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 postprocessing of the in-phase and quadrature components would otherwise deteriorate the stability, accuracy, and sensitivity. © 1991 IEEE

Varadarajan Jagadeesh Kumar

Department of Electrical Engineering

H. O. Modi

Panchapagesa Sankaran

AMPLIFIERS, FEEDBACK

ELECTRIC MEASUREMENTS

ELECTRONIC CIRCUITS, PHASE CHANGER

AMPLITUDE DETECTION

CLOSED LOOP DETECTION

Feedback

instrumentation

phase sensitive detection

Signal detection

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Feedback compensated synchronous and multiplier type phase sensitive detectors

IEEE Transactions on Instrumentation and Measurement

Two circuits which accept two sinusoidal waveforms of same frequency with phase difference Ø and provides two dc output voltages in which one dc output voltage is proportional to the quadrature component sin Ø and the another is proportional to the in-phase component cos Ø, by using (1) sampling and (2) switching–sampling techniques, are described in this article. In sampling-type phase-sensitive detector (PSD), a phase-shifted signal VI of peak value VS is sampled by a sampling pulse generated during positive zero crossings of the reference signal VR. Then the sampled output will be VQ = VS sin θ, where θ is the phase difference between VI and VR. This is illustrated graphically in this article. In the switching-type PSD, the need of a 90° phase shifter is eliminated to obtain quadrature component. Verification of the feasibility of circuit configuration is established by way of test results on a proto type. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

International Journal of Electronics Letters

Sampling and switching–sampling-type phase-sensitive detectors

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. © 2014 IEEE.

IEEE Transactions on Biomedical Circuits and Systems

A multi-electrode electric field based sensing system for ophthalmic anesthesia training

A phase meter with a switched-capacitor all-pass network as a controlled phase shifter within a feedback loop has been constructed. This phase meter works on the feedback compensation principle. Satisfactory operation of the device is possible, even if the signal is overwhelmed by noise and DC offsets, for the input phase range of - pi /2< Phi < pi /2 radians. The influence of noise and loop parameters on the phase jitter and acquisition time are studied using experimental results and by simulation.

Measurement Science and Technology

Performance of a compensating phase meter with a switched-capacitor all-pass network

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 < ø < +π/2 under signal to noise ratios as low as -10 dB 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. © 1992, The Institution of Electrical Engineers. All rights reserved.

Electronics Letters

Novel phase meter using narrow pulse switched capacitor phase shifter

IEE Sixteenth Saraga Colloquium on Digital and Analogue Filters and Filtering Systems

Dynamic-range optimisation of second-order integrator-loop active filters

IEEE Transactions on Circuits and Systems

An improved Wien bridge oscillator

Extending the frequency range of a Wien-bridge oscillator using composite operational amplifiers

International Journal of Electrical Engineering Education

The Wien Bridge Oscillator Incorporating An Op. Amp as the Active Element

High-frequency design of the Wien-bridge oscillator using composite amplifiers

Feedback Compensated Synchronous and Multiplier Type Phase Sensitive Detectors

Journal	IEEE Transactions on Instrumentation and Measurement
ISSN	00189456
Open Access	No