Showing papers on "Dynamic range published in 1974"

A new technique of thermal RMS measurement

Abstract: A thermal technique of rms measurement is described which uses the base-emitter junction of a bipolar transistor to sense the temperature change of a monolithic chip due to the power dissipation of a companion diffused resistor. An analysis is presented which provides: 1) design equations for performing error compensation to minimize the nonlinearity of the rms-to-dc conversion, and 2) ac feedback network design to optimize the low frequency cutoff and settling time product. Resulting rms converters had midband accuracies of /spl plusmn/0.05 percent of full scale over a dynamic range of 30 dB, high frequency limits of 100 MHz for 2 percent accuracy, and settling times less than 1 s.

Digital Companding Techniques

Abstract: This paper deals with the requirements for the design of digital companding techniques in either delta or pulse-code modulation. Both delta and pulse-code modulation convert analogue signals into binary signals and in both these systems the dynamic range is normally small. By the use of companding, the dynamic range can be extended. Since both delta and pulse-code modulation are digital methods, they are well suited to the use of digital companding techniques. The binary transmitted signal normally contains a measure of the system performance. By observing certain patterns in this binary signal and using the occurrence or nonoccurrence of these patterns to change the gain of the modulator and demodulator, syllabic companding can be obtained. The selection of the binary pattern and the rate of change of gain of the modulator and demodulator, determines both the point at which the companding operates and the attack and decay times. The ratio of the largest to the smallest value of the gain determines the dynamic range. By the use of digital circuitry, the gain can be controlled with sufficient accuracy over a large dynamic range. The paper deals with the principles involved in selecting the binary patterns to control the gain of the modulator and as examples a delta modulation system and a pulse-code modulation system with companding ratios of 60 dB are discussed.

Circuits for modifying the dynamic range of an input signal

Abstract: The invention provides signal compressors, expanders and noise reduction systems. In the compressor, a linearly treated signal component has combined therewith in opposition a non-linearly treated signal component which is however linear with respect to dynamic range above a threshold. Below the threshold the nonlinearly treated component has a gain which falls as the signal level falls. The expander is complementary to the compressor; the two signal components combine additively. The compressors and expanders are useful in video, audio and other circuits for effecting noise reduction.

Chirped Fourier Spectroscopy. 1:Dynamic Range Improvement and Phase Correction

Abstract: Chirping is the deliberate dispersion of the frequencies in a signal to remove a strong central peak. In a Fourier spectrometer, chirping improves dynamic range. For typical applications, the improvement is equivalent to about 16 dB in SNR. A very large nonlinear phase correction is required, but this is shown to be surprisingly simple to achieve in practice.

Multichannel logarithmic RF level detector

Abstract: The invention is a logarithmic RF level detector which can be used to derive gain-weighting signals in an n-channel angle modulation diversity receiving system. The IF signals in the n-channel receiving system are sequentially gated into a single logarithmic IF amplifier which compresses the input signal dynamic range by a factor on the order of a hundred to one. The amplifier output signal is envelope detected and then gated back into the n-channels essentially simultaneously with the gating of the signals into the logarithmic amplifier. After being gated back into its channel each signal feeds a low-pass filter which passes only the low-pass, or zeroth order zone. The signals so derived may then be used to actuate a diversity combination operation.

Signal transmission system

Abstract: A signal transmission system including a variable filter to control the frequency response by means of a control signal based on the amplitude of the information signal. The variable filter is connected to an output circuit of an information signal amplifier and may feed the frequency-modified information signal to a system output terminal, if the system is to compress the dynamic range of the information signal by amplifying low amplitude signals more than high amplitude signals. Alternatively, the filter may feed the frequency-modified signal back to the input of the amplifier by way of connecting means, such as a switch, to expand the dynamic range. In the latter mode, the switch can simultaneously be used to connect a feedback element directly between the output and the input of the amplifier. The overall response of the transmission system in expanding the dynamic range of the signal is the converse of the response of the system in compressing the dynamic range.

Tandem audio dynamic range expander

Abstract: An audio signal which has been compressed at two different frequencies for recording is expanded to its initial characteristics for reproduction by means of a tandem expander wherein the incoming signal is divided into paths representing a mid band variable gain path and a high band variable gain path and the two variable gain paths are subtracted from the main signal to provide a signal expanded in dynamic range. The control voltage for the high band variable gain path is extracted from the incoming signal. The system is particularly useful in the demodulation of discreet four-channel records.

