Showing papers on "High dynamic range published in 1994"

Optical carrier filtering for high dynamic range fibre optic links

Abstract: Optical carrier filtering is used with an externally modulated fibre optic link to maintain high dynamic range operation with significantly reduced optical power levels. A spur-free dynamic range of 115 dBHz/sup 2/3/ is achieved for a frequency of 17 GHz with a received optical power of only 1.5 mA. An external filter is used to demonstrate a 10 dB improvement in dynamic range for a fixed optical power level.

High dynamic range digitizer

Abstract: A digitizer suitable for digitizing input signals having a high dynamic range. The digitizer is microprocessor controlled and comprises an input stage, a multi-channel attenuator or amplifier bank, a multiplexer and a analog-to-digital (A/D) converter. The function of the multi-channel bank is to move the input signal within the range of the A/D converter. The input signal to be digitized is fed through the input stage to each of the channels in the attenuator bank. The signal is scaled by each respective channel in the attenuator bank. The multiplexer is used to switch the scaled signal which is within the range of the A/D converter for digitizing. The digitized sample is then corrected according to the attenuation or gain factor of the scaled channel. The digitizer includes a comparator bank which is used to determine the channel with the widest signal range within the range of the A/D converter. The digitizer also includes a channel calibrator for calibrating the actual gain or attenuation of each channel. In another aspect, the digitizer can be implemented using an optical front-end comprising an optical beam splitter, optical attenuators and amplifier banks. The optical front-end provides improved noise immunity and faster speed of operation.

A class of binary FSK direct conversion receivers

Abstract: Receivers of low power consumption and high dynamic range of typically 60 to 100 dB are key elements in wireless communication systems. This paper deals with a class of direct conversion receivers for binary FSK, involving the class of quotient detectors and an AGC circuit. The members of the class of quotient detectors are circuits of low complexity and do not contain components with excessive power consumption, as e.g. high-speed high-resolution ADCs. Analytical and experimental investigations show the capability of the class of quotient detectors for GMSK signals. So far, for one member of the quotient detectors an inherent dynamic range of 47 dB at a BER of 10/sup -3/ has been achieved. The proposed AGC is realized as a slow low-power ADC, based on a base-band switchable gain amplifier and a two bit power level detector that keeps the mean power level at the detector input within a 12 dB interval. Furthermore, the AGC circuit yields a signal strength information with the received signal resolution of 6 dB. Due to low power consumption, low complexity, and high dynamic range, the proposed class of receiver is well suited for wireless and cordless communication systems such as GSM or DECT. >

High-power microwave photodiode for high-dynamic-range analog transmission

Abstract: For efficient operation, photodiodes have been the predominant choice as photodelectors in fiber-optic microwave-transmission applications. Mesa structures have been operated at frequencies as high as 30 GHz (see Ref. 1), and edge-illuminated and waveguide structures have operated at even higher frequencies.2 Also important to high-fidelity link performance is the level of received photocurrent, with values of 5- 10 mA and above being desirable for many applications. However, little has been reported in the literature about the power-handling capabilities of such photodiodes, which can be expected to be limited because of their small size. Such power limitations can significantly impair the performance of a fiber link, particularly with regard to dynamic range, noise figure, and link loss.

High dynamic range laser diode direct modulation

Abstract: A high dynamic range laser diode modulation scheme employs two laser diodes connected so that their outputs are added in a single optical fiber. The first diode is modulated over its dynamic range. The second diode is also modulated over its dynamic range, and is attenuated with a filter to provide fine level adjustment to the coarse levels provided by the first diode.

Loss measurement in high voltage thyristor valves

Abstract: No measuring method is presently available for direct and sufficiently accurate evaluation of power losses in thyristor valves used in HVDC converter substations and static VAr controllers. This paper presents a measuring method to be be used during the valve type tests with the intention to verify the guaranteed loss characteristic. The method was validated under laboratory conditions by comparison to a sophisticated calorimetric technique. An uncertainty of 1% was achieved at conditions simulating full load operation. Voltage across and current through the valve are recorded in discrete steps and digitized. The loss is then calculated as their product. Special current and voltage sensors were developed to cover a very high dynamic range of the measured quantities. A high resolution, multichannel digital recorder was used for simultaneous registration of two voltage and two current signals. The method is of a general application, since the valve is treated as a two port circuit. Therefore, it can be used to measure loss in other nonlinear components and apparatus, where large dynamic changes of the measured quantities preclude application of conventional techniques. >

Bidirectional reflectance distribution function (BRDF) sensing with fiber optics, programmable laser diodes, and high-resolution CCD arrays

Abstract: This paper reports on (1) the development of a fully optoelectronic BRDF sensor, and (2) first experimental results obtained with an automated setup consisting of the sensor, stages for specimen scanning, as well as PC hard- and software for the control of the setup and the evaluation of data. Main points covered are the construction of the sensor head, problems with the alignment of the hundreds of fibers needed, how to reach the necessary high dynamic range of the CCD camera employed, and the control of the laser diode.

