JPH04122152A - Tone signal detection circuit - Google Patents

Abstract

PURPOSE:To prevent malfunction due to noise by disabling a tone signal even when a combination circuit detects the tone signal and a non-signal detection circuit detects a non-signal. CONSTITUTION:A sampling conversion circuit 2 applies A/D conversion of 2's complement indication to a sampled signal. A small amplitude detection circuit 10 discriminates it to be a small amplitude that when plural high-order bits of an output of an A/D converter 9 in 2's complement indication are all is or 0s and outputs '0' when the amplitude is small. A non-signal detection circuit 13 detects it to be a non-signal when three newest time series of an output of the small amplitude detection circuit 10 are all discriminated to be small amplitude signals and outputs a '0' signal to an AND circuit 15. Thus, the AND circuit 15 disables a tone signal even when the combination circuit 4 detects the tone signal and the non-signal detection circuit 13 detects a non- signal. Thus, malfunction is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal detection circuit, and particularly to a tone signal detection circuit.

[Conventional technology]

Conventionally, tone signal detection circuits have been used for various purposes, but their basic configuration has been a circuit using an analog resonant circuit and a circuit using a digital signal processing processor. On the other hand, with recent advances in L8I technology, systems on the chip are being realized, and the miniaturization of circuits and devices is progressing rapidly. Therefore, tone signal detection circuits are also being miniaturized using this LSI technology.

[Problem to be solved by the invention]

In the nine conventional tone signal detection circuits mentioned above, especially those using analog resonant circuits, the external attachment of the LSI for the resonant circuit generates parts, and even if the resonant circuit can be realized inside the LSI, Since it is an analog LSI, it cannot benefit from the more advanced miniaturization technology of digital LSI, and it is difficult to miniaturize the -layer. (9) Although circuits using digital signal processing processors can benefit from digital LSI miniaturization technology, they require a processor with a minimum number of kilogates, making it difficult to further miniaturize the circuit on an LSI. There is.

[Means to solve the problem]

The tone signal detection circuit according to the present invention samples the tone signal at a sampling rate that is Nf times higher than its frequency f (where N is a natural number), identifies the polarity of the amplitude, and creates a time series of the polarity of the sampling signal. The sampling/conversion circuit and the latest values of this time series are
Assuming that the polarity time series of tone signals of various phases in N ways are stored in the M latest values, there is a storage circuit that stores only 7'hN polarity patterns (M is a natural number). When the combinational circuit compares the polarity pattern with the polarity pattern and logically ORs the result for N comparisons, and the upper bits of the output of the sampling/conversion circuit mentioned above are all “1” or “0”. , a small amplitude detection circuit that determines that the amplitude is small, and detects that there is no signal when all the time series of the latest output of this small amplitude detection circuit (where ■ is a natural number) have small amplitudes. The apparatus includes a no-signal detection circuit and means for disabling the tone signal when the combinational circuit detects a tone signal and the no-signal detection circuit detects no signal.

[Effect]

The present invention is suitable for digital LSIs, and can realize further miniaturization on LSIs, and can also prevent malfunctions due to minute amplitude crosstalk.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a tone signal detection circuit according to the present invention. In the same figure, 1 is the input terminal, 2 is N of the frequency f of the tone signal considered as the input signal.
3 is a sampling/conversion circuit consisting of a sampling circuit that performs double sampling and a conversion circuit that identifies the polarity of this sampled signal and creates a time series of the polarity of the sampling signal; 3 stores M latest values of this time series; Normal A
//A storage circuit in which a D converter is used, 4 is a polarity pattern that assumes that the polarity time series of tone signals of various phases of N times are stored and is actually stored. A combinational circuit performs a comparison with a uniformity pattern and performs a logical OR operation on the N ratios. Reference numeral 5 represents a determination circuit that determines the presence or absence of a tone signal.

Note that the polar pattern of NAr is a multiple of Ni2, N=
Constructed as M, N/2-1 positive polarity (hereinafter referred to as "+"), 1 polarity undefined (hereinafter referred to as "x"), N/2
-1 bond with negative polarity (hereinafter referred to as "-"), and one undefined polarity "x" arranged in this order.
This is a pattern that was repeated.

Next, in order to briefly explain the operation of the tone signal detection circuit having the above configuration, the circuit configuration in the case of N=M=6 is shown in FIG. Figures 3(,) to 3() show the polarity time series of
f). In the combinational circuit 4 shown in FIG.
6&~6f are inverter circuits, 71~7f are AND circuits, and 8 is an OR circuit. And the above AND circuit 7a
Fi The phase polarity pattern shown in Figure 3 (, ) is ``+++-
--J, AND circuit 1b has a polarity pattern with the phase shown in FIG. 3(b) [-+++--J, AND circuit 7c has a polarity pattern r--+++-J with the phase shown in FIG.
The AND circuit 7d has the phase polarity pattern shown in FIG. Figure 3 (f) Polar pattern of phase shown in K “++-
−−+” is input, a “1” signal is output.

Therefore, for example, at a certain point in time, the storage circuit 3 as shown in FIG.
Assuming that a polar pattern "+++--J" shown by &)K is stored, the AND circuit 7 of the combinational circuit 4 performs a logical product and outputs a "1" signal.

