Feedback compensated synchronous and multiplier type phase sensitive detectors
TL;DR: In this paper, a feedback-compensated phase sensitive detection (PSD) algorithm is proposed, which is suitable for both synchronous and multiplier modes of implementation, and provides a DC output proportional to the amplitude of the measurand.
Abstract: A feedback technique for phase sensitive detection (PSD) is developed, which is suitable for both synchronous and multiplier modes of implementation. The feedback-compensated PSD straightaway provides a DC output proportional to the amplitude of the measurand. The technique is very useful in a noisy environment where post-processing of the in-phase and quadrature components would otherwise deteriorate the stability, accuracy, and sensitivity. Quantitative comparison of the extent of compensation obtained experimentally with that estimated by PC-simulation indicates good agreement. >
Citations
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TL;DR: A novel differential synchronous demodulator is presented that uses the on-off switching characteristic of the power supply in autonomous systems as the control signal for demodulation.
Abstract: In this paper, a novel differential synchronous demodulator is presented that uses the on-off switching characteristic of the power supply in autonomous systems as the control signal for demodulation. The proposed circuit, which uses only an op amp and a double-pole double-throw switch, can be useful in sensor nodes for sensor networks or distributed data-acquisition systems involving ac sensors or impedance measurements. Three prototype demodulators have been implemented using op amps with different power-bandwidth characteristics, and their common-mode rejection ratio (CMRR), nonlinearity, and initial transient were characterized. The working of the circuit when supplied by a piezoelectric energy converter is also verified.
13 citations
24 Apr 2006
TL;DR: In this paper, a differential synchronous demodulator is presented that uses the on-off switching characteristic of the power supply in autonomous systems as control signal for demodulation.
Abstract: A novel differential synchronous demodulator is presented that uses the on-off switching characteristic of the power supply in autonomous systems as control signal for demodulation. The proposed circuit, which uses a single op amp and SPDT switch, can be useful in sensors networks or distributed data acquisition systems involving ac sensors or impedance measurements. A prototype demodulator yields a nonlinearity of 0.8% FSR and CMRR = 47 dB at 15 kHz for unity gain. The feasibility of the circuit when supplied by a piezoelectric energy converter is also verified.
6 citations
Cites methods from "Feedback compensated synchronous an..."
...Currently available demodulators for ac sensors or impedance-based sensing are either digital [4] or analog, based on analog multiplication plus filtering [5] or on synchronous switching [ 6 ]....
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TL;DR: An anatomically accurate, rapid-prototyped manikin based training system for ophthalmic anesthetic blocks and the proposed capacitive sensing scheme has been validated by tests performed on a prototype system, thus demonstrating its usefulness for practical training purposes.
Abstract: Local anesthesia administration prior to ophthalmic surgery involves inserting a syringe needle into a confined intraorbital space at the proper position, angle and depth During this procedure ocular structures must remain unhurt and systemic complications must be avoided while achieving quick akinesia and analgesia Animal cadavers do not emulate human anatomy accurately and human subject based training entails risk to the patient Therefore, a training system that closely replicates the human ocular and orbital anatomy and provides the trainee with real-time feedback on the safety and effectiveness of the block administered would help reduce risks involved with real life procedures This paper presents an anatomically accurate, rapid-prototyped manikin based training system for ophthalmic anesthetic blocks The depth of penetration of the needle, the proximity of the needle to extraocular muscles and the touch of the needle to the muscles or optic nerve is detected by a multi-electrode electric field/capacitive sensing system The eye structure of the manikin does not have any electrical connections to it, rendering it replaceable, thus, enabling the emulation of anatomical variations due to pathologies of the eye A virtual instrument measures and computes the position of the needle and displays it to the trainee through an intuitive GUI with a 3D display of the orbital anatomy The proposed capacitive sensing scheme has been validated by tests performed on a prototype system, thus demonstrating its usefulness for practical training purposes
5 citations
Cites background or methods from "Feedback compensated synchronous an..."
...Synchronous demodulation improves the signalto-noise ratio by constricting the detection bandwidth to the signal frequency thereby reducing noise power in the output [20], [21] making the measurement system less sensitive to external electrical disturbances....
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...the receiver electrode) is prone to other interfering sources, a highly proven method of synchronous demodulation [20], [21]...
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TL;DR: In this article, a phase meter with a switched capacitor phase shifter (SCPS) is described, which is a nonlinear feedback device that relies on the phase compensation principle and works satisfactorily phase range −π/2 < π < + π/2 under signal to noise ratios as low as −10dB and DC offsets as high as the input signal plus noise peak in the signal channel.
