ADC Sampling Research Articles

The Electromagnetic Calorimetry of the PANDA Detector at FAIR

The PANDA collaboration at FAIR, Germany, will focus on undiscovered charm-meson states and glueballs in antiproton annihilations to study QCD phenomena in the non-perturbative regime. For fixed target experiments at the storage ring HESR a 4π-detector for tracking, particle ID and calorimetry is under development and construction to operate at high annihilation rates up to 20 MHz. The electromagnetic calorimeters are composed of a target spectrometer (EMC) based on PbWO4 crystals and a shashlyk-type sampling calorimeter at the most forward region. The EMC, comprising more than 15,000 crystals, is operated at a temperature of −25°C and read-out via large-area avalanche photo-diodes or vacuum phototriodes/tetrodes. The photo sensor signals are continuously digitized by sampling ADCs. More than 50% of the high quality PWO-II crystals are delivered and tested. The excellent performance with respect to energy, time and position information was determined over a shower energy range from 10 MeV up to 15 GeV by operating several prototype detectors. In addition, the concept of stimulated recovery has been investigated to recover radiation damage on- and off-line during the calorimeter operation. Besides the overall concept of the target spectrometer the response function of the shashlyk spectrometer down to photon energies even below 100 MeV is presented.

Trigger Performance Simulation of a High Speed ADC-Based TOF-PET Read-Out System

Monte Carlo simulations of a time-of-flight Positron Emission Tomography front end readout system (TOF-PET) are performed to investigate obtainable timing resolution at different ADC sample times using LYSO scintillators. Results from simulations with different combinations of ADC sample times and analog filter time constants are presented. To determine the coincidence resolving time (CRT), a trigger system based on a digital constant fraction zero crossing discriminator (CFD) is investigated. Such a trigger system would be suitable for running real time in a field-programmable gate array (FPGA). It is seen that below a certain sample time, the time resolution is limited by the scintillator and MPPC combination, and not the readout system.

Compressive sensing based sub-mm accuracy UWB positioning systems: A space–time approach

A key challenge to achieve very high positioning accuracy (such as sub-mm accuracy) in Ultra-Wideband (UWB) positioning systems is how to obtain ultra-high resolution UWB echo pulses, which requires ADCs with a prohibitively high sampling rate. The theory of Compressed Sensing (CS) has been applied to UWB systems to acquire UWB pulses below the Nyquist sampling rate. This paper proposes a front-end optimized scheme for the CS-based UWB positioning system. A Space-Time Bayesian Compressed Sensing (STBCS) algorithm is developed for joint signal reconstruction by transferring mutual a priori information, which can dramatically decrease ADC sampling rate and improve noise tolerance. Moreover, the STBCS and time difference of arrival (TDOA) algorithms are integrated in a pipelined mode for fast tracking of the target through an incremental optimization method. Simulation results show the proposed STBCS algorithm can significantly reduce the number of measurements and has better noise tolerance than the traditional BCS, OMP, and multi-task BCS (MBCS) algorithms. The sub-mm accurate CS-based UWB positioning system using the proposed STBCS-TDOA algorithm requires only 15% of the original sampling rate compared with the UWB positioning system using a sequential sampling method.

Implementation of a digital data readout system for double-sided silicon strip detectors for ion and alpha particle spectroscopy

The experimental investigation of superheavy elements, one of the prominent research areas of the GSI Helmholtzzentrum für Schwerionenforschung (GSI), has reached a region of short-lived nuclei with expected lifetimes of the order of 1 μs. As signal processing times for conventional analogue front-end electronics are typically longer than 10 μs, new developments are mandatory. Continuously sampling ADCs with virtually no dead time are presently being implemented for various signal processing applications in particle and photon spectroscopy. In this paper, a new flash-ADC based data acquisition system (DAQ) is presented. It has been tested using an a source and heavy ion reaction measurements at GSI's UNILAC accelerator facility. In addition, a novel analysis algorithm has been implemented thus increasing the sensitive area of the double-sided silicon strip detector (DSSD) in use.

