Digital High Speed Research Articles

Digital discrimination of neutrons and γ-rays in a deuterated liquid scintillator using the Simplified Digital Charge Collection method

The neutron/γ-ray discrimination properties of a BC537 deuterated liquid scintillator in a mixed neutron/γ-ray Am–Be source field are investigated with the help of an 8-bit resolution and 2 GSamples/s sampling frequency high-speed digitiser. The Simplified Digital Charge Collection (SDCC) method used for the analysis provides an improvement over the digital charge comparison (CC) method in terms of the Figure of Merit (FoM) values. The FoM and the neutron to γ-ray counts ratio as functions of energy threshold are compared with those of a typical BC501A scintillator in the same mixed neutron/γ-ray radiation field. The results confirm that the BC537 is to be preferred to BC501A for γ-ray detection purposes.

Roflumilast N‐oxide, a PDE4 inhibitor, improves cilia motility and ciliated human bronchial epithelial cells compromised by cigarette smoke in vitro

Mucociliary malfunction occurs in chronic obstructive pulmonary disease (COPD) and compromised functions of ciliated bronchial epithelial cells may contribute to this. Cigarette smoke, a major risk factor for COPD, impairs ciliary beat frequency (CBF). cAMP augments CBF. This in vitro study addressed, in differentiated, primary human bronchial epithelial cells, whether roflumilast N-oxide, a PDE4 inhibitor, (i) augments CBF; (ii) prevents the reduction in CBF induced by cigarette smoke extract (CSE); and (iii) protects against the loss of the ciliated phenotype following long-term CSE exposure. Air-liquid interface cultured human bronchial epithelial cells were incubated with roflumilast N-oxide and exposed to CSE. CBF was assessed by digital high speed video microscopy (DHSV). Ciliated cells were characterized by β-tubulin IV staining and analyses of Foxj1 and Dnai2 mRNA and protein (real-time quantitative PCR, Western blotting). Roflumilast N-oxide concentration-dependently triggered a rapid and persistent increase in CBF and reversed the decrease in CBF following CSE. Long-term incubation of bronchial epithelial cells with CSE resulted in a loss in ciliated cells associated with reduced expression of the ciliated cell markers Foxj1 and Dnai2. The PDE4 inhibitor prevented this loss in the ciliated cell phenotype and the compromised Foxj1 and Dnai2 expression. The enhanced release of IL-13 following CSE, a cytokine that diminishes the proportion of ciliated cells and in parallel, reduces Foxj1 and Dnai2, was reversed by roflumilast N-oxide. Roflumilast N-oxide protected differentiated human bronchial epithelial cells from reduced CBF and loss of ciliated cells following CSE.

New Adenylate Kinase 7 (AK7) Mutation in Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is a congenital hereditary disease affecting 1/20,000-60,000 people that causes chronic sinusitis, bronchiectasis, sinus hypoplasia, secretory otitis media, and low fertility. The complexity and heterogeneity of the disease make diagnosis difficult. Although the genetic origin of PCD is clear, mutations in only five genes have been associated with the disease, and, to date, no disease-causing gene has been identified. Recently, low levels of AK7 gene expression have been linked to PCD. This study was designed to determine the mutational status of the AK7 gene in 31 PCD (17 PCD and 14 Kartagener syndrome diagnosed) patients compared with 40 healthy volunteers. We also determined the AK7 sequence in two families with members with PCD and investigated ciliary activity and ciliogenesis in one patient with a mutation in AK7. We analyzed nasal mucociliary transport and cilial ultrastructure by electron microscopy and studied nasal ciliary beat frequency and beat pattern using high-resolution digital high speed video (DHSV) imaging. Mutation analyses were performed by direct resequencing of the 18 exons of the AK7 gene. Air-liquid interface differentiated cultures were studied using DHSV imaging and histochemistry. AK7 gene expression was studied by real-time reverse-transcription polymerase chain reaction. We identified two mutations in the AK7 gene, the described single nucleotide polymorphism (rs2369679), and a new mutation (c.1214insT) that, to the best of our knowledge, has not been described previously. Family and functional studies indicated that c.1214insT could be related to PCD. Our results indicate that AK7 may be involved in the development of PCD.