Abstract: A novel phase meter with a switched capacitor phase shifter (SCPS) is described. This phase meter is a nonlinear feedback device and relies on the phase compensation principle. This works satisfactorily phase range –π/2 < π < + π/2 under signal to noise ratios as low as –10dB and DC offsets as high as the input signal-plus-noise peak in the signal channel. The influence of noise on the output phase noise is studied. Its steady state error curve is presented for two representative noise levels.
4 citations
TL;DR: In this paper, a triangular wave-referenceded time division multipliers are configured to work as squarer and the squared voltages are added and given to non-inverting input of an op-amp OA.
Abstract: A circuit that accepts two input dc voltages V1 and V2 and provides output dc voltage by using three triangular wave-referenced time division multipliers is described in this paper. One input voltage is given to one multiplier and the other input voltage is given to another multiplier. Both multipliers are configured to work as squarer. The squared voltages are added and given to non-inverting input of an op-amp OA. The third multiplier which is also configured as a squarer is given at the negative feedback path of the op-amp OA. The op-amp OA output is the output voltage VO. The conventional multipliers used are the author's triangular wave-referenced time division multipliers. Verification of the feasibility of the circuit is established by way of test results on a prototype.
1 citations
Cites methods from "Feedback compensated synchronous an..."
...Few examples are (i) phase-sensitive detectors (PSDs) which play an important role in impedance measurement and power measurement etc., (ii) construction of signal-envelope circuits, (iii) diversity combiner circuits, (iv) radiometer circuits, and (v) in other applications in which the power of separate waveforms must be added....
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...The PSD [11] extracts the impedance voltage into the quadrature component VQ and the in-phase component VI....
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References
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TL;DR: In this article, phase sensitive detection is formalized in order that its operation can be understood and its practical use optimized, and the theory explains how narrow bandwidth amplification is achieved in order to reduce the noise content of a measurand and how the process can be considered simply as a multiplier followed by a low-pass filter.
Abstract: Phase sensitive detection is formalized in order that its operation can be understood and its practical use optimized. The theory explains how narrow bandwidth amplification is achieved in order to reduce the noise content of a measurand and how the process can be considered simply as a multiplier followed by a low-pass filter. The responses to various excitation and measurand forms are derived for signals ranging from the simple sinusoids to the more complicated signals produced when modulating interference fringes and stabilized laser cavities.
150 citations
TL;DR: The basic principles of optical methods for measuring voltage and current at high voltage are presented in this paper, including the magneto-optic effect, the electroelectrical effect and the electrogyration effect, plus various detection and noise reduction techniques.
Abstract: The basic principles of optical methods for measuring voltage and current at high voltage are presented. These include the magneto-optic effect, the electro-optic effect and the electrogyration effect, plus various detection and noise reduction techniques. Both free path and enclosed path devices which have been constructed on these principles are described. The viability of these devices for the electricity supply industry is assessed.
57 citations
TL;DR: In this article, an active circuit which simultaneously provides unity gain and a constant phase shift of 90° for sinusoidal inputs of varying frequency is described, which employs the voltage derived from a quadrature detector to modify the resistance of a voltage-controlled resistor incorporated in an active all-pass phase shifter circuit.
Abstract: An active circuit which simultaneously provides unity gain and a Constant phase shift of 90° for sinusoidal inputs of varying frequency is described. It employs the voltage derived from a quadrature detector to modify the resistance of a voltage-controlled resistor incorporated in an active allpass phase shifter circuit.
24 citations
TL;DR: In this article, a phase-locked loop containing a voltage-controlled oscillator synchronised to a harmonic of its fundamental output frequency was used to form an attractive digital phase shifter providing low phase error with relatively simple circuitry and control requirements.
Abstract: A phase-locked loop containing a voltage-controlled oscillator (v.c.o.) synchronised to a harmonic of its fundamental output frequency may be used to form an attractive digital phase shifter providing low phase error with relatively simple circuitry and control requirements. Phase increments of 2π/n radians are obtained, where n is the order of harmonic used.
10 citations
TL;DR: In this article, the authors describe an operational amplifier circuit which gives a constant (± 0.1°) phase shift and a constant unity gain to a sinusoidal signal, over a frequency band of range ± 2%.
Abstract: The letter describes an operational amplifier circuit which gives a constant (±0.1°) phase shift and a constant (±0.1%) unity gain to a sinusoidal signal, over a frequency band of range ±2%. The circuit incorporates two standard phase-shifters with different characteristics, deployed so that their phase errors mutually cancel as the frequency deviates from its central value. The device has been used as a phase-shifter in a precise negative phase sequence current measurement circuit in a power system.
7 citations