Open-loop Structure Research Articles

Reconfigurable Low-Power CMOS Amplifier Stages for Broadband Impedance Spectroscopy

In this paper, a fully differential amplifier is proposed in a 1.8 V-0.18 μm CMOS (Complementary Metal-Oxide-Semiconductor) technology, which can accommodate both voltage (V-mode) and current (C-mode) inputs. Post-layout simulation results show a fixed gain amplifier exhibiting a 26 dB (V-mode)/89 dBΩ (C-mode) gain and a programmable gain amplifier featuring a 6–26 dB gain, overall yielding a 26.8–46.4 dB dB (V-mode)/89.6–109.2 dBΩ (C-mode) programmable gain range, with a 100 MHz bandwidth and a power and area consumption of 360.5 µW and 0.0177 mm2, respectively. This amplifier has been designed considering the constraints and specifications (including low voltage, low power, reduced noise and high common mode rejection ratio) for its use in an analogue Lock-in-based Frequency Response Analyser-Impedance Spectroscopy (FRA-IS) device. The proposed design introduces a novel fully differential open-loop structure based on a transconductance–transimpedance (TC-TI) topology for high performance applications with a broad programmable bandwidth. To compare this work, different figures of merit (FoMs) are introduced as well as a comparison table with other simulated and experimental results, reporting an overall better performance in terms of gain, frequency and power-area consumption.

A hemicyanine-based fluorescent probe for detection of pH and its applications in live cells imaging and food monitoring

pH as an important parameter is closely related to many pathological processes and food freshness. In this paper, a new pH-sensitive fluorescent probe 1 based on hemicyanine dye was synthesized and used for the detection of pH in live cells and food spoilage. Under neutral and alkaline conditions, the phenolic hydroxyl group of the probe deprotonates, forming a closed spirocyclic structure and resulting in fluorescence quenching. Under acidic conditions, the probe maintains an open-loop structure and has intense fluorescence. The probe possessing good selectivity and stability can target lysosomes and visualize the exogenous pH in live cells. Furthermore, by using this probe, we successfully achieved the monitoring of pH in metamorphic process of shrimp and pork. This probe is expected to provide a good imaging tool for real-time detection of pH in live cells and food monitoring.

Dynamics and Concealment of Time-Delay Signature in Mutually Coupled Nano-Laser Chaotic Systems

It is well known that nano-lasers (NLs), as important optical components, have attracted widespread attention for their output characteristics. In this paper, the dynamic behavior and time-delay concealment properties of NLs mutually coupled in open-loop, semi-open-loop, and closed-loop structures have been numerically investigated. We employ bifurcation diagrams and 0–1 chaos tests in our simulations to quantitatively analyze the dynamic properties of the system and introduce the autocorrelation function to evaluate the ability of the system to conceal the time-delay signature (TDS). In the meantime, the effects of the NL parameters and the controllable variables of the system on the TDS are studied. The results indicate that, compared with an open-loop structure without feedback, the mutual coupling scheme with added feedback is beneficial for the system to output high-quality chaotic signals. Furthermore, selecting a moderate Purcell factor F and a smaller spontaneous emission coupling factor β can achieve TDS concealment over a wider parameter range of injection intensity and frequency detuning.

Emulation of IEEE STD 421.5/Industrial Excitation Systems Using a Micro-Alternator's Exciter

Micro-alternators, having similar parameters as turbo-alternators, play a significant role in the experimental evaluation of power system dynamics. Early thyristor excitation systems of micro-alternators have limited re-configurable options. Three possible control structures, two closed-loop control structures proposed in the literature and one open-loop control structure proposed in this paper, including a time constant regulator to mimic large machine time constants, are evaluated to emulate any IEEE 421.5 standard excitation system model or interface an industrial excitation system controller hardware in the loop (CHIL). It is shown that the communication delay introduced in CHIL does not impact the closed-loop stability within the bandwidth requirements of the excitation systems. One of the closed-loop structures, which is more generalized, and the open-loop structure performances are compared for emulating IEEE AC4C, DC1C, and ST1C excitation systems on a laboratory micro-machine based single machine infinite bus test system with buck exciter and H-bridge chopper (HBC) exciter using EMTP simulations under small and large disturbances. HBC exciter is used in the experimental validation with both the closed-loop and the open-loop control structures. The proposed open-loop structure is easy to implement and performs better than the closed-loop structure.

