Digital Signal Conversion Research Articles

Psychological stress recognition from heart rate variability parameters based on field programmable gate arrays.

Psychological stress is a big threat to people's health. Early detection of psychological stress is important. The design of a stress recognition device based on the ECG (electrocardiograph) signal is presented in this paper. The device features intelligence, precision, portability, fast response, and low power consumption. In the design, the ECG signals are acquired by the AD8232 ECG module and processed by a low power consumption FPGA (Field Programmable Gated Array) development board PYNQ-Z2. Meanwhile, a modified Deep Forest model named Aw-Deep Forest (Adaptive Weight Deep Forest) is proposed. The Aw-Deep Forest has better performance than the Deep Forest model because it improves the fitting quality of the forests. By implementing the Aw-Deep Forest model on the FPGA, the device can assess people's state of psychological stress by analyzing the HRV (heart rate variability) parameters from ECG data. This paper mainly introduces the detailed process of ECG signal collecting, filtering, analog signal to digital signal conversion, HRV parameter analysis, and psychological stress recognition with Aw-Deep Forest. The final accuracy is 81.39%.

Method for describing signal conversion processes in analog electronic systems

One of the main tasks of information technology is to improve existing and develop new methods for formal recording of various dynamic logical operations of analog and digital signal conversion in electronic control systems, acquisition, and processing of information. The stage of formal recording of any signal transformation process must be presented in the form of analytic symbols, the sequence of which must form a fully functional mathematical model. The improved method of the signals conversion processes description based on a representation of the mathematical models of the electronic circuits’ components in the grapho-analytical form with the increased information content allows integrating the developed models of electronic circuit elements with object-oriented programming language in the form of functional structures. It opens the way to perform parametric analysis of circuits and other tasks, related to the modeling of electronic systems.

Correction of errors and harmonic distortion in pulse-width modulation of digital signals

Pulse-Width (PW) modulation is widely used in those applications where an analog or digital signal has to be encoded in the time domain as a binary stream, such as switched-mode power amplifiers in transmitters of modern telecommunication standards, high-resolution digital signal conversion using single-bit digital-to-analog converters, and many others. Due to the fact that digital signals are sampled in the time domain, the quality of the resulting PW modulated waveforms is worsened by harmonic distortion. Multilevel PW modulation has been proposed to reduce these adverse effects, but the modulated waveform is no longer binary. In this paper, the mechanisms by which harmonic distortion is produced are analyzed. As a result, the distortion terms are mathematically quantified and used to correct the errors. Note that a correction network based on a simple subtraction of the distortion terms from the PW modulated signal would produce a waveform that would no longer be binary. The proposed correction network is implemented in the digital domain and, by means of a sigma-delta modulator, preserves the binary feature of the PW modulated output.

Preliminary results of measurements obtained from a low-cost arduino-based surface weather data acquisition system for radio meteorology

Surface weather monitoring is crucial for radio meteorology, agricultural, communication, and industrial processes. However, there is a dearth of weather data in Ede, Osun State, Nigeria (Lat 7.736° N, Lon 4.435° E). The proposed weather monitoring system used the Arduino Mega2560 microcontroller to measure, record and display the atmospheric parameters. Analog sensors for pressure, temperature, relative humidity, and wind speed were interfaced with the microcontroller through an ADC for digital signal conversion and data logging. An LCD connected to the microcontroller displays the measured parameters. The weather data were stored in excel format on a microSD card. The data were compared with that of a nearby weather station. The plots showed a close agreement with the data collected from the nearby station. The system eliminates the need for extra cost baud rate and expensive third-party software for interfacing. Besides, there is no need for an internet connection for configuration. Hence, this data acquisition system (DAS) could be a better choice in cost and maintenance than the off-the-shelf weather stations. The DAS was programmed to derive the surface radio refractivity from the meteorological parameters and the corresponding radio refractivity gradients over Ede.

