An adaptive technique for determining a reduced model for a system

A reduced or sparse system model is discussed that will contain only the most significant components, as opposed to a complete finite impulse response (FIR) model which may not be very accurate with the requirement of only a few components. The technique presented uses an adaptive delay filter to provide the sparse model and compares it to the model obtained with the standard adaptive filter     

An acoustic technique for studying thyristor turn-on action and di/dt capability

Mechanical shock waves have been detected emanating from the initial turn-on region in thyristors. This phenomenon has enabled the position of the ignition point to be determined and has allowed nondestructive examination of the effect of some parameters on di/dt capability.     

Utilisation of the MV spectrum for diagnosis and estimation ofharmonic fields

The authors consider the identification of a single channel multidimensional harmonic signal field contained in an unknown and possibly nonstationary noise field. A technique is presented using the convergence-based point spectra developed by Frazho and Sherman (1990, 1991). This technique has the advantage of discerning between point and narrowband noise spectra based on the monotonic convergence properties of a sequence of minimum variance (MV) spectra. Two examples are presented to demonstrate the properties and utility of the approach, also a comparison to the multidimensional discrete Fourier transform and autoregressive modelling techniques     

An experimental study of a sea clutter model

A model for the radar cross section (RCS) of the sea has been developed in parallel efforts by scientists in both the United States and the Soviet Union, which is based upon the concept of a composite surface, i.e., one in which a slightly rough surface in the sense of Rice is superimposed on a larger swell structure. For angles off the normal, the model predicts the variation of the RCS with frequency, polarization, and incident angle of the illumination and further predicts an upper bound (saturation value) of the RCS with increasing roughness. The model has been collated with data collected by the Naval Research Laboratory four-frequency radar system in sea states ranging from 0 to 7. The results of the comparison have shown that the upper bound for the RCS exists and is closely approached in windspeeds in excess of 5 m/s. In addition, the data have confirmed the variation of RCS with frequency (UHF to X-band), grazing angle, and with polarization (H, V), provided that the "tilting" of the scattering surface by swell is taken into account in the region of shallow grazing angles.     

Charge-extraction technique for studying the surface states in MOSdevices

A method called the charge-extraction technique is proposed for studying the surface states in MOS devices. This new technique utilizes the substrate current arising from the non-steady-state emission of carries from the surface states instead of that arising from their steady-state recombination, as utilized in the charge-pumping method. This is achieved by confining the amplitude of the gate-voltage signal to such a magnitude that the surface region of the device does not cross the depletion limits. A new theoretical model is developed for the present case which predicts the occurrence of a maximum value of the substrate current at a certain optimum frequency of the applied gate-voltage signal. Experimental measurements have been found quite in conformity with the theoretical model. It is found that the maximum substrate current and the corresponding optimum frequency, obtained in this way, can serve as more handy and precise parameters for the determination of the surface states     

An experimental technique for the investigation of the formation of picosecond pulses in a mode-locked Nd-glass laser

A general mode-locking andQ-switching technique which is specially suitable for the investigation of the influence of the non-linear transmission characteristic on the formation of mode-locked pulses is described. In addition, some preliminary results are reported.     

Liquid-crystal technique for observing integrated-circuit operation

A nondestructive technique has been developed that enables both the electric fields and temperature distributions at the surface of an operating integrated circuit to be viewed with conventional optical microscopes. Packaged chips or unscribed wafers are coated with a nematic liquid-crystal layer and operated in their normal fashion. Practical preparation and observation procedures have been developed.     

An affordable experimental technique for SRAM write margin characterization for nanometer CMOS technologies

Increased process variability and reliability issues present a major challenge for future SRAM trends. Non-intrusive and accurate SRAM stability measurement is crucial for estimating yield in large SRAM arrays. Conventional SRAM variability metrics require including test structures that cannot be used to investigate cell bit fails in functional SRAM arrays. This work proposes the Word Line Voltage Margin (WLVM), defined as the maximum allowed word-line voltage drop during write operations, as a metric for the experimental characterization of write stability of SRAM cells. Their experimental measurement can be attained with minimal design modifications, while achieving good correlation with existing writability metrics. To demonstrate its feasibility, the distribution of WLVM values has been measured in an SRAM prototype implemented in 65 nm CMOS technology. The dependence of the metric with the width of the transistors has been also analysed, demonstrating their utility in post-process write stability characterization.     

Double mandrel: a modified technique for studying static fatigue on optical fibres

Static fatigue failure data for optical fibres are obtained with a new measuring method. A fibre is wound around two rods of different diameter and each winding is fixed separately near the thicker one. Times of failure of the separate windings are measured. This new method to obtain static fatigue data will be demonstrated on mandrels stored in different environments.     

