Showing papers on "Dynamic range published in 1990"

Companding current-mode integrator: A new circuit principle for continuous-time monolithic filters

Abstract: A new companding current-mode (CI) integrator principle is proposed. The integrator function is linear despite being composed of nonlinear parts. Its application promises monolithic filters with improved noise performance suitable for low supply voltages. A class AB circuit implementation is proposed which features an extended dynamic range.

Theory and design of the liquid crystal TV as an optical spatial phase modulator

Abstract: An expression is derived for the complex amplitude transmittance of the liquid crystal TV (LCTV) and verified experimentally. It is shown that spatial phase modulation is realizable with good linearity, high transmission efficiency, and small intensity distortion. Although the commercial LCTV does not provide a sufficiently large dynamic range for continuous phase modulation, a dynamic range of 2'rr can be obtained by making appropriate changes in the design.

Design considerations for high-frequency continuous-time filters and implementation of an antialiasing filter for digital video

Abstract: An approach that has made possible the integration of video frequency continuous-time filters with wide dynamic range is discussed. The tuning scheme necessary to maintain the stable and accurate frequency response in the presence of temperature variations, process tolerance, and aging is described. Detailed design techniques specific to high-frequency operation are introduced to implement a 5-V, seventh-order elliptic analog magnitude filter for antialiasing in digital video applications. The filter, based on a G/sub m/-C technique, exhibits a dynamic range of 61 dB and dissipates a power of 75 mW. Ninety-two chips from various wafers and two different process runs were tested. Seventy-five percent of the fabricated chips were functional, and 63% of them met the commercial-grade specifications in spite of an error in the layout which forced the phase control circuitry to perform suboptimally. >

Signal-to-noise in phase angle reconstruction: dynamic range extension using phase reference offsets.

Abstract: The dynamic range of phase-reconstructed magnetic resonance images is compared to that of magnitude-reconstructed images. From analysis of propagation of errors, the phase angle noise is phase-independent and given in radians by σ (|I|)/|I|, the noise-to-signal ratio of the corresponding magnitude-reconstructed image. As the phase can range from minus π to π the phase angle dynamic range is 2π times that of the signal magnitude. These results agree with experiment, verifying that the noise in the two receiver channels is uncorrelated. An artifact-free technique is presented for correcting phase spillover, which further extends the phase angle dynamic range. The reconstruction-based reference phase is adjusted on a local basis so that the boundary of phase wraparound is reconstructed near the center of the [ − π, π] interval. For a particular flow study, the phase signal-to-noise was extended over twofold by spillover correction, to a value 15 times that of the magnitude signal-to-noise. © 1990 Academic Press, Inc.

Determination of physiological levels of glucose in an aqueous matrix with digitally filtered Fourier transform near-infrared spectra.

Abstract: A procedure is described for the measurement of clinically relevant concentrations of glucose in aqueous solutions with near-infrared (NIR) absorbance spectroscopy. A glucose band centered at 4400 cm-1 is used for this analysis. NIR spectra are collected over the frequency range 5000-4000 cm-1 with a Fourier transform spectrometer. A narrow-band-pass optical interference filter is placed in the optical path of the spectrometer to eliminate light outside this restricted range. This configuration provides a 2.9-fold reduction in spectral noise by utilizing the dynamic range of the detector solely for light transmitted through the filter. In addition, a novel spectral processing scheme is described for extracting glucose concentration information from the resulting absorbance spectra. The key component of this scheme is a digital Fourier filter that removes both high-frequency noise and low-frequency base-line variations from the spectra. Numerical optimization procedures are used to identify the best location and width of a Gaussian-shaped frequency response function for this Fourier filter. A dynamic area calculation, coupled with a simple linear base-line correction, provides an integrated area from the processed spectra that is linearly related to glucose concentrations over the range 1-20 mM. The linear calibration model accurately predicted glucose levels in a series of test solutions with an overall mean percent error of 2.5%. Based on the uncertainty in the parameters defining the calibration model and the variability of the magnitudes of the integrated areas, an overall uncertainty of 7.8% was estimated for predicted glucose concentrations.

