Showing papers on "Dynamic range published in 2004"

A digitally enhanced 1.8-V 15-bit 40-MSample/s CMOS pipelined ADC

Abstract: A 1.8-V 15-bit 40-MSample/s CMOS pipelined analog-to-digital converter with 90-dB spurious-free dynamic range (SFDR) and 72-dB peak signal-to-noise ratio (SNR) over the full Nyquist band is presented. Its differential and integral nonlinearities are 0.25 LSB and 1.5 LSB, respectively, and its power consumption is 400 mW. This performance is enabled by digital background calibration of internal digital-to-analog converter (DAC) noise and interstage gain errors. The calibration achieves improvements of better than 12 dB in signal-to-noise plus distortion ratio and 20 dB in SFDR relative to the case where calibration is disabled. Other enabling features of the prototype integrated circuit (IC) include a low-latency, segmented, dynamic element-matching DAC, distributed passive input signal sampling, and asymmetric clocking to maximize the time available for the first-stage residue amplifier to settle. The IC is realized in a 0.18-/spl mu/m mixed-signal CMOS process and has a die size of 4mm/spl times/5 mm.

Split Aperture Imaging for High Dynamic Range

Abstract: Most imaging sensors have limited dynamic range and hence are sensitive to only a part of the illumination range present in a natural scene. The dynamic range can be improved by acquiring multiple images of the same scene under different exposure settings and then combining them. In this paper, we describe a camera design for simultaneously acquiring multiple images. The cross-section of the incoming beam from a scene point is partitioned into as many parts as the required number of images. This is done by splitting the aperture into multiple parts and directing the beam exiting from each in a different direction using an assembly of mirrors. A sensor is placed in the path of each beam and exposure of each sensor is controlled either by appropriately setting its exposure parameter, or by splitting the incoming beam unevenly. The resulting multiple exposure images are used to construct a high dynamic range image. We have implemented a video-rate camera based on this design and the results obtained are presented.

A cascaded continuous-time /spl Sigma//spl Delta/ Modulator with 67-dB dynamic range in 10-MHz bandwidth

Abstract: This paper presents the design of a 2-2 cascaded continuous-time sigma-delta modulator. The cascaded modulator comprises two stages with second-order continuous-time resonator loopfilters, 4-bit quantizers, and feedback digital-to-analog converters. The digital noise cancellation filter design is determined using continuous-time to discrete-time transformation of the sigma-delta loopfilter transfer functions. The required matching between the analog and digital filter coefficients is achieved by means of simple digital calibration of the noise cancellation filter. Measurement results of a 0.18-/spl mu/m CMOS prototype chip demonstrate 67-dB dynamic range in a 10-MHz bandwidth at 8 times oversampling for a single continuous-time cascaded modulator. Two cascaded modulators in quadrature configuration provide 20-MHz aggregate bandwidth. Measured anti-alias suppression is over 50 dB for input signals in the band from 150 to 170 MHz around the sampling frequency of 160 MHz.

Direct HDR capture of the sun and sky

Abstract: We present a technique for capturing the extreme dynamic range of natural illumination environments that include the sun and sky, which has presented a challenge for traditional high dynamic range photography processes. We find that through careful selection of exposure times, aperture, and neutral density filters that this full range can be covered in seven exposures with a standard digital camera. We discuss the particular calibration issues such as lens vignetting, infrared sensitivity, and spectral transmission of neutral density filters which must be addressed. We present an adaptive exposure range adjustment technique for minimizing the number of exposures necessary. We demonstrate our results by showing time-lapse renderings of a complex scene illuminated by high-resolution, high dynamic range natural illumination environments.

Method and system to differentially enhance sensor dynamic range

Abstract: Effective differential dynamic range in a differential pixel detector (70) is increased by avoiding saturation effects due to common mode contribution in optical energy to be detected. Photocurrent generated by each photodetector (Da) pair is directly integrated by an associated capacitor (Ca) over an integration time T. Within time T, before either integrated capacitor voltage reaches Vsat for the photodetector, at least one of the capacitors is reset to a voltage such that the desired differential detector signal is still determinable. Reset may be generated externally or internally to the differential pixel detector.

