Minimum Signal Research Articles

EPR measurement of environmental radiation using human fingernails

Abstract In this research work, human fingernails were utilized to estimate the radiation dose using EPR measurements of radiation-induced radicals. The limiting factors in this research were the presence of mechanical induced EPR signals due to the mechanical stress during the preparation of the samples. The mechanically induced signals overlap with the radiation-induced signal, which considerably can overestimate the dose. Thus, different treatment methods of fingernails were used to reduce the mechanical induced signals. The results demonstrate that the mechanical and radiation induced signals have apparently different microwave power saturation behavior. Also, mechanical induced signal shows a fading evolution vs. time and reaches to a constant value. Chemical treatment using the different reagents showed that the minimum mechanical induced signal was obtained using the dithiothreitol reagent. The dose response curves of the treated samples with dithiothreitol for 30 min demonstrated a more linearity, and closer curves in comparison to those treated in 5 min. Therefore, to find out an unknown absorbed dose in a fingernail sample using a calibration curve, it could be recommended to use the mentioned chemical treatment procedure to reduce the uncertainty.

A Readout Channel Optimized for Minimum NEP of a FET-Based THz Pixel

This paper presents a high-gain, noise-efficient readout interface for a FET-based direct THz detector fabricated in 0.15 μm standard CMOS technology. The pixel, conceived to be used in array configuration for an imaging application, consists of an on-chip antenna, a FET device for THz signal detection and a chopper-stabilized readout interface performing in-pixel filtering and amplification. The switched-capacitor multistage design achieves a closed-loop gain of 70 dB and a system bandwidth of 1 kHz, thereby improving the SNR and limiting the total integrated input referred noise of the channel to less than the minimum detectable signal limit defined by the FET detector. The measurement results show that the pixel is able to achieve a maximum voltage responsivity of 470 kV/W and a minimum NEP value of 480 pW/√Hz at the antenna frequency of 370 GHz. The pixel consumes 200 μW power, and it occupies an area of 0.375mm2.

Toward quasi-DC conductivity of warm dense matter measured by single-shot terahertz spectroscopy.

We present an experimental setup capable of measuring the near DC conductivity of laser generated warm dense matter using single-shot terahertz time-domain spectroscopy. The setup uses a reflective echelon and balanced detection to record THz waveforms with a minimum detectable signal of 0.2% in a single laser pulse. We describe details of the experimental setup and the data analysis procedure and present single-shot terahertz transmission data on aluminum that has been laser heated to an electron temperature of 0.5 eV.

Field test of a 16 channel high sensitivity FBG geophone array

In this paper we report the development and field test of a 16 channel high sensitivity fiber Bragg grating (FBG) geophone array for oil and gas exploration application. A high sensitivity FBG geophone is designed, and its sensitivity is about 1000pm/g. The wavelength change of the FBG geophone is interrogated by using interferometric demodulation method, and the demodulation system noise is below 10−3pm/. And the minimum detectable seismic signal is below 1μg/. We are presenting field test results for the FBG geophone and comparing its performance with regular exploration geophones. In comparison, FBG geophone has the advantages of higher signal-to-noise ratio and better low-frequency response. This work shows that using FBG technology to develop geophone for oil and gas exploration is both advantageous and feasible.

Single-photon 3D imaging with deep sensor fusion

Sensors which capture 3D scene information provide useful data for tasks in vehicle navigation, gesture recognition, human pose estimation, and geometric reconstruction. Active illumination time-of-flight sensors in particular have become widely used to estimate a 3D representation of a scene. However, the maximum range, density of acquired spatial samples, and overall acquisition time of these sensors is fundamentally limited by the minimum signal required to estimate depth reliably. In this paper, we propose a data-driven method for photon-efficient 3D imaging which leverages sensor fusion and computational reconstruction to rapidly and robustly estimate a dense depth map from low photon counts. Our sensor fusion approach uses measurements of single photon arrival times from a low-resolution single-photon detector array and an intensity image from a conventional high-resolution camera. Using a multi-scale deep convolutional network, we jointly process the raw measurements from both sensors and output a high-resolution depth map. To demonstrate the efficacy of our approach, we implement a hardware prototype and show results using captured data. At low signal-to-background levels, our depth reconstruction algorithm with sensor fusion outperforms other methods for depth estimation from noisy measurements of photon arrival times.