Wide dynamic range direct accelerometer

Abstract: The acceleration input-digital-output sigma-delta modulator accelerometer and the finite-element analysis of the mechanical structure are described. The performance obtained from prototype units is also presented. Silicon micromachining techniques were used to fabricate a high-precision, micro-gee accelerometer. Operating in a closed-loop configuration, the accelerometer utilizes electrostatic field sensing and electrostatic force feedback. The sensor assembly consists of three silicon chips, bonded together at the wafer level. The micromachined sensor is operated in a vacuum to eliminate nonlinear viscous damping and to provide a high-Q second-order mechanical resonant circuit. Near-critical damping is provided by the closed-loop control system. The control system is a highly oversampled sigma-delta modulator that produces a wide dynamic range and a direct digital output. These accelerometers can be built to serve widely diverse markets at a reasonable cost. Frequency ranges from DC to thousands of hertz, accelerations from nano-gees to hundreds of gees, and dynamic ranges in excess of 120 dB can all be accommodated in small rugged silicon accelerometers. >

An enhancement-mode MOS voltage-controlled linear resistor with large dynamic range

Abstract: It is shown that the depletion-mode linear resistor of Babanezhad and Temes (IEEE J. Solid-State Circuits, vol. SC-19, p.932-8, 1984) can be implemented in enhancement-mode devices. This allows a large increase in the dynamic range of the resistors. By inserting a bias source, the linearity can also be improved. A layout and experimental results on the resulting IC are included. >

ASIC image sensors

Abstract: Two image array sensors designed and fabricated using a standard two-level metal ASIC CMOS process are described. The results show that good quality grey-level images can be formed, and that CMOS sensors arrays can be successfully integrated with efficient analogue sense amplifiers and with digital control/image-processing logic. The first sensor is a prototype 128*128 pixel test array. The second is a 312*287 pixel image sensor chip which includes all the necessary circuitry to produce full PAL format video output, as well as automatic electronic exposure control and built-in test circuits. Test results characterizing the devices are given, covering dynamic range, spectral response, sensitivity, resistance to blooming, etc. Some potential applications for such devices are mentioned. >

One bit higher order sigma-delta A/D converters

Abstract: A topology for higher-order sigma-delta modulations is described, and synthesis equations are given which allow for the arbitrary shaping of the signal and quantization noise transfer functions. The synthesis procedure is similar to that of switched-capacitor filters and uses switched-capacitor design techniques such as dynamic-range scaling, impedance scaling, and circuit noise analysis. Placement of passband zeros for the optimization of the quantization noise transfer functions is discussed, and some results measured on a third-order test chip are presented. Simulated results on nonlinear stabilization of the loop are discussed. The need for simulating the analog front-end along with the digital filters to find the true dynamic range of the system is indicated. >

Third order sigma delta oversampled analog-to-digital converter network with low component sensitivity

Abstract: An improved modulator network for an interpolative oversampled (sigma-delta) analog-to-digital converter comprises a second-order modulator, which performs double integration of error between its digital output signal and its analog input signal, and a first-order modulator, which performs single integration of error between its digital output signal and an analog signal supplied thereto from the second-order modulator. The modulators supply their output signals to a digital error cancellation circuit which suppresses in the signal supplied to a decimation filter the quantization noise arising in the second-order modulator. The network exhibits significantly reduced sensitivity to the practical nonidealities that normally limit the resolution of analog-to-digital converters of this type, i.e., component matching, amplifier nonlinearity, finite gain, settling time, and signal dynamic range.

Electronically-scanned white light interferometry with enhanced dynamic range

Abstract: When a CCD array is used to detect the spatial fringes of optical interference, interesting features emerge in the output as the width of each fringe approaches the dimension of a CCD sensing cell. These features are theoretically studied and their application to the enhancement of the dynamic operating range of electrically scanned white-light interferometry is investigated. Preliminary experimental results are presented.

A digital video camera system

Abstract: A new video camera control system developed for extending the dynamic range of present single-chip CCD (charge coupled device) cameras whose dynamic range is inherently limited is discussed. This is accomplished by controlling the dynamic range using a signal which discriminates the contrast of the object, by compensating the white balance by detecting achromatic parts of the object out of video signals, and by reducing pseudocolor effects produced at a region where high-frequence components are abundant. Saturation and glooming problems associated with present consumer-use video cameras caused by the narrow dynamic range of the single CCD camera system and lack of signal processing capability are solved. The approach adopted prevents excessive iris closing under back lighting and saturation of a locally bright area of images produced by excessive forward lighting. >

Quiescent signal compensated photodetector system for large dynamic range and high linearity

Abstract: The linearity and dynamic range of a photodetector system is enhanced by providing real time cancellation of condition-dependent quiescent output signals from the photosensitive devices by provision of a condition-dependent output signal monitoring device which drives the input section of a current mirror having output sections connected to the active photosensitive devices to zero out the condition-dependent quiescent output signals of those photosensitive devices during system operation. Multiple output sections may be run from a single input section of the current mirror.

