Sony Corporation

Masaaki Ueki

Makoto Yamada

Gen Ichimura

Masayoshi Noguchi

Toshihiko Masuda

Yuichi Inomata

Nobuyuki Yasuda

A recording and/or reproducing apparatus for recording and/or reproducing digital audio signal on a recording medium such as a magnetic tape, which includes a recording and/or reproducing unit, an analog-to-digital convertor, a decimation filter, and noise shaper. The recording and/or reproducing unit records and/or reproduces signal on a recording medium at a speed double relative moving speed of a head and the recording medium at least. The analog-to-digital convertor converts input analog audio signal into digital signal with a sampling frequency which is above the audio frequency band, and sufficiently higher than the maximum frequency capable of recording by the recording and/or reproducing unit. The decimation filter reduces the sampling frequency of the digital signal output from the analog-to-digital convertor, and converts it into digital signal of m-bit (m&gt;n). The noise shaper converts the digital signal from the decimation filter from m-bit to n-bit, and then in requantizing, shapes noise so as to suppress within the audio frequency band, and supplies it to the recording and/or reproducing unit.

Audio signal transmitting apparatus and the method thereof

Method and apparatus for higher resolution audio signal transmitting

Analog audio signals supplied via an analog signal input terminal 1 are translated in parallel via a first .DELTA..SIGMA. modulator 2 and a second .DELTA..SIGMA. modulator 3 into digital audio data which are summed together by an additive node 4. The resulting sum data is attenuated in level by an attenuator 5 and translated by a decimation filter 6 into audio data having a predetermined number of bits and resulting audio data is outputted via an audio data output terminal 7. There is no necessity of providing a decimation filter for each .DELTA..SIGMA. modulator, so that the number of components may be reduced and the circuit may be simplified in construction to lower production costs. Besides, there is no necessity of re-quantizing the audio data at an output stage so that no quantization noise is produced to enable the S/N ratio to be improved by a theoretical value of 3 dB.

Analog to digital converter

A digital-to-analog converter utilizing a PWM system for converting input digital data to PWM signals and finally to an analog signal divides the sampling period of the input digital data into an even number of sampling periods and produces PWM signals with equal pulse widths corresponding to the input digital data each divided sampling period, whereby a simple structure is provided to reduce harmonic distortion and obtain a high quality analog signal.

Digital-to-analog converter using pulse-width modulation

A signal processing apparatus reduces the quantization noise by using so-called noise shaping circuits. The input signal may be audio or video signals. One of the noise shaping circuits is supplied with a signal which is the relative addition of the input signal and a dither while the other noise shaping circuit is supplied with a signal which is the relative subtraction of the input signal and the dither. The signal components of the outputs of the noise shaping circuits are effectively combined to cancel the dither components to produce an output with an improved S/N ratio. A plurality of such signal processing apparatus may be arranged in parallel, in which case different dithers are used in the respective signal processing apparatus and the outputs of the respective signal processing apparatus are combined to further improve the S/N ratio.

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Tokyo, Japan

Masaaki Ueki