MMSE and maximum a posteriori estimators for speech enhancement in additive noise assuming a t ‐location‐scale clean speech prior

The authors derive closed form solutions for the minimum mean square error (MMSE) and maximum a posteriori estimators for speech enhancement in additive Gaussian noise assuming a t -location-scale probability density function (PDF) as clean speech prior. Fitting a t -location-scale PDF to the real and imaginary parts of the discrete fourier transform (DFT) coefficients of clean speech signals demonstrates the lower Jensen–Shannon divergence compared to the other heavy-tailed distributions such as Laplacian and gamma. The authors utilise the two presented estimators along with the Wiener filter and MMSE estimators based on Laplacian, gamma, and generalised gamma prior PDFs to enhance noisy signals from the NOIZEUS database. All the estimators are compared together in terms of both signal and noise distortions. The obtained results show that their proposed MMSE estimator results in the minimum squared error and signal distortion to estimate the complex-valued DFT coefficients of speech. The quality assessments of the enhanced signals are also performed in terms of perceptual evaluation of speech quality, segmental and general SNRs.

Investigation on the conformational changes of bovine serum albumin in a wide pH range from 2 to 12

The conformation of bovine serum albumin largely depends on its microenvironment pH and affects its physical functions and applications. In this study, we investigated the effects of pH (wide range 2–12) on the conformation of bovine serum albumin based on spectroscopic signals by various spectroscopic means including fluorescence, synchronous fluorescence, resonance light scattering, UV-visible absorption, and circular dichroism. The changes in spectroscopic signals, such as peak position and intensity, showed that the structure of bovine serum albumin varied significantly with pH. The conformation of bovine serum albumin was compact at pH 6–7, as indicated by the largest peak position values and peak intensities in the fluorescence, synchronous fluorescence, and RLS spectra. The structure of bovine serum albumin became loose in the acidic or alkaline environment, as indicated by the decreased peak position values and peak intensities. The microenvironment of the amino acid residues of bovine serum albumin also varied with pH, as indicated by the changing peak position values. At pH 7, the hydrophobicity of the tyrosine and tryptophan residues was the weakest, as indicated by the minimum synchronous fluorescence signals. In addition, the secondary structure of bovine serum albumin, especially α-helix, varied with pH. The content of α-helix reached the maximum value of 68% at pH 6–8, whereas it decreased in the acidic or alkaline environment. The study provides valuable details for studying the physiological function and applications of serum albumins.

Greedy Heuristic Resource Allocation Algorithm for Device-to-Device Aided Cellular Systems with System Level Simulations

Resource allocation in device-to-device (D2D) aided cellular systems, in which the proximity users are allowed to communicate directly with each other without relying on the intervention of base stations (BSs), is investigated in this paper. A new uplink resource allocation policy is proposed by exploiting the relationship between D2D-access probability and channel gain among variant devices, such as cellular user equipments (CUEs), D2D user equipments (DUEs) and BSs, etc., under the constraints of their minimum signal to interference-plus-noise ratio (SINR) requirements. Furthermore, the proposed resource-allocation problem can be formulated as the cost function of “maximizing the number of simultaneously activated D2D pairs subject to the SINR constraints at both CUEs and DUEs”. Numerical results relying on system-level simulations show that the proposed scheme is capable of substantially improving both the D2D-access probability and the network throughput without sacrificing the performance of conventional CUEs.

