Analog Signal Processing Research Articles

HV-CMOS detectors in BCD8 technology

This paper presents the first pixel detector realized using the BCD8 technology of STMicroelectronics. The BCD8 is a 160 nm process with bipolar, CMOS and DMOS devices; mainly targeted for an automotive application. The silicon particle detector is realized as a pixel sensor diode with a dimension of 250 × 50 μm2. To support the signal sensitivity of pixel diode, the circuit simulations have been performed with a substrate voltage of 50 V. The analog signal processing circuitry and the digital operation of the circuit is designed with the supply voltage of 1.8 V. Moreover, an analog processing part of the pixel detector circuit is confined in a unit pixel (diode sensor) to achieve 100 % fill factor. As a first phase of the design, an array of 8 pixels and 4 passive diodes have been designed and measured experimentally. The entire analog circuitry including passive diodes is implemented in a single chip. This chip has been tested experimentally with 70 V voltage capability, to evaluate its suitability. The sensor on a 125 Ωcm resistivity substrate has been characterized in the laboratory. The CMOS sensor realizes a depleted region of several tens of micrometer. The characterization shows a uniform breakdown at 70 V before irradiation and an approximate capacitance of 80 fF at 50 V of reverse bias voltage. The response to ionizing radiation is tested using radioactive sources and an X-ray tube.

A Novel All-Pass Network Implementation for Improved Group Delay Performance

In this letter, a novel all-pass network implementation is proposed using both distributed and lumped elements for high group delay. The implementation has reduced footprint and sensitivity of the group delay performance to the specified component value tolerances. It has been experimentally verified and the measured group delay is 2.4 ns at 1.85 GHz, which is thrice that reported in other approaches. The circuit finds varied applications in high resolution analog signal processing.

SSDCα – Inherently robust integrated biomimetic sensor-to-spike-to-digital converter based on peripheral neural ensembles

Abstract Rethinking analog to digital conversion has become extremely crucial in the race towards aggressively scaled technology nodes with decaying signal swings. The concept of more recent TDCs, which are completely designed in digital domain, make them simpler, easier to manufacture and faster to market. In previous work, LUCOS J. Doge, G. Schonfelder, G. Streil, and A. Konig. An HDR CMOS image sensor with spiking pixels, pixel-level ADC, and linear characteristics. Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on, 49(2):155–158, Feb 2002. , a high dynamic range image sensor using spike based processing with high pixel uniformity had been designed. This motivated a generic ADC concept, which makes use of spike processing, to design a highly effective sensor signal processing system, which carries the promise of robustness to technology scaling, for effective use in IoT and Industrie 4.0. In this work, an ADC concept based on acoustic localization in biological sensory systems has been pursued. An ADC has been designed based on this concept using biological models of spiking neurons. The first proof-of-concept prototype chip SSDCα has been designed in ams 350 nm technology node with area of the chip is 8.5 mm2, sampling rate from DC to 150 kHz, resolution from 8-bit to 13-bit, with 28, 200 transistors, 263 neurons and 517 synapses. The future work will move from 350 nm to 90 nm technology node to show the improvement and robustness of the SSDC with technology scaling.

Impact of Temperature Variation on Resonant Frequency of Active Grounded Inductor-based Bandpass Filter

Objective: This paper proposes an electronically tunable active grounded inductor circuit using VDVTA as a new active element. The circuit can replace spiral passive inductors for all Analog Signal Processing and data communications operations. Method/Analysis: The impact of temperature variation on its resonant frequency is investigated using Virtuoso Analog Design Environment of Cadence @ 45-nm CMOS technology node. Findings: This paper carries out a study on CMOS realization of Voltage Differencing Voltage Transconductance Amplifier (VDVTA) and its application as an active grounded inductor. A Bandpass filter circuit is realized using the VDVTA based grounded inductor. Furthermore, the impact of temperature variation on the response of the bandpass filter is analyzed and presented. Novelty/Improvement: The proposed circuit uses only active elements and a grounded capacitor. Due to this, the circuit finds applications in all canonical operations and integrated circuit implementations.

