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14 pages, 3092 KiB

Open AccessArticle

A Novel Method for Remaining Useful Life Prediction of RF Circuits Based on the Gated Recurrent Unit–Convolutional Neural Network Model

by Wanyu Yang, Kunping Wu, Bing Long and Shulin Tian

Sensors 2024, 24(9), 2841; https://doi.org/10.3390/s24092841 - 29 Apr 2024

Viewed by 322

Abstract

The remaining useful life (RUL) prediction of RF circuits is an important tool for circuit reliability. Data-driven-based approaches do not require knowledge of the failure mechanism and reduce the dependence on knowledge of complex circuits, and thus can effectively realize RUL prediction. This [...] Read more.

The remaining useful life (RUL) prediction of RF circuits is an important tool for circuit reliability. Data-driven-based approaches do not require knowledge of the failure mechanism and reduce the dependence on knowledge of complex circuits, and thus can effectively realize RUL prediction. This manuscript proposes a novel RUL prediction method based on a gated recurrent unit–convolutional neural network (GRU-CNN). Firstly, the data are normalized to improve the efficiency of the algorithm; secondly, the degradation of the circuit is evaluated using the hybrid health score based on the Euclidean and Manhattan distances; then, the life cycle of the RF circuits is segmented based on the hybrid health scores; and finally, an RUL prediction is carried out for the circuits at each stage using the GRU-CNN model. The results show that the RMSE of the GRU-CNN model in the normal operation stage is only 3/5 of that of the GRU and CNN models, while the prediction uncertainty is minimized. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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18 pages, 5986 KiB

Open AccessArticle

A Time-of-Flight Image Sensor Using 8-Tap P-N Junction Demodulator Pixels

by Ryosuke Miyazawa, Yuya Shirakawa, Kamel Mars, Keita Yasutomi, Keiichiro Kagawa, Satoshi Aoyama and Shoji Kawahito

Sensors 2023, 23(8), 3987; https://doi.org/10.3390/s23083987 - 14 Apr 2023

Viewed by 2618

Abstract

This paper presents a time-of-flight image sensor based on 8-Tap P-N junction demodulator (PND) pixels, which is designed for hybrid-type short-pulse (SP)-based ToF measurements under strong ambient light. The 8-tap demodulator implemented with multiple p-n junctions used for modulating the electric potential to [...] Read more.

This paper presents a time-of-flight image sensor based on 8-Tap P-N junction demodulator (PND) pixels, which is designed for hybrid-type short-pulse (SP)-based ToF measurements under strong ambient light. The 8-tap demodulator implemented with multiple p-n junctions used for modulating the electric potential to transfer photoelectrons to eight charge-sensing nodes and charge drains has an advantage of high-speed demodulation in large photosensitive areas. The ToF image sensor implemented using 0.11 µm CIS technology, consisting of an 120 (H) × 60 (V) image array of the 8-tap PND pixels, successfully works with eight consecutive time-gating windows with the gating width of 10 ns and demonstrates for the first time that long-range (>10 m) ToF measurements under high ambient light are realized using single-frame signals only, which is essential for motion-artifact-free ToF measurements. This paper also presents an improved depth-adaptive time-gating-number assignment (DATA) technique for extending the depth range while having ambient-light canceling capability and a nonlinearity error correction technique. By applying these techniques to the implemented image sensor chip, hybrid-type single-frame ToF measurements with depth precision of maximally 16.4 cm (1.4% of the maximum range) and the maximum non-linearity error of 0.6% for the full-scale depth range of 1.0–11.5 m and operations under direct-sunlight-level ambient light (80 klux) have been realized. The depth linearity achieved in this work is 2.5 times better than that of the state-of-the-art 4-tap hybrid-type ToF image sensor. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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19 pages, 659 KiB

Open AccessArticle

Sensing Algorithm to Estimate Slight Displacement and Posture Change of Target from Monocular Images

by Tadashi Ito, Hiroo Yoneyama, Yuto Akiyama, Tomonori Hagiwara and Shunsuke Ezawa

Sensors 2023, 23(2), 851; https://doi.org/10.3390/s23020851 - 11 Jan 2023

Cited by 2 | Viewed by 1498

Abstract

Various types of displacement sensors, which measure position changes of object, have been developed depending on the type and shape of the object under measurement, measurement range of the amount of displacement, required accuracy, and application. We are developing a new type of [...] Read more.