Microwave Frequency Generation, Switching, and Controlling Using Single-Mode FP-LDs

RF signal generation, switching, and reconfiguring are essential and important features for the rapidly developing microwave system, which are usually implemented using independent components or subsystems. In this paper, we propose and demonstrate an optical method to generate and switch the RF frequency at the stage of generation based on control input state using external cavity based single mode Fabry–Perot laser diode. The RF frequency generation, switching, and controlling are based on the principle of injection locking with negative and positive wavelength detuning. In the proposed scheme, a single external beam is simultaneously used to control RF switching as well as to generate RF signal through optical heterodyning of injection locked beams. This eliminates the necessity of two separate external beams to switch and generate RF signal. Based on the logic state of the input control beam, the frequency of the generated RF signal can be changed to another RF frequency within a group of predefined RF bands. In a proof-of-concept experiment, a 2-Gbps, 16-bit nonreturn-to-zero control signal is applied to switch the frequency of the generated RF signal. We obtain the minimum signal to noise power ratio of more than 23 dB, the maximum linewidth of 165 kHz, and rising and falling times of less than 40 ps associated with the RF switching. The tunable range, RF frequency, and RF power variation of the generated RF signals are also observed. Moreover, using random control signals, random sequences of RF frequencies can be generated using the same experimental and hardware setup. Such reconfigurability and flexibility of our system to generate several random RF signals from the same framework enables application of the proposed method in several fields such as secure communication, encryption, and military applications.

High Sensitivity and Wide Dynamic Range Analog Front-End Circuits for Pulsed TOF 4-D Imaging LADAR Receiver

Analog front-end (AFE) circuits, which mainly consist of a transimpedance amplifier (TIA) with wide dynamic range and a timing discriminator with double threshold voltage, were designed and implemented for a pulsed time-of-fight 4-D imaging LADAR receiver. The preamplifier of the proposed TIA adopts a shunt-feedback topology to amplify weak echo signal, and a current-mirror topology to amplify strong one, respectively. The proposed AFE can capture directly the pulsed echo amplitude with wide dynamic range through programmable gain control switches. The proposed AFE circuits, which achieve a high gain of 106 dB $\Omega $ , a linear dynamic range of 80 dB, an averaged input-referred noise density of 0.89 pA/Hz0.5 and a minimum detectable signal of $0.36~\mu \text{A}$ at SNR = 5, and a sensitivity of 8 nW with APD of 45 A/W, were designed with 3.3 V devices and fabricated in a 0.18- $\mu \text{m}$ standard CMOS process. The total area of AFE, which includes the circuit core, bandgap and bias circuits, and I/O PAD, is approximately equal to $1.20\times 1.13$ mm2.

Investigation of phosphate glass doped lanthanum as beta dosimeter

Phosphate glass samples with different doped lanthanum concentrations were prepared. The samples were subjected to XRD investigation. The given thermoluminescence glow curves of the samples were analyzed and exhibited a superimposed of five glow peaks at 386.7, 422.4, 461.6, 488.8 and 510.3 K. The activation energies of the corresponding electron traps were defined with their frequency factors and their lifetimes. The dosimetric properties of the glass doped lanthanum as beta dosimeters were investigated like dose response linearity, dosimetric sensitivity, reproducibility, minimum detectable dose and signal stability were done as well.

Distributed Power Control Algorithm in Orthogonal Frequency Division Multiple Cognitive Radio Systems for Fading Channel

In order to guarantee the quality of service (QoS) for primary users (PUs) and secondary users (SUs) in fading channel, a distributed power control algorithm is proposed based on convex optimization theory in underlay OFDM cognitive radio networks (CRNs). Our purpose obtains the maximum transmit data rate of each SU at all subcarriers under three constraints of the maximum allowable transmission power, the minimum signal to interference plus ratio (SINR) of each SU and the maximum allowable interference generated from SUs to PU at each subcarrier. Simulation results show that the performance of the proposed algorithms (m2) are superior to the geometric programming algorithm (m1) in fading channel environment.