High-resolution, dual-depth spectral-domain optical coherence tomography with interlaced detection for whole-eye imaging.

Dual-depth spectral-domain optical coherence tomography (SD-OCT) enables high-resolution in vivo whole-eye imaging. Two orthogonally polarized beams from a source are focused simultaneously on two axial positions of the anterior segment and the retina. For the detector arm, a 1×2 ultrafast optical switch sequentially delivers two spectral interference signals to a single spectrometer, which extends the in-air axial depth range up to 9.44 mm. An off-pivot complex conjugate removal technique doubles the depth range for all anterior segment imaging. The graphics-processing-unit-based parallel signal processing algorithm supports fast two- and three-dimensional image displays. The obtained high-resolution anterior and retinal images are measured biometrically. The dual-depth SD-OCT system has an axial resolution of ∼6.4 μm in air, and the sensitivity is 91.79 dB at 150 μm from the zero-delay line.

Operational Amplifier Circuits with Oxide Thin Film Transistors

Amorphous silicon thin film transistors (TFTs) have been used widely due to good uniformity and low process cost. However, They are not suitable for a circuit due to the low carrier mobility. Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistor (a-IGZO TFT) exhibits higher mobility and lower leakage current than amorphous silicon TFT and it is common to use only n-type a-IGZO TFT due to a poor electrical property of p-type TFT. In this paper, we developed operational amplifier (op-amp) circuit using only the n-type a-IGZO TFTs. Recently, medical device circuits for measuring bio-signals are being implemented on a wearable devices. Oxide TFTs are suitable for the integrated circuit for such applications. The analog signal processing such as amplification, and filtering of much noise are necessary for analog electrical signals introduced from bio-sensors. The op-amp is most widely used amplifiers due to ideal linear performance characteristics. An op-amp is composed of two input voltages (+Vin, -Vin), two power supply voltages (+VDD, -VDD) and one output voltage (Vout). It amplifies the voltage difference between the two input voltages of the non-inverting and inverting inputs (+Vin, -Vin). The op-amp with a-IGZO TFTs has lower gain than that of the op-amp by CMOS process and need increase of the gain by cascaded amplifier stages. We developed a single power supply (+VDD = +15V) OP amp with improved gain. The circuit is composed of three stages: the first is differential amplifier(T1~T8) of input stage, the second is common-source amplifier(T9~T17), and the third is output buffer(T18~T19) of the output stage. The differential amplifier of the first stage amplified the differential voltage for given input signals (+Vin, -Vin). The output voltage was amplified at the common-source amplifier stage of the second stage. Common-source amplifiers were used for a large voltage gain. After optimization of the circuits, the input voltage of 0.05V was amplified to about 13V.

Enhanced Bandwidth and Diversity in Real-Time Analog Signal Processing (R-ASP) Using Nonuniform C-Section Phasers

We show that a continuously nonuniform coupled-line C-section phaser, as the limiting case of the step-discontinuous coupled-line multisection commensurate and non-commensurate phasers, provides enhanced bandwidth and diversity in real-time analog signal processing (R-ASP). The phenomenology of the component is explained in comparison with the step-discontinuous using multiple-reflection theory and a simple synthesis procedure is provided. The bandwidth enhancement results from the suppression of spurious group delay harmonics or quasi-harmonics, while the diversity enhancement results from the greater level of freedom provided by the continuous nature of the nonuniform profile of the phaser. These statements are supported by theoretical and experimental results.

Thermal noise limit for time‐domain analogue signal processing in CMOS technologies

The impact of thermal noise in voltage- and time-domain analogue signal processing is discussed. Despite the technology scaling allows to resolve smaller time differences, it will be shown that in CMOS technologies voltage signal processing have a better fundamental limit compared with its time counterpart.

On an analogue signal processing circuit in the Nematode C. elegans.

