JPS61203760A - Data signal detecting circuit - Google Patents

Abstract

PURPOSE:To detect only a prescribed data signal with less noise by comparing the data signal with 1st comparator discriminating whether or not the data signal exists regardless of the quantity of noise and the 2nd comparator discriminating whether or not noise is much. CONSTITUTION:When a signal with less noise is inputted, an output of the 1st comparator 6 is logical 1 and an output of the 2nd comparator 7 is logical 0, the output of the comparator 7 is inverted by an inverter 8 and becomes logical 1, and two inputs of an AND circuit 9 go both to logical 1, then the level of logical 1 is outputted to a terminal 10. When a signal with much noise is inputted, an output of the comparator 6 goes to logical 1 and an output of the comparator 7 goes to logical 1, and a logical 0 is outputted to the terminal 10. Since the terminal 10 goes to logical 1 only when a prescribed data signal with less noise is inputted and the terminal 10 goes to logical 0 in other cases, only the prescribed data with less noise is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data signal detection circuit, and more particularly to a data signal detection circuit that detects the presence or absence of a data component in a received signal of data communication.

[Conventional technology]

Conventionally, this type of data signal detection circuit relies exclusively on detecting a specific code that has a high autocorrelation peak, that is, a synchronization signal, in the data of the received signal, and detects the data signal. It was intended to detect.

[Problem that the invention seeks to solve]

In the conventional data signal detection circuit described above, when the received electric field strength deteriorates, such as in a wireless communication bag, a lot of noise is mixed into the received signal and the bit error rate worsens. The problem is that there is a high possibility that data will be detected, that is, it will be determined that there is data even when there is no signal.

[Means for solving problems]

Figure 2 shows an example of a data signal of 1200 bit/se.
In the power spectrum of the FF5K signal in a, the solid line shows when there is little noise, and the broken line shows when there is much noise.

The present invention focuses on the fact that a data signal has a unique frequency spectrum depending on the modulation method, etc., and that the frequency spectrum of noise is flat within the band. After passing the peak and valley frequencies through two narrow band pass filters, they are rectified.
Each of the rectified outputs is connected to a first comparator having a reference value for determining whether or not the input data signal is a predetermined data signal regardless of the amount of noise. By comparing the second comparator with a reference value for determining whether the noise is large or small, it is detected that the input signal contains a predetermined data signal with little noise.

That is, the data signal detection circuit of the present invention inputs a signal from an input terminal, an output terminal, and an input terminal, and detects the frequency of the peak part and the frequency of the valley part of the spectrum peculiar to a predetermined data signal to be detected, respectively. First and second narrowband band pass filters to pass through; The first .i2 bandpass filter outputs are rectified. The outputs of the second rectifier circuit and the first rectifier circuit are compared with the first reference value to indicate whether the data signal input from the input terminal is a predetermined data signal regardless of the amount of noise. A first comparator that outputs a logic signal and the output of a second rectifier circuit are compared with a second reference value to generate a logic signal indicating whether there is a lot of noise or little noise in the signal input from the input terminal. Inputs both logic signals of the second output comparator and the first and second comparators to determine whether or not the signal input to the input terminal contains a predetermined data signal with less noise. The device includes a gate circuit that outputs a discrimination signal to an output terminal.

〔Example〕

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

FIG. 1 is a block diagram of an embodiment of a data signal detection circuit according to the present invention.
Note that the FF5K signal of it/sec is detected.

The data signal detection circuit of this embodiment has input terminal 1, output terminal IO, and a spectrum (Fig. 2) peculiar to a predetermined data signal (FF5K signal of 1200 bits/+ec) among the signals inputted from input terminal 1. The frequency of the peak of
That is, a narrow-band first band-pass filter 2 that passes 1500Hz±25H2, and a narrow-band second band-pass filter 3 that passes the frequency at the valley part of the spectrum, that is, 2400Hz±25H2 (1 in FIG.
1.12 are the first and second bandpass filters 2, respectively.
．． 3), a first and second rectifier circuit 4.5 that converts the average value of the respective output signals of these bandpass filters 2 and 3 into direct current, and these rectifier circuits 4.
5, -1Qdg, -2
The inverter 8 inverts the output signal of the comparator 7 of the first and second comparators 6.7 and 1w42, which outputs a logic value "l" when the voltage is equal to or higher than Qdg, and the output signal of the first comparator 6. It consists of an AND circuit 9 which takes the AND of the output signal of the inverter 8 and outputs it to the output terminal 10.

Next, the operation of this embodiment will be explained.

(1) Assume that a predetermined data signal with little noise is now input. The output of the first comparator 6 is a logical value "1",
The output of the second comparator 7 becomes the logic value "O", the output of the second comparator 7 is inverted by the inverter 8 and becomes 1", and the two inputs of the AND circuit 9 both become the logic value '"t.
”, the logical value °“l” is output to the output terminal 10.

(2) Next, assume that a predetermined data signal with a lot of noise is input. The output of the first comparator 6 becomes a logic value "1", and the output of the second comparator 7 also becomes a logic value "L", but the output of the comparator 7 of $2 is inverted by the inverter 8 and becomes a logic value. °
°O'', and one of the inputs of the AND circuit 9 has the logical value N.
I II The other becomes the logical value II O", so the output terminal 1
Logic value "o" is output for 0.

(3) If the next data signal is not input, the first
The output of comparator 6 becomes the logical value ``O''.

Regardless of the amount of noise, the logical value of the output of the AND circuit 9 is °'
It becomes O”.

The following table summarizes the above.

That is, the logical value "l" is output to the output terminal 10 only when a predetermined data signal with little noise is input.
In other cases, the logical value "O" is output, so that only a predetermined data signal with less noise is detected.

In this embodiment, the second bandpass filter passes the frequencies in the valleys with higher frequencies, but may pass the valleys with lower frequencies.

〔Effect of the invention〕

As explained above, the present invention converts the characteristics of the frequency spectrum of an input data signal into f-waves using a plurality of narrow band bandpass filters, and converts these into whether there is a data signal or not, regardless of the amount of noise. A first comparator determines whether the noise is high or low, and a second comparator determines whether the noise is high or low. By comparing the data, it is detected that the input signal contains a data signal with low noise. This has the effect of eliminating erroneous detection of fictitious data signals due to noise.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the data signal detection circuit of the present invention, FIG. 2 is a graph showing an example of the frequency spectrum of a data signal, and FIG. 3 is a diagram showing each bandpass filter 2 of FIG. It is a graph showing the frequency characteristics of .3. l...input terminal, 2...first band pass filter, 3...second band pass filter, 4...first rectifier circuit, 5...second rectifier circuit,
6... First comparator, 7... Second comparator. 8...Inverter, 9...AND circuit. 10... Output terminal.

Claims (1)

[Claims] An input terminal, an output terminal, and a narrow band that receives a signal from the input terminal and passes frequencies at peaks and valleys of a spectrum specific to a predetermined data signal to be detected. first and second band pass filters, first and second rectifier circuits that rectify the outputs of the first and second band pass filters, respectively, and rectifiers that rectify the output of the first rectifier circuit, respectively. Compare with the standard value,
a first comparator that outputs a logic signal indicating whether the data signal input from the input terminal is a predetermined data signal regardless of the amount of noise; a second comparator that outputs a logic signal indicating whether the noise contained in the signal input from the input terminal is large or small by comparison with a reference value; and both logics of the first and second comparators. Data signal detection comprising a gate circuit that inputs a signal and outputs a determination signal to the output terminal for determining whether or not the signal input to the input terminal includes a predetermined data signal with little noise. circuit.