Showing papers on "Dynamic range published in 1989"

A noise-shaping coder topology for 15+ bit converters

Abstract: A topology for high-precision noise-shaping converters that can be integrated on a standard digital IC process is presented. This topology uses a multibit noise-shaping coder and a novel form of dynamic element matching to achieve high accuracy and long-term stability without requiring precision matching of components. A fourth-order noise-shaping D/A (digital-to-analog) conversion system using a 3-b quantizer and a dynamic element-matching internal D/A converter, fabricated in a standard double-metal 3- mu m CMOS process, achieved 16-bit dynamic range and a harmonic distortion below -90 dB. This multibit noise-shaping D/A conversion system achieved performance comparable to that of a 1-bit noise-shaping D/A conversion system that operated at nearly four times its clock rate. >

Wide dynamic range camera

Abstract: An image pickup apparatus includes image sensors (70-1, 70-2, ..., 70-n) for receiving an image at various exposure levels and circuitry (74) combining the results into a single image signal. This results in a significantly widened dynamic range of exposure.

Optical plankton analyser: a flow cytometer for plankton analysis, II: Specifications.

Abstract: An analysing flow cytometer, the optical plankton analyser (OPA), is presented. The instrument is designed for phytoplankton analysis, having a sensitivity comparable with commercially available flow cytometers, but a significantly extended particle size range. Particles of 500 microns in width and over 1,000 microns in length can be analysed. Sample flow rates of up to 55 microliters/s can be used. Also, the dynamic range of the instrument is significantly increased for particles larger than about 5 microns. The optics, hydraulics, and electronics of the instrument are described, including the best form for a low fluid shear cuvette. The new pulse quantification technique we call digital integration is presented. This technique is essential for the instrument to handle both short and very long particles with a large dynamic range. Test measurements demonstrating particle size range and dynamic range are presented. Dynamic ranges of 10,000 and 100,000 were typically observed, measuring field samples with Microcystis aeruginosa colonies, whereas one sample showed a dynamic range of 10(6). A simple method for interpretation of time of flight (TOF) data in terms of particle morphology is presented. The specifications of the instrument are given.

A novel bipolar imaging device with self-noise-reduction capability

Abstract: A bipolar image sensor with charge amplification and noise-reduction capabilities in each unit cell is discussed. The dynamic range of linearity in the photoelectric conversion characteristics has been greatly extended by using capacitor-loaded emitter-follower circuitry and a readout operation in a deep forward-base-emitter-biasing condition. The fixed pattern noise and the random noise are reduced by introducing a hybrid reset operation that is a combination of the clamp reset and the transient reset. >

Binning spectral images in a charge-coupled device

Abstract: : A charge coupled device (CCD) can selectively combine photogenerated charge from several detector elements into a single charge packet by a charge readout mode called binning. This article focuses on the use of charge binning in a two dimensional CCD for increasing the sensitivity and dynamic range of spectroscopic measurements. Binning allows the effective detector element size to be matched to the size of the slit image. Equations describing the signal to noise ration and dynamic range of the binned readout of spectral lines are developed. Results of binning to increase the sensitivity of atomic emission and molecular fluorescence measurements are presented. An intraspectral dynamic range of 500,000 is achieved by mixing binned and normal readout modes of a Hg atomic emission spectrum. Practical factors related to binning spectral images including spectral line orientation, readout speed, and blooming are discussed. Keywords: Charge coupled device; Multichannel detectors; Binning; Dynamic range; Spectroscopic performance; Mercury.

Optical receivers for wide band data transmission systems

Abstract: Optical receiver designs for digital fiber data transmission systems operating with Gb/s data rates in the 800-1500-nm wavelength region have been investigated. The tradeoffs among conflicting receiver design requirements are considered in detail. The state-of-the-art performance of photodetectors and low noise amplifiers is discussed. Present receiver performance data, such as sensitivity, dynamic range, bit rate, and bit pattern dependencies, as a function of the bit rate in the 0.01-8 Gb/s data rate range are reviewed. The highest experimental sensitivities have been obtained with InGaAs APDs (avalanche photodiodes) and high-impedance GaAs FET (field-effect transistor) preamplifiers. >

High-performance optical analog link using external modulator

Abstract: An experimental fiber-optic analog link with a noise figure of only 6-dB, a 104-dB intermodulation-free dynamic range (measured using a 10-Hz noise bandwidth), and an RF-to-RF gain of 11 dB at 50 MHz is discussed. The link includes no electronic amplification. It uses a very sensitive bandpass impedance-matched Ti:LiNbO/sub 3/ interferometric modulator and an input optical power of 55 mW at 1.32 mu m. >

A single-chip bipolar AGC amplifier with large dynamic range for optical-fiber receivers operating up to 3 Gbit/s

