottaa taloudellisesti. Integroitujen piiriratkaisujen yleistyminen 1980-luvulta lähtien on edesauttanut kvadratuurimodulaattorin suosiota, koska integroidulle piirille voidaan taloudellisesti tuottaa kaksi hyvin ominaisuuksiltaan toisiaan vastaavaa kaksoisbalansoitua sekoitinta, ja nämä tunnetusti vaimentavat kantoaaltovuotoa ja parillisia harmoonisia piirin lähdössä. Toinen integroitujen piirien vahvuus on kyky tarkkaan mikroaaltoalueen kvadratuurisignalointiin samalla piirillä, jolloin vältetään suurin osa kytkentöjen parasiittisista jotka muutoin voisivat tuhota korkeataajuuksisen 90-asteen vaiheistuksen. Kaikki kvadratuurimodulaattorit ovat joka tapauksessa herkkiä vaiheistus- ja amplitudieroille, joita syntyy komponenttiarvojen satunnaishajonnasta, epätarkan differentiaalisen signaloinnin käytöstä, ja itse vaiheistuspiiristön puutteellisuuksista. Kahden asteen vaihevirhe syntyy helposti, ja tällöin sivukaistavaimennus heikkenee -30 dBc:n tasolle. Tämänvuoksi, ja olettaen että digitaalisella signaaliprosessorilla luotu kantataajuuksinen signalointi on riittävän tarkkaa, tämä väitöskirja keskittyy kvadratuurimodulaattorin mikroaaltotaajuuksisen signaalipolun analysointiin ja tuottamiseen painottaen erityisesti laajakaistaista, monisovellusradioiden kanssa yhteensopivaa toimivuutta. Kvadratuurimodulaattorin toimintamallia on kehitetty siten, että mallissa huomioidaan epälineaarisuuksien ja piirielementtien satunnaishajontojen vaikutus saavutettavalle suorituskyvylle. Lisäksi on teoreettisesti todistettu sinänsä hyvin tunnettu peräkkäin kytkettyjen vahvistinasteiden differentiaalisen signaloinnin symmetrisyyttä parantava vaikutus. Käytännön tuloksista voidaan mainita kehitetty virtaakierrättävä sekoitin, joka parantaa signaali-kohinasuhdetta +3 dB, suurimman mitatun dynaamisen alueen ollessa +158 dB. Samaa komplementaarista bipolaariprosessia käytettiin edelleen bipolaarisen vuorovaihe-asteen kaistan levittämisessä 9.5 GHz:iin. Yhtenä tämän työn tärkeimmistä tuloksista on kehitetty kytkimin valittavista rinnakkaisista monivaihesuodattimista koostuva kvadratuurigeneraattori, jolla on mahdollista tuottaa laajakaistaista IQ-signalointia ilman suurta häviötä joka yleensä liittyy monivaihesuodattimien käyttöön. Kaksi IQ-modulaattoriprototyyppiä toteutettiin simuloitujen ja teoreettisesti mallinnettujen tulosten testaamiseksi: 0.8 µm SiGe integroitu piiri saavuttaa paremman sivukaistavaimennuksen kuin -40 dBc yli 0.75-3.6 GHz, kun taas 0.13 µm digitaalipiirien tuottamiseen tarkoitetulla CMOS prosessilla toteutettu integroitu piiri saavuttaa paremman sivukaistavaimennuksen kuin -37 dBc taajuusalueella 0.56-4.76 GHz. Näihin sivukaistavaimennuksiin SiGe prototyyppi pääsee edullisesti integroiduin symmetrointimuuntajin, kun taas CMOS piirillä käytetään kela-siirtojohto-tyyppistä yhdistelmämuuntajaa LO-sisääntulossa josta ajetaan erikseen kytkettäviä monivaihesuodattimia.reviewe

Digital Filters and Signal Processing

Digital filters, together with signal processing, are being employed in the new technologies and information systems, and are implemented in different areas and applications. Digital filters and signal processing are used with no costs and they can be adapted to different cases with great flexibility and reliability. This book presents advanced developments in digital filters and signal process methods covering different cases studies. They present the main essence of the subject, with the principal approaches to the most recent mathematical models that are being employed worldwide