A C-band high-dynamic range GaN HEMT low-noise amplifier

Abstract: A C-band low-noise amplifier (LNA) is designed and fabricated using GAN HEMT power devices. The one-stage amplifier has a measured noise figure of 1.6 dB at 6 GHz, with an associated gain of 10.9 dB and IIP3 of 13 dBm. it also exhibits broadband operation from 4-8 GHz with noise figure less than 1.9 dB. The circuit can endure up to 31 dBm power from the input port. Compared to circuits based on other material and technology, the circuit shows comparable noise figure with improved dynamic range and survivability.

Multiple-gain-ranging readout method to extend the dynamic range of amorphous silicon flat-panel imagers

Abstract: The dynamic range of many flat panel imaging systems are fundamentally limited by the dynamic range of the charge amplifier and readout signal processing. We developed two new flat panel readout methods that achieve extended dynamic range by changing the read out charge amplifier feedback capacitance dynamically and on a real-time basis. In one method, the feedback capacitor is selected automatically by a level sensing circuit, pixel-by-pixel, based on its exposure level. Alternatively, capacitor selection is driven externally, such that each pixel is read out two (or more) times, each time with increased feedback capacitance. Both methods allow the acquisition of X-ray image data with a dynamic range approaching the fundamental limits of flat panel pixels. Data with an equivalent bit depth of better than 16 bits are made available for further image processing. Successful implementation of these methods requires careful matching of selectable capacitor values and switching thresholds, with the imager noise and sensitivity characteristics, to insure X-ray quantum limited operation over the whole extended dynamic range. Successful implementation also depends on the use of new calibration methods and image reconstruction algorithms, to insure artifact free rebuilding of linear image data by the downstream image processing systems. The multiple gain ranging flat panel readout method extends the utility of flat panel imagers and paves the way to new flat panel applications, such as cone beam CT. We believe that this method will provide a valuable extension to the clinical application of flat panel imagers.

Parallel-detection microwave spectroscopy system for breast imaging

Abstract: A liquid-coupled, noncontacting, broadband microwave imaging system has been designed and fabricated. Extension of the operating bandwidth allows us to exploit the potential of new clinical information for breast cancer diagnosis at frequencies higher than previously achieved. The new system design implements a parallel-detection scheme that allows signals to be simultaneously sampled at multiple receiving antenna sites (in 8 s for a single tomographic slice at a single frequency). It also has important features such as high cross-channel isolation (>120 dB), smooth broad bandwidth receiver response, and adjustable intermediate frequency signal amplification factors of 1 to 2000 to ensure successful realization of a large linear dynamic range which is especially important to counteract the increased signal loss at the higher operating frequencies. The new system is capable of recovering dielectric properties of breastlike phantoms with tumor inclusions over the frequency range from 0.5 to 2.1 GHz when embedded in an 87%/13% glycerin/water background. Errors in the measurement data are less than 0.5% in signal amplitude and 1° in phase, on average.

Scalable multichannel MRI data acquisition system.

Abstract: A scalable multichannel digital MRI receiver system was designed to achieve high bandwidth echo-planar imaging (EPI) acquisitions for applications such as BOLD-fMRI. The modular system design allows for easy extension to an arbitrary number of channels. A 16-channel receiver was developed and integrated with a General Electric (GE) Signa 3T VH/3 clinical scanner. Receiver performance was evaluated on phantoms and human volunteers using a custom-built 16-element receive-only brain surface coil array. At an output bandwidth of 1 MHz, a 100% acquisition duty cycle was achieved. Overall system noise figure and dynamic range were better than 0.85 dB and 84 dB, respectively. During repetitive EPI scanning on phantoms, the relative temporal standard deviation of the image intensity time-course was below 0.2%. As compared to the product birdcage head coil, 16-channel reception with the custom array yielded a nearly 6-fold SNR gain in the cerebral cortex and a 1.8-fold SNR gain in the center of the brain. The excellent system stability combined with the increased sensitivity and SENSE capabilities of 16-channel coils are expected to significantly benefit and enhance fMRI applications.

