JPH0666841B2 - Multi-frequency signal receiver - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a multi-frequency signal receiver, and more particularly to a multi-frequency signal receiver for training a selection signal in which a plurality of sinusoidal signals are mixed.

[Conventional technology]

In conventional multi-frequency signal receivers, the signal level is significantly different due to the difference in the amount of attenuation of the transmission line.For example, in Japan, the signal reception level range is wide at -5 to -48 dBmO and the audio signal is large. When input to a frequency signal receiver, this signal is often mistakenly received as a multi-frequency signal, which is a problem. This erroneous reception occurs because the voice signal component contains a multi-frequency signal component.

As a means for preventing such erroneous reception, the third formant enhancement method has been conventionally used. The third formant emphasizing method is a method for emphasizing the frequency components near 3 KHz in the received signal. By emphasizing the frequency components other than the multi-wave signal, the multi-frequency signal receiver is erroneously received when the voice signal is input. Is a method to prevent.

[Problems to be solved by the invention]

The conventional multi-frequency signal receiver to which the above-mentioned third formant enhancement method is applied emphasizes the frequency component around 3KHz. Therefore, when a noise signal near 3KHz is input together with the multi-frequency signal, it is mistakenly recognized as a voice signal. In addition, it has a drawback that it is difficult to prevent erroneous reception due to the voice signal when the voice signal is input because the individual difference of the voice signal is large and the frequency component near 3 KHz is small.

[Means for solving problems]

The multi-frequency signal receiver of the present invention is a multi-frequency signal receiver having means for detecting a mixed wave of a plurality of signals each having a predetermined frequency, wherein the detected frequency component is removed from an input signal when the mixed wave is detected. Signal removing means, first power detecting means for detecting a power value of an input signal for a certain period from the time of detecting the mixed wave, and generating a signal indicating the power value, and the constant period from the time of detecting the mixed wave. Second power detecting means for detecting the power value of the signal sent by the signal removing means and generating a signal indicating the power value, and the power shown by the respective sending signals of the first and second power detecting means. The control means controls the values to be compared and outputs the detection result of the mixed wave detection means only when the ratio obtained by dividing the former by the latter is less than or equal to a predetermined threshold value.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of the present invention.
In the figure, an input amplifier 1, a band elimination filter 21 and
22, limiter circuit (LIM) 3, and detection circuits 41 and 42
Is a functional circuit that has been used conventionally, and is connected in the same manner as in the past. When receiving a multi-frequency signal composed of a mixed wave of two frequencies, one for each of the low group frequency (L ₁ ) to (L ₄ ) and the high group frequency (H ₁ ) to (H ₄ ), a detection circuit 41 and 42, that is, one DC component is output from each of the two groups of the low group detection circuit and the high group detection circuit. The voice detection circuit 7 is a circuit newly added to prevent erroneous reception when a voice signal is input, and the output circuit 5 is a detection circuit 41.
OR circuit 51 for generating the logical sum of the output signal groups
And 52, and a NAND circuit 53 for outputting an inverted logical product of the outputs of the two OR circuits 51 and 52,
The output signal of the NAND circuit 53 is connected to the time recovery circuit 58. In the time period restoration circuit 58, when the duration of the multi-frequency signal interruption is measured and reaches a constant value, a reset signal is sent to the output control circuit 59, the output holding circuit 55, and the power detection circuits 75 and 76. The output signal of the output control circuit 59 is given to the end circuit 54 in parallel with the output signal groups of the detection circuits 41 and 42. Therefore, the output signal groups of the detection circuits 41 and 42 are sent to the output holding circuit 55 only when the output control circuit 59 is set.

In the voice detection circuit 7, the output signal of the input amplification circuit 1 is input to the power detection circuit 76 and a band elimination filter (REJ) 71 that eliminates the low group frequencies (L ₁ ) to (L ₄ ), respectively. The REJ71 obtains four output signals from which each frequency component of the low-group wave numbers (L ₁ ) to (L ₄ ) of the multi-frequency signal is removed, and the output signals are input to the selection circuit 72. .
In response to the data L indicating the detection result of the detection circuit 41, the selection circuit 72 selects the output signal of REJ71 and sends it to the band elimination filter (REJ) 73. In the REJ73, four output signals are obtained by removing each _one frequency component of the high group frequencies (H ₁ ) to (H ₄ ) of the multi-frequency signal, and the output signals are input to the selection circuit 74. The selection circuit 74 selects the output signal of the REJ 73 and sends it to the power detection circuit 75 in response to the detection result data H of the detection circuit 42. The power detection circuit 75 detects the power value α1 for a certain period after the detection of the multi-frequency signal. On the other hand, the power detection circuit 76 detects the power value α2 of the input signal for a certain period from the time of detecting the multi-frequency signal. The outputs of the power detection circuits 75 and 76 are input to the comparison circuit 77, and the comparison circuit 77
Of power values α1 and α2 If β is larger than a constant threshold γ (β> γ), it is determined as an audio signal, and if β is smaller than a constant threshold γ (β <γ), a multi-frequency signal is obtained. Then, the set signal is output to the output control circuit 59 only in the latter case. When the output control circuit 59 is set, the detection results of the detection circuits 41 and 42 are held and output from the output holding circuit 55 until reset.

As described above, in the present embodiment, since the received signal is determined as the audio signal or the multi-frequency signal based on the magnitude of the power ratio other than the multi-frequency signal component with respect to the total power of the received signal, erroneous reception is more likely than the conventional circuit. The probability can be reduced.

〔The invention's effect〕

As described above, the present invention removes the multi-frequency signal component detected at the time of signal reception from the input signal, obtains the power value of the frequency component other than the multi-frequency signal, and compares this with the power value of the input signal. As a result, the voice signal can be detected with high accuracy, and an erroneous reception at the time of inputting the voice signal can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1 ... Input amplifier, 21, 22 ... Band elimination filter, 3 ...
… Limiter circuit (LIM), 41, 42 …… Signal detection circuit, 5…
… Output circuit, 7 …… Voice detection circuit, 51,52 …… OR circuit, 53 …… NAND circuit, 54 …… AND circuit, 55 …… Output holding circuit, 71,73 …… Band elimination filter, 72,74 …… Selection circuit, 75,76 …… Power detection circuit, 77 …… Comparison circuit, 58…
… Time recovery circuit, 59 …… Output control circuit.

Claims (1)

[Claims] 1. A multi-frequency signal receiver having means for detecting a mixed wave of a plurality of signals each having a predetermined frequency,
A signal removing means for removing the detected frequency component from the input signal when the mixed wave is detected, and a signal for detecting the power value of the input signal for a certain period from the time when the mixed wave is detected and generating a signal indicating the power value A first power detecting means, a second power detecting means for detecting a power value of a signal output from the signal removing means for a certain period from the time of detecting the mixed wave, and generating a signal indicating the power value; The detection results of the mixed wave detection means are output only when the power values indicated by the respective output signals of the first and second power detection means are compared and the latter divided by the former is less than or equal to a predetermined threshold value. And a control means for controlling the multi-frequency signal receiver.