DESIGN, IMPLEMENTATION AND ANALYSIS OF FLASH ADC ARCHITECTURE WITH DIFFERENTIAL AMPLIFIER AS COMPARATOR USING CUSTOM DESIGN APPROACH

Analog-to-Digital Converters (ADCs) are useful building blocks in many applications such as a data storage read channel and an optical receiver because they represent the interface between the real world analog signal and the digital signal processors. Many implementations have been reported in the literature in order to obtain high-speed analog-todigital converters (ADCs). In this paper an effort is made to design 4-bit Flash Analog to Digital Converter [ADC] using 180nm cmos technology. For high-speed applications, a flash ADC is often used. Resolution, speed, and power consumption are the three key parameters for an Analog-to-Digital Converter (ADC). The integrated flash ADC is operated at 4-bit precision with analog input voltage of 0 to 1.8V. The ADC has been designed, implemented & analysed in standard gpdk180nm technology library using Cadence tool.

Analysis of ependymal ciliary beat pattern and beat frequency using high speed imaging: comparison with the photomultiplier and photodiode methods

BackgroundThe aim of this study was to compare beat frequency measurements of ependymal cilia made by digital high speed imaging to those obtained using the photomultiplier and modified photodiode techniques. Using high speed video analysis the relationship of the power and recover strokes was also determined.MethodsCiliated strips of ependyma attached to slices from the brain of Wistar rats were incubated at 30°C and observed using a ×50 water immersion lens. Ciliary beat frequency was measured using each of the three techniques: the high speed video, photodiode and photomultiplier. Readings were repeated after 30 minutes incubation at 37°C. Ependymal cilia were observed in slow motion and the precise movement of cilia during the recovery stroke relative to the path travelled during the power stroke was measured.ResultsThe mean (95% confidence intervals) beat frequencies determined by the high speed video, photomultiplier and photodiode at 30°C were 27.7 (26.6 to 28.8), 25.5 (24.4 to 26.6) and 20.8 (20.4 to 21.3) Hz, respectively. The mean (95% confidence intervals) beat frequencies determined by the high speed video, photomultiplier and photodiode at 37°C were 36.4 (34 to 39.5), 38.4 (36.8 to 39.9) and 18.8 (16.9 to 20.5) Hz. The inter and intra observer reliability for measurement of ciliary beat frequency was 3.8% and 1%, respectively. Ependymal cilia were observed to move in a planar fashion during the power and recovery strokes with a maximum deviation to the right of the midline of 12.1(11.8 to 13.0)° during the power stroke and 12.6(11.6 to 13.6)° to the left of the midline during the recovery stroke.ConclusionThe photodiode technique greatly underestimates ciliary beat frequency and should not be used to measure ependymal ciliary beat frequency at the temperatures studied. Ciliary beat frequency from the high speed video and photomultiplier techniques cannot be used interchangeably. Ependymal cilia had minimal deviation to the right side during their power stroke and to the left during the recovery stroke.

Efficient Measurement of Impulses Based on Frequency-Domain Approach

This paper designs and experimentally demonstrates an electronic hardware architecture to measure impulse signals without resorting to high-speed analog-to-digital converters (ADCs). The proposed architecture is based on a frequency-domain approach. It consists of multiple channels to down-convert the input signal, each of which obtains a small portion of the input's spectrum. Overlapping bands are designated in between every two adjacent channels, so that multiple narrow-band outcomes can be accurately merged to construct the entire spectrum through postprocessing. The resultant complex-valued spectrum is equivalent to that where the impulses are directly measured in the time domain. The architecture in this paper resembles traditional superheterodyne receivers, and hence, its circuit implementation is simple and robust and has low cost. In our circuit implementation, all the components involved (like oscillators and mixers) are commercially available and have low costs. The circuit is tested by two types of input impulses, both having spectra centered at 2.1 GHz. The input signals' spectra (including both magnitude and phase) obtained by our circuit show excellent agreement with the data measured by a 40-GHz oscilloscope. When the input signal-to-noise ratio is as low as 2 dB, the output of our frequency-domain approach is equivalent to that of a 4-b high-speed ADC.