Direct HDR capture of the sun and sky

Abstract: We present a technique for capturing the extreme dynamic range of natural illumination environments that include the sun and sky, which has presented a challenge for traditional high dynamic range photography processes. We find that through careful selection of exposure times, aperture, and neutral density filters that this full range can be covered in seven exposures with a standard digital camera. We discuss the particular calibration issues such as lens vignetting, infrared sensitivity, and spectral transmission of neutral density filters which must be addressed. We present an adaptive exposure range adjustment technique for minimizing the number of exposures necessary. We demonstrate our results by showing time-lapse renderings of a complex scene illuminated by high-resolution, high dynamic range natural illumination environments.

Method and apparatus for adaptive sound processing parameters

Abstract: An input sound signal (210) is processed in order to meet a target dynamic range (910, 920). At least one gain, specific to the input sound signal (210), is applied to the input sound signal (210) to produce a processed sound signal (214). A dynamic range of the processed sound signal is measured, and a match of the measured dynamic range with the target dynamic range (910, 920) is determined. The gain is adjusted in accordance with at least one input sound signal -specific parameter, to improve the match of dynamic range of the processed sound signal (214) to the target dynamic range (910, 920). The input sound signal -specific parameter is adaptive in response to at least one monitored signal condition.

A 1/3'' VGA linear wide dynamic range CMOS image sensor implementing a predictive multiple sampling algorithm with overlapping integration intervals

Abstract: Many tasks performed by machine vision systems involve processing of natural scenes with large intra-frame illumination ratios. Thus, wide dynamic range visible spectrum image sensors are required to achieve adequate processing performance and reliability. An image sensor implementing an algorithm that linearly increases the illumination dynamic range of solid-state pixels is presented. Optimal exposure is achieved with a predictive pixel saturation decision that allows for multiple integration intervals of different duration to run concurrently for different pixels while keeping the sensor frame rate constant. A proof-of-concept chip was fabricated in a 0.18-/spl mu/m CMOS process. Added functionality to standard imagers is mainly concentrated off-pixel so fill factor is not sacrificed. Measured data corroborates the algorithm functionality.

A time-to-first spike CMOS imager

Abstract: A novel time-to-first-spike CMOS imager is presented, in which the timing of a single spike from each pixel encodes the illuminance of each pixel. This temporal representation of illuminance can widen the image sensor dynamic range to over 100 dB. To reduce power consumption, an asynchronous address-event readout technique is incorporated. The imager essentially implements a pixel-level A/D conversion and benefits from the continued process scaling to deep submicron levels. Results are shown from a 32/spl times/32 pixel imager fabricated in the 0.5 /spl mu/m AMI process with measured dynamic range of 104 dB in one image. A test chip with one pixel and digital control logic has been fabricated through MOSIS using the TSMC 0.18 /spl mu/m standard digital CMOS process. It has demonstrated the expected functionalities. A modified architecture is also proposed for a larger imager array.

Multi-anode detector with increased dynamic range for time-of-flight mass spectrometers with counting data acquisitions

Abstract: A detection scheme for time-of-flight mass spectrometers is described that extends the dynamic range of spectrometers that use counting techniques while avoiding the problems of crosstalk. It is well known that a multiple anode detector capable of detecting different fractions of the incoming particles may be used to increase the dynamic range of a TOFMS system. However, crosstalk between the anodes limits the amount by which the dynamic range may be increased. The present invention overcomes limitations imposed by crosstalk by using either a secondary amplification stage or by using different primary amplification stages.