Use of heterodyne detection to measure optical transmittance over a wide range.

Abstract: We are developing a heterodyne detection technique to measure optical transmittance with high accuracy over an unprecedented dynamic range. We have measured filters spanning a wide range of transmittances (12 orders of magnitude) and have evaluated the absolute uncertainties and discuss the ultimate accuracies that may be achieved. Our setup uses a two-beam Mach-Zehnder interferometer with acoustooptic frequency shifting to produce a frequency difference between the two light beams. We determine the optical transmittance of a filter by inserting it into one of the interferometer arms and measuring the change in amplitude of the signal at the difference frequency on the interferometer output beam. This method allows direct comparisons between optical and rf attenuators, ultimately tying optical transmittance measurements to rf attenuation standards in an absolute way.

Low frequency noise canceling photodetector preamplifier useful for computerized tomography

Abstract: A preamplifier interfaces low level current-mode signals, such as from a photodetector in a computerized tomography system, to a corresponding voltage-mode signals, with a dynamic range on the order of 120 dB. The preamplifier can be implemented in CMOS technology to allow for complete integration of the computerized tomography interface function, including analog-to-digital conversion, of several channels in a single integrated circuit. The CMOS circuit accepts a current signal at its input and, after integration of the signal, produces a voltage output wherein the low frequency noise that is normally encountered with MOS transistors is cancelled through the use of correlated-double sampling. The circuit limits high frequency noise through use of low-pass filtering.

Extended dynamic range one dimensional spatial light modulator

Abstract: An optical information system which uses a liquid crystal television (LCTV) as a one dimensional spatial light modulator (SLM) is presented. An optical carrier wave is generated by polarizing and collimating the output of a laser. The liquid crystal television modulates the optical carrier wave with a digital modulating signal to output thereby a modulated optical signal: An array of photodetectors electroptically connects the modulated optical signal into a modulated electrical signal which is displayed on an oscilloscope. The use of an LCTV as a one dimensional SLM yields higher numerical accuracy and extended dynamic range than two dimensional SLM applications of the same equipment.

Apparatus and method for monitoring radiant energy signals with variable signal gain and resolution enhancement

Abstract: A sensor board for use with an endpoint controller which monitors light intensity is provided. The sensor board can provide a dynamic range of up to five million because a constant current driver and phase sensitive detector help eliminate noise from the detected signal. The sensor board can also subtract a DC voltage offset from the detected signal and amplify the difference to provide increased resolution of small changes in the detected signal.

Audio compressor, expander, and noise reduction circuits for consumer and semi-professional use

Abstract: Three related embodiments of audio signal dynamic range circuits for consumer and semi-professional audio signal compressors, expanders, and compressor/expander noise reduction systems incorporate certain basic features of professional Spectral Recording (SR) while adapting SR for use with consumer recording media (particularly audio cassette tape) and reducing the cost and complexity of the SR circuitry In addition, the three embodiments, and particularly the preferred embodiment, provide substantial compatibility with the existing B-type and C-type consumer and semi-professional noise reduction systems Subjective performance substantially equivalent to 16-bit PCM audio systems is achieved with analog audio cassette tape media In all three embodiments there are two cascaded stages: (1) a high-level stage a high-frequency fixed-band/sliding band action-substitution sub-stage (324A) and a low-frequency fixed-band sub-stage (328A) and (2) a low-level stage having only a high-frequency fixed-band/sliding band action-substitution sub-stage (326A) The dynamic action regions of the high-frequency action-substitution sub-stages are staggered Each of the high-frequency sub-stages provides up to 12 dB of dynamic action (together providing up to 24 dB of dynamic action) and operates in a frequency band defined by a single-pole filter having a high-pass shelving response with a corner frequency of 400 Hz The low-frequency sub-stage provides up to 10 dB of dynamic action and operates in a frequency band defined buy a single-pole filter having a low-pass shelving response with a corner frequency of 200 Hz The single-pole filter characterisctics provide a broad and smooth overlap of the high-frequency and low-frequency characteristics Particular forms of spectral skewing and antisaturation enhance the performance of the circuits with consumer recording media

Signal-to-noise ratio and maximum information content of images displayed by a CRT