An offset cancellation technique in a switched-capacitor comparator for SAR ADCs

An offset cancellation technique for a SAR (successive approximation register) ADC switched-capacitor comparator is described. The comparator is designed with a pre-amplifying and regenerative latching structure and realized in 0.18 μm CMOS. With the first stage preamplifier offset cancellation and low offset regenerative latching approach, the equivalent offset of the comparator is reduced to < 0.55 mV. By using the pre-amplifying and regenerative latching comparison mode the comparator exhibits low power dissipation. Under a 1.8 V power supply, with a 200 kS/s ADC sampling rate and 3 MHz clock frequency, a 13-bit comparison resolution is reached and less than 0.09 mW power dissipation is consumed. The superiority of this comparator is discussed and proved by the post-simulation and application to a 10 bit 200 kS/s touch screen SAR A/D converter.

A 0.013 ${\hbox {mm}}^{2}$, 5 $\mu\hbox{W}$, DC-Coupled Neural Signal Acquisition IC With 0.5 V Supply

We present an area-efficient neural signal-acquisition system that uses a digitally intensive architecture to reduce system area and enable operation from a 0.5 V supply. The architecture replaces ac coupling capacitors and analog filters with a dual mixed-signal servo loop, which allows simultaneous digitization of the action and local field potentials. A noise-efficient DAC topology and an compact, boxcar sampling ADC are used to cancel input offset and prevent noise folding while enabling “per-pixel” digitization, alleviating system-level complexity. Implemented in a 65 nm CMOS process, the prototype occupies 0.013 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> while consuming 5 μW and achieving 4.9 μVrms of input-referred noise in a 10 kHz bandwidth.

High-resolution ranging method based on low-rate parallel random sampling

In this paper, we propose a low-rate high-resolution ranging method for UWB (up to several GHz of sampling rate) ranging system. It exploits compressed sensing (CS) theory and a parallel sampling ADCs structure based on random projection (PSRP). To guarantee the effective application of CS on the received signal, we construct a dictionary in which the atoms are time-shifted versions of the transmitted signal. Hence the received signal can be low-rate sampled by PSRP. For an UWB ranging system using PSRP instead of the newly proposed analog-to-information converter, it possesses the universality of dictionary atoms, lower sampling rate and better performance for noisy signal. Additionally, since the dictionary size in this work can be adjusted flexibly, a desired high resolution can be achieved. The simulation results confirm these advantages via a noisy received signal (SNR=16 dB) which contains five target echoes. Though the received signal is sampled at less 10% of Nyquist rate, the probability of echo detection is over 95% and the distance resolution reaches the optimal of the conventional ranging method.

A Positron Emission Tomograph based on LSO-APD modules with a sampling ADC read-out system for a students’ advanced laboratory course

A one-day laboratory course on positron emission tomography (PET) for the education of physics students and PhD students in medical physics has been set up. In the course, the physical background and the principles of a PET scanner are introduced. Course attendees set the system in operation, calibrate it using a 22Na point source and reconstruct different source geometries filled with 18F. The PET scanner features an individual channel read-out of 96 lutetium oxyorthosilicate (LSO) scintillator crystals coupled to avalanche photodiodes (APD). The analog data of each APD are digitized by fast sampling analog to digital converters (SADC) and processed within field programmable gate arrays (FPGA) to extract amplitudes and time stamps. All SADCs are continuously sampling with a precise rate of 80MHz, which is synchronous for the whole system. The data is transmitted via USB to a Linux PC, where further processing and the image reconstruction are performed. The course attendees get an insight into detector techniques, modern read-out electronics, data acquisition and PET image reconstruction. In addition, a short introduction to some common software applications used in particle and high energy physics is part of the course.

VHDL implementation of feature-extraction algorithm for the PANDA electromagnetic calorimeter

A simple, efficient, and robust feature-extraction algorithm, developed for the digital front-end electronics of the electromagnetic calorimeter of the PANDA spectrometer at FAIR, Darmstadt, is implemented in VHDL for a commercial 16 bit 100 MHz sampling ADC. The source-code is available as an open-source project and is adaptable for other projects and sampling ADCs. Best performance with different types of signal sources can be achieved through flexible parameter selection. The on-line data-processing in FPGA enables to construct an almost dead-time free data acquisition system which is successfully evaluated as a first step towards building a complete trigger-less readout chain. Prototype setups are studied to determine the dead-time of the implemented algorithm, the rate of false triggering, timing performance, and event correlations.

