JPS6230556B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a multifrequency signal detection method.

In conventional multi-frequency signal detection methods, in order to distinguish between signals and noise and to reduce the influence of noise during signal reception, a comparison circuit and Since a delay circuit is used, it has the disadvantage that even when noise above a certain level is received, this noise is erroneously detected as a normal signal.

The purpose of the present invention is to eliminate such drawbacks by providing a differentiating circuit at the next stage of the rectifier circuit, and by differentiating the output of the rectifier circuit, the output of the rectifier circuit is differentiated between signals with little change in level over time and noise with large change in level over time. It is an object of the present invention to provide a multi-frequency signal detection method that distinguishes between noises and does not generate an output even if noise, which has conventionally been erroneously detected, is received.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIGS. 2 a-i and 3 a-i are waveform diagrams illustrating the operation of the circuit shown in FIG. 1.

In FIG. 1, a multi-frequency signal applied to an input terminal 1 is applied to a plurality of wave generators 2-1 and 2-2 for extracting each frequency included in the multi-frequency signal. After the output of each wave generator is rectified by each rectifier circuit 3-1 and 3-2 (Fig. 2 a, c)
and Fig. 3 a, c, comparison circuits 4-1 and 4-
2 and the differentiation circuit 5. Comparison circuit 4-
1 and 4-2, when there is an input example of a certain level or higher, an output is produced, and the output (FIG. 2 b, d and FIG. 3 b, d is an AND circuit 6-
1 and 6-2. Further, the output signals of the comparator circuit are added together by an adder 8 (FIG. 2e and FIG. 3e) and are applied to a differentiating circuit 5. In the differentiator circuit 5, when receiving a signal (normal signal) with little level fluctuation over time, the rectifier circuit 3-1,
Since the output level of 3-2 and 3-2 is constant except for transient phenomena at the time of input, only a small amount of output is generated (FIG. 3f). Therefore, the next stage comparison circuit 7
Since the logic "0" output does not occur except for transient phenomena at the time of input (Fig. 3g), the AND circuit 6-
1, 6-2 output is not prohibited. On the other hand, when there is noise with large level fluctuations over time, the rectifier circuit 3
The input levels of -1 and 3-2 vary and produce an output to the differentiating circuit 5 (FIG. 2f). Therefore, when the next-stage comparison circuit 7 determines that the input is above a certain reference level, it generates a logic "0" output (Fig. 2g), and this output signal
AND circuits 6-1 and 6-2 are prohibited.
NAND circuit 9 generates an output when the outputs of AND circuits 6-1 and 6-2 are present simultaneously (FIGS. 2h and 3h). Delay circuit 10 is NAND
When the output ("0") of the circuit 9 continues for a certain period of time, an output is given to the output terminal 11 (FIG. 2i). In addition,
Figures 2h and 3i and 3i show output signals when the input signal is a noise signal. Therefore, the output of the NAND circuit does not remain "0" for a certain period of time, and "1" (FIG. 2 i) appears at the output terminal 11, and the input signal is detected as a noise signal. When the input signal is a normal signal, the comparison circuits 4-1 and 4
-2 outputs (Fig. 3 b and d become "1" continuously) and the output of the comparator circuit 7 (Fig. 3 g) also becomes "1", thereby the output of the NAND circuit 9 (Fig. 3 h) becomes a continuous "0". As a result, the delay circuit 10 detects that "0" continues for a certain period of time and provides a signal "0" representing signal detection to the output terminal 11 (FIG. 3i).

As described above, since the present invention uses a differentiating circuit, multi-frequency signals can be detected without being affected by noise. Note that it is also possible to provide a differentiator circuit for each rectifier circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 a to i show the operation of the circuit in FIG. 1 when receiving noise, and FIGS. 3 a to i show the operation of the circuit in FIG. FIG. 4 is a waveform chart for explaining the operation of each circuit. In Fig. 1, 2-1, 2-2...wave devices,
3-1, 3-2... Rectifier circuit, 8... Adder circuit,
4-1, 4-2, 7...comparison circuit, 5...differentiation circuit, 6-1, 6-2...AND circuit, 10...delay circuit.

Claims (1)

[Claims] 1. A plurality of wave generators that extract the respective frequencies of a multi-frequency signal including a plurality of frequency signals, and a plurality of wave generators that are provided in one-to-one correspondence with the plurality of wave generators and rectify the outputs of the respective wave generators, respectively. A plurality of rectifier circuits, a plurality of comparator circuits that are provided in one-to-one correspondence with the rectifier circuits and generate an output when the output of each of the rectifier circuits reaches a certain level, and outputs from these comparator circuits. and a differentiation circuit that differentiates the sum of one or two outputs of the plurality of rectifier circuits, and each of the comparison circuits A multi-frequency signal detection method characterized by prohibiting the output of.