-
[show abstract]
[hide abstract]
ABSTRACT: Auditory filter models have a history of over a hundred years, with explicit bio-mimetic inspiration at many stages along the way. From passive analogue electric delay line models, through digital filter models, active analogue VLSI models, and abstract filter shape models, these filters have both represented and driven the state of progress in auditory research. Today, we are able to represent a wide range of linear and nonlinear aspects of the psychophysics and physiology of hearing with a rather simple and elegant set of circuits or computations that have a clear connection to underlying hydrodynamics and with parameters calibrated to human performance data. A key part of the progress in getting to this stage has been the experimental clarification of the nature of cochlear nonlinearities, and the modelling work to map these experimental results into the domain of circuits and systems. No matter how these models are built into machine-hearing systems, their bio-mimetic roots will remain key to their performance. In this paper we review some of these models, explain their advantages and disadvantages and present possible ways of implementing them. As an example, a continuous-time analogue CMOS implementation of the One Zero Gammatone Filter (OZGF) is presented together with its automatic gain control that models its level-dependent nonlinear behaviour.
Circuits and Systems (ISCAS), Proceedings of 2010 IEEE International Symposium on; 07/2010
-
[show abstract]
[hide abstract]
ABSTRACT: Hyperbolic sine (Sinh) CMOS filters are of inherent class-AB nature and offer high dynamic range at half the total capacitance value when compared against their pseudodifferential class-AB log-domain counterparts. This characteristic renders their theoretical and practical study valuable. Only a very limited number of CMOS Sinh filter topologies have been reported in the literature to date mostly due to the considerably increased mathematical complexity associated with their design. This paper presents the transistor-level synthesis and investigates in detail the performance of a 3rd-order Sinh CMOS 8Hz low-pass filter of Bessel approximation suitable for ECG processing. The filter is based on recent progress made and has been designed in the commercially available 0.35 μm AMS process. Its static power consumption amounts to 0.1 μW while its dynamic range exceeds 110 dBs. The new filter exhibits a flat group delay of less than 1% error up to 6 Hz and good variability performance verified by means of Monte Carlo simulations. The suitability of the filter as part of an ECG front-end is confirmed by the processing of artificially generated ECG signals contaminated by various simulated noise sources and fed as signal inputs into the Cadence Design Framework.
Microelectronics (ICM), 2009 International Conference on; 01/2010
-
[show abstract]
[hide abstract]
ABSTRACT: This paper deals with the design and performance evaluation of a new analog CMOS cochlea channel of increased biorealism. The design implements a recently proposed transfer function, namely the One-Zero Gammatone filter (or OZGF), which provides a robust foundation for modeling a variety of auditory data such as realistic passband asymmetry, linear low-frequency tail and level-dependent gain. Moreover, the OZGF is attractive because it can be implemented efficiently in any technological medium-analog or digital-using standard building blocks. The channel was synthesized using novel, low-power, class-AB, log-domain, biquadratic filters employing MOS transistors operating in their weak inversion regime. Furthermore, the paper details the design of a new low-power automatic gain control circuit that adapts the gain of the channel according to the input signal strength, thereby extending significantly its input dynamic range. We evaluate the performance of a fourth-order OZGF channel (equivalent to an 8th-order cascaded filter structure) through both detailed simulations and measurements from a fabricated chip using the commercially available 0.35 mum AMS CMOS process. The whole system is tuned at 3 kHz, dissipates a mere 4.46 muW of static power, accommodates 124 dB (at < 5% THD) of input dynamic range at the center frequency and is set to provide up to 70 dB of amplification for small signals.
IEEE Journal of Solid-State Circuits 04/2009; · 3.23 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The scope of this paper is to present certain insights and advances towards the synthesis and transistor-level implementation of high dynamic range (> 120 dB), micropower, CMOS Sinh companding filters. In particular, we present detailed technical insights on a recently proposed Sinh integrator which may serve as the basic building block for higher-order filter structures. The particular integrator exhibits a promising simulated linearity performance mainly because it does not rely on the complementarity of both N- and P-type MOS transistors to achieve its Class-AB operation. Rather, it is designed with single-type devices in its signal processing path. The integrator is evaluated through detailed simulation results obtained by performing both large-signal transient and periodic steady-state (PSS) analyses in Cadence IC Design Framework<sup>reg</sup> with the parameters of the commercially available AMS 0.35-mum CMOS process. SNR, SNDR, IP3 and mismatch are some of the performance figures reported in this work. A detailed head-to-head comparison with a typical pseudo-differential Class-AB Log-domain integrator, designed in the same technology and with identical specifications, is also performed in order to reveal any potential benefits of the Sinh circuit paradigm.
