Showing papers on "Dynamic range published in 1977"

Closed loop companding ratio control for continuously variable slope delta modulation

Abstract: A monolithic integrated circuit encoder/decoder capable of converting an analog signal to a digital signal and capable of reconstructing an analog signal from a digital signal employing continuously variable slope delta modulation. The dynamic range of the continuous variable slope delta modulation is increased by employing means for providing a companding ratio reference coupled to a means for comparing the companding ratio reference against a filtered coincidence output from the encoder/decoder and then amplifying any difference therebetween. The difference is used to control the gain of the continuously variable slope delta modulator and can be used to modify the companding ratio reference to provide a closed-loop controlled companding ratio for the encoder/decoder.

Design and characterization of a real-time correlator

Abstract: The design and characterization of a real-time correlator/electrically programmable transversal filter is presented, based on a novel functional multiplying structure in a standard single-level MOS LSI process. The analog information is sampled and held at fixed sites on the chip and the tap weights slide past them; the taps are digitized into 7 bits which control the selection of seven binary area-ratioed MOS capacitors per tap position. The rotation of the tap weights can reduce the effect of tap-weight errors but contributes to fixed pattern noise. Experiments using cascaded chips to build longer filters show excellent transfer-function agreement with theory. Dynamic range of the device is limited primarily by fixed pattern noise. This problem has been modeled and at present about a 45-dB dynamic range has been obtained for the heaviest doped chips when driven by input-signal amplitudes which allow better than 1-percent harmonic distortion. With improvements suggested, significant increases are expected in the dynamic range of the device.

Development of a superconducting ELF receiving antenna

Abstract: The development of an extremely low frequency (ELF) submarine receiving antenna that uses a triaxial array of superconducting quantum interference devices (SQUIDs) has addressed the following six problem areas: 1) achievement of a SQUID sensor with a sensitivity of 10^{-14} T-Hz-1/2; 2) acheivement of a SQUID linear dynamic range of 140 dB; 3) achievement of sensor orthogonality of 10^{-4} rad;4) stabilization of receiver platform motion to 10^{3} rad; 5) processing of SQUID outputs in order to remove residual motion noise;6) provision of a suitable cryogenic environment. The required sensitivity, approximate linear dynamic range, and sensor orthogonality were successfully obtained in a prototype point-contract type triaxial SQUID magnetometer. This magnetometer was used to detect the ELF signal broadcast from the U.S. Navy transmitter in Wisconsin, both in the atmosphere above the water surface and at a depth of 100 m below the ocean surface in a stationary configuration. No measurements have been made as yet with the magnetometer in a towed buoy. Achievement of the platform motion requirement was demonstrated by motion spectrum measurements on a hydrodynamically stabilized buoy designed to be towed by a submarine. Motion excursions within the ELF pass band of 30- 130 Hz were found to be about 10^{-4} rad. This amount of motion requires that motion-generated noise be further reduced by more than 80 dB. The required noise rejection can be achieved by adaptive determination of a vector that is approximately equal to the earth's magnetic field vector. When the adaptive vector is evaluated and combined vectorially with the SQUID outputs, a quantity proportional to the ELF signal vector results in which motion noise is suppressed. This adaptive processing has been studied using a computer simulation of the SQUIDs' motion noise derived from towed-buoy motion data. The feasibility of cooling the SQUID sensors with liquid helium was demonstrated by a prototype long-hold-time dewar of a size capable of fitting a towed communications buoy. The dewar successfully maintained the temperature of a volume sufficiently large to hold a triaxial SQUID sensor package at the temperature of boiling liquid helium for a duration of 102 days.

