Detector Transfer Function Research Articles

Computationally intelligent description of a photoacoustic detector

In this article, a method for determination of photoacoustic detector transfer function as an accurate representation of microphone frequency response is presented. The method is based on supervised machine learning techniques, classification and regression, performed by two artificial neural networks. The transfer function is obtained by determining the microphone type and characteristic parameters closely related to its filtering properties. This knowledge is crucial within the signal correction procedure. The method is carefully designed in order to maintain requirements of photoacoustic experiment accuracy, reliability and real-time performance. The networks training is performed using large base of theoretical signals simulating frequency response of three types of commercial electret microphones frequently used in photoacoustic measurements extended with possible flat response of the so-called ideal microphone. The method test is performed with simulated and experimental signals assuming the usage of open-cell photoacoustic set-up. Experimental testing leads to the microphone transfer function determination used to correct the experimental signals, targeting the “true” undistorted photoacoustic response which can be further used in material characterization process.

The periodic pulse photothermal radiometry technique within the front face configuration

The front face photothermal radiometry technique has been improved in order to estimate the thermal conductivity of thin films with better accuracy compared to existing techniques. The experimental procedure is based on the front face response to a nanoseconds laser pulse repeated periodically at high frequency, i. e., a Dirac comb waveform. Averaging the thermal response by considering thousands successive pulses allows improving largely the signal noise ratio. The unknown thermal properties and related experimental parameters are identified by minimizing the gap between the measured signal and the theoretical response that accounts with the pulse waveform, the repetition frequency and the detector transfer function. Minimization is first achieved by implementing first a simplex technique that gives an initial set of values to start the Metropolis–Hastings algorithm in a second step. Application of the proposed methodology is done considering amorphous GeTe film deposited on a Si wafer. It is shown that this experimental method as well as the implementation of the Bayes minimization technique allows to identify the thin film intrinsic thermal conductivity with high accuracy considering some uncertainty on the other parameters assumed to be known.

Prediction of spatial resolutions of future IR cameras at ITER

Here are presented the predictions of the spatial resolutions of one of the future IR camera that will survey the divertor of the Tokamak ITER. The objective is to associate, in Fourier space, the optical transfer function and the detector transfer function to calculate the total transfer function (TTF) of the virtual IR camera. The modulation transfer function (modulus of TTF) quantifies the ‘imaging’ performances of the virtual camera. Its ‘measuring’ performances are estimated by the simulation of the slit response function experiment. Finally, some results of sharp temperature profile measurements in realistic plasma situations are presented.

Cleaning-up dirty isotachopherograms in time and frequency domain

In chromatography and electrophoresis S/N is increased by time or frequency domain filtering, multiple injections or sample stacking (in case of CZE). Bottom line is noise reduction without peak distortion. Isotachophoresis (ITP) using conductivity detection is also relevant because of its entirely different information content and the importance in CZE stacking. Several time- and frequency domain filters (Fourier & Walsh transform) were compared. Results were:•Time domain filters can be equally applied to either integral or differential signal;•Fourier and Walsh transforms are likewise suitable, whereas Walsh better preserves sharp boundaries;•Disturbance by detector transfer function can only be partly un-done with de-convolution; conditions are critical.

A Miniature Pockels Cell with Novel Electrode Geometry

This paper discusses important elements of the Pockels sensing cell design. A novel electrode geometry is analyzed in order to obtain maximum sensitivity response from Pockels crystals (Bi12GeO20). This neither transversal nor truly longitudinal geometry, results in electrical field distribution along the sensing beam path that provides high modulation depth. Demonstrated performance level is in agreement with theoretical studies. Delta-sigma polarization detection method allows high linearity of the detector transfer function and measurement independent on laser intensity variations. Channel gain equalization process necessary for accurate delta-sigma normalization is provided by a walk off prism.

Simulated Response of the MARIO SCHENBERG Detector to Gravitational Wave Signals with Noise

The Mario Schenberg gravitational wave detector has been constructed at its site in the Physics Institute of the University of Sao Paulo as programmed by the Brazilian Graviton Project under full financial support from FAPESP (the Sao Paulo State Foundation for Research Support). We are ready to do a first test run of the spherical antenna at 4.2 K with three parametric transducers and an initial target sensitivity of h ∼ 10−21 Hz−½ in a 60 Hz bandwidth around 3.2 kHz.We have built a computer code for determining the source direction and the wave polarization (solution of the inverse problem) in real time acquisition for strong signal-to-noise ratio cases. The digital filter used is a simple bandpass filter.The ‘‘data’’ used for testing our code was simulated, it had both the source signal and detector noise. The detector noise includes the antenna thermal, back action, phase noise, series noise and thermal from transducer coupled masses. The simulated noise takes into account all these noise and the antenna-transducers coupling. The detector transfer function was calculated for a spherical antenna with six two-mode parametric transducers.Finally, we were able to check at what distance Schenberg would detected some known sources. Here we present the results of these simulations.

Reconfigurable carrier‐recovery loop

AbstractThis paper proposes a carrier‐recovery loop using a reconfigurable phase shaper. It is based on the five‐port technique, which has the advantage of using mixed circuits to calculate complex power ratios. Different modulation standards can be canceled, since the phase detector's transfer function can be dynamically changed. Furthermore, the loop filter is also reconfigurable, thus allowing for fast‐frequency acquisition and low‐noise bandwidth. Measurement results are presented in the 2‐GHz band with a data rate of 1 Mb/s. The regenerated carrier's phase noise and power spectral density are provided, as well as the constellation diagram of the demodulated signal. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 406–408, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20484

Critical dimension control of high resolution metal structures by backscattered electrons

In this article a commercial e-beam lithography machine (Leica Cambridge EBMF 10 cs/120) is used in metrological mode for critical dimension control of metal features with size down to 100 nm. The experimental backscattered electrons signal, collected by a channel plate detector, is described by an analytical function which is the convolution of probe beam function, detector transfer function, and specimen absorption transfer function. The further data processing by means of a developed software algorithm, allowed the determination of the significant structure parameters as linewidth and sidewall angle. Metal test structures, as isolated lines and grooves with size down to 100 nm, fabricated on silicon wafers, are successfully inspected and measured by this method. The comparison between computed dimensions and scanning electron microscopy measurements shows a good agreement (within 5%) for structures of different dimensions, varying their aspect ratio and the sidewall angle at their edges. The effect of beam diameter (BD) value on the measurement was also investigated and accurate measurements have been obtained for BD less than the structure dimension. Finally, a repeatability test performed on a sub-200 nm gold feature showed a precision of 6 nm (3σS value) on a sample of one thousand measurements.

A New Phase Locked Loop with Sin-O-Linear Detector

The performance of a phase-locked loop (PLL) having phase detector transfer function as a combination of sinusoidal and sawtooth types has been described in this paper. The improved noise handling capacities and larger acquisition range of the PLL compared to those of conventional ones have been established analytically.

Dynamic Compensation of Rhodium Self Powered Neutron Detectors

A mathematical model of a rhodium self-powered neutron detector has been developed to investigate the detector transfer function and to apply this transfer function as compensation for the inherent time delay in the rhodium-neutron interaction. The various reactions that comprise the detector signal have been evaluated experimentally and the resultant transfer function compensation has been tested in the field against a prompt responding ion chamber during a reactor trip.