Various types of displacement sensors, which measure position changes of object, have been developed depending on the type and shape of the object under measurement, measurement range of the amount of displacement, required accuracy, and application. We are developing a new type of displacement sensor that is image-based, capable of measuring changes in 6DOF (3D position and orientation) of an object simultaneously, and is compact and low-cost. This displacement sensor measures the 6DOF of an object using images obtained by a monocular vision system. To confirm the usefulness of the proposed method, experimental measurements were conducted using a simple and inexpensive optical system. In this experiment, we were able to accurately measure changes of about 0.25 mm in displacement and 0.1 deg in inclination of the object at a distance of a few centimeters, and thus confirming the usefulness of the proposed method. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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12 pages, 4523 KiB

Open AccessCommunication

Improved Quasi-Z-Source High Step-Up DC–DC Converter Based on Voltage-Doubler Topology

by Toru Sai, Younghyun Moon and Yasuhiro Sugimoto

Sensors 2022, 22(24), 9893; https://doi.org/10.3390/s22249893 - 15 Dec 2022

Cited by 5 | Viewed by 1484

Abstract

The step-up DC–DC converter is widely used for applications such as IoT sensor nodes, energy harvesting, and photovoltaic (PV) systems. In this article, a new topological quasi-Z-source (QZ) high step-up DC–DC converter for the PV system is proposed. The topology of this converter [...] Read more.

The step-up DC–DC converter is widely used for applications such as IoT sensor nodes, energy harvesting, and photovoltaic (PV) systems. In this article, a new topological quasi-Z-source (QZ) high step-up DC–DC converter for the PV system is proposed. The topology of this converter is based on the voltage-doubler circuits. Compared with a conventional quasi-Z-source DC–DC converter, the proposed converter features low voltage ripple at the output, the use of a common ground switch, and low stress on circuit components. The new topology, named a low-side-drive quasi-Z-source boost converter (LQZC), consists of a flying capacitor (C_F), the QZ network, two diodes, and a N-channel MOS switch. A 60 W laboratory prototype DC–DC converter achieved 94.9% power efficiency. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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17 pages, 6238 KiB

Open AccessArticle

Modified Triple-Tuned Bandpass Filter with Two Concurrently Tuned Transmission Zeros

by Mirosław Magnuski, Artur Noga, Maciej Surma and Dariusz Wójcik

Sensors 2022, 22(24), 9760; https://doi.org/10.3390/s22249760 - 13 Dec 2022

Cited by 2 | Viewed by 1648

Abstract

In this paper, a modified triple-tuned microstrip bandpass filter is presented. The filter consists of inductively cross-coupled resonators tuned with varactors. The application of the additional source-load couplings together with resonator branch swapping results in two transmission zeros tuned concurrently with operating frequency. [...] Read more.

In this paper, a modified triple-tuned microstrip bandpass filter is presented. The filter consists of inductively cross-coupled resonators tuned with varactors. The application of the additional source-load couplings together with resonator branch swapping results in two transmission zeros tuned concurrently with operating frequency. These transmission zeros placed on both sides of the passband significantly increase slope steepness in transition bands. The example filter tuned from 0.36 to 0.78 GHz and controlled by a single voltage was manufactured and validated by measurements. It has a constant fractional bandwidth of 11%, low in-band insertion loss ranging from 1.8 to 2.5 dB, and out-of-band attenuation up to 5 GHz without parasitic passbands. The obtained filter parameters made it useful for preselector networks. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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17 pages, 11098 KiB

