Receiving circuit and electronic apparatus for optical communication

• US 7,460,792 B2
• Filed: 07/07/2005
• Issued: 12/02/2008
• Est. Priority Date: 07/09/2004
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Yokogawa, Naruichi, Nishino, Takeshi
• Primary Examiner(s): Phan, Hanh
• Application Number:
  US11/175,340
• Publication Number:
  US 20060008280A1
• Time in Patent Office: 1,244 Days
• Field of Search: 398/202, 398/208, 398/209, 398/210, 398/211, 398/214, 398/135, 398/136, 398/137, 398/138, 398/139, 398/141, 398/158, 398/159, 398/161, 398/128, 398/17, 398/24, 398/25, 398/26, 398/27, 250/214.A, 250/214.R, 250/214.AG, 250/214.LA, 250/338.1, 330/59, 330/308, 330/253, 330/306, 375/317, 375/318, 375/22, 375/26, 375/35, 375/37, 327/100, 327/557
• US Class Current: 398/202
• CPC Class Codes: H04B 10/114 Indoor or close-range type systems

Abstract

In an optical communication-use receiving circuit of the present invention, the pulse width of the received pulse which is a binary signal corresponding to the signal optical pulse is specified by using an integration circuit and a trigger generating circuit. If the pulse width of the received pulse is not shorter than a predetermined value, a signal having a fixed pulse width is outputted as an output signal from a one-shot pulse generating circuit, so that a pulse having a constant pulse width corresponding to the specified communication speed is outputted. Accordingly, if the pulse width deriving from the signal optical pulse is larger than a certain value, the communication is deemed as a low-speed communication, and a pulse having a constant pulse width corresponding to the communication speed is outputted. As a result, it is possible to realize a small-size receiving circuit and a small-size electronic device which require no external switching-over terminal.

Claims

1. A receiving circuit, for use in an optical communication, from which an output signal is outputted in accordance with a signal optical pulse incident to a light-receiving element, the receiving circuit comprising:

a variable output circuit for detecting a pulse width of the signal optical pulse, selecting one pulse width from a plurality of pulse widths in accordance with the pulse width thus detected, and outputting an output signal having the one pulse width thus selected;

the variable output circuit includes a first pulse generating circuit generating a received pulse by comparing an electric signal converted from the signal optical pulse with a threshold, the received pulse being a digital signal;

wherein either the received pulse generated by the first pulse generating circuit or a pulse having a different pulse width from that of the received pulse is selectively outputted as an output signal, in accordance with the pulse width of the signal optical pulse;

the variable output circuit includes a second pulse generating circuit for generating a signal having a predetermined pulse width corresponding to a low-speed communication; and

if it is judged that a pulse width of an output from the first pulse generating circuit exceeds a predetermined value, a signal generated by the second pulse generating circuit is outputted as the output signal, instead of outputting the received pulse; and

the variable output circuit includes (I) a trigger generating circuit for generating a trigger signal when a pulse generating time of the first pulse generating circuit exceeds a first predetermined period, and (II) a timer circuit for generating a pulse having a second predetermined period, in response to the trigger signal from the trigger generating circuit;

if the timer circuit outputs no pulse, a pulse outputted from the first pulse generating circuit is outputted as the output signal; and

if the timer circuit outputs a pulse, a pulse outputted from the second pulse generating circuit is outputted as the output signal.

2. The receiving circuit as set forth in claim 1, wherein:

a length of the first predetermined period is set between a pulse width of the output pulse from the second pulse generating circuit and a pulse width of the output pulse from the first pulse generating circuit.

3. The receiving circuit as set forth in claim 2, wherein the first predetermined period is between 521 n sec. and 1.41 μ

sec.

4. The receiving circuit as set forth in claim 1, wherein the second predetermined period is equal to or longer than a maximum interval between a pulse and another pulse.

5. The receiving circuit as set forth in claim 4, wherein the second predetermined period is 1.04 m sec. or longer.

6. The receiving circuit as set forth in claim 1, further comprising:

an amplifying circuit for amplifying an electronic signal converted from the signal optical pulse,

the variable output circuit switching over, in accordance with a communication speed, a frequency band of the amplifying circuit during the period when the pulse of the second predetermined period exists.