Investigation and performance evaluation of filter aided configurations for erbium doped fiber optical amplification system

Various possible configurations of EDFA’s namely Single Pass (SP) EDFA, Double Pass (DP) EDFA, Double Pass with Filter (DPF) EDFA, Triple Pass with Filter (TPF) EDFA and finally Quadruple Pass with Filter (QPF) EDFA are designed. DPF EDFA is an upgraded and enhanced version of DP EDFA configuration designed by using an optical filter in cascade. This filter has been designed with an optimal set of internal parameters namely center wavelength, bandwidth and depth. TPF and QPF EDFA configurations have also been designed. It is observed that in absence of upconversion, maximum Figure Of Merit (FOM) of about 40.35 dB is achieved in QPF EDFA configuration. With upconversion mechanism enabled the FOM of QPF EDFA reduces to only about 37.45 dB thus making QPF EDFA configuration suitable for practical applications. QPF and TPF EDFA had minimum gain ripple thus can be used in WDM applications, where flattened gain spectrum is an important requirement. The configurations offered here are less bulky with only one filter used instead of two as was the case in earlier configurations. QPF EDFA designed in this work has a reduced noise figure of about 4.85 dB at smaller lengths of EDFA of about 4.5 m and lower pump powers of about 90 mW. This configuration has highest sensitivity with the capacity to detect minimum signal power of −41.6 dBm. The QPF EDFA has an improved gain with reduction in noise figure, therefore QPF EDFA can be used as a preamplifier, to improve the sensitivity of receiver.

Cross-correlation limit of a SQUID-based noise thermometer of the pMFFT type

The primary magnetic field fluctuation thermometer (pMFFT) is a SQUID-based noise thermometer for temperatures below 1 K, which complies with metrological requirements. It combines two signal channels in order to apply the cross-correlation technique, but it requires statistically independent noise signals for proper operation. In order to check the limit of the cross-correlation readout, we have performed zero measurements in the millikelvin range in a setup that is identical to the pMFFT, except for the removed temperature sensor. We examined the influence of different parameters such as SQUID working point or flux-lock loop parameters on the minimum cross-correlation signal down to 24 mK and below 100 kHz. Depending on the configuration, typical minimum SQUID-referred cross-power spectral densities of 1.5 × 10−15 /Hz or even smaller values were observed. For the pMFFT, considering its thermal noise spectrum, these flux densities correspond to a device noise temperature of ≤2.5 µK, thereby ensuring a negligible uncertainty contribution at the lower end of the PLTS-2000 (0.9 mK).

A Carrier-Based Modulation Scheme to Reduce the Third Harmonic Component of Common-Mode Voltage in a Three-Phase Inverter Under High DC Voltage Utilization

High dc voltage utilization is one of the important requirements in a three-phase inverter. Under some carrier-based pulse width modulations (PWMs), the dc voltage utilization can reach the same maximum as that under the space vector modulation. But the third harmonic component of common-mode voltage (CMV) will be increased markedly while using these carrier-based PWMs in inverters. To improve the situation, this paper proposes that a midpoint-fluctuation carrier (MFC) scheme should be used in the three-phase inverter. The MFC is formed by adding a midpoint-fluctuation signal on the standard symmetrical triangular carrier. By analyzing the linear modulation region of the midpoint-fluctuation signals, a minimum fluctuant signal in the linear modulation region is designed in the paper. Compared with the use of other conventional schemes in the three-phase inverter, the use of minimum MFC scheme has higher fundamental amplitude in the output line voltage and smaller magnitude of the third harmonic in the CMV. The feasibility and validity of the MFC are proved by experiment results in a three-phase inverter.

A 77-dB Dynamic Range Low-Power Variable-Gain Transimpedance Amplifier for Linear LADAR

An adjustable-gain transimpedance amplifier with a wide linear dynamic range, low power consumption, and low input impedance was designed for a pulsed linear laser detection and ranging system. To extend the linear dynamic range within a low power consumption, some specific techniques are presented. A low-power current-mirror amplifier with a level shifter was used to decrease the input impedance and keep it stable. Adjustable transimpedance gain extends the input dynamic range, and a high-pass filter eliminates the influence of dc operating point drift caused by the variable gain. When implemented in 0.18- ${\mu }\text{m}$ standard CMOS technology, the receiver achieved a high gain of 106 dB with four configurable gain modes, a wide linear output swing of 1 V, an input-referred noise current of $1.52~ {\rm p{A}/ \sqrt {Hz}}$ , and a minimum detectable signal of 400 nA at SNR = 5, leading to a linear dynamic range of 77 dB, and the power consumption in the highest gain mode was 8 mW with a 3.3-V supply.

