Signal Chain Research Articles

Simple Test Of Transducer Arrays By Imaging Of Ultrasound Emission Into Air

Abstract: A simple test method, feasible for remote or online testing of multi-element ultrasound transducer arrays, is presented. The test requires only a conventional ultrasonic B-mode image visualizing the transducer under investigation emitting into air. In preparation of the test a gray value profile is computed from the image data. Defective trans-ducer elements cause deviations in the profile, which are analyzed by means of a statistical procedure. The perform-ance of the test was investigated using an ultrasonic imaging system (SonixTOUCH, Ultrasonix Medical Corporation, Richmond, Canada) in research mode and masking single elements or element groups to simulate damaged piezoelec-tric elements. The test method allows to detect 2 adjacent defective elements out of a total of 128 transducer elements. Keywords: ultrasound diagnostic, multi-element trans-ducer arrays, quality assessment, statistic evaluation Introduction The quality and reliability of a diagnosis drawn on the basis of a ultrasonic investigation depends to a great ex-tend on the technical quality of the imaging system. Over the last years a number of test methods has been estab-lished which are able to detect different failure types at specific points in the signal chain and at different levels [1]. The ultrasound probe - a high sensitive, mechatronic device - is considered to be the most failure-prone part of the system [2]. Consequently a simple, user independent and reliable test of the transducer elements is a prerequi-site for a broader acceptance of technical quality assur-ance (TQA) in the user community. The analysis of B-mode images acquired when the ultrasound waves are emitted into air could provide such a test modality.

Precision Analog Signal Conditioning Semiconductors for Operation in Very High Temperature Environments

When designing signal chains for systems exposed to high temperature environments, analog signal processing ICs are needed to enable precision sensor measurements. However, as ambient operating temperatures increase beyond the typical extended-industrial +125°C limit, the performance characteristics of analog semiconductors are strongly impacted by the effects of temperature on circuit design, packaging, and the underlying fabrication process. In this paper we introduce two new precision analog components, an operational amplifier and voltage reference, rated for very high temperature operation. We then discuss the steps taken to ensure their performance at high temperature is robust and can be maintained over a limited lifetime. Finally, we demonstrate these devices utilized in an example application: a constant current source for temperature sensor signal conditioning.

Flight Characterization of New Generation GNSS Satellite Clocks

The passive hydrogen maser of GIOVE-B and the new GPS Block IIF Rubidium clock have demonstrated a superior stability in ground tests. In practice, however, the apparent clock performance for GNSS users is limited by measurement errors and imperfections of the signal chain that affect the clock variance at different time scales. Within this paper, we provide a direct comparison of the apparent clock performance for GIOVE-B and the first Block IIF satellite (SVN62). Periodic errors in the apparent clocks of both satellites are analyzed and an effort is made to separate the impact of orbit determination errors from physical clock or line bias variations. For SVN62 an empirical clock correction model is discussed, which offers a notable reduction of the Allan variance at orbital time scales. Furthermore, triple-frequency observations are used to demonstrate the presence of thermally induced line bias variations and to quantify the resulting inter-frequency clock biases.

Performance of FBK SiPMs coupled to PETA3 read-out ASIC for PET application

In this paper we show the energy and timing resolution performances of FBK SiPMs coupled to the PETA3 ASIC for PET application. We developed a measurement set-up to characterize single SiPMs coupled to scintillator exploiting the detector stack developed within the HYPERImage project. In this way we are able to characterize the combined SiPM/ASIC performance with the same signal chain (from the sensor to the ASIC board) used in the PET system. We show that using two scintillator detectors, composed of a 3×3×5mm3 LYSO crystal coupled to a 3×3mm2 SiPM, an intra-stack CRT of about 200ps FWHM can be obtained.