Development and Research of the Sensitive Element of the MEMS Gyroscope Manufactured Using SOI Technology

In this article, based on the developed methodology, the stages of designing the sensitive element of a microelectromechanical gyroscope with an open-loop structure are considered. This structure is intended for use in control units for mobile objects such as robots, mobile trolleys, etc. To quickly obtain a ready-made gyroscope, a specialized integrated circuit (SW6111) was selected, for the use of which the electronic part of the sensitive element of the microelectromechanical gyroscope was developed. The mechanical structure was also taken from a simple design. The simulation of the mathematical model was carried out in the MATLAB/Simulink software environment. The mechanical elements and the entire structure were calculated using finite element modeling with ANSYS MultiPhysics CAD tools. The developed sensitive element of the micromechanical gyroscope was manufactured using bulk micromachining technology−silicon-on-insulator−with a structural layer thickness equal to 50 μm. Experimental studies were carried out using a scanning electron microscope and a contact profilometer. Dynamic characteristics were measured using a Polytec MSA-500 microsystem analyzer. The manufactured structure has low topological deviations. Calculations and experiments showed fairly accurate results for the dynamic characteristics, with an error of less than 3% for the first iteration of the design.

Experimental study on convective heat transfer of an open-loop borehole heat exchanger

Open-loop borehole heat exchanger (OBHE) is a single well geothermal heat exchanger with an open-loop structure that can realize the geothermal energy extraction without mining the geothermal water. In this paper, a sandbox experiment is designed to simulate the convective heat transfer process in the reservoir area of OBHE. The mechanism of convective heat transfer in the reservoir area is studied, and the key factors that affect the convection heat transfer intensity are analyzed. The results show that the convection heat transfer of OBHE in the reservoir area is affected by both the driving effect of fluid flow inside the screen tube and the buoyancy effect. In the forward flow mode, the two effects have the opposite direction. While in the backward mode, the two effects have the same direction. The backward flow mode is more conducive to convective heat transfer. In addition, many factors influencing significantly the convective heat transfer of OBHE include inlet temperature, inlet flow rate, reservoir temperature, fluid flow direction and inner tube diameter.

A 63 μg/√Hz Noise Floor and 14 pJ Power Efficiency Open-Loop MEMS Capacitive Accelerometer Using Closed-Loop Hybrid Dynamic Amplifier

MEMS capacitive accelerometer for the Internet of Things (IoT) applications is designed with open-loop structure rather than close-loop structure to achieve low power consumption. In the open-loop structure, voltage control readout technique is preferred for low cost. However, voltage control readout technique suffers from poor noise performance and low power efficiency (in terms of FoM). In this paper, the weak feedback oversampling successive approximation readout circuit which merges the closed-loop hybrid dynamic amplifier with noise reduction technique is proposed to achieve low noise floor, high power efficiency and high accuracy. The proposed WFB-OSA based readout circuit is fabricated in a commercial <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18\mu \text{m}$ </tex-math></inline-formula> 1.8V CMOS process. The measurement result shows that the circuit has achieved a noise floor of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$63\mu g/\surd Hz$ </tex-math></inline-formula> and an FoM of 14pJ.

Study on the underpinning mechanisms of microwave-induced synthesis of carbon-coated metal nanoparticles

Microwave-induced metal arc discharge provides an intriguing solution for the synthesis of carbon-coated metal nanoparticles (M@CNPs) due to its fast formation and improved quality of products, however, the underpinning reaction mechanism is not comprehensively revealed. In this work, the effect of arc discharge intensity on the product morphology is firstly investigated by adjusting microwave power. And then, the effects of the organic groups (i.e. cyclopentadienyl v. s Acetylacetonate groups) and metal catalysis on the product morphology are also investigated by selecting ferrocene, iron acetylacetonate, nickelocene, and nickel acetylacetonate as precursors. Specifically, moderate microwave power can not only destroy the precursor to form carbon nanosheets by inducing intense discharge heat release but also provide sufficient intermittency to allow the carbon nanosheets to deposit on the surface of the metal core, which is an important precondition in fabricating M@CNPs. The structure of organic groups in the precursor also plays a predominant role in adjusting product morphology. Cyclopentadienyl groups tend to encapsulate the metal core to form graphitized carbon shells as the coordination bond between cyclopentadienyl and metal is recognized as a very strong covalent bond that confines the cyclopentadienyl collapse to metal core, and the cyclic structure facilitates the formation of graphite. In contrast, the acetylacetonate groups intend to combine randomly due to their open-loop structure. Moreover, for open-loop structures such as acetylacetonate groups, metal catalysis also affects the growth trend, of which Ni is more likely to induce the formation of carbon nanotubes relative to Fe. This work can provide a good reference for the synthesis of M@CNPs with controllable morphology.