Controlling Gasoline Low Temperature Combustion by Diesel Micro Pilot Injection

The simultaneous reduction of fuel consumption and pollutant emissions, namely NOx and soot, is the predominant goal in modern engine development. In this context, low temperature combustion concepts are believed to be the most promising approaches to resolve the above mentioned conflict of goals. Disadvantageously these combustion concepts show high peak pressures or high rates of pressure rise due to early ignition and high reaction rates especially at high loads. Furthermore, there are still challenges in controlling combustion phasing. In this context using a small amount of pilot diesel injected directly into the combustion chamber to ignite a highly diluted gasoline air mixture can overcome the aforementioned difficulties. As the gasoline does not ignite without the diesel, the pilot injection timing can be used to control combustion phasing. By increasing dilution even high loads with low rates of pressure rise and without knocking are possible. This paper shows the results of experimental investigations carried out on a heavy duty boosted single cylinder diesel engine. Based on the indicated cylinder pressure, the combustion process is characterized by performing knock analyses as well as thermodynamic analyses. Furthermore, an optically accessible engine has been set up to investigate both the diesel injection and the combustion process by means of digital high speed imaging. Together with the thermodynamic analyses the results of these optical investigations make up the base for the presented theoretical model of this combined diesel-gasoline combustion process. To show the load potential of this Dual-Fuel-CAI concept, the engine was operated at 2100 1/min with an IMEP of 19 bar. NOx emissions did not exceed 0.027 g/kWh.

A new method for measuring the response time of the high pressure ionization chamber

Time response is an important performance characteristic for gas-pressurized ionization chambers. To study the time response, it is especially crucial to measure the ion drift time in high pressure ionization chambers. In this paper, a new approach is proposed to study the ion drift time in high pressure ionization chambers. It is carried out with a short-pulsed X-ray source and a high-speed digitizer. The ion drift time in the chamber is then determined from the digitized data. By measuring the ion drift time of a 15atm xenon testing chamber, the method has been proven to be effective in the time response studies of ionization chambers.

High resolution biomedical imaging—multimodal ultrasound microscope and combination with optics

High frequency ultrasound imaging has evolved from classical acoustic microscopy to the multimodal ultrasound microscope which is available for quantitative C-mode, surface acoustic impedance mode and 3D-mode imaging. The evolution has realized both quantitative parametric imaging and easier observation. Quantitative C-mode representing two-dimensional distribution of attenuation or sound speed is realized by frequency-domain analysis of a single pulse by a high speed digitizer. Because the square of sound speed is proportional to the tissue elasticity, sound speed imaging provides biomechanical information of the tissues which is especially important in cardiology and orthopedic surgery. The data also help understanding clinical echo features, especially important in grading of liver fibrosis. Surface acoustic impedance mode without thin-slicing has been applied for imaging of fresh brain tissues and real time observation of high-intensity focused ultrasound procedures. High frequency 3D-mode imaging has visualized 3D structure of sebaceous gland in dermis. Compared with optical coherence tomography which provides higher resolution imaging, ultrasound is superior in the penetration depth and assessment of tissue elasticity. Photoacoustic imaging provides not only morphology but also small blood flow distribution. Both ultrasound and optical methods should develop together to realize high resolution and “gentle” biomedical imaging.

Development of a High-Speed Digitizer to Time Resolve Nanosecond Fluorescence Pulses

The development of a high-speed digitizer system to measure time-domain voltage pulses in nanoseconds range is presented in this work. The digitizer design includes a high performance digital signal processor, a high-bandwidth analog-to-digital converter of flash-type, a set of delay lines, and a computer to achieve the time-domain measurements. A program running on the processor applies a time-equivalent sampling technique to acquire the input pulse. The processor communicates with the computer via a serial port RS-232 to receive commands and to transmit data. A control program written in LabVIEW 7.1 starts an acquisition routine in the processor. The program reads data from processor point by point in each occurrence of the signal, and plots each point to recover the time-resolved input pulse after n occurrences. The developed prototype is applied to measure fluorescence pulses from a homemade spectrometer. For this application, the LabVIEW program was improved to control the spectrometer, and to register and plot time-resolved fluorescence pulses produced by a substance. The developed digitizer has 750 MHz of analog input bandwidth, and it is able to resolve 2 ns rise-time pulses with 150 ps of resolution and a temporal error of 2.6 percent.