Abstract: This paper describes the results of measurements which permit determination of the maximum information content of images displayed with a high resolution CRT of a nominal pixel matrix of 2000 x 2000 adressable pixels. These measurements are based on the precise determination of signal, noise and spatial resolution. Noise is measured both as temporal noise and as spatial noise, using both temporal and spatial sampling techniques. The dynamic range as given by the maximum and minimum values of luminance can be as high as 1900, however for practical settings of brightness and contrast it is about 424. The dynamic range is reduced from 424 to 1 38 as a result of veiling glare when the SMPTE pattern is displayed. The spatial noise was significantly larger than the temporal noise: For a command level of GL = 255, a single pixel and a single CRT frame, the temporal signal-to-noise Eatio was 59, while the spatial signal-to-noise ratio was only 7. The RMS noise (both spatial and temporal) was proportional to the squareroot of the respective bandwidths. Both temporal and spatial noise power spectra were independent of their respective frequencies (white noises). In the average, the size of a pixel was much larger than the size of an addressable pixel, indicating, that the total number of usable pixels was smaller than the number of addressable pixels: Instead of the addressable pixelmatrix of 2000 x 2000 pixels, we estimated only 532 x 548 "Noise-Equivalent" pixels. It was estimated, that for spatial integration over a single pixel and temporal integration over a single CRT frame, the maximum information content of images produced by this monitor, is 1.72 x 106 bits, based on temporal noise; however due to spatial noise that number is reduced to 1.28 x 106 bits. This contrasts sharply with the nominal information content of 3.2 x 107 bits as determined from the nominal raster of 2000 x 2000 pixels and the 8 bits digitization at the display buffer.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Nonlinear amplitude compression in magnetic resonance imaging: quantization noise reduction and data memory saving

Abstract: Dynamic range improvement in magnetic resonance imaging (MRI) by nonlinear amplitude compression is proposed. Quantization noise reduction by a factor of 10 to 20 is confirmed by a numerical simulation, provided an appropriate nonlinear transform is chosen. The piecewise-linear transform is the best nonlinear transform studied so far. Implementing amplitude compression requires no additional hardware in a usual MRI system if the low spatial frequency lines of the magnetic resonance (MR) signal are selectively prescanned through an attenuator. The method will be particularly effective in 3-D imaging of large objects. MR angiography, and imaging of solids. >

Method and apparatus for signal companding

Abstract: A method and apparatus for signal companding is disclosed that incorporates a log-offset companding technique to provide both a high bandwidth over the dynamic range of the signal being processed as well as temperature stability. In addition, the incorporation of log-offset companding technique provides the capability of generating a family of transfer curves. The ability to provide a family of transfer curves is particularly useful, for example, in telecine machines adapted to scan more than one type of film.

An algorithm to compensate for source spectral impurity in dynamic range measurements (ADCs)

Abstract: An algorithm to compensate for the effect of signal-source distortion in the measurement of the dynamic performance of analog-to-digital converters (ADCs) is described. The algorithm uses two sets of measurements: one set taken with the function generator and another taken with an all-pass filter inserted between the function generator and the ADC. Simulation results indicate that ADCs with a dynamic range of 60-70 dB can be measured with an absolute accuracy of better than 0.2 dB using a signal generator that has -40 dB distortion components. >

Design of a very linear CMOS transconductance input stage for continuous-time filters

Abstract: A CMOS differential input stage for transconductance amplifiers that combines a low noise excess factor, low input capacitance, and high common-mode rejection ratio with a very good linearity is described. The measured distortion is only 0.2% for a 1-V RMS input signal and only 1% for a 2-V RMS input signal on a test circuit implemented in a standard 3- mu m CMOS process, using +or-5-V supplies, resulting in over 85 dB of dynamic range. Applications include high-performance continuous-time filters and linear amplifiers. >

Waveguide modulators with extended linear dynamic range-a theoretical prediction

Abstract: A novel modification of the directional coupler modulator is described that reduces the nonlinear distortion and improves the linear dynamic range. The calculated results indicate that the ratio of optical signal power to the spurious signal power of this device is 30-40 dB larger than that of a Mach-Zehnder interferometric modulator. >

Dynamic range enlarging system

Abstract: PURPOSE:To enlarge the dynamic range of an imager by adding and/or averaging the read signals for plural times outputted from the non-destructive read type imager. CONSTITUTION:A non-destructive read type imager 21 is driven by a driver 29, the driver 29 is controlled by a timing control circuit 30, and an exposure start signal and read signals at different timing are supplied to the imager 21 by a driver 29. The photoelectric converting output of the imager 21 is compressed to a logarithmic value by guiding to a logarithm converting circuit 22, its output is guided to a clipping circuit 23, and the output of the clipping circuit 23 is converted into a digital value by guiding to an A/D converter 24. The signal, which is converted into the digital value, is inputted to an addition/averaging circuit 25, the output of the A/D converter 24 and the memory value of a buffer memory 26 are added, and their mean value is calculated. Thus, the dynamic range of the imager can be effectively enlarged.