Abstract: A complete automatic gain control (AGC) main amplifier for gigabit-per-second optical-fiber transmission system was carefully designed and integrated on a single chip, using a standard 2- mu m silicon bipolar technology. Gain control was performed by use of the four-quadrant multiplier principle. The amplifier is characterized by a maximum voltage gain of 40 dB, a large input dynamic range of 40 dB, a maximum bit rate of 3 Gb/s, and a gain-independent 3-dB cutoff frequency of 2.5 GHz. The experimental results agree very well with the simulation predictions. >

Switched detector for beam position monitor

Abstract: The NSLS (National Synchrotron Light Source) storage rings use sets of four button electrodes to determine the transverse position of the stored electron beam in the vacuum chamber. By means of GaAs switches, the 211 MHz component of the induced signals on each of the four buttons is measured in turn by a single amplifier-detector channel. These signals are then stored in four sample and hold circuits. The measurement cycle is repeated at a rate of 40 kHz. The required sums and differences of these signals are obtained by analog means. The results are normalized with respect to beam intensity by servoing the gain of the amplifier-detector channel such that the sum of the signals from the four buttons is maintained at a fixed value. The prototype receiver provides +or-20 mu m resolution within a 300 Hz bandwidth over a 30 dB dynamic range. The receiver is relatively insensitive to beam energy and to the number of bunches stored in the machine. >

A Photodiode-Array-Based Near-Infrared Spectrophotometer for the 600–1100 nm Wavelength Region:

Abstract: We describe a silicon photodiode-array (PDA)-based near-infrared spectrophotometer for making molecular absorption/diffuse reflectance measurements in the 600-1100 nm wavelength range. Absorptions in this spectral region arise from both low-lying electronic states and vibrational overtones of CH, NH, and OH functional groups and combination bands. One disadvantage of silicon-based array detectors is their decreasing quantum efficiency at wavelengths longer than 950 nm. For transmission measurements, this can be compensated for by the technique of spectral plane masking, which markedly improves the consistency and overall level of baseline noise as well as the dynamic range. The instrument's performance is evaluated in the areas of spectral resolution, baseline noise, stray light, and dynamic range, and a comparison is made with a state-of-the-art mechanically scanned instrument. In the study, the PDA spectrometer attained a signal-to-noise ratio two times better than that of the commercial instrument with a time efficiency advantage of twelve, while achieving a spectral resolution three times greater. Finally, the application of analyzing caustic brine solutions by rapid-scanning NIR spectroscopy is illustrated.

Optically powered data link for power system applications

Abstract: The practicability of an optically powered data link has been demonstrated. The link has moderate bandwidth (1 kHz), accuracy (1%) and dynamic range (>60 dB) over a useful range of ambient temperatures. The link uses commercially available components, including a photodiode array fabricated using the dielectric isolation process in silicon. An application to the measurement of current in a high voltage line by means of a linear coupler is described, and experimental results are presented. Power transmission efficiency is presently low, at about 0.3% overall (electrical-to-electrical) and 5% optical-to-electrical. >

Wide dynamic range image sensor

Abstract: An abstract sensor array (10) includes adaptive sensitivity control circuitry (12) for obtaining multiple outputs at different exposure levels. These are combined to yield an output with enhanced dynamic range. This enhanced dynamic range may be reduced in a manner which preferentially retains edge information in order to maintain high contrast.

Enhancing the dynamic range of analog-to-digital converters by reducing excess noise

Abstract: A technique for improving the dynamic range of analog-to-digital converters (ADCs) is presented. The technique consists of summing outputs of several parallel N-bit ADCs to reduce the uncorrelated excess noise introduced by each ADC. This increases the number of effective bits of resolution and is most useful to regain bits lost after dithering to reduce spurious harmonics for spectral analysis applications. The sensitivity of this approach to uncertainties in component gain and delay is discussed. >

Photonic probes for the measurement of electromagnetic fields over broad bandwidths

Abstract: The characteristics of photonic systems that make them especially well suited for use as broadband electromagnetic (EM) field sensors are discussed. Transfer functions are given for the individual components of such a measurement system, with special emphasis given to those of Pockels-cell and modified-directional-coupler optical modulators. An isotropic electric-field meter having 15-cm resistively tapered dipole elements combined with bulk crystal, Pockels-cell modulators is described. The meter's frequency response is flat between 30 kHz and 100 MHz, except for resonances in the modulator crystals that occur between 1 and 10 MHz. For a 3-kHz detection bandwidth, the noise floor is equivalent to a field of about 7 V/m, and the calculated linear dynamic range is 70 dB in EM-field power density. The response is within +or-2 dB of the ideal isotropic response. A photonic probe that uses a modified directional-coupler modulator is briefly described. >

Dynamic range video black level expander

Abstract: A digital video signal black level expander in which the dynamic range of the video signal is the criterion for expansion. The digital video signal is compared pixel by pixel in maximum and minimum comparators and the maximum and minimum pixel values for each field are stored in latches. Integrators average the maximum and minimum pixel values over successive pairs of fields of the video signal. The integrated minimum pixel value is subtracted from the integrated maximum pixel value to determine the dynamic range of the pixels in the video signal. A tilt-point pixel value is established as a function of the dynamic range, above which no expansion is permitted. Digital video signals below the tilt point are expanded. Programmable constants are supplied to modify the dynamic range effect and the amount of expansion as desired. A low pass filter removes high frequencies prior to comparing pixel values.

