Showing papers on "Dynamic range published in 1983"

Direct rotation-rate detection with a fibre-optic gyro by using digital data processing

Abstract: By using digital processing, the dynamic range of gyros with direct rotation-rate detection is no longer restricted. The linearity error is less than ±1% within a rotation range of 300 to 200000/h.

A low noise SIS array receiver for radioastronomical applications in the 35 50 GHz band

Abstract: Arrays of six superconducting tunnel junctions have been used in a heterodyne receiver over the frequency range 35–50 GHz. The mixer array and a 3.7–4.2 GHz parametric amplifier used as the if amplifier are immersed in liquid helium and operated at 2 K. The high if allows single sideband operation with a system noise temperature varying rather smoothly from 220 K at 35 GHz to 140 K at 50 GHz. Mixer noise temperatures between 11 and 21 K were measured over the band indicating that the use of arrays to enhance the dynamic range does not seriously affect the mixer noise performance in this frequency range. The receiver is used for radio astronomical observations in the Onsala 20 m telescope in Sweden.

A Multi-Octave Frequency Selective Limiter

Abstract: A frequency selective limiter operating over more than 2 octaves bandwidth has been developed. The design uses single crystal ephaxial YIG films. Limiting threshold and leakage are about 1 milliwatt. Dynamic range approaches 20 dB. Selectivhy bandwidth for 3 dB weak signal compression is about +- 20 MHz at 100 mW input. An analytical method gives accurate predictions of limiting behavior when linear loss terms are included.

Response Of Fiber Gyros To Signals Introduced At The Second Harmonic Of The Bias Modulation Frequency

Abstract: A technique that can be used for the closed-loop operation of dynamically biased optical fiber gyroscopes is discussed. The source wavelength dependence of the scale factor is considerably suppressed and the dynamic range of this system is limited only by that of the phase modulator used. Preliminary experimental results using an all-fiber gyroscope are compared with theoretical predictions.

Self-calibration of stacked beam radar

Abstract: An apparatus and method for calibrating the output signal of a receiver having amplification over a predetermined input signal amplitude range has been described incorporating means for generating a sequence of reference signals each having a predetermined amplitude, means for coupling the sequence of reference signals to the input of the receiver, means for sensing the output reference signals of the receiver, means for storing output reference signals indicative of the amplitude along with corresponding input reference signals to provide a table of receiver input and output signals over the dynamic range such as 70 dB of the receiver. Unknown input signals are calibrated by looking up and comparing the amplitude of the output received signals of the receiver with stored output reference signals in the table and selecting the corresponding known input signals previously provided by the calibration signals. The invention overcomes the problem of accuracy and stability in the gain of the receiver over a wide dynamic range, such as 70 dB, and for non-uniform amplitude gain between a plurality of receiver channels.

Spectral Structure Of Phase-Induced Intensity Noise In Recirculating Delay Lines

Abstract: The dynamic range of fiber optic signal processors driven by relatively incoherent multimode semiconductor lasers is shown to be severely limited by laser phase-induced noise. It is experimentally demonstrated that while the noise power spectrum of differential length fiber filters is approximately flat, processors with recirculating loops exhibit noise with a periodically structured power spectrum with notches at zero frequency as well as at all other multiples of 1/(loop delay). The experimental results are aug-mented by a theoretical analysis.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Arrangement for the expansion of the dynamic range of optical devices

Abstract: Light intensity levels are measured at various locations in a scene and light amplified and/or attenuated by a device interposed between the source of light and the light-sensitive surface having a limited dynamic range. By attenuating bright regions and/or amplifying weak regions, the dynamic range of light intensities of the scene is reduced, thus enabling the limited dynamic range device to be used with scenes having a larger light intensity dynamic range. In applying the method to the receiving side of a 3-D measurement system employing projected light, a simpler system results and problems associated with modifying the high energy projected light are avoided. Also, a greater range of measured object surface reflectance is accommodated.

Fourier transformation using an electroabsorptive CCD spatial light modulator

Abstract: The use of a GaAs CCD as a spatial light modulator is described and its application to coherent optical Fourier transformation is analyzed. In this device, the transmission through the two-dimensional buried-channel CCD may be electroabsorption modulated near the GaAs cutoff wavelength since the electric field in each storage well is controlled by the transferred charge. One of the primary advantages of this modulator is the ability to electrically address the device at high speed. Analysis of the two-dimensional modulator with a silicon CCD detector array yields a projected dynamic range approximately equal to the number of modulator array elements. For arrays containing greater than 1000 elements, detector performance and nonuniformities can limit the maximum range to 30-40 dB. The device can also be optically addressed, and in this mode of operation it has a comparable dynamic range to the electrically addressed structure with an optical write energy an order of magnitude lower than liquid crystal or photorefractive light valves. An alternative mode of device operation is a waveguide mode in which the light propagates along an epitaxial layer and is modulated as it passes under a one-dimensional CCD. The detection is done by a second linear CCD. The higher modulation efficiency results in a dynamic range approximately one hundred times the number of elements but is again limited to 30-40 dB because of detector response and nonuniformities.