I can See Clearly Now—In 3D: New Test Patterns for a New Format

The emergence of stereoscopic three-dimensional (3D) video brings with it a need for convenient tools for rapid verification and evaluation of displays and signal chains. 3D signal chains have all the usual 2D issues, with the addition of left-right matching of timing and tone scale, as well as special subsampling and compression issues. 3D displays also have issues of timing, tone scale, and subsampling, in addition to viewing angle and left-right crosstalk. This paper will examine measurement techniques that use test sequences to quickly evaluate these 3D system and display parameters.

Design and optimization of the readout system for X-ray CCDs

A readout system for X-ray CCDs based on an improved architecture is presented; by optimizing several critical circuit blocks along the analog signal chain, the conflict between the readout speed and readout noise is greatly alleviated. Using CCD47-10 as its target CCD, the readout system has achieved 8.6e− readout noise and 142 eV FWHM at 5.9 keV Mn Kα under a pixel rate of 80 kHz. Also its performance of imaging has been investigated.

An Algorithm for Quantitatively Calculating I/Q Gain and Phase Mismatch

The in-phase and quadrature modulator (IQ modulator) is a key component in modern wireless transmitter. It provides a convenient method for modulating data bits or symbols onto an RF carrier. It has become the architecture of choice for implementing transmitter signal chains for end applications such as cellular, WiMAX, and wireless point-to-point. However, there are several non-ideal aspects of analog IQ modulator, include IQ gain imbalance, imperfect quadrature, and LO leakage. These imperfections will result in image spectral and degrade MER of the modulator, which in turn degrades bit error rate (BER). Gain matching and phase compensation both affect the total amount of image rejection. Factory calibration can detect the IQ gain and phase mismatch in different frequency and store the correction coefficients in nonvolatile memory. The key issue is how to get the exact mismatch. In this paper, a mathematical model of IQ modulator was established and an analytic solution is obtained about how to get the exact mismatch parameters. DOI: http://dx.doi.org/10.11591/telkomnika.v10i4.872

Investigation of the Suitability of Tissue Phantoms for Testing the Constancy of Ultrasonic Transducer Arrays in Quality Assurance

To ensure high quality ultrasound diagnostics, proper functioning of the devices used is a necessary prerequisite. Ultrasound transducers have proven to be the most failure-prone part of the signal chain. Their technical monitoring is possible in principle with the help of tissue phantoms. The background of the present study is to determine which type of phantoms and which measurement parameters are best suited to a consistency test as part of routine quality assurance of ultrasound imaging systems. A classic wire-type phantom (ATS Mod. 539, ATS Labs Bridgeport, USA) and a 3 D cyst phantom (TCC, Timelkam, Austria) were used for the studies and comparative tests were conducted between intact transducers and those in which faults had been simulated. The collected measurement data show a relatively large scatter. Therefore, statistical analysis methods were used, and the discrimination analysis proved to be a useful tool. Local failures which arise, e. g. due to the breakdown of individual piezoelectric elements or element groups in the transducer array, can be detected with the help of the gray value targets of the ATS phantom, but only in those cases in which the error-affected sound field part actually overlaps with the target under consideration. The TCC phantom is not suitable for the detection of such errors. Global transducer failures, i. e. those that affect the entire array, can even be detected with both types of phantoms. When the emphasis of quality assessment is on the detection of local defects in the array that make up the largest part of the transducer faults, studies with conventional phantoms are only of limited value.

Impulsive interference in communication channels and its mitigation by SPART and other nonlinear filters

A strong digital communication transmitter in close physical proximity to a receiver of a weak signal can noticeably interfere with the latter even when the respective channels are tens or hundreds of megahertz apart. When time domain observations are made in the signal chain of the receiver between the first mixer and the baseband, this interference is likely to appear impulsive. The impulsive nature of this interference provides an opportunity to reduce its power by nonlinear filtering, improving the quality of the receiver channel. This article describes the mitigation, by a particular nonlinear filter, of the impulsive out-of-band (OOB) interference induced in High Speed Downlink Packet Access (HSDPA) by WiFi transmissions, protocols which coexist in many 3G smartphones and mobile hotspots. Our measurements show a decrease in the maximum error-free bit rate of a 1.95 GHz HSDPA receiver caused by the impulsive interference from an OOB 2.4 GHz WiFi transmission, sometimes down to a small fraction of the rate observed in the absence of the interference. We apply a nonlinear SPART filter to recover a noticeable portion of the lost rate and maintain an error-free connection under much higher levels of the WiFi interference than a receiver that does not contain such a filter. These measurements support our wider investigation of OOB interference resulting from digital modulation, which appears impulsive in a receiver, and its mitigation by nonlinear filters.

