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Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on

Issue 7 • Date July 2003

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Displaying Results 1 - 8 of 8
  • Design of optimal and narrow-band Laguerre filters for sigma-delta demodulators

    Page(s): 368 - 375
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (571 KB) |  | HTML iconHTML  

    Conventional sigma-delta (Σ-Δ) decimation methods are not optimal because the downsampling operation following the noise-shaping filters enables some quantization noise to alias back into the baseband. This paper proposes a novel decimation method that simplifies the implementation of the decimation process. This method makes use of an optimal Laguerre filter as the noise-shaping filter followed by another Laguerre filter that acts as a narrow-band filter. Conventional finite-impulse response (FIR) low-pass filters such as the optimal FIR filter and Sinck filter are commonly used as noise-shaping filters in Σ-Δ demodulators. As an alternative, optimal infinite-impulse response (IIR) filter architecture based on orthonormal Laguerre functions is used in the proposed decimation scheme. An optimal Laguerre IIR filter design methodology is presented via the optimization of a quadratic function subject to a linear and quadratic constraint. An efficient procedure to perform the optimization is introduced. A Laguerre IIR filter can also be used as the narrow-band filter before the decimation process. In this paper, a narrow-band Laguerre filter design methodology is presented via a digital frequency transformation. The narrow-band Laguerre filter can then be efficiently designed using a min-max criterion via a modified Parks-McClellan FIR filter design algorithm. View full abstract»

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  • Speeding up an integer-N PLL by controlling the loop filter charge

    Page(s): 343 - 354
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (558 KB) |  | HTML iconHTML  

    This paper studies a group of methods designed to speed-up the frequency step response of integer-N phase-locked loops (PLLs). The methods are based on current signals connected to the loop filter. Optimal speed-up waveforms are found mathematically using a linear PLL model. The paper also discusses problems associated with this theoretical waveform and introduces a considerably simpler waveform based on the use of two current pulses. This method uses excess output frequency to quickly cancel the accumulated phase error. In order to accelerate the decay of the phase error, the PLL is first overdriven at the beginning of the frequency transition with an external charge pulse to the loop filter. As the phase error goes rapidly to zero, the frequency error is also reduced to zero by another charge pulse. The theory presented here is verified by measurements using a practical RF synthesizer. View full abstract»

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  • Polyphase filter section with opamps

    Page(s): 376 - 378
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (234 KB) |  | HTML iconHTML  

    An RC active polyphase filter section is presented. The section uses three conventional operational amplifiers (opamps). The transfer function has a single pole and optionally a single zero. With a cascade of these sections, any polyphase filter function can be realized. The paper deals with the leakage caused by element deviation and the effects of a limited gain and gain-bandwidth product of the amplifiers. View full abstract»

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  • A computational kernel for fast and efficient compressed-domain calculations of wavelet subband energies

    Page(s): 389 - 392
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    This paper develops algorithms for calculating commonly used energy measures directly from the data stream of wavelet-compressed images. Incorporating these techniques into an underlying computational kernel allows many image-processing tasks to be efficiently implemented in the compressed domain. Compared to traditional decompress-process methods, the proposed techniques offer significant memory savings and reduce the computational load of the system. Experimental results show that the calculated energy values are accurate and obtained with less strain on system resources. The potential savings achieved by incorporating the proposed kernel are illustrated in a texture classification example. View full abstract»

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  • Two-channel digital and hybrid analog/digital multirate filter banks with very low-complexity analysis or synthesis filters

    Page(s): 355 - 367
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (803 KB) |  | HTML iconHTML  

    Multirate filter banks make use of analysis and synthesis filter banks. This paper introduces two-channel digital and hybrid analog/digital multirate filter banks where either the analysis or synthesis filters have a very low complexity. Such filter banks find application, for example, in high-speed analog-to digital converters where it is essential to minimize the complexity of the discrete-time or analog filters. The proposed digital filter banks are approximately perfect reconstruction (PR) filter banks, whereas the hybrid analog/digital filter banks can be chosen to be either approximately PR or approximately perfect magnitude reconstruction filter banks. The design is performed by first optimizing the digital or analog analysis filters and then, with the analysis filters fixed, optimizing the digital synthesis filters. This design procedure makes it possible to obtain analysis filters of very low order and complexity. The overall complexity is also low. Further, the proposed filter banks are, in all cases, very easy to design by making use of well-known and reliable optimization techniques; in particular, as small distortion and aliasing as desired are readily obtained because they are controlled in a linear programming problem. Several design examples are included, illustrating the properties of the proposed filter banks. View full abstract»

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  • Subband hyperstable adaptive IIR filters

    Page(s): 383 - 389
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (398 KB) |  | HTML iconHTML  

    Two subband implementations of hyperstability based adaptive infinite-impulse response (IIR) filtering algorithms are presented. These schemes are based on the polyphase decomposition of the adaptive filter and do not require cross filters to avoid aliasing. With this configuration, the larger the number of subbands, the more likely the SPR condition that this class of algorithms requires for convergence is to be satisfied. In addition, it is possible to assign different weights and/or compensating filters across the subbands, thus providing the designer with additional flexibility. View full abstract»

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  • An analog VLSI model of muscular contraction

    Page(s): 329 - 342
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (971 KB)  

    We have developed analog VLSI circuits to model the behavior demonstrated by biological sarcomeres, the force generating components of muscle tissue. The circuits are based upon the mathematical description of crossbridge populations developed by A. F. Huxley (1957). We have implemented the sarcomere circuit using a standard 1.2 μm process, and have demonstrated the nonlinear transient behaviors exhibited by biological muscle. View full abstract»

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  • Theory of gated multicycle integration (GMCI) for repetitive imaging of focal plane array

    Page(s): 378 - 383
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (343 KB) |  | HTML iconHTML  

    Gated multicycle integration (GMCI), a model of a directly gated readout circuit, is developed for repetitive imaging focal plane arrays (FPAs). The concept of GMCI is a combiner of gated integration (GI) and phase-sensitive integration (PSI). It differs from GI by its capability of background subtraction, and it differs from phase-sensitive integration by its duty cycle unlimited to 0.5. The operational modes of GMCI include the capacitive transimpedance amplifier (CTIA), GI, PSI (with background subtraction), multiple summation, multiple averaging, and some of their combinations. Through discussing the performance of one pixel, the analytical theory of GMCI provides the background limitations of gated and nongated FPAs. View full abstract»

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Aims & Scope

This title ceased production in 2003. The current updated title is IEEE Transactions on Circuits and Systems II: Express Briefs.

Full Aims & Scope