Computer simulation of low-frequency electromagnetic data acquisition

Abstract: Computer simulation of low‐frequency electromagnetic (EM) digital data acquisition in the presence of natural field noise demonstrates several important limitations and considerations. Without a remote reference noise removal scheme, it is difficult to obtain an adequate ratio of signal to noise below 0.1 Hz for frequency‐domain processing and below 0.3 Hz base frequency for time‐domain processing for a typical source‐receiver configuration. A digital high‐pass filter substantially facilitates rejection of natural field noise above these frequencies; however, at lower frequencies where much longer stacking times are required, it becomes ineffective. Use of a remote reference to subtract natural field noise extends these low‐frequency limits by one decade, but the remote reference technique is limited by the resolution and dynamic range of the instrumentation. Gathering data in short segments so that natural field drift can be offset for each segment allows a higher gain setting to minimize dynamic range p...

A CCD time-integrating correlator

Abstract: A CCD binary-analog time-integrating correlator has been designed and operated at 20 MHz clock rate. The 32-channel device is capable of integration periods in excess of 25 /spl mu/s or 500 clock periods, equivalent to a time-bandwidth product of 250. The device architecture is based on charge-domain signal processing for high-speed operation and does not required on-chip logic for storage of the binary reference. The device is tailored for weak signal applications, and a new charge skimming circuit has been devised which allows the small portion of the integrated charge containing the correlation function to be separated from the large register by tenfold. The correlator has a stationary pattern noise which can be eliminated with simple postprocessing, yielding a dynamic range of 67 dB.

A 360,000 pixel color image sensor for imaging photographic negatives

Abstract: We describe a 740(H) \times 242 (V) × 2 charge-coupled color image sensor for imaging photographic negatives. The sensor achieves charge capacity of 1 \times 10^{6} electrons per pixel, random noise of 300 rms electrons per pixel, and dynamic range of 70 dB. Sensor design, spectral sensitivity, charge capacity, and noise are discussed.

A Monolithic Audio Spectrum Analyzer

Abstract: A monolithic audio spectrum analyzer with 16 channels of bandpass filters, half-wave rectifiers, and postfiltering has been fabricated with double-poly NMOS technology. The chip was designed using switched-capacitor filter techniques. It performs a total of 84 poles of filtering and contains 100 operational amplifiers in an area of 225 X 280 mils. A system dynamic range of better than 43 dB, linearity of better than 1 percent, and center frequency accuracy of better than 1 percent have been achieved.

Low noise charge coupled imager circuit

Abstract: Noise reduction and dynamic range expansion in a CCD imager is achieved by combining a narrow FAT zero metering gate with a reference column substraction and CCD charge bailing.

A monolithic audio spectrum analyzer

Abstract: A monolithic audio spectrum analyzer with 16 channels of bandpass filters, half-wave rectifiers, and postfiltering has been fabricated with double-poly NMOS technology. The chip was designed using switched-capacitor filter techniques. It performs a total of 84 poles of filtering and contains 100 operational amplifiers in an area of 225 × 280 mils. A system dynamic range of better than 43 dB, linearity of better than 1 percent, and center frequency accuracy of better than 1 percent have been achieved.

A new polarographic flow-through detector

Abstract: The construction of a flow-through polarographic detector is described, based on introduction of the test solution into a space filled with mercury. Two variants of the detector have been developed, with the inlet jet placed vertically and horizontally. The dynamic properties of the two detector variants, the linear dynamic range and the response reproducibility were tested using o-nitrophenol as a model substance. The detector with the vertical jet has a wide linear dynamic range and that with the horizontal jet exhibits an extremely rapid response with a time constant of the order tenths of a second.

Signal conditioning circuit

Abstract: A signal conditioning circuit includes a logarithmic signal compression circuit for compressing wide dynamic range input signals to a dynamic range which is a predetermined portion of the dynamic range of an output utilization apparatus. There is provided, additionally, means for detecting the presence of the high level signals and superimposing a signal representative of the high level signals on the compressed signals to provide a combined output signal which, while compressed to the range of the output utilization apparatus, contains definable low level and high level signals from a wide dynamic range input signal.

Formulas for dynamic range evaluation of second-order discrete-time filters

Abstract: Formulas for evaluating the maximum magnitude of a second-order digital transfer function are given. These are especially useful for designing switched-capacitor (SC) filters with optimal dynamic range.

