JPS6283671A - Signal detection circuit - Google Patents

Abstract

PURPOSE:To enable the detection of an information signal without generating phase variation even when the envelope of a regeneration signal changes, by leading out comparing voltage by the envelope detection of peak voltages in the positive and negative directions of an input signal. CONSTITUTION:A regeneration signal V1 is inputted to a comparator 1 and an envelope detection circuit 16. In the circuit 16, the signal V1 is inputted to a positive direction peak voltage circuit consisting of a diode D1, a condenser C1 and a buffer amplifier 7 and a negative direction peak voltage detection circuit consisting of a diode D2, a condenser C2 and an amplifier 10 through a buffer amplifier 4 and respectively detected peak voltages V<+>p, V<->p in positive and negative directions show only the envelope of the regeneration signal. These voltages are added by an adder 14 and subsequently averaged through LPF15 to be supplied to the comparator 1 as comparing voltage. Therefore, an information signal is detected by the signal showing the center of the envelope and signal detection having no relation to phase variation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a signal detection circuit for detecting an information signal from an input signal, and is used in, for example, a magneto-optical disk memory device.

(Prior Art) A signal detection circuit in a magneto-optical disk memory device will be described as an example.

First, the reproduction principle of the magneto-optical disk memory device will be explained below.

When linearly polarized light is irradiated onto a magneto-optical disk on which information is recorded, the reflected light is affected by the magnetic film and the plane of polarization tilts. Reproduction is performed by changing this inclination to the intensity of light and detecting it with a photodetector.

FIG. 4 shows an example of the envelope of a reproduced signal obtained by removing a DC component from a signal detected by a photodetector using a bypass filter. As can be seen from FIG. 4, the envelope of the reproduced signal from the magneto-optical disk changes. The main reason for the change in the envelope is the transient response due to the bypass filter,
Examples include changes in DC components due to modulation of information signals and non-uniformity of the recording film of the disk.

Next, FIG. 5 shows an example of conventional zero-cross detection performed in a signal detection circuit that detects an information signal from the reproduced signal v1. In FIG. 5, the second signal V, is input to one input terminal of comparator a, and the other input terminal C
is a constant voltage V. The voltage divided by resistor R4 and resistor R9 ■
, is input. In this comparator a, the reproduced signal V1
are compared based on this comparison voltage V B 1, and an information signal (■) is obtained. 1 can be detected.

(Problems to be Solved by the Invention) However, in this type of signal detection circuit, phase fluctuation occurs in the detected information signal VOI. That is, at the input signal (1) of the comparator a and the comparison voltage Vll shown in FIG. 6, the reproduction signal (2) is generated. The information signal V detected because the envelope line of V changes. + (see FIG. 7) phase fluctuation occurs, making it impossible to detect a good information signal.

(Means for Solving the Problems) The present invention includes positive-direction peak voltage detection means for detecting and holding the positive-direction peak voltage of an input signal, and positive-direction peak voltage detection means for detecting and holding the negative-direction peak voltage of the input signal. and means for obtaining a comparison voltage in a comparator from envelope detection signals obtained by the positive and negative direction peak voltage detection means.

(Function) Based on the two peak voltages detected by the peak voltage detection means in the iIE direction and the peak voltage detection means in the negative direction, the comparison voltage in the comparator is made to follow the envelope 7;I( of the signal).

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

21) FIG. 1 shows the signal detection circuit according to the present invention, FIG. 2 shows the signal waveform at each point in FIG. 1, and FIG. 3 shows the waveform of the information signal detected in FIG. 1.

In FIG. 1, a reproduced signal (1) is input to a comparator 1 and an envelope detection circuit 16. In the envelope detection circuit 1,
Reproduction signal 1 is transmitted through a buffer amplifier 4 to a positive direction peak voltage detection circuit consisting of a diode D, a capacitor CI, and a buffer amplifier 7, and a negative direction peak voltage detection circuit consisting of a diode D2, a capacitor C2, and a Hanofa amplifier 10. Input to the detection circuit. The positive peak voltage V2' obtained by the positive peak voltage detection circuit and the negative peak voltage p- obtained by the negative peak voltage detection circuit are obtained by detecting only the envelope of the reproduced signal. There is. Then, these positive direction peak voltage Vp+ and negative direction V, -
is input to an adder composed of resistors R+, Rt, Rz and an operational amplifier 14.

At this time, the relationship among the resistors R+, Rz, and R:l is R+ = Rz = R3 in this example, and the output vbz of the adder is
" +Vp-) / 2. In other words, ■b□ is a signal intermediate between the positive direction peak voltage ■2゛ and the negative direction peak voltage ■p-. This vbz is passed through a low-pass filter (L P F ) 15 is equal to the center of the envelope of the reproduced signal. This Vat, which is the output of the envelope detection circuit 16, is equal to the (-
) input terminals and is compared with the reproduced signal ■1 inputted to (+) input terminals, resulting in an information signal ■. 2 (see FIG. 3) is detected.

As described above, if the center of the envelope of a reproduced signal with changes in the envelope is detected and the comparator detects the information signal based on this signal, phase fluctuations can be suppressed and good signal detection can be achieved. .

Furthermore, the signal detection circuit of the present invention can be applied not only to the above-mentioned magneto-optical disk memory device, but also to optical disk memory devices and other recording/reproducing devices, as long as it detects a signal accompanied by a change in envelope. It is.

In addition, according to the present invention, N
Not only the detection of information signals such as RZ recording and NRZI recording, but also the reproduction of detection density for signal detection, it is not necessary to set the center of the envelope as the comparison voltage, and it is not necessary to set the center of the envelope as the comparison voltage. A comparison voltage can be obtained based on the signal.

(Effect of Determination) As described above, the present invention provides a signal detection circuit capable of detecting information No. 13- in which phase fluctuation does not occur even if the envelope of the reproduced signal changes. be able to.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the signal detection circuit according to the present invention, FIG. 2 is a waveform diagram at each point in FIG. 1, and FIG. 3 is a waveform diagram of the information signal detected in FIG. 1. FIG. 4 is a diagram showing an example of the envelope of a reproduced signal in a magneto-optical disk memory device, FIG. 5 is a circuit diagram showing a conventional signal detection circuit, and FIG.
The figure is a waveform diagram at each point in FIG. 5, and FIG. 7 is a waveform diagram of the information signal detected in FIG. 1...Comparator 4...Buffer amplifier 7
, Buffer amplifier 14... Operational amplifier 15... Low-pass filter 16... Envelope detection circuit Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1) Positive-direction peak voltage detection means for detecting and holding the positive-direction peak voltage of an input signal; and negative-direction peak voltage detecting and holding the negative-direction peak voltage of the input signal. A signal detection circuit comprising: a detection means; and a means for obtaining a comparison voltage in a comparator from an envelope detection signal obtained by the positive direction and negative direction peak voltage detection means.