Information signal processing apparatus

• US 5,465,071 A
• Filed: 01/27/1995
• Issued: 11/07/1995
• Est. Priority Date: 07/13/1992
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kobayashi, Takashi, Hatae, Shinichi
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US08/379,035
• Time in Patent Office: 284 Days
• Field of Search: 329/327, 329/315, 329/336, 329/341, 329/342, 329/343, 332/117, 360/30, 360/38.1, 455/42, 455/110, 455/337
• US Class Current: 329/315
• CPC Class Codes: H03D 2200/005 Analog to digital conversion
• CPC Class Codes: H03D 2200/0052 Digital to analog conversion
• CPC Class Codes: H03D 2200/0058 using a digital filter with interpolation
• CPC Class Codes: H03D 2200/0062 Computation of input samples, e.g. successive samples
• CPC Class Codes: H03D 2200/0064 Detection of passages through null of a signal
• CPC Class Codes: H03D 2200/0082 Quadrature arrangements
• CPC Class Codes: H03D 3/006 by sampling the oscillations and further processing the samples, e.g. by computing techniques H03D3/007 takes precedence
• CPC Class Codes: H03D 3/007 by converting the oscillations into two quadrature related signals H03D3/245 takes precedence

Abstract

An information signal processing apparatus according to the present invention is arranged to receive as an input a frequency-modulated information signal having a predetermined frequency band, form a sample pulse signal by sampling the input frequency-modulated information signal in accordance with a clock signal having a first frequency which is selected so that a frequency which is 1/n times (n is a positive integer) a frequency of half the first frequency is positioned in a frequency band lower than the frequency band of the input frequency-modulated information signal and so that a frequency which is (n+1) times (n is a positive integer) the frequency of half the first frequency is positioned in a frequency band higher than the frequency band of the input frequency-modulated information signal, and demodulate the frequency-modulated information signal by performing computing processing of the formed sample pulse signal in accordance with the clock signal having the first frequency. According to the above-described arrangement, it is possible to reduce the amount of computation per unit time so that computing processing of the frequency-modulated information signal can be performed by a low-speed computational processing circuit. Accordingly, it is possible to reduce the complexity and cost of the apparatus.

Claims

1. An information signal processing apparatus for processing an information signal, comprising:

(A) sampling means for receiving as its input a frequency-modulated information signal having a predetermined frequency band, forming a sample pulse signal by sampling the input frequency-modulated information signal in accordance with a clock signal having a first frequency representative of a sub-Nyquist frequency of the input frequency-modulated information signal, and outputting the sample pulse signal; and

(B) sample pulse signal computing processing means for performing computing processing of the sample pulse signal outputted from said sampling means, in accordance with the clock signal having the first frequency.

2. An information signal processing apparatus according to claim 1, wherein the frequency-modulated information signal includes a frequency-modulated audio signal, said sample pulse signal computing processing means being arranged to perform demodulation processing of the frequency-modulated audio signal by processing, in accordance with the clock signal having the first frequency, the sample pulse signal outputted from said sampling means.

3. An information signal processing apparatus according to claim 1, wherein said sample pulse signal computing processing means includes:

(a) phase shifting means for receiving as its input the sample pulse signal outputted from said sampling means, shifting a phase of the input sample pulse signal by π

/2 and outputting the sample pulse signal shifted by π

/2 in phase;

(b) division means for receiving as one input the sample pulse signal outputted from said sampling means and as another input the sample pulse signal outputted from said phase shifting means and shifted by π

/2 in phase with respect to the input sample pulse signal, dividing the input sample pulse signal by the sample pulse signal outputted from said phase shifting means and shifted by π

/2 in phase, and outputting a signal indicative of a division result;

(c) tan^-1 processing means for performing tan^-1 processing of the signal outputted from said division means and outputting a signal indicative of a result of the tan^-1 processing;

(d) differentiating means for differentiating the signal outputted from said tan^-1 processing means and outputting a signal indicative of a differentiation result; and

(e) correcting means for performing correction processing of the signal outputted from said differential means and outputting a signal indicative of a result of the correction processing.

4. An information signal processing apparatus for processing an information signal, comprising:

(A) sampling means for receiving as its input a frequency-modulated information signal having a predetermined frequency band, and sampling means forming a sample pulse signal by sampling the input frequency-modulated information signal according to a first clock signal having a frequency larger than two times a maximum value of a frequency component of the frequency-modulated information signal, and outputting the sample pulse signal;

(B) clock signal generating means for generating a second clock signal having a second frequency which is positioned in a frequency band higher than the frequency band of the input frequency-modulated information signal; and

(C) sample pulse signal computing processing means for performing computing processing of the sample pulse signal outputted from said sampling means, in accordance with the second clock signal generating from said clock signal generating means.

