KR200299025Y1 - DTMF detector by using adaptive algorithm - Google Patents

Abstract

The present invention provides an apparatus for detecting DTMF using an adaptive algorithm, comprising: an adaptive filter unit 11 for adaptive filtering by receiving a reference DTMF signal; A noise canceller 12 configured to remove the noise of the input DTMF signal by using the output of the adaptive filter 11 as a reference signal to discriminate the input DTMF signal, thereby using an adaptive algorithm. Even if the DTMF signal contains noise, the DTMF signal can be accurately determined.

Description

DTMF detector using adaptive algorithm

The present invention relates to a DTMF (Dual Tone Multi Frequency) detection device, and more particularly, to an DTMF detection device using an adaptive algorithm that is suitable for accurately determining a DTMF signal even when noise is included in the DTMF signal using an adaptive algorithm. It is about.

In general, DTMF is a signal generated when a button on a regular telephone is pressed and sent to a telephone company. In the United States and many other countries, the old telephone that replaced the dial telephone is called a touch tone telephone or an electronic telephone.

In a telephone with DTMF, each key of the telephone you press produces two notes with a specific frequency. Thus, one voice is a note belonging to a high frequency, and the other is a note belonging to a low frequency, so that the voice cannot imitate the note.

Signals generated when the button of the touchtone phone is pressed are shown in Table 1 below.

text One 2 3 4 5 6 7 8 9 0 * # Low frequency (Hz) 697 697 697 770 770 770 852 852 852 941 941 941 High frequency (Hz) 1209 1336 1477 1209 1336 1477 1209 1336 1477 1336 1209 1477

The DTMF signal of the telephone is thus made of a combination of frequencies consisting of the low frequency groups (697, 770, 852, 941 Hz) and the high frequency groups (1209, 1336, 1477, 1633 Hz). Therefore, it is possible to determine the DTMF signal of the telephone just by accurately determining the combined frequency.

The conventional method of discriminating such a DTMF signal is to measure the DTMF signal in the frequency domain. Therefore, when measured in the frequency domain, the magnitude (magnitude) is large at the specific frequency combined, so it is easy to discriminate the DTMF signal by detecting only this.

Indeed, many commonly used methods are basically based on this method.

The method of converting the signal in the time domain into the frequency domain uses the Goertzel Algorithm, which has a small amount of computation.

If only briefly describes the result of the Gorcel algorithm which is currently used the most can be expressed as the following equation (1) and (2).

Where V _k (-1) = 0, V _k (-2) = 0, and x (n) = input.

Based on the Görcel algorithm, if N = 102, the correlation between DTMF and k value is shown in Table 2 below.

DTMF k 697 9 770 10 852 11 941 12 1209 15 1336 17 1477 19 1633 21

Therefore, since the DTMF signal is a combination of two frequencies, the DTMF signal can be determined by obtaining a k value corresponding to the DTMF signal by using the Görcel algorithm.

The advantage of the Görcel algorithm is that it has a small amount of computation. Since k value corresponding to each DTMF signal is determined, DTMF signal can be quickly and easily identified.

However, this conventional technology has a problem that affects the entire frequency band due to the frequency characteristics of the noise because the noise is also converted to the frequency domain in the noise included state. In this case, simply using the Görcel algorithm causes a problem that it is impossible to determine the correct DTMF signal due to noise.

Therefore, the present invention is proposed to solve the above-mentioned conventional problems, and an object of the present invention is to provide an adaptive algorithm that can accurately identify a DTMF signal even when noise is included in the DTMF signal using an adaptive algorithm. It is to provide a DTMF detection device used.

DTMF detection apparatus using an adaptive algorithm according to an embodiment of the present invention to achieve the above object,

An adaptive filter unit for adaptively receiving a reference DTMF signal; It is characterized in that it comprises a noise removing unit for removing the noise of the input DTMF signal by using the output of the adaptive filter unit as a reference signal to determine the input DTMF signal.

1 is a block diagram of an adaptive filter used in the present invention,

2 is a block diagram of a DTMF detection apparatus using an adaptive algorithm according to the present invention.

Explanation of symbols on the main parts of the drawings

11, 21, 31: adaptive filter section 12, 22, 32: noise canceling section

50: DTMF detection unit

Hereinafter, an embodiment according to the technical idea of the DTMF detection apparatus using the present invention and adaptive algorithm configured as described above will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an adaptive filter used in the present invention.