Wide dynamic range, low power, analog-to-digital receiver

Abstract: A low power, wide-dynamic-range, signal compressor is suitable for operat from batteries The compressor input is compatable with most sensors, resistive, capacitive or inductive and it is capable of compressing 150 db of input dynamic range into a 6 bit digital or 40 db analog signal The output from the compressor is single valued and satisfactory for driving standard telemetry equipment

Computer evaluation of gas chromatograms with wide dynamic range

Abstract: If the complete dynamic range of the flame ionisation detector (FID) amplifier signal is to be integrated during trace analysis, the computer used for this purpose must have an effective dynamic range of at least six decades. The detection limit for traces in the ppm range (parts per million), whilst the major component is simultaneosly integrated, is discussed using samples of pure styrene, propylene and vinyl chloride. The dynamic range can be increased by using minor components as internal markers, by a computer-controlled attenuator switch and by a splitter which produces an internal marker in the chromatogram. In this way, trace components around the ppm level can be determined with standard deviations of a few percent.

A Solid-State Converter for Measurement of Aircraft Noise and Sonic Boom

Abstract: A solid-state converter, used in a system of instrumentation for measuring aircraft noise and sonic boom, features a dualgate FET mixer and an output stage designed for compatibility with a zero drive amplifier of MB Electronics, Inc. With a half-inch condenser microphone the converter itself has an operating frequency range from dc-28 kHz (-3 dB), dynamic range of 72 dB, and noise floor of 50 dB in the band 22.4 Hz-22.4 kHz; the system requires no impedance matching networks and is insensitive to cable length up to at least 3000 ft.

Dynamic range modifying circuits utilizing variable negative resistance

Abstract: Dynamic range modifying circuits, namely compressors and expanders, are disclosed in which series connected circuits respond to current or voltage drive to provide voltage or current output. One circuit has characteristics which do not vary with dynamic range and contributes a component to the output having dynamic range linearity relative to the input. A second circuit has variable impedance characteristics and contributes a component which does not have dynamic range linearity relative to the input and which effects the dynamic range modification. Devices are described in which the variable impedance characteristics include effective negative resistance which is itself varied and is shunted by a variable reactance. Devices are also described in which the second circuit is a two terminal network which responds to the current between the two terminals to determine the voltage therebetween and wherein the voltage is derived either by way of a variable filter which acts to restrict the voltage or by way of multiple paths including filters and limiters.

A method of display dynamic range expansion using system gain wobbulation.

Abstract: The clinical relevance of the dynamic range of the display of two-dimensional ultrasonic scans is discussed. A method is described by which the effective dynamic range of the display may be expanded by relating the duration of the registration of the signal to the signal amplitude. This is achieved by wobbulation of the range of the swept gain control. The resulting improvement in the value of the display is illustrated by scans of a kidney made using a manually operated, direct contact scanner.

Gain-ranging analog or digital seismic system

Abstract: A wide-band, gain-ranging amplifier is described that may be used for recording data with a dynamic range of 60 db in each of three different levels, 12 db apart, so that we achieve an “effective” dynamic ±160-v analog or 84-db digital, within a normal ±10-v analog system. As described, the ranging circuit reduces the gain of the amplifier by a factor of either 4 or 16 whenever the output signal approaches the maximum for the system. The wide-band response is achieved with low-noise operational amplifiers and second-order active filters. Signals with periods greater than 30 sec are amplified by 100 db and those with periods shorter than 1 sec are amplified by 70 db. The system works well in extending the useful output range of a Willmore Mark II seismometer with a natural period of 1.5 sec to over 40 sec under normal field operating conditions. When analog recording, the gain-range switching occurs when the input signal reaches ±8.1-v; when digital recording, the level is ±9.375 v. The period in a divide-by-4- or 16-state is preset by the experimentalist. The gain level is recorded on an extra channel which is also used to record absolute time.

Compensation for limited dynamic range of recording instruments by use of an electronic compressor

Abstract: Due to the limited dynamic range of magnetic tape recorders, the recording of signals with large peak excursions compared to the average energy requires a choice between over‐driving the recorder, or accepting a low signal‐to‐noise ratio. It is demonstrated that a simple and inexpensive limiter circuit can be successfully used to circumvent this problem. Pseudodata produced in the laboratory were recorded via such a circuit and the performance of the system was evaluated by comparing the calculated probability densities, third‐ and fourth‐order moments, and spectra, of the original and recorded signals.