A cascaded continuous-time ΣΔ modulator with 67-dB dynamic range in 10-MHz bandwidth

Abstract: This paper presents the design of a 2-2 cascaded continuous-time sigma-delta modulator. The cascaded modulator comprises two stages with second-order continuous-time resonator loopfilters, 4-bit quantizers, and feedback digital-to-analog converters. The digital noise cancellation filter design is determined using continuous-time to discrete-time transformation of the sigma-delta loopfilter transfer functions. The required matching between the analog and digital filter coefficients is achieved by means of simple digital calibration of the noise cancellation filter. Measurement results of a 0.18-μm CMOS prototype chip demonstrate 67-dB dynamic range in a 10-MHz bandwidth at 8 times oversampling for a single continuous-time cascaded modulator. Two cascaded modulators in quadrature configuration provide 20-MHz aggregate bandwidth. Measured anti-alias suppression is over 50 dB for input signals in the band from 150 to 170 MHz around the sampling frequency of 160 MHz.

Method for improving digital images and an image sensor for sensing the same

Abstract: The present invention provides an image processing method. In one embodiment, the method provides discontinuity-preserving image smoothing and segmentation, noise reduction, reduction of image variations particularly those variations caused by illumination conditions, exposure compensation, and dynamic range compression. The present invention also provides an electronic image sensor that is able to detect high dynamic range optical images and produce electronic images with reduced dynamic range.

High-speed CMOS image sensor circuits with in situ frame storage

Abstract: Two CMOS image sensor circuit prototypes equipped with in situ frame storage have been fabricated and tested. Capable of 4-400 M-frames/s and between 66 and 79 dB rms dynamic range, these developments are intended for the capture of fast, brief, transient events with high resolution. Applications include accelerator-based flash radiography such as proton radiography. The first is a small two-dimensional (2-D) prototype in which each pixel includes either a capacitive trans-impedance amplifier or a direct-integration source-follower front end, followed by an array of 64 frame storage sample capacitors and associated readout electronics. The acquisition of either 32 frames using correlated double sampling (CDS) at 4 M-frames/s, or 64 frames without CDS at up to 10.5 M-frames/s (-3 dB), and up to 13 b dynamic range was achieved. The second is a monolithic solid state "streak camera", a 1-D linear array of 150 photodiodes, with a 150-frame analog storage array. This device reached 400-M-frames/s operation with electrical test inputs, at least 100-M-frames/s operation with optical inputs, and achieves over 11 b of dynamic range. These circuits demonstrate the high performance possible with CMOS sensor circuits containing in situ frame storage.

High-dynamic range image sensors

Abstract: The dynamic range of existing CMOS image sensors is limited. The present invention introduces an extended dynamic range CMOS pixel sensor circuit. The extended dynamic range CMOS pixel sensor circuit is relatively similar to existing CMOS pixel sensors except that a charge pump has been added to recharge the pixel sensor when the pixel sensor is nearing charge depletion. Every firing of the charge pump is counted. To create a final output for the extended dynamic range CMOS pixel sensor circuit, the number of charge pump firings is combined with a final analog voltage reading of the pixel sensor circuit.

PWM digital pixel sensor based on asynchronous self-resetting scheme

Abstract: In this letter, a pulse-width modulated digital pixel sensor is presented along with its inherent advantages such as low power consumption and wide operating range. The pixel, which comprises an analog processor and an 8-bit memory cell, operates in an asynchronous self-resetting mode. In contrast to most CMOS image sensors, in our approach, the photocurrent signal is encoded as a pulse-width signal, and converted to an 8-bit digital code using a Gray counter. The dynamic range of the pixel can be adapted by simply modulating the clock frequency of the counter. To test the operation of the proposed pixel architecture, an image sensor array has been designed and fabricated in a 0.35-/spl mu/m CMOS technology, where each pixel occupies an area of 45/spl times/45 /spl mu/m/sup 2/. Here, the operation of the sensor is demonstrated through experimental results.