At this time, if the zero crossing point of the tone signal is close, the stored pattern may not match any of the polarity patterns due to the influence of noise, but if the positive polarity is "+"
When transitioning from to negative polarity "-" and from negative polarity "-" to positive polarity "+", one piece is missing, and the polarity is undefined "×"
Insert it to guard against noise during Serocross. and,
Next, when the sampling data is imported, the waveform and polarity pattern are as shown in Figure 3(b).
Since it changes to J, the AND circuit 7b performs a logical product,
Outputs a “1” signal. Therefore, if the tone signal is continuous, its waveform and polar pattern are as shown in Figure 3 (
C) → Figure 3 (d) → Figure 3 (@) → changes as shown in Figure 3 (f). Therefore, the combinational circuit 4 has N=6
By checking whether the polarity detection pattern of the normal phase matches the actually stored polarity pattern, in the case of a tone signal, one of the polarity patterns shown in FIGS. 3(a) to 3(f)K is detected. There is always one match, and the ones that match each other will shift, so if you OR the results with the polar patterns shown in Figures 3(,) to 3(f), you can determine the tone signal. can be detected.

FIG. 4 is a block diagram showing another embodiment of the tone signal detection circuit shown in FIG. This is to prevent the possibility that tones may also be detected. In the same figure,
9 is an A/D converter that samples and performs A/D conversion in two's complement representation for good signals; 10 is composed of an AND circuit 11 and NOR circuits 12m and 12b;
A small amplitude detection circuit 13 determines that the amplitude is small when the upper bits of the output of the A/D converter 9 are all "1" or "0", and 13 is the small amplitude detection circuit 10. When all of the latest l time series outputs (where I is a natural number and I=3 in this example) have small amplitudes (in this example, rOJ is output when the amplitude is small), no A no-signal detection circuit 15 is an AND circuit that takes the logical product of the output of the combinational circuit 4 and the output of this no-signal detection circuit 13, and the combinational circuit 4 detects a tone signal. However, when the output of the no-signal detection circuit 13 is no signal, this tone signal can be disabled.

In addition, in this Figure 4, N=M=6, I=N/2=3, where I=3 is the half period of the tone signal, and includes the amplitude of the part close to the positive or negative peak amplitude. In rounding, it is essentially determined whether this peak amplitude exceeds a certain level or not.

(9) The number of high-order bits handled by the small amplitude circuit 10 is set so that the threshold value is between the lowest tone level and the tone level due to crosstalk.

Next, the operation of the tone signal detection circuit having the above configuration will be explained. First, the sampling/conversion circuit 2 performs A/D conversion on the sampled signal in two's complement representation. And the small amplitude detection circuit to? r2J with i
When the high-order bits of the output of the A/D converter 9, which are expressed as the complement of . Then, the no-signal detection circuit 13 is connected to this small amplitude detection circuit 1.
When all the latest three (I=3) time series of 0 output have small amplitude, it detects that there is no signal and outputs "0".
The signal is output to the AND circuit 15. Therefore, even if the combinational circuit 4 detects a tone signal, the AND circuit 15 can disable the tone signal when the no-signal detection circuit 13 detects no signal.

In the above embodiment, a sine wave tone signal has been described, but the present invention is not limited to this, and it goes without saying that a rectangular wave tone signal can also be detected in the same manner.

〔Effect of the invention〕

As described above in detail, 1. According to the tone signal detection circuit according to the present invention, the processor can be configured with several tens of gates, so it can be easily configured and miniaturized. Moreover, there is an effect 28 such that a signal that is not a tone is not determined to be a tone, and malfunctions due to noise can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the tone signal detection circuit according to the present invention, FIG. 2 is a block diagram showing an embodiment of the tone signal detection circuit shown in FIG. 1 when N=M=6, 3(a) to 3(f) are diagrams showing waveforms and polar patterns for explaining the operation of FIG. 2, and FIG. 4Fi is another embodiment of the tone signal detection circuit shown in FIG. 2. FIG. 1--Input terminal, 2--Sampling/conversion circuit, 3--Storage circuit, 4--Combination circuit, 5--
... Judgment circuit, 6th to 6f ... Inverter circuit, 7a to 7f -- Reference AND circuit, 8@-... OR circuit, 9... A/D converter, 1G...・Small amplitude detection circuit, 11...AND circuit, 12m> and 12b
・-・Noor circuit, 13 ・・No-signal detection circuit, 14
...OR circuit, 15...AND circuit.

Claims (1)

[Claims] A sampling and conversion circuit that samples a tone signal at a sampling rate Nf times higher than its frequency f (where N is a natural number), identifies the polarity of the amplitude, and creates a time series of the polarity of the sampled signal; A storage circuit that stores M latest values (M is a natural number);
It is assumed that the polarity time series of tone signals of various phases are stored in the M latest values, and the N-way polarity patterns are compared with the actually stored polarity patterns. A combinational circuit that performs a logical OR on the comparison; a small amplitude detection circuit that determines that the amplitude is small when all the upper bits of the output of the sampling/conversion circuit are "1" or "0"; A no-signal detection circuit detects no signal when all of the latest I (I is a natural number) time series outputs of the amplitude detection circuit have small amplitudes, and the combination circuit detects a tone signal. and means for disabling the tone signal when the no-signal detection circuit detects no signal.