JPH043677A - Data signal demodulator - Google Patents

Abstract

PURPOSE:To demodulate a DPSK signal without being affected by drop out by generating correction data, and synthesizing it with demodulation data when the drop out occurs in the DPSK signal. CONSTITUTION:A drop out detection circuit 26 detects the drop out when it exists in the DPSK signal inputted from a preamplifier 4. When a drop out detection signal is outputted from the drop output detection circuit 26, a D-type flip-flop 27 is triggered, and the level of the output of the flip-flop is inverted. Since the correction data outputted from the D-type flip-flop is synthesized with the output of a demodulation data generation circuit 13 by an exclusive OR gate 28, data outputted from the exclusive OR gate 28 goes to correct data. In such a way, the DPSK signal is demodulated without being affected by the drop out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data signal demodulation device suitable for use in a video floppy playback device.

[Prior Art] FIG. 4 is a block diagram showing the configuration of an example of a conventional data (No. 3 demodulation device) previously proposed by the applicant in Japanese Patent Application No. 1-76324.

A disk 2 rotated by a motor 1 is reproduced by a head 3. The playback signal output from the head 3 is amplified by a preamplifier 4 and passed through a bypass filter (HPF) 5.
, a low pass filter (LPF) 8, a tuning amplifier 10,
Each is input.

Bypass filter 5 separates the FM luminance signal component from the input signal. The FM luminance signal separated by the bypass filter 5 is input to the signal processing circuit 6, demodulated and processed, and then output to the encoder 7. Similarly, the FM color signal separated by the low-pass filter 8 is input to the signal processing circuit 9, demodulated and processed, and output to the encoder 7. The encoder 7 adds the luminance signal and the color signal and outputs the result as a composite video signal to a circuit (not shown).

On the other hand, the tuning amplifier 10 receives DPSK (
It tunes to the g frequency component, separates it, and amplifies it. The output of the tuned amplifier 10 (FIG. 5B) is input to the envelope detection circuit 11, and its envelope is detected. D
For example, when the data changes every 4H, the phase of the PSK signal changes every 4H, as is clear from the comparison with the horizontal synchronization signal (Figure 5A), so its envelope Also changes every 4H. This change point is detected by the change point detection circuit 12. Change point detection circuit 12
The detection output (FIG. 5C) is input to the demodulation data generation circuit 13. The demodulated data generation circuit 13 is composed of, for example, a flip-flop, and is triggered by the output of the change point detection circuit 12. As a result, the demodulated data generation circuit 13 generates DPSK demodulated data (FIG. 5D) whose phase is inverted every time a change point occurs.

The output of the signal processing circuit 6 is input to a sync separation circuit 14, and the sync separation circuit 14 separates a vertical sync signal. The mono-multivibrator 15 is triggered by this vertical synchronization signal and generates a reset pulse. The flip-flops constituting the demodulated data generation circuit 13 are reset by this reset pulse.

[Problem to be Solved by the Invention] In this way, the conventional device detects a changing point in the envelope of a DPSK signal, triggers a flip-flop in response to the changing point, and generates DPSK demodulated data. Ta. As a result, if there was a dropout in the DPSK signal (Fig. 5E), a changing point corresponding to this dropout was detected (Fig. 5F), which caused the problem that erroneous demodulation was performed (Fig. 5F). Figure G).

The present invention has been made in view of this situation, and is intended to enable correct demodulation of DPSK signals without being affected by dropouts.

[Means for Solving the Problems] A data signal demodulation device of the present invention provides DPSK demodulation from an input signal.
A DPSK separation circuit that separates signals, an envelope detection circuit that detects the envelope of the output of the DPSK separation circuit, a change point detection circuit that detects the change point of the output of the envelope detection circuit, and a change point detection circuit that corresponds to the output of the change point detection circuit. Te DP
A demodulation data generation circuit that generates SK4g demodulation data, a dropout detection circuit that detects dropout of DPSK (3), and a correction data generation circuit that generates correction data in response to the output of the dropout detection circuit. and a synthesis circuit that synthesizes the output of the demodulation data generation circuit and the output of the correction data generation circuit.

[Operation] In the data signal demodulator having the above configuration, when dropout occurs in the DPSK signal, correction data is generated and combined with the demodulated data.