Forward locking infrared video processing system having a scene dynamic range expander

Abstract: A means for expanding the dynamic range of a forward looking infrared (FL video processing system by inserting an automatic low frequency gain limiting and first post amplifier circuit means at the output of the preamplifiers in each video channel to provide variable pedestal limiting of the low frequency components of the video signal The automatic low frequency gain limiting and first post amplifier circuit means compresses the pedestal of signals derived from smoke, dust, or fire to arbitrary small levels to preserve sufficient dynamic range for enhancing the high frequency detail signal riding on the pedestals at a display

Dynamic Range And Spatial Resolution Of Picosecond Streak Cameras

Abstract: We have investigated the characteristics of a number of different streak cameras (IMACON600, IMACON675,and Electrophotonics cameras). With the exception of image converter tubes of very poor quantum efficiency,all cameras show a similar intensity- dependent time resolution. We define a useful dynamic range as thatrange over which tolerable pulse broadening is observed. This useful dynamic range varies with intensityfrom 5 for lOpsec pulses to 50 for 100psec pulses. At the same time no appreciable degradation of thespatial resolution is observed. Our results indicate that the pulse broadening mechanisms occur at thesurface or inside the photocathode material.Fast streak camera records are currently a widely used and relied -upon tool for the diagnostics ofshort laser pulses. However, considerable problems are frequently encountered when quantitative data are collected. These problems are directly related to the useful dynamic range of the streak camera. The useful dynamic range is defined as that range of input light intensities over which negligible or tolerabledistortion of the temporal pulse shape is observed. This range is also directly related to the temporalresolution of the camera.We present data taken with several types of cameras (IMACON600, IMACON675, and Electrophotonics).

Compander system having limiter in compressor and expander

Abstract: A noise reduction system having an encoder which compresses the dynamic range of an analog audio signal, a transmission medium coupled to the encoder, and a decoder coupled to the transmission medium for expanding and thereby restoring the dynamic range of the compressed analog audio signal. The encoder includes a voltage controlled amplifier (VCA) receiving the audio signal, a high-pass filter also coupled to the analog audio signal, a circuit for obtaining a difference between the outputs of the VCA and the high-pass filter, weighting and level sensing circuits coupled to the encoder output for sensing the level of the compressed analog audio signal, and a limiter circuit coupled to the output of the weighting and level sensing circuits and producing a control voltage applied to the VCA control input in such a manner that the ratio of the gain of the VCA and the gain of the high-pass filter at the pass band thereof does not become less than one. The decoder includes circuits similar to those of the encoder and exhibits a transfer function substantially inverse to the encoder transfer function, with the controlling voltage applied to the decoder VCA such that the loop gain in the pass band of the high-pass filter does not become more than one.

Precise wide-dynamic range constant current ratio circuits

Abstract: A method of compensation of unequal V BE 's in a conventional constant current ratio circuit is proposed, which improves the accuracy and the dynamic range of the current ratio considerably, without the need to use any higher resistance than normally desirable for integrated circuits. The linearity of the current ratio is better than 1 percent over a dynamic range of greater than four orders of magnitude.

Dynamic Range Of Picosecond Image Converter Streak Cameras

Abstract: The variation of dynamic range of a picosecond image converter camera is analysed in terms of its time resolution. It is observed that the dynamic range is proportional to the square of the resolved time. This phenomenon is explained in terms of a photo-electron emission "life-time" which is proportional to the intensity of the photon beam absorbed by the photocathode of the time resolving image converter tube. The implications of this mechanism on the interpretation of picosecond camera results are discussed.

Method of measuring equivalent noise levels

Abstract: PURPOSE:To compose a numerical chart for antilogarithms by the use of a code converter and measure equivalent noise levels by the use of the chart, thereby considerbly reducing processing time and enabling the sufficient assurance of dynamic range.

Crystal Streak Camera

Abstract: A high speed optical deflection system has been designed for picosecond laser pulse diagnostics. Evaluation of a prototype system indicates that an ultracompact streak camera with picosecond resolution can be constructed from readily available components with a relatively low cost. A commercially available electro-optic beam deflector with a 2-mm aperture ADP crystal is used in the prototype. This unit is capable of deflecting wavelengths from the visible to 1.06 pm. When high power single picosecond pulses are used, previous limitations of electro-optic deflectors due to signal beam absorption, internal heating, and mechanical shock waves are overcome. At 532 nm, a resolution of 18 spot diameters is obtained, while the dynamic range in excess of 200 is limited by the readout system. Use of a crystal material with a much higher electro-optic coefficient produces a theoretical resolution c,omparable to that of electro-optic cameras. The high current required to drive the crystal presents some difficult electronics problems and available solutions are discussed. Readout is accomplished with film, a TV camera, or a linear diode array. Computer manipulation of the output data can be used to improve resolution and dynamic range.