An experimental technique for in vivo permittivity measurement ofmaterials at microwave frequencies

A procedure for making in vivo dielectric measurements with an open-ended coaxial line probe is discussed. The theory behind the technique is discussed, along with a correction method to account for the system imperfections. Experimental results are compared with data for the lumped parameter model approach and a mathematically sound integral equation method available in the literature. The results show good agreement, with the exception of the lumped parameter technique, which deviates at higher frequencies. The limitations of this technique are considered     

An experimental technique used to measure the unloaded Q ofmicrostrip antennas

This paper presents a scattering method for measuring the unloaded Q of a prototype microstrip (patch) antenna structure without the need to implement connecting circuitry     

An improved technique and experimental results for the extractionof electron and hole mobilities in MOS accumulation layers

For the first time, experimental results are presented for electron and hole mobilities in the electron and hole accumulation layers of a MOSFET for a wide range of doping concentrations. Also presented is an improved methodology that has been developed in order to enable more accurate extraction of the accumulation layer mobility. The measured accumulation layer mobility for both electrons and holes is observed to follow a universal behavior at high transverse electric fields, similar to that observed for minority carriers in MOS inversion layers. At low to moderate transverse fields, the effective carrier mobility values are greater than the bulk mobility values for the highest doping levels. This is due to screening by accumulated carriers of the ionized impurity scattering by accumulated carriers, which dominates at higher doping concentrations. For lower doping levels, surface phonon scattering is dominant at low to moderate transverse fields so that the carrier mobility is below the bulk mobility value     

Gas storage technique for the repetitively pulsed operation of a continuously excited laser

This paper reports a technique by which repetitively pulsed outputs may be obtained from some continuously excited gas lasers by supplying the resonator with pulses of excited gas. The technique is applied to a CO2laser in which 14 kW, 1 ms (FWHM) pulses are produced at a repetition frequency of 200 Hz.     

An optimising technique for a K-out-of-N system

Of the class of redundant configuration systems the K-out-of-N system is studied. The system is considered successful if at least K subsystems out of the N are successful. A technique based on Bellman's¹ “Principle of Optimality” is developed to optimise the system reliability subject to cost constraints.     

An experimental technique for the study of non-avalanche charge injection or trapping in MIS structures

In the study of charge injection in the insulator-silicon system, variation of the electric field in the insulator, caused by charge trapping during a measurement, makes the interpretation and analysis of experimental data difficult.A measuring system and test device structure are described in which it is possible to monitor any change of the device threshold voltage and to adjust the applied gate voltage so as to maintain a constant electric field at the insulator-silicon interface.Experimental results will be presented which show the advantages stemming from this mode of operation.     

A combined technique for studying the multicomponent spectra of photoreflection from semiconductors

A new technique for studying the multicomponent photoreflection spectra in semiconductors involves spectra measurements at different laser fluences and wavelengths in combination with spectrum phase analysis. To demonstrate the possibilities offered by the technique, the multicomponent photoreflection spectrum of the passivated homoepitaxial Si₃N₄/n-GaAs/n ⁺-GaAs wafer is analyzed.     

A scale model for studying ground penetrating radars

A scale model developed for experimentally studying ground penetrating radars is described. The model is one-third full size and is used with transient signals that have significant frequency content within the range 150 MHz to 1.5 GHz. A unique feature is that the soil in the model is represented by an emulsion, which is mixture of mineral oil, saline solution, and a stabilizing agent. This emulsion is a scale model for red clay soil; it matches the electrical parameters of the clay, including the dispersion in the conductivity, over a ten-to-one frequency range. Typical results measured with the model are discussed. These include the measurement of the electric field transmitted by the radar into the soil and the measurement of radar signatures for pipes of various composition buried in the ground     

An empirical model and an inversion technique for radar scatteringfrom bare soil surfaces

Polarimetric radar measurements were conducted for bare soil surfaces under a variety of roughness and moisture conditions at L -, C-, and X-band frequencies at incidence angles ranging from 10° to 70°. Using a laser profiler and dielectric probes, a complete and accurate set of ground truth data was collected for each surface condition, from which accurate measurements were made of the rms height, correlation length, and dielectric constant. Based on knowledge of the scattering behavior in limiting cases and the experimental observations, an empirical model was developed for σ°_hh, σ°_vv, and σ° _hv in terms of ks (where k=2π/λ is the wave number and s is the rms height) and the relative dielectric constant of the soil surface. The model, which was found to yield very good agreement with the backscattering measurements of the present study as well as with measurements reported in other investigations, was used to develop an inversion technique for predicting the rms height of the surface and its moisture content from multipolarized radar observations     

An improved approach and experimental results of a low-frequency noise measurement technique used for reliability estimation of diode lasers

In this paper, we give the experimental results of low-frequency noise measurement and reliability forecasting after we have studied the low-frequency noise and electric ageing of 23 GaAs/GaAlAs proton-bombarded heterostructure LDs and 21 V-groove InP/InGaAsP lasers. We discuss the measuring circuits, measuring parameters, and suggest an improvement.