Noncontact Proximity Vital Sign Sensor Based on PLL for Sensitivity Enhancement

Hong, Young Ho; Kim, Sang Gyu; Kim, Byung-Hyun; Ha, Sung Jae; Lee, Hee Jo; Yun, Gi-Ho; Yook, Jong Gwan

doi:10.1109/tbcas.2013.2280913

Cited by 34 publications

(18 citation statements)

References 29 publications

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“…External circuit conditions such as frequency pulling by load variation or frequency pushing caused by power supply voltage variation can also lead to erratic behaviour. For example [2] gave a detailed study on injection locked oscillator temperature variation in order to ensure that the medical sensor presented was reliable enough for normal everyday use. The scenario of oscillators drifting out of lock can quite easily occur since oscillators used for injection locking often exploit low Q circuits to maximise the locking range.…”

Section: Nb Buchanan Vf Fuscomentioning

confidence: 99%

Injection‐locked oscillator lock detector

Buchanan

Fusco

2016

Electron. lett.

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This letter presents a simple circuit that is able to indicate if an injection locked oscillator is in the locked condition by providing a "high" or "low" output. The detector is compatible with most injection locked oscillators as all that is required is access to the low frequency bias circuit, with no direct access needed to the RF/microwave signals. To prove the universal nature of the lock detector it is successfully demonstrated practically for two scenarios, (i) a 1 GHz injection locked VCO, (ii) a 60GHz SiGe VCO MMIC.Introduction: Injection locking in oscillators is a well known phenomena [1]. Injection locked oscillators, due their simple architecture, have been used in applications such as medical sensors [2] and frequency dividers for mm-wave PLL's [3]. Low power transmitters for wireless sensor networks [4] have been shown to have improved efficiency by using an injection locked oscillator on their output stage. Injection locked oscillators have been shown in [5] to be capable of low loss clock distribution around a large circuit. In [6] the injection locked oscillator was used in a variety of configurations in order to simplify mm-wave phase locked loop architectures. Despite the potential advantages of injection locked oscillators, the aforementioned applications all have one thing in common, that is, they are rendered completely inoperable if the oscillators are not operating in their injection locked region. In addition, in some applications, e.g. transmitters, may produce unwanted out of band emissions if injection locking is not maintained.Changes in the external environment such as temperature variation can cause unwanted variation in the oscillator's free running frequency. External circuit conditions such as frequency pulling by load variation or frequency pushing caused by power supply voltage variation can also lead to erratic behaviour. For example [2] gave a detailed study on injection locked oscillator temperature variation in order to ensure that the medical sensor presented was reliable enough for normal everyday use. The scenario of oscillators drifting out of lock can quite easily occur since oscillators used for injection locking often exploit low Q circuits to maximise the locking range.What is essential in these injection locking scenarios is a simple method to confirm that the oscillator is in the injection locked condition, i.e. an injection locked oscillator lock detection circuit. There are already existing methods that can determine if an oscillator is injection locked, e.g. by examining its frequency spectrum. Here a non-symmetrical sideband distribution [7] indicates that the oscillator is out of lock. This method is suitable for laboratory testing, but far too complicated to be implemented on a device such as a sensor. Lock detection can also be carried out by feeding the oscillator signal and injection locking signal to a mixer circuit to determine if zero beat frequency is present. In [8] a 60 GHz subharmonically locked oscillator was presented, with a lock detector bas...

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Section: Nb Buchanan Vf Fuscomentioning

confidence: 99%

Injection‐locked oscillator lock detector

Buchanan

Fusco

2016

Electron. lett.

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“…이러한 대표적 구조는 도플러 효과를 이용 한 원거리(또는 근거리) 생체신호를 검출하기 위한 FM-CW, CW 레이더 등이 있다 [6]～ [9] . 반면, 수동형은 송신신 호 없이 신체와 센서 사이의 근접 전자기장의 변화를 이 용하여 호흡 및 심박 신호를 검출하였다 [10]～ [13] . RF 공진 기를 신체에 근접시키면 공진기의 임피던스가 변화되며, 결합된 발진기의 주파수 천이(drift) 현상을 이용하여 검 출해 내는 방식이다.…”

