DC Voltage control circuits

A DC voltage control circuit comprising:

• DC superposing means for superposing a control signal on an input signal;
• discriminating means for discriminating an output of said superposing means with a plurality of signal discriminating levels including a center discriminating level and with a plurality of error discriminating levels and for providing a plurality of digital signals, said signal discriminating levels dividing said input signal into a plurality of signal regions, said error discriminating levels dividing said signal regions into two, respectively;
• and
• control signal generator means for generating said control signal in response to some of said digital signals, which comprise error information obtained from said error regions except at least the error regions on positive or negative side adjoining said center discriminating level.

A DC voltage control circuit comprising:

• DC superposing means for superposing a control signal on an input signal;
• discriminating means for discriminating an output of said superposing means with a plurality of signal discriminating levels including a center discriminating level and with a plurality of error discriminating levels and for providing a plurality of digital signals, said signal discriminating levels dividing said input signal into a plurality of signal regions, said error discriminating levels dividing said signal regions into two, respectively;
• and
• control signal generator means for generating said control signal in response to some of said digital signals, which comprise error information selectively obtained from said error regions except at least the error regions on positive or negative side adjoining said center discriminating level, or from all said error regions.

A demodulation apparatus comprising in combination a demodulation circuit for demodulating a modulated carrier wave and a DC voltage control circuit for compensating for DC component variations caused when discriminating and regenerating the demodulated signal:

• said DC voltage control circuit including a plurality of DC superposing means each superposing a control signal upon an input demodulated signal;
• a plurality of discriminating means each connected to the respective DC superposing means, for discriminating an output of said superposing means with a plurality of signal discriminating levels including a center discriminating level and with a plurality of error discriminating levels and for providing a plurality of digital signals, said signal discriminating levels dividing said input signal into a plurality of signal regions, said error discriminating levels dividing said signal regions into two, respectively;
• and
• a plurality of control signal generator means for generating said control signal in response to some of said digital signals, which comprise error information obtained from said error regions except at least the error regions on positive or negative side adjoining said center discriminating level;
• said demodulation circuit including a carrier synchronizing circuit responsive to the outputs of said DC voltage control circuit for providing a reference carrier wave, and a demodulator for detecting the modulated carrier wave with said reference carrier wave and providing said demodulated signal.