Analog Implementation of Fractional-Order Elements and Their Applications

With advancements in the theory of fractional calculus and also with widespread engineering application of fractional-order systems, analog implementation of fractional-order integrators and differentiators have received considerable attention. This is due to the fact that this powerful mathematical tool allows us to describe and model a real-world phenomenon more accurately than via classical “integer” methods. Moreover, their additional degree of freedom allows researchers to design accurate and more robust systems that would be impractical or impossible to implement with conventional capacitors. Throughout this thesis, a wide range of problems associated with analog circuit design of fractional-order systems are covered: passive component optimization of resistive-capacitive and resistive-inductive type fractional-order elements, realization of active fractional-order capacitors (FOCs), analog implementation of fractional-order integrators, robust fractional-order proportional-integral control design, investigation of different materials for FOC fabrication having ultra-wide frequency band, low phase error, possible low- and high-frequency realization of fractional-order oscillators in analog domain, mathematical and experimental study of solid-state FOCs in series-, parallel- and interconnected circuit networks. Consequently, the proposed approaches in this thesis are important considerations in beyond the future studies of fractional dynamic systems

Use of frequency response masking technique in designing A/D converter for SDR.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.Analog-to-digital converters (ADCs) are required in almost all signal processing and communication systems. They are often the most critical components, since they tend to determine the overall system performance. Hence, it is important to determine their performance limitations and develop improved realizations. One of the most challenging tasks for realizing software defined radio (SDR) is to move ND conversion as close to the antenna as possible, this implies that the ADC has to sample the incoming signal with a very high sample rate (over 100 MSample/s) and with a very high resolution (14 -to -16 bits). To design and implement AID converters with such high performance, it is necessary to investigate new designing techniques. The focus in this work is on a particular type of potentially high-performance (high-resolution and highspeed) analog-to-digital conversion technique, utilizing filter banks, where two or more ADCs are used in the converter array in parallel together with asymmetric filter banks. The hybrid filter bank analog-todigital converter (HFB ADC) utilizes analog filters (analysis filters) to allocate a frequency band to each ADC in a converter array and digital synthesis filters to reconstruct the digitized signal. The HFB improves the speed and resolution of the conversion, in comparison to the standard time-interleaving technique by attenuating the effect of gain and phase mismatches between the ADCs. Many of the designs available in the literature are compromising between some metrics: design complexity, order of the filter bank (computation time) and the sharpness of the frequency response rolloff (the transition from the pass band to the stop band). In this dissertation, five different classes of near perfect magnitude reconstruction (NPMR) continuoustime hybrid filter banks (CT HFBs) are proposed. In each of the five cases, two filter banks are designed; analysis filter bank and synthesis filter bank. Since the systems are hybrid, continuous time IlR filter are used to implement the analysis filter bank and digital filters are used for the synthesis filter bank. To optimize the system, we used a new technique, known in the literature as frequency response masking (FRM), to design the synthesis filter bank. In this technique, the sharp roll-off characteristics can be achieved while keeping the complexity of the filter within practical range, this is done by splitting the filter into two filters in cascade; model filter with relaxed roll-off characteristics followed by a masking filter. One of the main factors controlling the overall complexity of the filter is the way of designing the model filter and that of designing the masking filter. The dissertation proposes three combinations: use of HR model filter and IlR masking filter, HR model filter/FIR masking filter and FIR model filter/FIR masking filter. To show the advantages of our designs, we considered the cases of designing the synthesis filter as one filter, either FIR or IlR. These two filters are used as base for comparison with our proposed designs (the use of masking response filter). The results showed the following: 1. Asymmetric hybrid filter banks alone are not sufficient for filters with sharp frequency response roll-off especially for HR/FIR class. 2. All classes that utilize FRM in their synthesis filter banks gave a good performance in general in comparison to conventional classes, such as the reduction of the order of filters 3. HR/HR FRM gave better performance than HR/FIR FRM. 4. Comparing HR/HR FRM using FIR masking filters and HR/IIR FRM using IIR masking filters, the latter gave better performance (the performance is generally measured in terms of reduced filter order). 5. All classes that use the FRM approach have a very low complexity, in terms of reduced filter order. Our target was to design a system with the following overall characteristics: pass band ripple of -0.01 dB, stop band minimum attenuation of - 40 dB and of response roll-off of 0.002. Our calculations showed that the order of the conventional IIR/FIR filter that achieves such characteristics is aboutN =2000. Using the FRM technique, the order N reduced to aboutN = 244, N = 179 for IIRJFIR and IIR/IIR classes, respectively. This shows that the technique is very effective in reducing the filter complexity. 6. The magnitude distortion and the aliasing noise are calculated for each design proposal and compared with the theoretical values. The comparisons show that all our proposals result in approximately perfect magnitude reconstruction (NPMR). In conclusion, our proposal of using frequency-response masking technique to design the synthesis filter bank can, to large extent, reduce the complexity of the system. The design of the system as a whole is simplified by designing the synthesis filter bank separately from the design of the analysis filter bank. In this case each bank is optimized separately. This implies that for SDR applications we are proposing the use of the continuous-time HFB ADC (CT HFB ADC) structure utilizing FRM for digital filters