Solitary deflection waves on the supersonic domain wall in yttrium orthoferrite

The moving antiferromagnetic vortices are accompanied by solitary deflection waves. These waves allow to investigate generation and nonlinear dynamics of the antiferromagnetic vortices on the moving domain wall with the help of the two- and three-fold digital high speed photography. On the quasi-relativistic domain wall the vortex dynamics is quasi-relativistic with the limiting velocity c=20km/s, which is equal to the spin-wave velocity. The solitary deflection waves dynamics can be explained assuming existence of the gyroscopic force. A theory for the gyroscopic force in the orthoferrite domain wall is elaborating by A.K. Zvezdin et al. currently. We present a comparison of the theoretical and experimental results on the dynamics of the solitary deflection waves, which accompany the antiferromagnetic vortices in the domain wall of orthoferrites.

Digital post-calibration of a 5-bit 1.25 GS/s flash ADC

We report a high-speed flash analog to digital converter (ADC) linearization technique employing the inverse Volterra model and digital post processing. First, a 1.25 GS/s 5-bit flash ADC is designed using a 0.18 μm CMOS, and the signal is quantized by a distributed track-and-hold circuit. Second, based on the Volterra series, a proposed digital post-calibration model is introduced. Then, the model is applied to estimate and compensate the nonlinearity of the high-speed flash ADC. Simulation results indicate that the distortion is reduced effectively. Specifically, the ADC achieves gains of 4.83 effective bits for a 117.1 MHz frequency input and 4.74 effective bits for a Nyquist input at 1.25 GS/s.

A Low-Cost Bit-Error-Rate BIST Circuit for High-Speed ADCs Based on Gray Coding

SUMMARY Real-time on-chip measurement of bit error rate (BER) for high-speed analog-to-digital converters (ADCs) does not only require expensive multi-port high-speed data acquisition equipment but also enormous post-processing. This paper proposes a low-cost built-in-self-test (BIST) circuit for high-speed ADC BER test. Conventionally, the calculation of BER requires a high-speed adder. The presented method takes the advantages of Gray coding and only needs simple logic circuits for BER evaluation. The prototype of the BIST circuit is fabricated along with a 5-bit high-speed flash ADC in a 90-nm CMOS process. The active area is only 90 μm × 70 μm and the average power consumption is around 0.3 mW at 700 MS/s. The measurement of the BIST circuit shows consistent results

Undersampling channelized receiver using principle of signal matched-phase

In the traditional digital channelized receiver, there is no simple algorithm to reconstruct the wideband cross-channel signal without distortion. Moreover, the analog-to-digital converter (ADC) limits the instantaneous bandwidth and dynamic range of the receiver. These problems restrict the applications of digital channelized receiver in radar and communication. Based on the principle of signal matched-phase, a novel channelized receiver structure is presented, where the sub-channels can be seamlessly combined. The presented structure uses the principle of signal matched-phase to solve the frequency ambiguity in the case of the multi-channel undersampling signals. It can reconstruct the wideband cross-channel signal with extremely low distortion, and that it avoids the use of high-speed and high-resolution ADC in wideband and high dynamic applications. Simulation results show the effectiveness of the structure.

The virtual fields method applied to spalling tests on concrete

For one decade spalling techniques based on the use of a metallic Hopkinson bar put in contact with a concrete sample have been widely employed to characterize the dynamic tensile strength of concrete at strain-rates ranging from a few tens to two hundreds of s −1 . However, the processing method mainly based on the use of the velocity profile measured on the rear free surface of the sample (Novikov formula) remains quite basic and an identification of the whole softening behaviour of the concrete is out of reach. In the present paper a new processing method is proposed based on the use of the Virtual Fields Method (VFM). First, a digital high speed camera is used to record the pictures of a grid glued on the specimen. Next, full-field measurements are used to obtain the axial displacement field at the surface of the specimen. Finally, a specific virtual field has been defined in the VFM equation to use the acceleration map as an alternative ‘load cell’. This method applied to three spalling tests allowed to identify Young’s modulus during the test. It was shown that this modulus is constant during the initial compressive part of the test and decreases in the tensile part when micro-damage exists. It was also shown that in such a simple inertial test, it was possible to reconstruct average axial stress profiles using only the acceleration data. Then, it was possible to construct local stress-strain curves and derive a tensile strength value.