OFDM 기반의 WLAN을 지원하는 디지털 IF단 설계

In this paper, we propose the design procedure of a digital IF system for the OFDM based WLAN system and examine its performances. Along with the decision procedure of ADC sample rate, NCO frequency and the required decimation ratio, we show the decimation ratio is accomplished through the use of a CIC filter and a MHBF. We also show that the amplitude distortion occurred in the decimation filters can effectively be compensated by a ISOP filter and an additional FIR filter, which leads to the reduction of the overall hardware complexity. Finally, we examine the BER performance of the proposed system and compare it with a theoretical one that excludes filter non-linearities.

Performance of the prototype of the electromagnetic calorimeter for PANDA

The PANDA collaboration at FAIR, Germany, will employ antiproton annihilations to investigate yet undiscovered charm-meson states and glueballs. The aim is to study QCD phenomena in the non-perturbative regime and to unravel the origin of hadronic masses. A multi-purpose detector for tracking, calorimetry and particle identification is presently being developed to run at high luminosities providing up to 2×107 interactions/s. One of the crucial components of the PANDA spectrometer is the Electromagnetic Calorimeter, composed of cooled PbWO4 crystals. This paper describes construction and performance of a fully functioning prototype of this calorimeter. The performance was determined from measurements exploiting cosmic muons and high-energy tagged photons from the MAMI-C electron accelerator. The response measurements were carried out using sampling ADCs and, for comparison, charge-integrating ADCs. The achieved results validate the usage of sampling ADCs with a moderate sampling frequency, provide the energy resolution as foreseen in the Technical Design Report of the full calorimeter, and secure event correlation by achieving a good timing resolution through digital analysis of the sampled signals.

Measuring the dependence of the decay curve on the electron energy deposit in NaI(Tl)

We report on the first measurement of the decay times of NaI(Tl) as a function of the deposited electron energy. It has been suggested that the decay curve depends on the ionization density, which is correlated with the electron energy deposit in the scintillator. The ionization creates excitation states, which can decay radiatively and non-radiatively through a number of competing processes. As a result, the rate at which the excitation decays depends on the ionization density. A measurement of the decay curve as a function of the ionization density will allow us to probe the kinetic rates of the competing processes. The Scintillator Light Yield Non-proportionality Characterization Instrument (SLYNCI) measures the electron response of scintillators utilizing fast sampling ADCs to digitize the raw signals from the detectors, and so can provide a measurement of the light pulse shape from the scintillator. Using data collected with the SLYNCI instrument, the intrinsic scintillation profile is extracted on an event-by-event basis by deconvolving the raw signal with the impulse response of the system. Scintillation profiles with the same electron energy deposit are summed to obtain decay curves as a function of the deposited electron energy. The decay time constants are obtained by fitting the decay curves with a two-component exponential decay. While a slight dependence of the decay time constants on the electron energy deposit is observed, the results are not statistically significant.

Front-End Electronics and Feature-Extraction Algorithm for the PANDA Electromagnetic Calorimeter

The PANDA collaboration at FAIR, Germany, will employ antiproton annihilations to investigate yet undiscovered charm-mesons and glueballs aiming to unravel the origin of hadronic masses. A multi-purpose detector for tracking, calorimetry and particle identification is presently being developed to run at high luminosities providing up to 2.107 interactions/s. A trigger-less data-acquisition system will be employed with sub-detectors continuously providing data from incoming physics events. This paper describes readout electronics and the treatment of the digitised preamplifier signal for the Electromagnetic Calorimeter. The use of a Sampling ADC in the readout allows to achieve the design goals, namely a large dynamic range from 1 MeV to 10 GeV, a count-rate dependent low trigger threshold of about 1-3 MeV, and a time resolution better than 1 ns.

Development of a Neutral Beam Profile Monitor

We developed a novel beam profile monitor for measuring the shape of an intense neutral beam for particle physics. This monitor is based on a detector technology of scintillating fibers, photomultiplier tubes, and sampling ADCs. It has an advantage for its simplicity, reliability, flexibility, and versatility. This monitor was installed in the small-diameter neutral beam for the KL0 →π0 νν experiment at J-PARC. We report in this article the development and performance of this monitor.

