Front-end Circuit Research Articles

A Simple Calibration Method for Ratio Error and Phase Error of Electronic Energy Meter

The ratio errors of resistance divider network and current transformer, and the phase error introduced by current transformer, which are the main error sources, greatly affect the measurement accuracy of actual electronic energy metering equipment. Because the fairness of energy metering system has a significant influence on the energy market, a digital calibration method for ratio error and phase error of electronic energy meter is proposed to deal with this problem in this paper. By establishing the equivalent models of the analog front-end circuit of static meter, a simple and high accuracy digital calibration method for reducing ratio error and phase error of static meter is given. Firstly, the DC bias of each channel is subtracted from its corresponding channel. After that, correction coefficients are used to correct the ratio errors of voltage and current channels. Finally, a piecewise Lagrange quadratic interpolation method is used to realize phase error calibration. The proposed approach has the features of simplicity and high efficiency. The experimental results validate the accuracy and effectiveness of the proposed algorithm.

Design of a floating-ground-electrode circuit for measuring attenuation of the human body channel.

Recently, health care and disease prevention are more and more important in people's daily life. Human body communication (HBC) is an emerging short distance wireless communication mode, which is quite suitable for the communication between the wearable human health care equipment. However, most research on HBC mainly focuses on the electromagnetic model and the circuit model of equivalent human and the in vivo experiment is based on the commercial equipment. The aim of this paper is to design a circuit device for measuring the attenuation of the human body channel based on a floating-ground-electrode method. This paper proposed a new floating-ground-electrode method so as to solve problems of power and high frequencies interference and impedance matching. A circuit module, including signal generator, analog frontend circuit and MCU, was designed to initially replace the spectrum analyzer to measure the attenuation of the human body channel. The floating-ground-electrode added to the receiving end of the human body channel was connected to the ground of the analog frontend circuit, forming an equal potential circuit. The three-electrodes of the receiving terminal can act as a differential probe, since one electrode is connected to the ground and the other two electrodes achieved signal input and output respectively. The results showed that the experimental data of channel attenuation were similar to the measured value of the spectrum analyzer. The maximum absolute error was 1.148 dB and the relative error was 3.55%. In addition, different sizes of the floating-ground-electrode cannot affect the attenuation path of human body channels. Moreover, the common mode rejection ratio (CMRR) was approximated to the value of the commercial differential probe. This paper proposed a new floating-ground-electrode method for measuring the attenuation of the human body channel. It could provide the possibility for the dynamic measurement of attenuation and take the place of the spectrum analyzer and make the process of experiments simple and efficient.

A Mutual-Capacitance 3-D Gesture Sensing System Based on 2-D Orthogonal Encoding and an Un-Folding Coordinate Interpolation Schemes

This paper describes the design of a capacitance readout IC for 3-D hover gesture sensing system. The proposed IC adopts a multi-channel driving scheme in both driving and sensing electrodes of a TSP (touch screen panel). The proposed single encoding and summing (ENS) filter in the readout circuit senses all TSP channels at once, thereby reducing the power consumption and chip area. An incorporated correlated double sampler (CDS) performs down-conversion of the capacitance signal and moving average filtering for severe noise interferences with high pass-filtering of the ENS filter. The proposed IC also employs an efficient hovering gesture detection method that is based on an un-folding 1-dimensional coordinate extraction scheme and various triggering events. By employing the cascade driving for hovering detection, the hover frame rate is maintained to be the same as the TSP frame rate while achieving a targeted signal-to-noise ratio (SNR). The proposed readout IC was fabricated on a 130-nm CMOS process. The IC achieves 26-dB SNR at 10-mm hover height and 120-Hz frame rate with $16\times16$ TSP. The front end circuit occupies a chip area of 0.0912-mm2 and supports a supply voltage ranging from 2.7 V to 3.3 V.

Development of a front-end ASIC for silicon-strip detectors of the J-PARC muon [formula omitted]/EDM experiment

A front-end application specific integrated circuit (ASIC) with high rate capability and deep memory buffer is needed for the silicon-strip detector for the J-PARC muon g−2/EDM experiment. In this experiment, we reconstruct a positron track from muon decay by the silicon-strip detector and measure the muon anomalous magnetic moment and the electric dipole moment precisely to explore new physics beyond the Standard Model. The front-end ASIC is required to tolerate hit rates of 1.4 MHz per strip, to be stable to the change of hit rate by a factor of 150 from the beginning to the end of the measurement, and to have deep memory for the period of 40μs with 5 ns time resolution. To satisfy the experimental requirements, we designed a prototype ASIC “SliT128B” with the Silterra 180 nm CMOS technology. We report on the design and the performance of the SliT128B.