Interaction of two photoreceptors in the regulation of bacterial photosynthesis genes

The expression of photosynthesis genes in the facultatively photosynthetic bacterium Rhodobacter sphaeroides is controlled by the oxygen tension and by light quantity. Two photoreceptor proteins, AppA and CryB, have been identified in the past, which are involved in this regulation. AppA senses light by its N-terminal BLUF domain, its C-terminal part binds heme and is redox-responsive. Through its interaction to the transcriptional repressor PpsR the AppA photoreceptor controls expression of photosynthesis genes. The cryptochrome-like protein CryB was shown to affect regulation of photosynthesis genes, but the underlying signal chain remained unknown. Here we show that CryB interacts with the C-terminal domain of AppA and modulates the binding of AppA to the transcriptional repressor PpsR in a light-dependent manner. Consequently, binding of the transcription factor PpsR to its DNA target is affected by CryB. In agreement with this, all genes of the PpsR regulon showed altered expression levels in a CryB deletion strain after blue-light illumination. These results elucidate for the first time how a bacterial cryptochrome affects gene expression.

Зв’язок активності висхідних шляхів із фазовим кодуванням у люмбальних відділах спинного мозку

We studied the relationship of discharges phase characteristics in ascending column of spinal cord (SC) and specificity of activation of neurones, which generate negative components of evoked potentials of SC. The discharges was recorded from SC at a level of a presence of dorsal column (DC), spinocervical and dorsal spinocerebellar tract in upper lumbar and thoracic segments at a stimulation of a nerve or DC. It is shown, that the phase of the discharges depends on the quantity of synaptic delays in generating chain of such signals. Thus, the phase of a signal can carry the additional information on specificity of activation of the sensory elements in CNS.

The jasmonate pathway mediates salt tolerance in grapevines.

Salt stress is a major constraint for many crop plants, such as the moderately salt-sensitive economically important fruit crop grapevine. Plants have evolved different strategies for protection against salinity and drought. Jasmonate signalling is a central element of both biotic and abiotic stress responses. To discriminate stress quality, there must be cross-talk with parallel signal chains. Using two grapevine cell lines differing in salt tolerance, the response of jasmonate ZIM/tify-domain (JAZ/TIFY) proteins (negative regulators of jasmonate signalling), a marker for salt adaptation Na+/H+ EXCHANGER (NHX1), and markers for biotic defence STILBENE SYNTHASE (StSy) and RESVERATROL SYNTHASE (RS) were analysed. It is shown that salt stress signalling shares several events with biotic defence including activity of a gadolinium-sensitive calcium influx channel (monitored by apoplastic alkalinization) and transient induction of JAZ/TIFY transcripts. Exogenous jasmonate can rescue growth in the salt-sensitive cell line. Suppression of jasmonate signalling by phenidone or aspirin blocks the induction of JAZ/TIFY transcripts. The rapid induction of RS and StSy characteristic for biotic defence in grapevine is strongly delayed in response to salt stress. In the salt-tolerant line, NHX1 is induced and the formation of reactive oxygen species, monitored as stress markers in the sensitive cell line, is suppressed. The data are discussed in terms of a model where salt stress signalling acts as a default pathway whose readout is modulated by a parallel signal chain triggered by biotic factors downstream of jasmonate signalling.