Large-time-bandwidth-product correlation and holographic storage with an s.a.w. storage correlator

Abstract: High-resolution (375 Hz) spectrum analysis has been performed by correlating long signals during the read-in process. In a ZnO-on-Si storage correlator a new holographic storage technique is demonstrated to achieve chirp compression with large compression ratio (?8000) and improved dynamic range.

Amplifier for short, amplitude variable gaussian pulses - has class=B input transistor amplifier and double gate MOSFET output amplifier giving compression at top of dynamic range

Abstract: Gaussian pulses in the nanosecond range whose amplitude can vary from pulse to pulse within a certain dynamic range, are amplified almost without distortion by the amplifier. A B-class transistor a.c. amplifier stage is provided as input amplifier. It is followed by an amplifying stage with a double gate MOS field-effect transistor as output amplifier. The input amplifier output is connected to one gate, while the other gate is connected to a fixed bias voltage. The working point of the output amplifier is such, that when pulse amplitudes are at the top of the dynamic range, a very little widening of the pulses occurs, and the amplitude is compressed, but pulse peaks are not flattened by limiting processes.

Wideband Acousto-Optic Radiometry

Abstract: The technique of acousto-optic spectrum analysis can be used to improve the signal to noise of r.f. signals by the noncoherent integration of photoelectrons in a properly configured optical sensor. The requirements placed upon the sensor and acousto-optic device to obtain a given processing gain, resolution, analysis bandwidth, and dynamic range are discussed for bulk optical devices.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Ultraasonic delay circuit

Abstract: PURPOSE:To provide a circuit system wherein a dynamic range of a wide band amplifier for delay line driving in a delay line system is economized, but S/N ratio is superior

A Low-Noise High-Output Capacitor Microphone System

Abstract: INTRODUCTION: Now that we have an audio signal ing the microphone for a line level output of 20 dBm into processing system [1] capable of extending the dynamic 600 ohms, cable noise pickup has been rendered insigrange of a studio tape machine to 110 dB, the.previously nificant, and the need for a low level console preamplifier adequate noise levels of studio consoles and microphones with its attendant noise has been eliminated. have become too high. The extended dynamic range Many recording studios use a wide variety of micapacitor microphone system to be described is designed crophone types in a single recording session because the to solve this noise problem and, at the same time, increase sounds of certain microphones are considered optimum for the maximum acoustic input capability, the sound sources with which they are used. In the In recording, noise is most apparent in a multitrack author's recording system the same wide dynamic, range mixdown and when microphones are picking up at a microphone serves all purposes. In this case the sound is distance. The noise levels of today's high-quality changed by means of an extremely flexible wide dynamic capacitor microphone systems are in the range of 20-30 range program equalizer described in an earlier paper [2]. dB sound pressure level. Although this noise may be Directional patterns can be selected by using either somewhat comparable with the noise of a well constructed pattern-switchable capsules providing either two or three studio, the room noise does not mask the microphone directional patterns or by separate capsules having the noise because room noise occurs primarily at low frequen_ desired directional patterns. Sufficient gain for close, cies and the audible microphone noise is a hiss at high medium, or distant miking is attained by means of a gain frequencies, switch on the microphone itself which provides 20 dBm In this new microphone system the noise level has been: output for sound pressure level inputs of 140, 125, or 110 extended downward to 15 dB sound pressure level dB, respectively. A-weighted. Its maximum input signal has been extended The following sections will describe the sources of upward to 140 dB sound pressure level without taking the noise, how the electronic system is designed, and its microphone apart and adding a capacitive pad. By designperformance characteristics.