Feasibility study of SiPM based scintillation detector for dual-energy X-ray absorptiometry

Dual-energy x-ray absorptiometry (DXA) is the noninvasive method to diagnose osteoporosis disease characterized by low bone mass and deterioration of bone tissue. Many global companies and research groups have developed the various DXA detectors using a direct photon-counting detector such as a cadmium zinc telluride (CZT) sensor. However, this approach using CZT sensor has some drawback such as the limitation of scalability by high cost and the loss of efficiency due to the requirement of a thin detector.In this study, a SiPM based DXA system was developed and its performance evaluated experimentally. The DXA detector was composed of a SiPM sensor coupled with a single LYSO scintillation crystal (3 × 3 × 2 mm3). The prototype DXA detector was mounted on the dedicated front-end circuit consisting of a voltage-sensitive preamplifier, pulse shaping amplifier and constant fraction discriminator (CFD) circuit. The SiPM based DXA detector showed the 34% (at 59 keV) energy resolution with good BMD accuracy. The proposed SiPM based DXA detector showed the performance comparable to the conventional DXA detector based on CZT.

Design and performance of the front-end electronics for a 10BF3 tube array

A neutron yield monitoring system based on a 10BF3 tube array was designed to monitor fast neutrons with an energy of 14 MeV and a yield of 104–108 produced by a deuterium-tritium fusion reaction. The array contained six 10BF3 tubes of different sizes. The signal readout system used a charge sensitive preamplifier (CSA) as the front-end circuit. The CSA was optimized and tested to ensure that it met the measurement requirements for low charge and high counting rate. The zero-capacitance equivalent noise charge (ENC) was 2425 e− and the ENC slope was 15 e−/pF. In the temperature range 0–60̂C, the ENC slope was 10 e−/̂C and the baseline drift was less than 0.05 mV/̂C. In the 10 h long-term stability test, the baseline drift was less than 0.07 mV.

Offset-free DC-coupled analog frontend circuit for high-dynamic-range signals

The analog frontend (AFE) coupling circuit is a crucial processing element for data acquisition systems based on analog-to-digital converters (ADCs). Currently, high-speed and high-resolution ADCs are predominantly designed with differential input stages. Conventional high-speed ADC drivers are mainly AC-coupled by employing transformers (Baluns) or fully differential amplifiers (FDAs) with blocking capacitors. However, the results of this study indicate that a certain degree of DC offset error exists and manifests itself as the baseline error in the presence of power dividers connecting several DC-coupled channels that implement high-dynamic-range (HDR) signal conditioning. The study involves a theoretical analysis and explanation of the baseline offset error. The offset error can potentially lead to unexpected out-of-range issues for sampling devices, including high-speed ADCs and switched capacitor array ASICs. High-performance FDAs are adopted, and an offset-free DC-coupled AFE circuit is proposed to address the aforementioned issue using two-stage amplification and a resistive attenuator. The proposed methodology is verified via circuit simulations and hardware design. Thus, the baseline offset problem can be accurately solved using the proposed circuit by minimizing the neglectable error. The proposed circuit facilitates improvements in the high-precision measurement of HDR signals in many nuclear physics experiments and some applications in the DC-coupling scheme with FDAs involving resistive power dividers.

Development of a High-Rate Front-End ASIC for X-Ray Spectroscopy and Diffraction Applications

-We developed a new front-end application-specific integrated circuit (ASIC) to upgrade the Maia X-ray microprobe. The ASIC instruments 32 configurable channels that perform either positive or negative charge amplification, pulse shaping, peak amplitude, and time extraction along with buffered analog storage. At a gain of 3.6 V/fC, 1-μs peaking time, and a temperature of 248 K, an electronic resolution of 13 and 10 e- rms was measured with and without a silicon drift detector (SDD) sensor, respectively. A spectral resolution of 170-eV full-width at half-maximum (FWHM) at 5.9 keV was obtained with an 55Fe source. The channel linearity was better than ± 1% with rate capabilities up to 40 kcps. The ASIC was fabricated in a commercial 250-nm process with a footprint of 6.3 mm × 3.9 mm and dissipates 167 mW of static power.