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“…RF 공진 기를 신체에 근접시키면 공진기의 임피던스가 변화되며, 결합된 발진기의 주파수 천이(drift) 현상을 이용하여 검 출해 내는 방식이다. 주파수 천이를 DC로 검출하는 방식 중 SAW 필터와 RF 검출기 [10], [11] , Injection-locking [12] 및 위 상고정루프 [13] 방법 등이 제안되었다. 본 논문에서는 감도 향상을 위해 발진기의 2차 고조파 주파수 변이 및 유사 검출시스템(SAW 필터 및 RF 검출 기)의 조합을 통해 기존 논문 [10] 대비 2배의 검출거리를 갖는 비접촉식 생체신호 측정센서를 제안하였다.…”

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“…근접 전자기장내의 인체 영향이 고려된 평면형 공진기의 단순화된 RLC 회로 모델을 그림 2에 나타내었다. 호흡 및 심박과 같은 신체의 주기적 움직임은 간단히 가변 캐 패시턴스(C pv )로 모델링 [13] 할 수 있다. 가변 캐패시턴스의 변화는 공진기의 입력 임피던스의 변화, 즉 발진주파수의 변경을 의미한다.…”

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“…가변 캐패시턴스의 변화는 공진기의 입력 임피던스의 변화, 즉 발진주파수의 변경을 의미한다. 주기적인 신체의 움직임(호흡 및 심박 활동)의 영향을 고려한 평면형 공진기의 입력 임피던스 는 다음과 같이 표현할 수 있다 [13] . [12] .…”

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Vital Sign Sensor Based on Second Harmonic Frequency Drift of Oscillator

Ku¹,

Hong²,

Lee³

et al. 2016

The Journal of Korean Institute of Electromagnetic Engineering

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In this paper, a vital sign sensor based on impedance variation of resonator is proposed to detect the respiration and heartbeat signals within near-field range as a function of the separation distance between resonator and subject. The sensor consists of an oscillator with a built-in planar type patch resonator, a diplexer for only pass the second harmonic frequency, amplifier, SAW filter, and RF detector. The cardiac activity of a subject such as respiration and heartbeat causes the variation of the oscillation frequency corresponding impedance variation of the resonator within near-field range. The combination of the second harmonic oscillation frequency deviation and the superior skirt frequency of the SAW filter enables the proposed sensor to extend twice detection range. The experimental results reveal that the proposed sensor placed 40 mm away from a subject can reliably detect respiration and heartbeat signals.

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Nanocomposite Multimodal Sensor Array Integrated with Auxetic Structure for an Intelligent Biometrics System

Cheng,

Li,

Lee

et al. 2024

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A multimodal sensor array, combining pressure and proximity sensing, has attracted considerable interest due to its importance in ubiquitous monitoring of cardiopulmonary health‐ and sleep‐related biometrics. However, the sensitivity and dynamic range of prevalent sensors are often insufficient to detect subtle body signals. This study introduces a novel capacitive nanocomposite proximity‐pressure sensor (NPPS) for detecting multiple human biometrics. NPPS consists of a carbon nanotube‐paper composite (CPC) electrode and a percolating multiwalled carbon nanotube (MWCNT) foam enclosed in a MWCNT‐coated auxetic frame. The fractured fibers in the CPC electrode intensify an electric field, enabling highly sensitive detection of proximity and pressure. When pressure is applied to the sensor, the synergic effect of MWCNT foam and auxetic deformation amplifies the sensitivity. The simple and mass‐producible fabrication protocol allows for building an array of highly sensitive sensors to monitor human presence, sleep posture, and vital signs, including ballistocardiography (BCG). With the aid of a machine learning algorithm, the sensor array accurately detects blood pressure (BP) without intervention. This advancement holds promise for unrestricted vital sign monitoring during sleep or driving.

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Noncontact Proximity Vital Sign Sensor Based on PLL for Sensitivity Enhancement

Cited by 34 publications

References 29 publications

Injection‐locked oscillator lock detector

Injection‐locked oscillator lock detector

Vital Sign Sensor Based on Second Harmonic Frequency Drift of Oscillator

Nanocomposite Multimodal Sensor Array Integrated with Auxetic Structure for an Intelligent Biometrics System

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