5. An information signal processing apparatus according to claim 4, wherein the frequency-modulated information signal includes a frequency-modulated audio signal, said sample pulse signal computing processing means being arranged to perform demodulation processing of the frequency-modulated audio signal by processing, in accordance with the second clock signal having the first frequency, the sample pulse signal outputted from said sampling means.

6. An information signal processing apparatus according to claim 4, wherein said sample pulse signal computing processing means includes:

(a) phase shifting means for receiving as its input the second sample pulse signal outputted from said second sampling means, shifting a phase of the input second sample pulse signal by π

/2 and outputting the sample pulse signal shifted by π

/2 in phase;

(b) division means for receiving as one input the second sample pulse signal outputted from said second sampling means and as another input the second sample pulse signal outputted from said phase shifting means and shifted by π

/2 in phase with respect to the input second sample pulse signal, dividing the input second sample pulse signal by the second sample pulse signal outputted from said phase shifting means and shifted by π

/2 in phase, and outputting a signal indicative of a division result;

(c) tan^-1 processing means for performing tan^-1 processing of the signal outputted from said division means and outputting a signal indicative of a result of the tan^-1 processing;

(d) differentiating means for differentiating the signal outputted from said tan^-1 processing means and outputting a signal indicative of a differentiation result; and

(e) correcting means for performing correction processing of the signal outputted from said differential means and outputting a signal indicative of the correction processing.

7. An information signal processing apparatus for processing an information signal, comprising:

(A) first sampling means for receiving as its input an information signal, forming a sample signal by sampling the input information signal in accordance with a clock signal having a first frequency, and outputting the sample signal;

(B) signal processing means for performing signal processing of the sample signal outputted from said first sampling means and outputting a sample signal indicative of a result of the signal processing;

(C) second sampling means for forming a re-sample signal by re-sampling the sample signal outputted from said signal processing means, in accordance with a clock signal having a second frequency which is n times the first frequency (n is a positive integer of n≧

2), and outputting the re-sample signal; and

(D) filter means for extracting and outputting a high-frequency component of the re-sample signal outputted from said second sampling means.

8. An information signal processing apparatus according to claim 7, wherein the information signal includes an audio signal, said signal processing means being arranged to perform frequency-modulation processing for forming a frequency-modulated audio signal by performing computing processing of the sample signal outputted from said first sampling means.

9. An information signal processing apparatus according to claim 7, wherein said signal processing means includes:

(a) coefficient multiplying means for receiving as its input the sample signal outputted from said first sampling means, multiplying the input sample signal by a predetermined coefficient, and outputting a sample signal indicative of a multiplication result;

(b) coefficient adding means for adding a predetermined coefficient to the sample signal outputted from said coefficient multiplying means and outputting a sample signal indicative of an addition result;

(c) integrating means for integrating the sample signal outputted from said coefficient adding means and outputting a sample signal indicative of an integration result; and

(d) sin function processing means for performing sin function processing of the sample signal outputted from said integrating means and outputting a signal indicative of a result of the sin function processing.

10. An information signal processing apparatus for processing an information signal, comprising:

(A) analog/digital conversion means for receiving as its input an information signal having a predetermined frequency band, converting the input analog information signal into a digital information signal in accordance with a first clock signal having a first frequency, and outputting the digital information signal;

(B) digital information signal computing processing means for performing computing processing of the digital information signal outputted from said analog/digital conversion means in accordance with the first clock signal and outputting a digital information signal indicative of a result of the computing processing;

(C) digital data signal generating means for generating a digital data signal whose signal level is zero;

(D) switching output means for receiving as one input the digital information signal outputted from said digital information signal computing processing means and as another input the digital data signal generated by said digital data signal generating means, and outputting the digital information signal and the digital data signal in an alternately switching manner in accordance with a second clock signal having a frequency of n times the first frequency (n is a positive integer of n≧

2);

(E) filter processing means for subjecting the digital signal outputted from said switching output means to filter processing based on the second clock signal and outputting a digital signal indicative of a result of the filter processing; and

(F) digital/analog conversion means for receiving as its input the digital signal outputted from said filter processing means, converting the input digital signal into an analog signal in accordance with the second clock signal, and outputting the analog signal.