A novel automatic digital quasi-peak detector for a time domain measurement system

Abstract: An advanced ultra-fast broadband time domain EMI (TDEMI) measurement system is presented Measurements were performed in the 30-1000 MHz range Using digital signal processing for spectral estimation and detection, the measurement time is reduced by a factor of 10 in comparison to a conventional EMI receiver A novel recording routine for TDEMI measurement and digital signal processing for proper quasi-peak detection is described Different amplitude resolutions are selected during the recording to enhance the dynamic range by about 50 dB Measurement results are compared with the results obtained with a conventional EMI receiver

Portable near-infrared diffusive light imager for breast cancer detection.

Abstract: We present a frequency-domain near-infrared optical tomography system designed for breast cancer detection, in conjunction with conventional ultrasound. It features fast optical switching, three-wavelength excitations, and avalanche photodiode as detectors. Laser diodes at 660, 780, and 830 nm are used as light sources and their outputs are distributed sequentially to one of nine source fibers. An equivalent 130-dB isolation between electrical signals from different source channels is achieved with the optical switches of very low crosstalk. Ten detection channels, each of which includes a silicon avalanche photodiode, detect diffusive photon density waves simultaneously. The dynamic range of an avalanche photodiode is about 20 to 30 dB higher than that of a photomultiplier tube, thus eliminating the need for multistep system gain control. The entire system is compact in size (<0.051 m3) and fast in data acquisition (less than 2 sec for a complete scan). Calibration and the clinical experiment results are presented in the paper.

A novel 5GHz RF power detector

Abstract: The principles of a RF power detector using bipolar transistors are analyzed and a new RF power detector for embedded RF IC test is proposed. The new detector uses a voltage divider to provide unequal ac signals for its differential input. It has a more linear transfer function for large-signal detection than previously reported detectors. Also, the detector retains its square-law transfer characteristics for low-level-signal detection. The errors in linear or square-law region operation are within 2%. The crossover region between detector linear and square-law operation is minimized to 30/spl sim/50mV and its detection error is within 8% using either linear or square-law estimation. The detector has 65dB dynamic range and it can work with 5GHz or higher signals as compared to roughly 30dB dynamic range in R.G. Meyer (1995).

4/spl times/2.5 GHz repetitive photonic sampler for high-speed analog-to-digital signal conversion

Abstract: This letter presents a 10-gigasample/s (GS/s) photonic analog-to-digital converter (ADC) system constructed using a four-wavelength picosecond pulsed source. The lasing-to-nonlasing modes suppression ratio of the optical source is over 24 dB. By using the 10-GHz optical source, a 10-GS/s photonic ADC has been demonstrated and was used to sample an arbitrary radio-frequency signal. The system was further investigated by sampling a 2.4-GHz sinusoidal signal. Important parameters including the signal-to-noise and distortion ratio and the spurious-free dynamic range have been determined.

Wide dynamic range image sensor

Abstract: The present invention relates to a CMOS image sensor having a wide dynamic range, which permits favorable imaging even in cases where a bright portion and a dark portion exist simultaneously. The dynamic range can be widened by preventing the saturation of optical charge at a high illuminance by removing low illuminance signals due to long-time accumulation, intermediate illuminance signals due to short-time accumulation, and high illuminance signals due to ultra-short time accumulation from pixel portions of the image sensor. Further, adaptive control of the dynamic range can also be performed by dynamically changing the wide dynamic range imaging conditions that comprise a combination of different accumulation times of each of a plurality of short time accumulation signals.