Open AccessArticle

Circuit Techniques to Improve Low-Light Characteristics and High-Accuracy Evaluation System for CMOS Image Sensor

by Norihito Kato, Fukashi Morishita, Satoshi Okubo and Masao Ito

Sensors 2022, 22(16), 6040; https://doi.org/10.3390/s22166040 - 12 Aug 2022

Viewed by 2432

Abstract

The surveillance cameras we focus on target the volume zone, and area reduction is a top priority. However, by simplifying the ADC comparator, we face a new RUSH current issue, for which we propose a circuit solution. This paper proposes two novel techniques [...] Read more.

The surveillance cameras we focus on target the volume zone, and area reduction is a top priority. However, by simplifying the ADC comparator, we face a new RUSH current issue, for which we propose a circuit solution. This paper proposes two novel techniques of column-ADC for surveillance cameras to improve low-light characteristics. RUSH current compensation reduces transient current consumption fluctuations during AD conversion and utilizing timing shift ADCs decreases the number of simultaneously operating ADCs. These proposed techniques improve low-light characteristics because they reduce the operating noise of the circuit. In order to support small signal measurement, this paper also proposes a high-accuracy evaluation system that can measure both small optical/electrical signals in low-light circumstances. To demonstrate these proposals, test chips were fabricated using a 55 nm CIS process and their optical/electrical characteristics were measured. As a result, low-light linearity as optical characteristics were reduced by 63% and column interference (RUSH current) as an electrical characteristic was also reduced by 50%. As for the high-accuracy evaluation system, we confirmed that the inter-sample variation of column interference was 0.05 LSB. This ADC achieved a figure-of-merit (FoM) of 0.32 e-·pJ/step, demonstrating its usefulness for other ADC architectures while using a single-slope-based simple configuration. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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14 pages, 3432 KiB

Open AccessArticle

High Gain, Low Noise and Power Transimpedance Amplifier Based on Second Generation Voltage Conveyor in 65 nm CMOS Technology

by José C. García-Montesdeoca, Juan A. Montiel-Nelson and Javier Sosa

Sensors 2022, 22(16), 5997; https://doi.org/10.3390/s22165997 - 11 Aug 2022

Cited by 1 | Viewed by 2473

Abstract

A transimpedance amplifier (TIA) based on a voltage conveyor structure designed for high gain, low noise, low distortion, and low power consumption is presented in this work. Following a second-generation voltage conveyor topology, the current and voltage blocks are a regulated cascode amplifier [...] Read more.

A transimpedance amplifier (TIA) based on a voltage conveyor structure designed for high gain, low noise, low distortion, and low power consumption is presented in this work. Following a second-generation voltage conveyor topology, the current and voltage blocks are a regulated cascode amplifier and a down converter buffer, respectively. The proposed voltage buffer is designed for low distortion and low power consumption, whereas the regulated cascode is designed for low noise and high gain. The resulting TIA was fabricated in 65 nm CMOS technology for logic and mixed-mode designs, using low-threshold voltage transistors and a supply voltage of ±1.2 V. It exhibited a 52 dBΩ transimpedance gain and a 1.1 GHz bandwidth, consuming 55.3 mW using a ±1.2 V supply. Our preamplifier stage, based on a regulated cascode, was designed considering detector capacitance, bonding wire, and packaging capacitance. The voltage buffer was designed for low-power consumption and low distortion. The measured input-referred noise of the TIA was 22 pA/√Hz. The obtained total harmonic distortion of the TIA was close to 5%. In addition, the group delay is constant for the considered bandwidth. Comparisons against published results in terms of area (A), power consumption (P), bandwidth (BW), transimpedance gain (G), and noise (N) are were performed. Both figures of merit FoMs—the ratio √ (G × BW) and P × A—and FoM/N values demostrated the advantages of the proposed approach. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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14 pages, 5578 KiB

