RU2202857C2 - Tone signal receiver - Google Patents

Abstract

FIELD: radio engineering; multichannel communication systems. SUBSTANCE: device designed to receive tone signals in multichannel communication systems is provided with newly introduced four integrating sections, subtractor, ratio computing unit, threshold element, and display unit. Estimates of signal power in data band, input signal energy distribution over frequency band, peak factor of signal received, and degree of irregularity of input signal envelope in band filter are used as resolving characteristics. EFFECT: enhanced precision of tone signal discrimination. 1 dwg

Description

 The invention relates to the field of telecommunications, in particular to means for receiving channel signaling signals in multi-channel communication systems, and can be used, for example, to detect tonal signals in telephone channels.

 The main problems of receiving tonal signaling signals are as follows. In practice, the reception of tonal signaling signals is complicated, firstly, by the significant uncertainty of the received signal (in frequency, level, and even shape), and, secondly, by the need to detect such signals against the background of very significant interference (the most typical here are smooth channel noise , impulse noise and spurious speech signals). This is due to the wide variety of tone generators, and also to a large extent depends on the path and method of transmitting signals over communication channels. As a result, at the point of reception there is a danger of skipping the information signal or receiving instead of it some other spurious signal (for example, signals exchanging documentary communications, speech or music signal).

 A device for receiving tonal signals is known, comprising a matching block with a channel, a bandpass filter, two resonant circuits connected in series, two linear detectors, two polarized relays, a threshold element, and an actuator. Here, the separation of the tonal (information) signal and the stray currents of speech frequencies is carried out through the use of two resonant circuits. Voltages removed from these circuits, after rectification, are applied to a polarized relay with two windings wound in the opposite direction. As a result, this receiver steadily selects a signal whose spectrum contains only spectral components in the information frequency band.

 However, this device cannot provide reliable selection of tonal signals subjected to significant distortion, as well as the information signal, which is received against the background of speech. In addition, in the case of a significant detuning in the frequency of the tone generator, the operation of this receiver will be accompanied by frequent omissions.

 Also known is a receiver of tonal signals, comprising a matching unit with a communication channel, four one-vibrators, an inverter, two logical elements AND, an integrating element, an executive element. However, this device is also characterized by a low accuracy of extracting the information signal, which is associated with the possibility of processing the receiver on a spurious signal, as well as the high probability of missing a distorted acoustic signal.

 Closest in technical essence to the claimed device is a device for separating acoustic signals in communication channels, comprising a matching unit with a communication channel, a bandpass filter, first, second and third linear detectors, first and second integrating links, first, second and third threshold elements , the first and second blocks of calculating the relationship, the peak detector, the first and second logical elements AND, register, control timer and actuator.

 The principle of operation of this device is based on the assessment of three decisive statistics, which are the hallmarks of recognition of an informational acoustic signal from channel noise and spurious speech signals. The following statistics are used as decisive statistics: estimation of the signal power in the information frequency band, distribution of the input signal power over the frequency range, and the peak factor of the input signal.

 However, when this device is operating, errors may also occur if the form of the received tone signal differs from the sinusoidal one. On the other hand, with an increase in the receiver threshold by the peak factor of the received signal, the probability of false alarms will inevitably increase, which is also unacceptable in alarm systems. Thus, in order to increase the reliability of receiving tonal signals into the device, it is advisable to introduce another additional feature that allows more fully use a priori information about the possible form of the signal at the point of its reception.

 The purpose of the invention is to improve the accuracy of the selection of tone signals.

 To achieve this goal, a device for receiving tonal signaling signals, comprising a matching unit with a communication channel, a band-pass filter, first and second integrating links, AND logic element, first, second and third linear detectors, first and second relationship calculation units, peak detector, the first, second and third threshold elements and a control timer, according to the invention, third, fourth, fifth and sixth integrating links, a subtracter, a third ratio calculating unit, a fourth p a horn element and a display unit, the output of the matching unit with the communication channel being connected to the inputs of the bandpass filter and the first linear detector, the output of the first linear detector through the first integrating link is connected to the first input of the first ratio calculation unit, the output of which is connected to the first input through the first threshold element logical element And, while the output of the bandpass filter is connected to the inputs of the peak detector and the sixth integrating link, and also through the second linear detector is connected to the input the second, third and fourth integrating links, in turn, the output of the second integrating link is connected to the second input of the first unit for calculating the relationship, to the second input of the second unit for calculating the ratio and through the second threshold element to the second input of the logical element AND, in addition, the output of the third integrating unit connected to the first input of the subtractor, and the output of the fourth integrating link with the second input of the subtracter, while the output of the subtractor through the third line detector and the fifth and the tagging unit is connected to the first input of the second unit for calculating the ratio, the output of which through the third threshold element is connected to the third input of the logical element AND, while the output of the peak detector is connected to the first input of the third unit for calculating the ratio, the second input of which is connected to the output of the sixth integrating unit, and output - with the input of the fourth threshold element, the output of the latter is connected to the fourth input of the logical element AND, the output of which is connected to the input of the display unit, and the output of the control tie EPA is connected to the control input of the logical element I.

