Dynamic range

About: Dynamic range is a research topic. Over the lifetime, 7576 publications have been published within this topic receiving 101739 citations. The topic is also known as: DNR & DR.

Alternate pixel architectures for large-area medical imaging

Abstract: Amorphous silicon active matrix flat-panel imagers have gained considerable significant in digital diagnostic medical imaging applications in view of their large area readout capability. The pixel, forming the fundamental unit of the active matrix, consists of a detector and readout circuit. The most widely used architecture is a passive pixel sensor (PPS) where the pixel consists of a detector and an a-Si:H thin-film transistor readout switch. While the PPS has the advantage of being compact and amenable towards high-resolution imaging, reading the low PPS output signal require external circuitry such as column charge amplifiers. More importantly, these amplifiers add a large noise component to the PPS that reduces the minimum readable sensor input signal. This work presents an alternate pixel architecture that can perform on-pixel input signal amplification, i.e. an active pixel sensor (APS). Two operating modes of the APS, voltage output (V-APS) and current output (C-APS) are introduced but the focus is on C- APS. Theoretical calculations indicating the feasibility of the C-APS for low-noise, real time imaging applications (e.g. fluoroscopy) are presented. Specifically, signal gain, dynamic range, readout rate and noise of the C-APS are examined. Lastly, initial experimental results of C-APS linearity and gain are presented in addition to a discussion on APS threshold voltage stability.

High-speed microstrip multi-anode multichannel plate detector system

Abstract: High-speed detector systems with high dynamic range and pulse width characteristics in the sub-nanosecond regime are mandatory for high resolution and highly sensitive time-of-flight mass spectrometers. Typically, for a reasonable detector area, an impedance-matched anode design is necessary to transmit the registered signal fast and distortion-free from the anode to the signal acquisition system. In this report, a high-speed microstrip multi-anode multichannel plate detector is presented and discussed. The anode consists of four separate active concentric anode segments allowing a simultaneous readout of signal with a dynamic range of about eight orders of magnitude. The impedance matched anode segments show pulse width of about 250 ps, measured at full width at half maximum, and rise time of ∼170 ps, measured with an oscilloscope with a sampling rate of 20 GS/s and 4 GHz analogue bandwidth. The usage of multichannel plates as signal amplifier allowed the design of a lightweight, low power consuming, and compact detector system, suitable, e.g., for the integration into space instrumentation or portable systems where size, weight, and power consumption are limited parameters.

Threshold-variation-enhanced adaptability of response in a nanowire field-effect transistor network

Abstract: Stochastic resonance in a summing network with varied thresholds was investigated using GaAs-based etched nanowire field-effect transistors having different threshold voltages. The network’s response adapted to input offset fluctuations in the range of the threshold voltage variation and the network could detect a weak signal without any adjustment of the input offset or the addition of high noise. The observed adaptability resulted from a widened dynamic range of the system due to signal decomposition and reconstruction by multiple thresholds together with the output summation process.

High-rate conditioning pulse trains in cochlear implants: Dynamic range measures with sinusoidal stimuli

Abstract: The addition of a continuous, unmodulated, high-rate pulse train to the electrical signals of cochlear implant recipients results in statistically significant increases in psychophysical dynamic range (41 out of 46 electrode pairs tested). The observed increases in dynamic range are thought to result from nerve conditioning by appropriate levels of high-rate pulse train. Five dynamic range profiles are characterized, defining the different responses of dynamic range observed with increasing levels of the conditioner. Four of the five profiles demonstrate increases in dynamic range, with three showing behavior consistent with stochastic resonance. One profile depicts evidence of adaptation in response to higher levels of the conditioner, with a recovery period lasting throughout the duration (on the scale of tens of minutes) of experimentation. Dynamic range profiles are shown to be similar across sinusoidal frequencies (202, 515, and 1031 Hz) but potentially different across electrode pairs (electrodes 1-2, 7-8, and 15-16). Correlation analysis does not reveal any predictors of optimal conditioner level or amount of dynamic range increase with the conditioner.

Improved Dynamic Range Microwave Photonic Instantaneous Frequency Measurement Based on Four-Wave Mixing

Abstract: An improved dynamic range instantaneous frequency measurement system based on four-wave mixing effect in a highly nonlinear fiber was practically demonstrated. A closed-form model was developed to predict the behavior of the system. The model predicted that the system output would have a low frequency voltage which was a function of RF input frequency. The system performance was also practically demonstrated. The system characterization showed a 0.04-40-GHz frequency measurement range with 51-dB dynamic range for 100-MHz measurement error at the end of the band. A maximum relative measurement error of 0.35% was achieved over the entire frequency range. This dynamic range was achieved by employing the lock-in amplification technique.