Digital signal receiver circuit
First Claim
1. A digital signal receiver circuit comprising:
- a preamplifier for generating a positive phase signal and the opposite phase signal from an input digital signal;
a first level sensing circuit for sensing and holding either the peak value or the bottom value of the positive phase output of said preamplifier;
a second level sensing circuit for sensing and holding the same level value as that of said first level sensing circuit from the peak value or bottom value of the opposite phase output of said preamplifier;
a first median output circuit for outputting the median between the positive phase output of said preamplifier and the output of said second level sensing circuit;
a second median output circuit for outputting the median between the opposite phase output of said preamplifier and the output of said first level sensing circuit; and
a first level comparison circuit for comparing the output of said first median output circuit with the output of said second median output circuit and outputting a signal voltage with a constant amplitude within a specific input voltage range, whereinsaid first and second level sensing circuits, first and second median output circuits, and said first level comparison circuit constitute an offset compensating section that performs the offset compensation of the DC level difference of the output of said preamplifier, andsaid first level comparison circuit constitutes an amplitude limit amplifier section that compares and amplifies the output of said offset compensating section.
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Accused Products
Abstract
An optical signal is converted by a light-receiving element into a photoelectric current. The photoelectric current is converted by a preamplifier into a positive phase voltage and the opposite phase voltage. The peaks of the positive phase output and opposite phase output are sensed and held by a first and second peak sensing circuits. The median between the output of the second peak sensing circuit and the positive phase output of the preamplifier is determined by a first median output circuit. The median between the output of the first peak sensing circuit and the opposite phase output of the preamplifier is determined by a second median output circuit. A level comparison circuit compares the outputs of the first and second median output circuits and produces a signal voltage with a constant amplitude within a specific input voltage range, thereby producing a reception signal. This helps alleviate duty fluctuations and the deterioration of the reception sensitivity resulting from the dark current of the light-receiving element or fluctuations in the output offset voltage of the preamplifier.
62 Citations
33 Claims
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1. A digital signal receiver circuit comprising:
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a preamplifier for generating a positive phase signal and the opposite phase signal from an input digital signal; a first level sensing circuit for sensing and holding either the peak value or the bottom value of the positive phase output of said preamplifier; a second level sensing circuit for sensing and holding the same level value as that of said first level sensing circuit from the peak value or bottom value of the opposite phase output of said preamplifier; a first median output circuit for outputting the median between the positive phase output of said preamplifier and the output of said second level sensing circuit; a second median output circuit for outputting the median between the opposite phase output of said preamplifier and the output of said first level sensing circuit; and a first level comparison circuit for comparing the output of said first median output circuit with the output of said second median output circuit and outputting a signal voltage with a constant amplitude within a specific input voltage range, wherein said first and second level sensing circuits, first and second median output circuits, and said first level comparison circuit constitute an offset compensating section that performs the offset compensation of the DC level difference of the output of said preamplifier, and said first level comparison circuit constitutes an amplitude limit amplifier section that compares and amplifies the output of said offset compensating section. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A digital signal receiver circuit comprising:
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a preamplifier for generating a positive phase signal and the opposite phase signal from an input digital signal; a first level sensing circuit for sensing and holding either the peak value or the bottom value of the positive phase output of said preamplifier; a second level sensing circuit for sensing and holding the same level value as that of said first level sensing circuit from the peak value or bottom value of the opposite phase output of said preamplifier; a first differential circuit that determines the difference between the positive phase output of said preamplifier and the output of said first level sensing circuit and outputs the difference; a second differential circuit that has the same gain as that of said first differential circuit and that determines the difference between the opposite phase output of said preamplifier and the output of said second level sensing circuit and outputs the difference; a first level comparison circuit that compares the output of said first differential circuit with the output of said second differential circuit and outputs a signal voltage with a constant amplitude within a specific input voltage amplitude range; a second level comparison circuit that has the gain equal to the product of the gain of said first or second differential circuit and the gain of said first level comparison circuit and that compares the output of said first level