 A device for receiving tonal signaling signals (see the drawing) contains a matching unit 1 for a communication channel, a bandpass filter 2, a first linear detector 3, a first integrating link 4, a first threshold element 5, a second linear detector 6, a second integrating link 7, and a first block 8, ratio calculation, second threshold element 9, third integration link 10, fourth integration link 11, subtractor 12, third line detector 13, fifth integration link 14, second ratio calculation block 15, third threshold element 16, peak det 17 Torr, the sixth integrating unit 18, a third ratio calculation unit 19, the fourth threshold element 20, an AND gate 21, a display unit 22 and the control timer 23.

 In the claimed device, the decision on the appearance of a tone signal in the communication channel is made after the coincidence of all characteristic features, which are significant statistical criteria for highlighting this type of signal. In practice, the evaluation of characteristic features in the inventive device is carried out by calculating four crucial statistics. Together, all calculated statistics provide recognition of the information acoustic signal from channel noise, spurious speech signals, network interference, impulse noise and other distortions. Here, the following statistics are used as decisive statistics: estimation of the signal power in the information frequency band, the distribution of the input signal energy over the frequency range, the peak factor of the received signal and the level of envelope unevenness of the input signal filtered in the band-pass filter.

 The analyzed signal from the output of the communication channel, passing through block 1 matching with the communication channel, is fed simultaneously to the input of the bandpass filter 2, as well as to the input of the first linear detector 3.

 Moreover, in blocks 2-4, an estimate of the power of the incoming signal in the entire frequency band of the communication channel is formed, for which the original signal is rectified in the first linear detector 3 and accumulated in the first integrating link 4.

 An approximate estimate of the signal power limited by the information frequency band (i.e., the frequency band in which the tone message can be based on a priori information) is generated by blocks 2, 6, 7. For this, the input signal passes through a bandpass filter 2. Bandwidth bandpass filter 2 corresponds to the information band of the tone signal. Next, the received signal is detected by the second linear detector 6 and accumulated in the second integrating link 7.

 An estimate of the input signal power limited by the information frequency band is used in the inventive device as the first decisive feature (or, alternatively, a statistical criterion) when deciding on the presence of a tone signal in a channel. The main purpose of introducing this feature into the inventive device is to prevent false alarms of the detector from signals whose spectrum is located outside the information frequency band. To calculate this decisive statistics, the signal from the output of the second integrating link 7 is fed to the second threshold element 9, where a comparison with the boundary (threshold) value is performed. The result of the comparison goes to the first input of the And 21 logic element. If the signal level in the information strip exceeds a threshold value, then the logical unit is fixed at the first input of the And 21 logic element.

 To obtain the second feature, the signal from the output of the second integrating link 7 is fed to the second input of the first unit 8 of the ratio calculation. At the first input of the ratio calculation unit 8, a signal is received from the output of the first integrating link 4.

 As a result, at the output of the first relationship calculating unit 8, we have a value characterizing the distribution of the energy of the input signal over the frequency range of the communication channel. In other words, the estimate generated by the first ratio calculating unit 8 is approximately equal to the ratio of the signal power at the output of the bandpass filter 2 to the signal power at the input of the device. The introduction of the second feature allows the detection of a tone signal to avoid errors associated with false alarms on multi-frequency (for example, speech, music, etc.) signals. Here we use the well-known feature of the tone signal in the channel signaling, which consists in the fact that the power of the tone signal is concentrated in a rather narrow spectral band and exceeds the power of channel interference.

 When implementing the procedure for calculating crucial statistics, the well-known harmonic signal property is used, consisting in the fact that there is a strict dependence between the power of such a signal and the average value of the module. The value thus obtained is compared in the second threshold element 9 with a boundary value. The comparison result in the form of a logical "0" or "1" is fed to the second input of the logical element And 21.