АПАРАТНО-ПРОГРАМНА ВБУДОВАНА СИСТЕМА ЧАСТОТНОЇ СЕЛЕКЦІЇ СИГНАЛУ НА ОСНОВІ ГІРАТОРА

The work is devoted to the problem of frequency-selective signal conversion in microelectronic sensor devices. It has been shown that the signal path of such devices, in particular, sensor nodes in the concept of the Internet of Things, must meet the requirements of embedded systems using a mixed analog-digital front end. The analysis of the signal transformation of photovoltaic sensors, in particular the problem of a significant parasitic influence of extraneous non-informative optical radiation and electromagnetic interference, has been carried out. SPICE models of photovoltaic sensor signal circuits providing frequency selection on bandwidth filters have been synthesized. The main approaches of hardware-software implementation of the built-in system of frequency selection with the mixed-signal transformation are considered. The signal path of the embedded system includes a gyrator, a software-controlled amplifier, a synchronous demodulator, an analog-to-digital converter, and a digital filter. The implementation is carried out on the platform of the programmable system on a PSoC chip. The integrated circuits of the PSoC 5 LP Family Cypress Semiconductor Corporation are used with a wide range of programmable analog front-end nodes, in particular operating amplifiers, comparators, units on switching capacitors, reference voltage sources on the principle of the forbidden zone, analog multiplexers, signal synthesizers, etc. The efficiency of the mixed analog and digital signal conversion is shown.

Implementation of Global System for Mobile Communication-Based Smart Weather Monitoring System for Agricultural Environment

A weather station can be described as an instrument or device, which provides us information about weather in our surrounding environment. For example, it can provide us with details about the surrounding temperature, moisture, humidity, etc. Hence, this device basically senses temperature, moisture, humidity, leaf wetness, etc. There are various types of sensors are used, which measured the above-mentioned parameters. A device for real-time weather monitoring is presented to monitor the real-time temperature, the relative humidity of the atmosphere, leaf wetness of leaf, and moisture of soil via global system for mobile communication (GSM) network, using analog and digital components. The analog outputs of the sensors are connected to a PIC microcontroller through an ADC for digital signal conversion. A liquid crystal display (LCD) is also connected to the PIC microcontroller to display the measurements. For analysis and archiving purposes, the data can be transferred over GSM and received by a number of mobile users. The weather monitoring system can either be wired or a wireless one. In the case of wireless communication, the connectivity will be more user-friendly and weather monitoring would not require the physical presence of the person at the remote location.

Comparison of Radio Interferometers with Analog and Digital Extraction of Recorded Signal

Introduction. Radio telescopes of Very Long Baseline Interferometry (VLBI) networks usually record several signals with relatively narrow (up to 32 MHz) bands, which are extracted by means of base band converters (BBC) from an analog noise signal of an intermediate frequency (IF) with bands up to 1 GHz. When processing data, frequency band synthesis is used. At new small radio telescopes (for example, RT-13), directly wideband IF signals are digitized. An ability to connect the RT-13 radio telescope to the “Quasar” VLBI complex and to international VLBI networks provides by a digital narrow-band signal extraction module developed in 2019.Aim. Determining the measuring accuracy of an interferometric group delay of a signal by a radio interferometer with a digital narrow-band signal extraction module and comparing the sensitivity of interferometers with analog and digital signal extraction systems.Materials and methods. Sensitivity losses of interferometers with different systems for detecting recorded signals were calculated. The accuracy of a multi-channel interferometer with the synthesis of a frequency band and of an interferometer with recording of digital broadband IF signals without band synthesis was compared. The results were confirmed by VLBI observations in the observatories of the “Quasar” complex.Results. When replacing the analog system of signal extraction with digital system the sensitivity losses of the interferometer were slightly reduced. The measurement accuracy of the interferometric group delay had not changed. Accuracy increased when digitally recording broadband IF signals and when synthesizing a frequency band significantly larger than the IF bandwidth. Conditions and minimum synthesized bands were determined under which the accuracy of the interferometer with the registration of narrowband signals can be higher than the accuracy of the interferometer with the registration of wideband IF signals.Conclusion. The problem of combining RT-13 radio telescopes with VLBI networks with recording of video frequency signals was solved. The efficiency of the installation of digital signal conversion systems at radio telescopes was shown.

Analog to Digital Converters (ADC): A Literature Review

The signal processing is advancing day by day as its needs and in wireline/wireless communication technology from 2G to 4G cellular communication technology with CMOS scaling process. In this context the high-performance ADCs, analog to digital converters have snatched the attention in the field of digital signal processing. The primary emphasis is on low power approaches to circuits, algorithms and architectures that apply to wireless systems. Different techniques are used for reducing power consumption by using low power supply, reduced threshold voltage, scaling of transistors, etc. In this paper, we have discussed the different types and different techniques used for analog to digital conversion of signals considering several parameters.