sensing circuit with the output of said second level sensing circuit and outputs a signal voltage with a constant amplitude within a specific input voltage amplitude range; and an adder circuit that adds the output of said first level comparison circuit to the output of said second level comparison circuit, wherein said first and second level sensing circuits, first and second differential circuits, and first level comparison circuit constitute an offset compensating section that performs the offset compensation of the DC level difference of the output of said preamplifier, said first level comparison circuit constitutes an amplitude limit amplifier section that compares and amplifies the output of said offset compensating section, and said second level comparison circuit and said adder circuit constitute a DC level reproducing section that compensates for fluctuations in the outputs of the first and second level sensing circuits. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A digital signal receiver circuit comprising:
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a preamplifier for generating a positive phase signal and the opposite phase signal from an input digital signal; a first level sensing circuit for sensing and holding either the peak value or the bottom value of the positive phase output of said preamplifier; a second level sensing circuit for sensing and holding the same level value as that of said first level sensing circuit from the peak value or bottom value of the opposite phase output of said preamplifier; a first differential circuit that determines the difference between the positive phase output and opposite phase output of said preamplifier and outputs the difference; a second differential circuit that has the same gain as that of said first differential circuit and that determines the difference between the outputs of said first and second level sensing circuits and outputs the difference; a first level comparison circuit that compares the output of said first differential circuit with the output of said second differential circuit and outputs a signal voltage with a constant amplitude within a specific input voltage amplitude range; a second level comparison circuit that has the gain equal to the product of the gain of said first or second differential circuit and the gain of said first level comparison circuit and that compares the output of said first level sensing circuit with the output of said second level sensing circuit and outputs a signal voltage with a constant amplitude within a specific input voltage amplitude range; and an adder circuit that adds the output of said first level comparison circuit to the output of said second level comparison circuit, wherein said first and second level sensing circuits, first and second differential circuits, and first level comparison circuit constitute an offset compensating section that performs the offset compensation of the DC level difference of the output of said preamplifier, said first level comparison circuit constitutes an amplitude limit amplifier section that compares and amplifies the output of said offset compensating section, and said second level comparison circuit and said adder circuit constitute a DC level reproducing section that compensates for fluctuations in the outputs of the first and second level sensing circuits. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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28. A digital signal receiver circuit comprising:
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a preamplifier for generating a positive phase signal and the opposite phase signal from an input digital signal; a first level sensing circuit for sensing and holding either the peak value or the bottom value of the positive phase output of said preamplifier; a second level sensing circuit for sensing and holding the same level value as that of said first level sensing circuit from the peak value or bottom value of the opposite phase output of said preamplifier; a first differential circuit that determines the difference between the positive phase output and opposite phase output of said preamplifier and outputs at least the positive phase signal; a second differential circuit that has the same gain as that of said first differential circuit and that determines the difference between the output of said first level sensing circuits and the output of said second level sensing circuit and outputs the positive phase signal and opposite phase signal; a first level comparison circuit that compares the positive phase output of said first differential circuit with the positive phase output of said second differential circuit and outputs a signal voltage with a constant amplitude within a specific input voltage amplitude range; a second level comparison circuit that has the same gain as that of said first level comparison circuit and that compares the positive phase output and opposite phase output of said second differential circuit and outputs a signal voltage with a constant amplitude within a specific input voltage amplitude range; and an adder circuit that adds the output of said first level comparison circuit to the output of said second level comparison circuit, wherein said first and second level sensing circuits and first and second differential circuits constitute an identification level sensing section that senses the identification level of the output of said first differential circuit, said first level comparison circuit constitutes an amplitude limit amplifier section that compares and amplifies the output of said identification level sensing section, and said second level comparison circuit and said adder circuit constitutes a DC level reproducing section that compensates for fluctuations in the outputs of the first and second level sensing circuits. - View Dependent Claims (29, 30, 31, 32, 33)
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Specification