Design of a high-voltage resistant and highly reliable LDO for automotive applications

This paper presents a high reliability low dropout linear regulator with high voltage tolerance, which uses an open loop structure and is applied to the feedforward response portion of the power tube gate to enhance the transient response of the LDO. The proposed LDO is simulated using a 0.18um DTI isolated BCD process with a 3.3V-14V supply voltage, a maximum input voltage of 40V and an adjustable output voltage of 3.1V/5V. The line regulation is 0.086% at 40V high voltage input and the supply voltage rejection ratio of the circuit can be maintained at around 60dB.

Infinite horizon Stackelberg differential games with random coefficients under control input constraint

In this paper, we study Stackelberg stochastic differential game driven by stochastic differential equation (SDE for short) with random coefficients on infinite horizon under convex control constraint. The control enters into the drift and diffusion terms simultaneously. By employing the first-order adjoint equation (backward stochastic differential equation, BSDE for short), we are able to announce Pontryagin's maximum principle for the leader's global Stackelberg solution, within adapted open-loop structure, where the term global means that the leader's domination over the entire game duration. Due to the follower's adjoint equation develops into a BSDE, the leader will be confronted with a control problem where the state equation is a kind of infinite horizon fully coupled forward-backward stochastic differential equation (FBSDE for short). We shed light on an important application in a class of infinite horizon linear-quadratic (LQ for short) Stackelberg games in which the control process of leader's is constrained in a closed convex subset Γ 1 of full space R m 1 . Whenever the control domain is postulated to be full space, we derive a new kind of infinite horizon backward stochastic Riccati equation (BSRE for short) with asymmetric coefficients.

Towards a new effective strategy to obtain optimal radial structure in power distribution networks: Graph theory-based topology assessment

Power distribution networks (PDNs) are principally operated and planned in a radial—open-loop—structure to satisfy several techno-economic goals. It is, therefore, indispensable to develop new practical strategies to rigorously investigate the radial structure-related limitation in the operation and planning of the PDNs. In this study, after a thorough and critical review of existing strategies in the literature, a new effective graph theory-based topology assessment strategy (GT-ToST) is outlined to examine the radial structure-related limitation. Then, both the distribution branch reconfiguration (DBR) problem and the multi-stage joint distributed generation and distribution network expansion planning (DG&DNEP) problem (most appropriate for the short and long-term horizons, respectively) are employed to explore the feasibility and practicality of the newly proposed strategy compared to the existing ones. The proficiency of the proposed strategy is investigated for the DBR problem with a modified 33-bus PDN and a modified real-world 177-bus PDN in Rio de Janeiro, as well as for the DG&DNEP problem with a modified 27-bus PDN and a modified real-world 104-bus PDN in the northeast part of Brazil. The obtained results from the illustrative examples and case studies prove the effectiveness of the proposed GT-ToST compared to the existing strategies.

A Method Without Stability Issue for Robust Estimation of Three-Phase Grid Frequency

The grid frequency estimation using a recursive signal or an integrator-based method may suffer from a stability issue due to an accumulation or discretization error. To avoid these shortcomings and also to obtain a robust estimation of three-phase grid frequency under unbalanced and distorted conditions, this letter proposes a demodulation-based method without using a recursive signal and integrator. The proposed demodulation-based approach relies on the Clarke transform and fixed transport delay-based relatively simple finite-impulse-response filters. It includes an open-loop structure, thus unconditionally stable. It also does not demand the real-time evaluation of the trigonometric or inverse trigonometric function. Moreover, it generates improved accuracy as compared with a frequency-locked loop and phase-looked loop.