Phase noise estimation method for RF front-end circuit of GNSS receiver

Phase noise estimation method for RF front-end circuit of GNSS receiver

Bidirectional multiport solar‐assisted SRM drive for pure electric vehicle applications with versatile driving and autonomous charging capabilities

Pure electric vehicles (PEVs) offer a solution for achieving a zero-emission transport system. This study presents the work towards the development of a bi-directional multiport solar-assisted switched reluctance motor (SRM) drive for PEV applications having battery-to-vehicle (B2V), photovoltaic (PV)-to-vehicle (PV2V), PV assisted B2V, grid-to-vehicle battery charging and PV2V battery charging functions. The power circuit is formed by the combination of a front-end circuit and a modified-Miller SRM converter. Battery, PV panel, grid and SRM form the four ports of this multiport drive, which with proper control, provide motoring, braking and charging functions. The dc-link voltage is fully controllable which improves the machine performance both at higher and lower speeds. During stand-still conditions, the battery is charged either from the grid at unity power factor or through the PV panel by incorporating the drive components to form an on-board battery charger, thereby reducing the reliance on charging stations. A fault-tolerant control is developed to operate the system with desired performance under single and double phase open-circuit faults. An 8/6 SRM is used for proof of concept and the experimental results confirm the effectiveness of the proposed drive and control strategy.

Miniaturized 0.13-μm CMOS Front-End Analog for AlN PMUT Arrays.

This paper presents an analog front-end transceiver for an ultrasound imaging system based on a high-voltage (HV) transmitter, a low-noise front-end amplifier (RX), and a complementary-metal-oxide-semiconductor, aluminum nitride, piezoelectric micromachined ultrasonic transducer (CMOS-AlN-PMUT). The system was designed using the 0.13-μm Silterra CMOS process and the MEMS-on-CMOS platform, which allowed for the implementation of an AlN PMUT on top of the CMOS-integrated circuit. The HV transmitter drives a column of six 80-μm-square PMUTs excited with 32 V in order to generate enough acoustic pressure at a 2.1-mm axial distance. On the reception side, another six 80-μm-square PMUT columns convert the received echo into an electric charge that is amplified by the receiver front-end amplifier. A comparative analysis between a voltage front-end amplifier (VA) based on capacitive integration and a charge-sensitive front-end amplifier (CSA) is presented. Electrical and acoustic experiments successfully demonstrated the functionality of the designed low-power analog front-end circuitry, which outperformed a state-of-the art front-end application-specific integrated circuit (ASIC) in terms of power consumption, noise performance, and area.

Harmonic Distortion Optimization for Sigma-Delta Modulators Interface Circuit of TMR Sensors.

The tunneling magnetoresistance micro-sensors (TMR) developed by magnetic multilayer material has many advantages, such as high sensitivity, high frequency response, and good reliability. It is widely used in military and civil fields. This work presents a high-performance interface circuit for TMR sensors. Because of the nonlinearity of signal conversion between sensitive structure and interface circuit in feedback loop and forward path, large harmonic distortion occurs in output signal spectrum, which greatly leads to the reduction of SNDR (signal noise distortion rate). In this paper, we analyzed the main source of harmonic distortion in closed-loop detection circuit and establish an accurate harmonic distortion model in TMR micro-sensors system. Some factors are considered, including non-linear gain of operational amplifier unit, effective gain bandwidth, conversion speed, nonlinearity of analog transmission gate, and nonlinearity of polycrystalline capacitance in high-order sigma-delta system. We optimized the CMOS switch and first-stage integrator in the switched-capacitor circuit. The harmonic distortion parameter is optimally designed in the TMR sensors system, aiming at the mismatch of misalignment of front-end system, non-linearity of quantizer, non-linearity of capacitor, and non-linearity of analog switch. The digital output is attained by the interface circuit based on a low-noise front-end interface circuit and a third-order sigma-delta modulator. The digital interface circuit is implemented by 0.35μm CMOS (complementary metal oxide semiconductor) technology. The high-performance digital TMR sensors system is implemented by double chip integration and the active interface circuit area is about 3.2 × 2 mm. The TMR sensors system consumes 20 mW at a single 5 V supply voltage. The TMR sensors system can achieve a linearity of 0.3% at full scale range (±105 nT) and a resolution of 0.25 nT/Hz1/2(@1Hz).

Sensitivity Enhanced Photoacoustic Imaging Using a High-Frequency PZT Transducer with an Integrated Front-End Amplifier.