11. An information signal processing apparatus according to claim 10, wherein the information signal includes an audio signal, said digital information signal computing processing means being arranged to perform frequency modulation processing for forming the frequency-modulated audio signal by performing computing processing of a digital audio signal outputted from said analog/digital conversion means, in accordance with the first clock signal.

12. An information signal processing apparatus according to claim 10, wherein said digital information signal computing processing means includes:

(a) coefficient multiplying means for receiving as its input the digital information signal outputted from said analog/digital conversion means, multiplying the input digital information signal by a predetermined coefficient, and outputting a digital information signal indicative of a multiplication result;

(b) coefficient adding means for adding a predetermined coefficient to the digital information signal outputted from said coefficient multiplying means and outputting a digital information signal indicative of an addition result;

(c) integrating means for integrating the digital information signal outputted from said coefficient adding means and outputting a digital information signal indicative of an integration result; and

(d) sin function processing means for performing sin function processing of the digital information signal outputted from said integrating means and outputting a signal indicative of a result of the sin function processing.

13. An information signal processing apparatus for processing an information signal, comprising:

(A) phase shifting means for receiving as its input a frequency-modulated information signal, shifting a phase of the input frequency-modulated information signal by π

/2 and outputting the frequency-modulated information signal shifted by π

/2 in phase;

(B) division means for receiving as one input the frequency-modulated information signal and as another input the frequency-modulated information signal outputted from said phase shifting means and shifted by π

/2 in phase with respect to the input frequency-modulated information signal, dividing the input frequency-modulated information signal by the frequency-modulated information signal outputted from said phase shifting means and shifted by π

/2 in phase, and outputting a signal indicative of a division result; and

(C) dropout detecting means for checking a state of the signal outputted from said division means and detecting on the basis of a check result whether a dropout has occurred in the input frequency-modulated information signal.

14. An information signal processing apparatus according to claim 13, further comprising:

(a) tan^-1 processing means for performing tan^-1 processing of the signal outputted from said division means and outputting a signal indicative of a result of the tan^-1 processing;

(d) differentiating means for differentiating the signal outputted from said tan^-1 processing means and outputting a signal indicative of a differentiation result; and

(c) correcting means for performing correction processing of a D.C. component of the signal outputted from said differential means and outputting a signal indicative of the correction processing.

15. An information signal processing apparatus according to claim 13, wherein said division means is arranged to output an overflow pulse if said division means fails to calculate a division result which lies within a predetermined level range.

16. An information signal processing apparatus according to claim 15, wherein said dropout detecting means is arranged to detect an interval during which the overflow pulse is outputted from said division means, and, if the detected interval during which the overflow pulse is outputted exceeds a predetermined interval, determine that a dropout has occurred in the input frequency-modulated information signal, to output a dropout detection signal.

17. An information signal processing apparatus for processing an information signal, comprising:

(A) sampling means for receiving as its input a frequency-modulated information signal having a predetermined frequency band, said sampling means forming a sample pulse signal by sampling the input frequency-modulated information signal according to a clock signal having a first frequency smaller than two times of a maximum value of a frequency component of the frequency-modulated information signal, but larger than said maximum value of a frequency component of the frequency-modulated information signal, and outputting the sample pulse signal; and

(B) sample pulse signal computing processing means for performing computing processing of the sample pulse signal outputted from said sampling means, in accordance with the clock signal having the first frequency.

18. An information signal processing apparatus according to claim 17, wherein the frequency-modulated information signal includes a frequency-modulated audio signal, said sample pulse signal computing processing means being arranged to perform demodulation processing of the frequency-modulated audio signal by processing, in accordance with the clock signal having the first frequency, the sample pulse signal outputted from said sampling means.

19. An information signal processing apparatus according to claim 17, wherein said sample pulse signal computing processing means includes:

(A) phase shifting means for receiving as its input the sample pulse signal outputted from said sampling means, shifting a phase of the input sample pulse signal by π

/2 and outputting the sample pulse signal shifted by π

/2 in phase;

(B) division means for receiving as one input the sample pulse signal outputted from said sampling means and as another shifting means and shifted by π

/2 in phase with respect to the input sample pulse signal, dividing the input sample pulse signal by the sample pulse signal outputted from said phase shifting means and shifted by π

/2 in phase, and outputting a signal indicative of a division result;

(C) tan^-1 processing means for performing tan^-1 processing of the signal outputted from said division means and outputting a signal indicative of a result of the tan^-1 processing;

(D) differentiating means for differentiating the signal outputted from said tan^-1 processing means and outputting a signal indicative of a differentiation result; and

(E) correcting means for performing correction processing of the signal outputted from said differential means and outputting a signal indicative of a result of the correction processing.