MAP detection and ML estimation of signals overlapping in time and frequency for both Gaussian and Laplacian noise

Abstract: The magnitude error function is the optimal criterion for detection and parameter estimation under Laplacian (double-sided exponential density) noise. Its use is compared to the commonly used squared error function (equivalent to the matched filter), derived under the condition of Gaussian (normal density) noise, and found to possess the following advantages: (1) The performance of the magnitude error detector is better than that of the squared error detector for signals with unknown delays in low-level noise and within overlappings; (2) The algorithms are simpler to implement on a digital processor and they run faster because no multiply operations are needed and because the dynamic range is suitable for a 16-bit arithmetic. The theory is developed for a detection and estimation scheme on nonlinear functions of non-random parameters. It is applied to a problem in electromyography (EMG), namely the problem of separating superpositions of finite-duration signals which overlap both in the time and frequency domains. For the sake of completeness it is shown that the amplitude density of the noise in EMG is Laplace distributed rather than Gaussian.

Noise cancelling system for low frequency analog recording

Abstract: The present disclosure describes an electronic system for use with low cost audio tape recorders whereby a substantially noise-free wide dynamic range is provided for the recording of analog signals in the DC to 30HZ frequency band. In achieving this result, the system utilizes two FM carrier oscillators having center frequencies displaced from each other and modulated respectively in opposite senses by the signal being recorded. The system also provides an additional utility channel of limited dynamic range for the concurrent recording of time markers, digital signals and the like.

Adaptive digitizer circuit for information processing system

Abstract: An adaptive digitizer circuit for an information processing system includes an entropy filter responsive to an information signal V having a variable noise σ V that is a function of V, for providing a transform signal T, having a constant transform noise level σ T throughout its dynamic range; and an analog to digital converter in which the ratio σ T /δ T of the noise level σ T of the transformed signal and the digitization interval δ T is constant throughout the dynamic range of T.

Optical direct analog-to-digital conversion for microphones.

Abstract: Acoustic pressure is directly converted to a parallel 3-bit binary code using optical interference. Since the diaphragm deforms sinusoidally when pressure is applied, the interference is different from point to point on the diaphragm. We simultaneously detected the interference intensity at an adequate sampling of three points. A quantized bit plane is produced in parallel without scanning. The dynamic range is ±240 Pa, and good linearity is obtained. This method can be used to measure other quantities such as temperature and voltage.

Method for automatic adaptation of the volume and dynamic range of electroacoustic signals to the noise level occurring at the listening location

Abstract: By means of a control circuit with a relatively short control time, the level of the radiated useful signal is adjusted so that it follows the sum of the levels of the noise and the original useful signal, whereby simultaneous volume adaptation and dynamic range compression of the useful signal depending on the noise level with minimal additional sound pressure imposed on the listener and minimal reduction in reproduction fidelity are achieved. The circuit arrangement according to the invention provides an amplifier with a control component as a control route in the transmission path of the useful signal, while the control parameter is derived from the difference between the sum of the input level and the mean noise level on the one hand and the output level on the other hand.

SQUID parametric amplifier

Abstract: The single junction SQUID was previously shown by analysis and simulation to be an attractive candidate for a parametric amplifier. Further calculations of the noise and saturation behavior of the nearly degenerate parametric amplifier have now been performed by numerical simulation. These simulations clearly show that the amplifier noise temperature will be approximately the device temperature T 0 , and that the amplifier will be completely saturated in the presence of white noise characteristic of 30T 0 . Signal saturation of the amplifier also occurs for an output power 10^{-2}F_{o}\phi_{o}^{2}/2L , strongly limiting the dynamic range, However, a coherent array of N single junction SQUIDs is shown to have a signal saturation level increased by N relative to a single SQUID, with no increase in noise temperature, resulting in an N-fold improvement in dynamic range.

Dynamic reflection range in the case of four-wave interaction in resonant media at the wavelength of 10.6 μ

Abstract: It was found experimentally that the dynamic reflection range was ~107 for a four-wave interaction in SF6 and BCl3 gases absorbing resonantly at 10.6 μ. In an optically dense nonlinear medium the power efficiency of reflection of a signal wave was independent of its intensity right up to the value comparable with the intensity of the first reference wave. On the side of low signal intensities the dynamic range was limited by the scattering of the reference waves on the windows of a gas cell.

High Frequency Acoustic Microscopy Using Pulse Compression

Abstract: The use of extended coded pulses gives rise to a compresssion processing gainandhence increased dynamic range in reflection acoustic microscopy. This is achieved without degrading the depth resolution. We have previously demonstrated the use of this technique at relatively low frequencies. At high frequencies and using large bandwidths one encounters a major difficulty which stems from the frequency dependent absorption in the coupling medium. For bandwidths of the order of 20% at frequencies over 500 MHz this can have a drastic effect. The problem has been investigated both by the use of approximate analytical as by numerical techniques. A SAW-based pulse compression microscope operating at a centre frequency of 750 MHz is described. 12 dB and the compressed pulse width is 8 ns which are both in good agreement with theoretical prediction. The observed processing gain is