In this work we will work on analogue signal processing in the neural circuit of C. elegans which is able to detect the analogue signals from the environment and produce locomotive behaviours which are in accordance with experiments. The signals in C. elegans are processed in a purely analogue procedure, since no action potential has been recorded in its neural activity. We aim to show how signal processing can be executed in analogue domain in a living creature. In order to do that we will model two different behaviours of C. elegans which are generated in the same network of neurons, klinotaxis behaviour and isothermal tracking. We will implement a Genetic Algorithm to find appropriate sets of parameters of the model. Our contribution is to show how relatively straight forward differential equations can lead to relatively complex and different behaviours.

Reconfigurable analog classifier for knee-joint rehabilitation.

We present a System-On-Chip Field Programmable Analog Array (FPAA) for analyzing and processing the signals off an accelerometer for a wearable joint health assessment device. FPAAs have been shown to compute with an efficiency of 1000 times, as well as area efficiencies of 100 times, more than digital solutions. This work presents a low power signal processing system which allows us to extract features from the output of the accelerometer. These features are used by the classifier, implemented using a vector matrix multiplication and a two output 1-winner-take-all, to detect flexion and extension cycles in the subject. The compiled design consumes 0.636 μW of power for the front end analog signal processing chain where as the single layer classifier uses 13 μW of power. Thus the system is highly suitable for wearable applications where power consumption is a major concern. The current FPAA is fabricated in a 0.35 μm CMOS process and is operated at a power supply of 2.5 volts. The Gm-C filters and other circuits are operated in the subthreshold regime of the transistor to obtain the highest transconductance to current ratio offered by the process.

Poster - 01: LabPET II Pixelated APD-Based PET Scanner for High-Resolution Preclinical Imaging

Purpose: LabPET II is a new generation APD-based PET scanner designed to achieve sub-mm spatial resolution using truly pixelated detectors and highly integrated parallel front-end processing electronics. Methods: The basic element uses a 4×8 array of 1.12×1.12 mm2 Lu1.9Y0.1SiO5:Ce (LYSO) scintillator pixels with one-to-one coupling to a 4×8 pixelated monolithic APD array mounted on a ceramic carrier. Four detector arrays are mounted on a daughter board carrying two flip-chip, 64-channel, mixed-signal, application-specific integrated circuits (ASIC) on the backside interfacing to two detector arrays each. Fully parallel signal processing was implemented in silico by encoding time and energy information using a dual-threshold Time-over-Threshold (ToT) scheme. The self-contained 128-channel detector module was designed as a generic component for ultra-high resolution PET imaging of small to medium-size animals. Results: Energy and timing performance were optimized by carefully setting ToT thresholds to minimize the noise/slope ratio. ToT spectra clearly show resolved 511 keV photopeak and Compton edge with ToT resolution well below 10%. After correction for nonlinear ToT response, energy resolution is typically 24±2% FWHM. Coincidence time resolution between opposing 128-channel modules is below 4 ns FWHM. Initial imaging results demonstrate that 0.8 mm hot spots of a Derenzo phantom can be resolved. Conclusion: A new generation PET scanner featuring truly pixelated detectors was developed and shown to achieve a spatial resolution approaching the physical limit of PET. Future plans are to integrate a small-bore dedicated mouse version of the scanner within a PET/CT platform.

Analog Signal Derivation in the Programmable Logical Controller

Programmable logical controllers (PLC) find ever-widening applications in technological processes of ground operating equipment. Their computing capacity allows additional processing of analogue signals coming from the sensors of physical quantities. In particular, PLC hardware and software enable us to calculate the first derivative of an analogue signal in order to improve the control or prediction quality of the process under control. The aim is to research the singularities in calculating the first derivative of an analogue signal using the SIMATIC S7-200 PLC of Siemens Company. A method of digital differentiation has been decided on the algorithm based on a derivative representation by a final number of return differences of consecutive readout in regular intervals of continuous function. Such an algorithm allows us to find comprehensible accuracy in calculation of the first derivative of an analogue signal in PLC when using the first and second differences of readout. Thus, a choice of the period of digitization of differentiated process is also of great importance. Research of the differentiation process, based on mathematical models of aperiodic chains of the first and second orders, has shown that for used PLC a digitization period should not be less than 50msес. The natural experiment has shown that calculation of the first derivative of a signal from the temperature sensor allows an essential increase in speed of PLC response to the abrupt change of the measured quantity. The research results have shown that SIMATIC S7-200 PLC allow us to provide sufficient accuracy and speed in calculating the first derivative of the low-frequency analogue signals, being specific, for example, for re-fuelling systems or systems of temperature stabilization. The received results are of interest for experts in the field of development and operation of technological systems of the ground operating equipment.

