Active Compensation Method Research Articles

Single electrode dynamic clamp with StdpC

Dynamic clamp is a powerful approach for electrophysiological investigations allowing researchers to introduce artificial electrical components into target neurons to simulate ionic conductances, chemical or electrotonic inputs or connections to other cells. Due to the rapidly changing and potentially large current injections during dynamic clamp, problematic voltage artifacts appear on the electrode used to inject dynamic clamp currents into a target neuron. Dynamic clamp experiments, therefore, typically use two separate electrodes in the same cell, one for recording membrane potential and one for injecting currents. The requirement for two independent electrodes has been a limiting factor for the use of dynamic clamp in applications where dual recordings of this kind are difficult or impossible to achieve. The recent development of an active electrode compensation (AEC) method has overcome some of these prior limitations, permitting artifact-free dynamic clamp experimentation with a single electrode. Here we describe an AEC method for the free dynamic clamp software StdpC. The AEC component of StdpC is the first such system implemented for the use of non-expert users and comes with a set of semi-automated configuration and calibration procedures that facilitate its use. We briefly introduce the AEC method and its implementation in StdpC and then validate it with an electronic model cell and in two different biological preparations.

Feasibility Study to Actively Compensate Deformations of Composite Structure in a Space Environment

An active compensation method for the deformation of composite structures using additional controllable metal parts is proposed, and its feasibility is experimentally investigated in a simulated space environment. Composite specimens are tested in a vacuum chamber, which is able to maintain pressure on the order of 10-3 torr and interior temperature in the range of <TEX>${\pm}30^{\circ}C$</TEX>. The displacement-measuring interferometer system, which consists of a heterodyne HeNe laser and an interferometer, is used to measure the displacement of the whole structure. Meanwhile, the strain of the composite part and temperature of both parts are measured by fiber Bragg grating sensors and thermistors, respectively. The displacement of the composite structure is maintained within a tolerance of <TEX>${\pm}1{\mu}m$</TEX> by controlling the elongation of the metal part, which is bonded to the end of the composite part. Also, the possibility of fiber Bragg grating sensors as control input sensors is successfully demonstrated using a proper corrective factor based on the specimen temperature gradient data.

An effective active phase compensation method for quantum key distribution system

Quantum key distribution (QKD) system must be robust enough in practical communication. The system performance is notably affected by phase drift. For the fiber-based phase-encoded quantum key distribution system, the Faraday-Michelson QKD scheme can auto-compensate the birefringence of fiber, but phase drift caused by environment variations is still a serious problem in practical operation. In this paper, the major schemes to compensate for the phase drift are analyzed in detail and an “five-phase”effective active phase compensation method is proposed. The comparison with other two major active phase compensation schemes also given. The result shows that this method uses less time to acquire the parameter of phase drift with the same precision and it can be used in phase-encoded QKD systems without introducing additional devices.

HISTORY AND PROGRESS OF THE KERWIN–HUELSMAN–NEWCOMB FILTER GENERATION AND OP AMP REALIZATIONS

The history of Kerwin–Huelsman–Newcomb (KHN) second-order filter is reviewed. A generation method of the KHN filter from passive RLC filter is presented. Two alternative forms of the KHN circuit using operational amplifier are reviewed. The effect of finite gain-bandwidth of the op amps is considered and expressions of the actual ω0and Q are given. Two KHN circuits with inherently stable Q factor are also included. Two new partially compensated inverted KHN circuits are introduced. Active compensation methods to improve the KHN and the inverted KHN circuit performance for high Q designs are summarized. Spice simulation results are given. The progress of the KHN realizations using the current conveyor is also summarized briefly.

Eccentricity Compensation Mechanism for Improving Reliability of Removable Performance in Near-Field Optical Disc Drive System

In this paper, we propose the eccentricity-compensating actuator mechanism for near-field (NF) optical disc drives. In this proposed dual-stage compensating actuator mechanism, the disc-spindle unit is actuated instead of the solid immersion lens (SIL) along the tracking axis to cancel out an eccentricity less than 20 µmpp (pp: peak to peak), which is the required criterion for NF discs of 160 nm track pitch. As a result, the proposed method enables the decrease in the required residual tracking error to lower than the criteria of 4.5 nm in NF optical disc drive (ODD) even when using the tracking servo of moderate performance. The proposed active eccentricity compensation method can be effective and applicable to dealing with the eccentricity problem in NF ODD, which we verified experimentally.

HISTORY AND PROGRESS OF THE TOW–THOMAS BI-QUADRATIC FILTER PART I: GENERATION AND OP AMP REALIZATIONS

The history of Tow–Thomas second-order filter is reviewed. Two alternative generation methods of the Tow–Thomas filter are discussed. The first is a generation method from the second-order passive RLC filter and the second is from the multiple feedbacks inverting low-pass filter using a single op amp. Several forms of the circuit are briefly reviewed. Passive and active compensation methods to improve the circuit performance for high-Q designs are summarized. Spice simulation results are included.