Cooled And Intensified Array Detectors For Optical Spectroscopy

Abstract: Recent advances in thermoelectric cooler, fiber optic, and image intensifier technology have been combined with advanced solid state optical detectors to produce high sensitivity, extremely wide dynamic range detectors for applications in optical spectral measurement Spectral data from detectors is digitized and signal averaged for higher precision, then recorded under computer control for advanced data reduction A general comparison of TN-1223 series array detectors to vidicons is made, with sensitivity and dynamic range advantages of the array detectors described

Methods And Results Of Dynamic Range Testing Of Diagnostic Ultrasound Instrumentation

Abstract: The technological advance of gray scale imaging has been a major factor in the rapid growth of the clinical application of diagnostic ultrasound. Gray scale imaging implies that the displayed brightness of a target in the ultrasound image is a function of the amplitude of its echo. Several techniques have been investigated for the measurement of the dynamic range of gray scale ultrasound scanners. The measurement methods include (1) an electronic pulse burst generator which emits a sequence of pulses decaying at a selectable rate of 0, 1.25 or 2.5 dB/cm, (2) a polypropanol wedge designed to attenuate acoustic echoes over a range of 0 to 60 dB, (3) a series of stainless steel reflectors varying in angle from 0 to 10° so that returning echoes vary over a 40 dB range. All three instruments are easy to use. However, the wedge and variable angle devices must be calibrated for use with individual transducers. The electronic test device excludes the transducer when testing system dynamic range. Therefore, the pulse burst generator seems to be the most suitable for clinical or survey applications at this time.

Impatt vibrator for superhigh frequency meter

Abstract: PURPOSE:To remove the higher harmonics more than 3/2 times of that of the IMPATT vibrator to be used for the indicator of micro wave and milli wave bands and to enalarge the indication accuracy and to indicate dynamic range.

A 7GHz Band GaAs FET Amplifier for the Straight-Through-Repeater

Abstract: A 7GHz band GaAs FET amplifier for the straight-through-repeater has been developed. The amplifier has six single-ended stages, a 40dB linear gain, a 4 to 4.5dB noise figure and 17dBm saturated output power over a frequency range of 6.5 to 6.9GHz. The power consumption is lW maximum. Distortion for FM transmission is sufficiently low over a wide dynamic range up to saturation, so the repeater needs no additional AGC circuit for output limitting. 960 telephone channel FM Transmission noise loading test results show distortion to be less than 10pWOp up to saturation. For two FM/ FDM carrier transmission, the distortion is nearly the same as single carrier up to the 1dB compression point.

Better Utilization of SAR Dynamic Range

Abstract: Three general classes of image enhancement techniques for synthetic aperture radar (SAR) video were investigated through non-real-time computer simulation. The general categories were 1) monochromatic adaptive gray shade transformations, 2) pseudocolor encoding, and 3) feature analytic methods. The class of feature analytic techniques was found to have the greatest potential for improving the operational utility of SAR imagery.

A unified acquisition system for acoustic data

Abstract: A multichannel, acoustic AM carrier system was developed for a wide variety of applications, particularly for aircraft noise and sonic boom measurements. Each data acquisition channel consists of a condenser microphone, an acoustic signal converter, and a Zero Drive amplifier, along with peripheral supporting equipment. A control network insures continuous optimal tuning of the converter and permits remote calibration of the condenser microphone. With a 12.70-mm (1/2-in.) condenser microphone, the converter/Zero Drive amplifier combination has a frequency response from 0 Hz to 20 kHz (-3 db), a dynamic range exceeding 70 db, and a minimum noise floor of 50 db ref. 20 micro Pa) in the band 22.4 Hz to 22.4 kHz. The system requires no external impedance matching networks and is insensitive to cable length, at least up to 900 m (3,000 ft). System gain varies only + or - 1 db over the temperature range 4 to 54 C (40 to 130 F). Adapters are available to accommodate 23.77-mm (1-in.) and 6.35-mm (1/4-in.) microphones and to provide 30-db attenuation. A field test to obtain the acoustical time history of a helicopter flyover proved successful.