A 30 $\mu$W Analog Signal Processor ASIC for Portable Biopotential Signal Monitoring

This paper presents the design and implementation of an analog signal processor (ASP) ASIC for portable ECG monitoring systems. The ASP ASIC performs four major functionalities: 1) ECG signal extraction with high resolution, 2) ECG signal feature extraction, 3) adaptive sampling ADC for the compression of ECG signals, 4) continuous-time electrode-tissue impedance monitoring for signal integrity monitoring. These functionalities enable the development of wireless ECG monitoring systems that have significantly lower power consumption yet that are more capable than their predecessors. The ASP has been implemented in 0.5 μm CMOS process and consumes 30 μW from a 2 V supply. The noise density of the ECG readout channel is 85 nV/√Hz and the CMRR is better that 105 dB. The adaptive sampling ADC is capable of compressing the ECG data by a factor of 7 and the heterodyne chopper readout extracts the features of the ECG signals. Combination of these two features leads to a factor 4 reduction in the power consumption of a wireless ECG monitoring system. Furthermore, the proposed continuous-time impedance monitoring circuit enables the monitoring of the signal integrity.

First tests of multipurpose spectrometer

A new standalone compact spectrometer has been developed. It is based on the digital signal processor, sampling ADC and contains other components needed for spectra processing (i.e. RAM, Flash/ROM, real time clock, power supply block). Spectrometer is connected with a PC via high-speed USB 2.0 bus. It is designed as a multipurpose device, which is planned to be used for many applications such as measurements of Rn activities, energy of detected particles by CdTe pixel detector or for coincidence measurements. Results of the first spectroscopic tests (with Am+Pu+Cm alpha source, measurements of Rn progenies) are presented.

Multifrequency simultaneous bioimpedance measurements using multitone burst signals for dynamic tissue characterization

In this paper we present the keypoints to perform multifrequency simultaneous bioimpedance measurements using multitone signals. Concerning the frequency distribution, tones are spread over 1kHz to 1MHz range using a custom frequency distribution which we called Bilateral Quasi Logarithmic (BQL). BQL concentrates a higher number of tones around the impedance relaxation and contains a frequency plan algorithm. It minimizes the intermodulation effects due to non-linearities behaviours of the DUT and electrodes by slightly shifting the original tones in order to guarantee a guard bandwith. Regarding the multitone phase distribution, a Genetic Algorithm (GA) has been developed to minimize multitone Crest Factor (CF). This allow us to maximize the resultant Signal to Noise Ratio (SNR) of the acquisition system. This paper also presents the relation between parameters such as sampling frequency and ADC bits with the SNR and the effect in the overall amplitude and phase error when using multitone signals as excitation waveforms. Finally, we present characterization results from a measurement system based on a modular PXI architecture.

Development of a 1 GS/s high-resolution sampling ADC system

Today, many experiments in high energy physics have to handle data rates of several MHz per readout channel to reach statistical significance for the measured quantities. In addition, these experiments frequently have to deal with short analog pulses of a few nanoseconds length which may cover large dynamic ranges and which require amplitude as well as time measurements with highest accuracy. For applications of this kind fast transient recorders with very high resolution and deep on-board memory are the first choice. We have built a 16-channel 12- or 14-bit single unit VME64x/VXS sampling ADC module which may sample at rates up to 1GS/s. Fast algorithms have been developed and successfully tested on scintillating counter detectors to implement pulse shape discrimination, constant fraction timing and gated integration.

Focus on test and measurement

Focus on test and measurement

Static and dynamic test of high resolution DAC based on over sampling and low resolution ADC

The problem of the signal acquisition with high resolution and linearity for static and dynamic characterization of high resolution DACs is shifted into the problem of high speed signal acquisition at lower resolution. High speed low resolution ADC is used to over sample the signal sum of output voltage of the DAC under test and periodic reference voltage. Two different reference signals are used: sinusoidal for static test, and sawtooth for dynamic test. DAC output is reconstructed by means of the reference signal evaluated in the zero crossing sequence detected on the resulting signal. Because the reconstructed signal is non-uniformly time sampled, the spectral analysis is performed by adapting the procedure pointed out to reconstruct the uniformly sampled spectrum from the non-uniformly sampled one. Numerical tests confirm the advantages in term of higher accuracy in comparison with others methods.