磁束反発を利用した能動補償の分離型磁気シールドへの適用

A new active compensation method using magnetic repulsion is presented which is applicable to a separate magnetic shield. A pair of the compensation coil is set on each of the separate shells and generate compensation magnetic field to bend the flux lines of the disturbing magnetic field in order to pass them below and above the magnetic shells. We have applied the method to a small laboratory model and confirmed a large shielding efficiency of the new compensation method. The transverse shielding factor measured perpendicularly to the plane separating two shells was 1.4 for the magnetic field of 10 Hz, 10 μT, when the compensation was off, however, it was larger than 1,000 when the compensation was on.

Analysis of uncompensated Langmuir probe characteristics in radio-frequency discharges revisited

Measurements of the electron temperature, plasma density, and floating and plasma potentials with Langmuir probes in radio-frequency discharges often represent a challenge due to rf oscillations of the plasma potential. These oscillations distort the probe characteristic, resulting in wrong estimates of the plasma parameters. Both active and passive rf compensation methods have previously been used to eliminate rf fluctuation effects on the electron current drawn by an electrostatic probe. These effects on an uncompensated probe have been theoretically and experimentally studied by Garscadden and Emeleus [Proc. Phys. Soc. London 79, 535 (1962)], Boschi and Magistrelli [Nuovo Cimento 29, 487 (1963)], and Crawford [J. Appl. Phys. 34, 1897 (1963)]. They have shown theoretically that, assuming a Maxwellian distribution and sinusoidal plasma-potential oscillation, the electron temperature can be deduced directly from an uncompensated Langmuir probe trace, by taking the natural logarithm of the electron current. It is the purpose of this paper to bring back the attention onto this result, which shows that under certain discharge conditions it is not necessary to build any rf compensation in a Langmuir probe system. Here we present and reference experimental data found on the literature which support this result. Also computational data are presented.

Comparison of an self-organizing migration algorithm with simulated annealing and differential evolution for automated waveform tuning

In this article, the performance of a self-organizing migration algorithm (SOMA), a new stochastic optimization algorithm, has been compared with simulated annealing (SA) and differential evolution (DE) for an engineering application. This application is the automated deduction of 14 Fourier terms in a radio-frequency (RF) waveform to tune a Langmuir probe. Langmuir probes are diagnostic tools used to determine the ion density and the electron energy distribution in plasma processes. RF plasmas are inherently non-linear, and many harmonics of the driving fundamental can be generated in the plasma. RF components across the ion sheath formed around the probe distort the measurements made. To improve the quality of the measurements, these RF components can be removed by an active-compensation method. In this research, this was achieved by applying an RF signal to the probe tip that matches both the phase and amplitude of the RF signal generated from the plasma. Here, seven harmonics are used to generate the waveform applied to the probe tip. Therefore, 14 mutually interacting parameters (seven phases and seven amplitudes) had to be tuned on-line. In previous work SA and DE were applied successfully to this problem, and hence were chosen to be compared with the performance of SOMA. In this application domain, SOMA was found to outperform SA and DE.

Active compensation for ambient magnetic noise in the unshielded environment

An active compensation method is presented as the method of improvement of measuring conditions in an unshielded laboratory room. The disturbing magnetic field is picked up by a SQUID magnetometer. The output signal controlled by electronics feeds the compensation coil set, which generates a magnetic field opposite to the disturbing magnetic field and magnetic ambient noise is reduced. The combination of the active compensation technique and a gradiometer is used to eliminate low-frequency magnetic disturbances. An attenuation of more than 40 dB at low frequencies was obtained. The comparison with other compensation techniques is discussed, as is the problem of whether active compensation reduces magnetic disturbances when changing the measuring position. The active compensation technique is performed in all directions of an orthogonal system.

Determination of electron energy distribution functions in surface wave produced plasmas. II. Measurements

For pt.I see ibid., vol.24, p.1585-93 (1991). Electron energy distribution functions of surface wave produced argon plasmas are measured via second derivatives of Langmuir probe characteristics. An active compensation method for avoiding modifications by the RF electric field is employed. Good agreement with previous numerical solutions of the Boltzmann equation is observed.

Instrumentation amplifiers with improved bandwidth

Active magnitude compensation methods for the finite bandwidth of operational amplifiers when employed in the differential voltage controlled voltage source structures are given. The results are summarized in a table.

Active compensation of opamps

A novel active compensation method for the finite gain bandwidth of operational amplifiers, when used in voltage-controlled voltage source structures, is given. In this method, a universal active compensation scheme is proposed which can be used with operational amplifier voltage-controlled voltage sources, when looked upon as a general threeport active building block. It is shown that phase shifts contributed by imperfect operational amplifiers are virtually eliminated over an extended frequency range. Experimental resnits are presented.

Novel generalized differential integrator with controlled phase lead

A new active compensation method for the differential integrator is given. The proposed integrator has a phase lead which is controlled by a single resistor. The circuit realizes a novel phase lead inverting (noninverting) integrator by shorting one of the two input ports to ground. A differential integrator with a very small phase lag which includes the compensated Miller [1] and the compensated balanced time constant [2] integrators as special cases is also given.