Polymeric micro-cantilever array for auditory front-end processing

Abstract: A polymeric micro-cantilever array has been developed that mimics the biological front-end processing in the mammalian cochlea, and is intended for use in applications of auditory prostheses. Made of optical epoxy polymer molded over a silicon substrate, the micro-cantilevers have similar mechanical performance as the basilar membranes in the mammalian ears. The polymeric cantilevers, which are transparent, are used as optical waveguides to guide and modulate a light beam, which is initiated from a light emitting diode (LED) and collected by a photo diode, to produce a signal suitable for human hearing when the sound wave excites them. The polymeric cantilevers have Q10 values of 9.38, 10.11, 11.56, and 14.01 for resonant frequencies at 286, 720, 2868, and 6948 Hz, respectively. These values are similar to those obtained by direct measurement of the basilar membrane. Furthermore, they have a linear dynamic range of more than 80 dB sound pressure level (SPL) with less than 15% total harmonic distortion (THD). This polymeric micro-cantilever array has low power consumption, short processing time, high sensitivity, high frequency resolution, small size, is insensitive to electromagnetic interference, and is suitable for a totally implantable device in the human ear. © 2003 Elsevier B.V. All rights reserved.

High dynamic range contrast measurements by use of an optical parametric amplifier correlator.

Abstract: A new design of pulse-contrast-measuring correlator, based on optical parametric amplification, is presented. It amplifies the wings of the pulse and allows high-contrast measurement with a low-sensitivity detector. The test system demonstrates an ability to measure a dynamic range of >10(11):1.

Successive approximation calibration apparatus, system, and method for dynamic range extender

Abstract: A gain characteristic correctable dynamic range enhancement system (DRES) receives input signals from an imager device connected to a correlated double sampling (CDS) circuit for receiving the video signal from the CCD imaging device. The dynamic range enhancement system includes a variable gain amplifier (VGA), and a limited bit-width analog-to-digital converter (ADC) which digitizes the analog signal received from the VGA. The output of the ADC is provided to an initial bit range position of a wider bit-width shifter connected to the output of the ADC. The DRES system correctably extends the dynamic range of the imager device, subject to offsets providing linearity corrections at predetermined trip points, subject to determined offset values, to ensure that there are no discontinuities in the system transfer function.

Saturation effects in active noise control systems

Abstract: The reference and error sensors of active noise control (ANC) systems will be saturated in real-world applications if the noise level exceeds the dynamic range of the sensors. However, there is a lack of analysis of saturation effects on the performance of ANC systems. This paper proposes an indirect method for analyzing the saturation effects in steady state using Fourier analysis. This indirect method uses clipping to approximate saturation and decomposes the saturated narrowband signal as the summation of a set of rectangular waves and a pulse-amplitude modulated signal. The theoretical analysis shows that the clipping of a sinusoidal signal produces extra odd harmonics, thus affecting the convergence speed and steady-state solution of adaptive filter in ANC systems. This analysis can be extended to narrowband noises that consist of multiple sinusoidal components such as engine noise in many ANC applications. A low-pass filter is effective in reducing saturation effects for harmonic-related noises. Analysis results are verified by computer simulations using recorded engine noise and transfer functions measured from an experimental setup.

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

The High Resolution Chirp Transform Spectrometer for the Sofia-Great Instrument

Abstract: In this paper, we present the design of a high resolution Chirp Transform Spectrometer (CTS) which is part of the GREAT (German REceiver for Astronomy at Terahertz frequencies) instrument onboard SOFIA, the Stratospheric Observatory For Infrared Astronomy. The new spectrometer will provide unique spectral resolving power and linearity response, since the analog Fourier transform performed by the CTS spectrometer was improved through a new design, that we call “Adaptive Digital Chirp Processor (ADCP)”. The principle behind the ADCP consists on digitally generating the dispersive signal which adapts to the compressor dispersive properties, achieving maximum spectral resolution and higher dynamic range. Excellent test results have been obtained such as a white noise dynamic range of 30 dB, and a spectral resolution (FWHM) of 41.68 kHz which would mean if analyzing signals with the high frequency band receiver on the GREAT instrument (4.7 THz) a spectral resolving power (λ/Δ λ) higher than 108.