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.

A current-mode gain-control scheme with constant bandwidth and propagation delay for a transimpedance preamplifier

Abstract: This paper presents a current-mode gain-control scheme that significantly increases the input dynamic range of a wideband optoelectronic receiver without affecting its bandwidth or delay or deteriorating its noise properties. A current buffer with variable attenuation is placed between the photodetector and the transimpedance preamplifier. In this way, the input dynamic range of the receiver can be increased, or alternatively, the signal dynamics can be reduced, by over 20 dB. A BiCMOS test circuit designed for a pulsed time-of-flight laser rangefinder has a measured bandwidth of 170 MHz and an input dynamic range of /spl sim/80 dB. The delay varies only /spl plusmn/5 ps when the gain is varied by 24 dB (1:15).

Experimental evaluation of leaky least-mean-square algorithms for active noise reduction in communication headsets

Abstract: An adaptive leaky normalized least-mean-square (NLMS) algorithm has been developed to optimize stability and performance of active noise cancellation systems. The research addresses LMS filter performance issues related to insufficient excitation, nonstationary noise fields, and time-varying signal-to-noise ratio. The adaptive leaky NLMS algorithm is based on a Lyapunov tuning approach in which three candidate algorithms, each of which is a function of the instantaneous measured reference input, measurement noise variance, and filter length, are shown to provide varying degrees of tradeoff between stability and noise reduction performance. Each algorithm is evaluated experimentally for reduction of low frequency noise in communication headsets, and stability and noise reduction performance are compared with that of traditional NLMS and fixed-leakage NLMS algorithms. Acoustic measurements are made in a specially designed acoustic test cell which is based on the original work of Ryan et al. ["Enclosure for low frequency assessment of active noise reducing circumaural headsets and hearing protection," Can. Acoust. 21, 19-20 (1993)] and which provides a highly controlled and uniform acoustic environment. The stability and performance of the active noise reduction system, including a prototype communication headset, are investigated for a variety of noise sources ranging from stationary tonal noise to highly nonstationary measured F-16 aircraft noise over a 20 dB dynamic range. Results demonstrate significant improvements in stability of Lyapunov-tuned LMS algorithms over traditional leaky or nonleaky normalized algorithms, while providing noise reduction performance equivalent to that of the NLMS algorithm for idealized noise fields.

Glare encoding of high dynamic range images

Abstract: Without specialized sensor technology or custom, multi-chip cameras, high dynamic range imaging typically involves time-sequential capture of multiple photographs. The obvious downside to this approach is that it cannot easily be applied to images with moving objects, especially if the motions are complex. In this paper, we take a novel view of HDR capture, which is based on a computational photography approach. We propose to first optically encode both the low dynamic range portion of the scene and highlight information into a low dynamic range image that can be captured with a conventional image sensor. This step is achieved using a cross-screen, or star filter. Second, we decode, in software, both the low dynamic range image and the highlight information. Lastly, these two portions can be combined to form an image of a higher dynamic range than the regular sensor dynamic range.

A low-power highly-digitized receiver for 2.4-GHz-band GFSK applications

Abstract: This paper describes the design and measurement results of a low-power highly digitized receiver for Gaussian frequency-shift keying modulated input signals at 2.4 GHz. The RF front-end has been based on a low-IF architecture and does not require any variable gain or filtering blocks. The full dynamic range of the low-IF signal is converted into the digital domain by a low-power high-resolution time-continuous SigmaDelta analog-to-digital converter (ADC). This leads to a linear receive chain without limiters. A fifth-order poly-phase loop filter is used in the complex SigmaDelta ADC. The digital block performs filtering and demodulation. Channel filtering is combined with matched filtering and the suppression of noise resulting from the SigmaDelta ADC. The high degree of digitization leads to design flexibility with respect to changing standards and scalability in future CMOS generations. The receiver has been realized in a standard 0.18-mum CMOS process and measures 3.5 mm2. The only external components are an antenna filter and a crystal. The power consumption is only 32 mW in the continuous mode, which is at least a factor of two lower than state-of-the-art CMOS receivers

Dynamic range requirements for MRI

Abstract: In order to realize the full potential in an MR receiver, the digitizer must capture a signal magnitude range from the central k-space peak to the thermal noise floor of the system. This dynamic range can exceed the performance of standard 16-bit data converters. For example, a whole-body mouse scan in a 7 Tesla magnet requires 20 bits of dynamic range. A 3D high-resolution mouse scan at 75 μm isotropic voxel resolution using a 16-bit spectrometer shows an eightfold improvement in image SNR by gain stepping the receiver prior to digitization to cover the full magnitude dynamic range compared to a standard fixed gain approach. A method is presented to determine the dynamic range requirements of any experiment. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 26B: 28–35, 2005.