Showing papers on "Dynamic range published in 1973"

Electrically Calibrated Pyroelectric Optical-Radiation Detector

Abstract: An electrically calibrated optical detector has been developed using a pyroelectric response of the plastic, polyvinylfluoride. An in-depth look at the modulation frequency response was performed to substantiate the equivalence of the optical and electrical inputs, indicate the optimum structure and allow for a clearer understanding of the device limitations. The experimental results of the dynamic range, linearity, uniformity, and detectivity confirm the device’s utility.

Noise reduction systems

Abstract: A noise reduction system comprising a compressor feeding an information channel and a complementary expander treating the output of the channel. The system is applicable to audio and visual signals using compressors and expanders with appropriately scaled frequency selective circuits which narrow the band in which compression and expansion take place as the signal level rises. Distortion and tracking accuracy problems are reduced by the use of compressor and expander configurations embodying a main signal circuit and a further signal circuit, the main circuit providing a first signal which has dynamic range linearity with respect to the input signal and the further circuit providing a second signal which is restricted to a small part of the dynamic range of the signal in the main circuit. The restriction may be effected by one or more variable filter means having a pass band which narrows to exclude large signal components from the compression or expansion action. The second signal is combined additively with the first signal for compressor operation and subtractively for expander operation. True complementarity is attainable by the use of a compressor and expander together to provide an overall noise reduction action without introducing defects into the signal being processed.

Sensitivity and Dynamic Range Considerations for Homodyne Detection Systems

Abstract: The effects of modulation frequency, RF reference power, and external bias upon the sensitivity and dynamic range of microwave homodyne detection systems was measured for point contact diodes and low l/f noise Schottky and backward diodes The measurements were made at 489 GHz using a signal to noise ratio of 3 dB and a detection system bandwidth of 10 Hz Maximum sensitivities of -135, -150, and -145 dBm, and dynamic ranges of 92, 110, and 124 dB were measured for the point contact, Schottky, and backward diodes at modulation frequencies of 30, 30, and 3 kHz, respectively It was found that the level of RF reference signal needed to obtain the maximum sensitivity was equal to or somewhat above the point where the diode changes from square law to linear detection The results are significant in that previously reported homodyne sensitivities (not necessarily maximum) were on the order of -90 to -130 dBm for point contact diodes and no data are available for Schottky and backward diodes Significantly improved stability, sensitivity, and dynamic range can be achieved using these low 1/f noise devices, the correct external bias, and the optimum RF reference power

The GaAs dual-gate FET with low noise and wide dynamic range

Abstract: The benefits inherent in the tetrode structure and the potential of GaAs as the material are combined to realize a dual-gate FET with a low noise figure and a wide dynamic range at microwave frequencies. Following the newly constructed design theory of GaAs dual-gate FET, an improved device structure is derived and FET's are fabricated using a Schottky barrier for the gate. The improved device exhibited a noise figure as low as 3dB and a power gain of 12dB at 4GHz. The stability factor and maximum stable gain are much larger than the single gate unit. By varying the 2nd gate bias, the power gain was controllable over a wide range of 30dB at 4GHz without significantly affecting the input impedance.

A Comparison of Optimum and Logarithmic Quantization for Speech PCM and DPCM Systems

Abstract: Two quantization rules, optimum (minimum mean-square error) and logarithmic companding, are compared for application to digital speech transmission. Comparison is made on the basis of signal-to-quantizing noise ratio (S/N), subjective quality judgments, idle channel noise, and dynamic range. These quantizers are considered in both PCM and differential PCM configurations. A computer algorithm is described that yields the optimum quantizer levels for a given speech record. It has been found that the improvement in S/N which optimum quantization affords over conventional logarithmic quantization is offset by the greater idle channel noise and smaller dynamic range (range of talker volumes handled with a lower limit on S/N) of the optimum law.

A Sampling Linear Detector for Accurate rf Pulse Amplitude Measurement

Abstract: A sampling linear detector is described which has been developed for measuring one‐shot free precession amplitudes at 1.5 MHz in a pulsed NMR experiment. A 10−3 accuracy is achieved over a 30 dB dynamic range with a 60 μsec gate aperture time. The rectifying circuit is made up of two low threshold hot carrier diodes placed in the feedback loop of a fast operational amplifier. A bias voltage technique is employed for further linearization. Commercial integrated circuits and operational amplifiers are used throughout and make layout and wiring noncritical. Checking and calibration prodedures, as well as circuit operation, are carefully analyzed.

Signal control circuit

Abstract: A circuit to control the frequency response of a variable filter by means of a control signal based on the amplitude of the information signal to minimize the effect of noise in a signal transmission system. 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 switch, to expand the dynamic range. Control of the filter for low frequency signals is achieved by rectifying and filtering the signals to the control amplifier. Negative-going transients are inverted and by-pass the rectifier and filter and are applied directly to the control amplifier. Positive-going transients are applied through the filter and are not inverted.

A Precision Sampling Circuit

Abstract: A sampling circuit is described, which provides clean output pulses free from transients with excellent linearity and stability in the dynamic range of 0.2–10.0 V. The circuit has been incorporated in a threshold detecting device, allowing the performance of the device to be improved.

Analog multiplication at high frequencies with a high dynamic range

Abstract: An analog multiplier has been constructed by means of field-effect transistors. The multiplier has a dynamic range higher than 80 dB and a frequency response that is flat to within 0.7 dB from 50 to 70 Mhz. This device would be very useful in applications where both inputs may vary by 40 dB or more.

MOSFET surface wave detectors for high frequency signal processing

Abstract: The piezoresistance effect in Si-MOSFET structures is used for the detection of Rayleigh surface waves launched on a silicon substrate. The semiconductor devices are MOSFET N and P-channel inversion layers, the channel length is along the direction of the wave propagation and many elementary detectors have been disposed along the propagation path in order to realize tapped delay lines. Theoretical and experimental results are given for the conversion efficiency, bandwidth, sensitivity and dynamic range for a single N or P channel device. Results are presented also for an array of detectors operating as a variable delay line and as a correlator for a 50 MHz bit rate waveform.