Circuits and Systems I: Regular Papers, IEEE Transactions on 11/2008; · 1.97 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper a novel, practical, low-power, Class-AB companding hyperbolic sine (Sinh ) integrator based on the harmonic mean law is presented. MOS transistors operating in their weak inversion region are used for low power and low supply voltage operation. All translinear loops are implemented using single-type devices allowing for fabrication on standard, twin-well CMOS processes. Detailed simulation results from Cadence IC Design Framework and the commercially available AMS 0.35 mum process parameters are reported and discussed. The proposed circuit achieves more than 120 dB of input dynamic range, and a frequency tunability of over 4 decades with a power consumption of less than 1.5 muW. In addition, head-to-head comparison with our previously reported (ISCAS '07) geometric-mean Sinh integrator is performed in an attempt to shed more light on the potential of this very promising class of current-mode companding filters.
Circuits and Systems, 2008. ISCAS 2008. IEEE International Symposium on; 06/2008
-
[show abstract]
[hide abstract]
ABSTRACT: This paper outlines the design and simulated performance of a novel, current-mode, companding, Class-AB, Sinh lossy integrator. Prior Sinh filter designs utilize current conveyor-like blocks which incorporate both N- and P-type devices in alternate cascode arrangement to process the split-ted phases of the input. However, if these blocks were to be designed in weak inversion CMOS, the bulks of all the devices involved should be connected to their respective sources for accurate exponential/logarithmic conformity, which dictates the use of a triple-well process. Triple-well processes, apart from the fact that are not always available, have increased parasitics compared to twin-well ones, making the design and optimization of these already complicated filters a rather difficult one. In this paper, we present a new Sinh lossy integrator circuit that uses (either N- or) P-type devices rendering it to be practically realizable in any standard twin-well process. The circuit has been designed in 0.35mum AMS CMOS process with all simulation results obtained from Cadence Design Frameworkreg. The resulting lossy integrator exhibits a simulated input dynamic range greater than 120dB with only one integrating capacitor, while dissipating 0.3muW of power.
Circuits and Systems, 2007. ISCAS 2007. IEEE International Symposium on; 06/2007
-
[show abstract]
[hide abstract]
ABSTRACT: This paper deals with continuous-time filter transfer functions that resemble tuning curves at particular set of places on the basilar membrane of the biological cochlea and that are suitable for practical VLSI implementations. The resulting filters can be used in a filterbank architecture to realize cochlea implants or auditory processors of increased biorealism. To put the reader into context, the paper starts with a short review on the gammatone filter and then exposes two of its variants, namely, the differentiated all-pole gammatone filter (DAPGF) and one-zero gammatone filter (OZGF), filter responses that provide a robust foundation for modeling cochlea transfer functions. The DAPGF and OZGF responses are attractive because they exhibit certain characteristics suitable for modeling a variety of auditory data: level-dependent gain, linear tail for frequencies well below the center frequency, asymmetry, and so forth. In addition, their form suggests their implementation by means of cascades of N identical two-pole systems which render them as excellent candidates for efficient analog or digital VLSI realizations. We provide results that shed light on their characteristics and attributes and which can also serve as “design curves†for fitting these responses to frequency-domain physiological data. The DAPGF and OZGF responses are essentially a “missing link†between physiological, electrical, and mechanical models for auditory filtering.
EURASIP Journal on Audio, Speech, and Music Processing. 01/2007;
-
[show abstract]
[hide abstract]
ABSTRACT: The scope of this paper is to introduce two particular filter responses which closely resemble tuning curves at specific set of places on the basilar membrane (BM) of the biological cochlea. The responses are termed Differentiated All-Pole Gammatone Filter (DAPGF) and One-Zero Gammatone Filter (OZGF) and their form suggest their implementation by means of cascades of N identical two-pole systems, which makes them excellent candidates for efficient analog VLSI implementations. The resulting filters can be used in a filterbank architecture to realize cochlea implants or auditory processors of increased biorealism. In addition, their simple parameterization allows the use of conventional automatic gain control (AGC) schemes to model certain important features of the biological cochlea (e.g. level-dependent gain) that are observed physiologically. To illustrate the idea, we present preliminary simulation results from a 4th-order OZGF using novel high dynamic range log-domain biquads in CMOS weak inversion (CMOS-WI). All circuits were designed in Cadence® Design Framework, using the commercially available AMS 0.35¿m CMOS process. The reported OZGF structure has a simulated input dynamic range of 122.8dB, while dissipating 3.7¿W of static power.
Circuits and Systems, 2006. MWSCAS '06. 49th IEEE International Midwest Symposium on; 09/2006
-
[show abstract]
[hide abstract]
ABSTRACT: The scope of this paper is to evaluate the potential of Sinh filters synthesized by exploiting the exponential V-I relation of weakly inverted MOS devices. We report quiescent power consumption, tunability and linearity simulation results for: (a) a lowpass biquad, (b) a bandpass bi-quad and (c) a third-order Butterworth lowpass CMOS Sinh filter response using the 0.35 μm AMS process parameters. Frey's state-variable mapping procedure is followed. Key synthesis and performance limitations are identified.
Circuits and Systems, 2005. 48th Midwest Symposium on; 09/2005
