Matsushita Electric Industrial Co., Ltd.

Matsushita Electrical Industrial Co., Ltd.

Tetsuhiko Kaneaki

Yasunori Tani

Kinji Kawamoto

Masataka Nikaido

Kazuhiro Murase

Kozo Nuriya

Akira Sobajima

Tatsuya Adachi

Mikio Oda

Tsuyoshi Takayama

Masao Tsukamoto

Yoshiyuki Takagi

Yoshihiko Fukumoto

Junnosuke Shigeta

Sakurako Matsuda

Hideaki Hatanaka

Kazuhiko Murase

D/A conversion apparatus and A/D conversion apparatus

An offset reducer includes an adder for adding an input signal and an offset cancel signal to reduce an offset component of the input signal. A converter serves to measure a difference between a sum of past periods during which an output signal of the adder was positive and a sum of past periods during which the output signal of the adder was negative. The converter outputs an offset detection signal of a given value which depends on a sign of the measured difference when an absolute value of the measured difference exceeds a given difference. The converter initializes the measured difference to a given initial difference when the offset detection signal is outputted. An integrator serves to accumulate the offset detection signal outputted from the converter. The integrator generates the offset cancel signal in accordance with a result of the accumulating the offset detection signal. The output signal of the adder constitutes an offset-free signal corresponding to the input signal.

Digital filter for removing DC components

In a digital signal noise shaping requantization circuit formed of a first delta-sigma quantizer (main loop) for executing noise shaping of an input digital signal and a second delta-sigma quantizer (sub-loop) which receives as input signal the quantization error of a local quantizer in the first delta-sigma quantizer, and whose output signal is differentiated and added to the output signal from the first delta-sigma quantizer, the second delta-sigma quantizer includes a feedback circuit for operating on a quantization error of a local quantizer therein, with a predetermined transfer function. The output signal from the feedback circuit, in addition to being fed back to the input of the second delta-sigma quantizer, is also applied to control the operation of the first delta-sigma quantizer such as to modify the value of quantization error of the local quantizer of the first delta-sigma quantizer, for thereby ensuring stable and effective operation of the second delta-sigma quantizer even when the input digital signal attains a high amplitude.

Digital signal requantizing circuit using multistage noise shaping

A noise shaping quantization D/A converter in which an input digital signal is supplied to a single-integration sigma delta modulation circuit having quantization levels which include zero level, with a quantization error signal from the single-integration circuit being supplied to a double-integration noise shaping quantization circuit having quantization levels which also include zero level, and an output signal from the double-integration circuit being differentiated and summed with the single-integration circuit output to obtain a bit-compressed digital signal for D/A conversion. Offset of the analog output signal during a zero hold status of the input digital signal is eliminated, and increased efficiency of supply voltage utilization is attained, together with increased S/N ratio.

Multi-stage noise shaping over-sampling D/A converter

A first analog input signal is converted into a plurality of second analog signals having different levels respectively. The second analog signals are inputted into respective analog-to-digital converters. Values of output signals from the respective converters are adjusted in accordance with the values of the output signals from the respective converters to convert the output signals from the respective converters into respective adjusted signals. One of the adjusted signals is selected in accordance with the values of the output signals from the respective converters. The selected signal is produced as a system output signal.

Analog-to-digital converting system

An electronic musical instrument includes a first waveform memory for storing a waveform corresponding to an attack portion of a musical tone and one period of a steady waveform produced after the attack, a second waveform memory for storing one period of a waveform different from the contents of the first waveform memory, a waveform reader which reads out the first and second waveform from the first and second waveform memory, respectively, and an envelope generator which generates two separate envelope signals. The first waveform including the attack portion of the musical tone and the periodic second waveform are multiplied by the separate envelope signals, respectively, and then the products of the multiplication are added together. The sum of the products is provided as an output. Thus, the electronic musical instrument is capable of precisely simulating the attack portions of musical tones of a natural musical instrument and generating musical tone signals having a steady part vividly simulating the musical tones of the natural musical instrument.

Electronic musical instrument for generating a natural musical tone

A wave generating method and a wave generating apparatus using the method are arranged such that plurality of wave samples, each being generated successively, are respectively weighted by, for example, being multiplied by a plurality of wave functions generated corresponding to the plurality of wave samples. The plurality of weighted wave samples are summed to obtain a desired wave. The kind of each of the plurality of wave samples generated successively is changed at each time when the value of corresponding one of the plurality of wave functions becomes zero. Therefore, the apparatus includes wave generators for generating the wave samples successively, wave function generators for generating the wave functions successively, multipliers for multiplying the wave samples by the wave functions respectively, an adder for adding all of the outputs of the multipliers to generate the desired wave, and a wave changing circuit for changing the kind of each of the wave samples when the corresponding one of the wave functions becomes zero.

Wave generating method and apparatus using same

A multiple wave generator for an electronic musical instrument which has a wave data memory storing plural data samples of a wave shape, a wave address register storing wave address data partially designating sampled data in the wave data memory, a difference address register storing difference address data which specifies incremental address amount, a wave address calculator adding the wave address data to the difference address data and writing into the wave address register, the summed address data being separated into wave memory address data and partial address data, and a wave calculator. The wave memory address data, which are part of the wave address data, are applied to the wave data memory for reading out one data sample, and the one data sample and the partial address data are applied to the wave calculator for calculating interpolated wave sample data corresponding to the wave memory address and the partial address.

Multiple wave generator

An electronic musical instrument has a generator assigner for supplying note data and octave data by key stroke entry, a top octave synthesizer for generating 12 of the highest pitch signals for each note, a circuit for selecting one highest pitch signal from the 12 highest pitch signals according to note data, a binary counter for dividing one highest pitch signal to produce several pitch signals, and circuits for selecting one pitch signal out of several pitch signals obtained by the binary counter. The circuits are further controlled by both octave data and note data to generate octave series tone signals and non-octave series tone signals such as quint series tone signals.

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Ashiya, Japan

Tetsuhiko Kaneaki