Sumihisa Hashiguchi

Two-dimensional LMS adaptive filters

A novel two-dimensional least mean square (2-D LMS) algorithm is proposed. This algorithm can converge along both the horizontal and vertical directions of a 2-D plane. In order to compare this algorithm to another 2-D LMS algorithm, both are realized in the form of a 2-D adaptive line enhancer (2-D ALE), and they are applied for to enhancement of images contaminated with noise. The 2-D ALE based on the proposed algorithm does not cause any degradations due to anisotropic processing. >

Noise and transport characterisation of tantalum capacitors

Abstract A low frequency noise and charge carrier transport mechanisms were investigated on tantalum capacitors made by various producers. The model of Ta–Ta2O5–MnO2 MIS structure was used to give physical interpretation of I–V characteristics in normal and reverse modes. The noise in time and frequency domain was examined and noise sources were identified. We evaluated correlation between leakage current and noise spectral density and discussed corresponding quality and reliability indicators.

A digital still camera

A small-sized digital still camera was successfully manufactured, incorporating the pixel-adaptive DPCM (differential pulse code modulation) scheme for data compression. The picture data were processed in the red-green-blue (RGB) form arranged in the inline sequence. The charge coupled device (CCD) imager with vertical stripe color filters was driven so to generate red, green, and blue signals that were adequate for application of the adaptive DPCM procedure. >

A new 2-D LMS adaptive algorithm

A novel adaptive LMS (least mean square) algorithm is presented in which the algorithm can update the filter coefficients along both the horizontal and the vertical directions on a 2-D plane. Both the conventional algorithm and the new 2-D LMS algorithm are applied to the identification of unknown 2-D systems with stationary or nonstationary characteristics. The learning curves and the mean square errors show that the new 2-D LMS adaptive algorithm is particularly suitable for processing 2-D nonstationary signals. However, it converges slowly for stationary inputs.<<ETX>>

Measurement of the Temperature Fluctuation in a Resistor Generating 1/f Fluctuation

A new method is devised to measure the temperature fluctuation in a current-carrying resistor. The spectrum of the temperature fluctuation is determined from the values of the resistance fluctuation, the variance fluctuation, and their product. It is found to be proportional to f1.1 and the temperature fluctuation amounts to 0.13 K2 in the frequency range of 104–102 Hz. This agress well with the calculated value of the equilibrium temperature fluctuation in the effective volume generating 1/f noise.

RTS in submicron MOSFETS and quantum dots

In the present paper, emphasis is laid on those RTS showing a capture process, which deviates from the standard Shockley-Read-Hall kinetics. A modified two-step approach is proposed. In this case the charge carrier quantum transitions represent a primary process X(t), which involves two or three quantum states. The measurable quantity is the current modulation, which has discrete states, too. The current modulation is then represented by a secondary process Y(t). The proposed model can explain some of the complex switching phenomena being measured in nanoscale devices. The quadratic dependence of the capture rate on the current and the noise spectral density dependence on the current and temperature are analysed. It is shown that the occupation time probability density for emission is given by a superposition of two exponential dependencies, whereas the capture time constant distribution is purely exponential.

Electron Cyclotron Resonance Plasma Etching of n-SiC and Evaluation of Ni/n-SiC Contacts by Current Noise Measurements

The Si surface of n-SiC is etched by an Ar electron cyclotron resonance plasma in order to smooth the as-received substrates. Low-frequency current noise characteristics of Ohmic contacts of the wide-band-gap semiconductor n-SiC are investigated. Ohmic contacts with a diameter of 200 µm have a minimum Ohmic contact resistance of the order of 10-4 Ωcm2 at an alloying temperature of 1000°C for 30 min. These low resistance Ohmic contacts show typical 1/f current noise characteristics that increase with the square of the sample current I2. A sample with a higher contact resistance exhibits, however, current noise power increase with increasing sample current I. The relevant total electron number between the electrodes of the bulk substrate is estimated from the resistance and by finite element method simulation, from which the Hooge parameter αH is estimated to be approximately 40.

Generation of 1/f spectrum by relaxation process in thin film resistors

Relaxation processes with various time constants generate a 1/f spectrum when they are driven by a single random time series. Such simple processes may be the origin of the noise generated in some kinds of thin film resistors.

Research and development of WEarable walKing mate system

A wearable travel aid to guide visually impaired without special infrastructures has been developed. We call this system WEarable walKing mate system (WEK). The WEK has three functions that 1) Create courses data, 2) Guide a visually impaired to the destinations, and 3) Warm the dangerous places. This paper described the estimation method of travel distance using Optical Flow in the WEK, which is effective for various ways of walking. The experimental results in an indoor environment show the each error of estimated travel distance is less than at previous method to three kinds of how, a shuffle, a natural walking, and a march. There are shown that the WEK is efficient for guiding the visually impaired to the destinations.

Noise and Charge Storage in Nb2O5 Thin Films

A low frequency noise and DC leakage current measurements have been performed on the MIS structure NbO − Nb2O5 − MnO2. The mechanism of current flow and current noise sources were determined from these measurements. The insulating layer thickness is 50 to 150 nm, relative permittivity about 38. The charge is accumulated not only on NbO and MnO2 electrodes, but also in the Nb2O5 insulating layer. The charge carrier transport is determined by the Poole‐Frenkel mechanism and tunnelling in the normal mode (for NbO electrode positive). In this case g‐r noise is dominant for Poole‐Frenkel mechanism and 1/f noise is dominant for tunnelling.