Therefore, the DPSK signal can be demodulated without being affected by dropout.

[Embodiment] FIG. 1 is a block diagram showing the configuration of an embodiment of a data signal demodulation device of the present invention, and parts corresponding to those in FIG. 4 are given the same reference numerals and will not be repeated. Therefore, the explanation will be omitted as appropriate.

In this embodiment, the output of the preamplifier 4 is input to the dropout detection circuit 26, dropout is detected, and the D-type flip-flop 27
(The correction data generation circuit is triggered. The output of the flip-flop 27 is combined with the output of the demodulation data generation circuit 13 by the exclusive OR gate 28 (synthesizing circuit). is reset by a reset pulse output from the mono-multivibrator 15.

The other configurations are the same as in FIG. 4.

Next, the operation will be explained with reference to the timing chart of FIG.

As described above, the change point detection circuit 12 detects the change point detection output (the change point detection output) every 4H (FIG. 2A) when a phase change actually occurs in the output of the tuned amplifier 10 (FIG. 2B). Figure 2C
) occurs. This change point detection output is input to the demodulated data generation circuit 13, and demodulated data (FIG. 2D) is generated.

This change point detection output (FIG. 2F) is generated even when a dropout occurs in the DPSK signal (FIG. 2E). As a result, incorrect demodulated data (Fig. 2G
) is generated.

On the other hand, if a dropout exists in the DPSK signal input from the preamplifier 4, the dropout detection circuit 26 detects this. When the dropout detection signal (H in FIG. 2) is output from the dropout detection circuit 26, the D-type flip-flop 27 is triggered and the level of its output is inverted. The correction data output from this D-type flip-flop 27 is combined with the output of the demodulation data generation circuit 13 by the exclusive OR gate 28, so that the data output from the exclusive OR gate 28 (see FIG. )
is correct data.

Next, with reference to FIG. 3, the reproduction operation of DPSK demodulated data will be briefly described.

288th to 32nd H of the first field of the DPSK signal
4H is the initial pit, and the following 328th to 4th
A field or frame identification signal is arranged at 0H, and track numbers are arranged at 408th to 68th H (FIGS. 3A and 3B). For example, in the example shown in Figure 3, the DPSK (No. 328 and 44 of No. g (Figure 3 B)
8, No. 488, No. 568, there are changing points, these changing points are detected (Fig. 3 C), and the waveform is shaped (
Figure 3D). At this point of change, a signal (E, F in FIG. 3) that is inverted to logic H or L can be generated. consecutive 2
The DPSK signal is read by calculating the exclusive OR of the two logics.

[Effects of the Invention] As described above, according to the data signal demodulation device of the present invention,
When a dropout occurs in the DPSK signal, correction data is generated and combined with the demodulated data, so
It becomes possible to demodulate the DPSK signal without being affected by dropout.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the data signal demodulation device of the present invention, FIGS. 2 and 3 are timing charts explaining the operation of the embodiment of FIG. 1, and FIG. 4 is a conventional A block diagram showing the configuration of an example of a data signal demodulation device,
FIG. 5 is a timing chart illustrating the operation of the example shown in FIG. 6.9... Signal processing circuit, 10... Tuning amplifier, 1
DESCRIPTION OF SYMBOLS 1... Envelope detection circuit, 12... Change point detection circuit, 13... Demodulation data generation circuit, 14... Synchronization separation circuit, 26... Dropout detection circuit, 27.
・・D type flip-flop (correction data generation circuit), 2
8...Exclusive OR gate (synthesis circuit). ,・r Patent applicant Asahi Optical Co., Ltd.

Claims (1)

[Scope of Claims] A DPSK separation circuit that separates a DPSK signal from an input signal; an envelope detection circuit that detects an envelope of the output of the DPSK separation circuit; and a change point detection circuit that detects a change point of the output of the envelope detection circuit. a demodulation data generation circuit that generates demodulated data of a DPSK signal in response to the output of the change point detection circuit; a dropout detection circuit that detects a dropout of the DPSK signal; and an output of the dropout detection circuit. A DPSK signal demodulation device comprising: a correction data generation circuit that generates correction data; and a synthesis circuit that synthesizes an output of the demodulation data generation circuit and an output of the correction data generation circuit.