Open AccessCommunication

A Design of 10-Bit Asynchronous SAR ADC with an On-Chip Bandgap Reference Voltage Generator

by Deeksha Verma, Khuram Shehzad, Sung Jin Kim, Young Gun Pu, Sang-Sun Yoo, Keum Cheol Hwang, Youngoo Yang and Kang-Yoon Lee

Sensors 2022, 22(14), 5393; https://doi.org/10.3390/s22145393 - 19 Jul 2022

Cited by 3 | Viewed by 4567

Abstract

A proposed prototype of a 10-bit 1 MS/s single-ended asynchronous Successive Approximation Register (SAR) Analog-to-Digital Converter (ADC) with an on-chip bandgap reference voltage generator is fabricated with 130 nm technology. To optimize the power consumption, static, and dynamic performance, several techniques have been [...] Read more.

A proposed prototype of a 10-bit 1 MS/s single-ended asynchronous Successive Approximation Register (SAR) Analog-to-Digital Converter (ADC) with an on-chip bandgap reference voltage generator is fabricated with 130 nm technology. To optimize the power consumption, static, and dynamic performance, several techniques have been proposed. A dual-path bootstrap switch was proposed to increase the linearity sampling. The Voltage Common Mode (VCM)-based Capacitive Digital-to-Analog Converter (CDAC) switching technique was implemented for the CDAC part to alleviate the switching energy problem of the capacitive DAC. The proposed architecture of the two-stage dynamic latch comparator provides high speed and low power consumption. Moreover, to achieve faster bit conversion with an efficient time sequence, asynchronous SAR logic with an internally generated clock is implemented, which avoids the requirement of a high-frequency external clock, as all conversions are carried out in a single clock cycle. The proposed error amplifier-based bandgap reference voltage generator provides a stable reference voltage to the ADC for practical implementation. The measurement results of the proposed SAR ADC, including an on-chip bandgap reference voltage generator, show an Effective Number of Bits (ENOB) of 9.49 bits and Signal-to-Noise and Distortion Ratio (SNDR) of 58.88 dB with 1.2 V of power supply while operating with a sampling rate of 1 MS/s. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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19 pages, 3829 KiB

Open AccessArticle

Identifying A(s) and β(s) in Single-Loop Feedback Circuits Using the Intermediate Transfer Function Approach

by Gordon Walter Roberts

Sensors 2022, 22(11), 4303; https://doi.org/10.3390/s22114303 - 6 Jun 2022

Viewed by 1945

Abstract

It is common practice to model the input–output behavior of a single-loop feedback circuit using the two parameters, A and β. Such an approach was first proposed by Black to explain the advantages and disadvantages of negative feedback. Extensive theories of system [...] Read more.

It is common practice to model the input–output behavior of a single-loop feedback circuit using the two parameters, A and β. Such an approach was first proposed by Black to explain the advantages and disadvantages of negative feedback. Extensive theories of system behavior (e.g., stability, impedance control) have since been developed by mathematicians and/or control engineers centered around these two parameters. Circuit engineers rely on these insights to optimize the dynamic behavior of their circuits. Unfortunately, no method exists for uniquely identifying A or β in terms of the components of the circuit. Rather, indirect methods, such as the injection method of Middlebrook or the break-the-loop approach proposed by Rosenstark, compute the return ratio RR of the feedback loop and inferred the parameters A and β. While one often assumes that the zeros of (1 + RR) are equal to the zeros of (1 + A × β), i.e., the closed-loop poles are equivalent, this is not true in general. It is the objective of this paper to present an exact method to uniquely identify each feedback parameter, A or β, in terms of the circuit components. Further, this paper will identify the circuit conditions for which the product of A × β leads to the correct closed-loop poles. Full article

(This article belongs to the Special Issue Sensors and Analog Front-End Circuits for IoT Systems and High Sensitivity Measurements)

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