High-frame-rate image acquisition system

Abstract: A compact and fully integrated, high-frame-rate and high-resoluuon digital image acquisitionand analysis system has been developed. The system integrates highspeed data acquisition, imageplayback, image processing, and motion analysis features. The imaging device, a multiport, split-frame-transfer, backside-illuminated charge-coupled device (CCD) imager developed by the ArmyResearch Laboratory (ARL) and the David Sarnoff Research Center, enables system operation at upto 500 frames per second. The system design is described and CCD performance results are given.Keywords: image processing, electronic imaging, charge-coupled device 1. INTRODUCTIONOptical signal-processing systems and certain imaging applications require photodetectorarrays with high dynamic range and fast frame-rate capabifities. As part of an API program foroptical signal-pmcessing systems, 512 x 512 and 1024 x 1024 pixel multiport imagers were developed. The designs focused on readout structures to maximize speed and reduce noise, improveimager resolution through crosstalk reduction and increased fill-factor, and maximize dynamic range

Trading off speed versus dynamic range in switched current circuits

Abstract: This paper describes the theoretical basis for a design methodology which enables control of the fundamental tradeoff between speed, dynamic range, and power consumption in switched current cells. The presented methods are applied to the design of a very high dynamic range current memory cell and simulation results are given. >

Measurement of Nonlinearity in High-resolution Sigma-Delta Converters

Abstract: Sigma-delta conversion techniques are now common in high-resolution analog-to-digital (AD) and digital-to-analog (DA) converter design, and are capable of achieving high dynamic range with low distortion. One of the biggest problems in evaluating the performance of such converters is in measuring nonlinear errors at either the design stage (by simulation) or in physical realisations. This paper reviews techniques commonly used to evaluate performance, such as sinewave testing and dc-level sweeps, and presents a new technique for measuring nonlinearity using maximum-length sequence (pseudo-random noise) stimuli. Maximum-length-sequence (MLS)-based distortion measurements are possible because of the separation of linear and nonlinear signal components that occurs under MLS cross correlation, and possess some unique and desirable properties.

New camera for high-speed, high-dynamic-range digital imaging at 4,000 frames/second (burst rate) and 14-16 bits/pixel

Abstract: A novel combination of techniques with a proprietary masked CCD allows economical commercial realization of a fast framing camera which can acquire images at 4,000 frames per second while maintaining the low readout noise of a slow scan scientific grade CCD system. A 16 bit gray scale dynamic range has been achieved in production with this system and even higher dynamic ranges appear possible in the near future with this technique. This imaging system can also be combined with a gated image intensifier to provide shutter times in the nanosecond domain.

A high precision ADC system for instrumentation

Abstract: Pulse Density Modulation and especially Sigma Delta techniques are employed preferably for a wide range of applications. No trimming is required and no complicated calibration circuitry has to be implemented. This type of converters provide low cost and reasonably small silicon area is utilized. Although there are limitations in multiplexing and control loop applications, Pulse Density Modulation is the most common principle for low and medium speed converters. Recently, a variety of high performance Sigma Delta ADCs have been developed in the field of instrumentation. An optimized combination of Pulse Width and Pulse Density Modulation has been used for an ADC to obtain an excellent linearity and very high dynamic range. This principle has been employed for an ADC that occupies an area of 17 mm2 with pads including two independent modulators, digital filtering, serial interface, oscillator and other functional blocks. At a power dissipation of 6 mW it is suitable for battery supply. Its extremely good linearity, offset and offset drift performance as well as a very low input bias current offer a wide range of applications. The difficult task of testing high precision ADCs has been of great concern. For Pulse Density Modulators the differential linearity is inherently good. Therefore an incremental technique can be employed to measure the transfer characteristic at 21 bit accuracy, using only standard elements. This technique has been successfully used and is referred to in detail.

High dynamic range swept time delay crosscorrelator

Abstract: Analysis and theoretical results of a novel high dynamic range swept time delay crosscorrelator are presented. It is shown that, subject to the form of the post-multiplier filter employed, code self-noise is negligible and the dynamic range of the system is independent of the code length.

A low-noise BiCMOS amplifier channel for telecommunications

Abstract: A low-noise low-pass amplifier channel designed for telecommunications is described. The channel has an 80-kHz corner frequency and total dynamic range of 94 dB. To achieve the high dynamic range, the amplifier channel is constructed with a BiCMOS process and a relative high supply voltage of ±8V is used. To further increase the dynamic range, the baseband amplifier has two branches, a low gain (A = 29 dB) and a high gain (A = 73 dB) branch, comprising a common continuous-time preamplifier and separate antialias filters, switchedcapacitor filters, and postamplifiers. Differential signal processing is used to reduce the effect of common-mode disturbances.

Low‐noise gaas MESFET optimization using an orthogonal array approach

Abstract: This article presents an experimental optimization of the noise figure of small-signal self-aligned FETs. An L18 orthogonal array has been used to find the main effects of specific device parameters on noise performance at 18 GHz. This knowledge has been used to find an alternative device which shows a ∼0.7-dB improvement in noise measure without requiring major process changes. Hybrid low-noise amplifiers built with the improved FETs confirm the noise performance and show record power performance for high dynamic range applications. © 1994 John Wiley & Sons, Inc.

20 GHz Bandwidth High Dynamic Range 1.3 μm Buried Heterostructure Laser Modules

Abstract: A 20 GHz bandwidth 1.3 μ InGaAsP/InP Straight-Wall Mass-transport Buried Heterostructure laser diode was developed to operate in a microwave fiber optic link. When used in a microwave link, the laser has a typical RF insertion loss of 37 dB, an equivalent input noise density less than -115 dBm/Hz, a 1 dB compression dynamic range greater than 138 dB.Hz and a spurious signal free dynamic range of 97 dB.Hz 2/3 . The wide bandwidth, high dynamic range and low-noise of the laser module were obtained through the design of the package, the subcarrier and the laser chip

Role of optical amplifiers in high-dynamic-range analog links

Abstract: Analog AM photonic links are used in many applications such as cable TV and microwave links in phased arrays. The major issues of these links are linear dynamic range and rf efficiency. We will show in this paper that, while the rf efficiency is always increased by the optical amplifiers, the linear dynamic range may be significantly reduced. The effect of the optical amplifier on the signal to noise ration can always be expressed as a laser source with an equivalent RIN noise. The signal to noise ratio is affected less when the amplifier is placed closer to the source.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.