JPS58161536A - Signal detector - Google Patents

Abstract

PURPOSE:To improve the noise margin, by generating automatically the reference voltage of a voltage comparator in the form of a function of the signal voltage applied to an input circuit and the noise voltage. CONSTITUTION:For the input voltage Ei, the voltage ei having improved S/N is applied to a voltage comparator 8 through a BPF7. At the same time, the voltage of the band where only the noise of voltage Ei is extracted by a BPF1. Then the DC voltage en which is proportional to the extracted noise voltage is delivered through an envelope curve detector 2 and an LPF3. While the voltage (ei) is attenuated by an attenuating circuit 5 which alpha-multiplies the voltage (ei). Then beta is set so as to satisfy alphaei>betaen when a signal exists for a DC amplifying circuit 4 which beta-multiplies the voltage (en). A switch circuit 6 switches and delivers the larger one of alphaei and betaen. The output voltage of the circuit 6 is used to the reference voltage eR of the comparator 8. As a result, the comparator 8 decides the presence of signal if a signal exists to the voltage ei. While the comparator 8 decides the absence of signal if no signal exists to the voltage ei.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal detection device in which a reference voltage of a voltage comparator is formed from an input voltage to improve noise margin.

Conventionally, the reference voltage of a voltage comparator is a fixed DC voltage that does not change even when the input voltage of the voltage comparator changes. Therefore, if the amplitude of the signal voltage and noise voltage applied to the voltage comparator fluctuates, 1
This has the disadvantage that the noise margin for 1-voltage comparison becomes smaller.

An object of the present invention is to eliminate such drawbacks, to automatically generate a reference voltage for a voltage comparator as a function of the signal voltage and noise voltage applied to the input circuit, and to improve the noise margin. An object of the present invention is to provide a signal detection device.

The signal detection device of the present invention includes a first p-wave device that passes a predetermined signal frequency band of the input signal, an attenuator that provides a predetermined attenuation to the output of the first F-wave device, and a first p-wave device that passes a predetermined signal frequency band of the input signal. A second filter that passes noise in a predetermined frequency band that does not exist, a noise detection circuit that detects the noise output of the second filter and extracts a DC noise voltage, and an output of the noise detection circuit. an amplifier that amplifies the voltage so that it becomes larger than the output of the attenuator when there is no input signal; a switching circuit that compares the output of this amplifier with the output of the attenuator to take out a larger output; and this switching circuit. and a voltage comparator that compares the output of the first F-wave device using the output of the circuit as a reference voltage.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a detailed diagram of this embodiment.

In the figure, the input voltage Ei, in which the signal voltage and the noise voltage are superimposed, passes through a bandpass filter 7 to cut off the noise in the band where no signal voltage exists, resulting in an improved voltage ei of 87N.
is applied as the input voltage of the voltage comparator 8. The noise voltage in the input voltage Bi is distributed over a wide band as shown in the spectrum 12 shown in the spectrum diagram of FIG. 2, and the signal voltage is distributed within a limited round band as shown in the spectrum 11. For this reason, the voltage in a band where only noise exists, such as region 13, is extracted by a bandpass detector l, and the DC voltage e11 proportional to the extracted noise voltage is detected by an envelope detector 2. The low-frequency F-wave generator 3 is used to perform the calculation.

The amount of variation in the width of the voltage em is proportional to the amount of variation in the noise voltage n included in the signal voltage ei. This signal voltage et is attenuated by an attenuation circuit 5 which multiplies it by α, and α is set to a value of 1 or less. On the other hand, in the DC amplifier circuit 4 that multiplies the DC voltage em by 1, the output βC11 becomes 9 when the value is larger than the peak value of the noise voltage included in the voltage ek, and αei) 10m when there is a signal. Set β as follows. (9) The switching circuit 6 switches and outputs the larger voltage value between αei and 16m. The voltage gain of this switching circuit 6 is assumed to be 1. The output voltage of this switching circuit 6 is used as the voltage comparator 80 reference voltage e1.

With such a configuration, when a signal exists at voltage at, the reference voltage axis becomes eB:αei, and ei
) αei Therefore, the voltage comparator 8t2
It is determined that there is a signal. When there is no signal at this voltage ei, the reference voltage eH is eR=βθ.

Since the relationship is ei<βen, the voltage comparator 8
It is determined that there is no signal.

As explained above, since the reference voltage of the voltage comparator changes in proportion to the input signal voltage and the input noise voltage, it is effective in signal detection when the input signal voltage fluctuates greatly.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a spectrum distribution diagram in FIG. 1. In fig. 1...Band-pass F-wave device that extracts only noise voltage from a frequency band where no signal voltage exists%2...
Envelope detector, 3...Low frequency F wave detector, 4...
··amplifier. 5...Attenuator, 6...Voltage gain 1 switching circuit, 7...Pass band interrupter, 8...
・Voltage comparator, 11...Signal spectrum, 1
2...Noise spectrum. 13...This is the passage area of the F-wave device 1. Figure 1 3 Village map 2

Claims (1)

[Claims] A first filter that passes a predetermined signal frequency band of the input signal.
an attenuator that provides predetermined attenuation to the output of the first F-wave generator; a second P-wave generator that passes noise in a predetermined frequency band in which the predetermined signal does not exist; a noise detection circuit that detects the noise output of the filter and outputs a DC noise voltage; and an amplifier that amplifies the output voltage of the noise detection circuit so that it becomes larger than the output of the attenuator when there is no input signal. a switching circuit that compares the output of the amplifier with the output of the attenuator to obtain a larger output; and a voltage comparator that compares the output of the first waveform generator using the output of the switching circuit as a reference voltage. and a signal detection device.