7. The receiving circuit as set forth in claim 1, wherein:

during the period when the pulse of the second predetermined period exists, the variable output circuit switches over a response speed of the variable output circuit, in accordance with a communication speed.

8. A receiving circuit, for use in an optical communication, from which an output signal is outputted in accordance with a signal optical pulse incident to a light-receiving element, the receiving circuit comprising:

a variable output circuit for detecting a pulse width of the signal optical pulse, selecting one pulse width from a plurality of pulse widths in accordance with the pulse width thus detected, and outputting an output signal having the one pulse width thus selected;

the variable output circuit includes a first pulse generating circuit generating a received pulse by comparing an electric signal converted from the signal optical pulse with a threshold, the received pulse being a digital signal;

wherein either the received pulse generated by the first pulse generating circuit or a pulse having a different pulse width from that of the received pulse is selectively outputted as an output signal, in accordance with the pulse width of the signal optical pulse;

the variable output circuit includes a second pulse generating circuit for generating a signal having a predetermined pulse width corresponding to a low-speed communication; and

if it is judged that a pulse width of an output from the first pulse generating circuit exceeds a predetermined value, a signal generated by the second pulse generating circuit is outputted as the output signal, instead of outputting the received pulse; and

wherein the first pulse generating circuit includes a one-shot pulse generating circuit that receives the received pulse and maintains the pulse width of the output signal at a constant value.

9. The receiving circuit as set forth in claim 8, further comprising a delay circuit connected to an output of the one-shot pulse generating circuit.

10. A receiving circuit, for use in an optical communication, from which an output signal is outputted in accordance with a signal optical pulse incident to a light-receiving element, the receiving circuit comprising:

a variable output circuit for detecting a pulse width of the signal optical pulse, selecting one pulse width from a plurality of pulse widths in accordance with the pulse width thus detected, and outputting an output signal having the one pulse width thus selected;

the variable output circuit includes a first pulse generating circuit generating a received pulse by comparing an electric signal converted from the signal optical pulse with a threshold, the received pulse being a digital signal;

wherein either the received pulse generated by the first pulse generating circuit or a pulse having a different pulse width from that of the received pulse is selectively outputted as an output signal, in accordance with the pulse width of the signal optical pulse;

the variable output circuit includes a second pulse generating circuit for generating a signal having a predetermined pulse width corresponding to a low-speed communication; and

if it is judged that a pulse width of an output from the first pulse generating circuit exceeds a predetermined value, a signal generated by the second pulse generating circuit is outputted as the output signal, instead of outputting the received pulse; and

wherein the first pulse generating circuit includes a delay circuit to which the received pulse is inputted.

11. A receiving circuit, for use in an optical communication, from which an output signal is outputted in accordance with a signal optical pulse incident to a light-receiving element,

the receiving circuit comprising:

a variable output circuit for detecting a pulse width of the signal optical pulse, determining a pulse width of the output signal in accordance with the pulse width of the signal optical pulse, and outputting the output signal;

wherein the variable output circuit includes a first pulse generating circuit generating a received pulse by comparing an electric signal converted from the signal optical pulse with a threshold, the received pulse being a digital signal; and

wherein either the received pulse generated by the first pulse generating circuit or a pulse having a different pulse width from that of the received pulse is selectively outputted as an output signal, in accordance with the pulse width of the signal optical pulse;

wherein the variable output circuit further includes a second pulse generating circuit for generating a signal having a predetermined pulse width corresponding to a low-speed communication; and

if it is judged that a pulse width of an output from the first pulse generating circuit exceeds a predetermined value, a signal generated by the second pulse generating circuit is outputted as the output signal, instead of outputting the received pulse; and

wherein the variable output circuit still further includes a trigger generating circuit for generating a trigger signal when a pulse generating time of the first pulse generating circuit exceeds a first predetermined period, and a timer circuit for generating a pulse having a second predetermined period, in response to the trigger signal from the trigger generating circuit;

if the timer circuit outputs no pulse, a pulse outputted from the first pulse generating circuit is outputted as the output signal; and

if the timer circuit outputs a pulse, a pulse outputted from the second pulse generating circuit is outputted as the output signal.