Band correcting apparatus

• US 20060142999A1
• Filed: 02/26/2004
• Published: 06/29/2006
• Est. Priority Date: 02/27/2003
• Status: Active Grant

• Current Assignee: OKI Electric Industry Company Limited
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Takada, Masashi, Murakami, Yoshinari
• Granted Patent: US 7,805,293 B2
• Time in Patent Office: Days
• US Class Current: 704/205
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 21/0364 for improving intelligibility

Abstract

A voice band correcting apparatus in which the signal level of limit bands is amplified by a correction filter, the signal level of a correction signal supplied is compared by a level detector to a preset level, and the result of decision is sent as level information to a coefficient controller, where the signal level is adjusted in a controlled manner. The high-quality broadband signal may be obtained on correction without degrading the quality of a communication signal ascribable to excess amplification.

Claims

1. A band correcting apparatus comprising:

a corrector receiving with an input signal limited in frequency band for correcting the input signal with respect to a signal level of each limit band and outputting a corrected signal;

a monitor for monitoring whether or not the signal level of the corrected signal reaches a preset level; and

a level adjustor for adjusting the signal level responsive to level information from said monitor.

2. The apparatus in accordance with claim 1, wherein said level adjustor includes a coefficient controller for controlling a coefficient correcting the signal level.

3. The apparatus in accordance with claim 1, wherein said level adjustor comprises:

a level amplifier for controlling a coefficient for amplifying the input level; and

a coefficient controller for outputting the coefficient for amplifying the level of the input signal depending on the level information.

4. The apparatus in accordance with claim 1, wherein said corrector comprises a first filter for amplifying a band signal, excluding the input signal, limited in frequency band, and a second filter for applying a delay to a signal of the band excluding the limit band of the band-limited input signal, the delay being substantially equivalent to a delay of the band-limited input signal;

said monitor and said level adjustor being provided correspondingly in number to the band signal of the first filter;

said level adjustor including a coefficient controller and a multiplier for multiplying the coefficient from said coefficient controller with the input signal;

said apparatus further comprising an adder for summing an output of said first and second filter.

5. The apparatus in accordance with claim 4, wherein said monitor is arranged downstream of said adder and sends the level information measured to said level adjustor.

6. The apparatus in accordance with claim 4, further comprising a band splitter arranged upstream of said level adjustor for further separating and band-limiting the band-limited input signal.

7. The apparatus in accordance with claim 6, wherein said monitor is arranged downstream of said adder and sends the level information measured to said level adjustor.

8. The apparatus in accordance with claim 6, wherein said band splitter comprises third filters for splitting the input signal supplied into a plurality of frequency bands;

one of said third filters delaying a signal of a band other than the limit band of the band-limited input signal in an amount substantially equal to the delay of said second filter.

9. The apparatus in accordance with claim 6, further comprising a fourth filter for sampling an output of said corrector with a sampling frequency different from a sampling frequency applied to the output of said corrector, for processing of said band splitter.

10. The apparatus in accordance with claim 8, further comprising fourth filters for sampling an output of said corrector with a sampling frequency different from a sampling frequency applied to the output of said corrector, for processing of said band splitter.

11. The apparatus in accordance with claim 9, wherein said apparatus conforms to the standard of the ITU-T (International Telecommunication Union Telecommunication standardization sector) recommendations G.722.

12. The apparatus in accordance with claim 10, wherein said apparatus conforms to the standard of the ITU-T (International Telecommunication Union Telecommunication standardization sector) recommendations G.722.

13. A band correcting apparatus comprising:

a band splitter for splitting a band of an input signal into a plurality of limit bands;

a corrector for correcting a signal level of the bands obtained on splitting for outputting correction signals; and

an analog converter for converting each of the correction signals into analog signals.

14. The apparatus in accordance with claim 13, wherein said band splitter comprises:

a first delay circuit for applying a delay to a signal other than the limit band of the band-limited input signal, the delay being substantially equivalent to a delay attendant on filtering of the band-limited input signal; and

a second delay circuit for applying a delay substantially equivalent to a delay attendant on processing by said corrector.

15. The apparatus in accordance with claim 14, wherein said corrector comprises:

a first filter for amplifying a band signal output from said first delay circuit; and

a second filter for amplifying a band signal output from said second delay circuit.

16. The apparatus in accordance with claim 13, wherein said apparatus conforms to the standard of the ITU-T (International Telecommunication Union Telecommunication standardization sector) recommendations G.722.

17. The apparatus in accordance with claim 16, wherein said band splitter comprises a quadrature mirror filter for conforming to said standard and splitting the band of the input signal into a low sub-band and a high sub-band;

said corrector including;

a low-range corrector for correcting a level of the low sub-band; and

a high-range corrector for correcting a level of the high sub-band;

said apparatus being further comprising a shifter for shifting a frequency of an output signal of the high sub-band output by said analog converter.

18. The apparatus in accordance with claim 17, further comprising a third filter provided downstream of said low-range corrector for splitting the band.

19. The apparatus in accordance with claim 18, wherein said fifth filter includes a quadrature mirror filter.

20. The apparatus in accordance with claim 17, further comprising a phase adjustor for adjusting a phase or a delay of an output signal from said low-range corrector.

21. The apparatus in accordance with claim 18, further comprising a phase adjustor for adjusting a phase or a delay of an output signal from said third filter.