 In blocks 10-16, the formation of the third information feature is carried out - an assessment of the unevenness of the envelope of the filtered signal. This feature is introduced into the inventive device to prevent false alarms on signals, which are characterized by significant variability of its level averaged over a small time interval. An example of such signals are spurious speech signal, non-stationary interference. Indeed, as you know, the envelope of a speech signal changes rapidly. In practice, the length of the "pseudo-stable" portion of the speech envelope very rarely exceeds 200 ms. At the same time, tone parcel generators are characterized by the stability of the average output signal level over the entire duration of the parcel.

 To assess the unevenness of the envelope, the signal from the output of the second linear detector 6 is fed simultaneously to the third and fourth integrating links 10 and 11, which differ in the value of the integration time. A comparison of the obtained values is performed in the subtractor 12. Next, the obtained value is detected (the absolute value of the quantity is calculated) in the third linear detector 13 and averaged in the fifth integrating link 14. Then, the obtained value in the second block for calculating the ratio 15 is normalized to the average level of the filtered signal, the estimate of which is available the output of the second integrating link 7. The resulting value is compared in the third threshold element 16 with a boundary value. The result of the comparison in the form of a logical "0" or "1" is fed to the third input of the logical element And 21.

 The last, fourth, information feature is introduced into the inventive device to increase the stability of distinguishing tonal signals. As such a feature in this device, the peak factor of the input signal passed through the bandpass filter 2 and detected in the second linear detector 6 is used. Here we use a priori information that the peak factor of the harmonic signal (or a signal that is close in shape to harmonic ) is much smaller than the peak factor of the noise signal.

 Assessment of the fourth information feature is as follows. The signal from the output of the second linear detector 6 is fed to the inputs of the peak detector 17 and the sixth integrating link 18. In this case, the peak value of the signal is recorded in the peak detector 17 in the analysis interval, and its average value is calculated in the sixth integrating link 18. Further, in the third block 19 for calculating the ratio, the magnitude of the peak factor of the received signal is estimated. The received value goes to the fourth threshold element 20. If the value obtained at the output of the fourth threshold element 20 is less than the threshold value, then the logical unit is fixed at the fourth input of the logical element And 21.

 Decisions on the presence of a tonal signal in the communication channel are periodically transmitted at intervals of time by command from the control timer 23 from the AND gate 21 to the display unit 22.

 The inventive object can be built using existing electronic means and components of communication equipment or implemented on the basis of computer technology, or using signal processors. This device may find application in the hardware and software of a telephone exchange.

Sources of information
1. Zayonchkovsky E. A., Pshenichnikov A. P., Romantsov V. M. Automatic long distance communication. M .: Radio and communications, 1984, p. 111-115.

 2. Copyright certificate 441681, H 04 M 1/46, 03.01.73.

 3. Patent 2118067, H 04 B 3/46, 04/02/96.

Claims (1)

 A device for receiving tonal signaling signals, comprising a matching unit with a communication channel, a band-pass filter, first and second integrating links, logic element And, first, second and third linear detectors, first and second blocks for calculating the ratio, a peak detector, characterized in that the device additionally introduced the third, fourth, fifth and sixth integrating links, a subtractor, a third ratio calculating unit, a fourth threshold element and a display unit, wherein the output of the matching unit with the communication channel it is single with the inputs of the bandpass filter and the first linear detector, the output of the first linear detector through the first integrating link is connected to the first input of the first unit for calculating the ratio, the output of which through the first threshold element is connected to the first input of the logical element And, while the output of the bandpass filter is connected to the inputs of the peak the detector and the sixth integrating link, and also through the second linear detector is connected to the input of the second, third and fourth integrating links, in turn, the output of the second the integrating unit is connected to the second input of the first unit for calculating the relationship, the second input of the second unit for calculating the ratio and through the second threshold element to the second input of the logical element And, in addition, the output of the third integrating unit is connected to the first input of the subtractor, and the output of the fourth integrating unit to the second input of the subtractor, while the output of the subtractor is connected through a third line detector and a fifth integrating element connected in series to the first input of the second ratio calculation unit, the output which through the third threshold element is connected to the third input of the AND gate, while the output of the peak detector is connected to the first input of the third block for calculating the ratio, the second input of which is connected to the output of the sixth integrating link, and the output is connected to the input of the fourth threshold element, the output of the latter is connected to the fourth input of the logical element AND, the output of which is connected to the input of the display unit, and the output of the control timer is connected to the control input of the logical element I.