Tactile Phonetics and Digital Impressions to Assist the Hearing and Visual Impaired

“Touch to Feel” is a method consistent with natural behavior and responses. It is commonly prevalent in the living, human and animals alike. With a digital conversion of the signals, more accurate and compressed data can be transmitted to the recipient. A small test was conducted on children with hearing disability and without any training or understanding, in front of public; they were able to identify the digital conversion of phonetic signals presented in a tactile format and matched it easily with the corresponding sentences and words. The purpose of this project was to find means to alleviate the struggle of the disabled to connect with the society with clear understanding and find a normal life in their current environment. Sign language does not give the hearing impaired to connect with all neither do the visually impaired are clearly able to perceive their surroundings. A new method of impression for digital data would help both kinds of disability to efficiently address the issue and improve their perception and understanding of their environment, people and knowledge acquisition methods, so that they a fair opportunity to lead a normal life.

Signal Synchronization, Collection and Transmission for Multichannel Distribution Seismic Antenna

Creation of seismic antennas involves production of a system capable to provide synchronous analog-to- digital data signal conversion of all channels and to broadcast digitized signals to the central computing complex (CCC). The article considers a structure of data transmission system from a big number of sources for application in seismic antennas. Moreover, it provides possible ways of preprocessing equipment (PE) unit arrangement in separate hermetic blocks to facilitate their replacement. Besides, the options for PE unit structural and functional schemes are offered. Application of specific chips is explained. The review of the most widespread types of digital convertors is given and the optimal one is chosen for application in hydro acoustic complexes. The option of synchronization with the use of phase-locked loop PLL units is offered. Configuration of data transmission system with the use of Ethernet switchboard setting optimal data transmission protocol is considered.

The Design of a Single-Bit CMOS Image Sensor for Iris Recognition Applications.

This paper presents a single-bit CMOS image sensor (CIS) that uses a data processing technique with an edge detection block for simple iris segmentation. In order to recognize the iris image, the image sensor conventionally captures high-resolution image data in digital code, extracts the iris data, and then compares it with a reference image through a recognition algorithm. However, in this case, the frame rate decreases by the time required for digital signal conversion of multi-bit digital data through the analog-to-digital converter (ADC) in the CIS. In order to reduce the overall processing time as well as the power consumption, we propose a data processing technique with an exclusive OR (XOR) logic gate to obtain single-bit and edge detection image data instead of multi-bit image data through the ADC. In addition, we propose a logarithmic counter to efficiently measure single-bit image data that can be applied to the iris recognition algorithm. The effective area of the proposed single-bit image sensor (174 × 144 pixel) is 2.84 mm2 with a 0.18 μm 1-poly 4-metal CMOS image sensor process. The power consumption of the proposed single-bit CIS is 2.8 mW with a 3.3 V of supply voltage and 520 frame/s of the maximum frame rates. The error rate of the ADC is 0.24 least significant bit (LSB) on an 8-bit ADC basis at a 50 MHz sampling frequency.

On Time Assist for Victims Trapped in Collapsed Building Enhanced with IOT Technology

Objectives: To increase the chances of saving the victims under debris especially those trapped under collapsed building. Methods: Technology used in this project is Internet of Things (IOT); through this technology the information about the victim trapped under debris is collected and stored in internet which is used for future use. A separate website is created to store the information about the workers in and out time and a GPS system is used to identify the victim location Findings: The simulation result explains about the latitude and longitude position of victim under rubble, Employer Id and the status of the victim under rubble. While comparing with the existing system the ARM processor is used where the analog to digital signal conversion is faster while comparing with PIC microcontroller, the information stored about the victim is useful for future purpose. Applications: Improvement is to reduce the size of the hardware and weight of the hardware. It is mainly applicable for saving the victims' life under collapsed building and under rubble.

A multifunctional digital converter for radio-astronomy signals with a bandwidth of up to 512 MHz

A multifunctional digital signal converter is described, which is used as a channel for the digital conversion and formatting of radio-interferometric signals with bandwidths of up to 512 MHz. The converter allows changes in its function by only a change in the control program, which is administered by the radio-telescope computer. The multifunctional computer can be used for radiometric and spectral measurements and for tests of the receiving–amplifying equipment of the radio telescope.

Multichannel analog front-end and analog-to-digital converter ICs for silicon photomultipliers

Integrated circuit (IC) of multichannel analog front-end and a mixed-signal chip of multichannel analog-to-digital converter are presented. A chipset of these two ICs is intended for readout, analog preprocessing and analog to digital conversion of silicon photomultiplier array signals. The number of channels of the analog front-end IC as well as the types of their input stages depends on the application. The current test version of the chip contains three current-input channels and three voltage-input channels. Each of the channels includes a programmable pre-amplifier, integrator with baseline-holder, code-controlled amplifier, amplitude discriminator, two programmable timers, pulse-shaping low-pass filter, peak detector, and an output buffer with baseline tuning circuitry. The analog IC has code-configurable architecture. The mixed-signal IC includes nine main channels and one auxiliary channel, containing 10-bit analog-to-digital converter in each channel. It also has a buffer memory and a voltage reference. The chip features low power consumption, which is less than 0.5 mW per channel at a sampling rate of 100 kHz. Both ICs are implemented in 0.35 μm CMOS technology.

