Pioneer Corporation

Pioneer Electronic Corporation

Toru Ohashi

Yuji Yamamoto

Detection output from a detection circuitis converted to digital detection data Dand supplied to an AGC circuit AGCC and a noise clamping circuit NCC that are formed by digital circuits. In the AGC circuit AGCC, a digital low pass filtergenerates DC voltage data Dfrom the detection data D. A digital dividerperforms division of the DC voltage data Dby the reference detection level data Dindicating the detection data level. A digital multiplier multiplies the division results Dby the detection data Dto generate multiplication data Dthat is constant irrespective of a variation in the detection data D. In the noise clamping circuit NCC, a digital comparatorcompares the size of the preset voltage data Dand that of the multiplication data D. A selector circuitselectively outputs preset voltage data Dor multiplication data Dto generate signal wave data D.

Receiver for regenerating a signal wave via digital signal processing

Such a digital receiver comprises a digital band-pass filterfor performing digital filtering on digital data Dof the intermediate frequency, the digital data Dfrequency-converted by a frequency converter and undergone analog-to-digital conversion, at a first sampling rate equal to an exponentiation multiple of 2 of the intermediate frequency, and an interpolation filterfor performing digital filtering on digital data Doutput from the digital band-pass filterat a second sampling rate equal to an exponentiation multiple of 2 of the intermediate frequency and outputting the resulting data to a detection circuit

Receiver

A D/A converter includes a &#x394;&#x3a3;modulator applying Delta-Sigma modulation to a digital signal in order to generate a code sequence, and first and second post-filters as a first-order analog low-pass filter, respectively, which is connected in cascade to the subsequent stage of the modulator, in which low-pass filtering on the code sequence is executed so as to output an analog signal. The post-filter is set to have a cutoff frequency which falls in the frequency range from fca to fHa, where the fca is a cutoff frequecy of the post-filterand the fHa is a maximum frequency thereof. Since the respective attenuation characteristics of post-filters are synthesized, an overall attenuation characteristic between the both filters is able to have the characteristics of a desired second-order filter. The synthesized attenuation characteristic allows the D/A converter to simultaneously execute processing such as de-emphasis in the frequency range between the both cutoff frequency, and elimination of high-frequency noises over the frequency range of the cutoff frequency. As a result, the D/A converter with a small circuit scale can be provided.

Digital-to-analog converter

A digital filter for forming a feedback path including a delay unit, applying a filter operation to an input signal, giving a frequency characteristic having a predetermined time constant, and generating an output signal, is provided with: a selector having a multiplier for implementing time constants in at least two stages, and selecting the connection of the multiplier corresponding to a preset time constant to perform time constant switching; a timing generator for determining the timing when the time constant switching is performed by the selector; and a correction device for correcting the output of the delay unit to suppress variations in the output signal in the determined timing.

Digital filter

A level detector is provided for detecting the level of a signal demodulated by a detector of a stereophonic radio receiver. A separation controller is provided for producing a separation control signal dependent on the detected level. In response to the separation control signal, a stereo decoder controls the separation of left and right channels in such a manner that the separation is increased when the detected level of the demodulated signal is higher than a predetermined level.

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Saitama, Japan

Toru Ohashi