Spatial- and Time-Correlated Detection of Fission Fragments

With the goal to measure angular correlations of fission fragments in rare fission decay (e.g. ternary and quaternary fission), a multi-detector coincidence system based on two and up to four position sensitive pixel detectors Timepix has been built. In addition to the high granularity, wide dynamic range and per pixel signal threshold, these devices are equipped with per pixel energy and time sensitivity providing more information (position, energy, time), enhances particle-type identification and selectivity of event-by-event detection. Operation of the device with the integrated USB 2.0 based readout interface FITPix and the control and data acquisition software tool Pixelman enables online visualization and flexible/adjustable operation for a different type of experiments. Spatially correlated fission fragments can be thus registered in coincidence. Similarly triggered measurements are performed using an integrated spectrometric module with analogue signal chain electronics. The current status of development together with demonstration of the technique with a 252 Cf source is presented. 1 Motivation

Basic Characteristics of IEC Flickermeter Processing

Flickermeter is a common name for a system that measures the obnoxiousness of flicker caused by voltage fluctuations. The output of flickermeter is a value of short-term flicker severity indicator, . This paper presents the results of the numerical simulations that reconstruct the processing of flickermeter in frequency domain. With the use of standard test signals, the characteristics of flickermeter were determined for the case of amplitude modulation of input signal, frequency modulation of input signal, and for input signal with interharmonic component. For the needs of simulative research, elements of standard IEC flickermeter signal chain as well as test signal source and tools for acquisition, archiving, and presentation of the obtained results were modeled. The results were presented with a set of charts, and the specific fragments of the charts were pointed out and commented on. Some examples of the influence of input signal’s bandwidth limitation on the flickermeter measurement result were presented for the case of AM and FM modulation. In addition, the diagrams that enable the evaluation of flickermeter’s linearity were also presented.

Thin films of substituted polyanilines: interactions with biomolecular systems

We use substituted polyanilines for the construction of new polymer electrodes for interaction studies with the redox protein cytochrome c (cyt c) and the enzyme sulfite oxidase (SO). For these purposes four different polyaniline copolymers are chemically synthesized. Three of them are copolymers, containing 2-methoxyaniline-5-sulfonic acid with variable ratios of aniline; the fourth copolymer consists of 3-amino-benzoic acid and aniline. The results show that all polymers are suitable for being immobilized as thin stable films on gold wire and indium tin oxide (ITO) electrode surfaces from DMSO solution. This can be demonstrated by cyclic voltammetry and UV-Vis spectroscopy measurements. Moreover, cyt c can be electrochemically detected not only in solution, but also immobilized on top of the polymer films. Furthermore, the appearance of a significant catalytic current has been demonstrated for the sulfonated polyanilines, when the polymer-coated protein electrode is being measured upon addition of sulfite oxidase, confirming the establishment of a bioanalytical signal chain. Best results have been obtained for the polymer with highest sulfonation grade. The redox switching of the polymer by the enzymatic reaction can also be analyzed by following the spectral properties of the polymer electrode.

Tuning and amplification strategies for intravascular imaging coils

The manufacturing of intravascular imaging coils poses several challenges. Due to their size, it can be difficult to incorporate local matching networks and signal amplifiers. The goal of this study is to investigate tuning and amplification strategies for intravascular coils and to assess the signal-to-noise benefits of incorporating a matching network and/or miniature amplifier into catheter-based intravascular imaging devices at various locations in the signal chain. The results suggest that the use of a low-noise amplifier close to the receiving coil enables the use of miniature coaxial cables to be used despite being noisy. Moreover, an improvement in the signal-to-noise ratio of over 75% is presented over conventional intravascular coil configurations where the matching circuit and low-noise amplifier are placed at the proximal end. Therefore, designing devices for intravascular applications capable of generating high signal-to-noise ratio images becomes more feasible, also allowing for significant reductions in scan time.

