JP3134358B2 - Digital tone receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital tone receiver for receiving and identifying various audible signal tones by digital signals.

[0002]

2. Description of the Related Art Conventionally, in a digital tone receiver of this kind, after a digital filter first discriminates a frequency of a received digital signal, a power value obtained by calculating an absolute value and integrating the calculated value for a certain period of time is calculated. , When it exceeds a predetermined threshold value, it is determined that the signal of the discriminated frequency has been received.

FIG. 2 is a block diagram showing an example of the related art.

As shown in the figure, an input signal 11 passes through a digital filter 1 and is subjected to frequency discrimination. Then, a power calculator 10 calculates power for each frequency. When the input value is a value exceeding a predetermined value at a predetermined threshold value, the determination unit 6 that inputs the calculated value determines that a signal of a frequency having this value has been received and outputs the signal as a reception result 12. I do.

[0005]

The above-mentioned conventional digital tone receiver has a configuration in which after a frequency filter is discriminated by a digital filter, power is calculated by a received signal to detect a tone of a received frequency. When the reference level of the waveform is different from the predetermined zero level, the threshold for judging the reception of the tone from the input signal cannot function accurately, and the correct tone cannot be received, so that there is a disadvantage that the reception may be erroneous.

SUMMARY OF THE INVENTION An object of the present invention is to provide a digital tone receiver which solves the above-mentioned drawback by calculating an offset value of a tone signal having a frequency discriminated from an input signal to correct a received signal level.

[0007]

A digital tone receiver according to the present invention includes a digital filter for discriminating a digital signal to be received into a specific frequency signal, an absolute value of an output of the filter being calculated, added for a predetermined time, and accumulated. A power calculator for outputting a value, an offset calculator for adding an output of the digital filter for a certain period of time to calculate an offset value with respect to a predetermined zero level, and correcting the output of the power calculator with the calculated offset value. An offset corrector that outputs the output signal, and a determiner that compares the output of the offset corrector with a predetermined threshold to determine the digital signal to be received and output the result.

[0008]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

As shown in FIG. 1, a digital tone receiver converts an input signal 11 to be received from a digital filter 1 through a power calculator 10 composed of an absolute value calculator 2 and a cumulative calculator 3, while calculating an offset. The level is calculated by the unit 4, the level is corrected by the offset correction unit 5, and the result is transferred to the determination unit 6.

The input signal 10 is input to the digital filter 1 and is discriminated into a signal of a specific frequency. The output of the digital filter 1 is input to the absolute value calculation unit 2, where the absolute value is obtained.

The output of the absolute value calculating unit 2 is input to a cumulative calculating unit 3, where the absolute value is added for a certain period of time to calculate the cumulative absolute value, and is calculated as the power value of the discriminated specific frequency component.

The output of the digital filter 1 is also input to an offset calculator 4, where the output of the digital filter 1 is added for a certain period of time to calculate an offset value for a predetermined zero level.

The output power value of the accumulation calculator 3 and the output offset value of the offset calculator 4 are input to an offset corrector 5, which corrects the effect of the offset by subtracting the offset value from the power value. The calculated power value is calculated and output.

The output of the offset correction unit 5 is input to a determination unit 6, which compares the power value corrected for the influence of the offset with a predetermined threshold value, performs a reception determination process, and determines the reception result 11. Output.

The reception determination process counts the time when the power value is greater than the threshold value, and outputs a reception result 11 indicating that a tone has been detected when the time is longer than a predetermined time. Of course, the reception determination process may use other determination processing means.

[0017]

As described above, according to the present invention, after the input signal is discriminated by the digital filter, the power value of the specific frequency component is calculated by accumulating the absolute value of the output of the digital filter for a certain period of time. By calculating the offset value of the output of the filter and subtracting this offset value from the power value, the effect of the offset is corrected, so that a correct power value without the effect of the offset can be obtained. There is an effect that can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Digital filter 2 Absolute value calculation part 3 Accumulation calculation part 4 Offset calculation part 5 Offset correction part 6 Judgment part 10 Power calculation part 11 Input signal 12 Reception result

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 27/00 H04L 27/26

Claims (1)

(57) [Claims] 1. A digital filter for discriminating a received digital signal into a specific frequency signal, a power calculation unit for calculating an absolute value of an output of the filter, adding the output for a fixed time and outputting a cumulative value, and An offset calculating unit that adds an output for a predetermined time to calculate an offset value with respect to a predetermined zero level, an offset correcting unit that corrects and outputs an output of the power calculating unit with the calculated offset value, and an offset correcting unit. A digital tone receiver comprising: a comparator for comparing the output of the digital tone signal with a predetermined threshold to determine a digital signal to be received and outputting a result;