Foglight: Visible Light-Enabled Indoor Localization System for Low-Power IoT Devices

Advances in small and low power electronics have created new opportunities for the Internet of Things (IoT), leading to an explosion of physical objects being connected to the Internet. However, there still lacks an indoor localization solution that can answer the needs of various location-based IoT applications with desired simplicity, robustness, accuracy, and responsiveness. We introduce Foglight, a visible light enabled indoor localization system for IoT devices that relies on unique spatial encoding produced when mechanical mirrors inside a projector are flipped based on gray-coded binary images. Foglight employs simple off-the-shelf light sensors that can be easily coupled with existing IoT devices—such as thermometers, gas meters, or light switches—making their location discoverable. Our sensor unit is computation efficient; it can perform high-accuracy localization with minimum signal processing overhead, allowing any low-power IoT device on which it rests to be able to locate itself. Additionally, results from our evaluation reveal that Foglight can locate a target device with an average accuracy of 1.7 mm and average refresh rate of 84 Hz with minimal latency, 31.46 ms on Wi-Fi and 23.2 ms on serial communication. Two example applications are developed to demonstrate possible scenarios as proof of concept. We also discuss limitations, how they could be overcome, and propose next steps.

A Method of De-noise and Harmonics Detection in Power System Based on Periodicity Analysis

A novel method of de-noise and harmonics detection is presented. Firstly, based on periodicity analysis and signals which have been detected, one minimum period signal with slight noise could be calculated. This signal is named as Standard unit-Period (SuP). Then a correction model is constructed based on SuP and 3-sigma rule, aiming to revise the rough harmonic signal. From the view of solutions, SNR could be risen about 15 dB in a high-SNR background. Furthermore, SuP could be applied to improve DFT in harmonic detection by adjusting the length of harmonic signal. It not only helps to avoid errors caused by spectral leakage effectively in particular situations, but also makes detection method run faster and more precise. At last, applications of SuP in several complex situations are simulated. It showed that SuP could deal with various coloured noise effectively, and this method could be used when the system fluctuates with changing parameters.

Robust Multigroup Multicast Transmission for Frame-Based Multi-Beam Satellite Systems

We investigate robust multigroup multicast transmission for frame-based multi-beam satellite communication systems with full frequency reuse. To mitigate the effect of outdated channel state information (CSI), we first investigate robust multigroup multicast precoding that maximizes the minimum average signal to interference plus noise ratio (SINR) under the per-beam power constraints. We show the relationship between the robust max-min fair problem and the robust power minimization problem with partial CSI and propose a low complexity precoder for the robust power minimization problem. We then investigate user clustering which only requires partial CSI. We show that the approximated average SINR can be maximized provided that the estimated channel vectors of the users in the same cluster are linearly dependent while those in different clusters are mutually orthogonal. Motivated by this user clustering condition, we further propose a low-complexity user clustering algorithm. Simulation results demonstrate that the proposed robust approach can provide substantial performance gains over the conventional approach in multi-beam satellite communication systems.

Model petri net of adaptive traffic lights and its collaboration with a special event

Traffic lights have an important role as the system control of vehicles flow on the urban network. Commonly, most countries still using fixed time strategy. Our research proposes the adaptive traffic lights model to response the traffic demand. It uses basic Petri net as a general modeling framework. Foractuating method of minimum and maximum green signal time interval, the green traffic lights have three-time extension units. Next, we collaborate on a case of the existence of railways that crosses on the southern arm of an intersection. We introduce both of collaboration model design of traffic lights and the railway's gate which always closes while a train passing. Verification and validation of the model are based on the simulation result of vehicles queue. The collaboration model design of traffic lights has excellent performance, and it can resolve the congestion problem better than conventional schedule.