FPGA Based Implementation of Gain Control Block for OFDM System

In the OFDM (Orthogonal Frequency Division Multiplexing) system, the fast synchronization is required which in general could be achieved using the preamble located in the header part of the data packet. The modulated and transmitted signal experiences the frequency selective fading due to the multipath channel. As the recent OFDM systems have been applied to the various application areas, the coverage increases which can be translated into the wide range of the signal power variation observed at the receiver side. To obtain the optimum signal level the gain control block at the receiver front-end should be capable of processing wider range of the signal power than the conventional systems. If the signal power is not controlled properly, the overall system performance is expected to be deteriorated due to the quantization errors generated in the process of the analog to digital signal conversion. Therefore it is required to control the received signal power at the optimum level. In this paper, the gain control block is implemented based on the FPGA (Field Programmable Gate Array) hardware. The implemented block adopts multiple gain steps which are optimized by using the statistical characteristics of the quantized signal at the ADC (Analog to Digital Converter) output. The proposed design is shown to provide the enhanced convergence speed and reduced processing time while the hardware complexity is increased marginally compared with the conventional system.

Wireless Acoustic Emission Sensor Device with Microcontroller

Paper presents a wireless acoustic emission sensor device with microcontroller for monitoring systems of structures under stress, prevailed by a piezoelectric AE sensor, fixed on the material surface by an electroacoustic medium. The module performs the analogue to digital conversion of signals, the microcontroller commands the wireless interface, may send and receive information by other emitting -receiver wireless modules. The microcontroller could vary the amplifier gain and make the appropriate analogue – digital conversion. Important to the application is that several wireless modules, fixed on different structures could be part of complex AE monitoring systems.

A digital signal conversion system for astronomy radio interferometers with small antennas

Results of designing a digital signal conversion system for radio interferometers with small-diameter (up to 12 m) antennas are presented. The system contains four digital signal conversion channels with 500-MHz bandwidths. The output data stream rate in the VDIF format is 2048 Mbit/s per channel, and the cumulative output data flow is 8192 Mbit/s. The observation data flows arrive at the signal recording buffer unit and can be transmitted from there via a 10G Ethernet interface to a correlator in near-real time.

The Comprehensive Gateway Model for Diverse Environmental Monitoring Upon Wireless Sensor Network

This study is aimed to establish a wireless sensor network (WSN) gateway model prior to the back-end server for diverse environmental monitoring applications. The design catalogs different sensor data with transmission load balance to incorporate heterogeneity of sensor signals, stability of data transportation, and expenditure of mobile communication. As considering a variety of sensor characteristics for environmental monitoring, the proposed WSN gateway is designed with three bridged functions, including serial listener, transaction logger and Internet listener, to enable analog and digital signal conversion, physical data classification, threshold determination, database redundancy and mobile communication. The criterion-based scheme is created for remotely updating thresholds of monitored data from the back-end server to the gateway. The model is built upon the embedded computer for low power consuming to perform efficient and stable applications. The comprehensive model design can be easily utilized for general WSN surveillance with expansibility and flexibility.

Compression at the Physical Interface

This article focuses on recent progress in physical compressive sampling under the Defense Advanced Research Agency's Analog-to-Information (A-to-I) and Multiple Optical Non-Redundant Aperture Generalized Sensors (MONTAGE) programs. A-to-I and MONTAGE focus on aggressive forms of generalized sampling under which measurements consist of transformations, projections, or encodings of the signal onto discrete digital data. The central system design challenge is to select features, sampling strategies and hardware that enable high fidelity signal estimation from these features. The A-to-I and MONTAGE projects differ in application and implementation A-to-I seeks to revolutionize very high temporal bandwidth analog to digital signal conversion whereas MONTAGE seeks to revolutionize very high spatial bandwidth analog to digital signal conversion.

PLM 통신기반 선박용 LMS 구현

This paper describes the implementation of control and monitoring system of ship's lamps at local area using power line communication method, power line modem(PLM). We design modem, microprocessor interface for electric power control by frequency control and analog to digital signal conversion, lamp device.<BR> PLM communication is very economical using existing electric power line unlike RS-232, RS-485 communications. We verify and confirm by experimental work that control and monitor lamp system for ship by an PLM communication.