Peak level detecting apparatus for image sensors which prevents saturation

Abstract: A peak level detecting apparatus for image sensors by which the maximum light value of a remote object is detected effectively utilizing the dynamic range of image sensors. The peak level detecting apparatus realizes a detection of the remote object patterns without any saturation in photoelectric devices by adjusting the exposure time with the detection of induced signal change in at least one of the photoelectric devices reaching the predetermined peak level, in order to improve the dynamic range and the signal to noise ratio.

Particle measuring method and apparatus

Abstract: Disclosed is a particle measurement method and apparatus for measuring particle properties in which a laser beam (5) is projected into a detection region (6) in a medium containing particles to be measured, and a photoelectric detector (11) having a predetermined dynamic range is used to detect the laser light scattered by the particles in the medium to produce signals which are evaluated to measure the particle properties. The polarization (S, P) of the laser beam and the intensity of the scattered light are regulated using filter means (10, 59) in accordance with the range of particle sizes measured so that the intensity of the scattered light is within the dynamic range of the photoelectric detector (11). This arrangement makes it possible to expand the range of particle sizes with an improved resolving power in particle measurement without multi-valued ranges.

High efficiency coding device

Abstract: PURPOSE: To prevent generation of mismatching between the encoder side and the decoder side by applying the buffering processing based on an original dynamic range DR, comparing a corrected dynamic range DR' and a threshold level decided by the buffering processing so as to apply quantization. CONSTITUTION: A bit number decision circuit 19 receives an output signal of a comparator circuit 20. A corrected dynamic range DR' from a subtraction circuit 15 and threshold levels T1-T4 (T1

Optical homodyne phase metrology

Abstract: Electronic circuitry that is helpful for measuring optical phase from three-phase input signals is described. Six flash analog-to-digital converters in conjunction with a read-only memory resolve a digital byte (or more) per turn of phase. That digital phase may then be digitally low pass filtered with an adder and multiplier accumulator to expand the dynamic range by counting turns and shrinking the subdivisions.

Implementation considerations and limitations for dynamic range enhanced analog to digital converters

Abstract: The authors review the operation of single and cascade oversampled noise-feedback converters operating with multilevel ADCs (analog/digital converters). Attention is given to techniques for improving the accuracy and the dynamic range of ADCs by operating a reduced resolution quantizer in a feedback loop. These techniques are seen to be special cases of noise-feedback coding in which the loop operates at sample rates far in excess of the signal bandwidth and uses spectral noise shaping to shift in-band quantizing noise power to out-of-band spectral positions. It is noted that implementing these techniques at very high sample rates (10/sup 8/ samples per second) with combinations of analog and digital subsystems offers a number of challenging signal processing problems. It is shown that the mix of analog and digital segments and the ADC-DAC (digital/analog converter) delays have significant deleterious effects on the loop performance. >

Wideband bipolar multiplier IC with high dynamic range for use in coherent optical receivers

Abstract: A novel silicon bipolar multiplier IC with low input power requirements was implemented in a 560Mbit/s DPSK demodulator of a phase-diversity receiver. Error-free detection was achieved over a dynamic range of 25 dB.

D/a conversion circuit

Abstract: The invention provides a D/A conversion circuit in which the polarities of a series of input digital data are reversed (1a) with every other data block, and the original digital data and the reversed digital data are alternately D/A converted (2). An output analog signal (f) is obtained by subtraction (6) between the two D/A converted analog signals (d, e). With the above-mentioned arrangement, the D/A conversion circuit has a dynamic range equivalent to that using two D/A converters even with a single D/A converter.