Feed-forward and reciprocal inhibition for gain and phase timing control in a computational model of repetitive cough.

We investigated the hypothesis, motivated in part by a coordinated computational cough network model, that second-order neurons in the nucleus tractus solitarius (NTS) act as a filter and shape afferent input to the respiratory network during the production of cough. In vivo experiments were conducted on anesthetized spontaneously breathing cats. Cough was elicited by mechanical stimulation of the intrathoracic airways. Electromyograms of the parasternal (inspiratory) and rectus abdominis (expiratory) muscles and esophageal pressure were recorded. In vivo data revealed that expiratory motor drive during bouts of repetitive coughs is variable: peak expulsive amplitude increases from the first cough, peaks about the eighth or ninth cough, and then decreases through the remainder of the bout. Model simulations indicated that feed-forward inhibition of a single second-order neuron population is not sufficient to account for this dynamic feature of a repetitive cough bout. When a single second-order population was split into two subpopulations (inspiratory and expiratory), the resultant model produced simulated expiratory motor bursts that were comparable to in vivo data. However, expiratory phase durations during these simulations of repetitive coughing had less variance than those in vivo. Simulations in which reciprocal inhibitory processes between inspiratory-decrementing and expiratory-augmenting-late neurons were introduced exhibited increased variance in the expiratory phase durations. These results support the prediction that serial and parallel processing of airway afferent signals in the NTS play a role in generation of the motor pattern for cough.

A debugging system for azimuthally acoustic logging tools based on modular and hierarchical design ideas

On the basis of modular and hierarchical design ideas, this study presents a debugging system for an azimuthally sensitive acoustic bond tool (AABT). The debugging system includes three parts: a personal computer (PC), embedded front-end machine and function expansion boards. Modular and hierarchical design ideas are conducted in all design and debug processes. The PC communicates with the front-end machine via the Internet, and the front-end machine and function expansion boards connect each other by the extended parallel bus. In this method, the three parts of the debugging system form stable and high-speed data communication. This study not only introduces the system-level debugging and sub-system level debugging of the tool but also the debugging of the analogue signal processing board, which is important and greatly used in logging tools. Experiments illustrate that the debugging system can greatly improve AABT verification and calibration efficiency and that, board-level debugging can examine and improve analogue signal processing boards. The design thinking is clear and the design structure is reasonable, thus making it easy to extend and upgrade the debugging system.

A wideband linear tunable CDTA and its application in field programmable analogue array

In this paper, a NMOS-based wideband low power and linear tunable transconductance current differencing transconductance amplifier (CDTA) is presented. Based on the NMOS CDTA, a novel simple and easily reconfigurable configurable analogue block (CAB) is designed. Moreover, using the novel CAB, a simple and versatile butterfly-shaped FPAA structure is introduced. The FPAA consists of six identical CABs, and it could realize six order current-mode low pass filter, second order current-mode universal filter, current-mode quadrature oscillator, current-mode multi-phase oscillator and current-mode multiplier for analog signal processing. The Cadence IC Design Tools 5.1.41 post-layout simulation and measurement results are included to confirm the theory.

The Digital Fields Board for the FIELDS instrument suite on the Solar Probe Plus mission: Analog and digital signal processing

AbstractThe first in situ measurements of electric and magnetic fields in the near‐Sun environment (< 0.25 AU from the Sun) will be made by the FIELDS instrument suite on the Solar Probe Plus mission. The Digital Fields Board (DFB) is an electronics board within FIELDS that performs analog and digital signal processing, as well as digitization, for signals between DC and 60 kHz from five voltage sensors and four search coil magnetometer channels. These nine input signals are processed on the DFB into 26 analog data streams. A specialized application‐specific integrated circuit performs analog to digital conversion on all 26 analog channels simultaneously. The DFB then processes the digital data using a field programmable gate array (FPGA), generating a variety of data products, including digitally filtered continuous waveforms, high‐rate burst capture waveforms, power spectra, cross spectra, band‐pass filter data, and several ancillary products. While the data products are optimized for encounter‐based mission operations, they are also highly configurable, a key design aspect for a mission of exploration. This paper describes the analog and digital signal processing used to ensure that the DFB produces high‐quality science data, using minimal resources, in the challenging near‐Sun environment.