A CMOS Energy Harvesting and Imaging (EHI) Active Pixel Sensor (APS) Imager for Retinal Prosthesis

A CMOS image sensor capable of imaging and energy harvesting on same focal plane is presented for retinal prosthesis. The energy harvesting and imaging (EHI) active pixel sensor (APS) imager was designed, fabricated, and tested in a standard 0.5 μm CMOS process. It has 54 × 50 array of 21 × 21 μm(2) EHI pixels, 10-bit supply boosted (SB) SAR ADC, and charge pump circuits consuming only 14.25 μW from 1.2 V and running at 7.4 frames per second. The supply boosting technique (SBT) is used in an analog signal chain of the EHI imager. Harvested solar energy on focal plane is stored on an off-chip capacitor with the help of a charge pump circuit with better than 70% efficiency. Energy harvesting efficiency of the EHI pixel was measured at different light levels. It was 9.4% while producing 0.41 V open circuit voltage. The EHI imager delivers 3.35 μW of power was delivered to a resistive load at maximum power point operation. The measured pixel array figure of merit (FoM) was 1.32 pW/frame/pixel while imager figure of merit (iFoM) including whole chip power consumption was 696 fJ/pixel/code for the EHI imager.

On the interchannel interference in digital communication systems, its impulsive nature, and its mitigation

A strong digital communication transmitter located in close physical proximity to a receiver of a weak signal can noticeably interfere with the latter even when the respective channels are tens or hundreds of megahertz apart. When time domain observations are made in the signal chain of the receiver between the first mixer and the baseband, this interference is likely to appear impulsive. Understanding the mechanism of this interference is important for its effective mitigation. In this article, we show that impulsiveness, or a high degree of peakedness, of interchannel interference in communication systems results from the non-smooth nature of any physically realizable modulation scheme for transmission of a digital (discontinuous) message. Even modulation schemes designed to be 'smooth', e.g., continuous-phase modulation, are, in fact, not smooth because their higher order time derivatives still contain discontinuities. When observed by an out-of-band receiver, the transmissions from these discontinuities may appear as strong transients with the peak power noticeably exceeding the average power, and the received signal will have a high degree of peakedness. This impulsive nature of the interference provides an opportunity to reduce its power by nonlinear filtering, thus improving quality of the receiver channel.

0–30 V common mode range, 120 dB CMRR, and 10 nV/ $$ \sqrt {\text{Hz}} $$ noise floor current shunt monitor IC with an embedded ΣΔ modulated digital interface

Sensing and controlling current flow is a fundamental requirement for many electronic systems, including power management (DC---DC converters and LDOs), battery chargers, electric vehicles, solenoid positioning, motor control, and power monitoring. Current shunt monitor (CSM) system enables current measurement across an external sense resistor (R S ) in series to current flow. Proposed CSM system can sense a system (power supply) current from 1 to 500 mA across a typical board Cu-trace resistance of 1 ? with less than 10 μV input-referred offset, 150 nV/°C offset drift and 0.1% accuracy. Instead of using a costly zero-TC sense resistor (R S ) that is used in typical CSM systems; proposed method uses existing Cu board trace for sensing. The sense amplifier uses chopper stabilization in the signal chain of the amplifier to suppress input-referred offset down to less than 10 μV. Switching current-mode (SI) FIR filtering is used at the instrumentation amplifier output to filter out the chopping ripple at the harmonics of the chopping frequency. A frequency domain Sigma Delta (ΣΔFD) ADC enables a digital interface to processor applications. The CSM is fabricated on a 0.7 μm CMOS process with three levels of metal with maximum Vds tolerance of 8 V, and operates across a common mode range of 0---30 V achieving less than 10 nV/ $$ \sqrt {\text{Hz}} $$ of flicker noise at 100 Hz. By using a semi-digital SI FIR filter, residual chopper ripple is suppressed by more than 7.5 mVpp from the base line of 8 mVpp, which is equivalent to 25 dB suppression.

Are posttranslational modifications of β2‐glycoprotein I markers for thrombotic risk? Are they triggers of autoimmunity?

Are posttranslational modifications of β₂‐glycoprotein I markers for thrombotic risk? Are they triggers of autoimmunity?