Calibration of flow cytometer detector systems

Abstract: Publisher Summary Flow cytometers measures fluorescence intensity, but no standard method for the quantitative expression of results has been adopted. It is due to the dependence of these data on instrument alignment, laser power, optical filters, photomultiplier tube (PMT) sensitivity, and display mode and resolution. With so many factors potentially contributing to the values assigned to any sample intensity, it is often most convenient to intercompare experimental samples simply by choosing appropriate machine settings and collecting a frequency histogram of fluorescence intensity for each sample without changing the measurement conditions. This approach produces data with the greatest possible resolution when small differences in sample intensity are expected. In the case of linear amplification, the resolution and dynamic range are dependent on the number of channels selected for analog-to-digital signal conversion; for logarithmic amplification, the dynamic range is limited by that of the amplifier itself, and overall resolution is decreased. The chapter describes a method for the conversion of logarithmic data to linear format. Using this procedure, data acquired in either the log or linear format can be reduced to the same values for relative fluorescence intensity.

Incrementally lossless, broad-bandwidth analog fiber-optic link

Abstract: Operation of a broadband, incrementally lossless, fiber-optic link is reported. By using a solid-state laser as the CW source, a dynamic range for this externally modulated link was measured and shown to exceed that of a directly modulated link. The modulator was a conventional Mach-Zehnder design. The average optical power on the detector was 20 mW. The modulator input and detector output are resistively terminated with 50 Omega , and the link RF-to-RF insertion loss vs. frequency is measured using an RF network analyzer. The maximum intermodulation-free (IM-free) dynamic range occurs at the optical modulation depth (OMD) for which the output intermodulation power equals the link output noise power. Consequently, the maximum IM-free dynamic range depends not only on the linearity of the modulating device, but also on the sources of noise in the link. >

Picture data compression

Abstract: A highly efficient coding apparatus for picture data for splitting an input digital picture signal into component data of plural frequency bands and compressing and encoding the data of the each band, includes an encoder supplied with one or more data containing at least the component data of the band on the lowest frequency side among data of the plural bands and adaptive to dynamic range. The encoder comprises a block segmentation circuit for converting input data into data of a block structure, a detection circuit for detecting a maximum value MAX, a minimum value MIN and a dynamic range DR of the blocks, a subtraction circuit for subtracting the maximum value MAX or the minimum value MIN from the input data, and a quantisation circuit for encoding an output signal of the subtraction circuit to be adaptive to the dynamic range DR.

Contact type image sensor device with specific capacitance ratio

Abstract: A contact type image sensor device comprises a plurality of photodiodes connected in a matrix, and an equal number of blocking diodes. A capacity ratio of a photo electric part constituting the photodiodes to a diode part constituting the blocking diode is in the range of 2:1 to 30:1. Dynamic range, magnitude of the signal current, light sensitivity and after image characteristics of the image sensor are improved according to the invention.

Interactive type dynamic range adjustment method and apparatus for digital image

Abstract: PURPOSE: To efficiently execute image dynamic range adjustment by separating image data into low frequency components and high frequency components and executing a compression processing only to the low frequency components among them. CONSTITUTION: Three-color images are supplied to an RGB-luminance and hue transformation matrix 100 and luminance signals are supplied to a low-pass filter 120. The first output of the filter 120 is supplied to the negative input of' an addition circuit 110 and the difference signals of the luminance signals and the luminance signals from which a high frequency band is removed are outputted from the addition circuit 110. A transformation block 160 receives hue signals from a block 100, combines them with output signals from the addition circuit 110 and outputs RGB signals and a form type curve block 170 modulates the RCB signals corresponding to the characteristics of a form. In such a manner, by making a user perform contrast adjustment only to the low frequency components of images on an interactive basis by using a mapping curve, a most suitable parameter is selected by the user.