As shown therein, an adaptive filter unit 11 for adaptively filtering the reference DTMF signal; And a noise canceling unit 12 for removing the noise of the input DTMF signal by using the output of the adaptive filter unit 11 as a reference signal to determine the input DTMF signal.

2 is a block diagram of a DTMF detection apparatus using an adaptive algorithm according to the present invention.

As shown therein, an adaptive filter unit 11 for adaptively filtering the reference DTMF signal; A noise canceling unit (12) for removing noise of the input DTMF signal by using the output of the adaptive filter unit (11) as a reference signal; And a DTMF detector 50 that receives the output of the noise canceling unit 12 and detects a DTMF signal to determine the type of DTMF signal.

In addition, the adaptive filter unit and the noise removing unit 12 may be configured as 16 units.

Accordingly, first to sixteenth adaptive filter units 11, 21, 31 for receiving the reference DTMF signal and adaptively filtering each other; First to sixteenth noise canceling units 12 and 22 that respectively remove noise of an input DTMF signal using the outputs of the first to sixteenth adaptive filter units 11 and 21 and 31 as reference signals; 32); And a DTMF detector 50 that receives the outputs of the first to sixteenth noise cancelers 12, 22 and 32 to detect DTMF signals to determine the type of DTMF signals.

In the above, the DTMF detection unit 50 receives the outputs of the first to sixteenth noise cancellers 12, 22 and 32 as the input DTMF by selecting a reference signal of the adaptive filter that converges the fastest. Determine.

The operation of the DTMF detection apparatus using the adaptive algorithm according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

First, the present invention aims to accurately discriminate DTMF signals even in the presence of noise using an adaptive algorithm.

The adaptive filter has the configuration as shown in FIG. It is becoming.

The key to adaptive filters is the reference signal. The performance of the adaptive filter depends on how much the reference signal correlates with the input signal.

The configuration of the DTMF signal discriminator using the adaptive filter is shown in FIG. 2, which is composed of 16 adaptive filters.

Due to the characteristics of the adaptive filter, when the reference signal (Reference DTMF signal) correlates most with the input signal, convergence is accelerated. Using this characteristic, if the reference signals of 16 adaptive filters are used as inputs of 16 DTMF signals, and the input DTMF signals are used in common, each adaptive filter operates based on the reference signal.

In this case, the adaptive filter using the most correlated reference signal converges fastest. The reference signal of the adaptive filter that converges the fastest becomes the input DTMF, and the DTMF signal is determined through this process.

As such, the present invention uses the adaptive algorithm to accurately identify the DTMF signal even when the DTMF signal contains noise.

While the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. Therefore, the above description does not limit the scope of the present invention as defined by the limitations of the following claims.

As described above, the DTMF detection apparatus using the adaptive algorithm according to the present invention has an effect of accurately determining the DTMF signal even when noise is included in the DTMF signal using the adaptive algorithm.

Claims (4)

An adaptive filter unit 11 which receives a reference DTMF signal and adaptively filters it; And a noise canceling unit (12) configured to remove the noise of the input DTMF signal by using the output of the adaptive filter unit (11) as a reference signal to determine the input DTMF signal. DTMF detection device used. According to claim 1, DTMF detection apparatus using the adaptive algorithm, DTMF detection apparatus using an adaptive algorithm, characterized in that it further comprises a DTMF detection unit for receiving the output of the noise canceling unit (12) to detect the DTMF signal to determine the type of DTMF signal. The method of claim 2, The adaptive filter unit (11) comprises first to sixteenth adaptive filter units (11) (21) (31) for receiving a reference DTMF signal and adaptively filtering each other; The noise removing unit 12 removes noise of an input DTMF signal by using the outputs of the first to sixteenth adaptive filter units 11 and 21 and 31 as reference signals, respectively. DTMF detection apparatus using an adaptive algorithm, characterized in that the removal unit 12, 22, 32. The method of claim 2 or 3, wherein the DTMF detection unit 50, An adaptive algorithm for determining a DTMF signal by selecting a reference signal of an adaptive filter that receives the output of the first to sixteenth noise cancelers 12, 22, and 32 as the fastest convergence signal as an input DTMF. DTMF detection device used.