A Chemical Instrumentation Course on Microcontrollers and Op Amps. Construction of a pH Meter

In a chemical instrumentation course, usually analog signal conditioning, data acquisition, and digital signal processing are taught. Analog boards for easy interconnection of operational amplifiers are now available that make an introduction to analog signal processing easier. The digitization process can be demonstrated with microcontrollers. The cost of microcontroller development boards has decreased, and now they represent a cost-efficient platform to clarify the process of data acquisition. In this paper, we show the construction of a pH meter, and, as the development progresses, the characteristics of operational amplifiers and microcontrollers are exposed in the hope of making the internal operation of modern instrumentation more transparent.

On Covering the Nodes of Circulant Networks and Its Applications

Coverage and security of network nodes are the critical issue in wireless sensor networks. The covering number is an essential tool in monitoring networks, as it gives the smallest number of detection devices needed to identify the location of an intruder or a malicious node. In this paper, we provide a graph theory based approach which could be beneficial to keep the network secure. The covering number for circulant networks are calculated exactly and their theoretical properties are explored in this article. Circulant networks have a broad range of applications in parallel computing and signal processing because of its increased connectivity. The minimal vertex covering set of a network serves as its back bone in the process of routing.

Design of Secure ECG-Based Biometric Authentication in Body Area Sensor Networks.

Body area sensor networks (BANs) utilize wireless communicating sensor nodes attached to a human body for convenience, safety, and health applications. Physiological characteristics of the body, such as the heart rate or Electrocardiogram (ECG) signals, are promising means to simplify the setup process and to improve security of BANs. This paper describes the design and implementation steps required to realize an ECG-based authentication protocol to identify sensor nodes attached to the same human body. Therefore, the first part of the paper addresses the design of a body-area sensor system, including the hardware setup, analogue and digital signal processing, and required ECG feature detection techniques. A model-based design flow is applied, and strengths and limitations of each design step are discussed. Real-world measured data originating from the implemented sensor system are then used to set up and parametrize a novel physiological authentication protocol for BANs. The authentication protocol utilizes statistical properties of expected and detected deviations to limit the number of false positive and false negative authentication attempts. The result of the described holistic design effort is the first practical implementation of biometric authentication in BANs that reflects timing and data uncertainties in the physical and cyber parts of the system.

Direct Digital Demultiplexing of Analog TDM Signals for Cable Reduction in Ultrasound Imaging Catheters.

In real-time catheter-based 3-D ultrasound imaging applications, gathering data from the transducer arrays is difficult, as there is a restriction on cable count due to the diameter of the catheter. Although area and power hungry multiplexing circuits integrated at the catheter tip are used in some applications, these are unsuitable for use in small sized catheters for applications, such as intracardiac imaging. Furthermore, the length requirement for catheters and limited power available to on-chip cable drivers leads to limited signal strength at the receiver end. In this paper, an alternative approach using analog time-division multiplexing (TDM) is presented, which addresses the cable restrictions of ultrasound catheters. A novel digital demultiplexing technique is also described, which allows for a reduction in the number of analog signal processing stages required. The TDM and digital demultiplexing schemes are demonstrated for an intracardiac imaging system that would operate in the 4- to 11-MHz range. A TDM integrated circuit (IC) with an 8:1 multiplexer is interfaced with a fast analog-to-digital converter (ADC) through a microcoaxial catheter cable bundle, and processed with a field-programmable gate array register-transfer level simulation. Input signals to the TDM IC are recovered with -40-dB crosstalk between the channels on the same microcoax, showing the feasibility of this system for ultrasound imaging applications.