Shojiro Yoneda

Switched-capacitor DFT and IDFT Circuit

The switched-capacitor realization of the discrete Fourier transform (DFT) is treated in this paper as well as the inverse discrete Fourier transform (1DFT). The output of the DFT has a sinusoidal waveform including the amplitude and phase information of the required spectra. These spectra are given simultaneously and almost in real time. The output of the 1DFT is given merely by adding DFT outputs. Furthermore, the circuit configuration of this system-from input to DFT, from DFT to 1DFT, and from 1DFT to output-is a very simple configuration constructed by a non-recursive filter circuit.

Switched-capacitor non-recursive lowpass filter

A new switched-capacitor realization of a non-recursive filter based on the digital filter theorem is proposed. A switched-capacitor realization of the delay circuit is described first. A switched-capacitor coefficient multiplier and adder are based on the integral feedback capacitance circuit. This circuit has the feature that the voltage across the integral feedback capacitance is used for the output voltage, whereas, in an ordinary circuit, the output voltage is used at the output terminal of an operational amplifier. Agreement between experimental and theoretical values is confirmed.

Novel tracking amplifier composed of switch and comparator

Abstract A new amplifier (called a tracking amplifier) is proposed which need not contain any amplifying elements such as transistors and valves. It is composed of a switch, a comparator, a voltage divider and a low-pass filter. On a principle similar to delta modulation, the input signal is compared with a part of the output signal obtained through feedback. The source voltage is switched with the comparator output, and smoothed, so the amplifier output varies in proportion to the input signal.

A neural network with a mechanism for detecting and zooming

This paper proposes a pre-processing model for character recognition by neural networks. In character recognition, it is important to extract a character from a given input pattern. If this input character is different from the training patterns in position and/or scale, the recognition rate will decrease. Hence, where the character size is far larger or smaller than those in the training patterns, it is necessary to extract the character. The proposed model uses a large input layer from which it can extract a character. This model will be useful in the realization of optical character reader system by neural networks.

Switched-capacitor realization of a Walsh transform circuit and its application to sequency filtering

A novel switched-capacitor discrete Walsh transform circuit is proposed. The Walsh hardware transformation is improved in simplicity by using the proposed circuit, and this circuit has a speed advantage because of analog processing. Furthermore, a switched-capacitor inverse Walsh transform circuit is constructed. A switched-capacitor sequence filter is also proposed which combines the Walsh transform circuit and its inverse.<<ETX>>

A consideration of the problems in switched-capacitor realization of non-recursive and recursive filters

ABSTRACT The realizations of switched-capacitor filter based on the digital filter and their problems are indicated. There are two types of filters, non-recursive and recursive. For the switched-capacitor realization of non-recursive, an improvement is given, and for that of recursive, a limitation under the circuit configuration using discrete parts is shown

Application of a switched-capacitor circuit to converting a two-wire to a four-wire hybrid function

ABSTRACT A new switched-capacitor circuit using an integral feedback capacitor is proposed. A capacitor in a CR integrator which uses an operational amplifier is regarded as an information transmission element. By switching this capacitor from the input side to the output side periodically, a sampled-data transmission circuit is produced which has better frequency response than that of an ordinary integrator. The technique is shown applied to a solid-state two-wire to four-wire hybrid function in telephone communication.

Sampled-data charge processor

ABSTRACT A general-purpose analogue signal processor is presented in which all operations are performed in a charge domain. The processor can be customized to each application according to an instruction program. The processor is composed of amplifiers, analogue switches, capacitors and a memory. Charge-domain processing techniques and a calibration technique are used to reduce the requirement for a capacitor precision-ratio. An application to bandpass filtering is demonstrated.

A Novel Method of Echo Suppression Using a Bilateral Optoisolator Circuit

In the telephone network, an echo is generated at the hybrid junction that connects four- to two-wire lines. A conventional echo suppressor or canceller is designed on the assumption that the echo is actually induced. On the contrary, in this novel method using a bilateral optoisolator circuit, the echo is suppressed at its origin. This bilateral optoisolator circuit has not only the property of bilateral transmission, but also the same property of suppression impedance fluctuation as is characteristic of a buffer amplifier. Experimental results show that the degradation of echo return loss can be kept within a few decibels even under the severe condition that the line impedance changes from zero to infinity.

A pitch synchronous switched capacitor discrete Fourier transform circuit

A novel pitch-synchronous switched capacitor (SC) discrete Fourier transform (DFT) circuit suitable for high-speed spectral analysis is proposed. This circuit can analyze a harmonic signal synchronously with the pitch period of the signal, and it takes less than 0.2 ms to analyze 32 spectral components. Moreover, it is possible that all the proposed circuits can be integrated into one LSI package since they are constructed using the SC technique.<<ETX>>