Minimization of nonlinear acousto-optic Bragg cell intermodulation products

Abstract: The acoustooptic Bragg cell intermodulation products (IMPs) arising from multiple optical diffraction (dynamic IMPs) fundamentally limit Bragg-cell dynamic range. The IMPs arising from acoustic harmonic waves generated by the nonlinear elastic response of the Bragg cell crystalline lattice (elastic IMPs) may further limit dynamic range in Bragg cells operating at high frequencies or long time apertures. It is shown that the elastic IMPs can be minimized by increasing the Bragg-cell transducer length. The length can be increased without the attendant bandwidth loss using a phased array transducer. It is shown experimentally that this device is limited in dynamic range by the dynamic IMPs and thus exhibits the maximum spurious-free dynamic range possible. >

A study on an active square-law combining method for a polarization-diversity coherent optical receiver

Abstract: A polarization-diversity coherent optical receiver which realizes ideal square-law combining with active gain control is described. This receiver can suppress the additional power penalty due to the demodulator dynamic range limitation by equivalently expanding the demodulator dynamic range. A low-power penalty less than 1 dB was attained with a 400-Mb/s FSK (frequency-shift keyed) single-filter detection system. Throughout a 25-h 183-km transmission experiment, the stable operation of this receiver was confirmed. >

Sensing system using optical fibers

Abstract: A sensing system using optical fibers having loss characteristics subject to variations of a signal light wave as a pumping light wave with a wavelength different from that of a pumping light wave is coupled into said optical fiber. Unlike conventional OTDRs that utilizes a light back scattering in an optical fiber, a sensing system using optical fibers according to the invention utilizes the light passing through an optical fiber as a detected signal in order to enhance the efficiency and effectiveness of the system and, therefore, it has a significantly improved S/N ratio and a dynamic range of measurement as compared with conventional OTDRs. Moreover, continuous light may be used for the signal light wave (detected signal) to increase the rate of light emission for detection and to reduce the time required for measurement.

A 32/24 bit digital audio signal processor

Abstract: A digital signal processor of novel architecture developed for high-performance audio applications and realizing a new level of parallelism and dynamic range is presented. The chip, featuring 32-b*24-b multiplier/accumulator and 80-ns cycle time, is fabricated using 1.2- mu m CMOS double-level metal technology. The performance of audio signal processing is efficiently increased by parallel operation of (calculations and data transfers) and by the configuration of the arithmetic logic unit and the MAC (multiplier and accumulator). The MAC gives sufficient dynamic range for high-precision audio signal processing. Two 24*256 words of data RAMs enable users to execute over 500 taps of FIR (finite impulse response) filtering with one processor. The cascade configuration of the processors enables users to execute very long taps of FIR filtering. >

Predictive coding device

Abstract: A predictive coding device includes: a limiter to limit an input value having a first dynamic range to a value within a second dynamic range narrower than the first dynamic range; a subtracter to calculate a differential value between an output value of the limiter and a predictive value; a quantization circuit to assign the same code to differential values which differ by a value which is equal to or larger than the second dynamic range and smaller than the first dynamic range; and a predictor to calculate a new predictive value by using an output of the quantization circuit. The quality of the code due to the limitation of the dynamic range is improved.

Trench CCD image sensor

Abstract: The authors describe and present simulation data on the device structure, process flow, and operation of the Trench CCD (charge coupled device), which is being developed to increase the resolution of solid-state image sensors. The device provides larger dynamic range, higher sensitivity, and no image lag together with great packing density. A charge transfer channel formed around a trench eliminates the problem of insufficient dynamic range, which restricts the resolution. Because the Trench CCD occupies a small percentage of the total pixel area, the aperture area is increased, leading to improved sensitivity. Trench fabrication technology is used in dynamic RAM production; hence, further refinements can be expected to enable improvement of CCD image sensor performance parameters other than dynamic range. These features allow the development of a Trench CCD with 2 million pixels for 2/3-in and smaller optical systems, bringing a practical consumer HDTV (high-definition TV) camera closer to reality. >

3000 In Ga As Photodiode Multiplexed Linear Array For The Spot 4 S.W.I.R. Channel

Abstract: SPOT 4 will be an improved version of the SPOT 1,2 and 3 earth remonte sensing satellites ; a SWIR channel is added for agriculture monitoring, and the lifetime is entended to 4 years. The SWIR sensor was designed to be fully compatible with the visible and near IR silicon CCD : - the 3000 30 μm x 30 μm pixels can be registred to the visible detectors with an accuracy better than =/= 2 μm ; - the radiometric performance (uniformity of response, dynamic range, linearity,...) is imilar to that of the visible-channel CCD ; - the operating temperature is + 5°C. The 3000-pixel sensor consists of an ultra-precise assembly of ten elementary modules comprising 300 InGaAs photodiodes and two associated CCD multiplexers on both side. One single pixel is destroyed at the splice between two adjacent modules; The ten modules are read out in sequence. The reading sequence last 3 ms. Quantum efficiency of the photodiodes is typically 65%. Noise equivalent power is 10-13 W. A dynamic range of better than 4000 is obtained at the output of the multiplexer. The histogram of output noise voltages will be presented. A map of the relative sensitivity along the array will be displayed. The cut--off wave-length depends on the In/Ga ratio in the active layer, and the operating temperature. It is 1.690 0.005 μm at +5°C. Several detectors are presently undergoing re liability tests ; no significant alteration in performance has been noticed after aging at 125°C (operating).