Research on D-Shape Open-Loop PCF Temperature Refractive Index Sensor Based on SPR Effect

PCF (Photonic crystal fiber) temperature refractive index sensor based on SPR effect with the new double membrane open-loop structure is proposed. The inner surface of such PCF&#x2019;s open-loop structure is plated with a layer of 70 nm gold film, and a layer of 20 nm SiO <inline-formula><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> film is coated on the gold film, which could effectively prevent the gold film from oxidation corrosion. Besides, the open loop could reduce the production cost, and it could form two energy channels with nearby air holes, promoting the leakage of core energy to plasma mode and enhancing the SPR effects. The ethanol could be adopted as the temperature sensing solution, to measure the refractive index sensing of the solution to be measured. Numerical simulation is carried out based on the full vector finite element method, and the simulation results indicate that the average wavelength sensitivity of refractive index sensing could reach 3330 nm/RIU, and the wavelength sensitivity of temperature sensing could reach 0.912 nm/<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C, and a maximum figure of merit (FOM) of 102 which is approximately four times larger than that of the similar reported PCF-SPR sensors in the literature. The simulation results show that D-shape open-loop photonic crystal fiber has the potential application prospect on the temperature and refractive index sensing.

Group-Chopping: An 8-Channel, 0.04% Gain Mismatch, 2.1 µW 0.017 mm2 Instrumentation Amplifier for Bio-Potential Recording.

An 8-channel AFE with a group-chopping instrumentation amplifier (GCIA) is proposed for bio-potential recording applications. The group-chopping technique cascades chopper switches to progressively swap channels and dynamically removes gain mismatch among all channels. An 8-phase non-overlapping clocking scheme is developed and achieves excellent between-channel gain mismatch characteristics. The dynamic offsets among all channels are mitigated by the GCIA as well. The GCIA is the first work that minimizes the gain mismatch across more than two channels. With the help of the group-chopping, combined with an area-efficient open-loop structure, the GCIA shows <0.04% between-channel gain mismatch, the lowest mismatch reported to date. The chip is fabricated in 0.18µm 1P6M CMOS, occupies only 0.017 mm2/Ch., consumes 2.1 μW/Ch. under 0.5 V supply and achieves an NEF of 2.1.

A method to improve multi-node power transmission efficiency of inductively coupled mooring cable.

The inductively coupled mooring cable is an important tool for monitoring the ocean hydrological data. The mooring cable is an open-loop structure that uses a section of seawater as the transmission medium. The power transmission efficiency of this structure is very low due to the large power loss of the seawater medium, and it is rarely studied. In this paper, a contactless power transmission circuit with seawater loss is analyzed, and the theoretical model of multi-node power transmission of the inductively coupled mooring system is established. In this model, the improvement of the output power and transmission efficiency is only related to the frequency selection and the properties of the magnetic core itself, such as the magnetic core material. Moreover, the optimal scheme is selected according to the output power requirements. The experimental results show that when the input current (Irms) is 2A, the output power of a single node is 12W, the total output power is 120W, and the total transmission efficiency reaches 50%.

Differential diagnosis of superficial duodenal epithelial tumor and non-neoplastic lesion in duodenum by magnified endoscopic examination with image-enhanced endoscopy.

Differential diagnosis of superficial duodenal epithelial tumors (SDETs) and non-neoplastic lesions (NNLs) in duodenum by endoscopy is difficult. Here, we attempted to distinguish them by magnified endoscopic examination with image-enhanced endoscopy (IEE-ME). Various IEE-ME findings of 95 SDETs who underwent endoscopic resection and 58 NNLs who underwent biopsy were retrospectively reviewed. When we compared the IEE-ME findings of SDETs and NNLs, the presence of demarcation line (DL) (97.9% vs. 79.3%, P = 0.0002), white opaque substance (WOS) (84.2% vs. 1.7%, P < 0.0001) and light blue crest (LBC) (93.7% vs. 32.8%, P < 0.0001) and the absence of enlarged marginal epithelium (EME) (98.9% vs. 62.1%, P < 0.0001) were significantly more frequent in SDETs than NNLs. When divided into each superficial structure, it was the most effective to evaluate the combination of WOS and LBC as SDET with open-loop structure (OLS), and the combination of DL and EME as SDET with closed-loop structure (CLS). However, LBC was excluded because of low inter- and intra-observer agreements. Finally, the sensitivity, specificity and accuracy for the diagnosis of SDETs were 88.4%, 98.3% and 92.2%, respectively, and we developed an algorithm for the differential diagnosis of duodenal lesions. We could distinguish SDET from NNL, diagnosed SDET as presence of WOS indicated OLS of superficial structure, and presence of DL and absence of EME indicated CLS of superficial structure.