Photoacoustic (PA) imaging is a hybrid imaging technique that can provide both structural and functional information of biological tissues. Due to limited permissible laser energy deposited on tissues, highly sensitive PA imaging is required. Here, we developed a 20 MHz lead zirconium titanate (PZT) transducer (1.5 mm × 3 mm) with front-end amplifier circuits for local signal processing to achieve sensitivity enhanced PA imaging. The electrical and acoustic performance was characterized. Experiments on phantoms and chicken breast tissue were conducted to validate the imaging performance. The fabricated prototype shows a bandwidth of 63% and achieves a noise equivalent pressure (NEP) of 0.24 mPa/√Hz and a receiving sensitivity of 62.1 μV/Pa at 20 MHz without degradation of the bandwidth. PA imaging of wire phantoms demonstrates that the prototype is capable of improving the detection sensitivity by 10 dB compared with the traditional transducer without integrated amplifier. In addition, in vitro experiments on chicken breast tissue show that structures could be imaged with enhanced contrast using the prototype and the imaging depth range was improved by 1 mm. These results demonstrate that the transducer with an integrated front-end amplifier enables highly sensitive PA imaging with improved penetration depth. The proposed method holds the potential for visualization of deep tissue structures and enhanced detection of weak physiological changes.

Analysis and design of a transimpedance amplifier based front-end circuit for capacitance measurements

In this study, transimpedance amplifier based front-end circuits which can be employed to measure small capacitances were designed, analyzed and simulated using analog electronic circuit simulator. The front-end circuit converts the current flowing through the measured capacitance into a modulated voltage value which contains information regarding the desired capacitance. The frequency-domain, time-domain, stability and noise analyzes were carried out numerically and in simulation environment using a circuit simulator. The analytical, numerical and simulation results can be used to design optimized, precise and stable transimpedance amplifiers with low-noise value. The measured capacitance value was 10 pF which is low enough to simulate various real-world applications. Three commercially available, off-the-shelf operational amplifiers with different peripheral passive components were employed for computer based analysis. The designed transimpedance amplifiers are suitable to connect with capacitance extraction circuits which use analog or digital demodulation techniques.

Millimeter-Scale Node-to-Node Radio Using a Carrier Frequency-Interlocking IF Receiver for a Fully Integrated 4$\times$ 4$\times$ 4 mm3 Wireless Sensor Node

Ultralow-power (ULP) mm-scale Internet-of-Things (IoT) platforms enable newly emerging applications such as pervasive agricultural monitoring and biosensing. Although there is an increasing interest in node-to-node communication as defined in Bluetooth v5.0, prior research in mm-scale wireless systems is mostly limited to asymmetric node-to-gateway communications. We present a 2.4-GHz node-to-node communication system for an ultra-small wireless sensor node fully integrated within a 4 $\times $ 4 $\times $ 4 mm3 form factor. The system integrates multiple stacked layers including an RF transceiver, a ULP processor, a photovoltaic (PV) cell, a 32-kHz crystal, and a 3-D magnetic dipole antenna. The transceiver front-end circuit is co-designed with a printed 3-D magnetic dipole antenna to form a power oscillator for the transmitter (TX) as well as a $Q$ -enhanced amplifier (QEA) for the receiver (RX). A new carrier frequency-interlocking IF architecture successfully mitigates the TX–RX carrier frequency synchronization challenge that is critical to the mm-scale radio systems. The complete system achieves −94-dBm sensitivity with 97- $\mu \text {W}$ power consumption and −12.6-dBm equivalent isotropically radiated power (EIRP). Standalone operation of a sensor node is demonstrated through bi-directional wireless communication to another sensor node over 1-m distance in real, uncontrolled wireless channels.

CMOS Transimpedance Amplifiers for Biomedical Applications: A Comparative Study

Recently, different medical devices have emerged and utilized in a numerous health care fields such as pulse oximetry, cuffless blood pressure using Photoplethysmogram (PPG), noninvasive blood glucose measuring, and Near Infrared Spectroscopy (NIRS). Those devices are very similar in their analog front end circuit which is a transimpedance amplifier (TIA). Many different TIA topologies have appeared in different optoelectronic fields which make the choice of the best TIA topology for a certain application a challenging task. In this regard, this paper presents a comparison between state of the art, previously published TIA topologies. All topologies are simulated at four different simulation cases to account for various design scenarios. The topologies are simulated with 10 pF photodiode (PD) input capacitance and 5 KHz bandwidth (BW) while optimizing for two different targets; one time for minimum input noise and the other for minimum power consumption. Moreover, the same procedures are performed with 2 pF PD and 100 MHz BW to account for higher BW demanding applications. The studied topologies are compared according to their transimpedance gain, power consumption, total input referred noise current, and dynamic range (DR) to expose their relative merits. A noise and a transimpedance gain mathematical models are also presented for each topology to assist the comparison. Recommendations to designers on which TIA to select in a certain application are concluded according to the obtained results.

