Modulating circuit, demodulating circuit and modulating and demodulating circuit system, using PPM method

• US 6,442,200 B1
• Filed: 07/01/1998
• Issued: 08/27/2002
• Est. Priority Date: 07/03/1997
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Fukui, Ryoh
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): BURD, KEVIN MICHAEL
• Application Number:
  US09/108,548
• Time in Patent Office: 1,518 Days
• Field of Search: 375/239, 329/313, 332/112, 370/213, 341/183, 341/187, 359/154, 359/181, 359/184, 359/185
• US Class Current: 375/239
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation

Abstract

A demodulating circuit demodulates a PPM signal obtained as a result of modulation performed in accordance with a PPM method. This circuit includes a detecting portion and a control portion. The detecting portion detects a predetermined carrier pulse provided within a symbol period of the PPM signal, using a clock signal having a frequency double or higher than double the transmission rate of the PPM signal. The controlling portion stops supply of the clock signal to the detecting circuit after the detecting portion detects the predetermined carrier pulse until the subsequent symbol period starts.

Claims

1. A modulating circuit for modulating an input data signal into a PPM signal in accordance with a PPM method, comprising:

counting means for dividing a predetermined amount of the input data signal into divisions, each division having a predetermined number of bits, and counting an appearance frequency of the divisions of the input data signal for each identical data;

setting means for setting, in accordance with the appearance frequency of the divisions of the input data signal counted for each identical data by said counting means, a conversion rule in accordance with which the divisions of the input data signal are converted into the PPM signal for each identical data;

modulating means for modulating the predetermined amount of the input data signal into the PPM signal in accordance with the conversion rule set by said setting means; and

outputting means for outputting data of the conversion rule and the PPM signal.

2. The modulating circuit, according to claim 1, wherein:

said setting means sets such a conversion rule that each of the divisions of the input data signal which have common identical data appearing more frequently is converted into the PPM signal in which a carrier pulse is provided earlier within a symbol period.

3. A modulating and demodulating circuit system, comprising:

a modulating circuit for modulating an input data signal into a PPM signal in accordance with a PPM method, comprising;

counting means for dividing a predetermined amount of the input data signal into divisions, each division having a pre determined number of bits, and counting an appearance frequency of the divisions of the input data signal for each identical data;

setting means for setting, in;

accordance with the appearance frequency of the divisions of the input data signal counted for each identical data by said counting means, a conversion rule in accordance with which the divisions of the input data signal are converted into the PPM signal for each identical data;

modulating means for modulating the predetermined amount of the input data signal into the PPM signal in accordance with the conversion rule set by said setting means; and

outputting means for outputting data of the conversion rule and the PPM signal; and

a demodulating circuit, comprising;

a detecting circuit detecting a predetermined carrier pulse provided within a symbol period of a PPM signal, using a clock signal having a frequency double or higher than double a transmission rate of the PPM signal;

controlling means for stopping supply of the clock signal to said detecting circuit after said detecting circuit detects the predetermined carrier pulse until a subsequent symbol period starts; and

demodulating means for demodulating the PPM signal based on the data of the conversion rule which is sent from said modulating circuit together with the PPM signal.

4. The modulating and demodulating circuit system, according to claim 3, wherein:

said setting means sets such a conversion rule that each of the divisions of the input data signal which have common identical data appearing more frequently is converted into the PPM signal in which the carrier pulse is provided earlier within the symbol period.

5. A modulating circuit for modulating an input data signal into a PPM signal in accordance with a PPM method, comprising:

a counting portion dividing a predetermined amount of the input data signal into divisions, each division having a predetermined number of bits, and counting an appearance frequency of the divisions of the input data signal for each identical data;

a setting portion setting, in accordance with the appearance frequency of the divisions of the input data signally counted for each identical data by said counting portion, a conversion rule in accordance with which the divisions of the input data signal are converted into the PPM signal for each identical data;

a modulating portion modulating the predetermined amount of the input data signal into the PPM signal in accordance with the conversion rule set by said setting portion; and

an outputting portion outputting data of the conversion rule and the PPM signal.

6. The modulating circuit, according to claim 5, wherein:

said setting portion sets such a conversion rule that each of the divisions of the input data signal which have common identical data appearing more frequently is converted into the PPM signal in which a carrier pulse is provided earlier within a symbol period.

7. A modulating and demodulating circuit system, comprising:

a modulating circuit modulating an input data signal into a PPM signal in accordance with a PPM method, comprising;

a counting portion dividing a predetermined amount of the input data signal into divisions, each division having a predetermined number of bits, and counting an appearance frequency of the divisions of the input data signal for each identical data;

a setting portion setting, in accordance with the appearance frequency of the divisions of the input data signal counted for each identical data by said counting portion, a conversion rule in accordance with which the divisions of the input data signal are converted into the PPM signal for each identical data;

a modulating portion modulating the predetermined amount of the input data signal into the PPM signal in accordance with the conversion rule set by said setting portion; and

an outputting portion outputting data of the conversion rule and the PPM signal; and

a demodulating circuit, comprising;

a detecting portion detecting a predetermined carrier pulse provided within a symbol period of a PPM signal, using a clock signal having a frequency double or higher than double a transmission rate of the PPM signal;

a controlling portion stopping supply of the clock signal to said detecting portion after said detecting portion detects the predetermined carrier pulse until a subsequent symbol period starts; and

a demodulating portion demodulating the PPM signal based on the data of the conversion rule which is sent from said modulating circuit together with the PPM signal.

8. The modulating and demodulating circuit system, according to claim 7, wherein:

said setting portion sets such a conversion rule that each of the divisions of the input data signal which have common identical data appearing more frequently is-converted into the PPM signal in which the carrier pulse is provided earlier within the symbol period.

9. A modulating method for, modulating an input data signal into a PPM signal in accordance with a PPM method comprising:

dividing a predetermined amount of the input data signal into divisions, each division having a predetermined number of bits, and counting an appearance frequency of the divisions of the input data signal for each identical data;

setting, in accordance with the appearance frequency of the divisions of the input data signal counted for each identical data, al conversion rule in accordance with which the divisions of the input data signal are converted into the PPM signal for each identical data;

modulating the predetermined amount of the input data signal into the PPM signal in accordance with the conversion rule set; and

outputting data of the conversion rule and the PPM signal.

10. A modulating and demodulating method, comprising:

modulating an input data signal into a PPM signal in accordance with a PPM method, the modulating method comprising;

dividing a predetermined amount of the input data signal into divisions, each division having a predetermined number of bits, and counting an appearance frequency of the divisions of the input data signal for each identical data;

setting, in accordance with the appearance frequency of the divisions of the input data signal counted for each identical data, a conversion rule in accordance with which the divisions of the input data signal are converted into the PPM signal for each identical data;

modulating the predetermined amount of the input data signal into the PPM signal in accordance with the conversion rule set; and

outputting data of the conversion rule and the PPM signal; and

a demodulating method, comprising;

detecting a predetermined carrier pulse provided within a symbol period of a PPM signal, using a clock signal having a frequency double or higher than double a transmission rate of the PPM signal;

stopping supply of the clock signal to said detecting circuit after said detecting detects the predetermined carrier pulse until a subsequent symbol period starts; and

demodulating the PPM signal based on the data of the conversion rule which is sent with the PPM signal.