Establishment of high-speed digitization method of herbarium specimen and construction of maintenance-free digital herbarium

Establishment of high-speed digitization method of herbarium specimen and construction of maintenance-free digital herbarium

Mass transfer characteristics of liquid films flowing down a vertical wire in a counter current gas flow

The wetted-wire packing, mainly consisting of a bundle of vertical parallel wires, is a promising concept for the use in separation columns. To investigate the multiphase flow inside the packing in detail and to estimate the performance of the packing, experiments on liquid films on a single vertical wire in a counter current gas flow were carried out. To get information about the interfacial area, an optical measurement of the film thickness was carried out with a digital high speed camera and image recognition tools. By measuring the evaporation of water and aqueous polyvinylpyrrolidone solutions into air, the gas-side mass transfer was determined. The liquid-side mass transfer was examined by measuring the desorption of CO 2 from water into air. The results show that the mass transfer coefficients are comparable to those appearing in common structured packings. When assuming a sufficiently high wire packing density, a specific interfacial area similar to corrugated sheet structured packings can be reached. Previous studies predicted a low pressure drop per packing height and extended capacity limits compared to common packings. In consideration of these results, the wetted wire packing therefore is shown to be suitable especially for absorption processes where a low pressure drop is favourable.

A 6-bit Fully Binary Digital-to-Analog Converter in 0.25-$\mu{\hbox {m}}$ SiGe BiCMOS for Optical Communications

This paper presents an approach to implement a high-speed binary weighted digital-to-analog converter (DAC). A different current switching mechanism is proposed that improves the dynamic performance of binary weighted DACs. Circuit simulation shows an improvement of the rise (fall) time mismatch by a factor of 2 over the conventional structure. It is shown that in a conventional high-speed binary DAC implemented with differential pairs, the spurious-free dynamic range (SFDR) can be degraded by nearly 6 dB due to the different rise (fall) times of the current switches. Using the proposed current switches, a fully binary weighted DAC with nominal resolution of 6 bit has been fabricated in 0.25-μm SiGe technology. The measured SFDR is higher than 30.1 dBc up to 5.9-GHz input signal with a 13.4-GHz clock. The DAC can provide 1.1-V peak-to-peak differential output swing over 50 Ω while dissipating 1050 mW. Full-scale 20%-80% fall time and 2% settling time are measured below 18 and 45 ps, respectively.

Digital EPR with an arbitrary waveform generator and direct detection at the carrier frequency

A digital EPR spectrometer was constructed by replacing the traditional bridge with an arbitrary waveform generator (AWG) to produce excitation patterns and a high-speed digitizer for direct detection of the spin system response at the carrier frequency. Digital down-conversion produced baseband signals in quadrature with very precise orthogonality. Real-time resonator tuning was performed by monitoring the Fourier transforms of signals reflected from the resonator during frequency sweeps generated by the AWG. The capabilities of the system were demonstrated by rapid magnetic field scans at 256 MHz carrier frequency, and FID and spin echo experiments at 1 and 10 GHz carrier frequencies. For the rapid scan experiments the leakage through a cross-loop resonator was compensated by adjusting the amplitude and phase of a sinusoid at the carrier frequency that was generated with another AWG channel.

Power efficient high-speed DAC for wideband communication applications

This paper demonstrates a power efficient design of high-speed Digital-to-Analog Converters (DACs) for wideband communication systems. For Wireless personal area network applications with a 250 MHz signal bandwidth, a 6 bit DAC capable of two times the Nyquist rate sampling is implemented in a current steering segmented 2 + 4 architecture optimized for power efficiency. Along with a proposed master-slave deglitch circuit, several circuit techniques are investigated to improve dynamic performances such as linearity. Implemented in a 0.18 um CMOS process, our DAC achieved a superior conversion performance over the state-of-the-arts, exhibiting integral nonlinearity of less than 0.27 LSB and differential nonlinearity of less than 0.15 LSB. Measured spurious free dynamic range for 251 MHz output signal is 40.92 dB, with total power consumption at 1 GS/s of 6mW, yielding a figure-of-merits of 78.3 pJ/(conversion step*W).