A Front-End Amplifier With Current Compensation Feedback Input Impedance Booster for Neural Signal Applications

In integrated circuit form, the front-end amplifier (FEA) determines the fidelity of the biosignal detection, signal-to-noise ratio, power consumption and detector size for the future multi-channel neural signal recording systems and applications. Especially for the high-density implantable applications, a higher input impedance reduces the signal attenuation (with respect to the high-impedance miniature electrodes), and lowers the current into the tissue (to avoid the overheating damage). In this paper, an input impedance booster with current compensation feedback technique is proposed, it neutralizes any currents generated at input of FEA without affecting the gain. It substantially yields a high input impedance across process and device mismatches. The proposed front-end circuit is implemented on a $0.18\mu \text{m}$ CMOS process, it achieves an input impedance of approximately 60 $\text{G}\Omega $ , and CMRR of 61 dB with 57 dB PSRR. The input-referred noise is approximately $5.6~\mu \text{v}/\surd $ Hz while consuming $7.6~\mu \text{W}$ in 0. 025mm2chip area.

A High-Temperature, Low-Noise Readout ASIC for MEMS-Based Accelerometers.

This paper presents the development and measurement results of a complementary metal oxide semiconductor (CMOS) readout application-specific integrated circuit (ASIC) for bulk-silicon microelectromechanical system (MEMS) accelerometers. The proposed ASIC converts the capacitance difference of the MEMS sensor into an analog voltage signal and outputs the analog signal with a buffer. The ASIC includes a switched-capacitor analog front-end (AFE) circuit, a low-noise voltage reference generator, and a multi-phase clock generator. The correlated double sampling technique was used in the AFE circuits to minimize the low-frequency noise of the ASIC. A programmable capacitor array was implemented to compensate for the capacitance offset of the MEMS sensor. The ASIC was developed with a 0.18 μm CMOS process. The test results show that the output noise floor of the low-noise amplifier was −150 dBV/√Hz at 100 Hz and 175 °C, and the sensitivity of the AFE was 750 mV/pF at 175 °C. The output noise floor of the voltage reference at 175 °C was −133 dBV/√Hz at 10 Hz and −152 dBV/√Hz at 100 Hz.

Towards Wearable and Flexible Sensors and Circuits Integration for Stress Monitoring.

Excessive stress is one of the main causes of mental illness. Long-term exposure of stress could affect one's physiological wellbeing (such as hypertension) and psychological condition (such as depression). Multisensory information such as heart rate variability (HRV) and pH can provide suitable information about mental and physical stress. This paper proposes a novel approach for stress condition monitoring using disposable flexible sensors. By integrating flexible amplifiers with a commercially available flexible polyvinylidene difluoride (PVDF) mechanical deformation sensor and a pH-type chemical sensor, the proposed system can detect arterial pulses from the neck and pH levels from sweat located in the back of the body. The system uses organic thin film transistor (OTFT)-based signal amplification front-end circuits with modifications to accommodate the dynamic signal ranges obtained from the sensors. The OTFTs were manufactured on a low-cost flexible polyethylene naphthalate (PEN) substrate using a coater capable of Roll-to-Roll (R2R) deposition. The proposed system can capture physiological indicators with data interrogated by Near Field Communication (NFC). The device has been successfully tested with healthy subjects, demonstrating its feasibility for real-time stress monitoring.

Design of Magnetic Resonance Sounding Antenna and Matching Circuit for the Risk Detection of Tunnel Water-Induced Disasters

The magnetic resonance sounding (MRS) method can noninvasively, directly, and quantitatively detect groundwater and forecast the potential for a water-induced disaster during tunnel construction. However, due to the spatial limitations of underground engineering, the signal-to-noise ratio (SNR) of the receiving signal is low (<; 1), which severely limits the reliability of the disaster warning. Thus, the question of how to design the meter-scale antenna and improve the SNR has become the bottleneck that restricts the successful application of the underground MRS method. To address this problem, we comprehensively consider the factors of detection depth, signal amplitude, and antenna size and weight using theoretical calculations and model simulations in this paper. We determine that an 8-turn transmitting antenna and a 30-turn receiving antenna with both side lengths of 6 m constitute an effective combination for achieving reliable detection of large water-bearing structures. Meanwhile, we propose a front-end matching circuit for a high-inductance antenna to solve the problem of attenuation of the signal amplitude due to high impedance and successfully increase the SNR from 1.12 to 5.13. Finally, in the tunnel of the Shanghai-Kunming high-speed railway of China, we perform the field measurement of an underground river and validate the practicability of the proposed antenna and matching circuit.