Capacitance-to-voltage converter employing parallel-series passive charge integrator for low noise power efficient MEMS capacitive sensor

Parallel-series passive charge integrator (PSPI) based capacitance-to-voltage converter (CVC) is proposed in this paper to reduce the noise floor of readout circuit for MEMS capacitive sensor with high power efficiency in terms of the figure of merit (FoM). For MEMS capacitive accelerometer, open-loop structure is preferred for its low power consumption. However, in the open-loop structure, the capacitance variation of sensing element is limited to femto-farad level in order to overcome nonlinearity. As a result, the thermal noise from parasitic capacitance becomes significant, which leads to low SNR. Traditional oversampling method can reduce the parasitic-induced noise, but leads to low power efficiency. In this work, the PSPI-CVC is proposed to reduce the parasitic-induced noise with high power efficiency. The PSPI-CVC is designed by a commercial 0.18 μm CMOS process. The transistor-level simulation results show that, compared to the traditional CVC, the PSPI-CVC can improve the SNR by 24 dB without increase of the power consumption. Compared with the other similar works, the proposed readout circuit achieves competitive FoM1 (FoM1 =20.2pJ)and the best FoM2 (FoM2).

Correlated Double Amplifying Readout Technique for Low-Noise Power-Efficient MEMS Capacitive Accelerometer

MEMS capacitive accelerometer for the Internet of things applications is designed with open-loop structure rather than close-loop structure to achieve low power consumption. In the open-loop structure, voltage control readout structure instead of charge control readout structure is preferred for low cost. However, the voltage control readout structure suffers from low power efficiency (in terms of <i>FoM</i>) due to significant parasitic-capacitance-induced noise. In this paper, the correlated double amplifying (CDA) technique is proposed to reduce the noise of the voltage control readout circuit with high power efficiency. Although, traditional correlated double sampling (CDS) technique can also be used in readout circuit to reduce the parasitic-capacitance-induced noise, it sacrifices driving ability and bandwidth of the readout circuit while CDA does not. The CDA technique adopts correlated amplifying to reduced noise without significant increase of power consumption. Thus, CDA technique leads to higher power efficiency. The CDA technique is demonstrated in a fully-differential readout circuit fabricated in a 0.18um CMOS process and tested with a sensing element from a commercial MEMS accelerometer. The measurement results show that noise floor of the readout circuit is 0.5<i>aF</i>/&#x221A;<i>Hz</i> and the noise floor of the whole system is 112<i>ug</i>/&#x221A;<i>Hz</i>, with a power consumption of 139&#x03BC;W and a bandwidth of 12.5kHz. The full input range is &#x00B1;4g, a <i>FoM</i>₁ of 80<i>pJ</i> and a <i>FoM</i>₂ of 254<i>uW</i> &#x2219; <i>ug</i>/<i>Hz</i> are achieved.

Phase-locked subdivision method of digital signal based on FPGA

In order to improve the accuracy and real-time performance of the subdivision signal expression result of the photoelectric encoder in the signal dynamic measurement process, a phase-locked subdivision method of digital signal based on FPGA is proposed. The open-loop structure is used to realize the large-range detection of the grating measurement system, and the fractional frequency division method is used to realize the subdivision function of the grating moiré signal. In order to verify the effectiveness of the design, we compare the analog signal subdivision with the traditional digital phase-locked subdivision method. The experimental results show that the digital phase-locked subdivision algorithm designed in this paper can be used in the high-frequency moiré signal frequency and rate of change. The subdivision function is realized under the following conditions, which can be better applied to dynamic measurement occasions.

Simulation analysis of a single well geothermal system with open-loop structure

The relatively small heat exchange power limits the promotion and application of deep borehole heat exchanger (DBHE) with the closed loop due to the main heat transfer pattern of heat conduction through rocks with poor thermal conductivity coefficient. Furthermore, geothermal water is prohibited to extract in some places even with 100% reinjection. To solve the above problems, here a novel single-well enhanced geothermal system (SEGS) is studied with an open-loop structure having the convection heat exchange process. The heat transfer performance, mechanism and main influential factors of SEGS are studied. Result shows that the heat transfer performance of SEGS is greatly improved compared to DBHE, and the average heat transfer power of SEGS reaches 1603.6 kW and 1204.6 kW respectively with different operation modes. In addition, the study also finds that the convective heat transfer process inside the geothermal reservoir is simultaneously affected by the driving effect of the fluid in the screen and the buoyancy effect. Further, the above two effects act in the same direction when the annulus is used as the inlet, while they act in the opposite direction when the inner tube is used as the inlet.