JPH0543236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a keying pulse waveform shaping processing device used in a CATV converter.

BACKGROUND OF THE INVENTION A keying signal is a group of pulses containing the information necessary to descramble an image scramble signal. This keying signal is usually input together with the video signal at the head of the video signal. Furthermore, the keying signals include those of positive polarity and those of negative polarity.

FIG. 2 is a block diagram showing the configuration of a conventional keying pulse waveform shaping circuit. In FIG. 2, a keying signal before waveform shaping applied from an input terminal 1 is inputted to an automatic waveform shaping circuit 3 after a capacitor DC component provided in a DC CUT circuit 2 is removed. In automatic waveform shaping circuit 3, DC
A predetermined DC level of the output pulse of the CUT circuit 2 is applied, and at the same time peak hold is performed. The relationship between the DC level and the peak level is as shown in FIG. 3a. Then detect the peak level and DC level,
These level differences are divided, a slice level is determined, and the waveform is shaped into a keying pulse as shown in FIG. 3b.

Problems to be solved by the invention However, with the above conventional configuration,
If a keying signal of positive polarity is input, there is no problem, but if a keying signal of negative polarity is input, as shown in Figure 4a, the DC level and peak level are the same level, so In automatic waveform shaping circuits, there was a problem in that slice levels could not be set and signal processing could not be performed.

In view of the above-mentioned problems, the present invention provides a keying pulse waveform shaping processing device suitable for integration, which can perform waveform shaping on both positive polarity and negative polarity keying signals and output them all with positive polarity. The purpose is to

Means for Solving the Problem In order to achieve this object, the present invention includes a DC CUT circuit that removes the DC component of the input keying signal and sets the DC level to a predetermined level, and slices from the predetermined level and the peak level. First and second waveform shaping circuits that set the level, slice and pulse-shape the input keying signal, and first and second pulses that detect the presence or absence of pulse output from the first and second waveform shaping circuits, respectively. an inverting circuit provided on the input side of the second waveform shaping circuit to invert the level of the input keying signal; and an inverting circuit provided on the input side of the second waveform shaping circuit to determine whether the output signals of the first and second waveform shaping circuits have the first and second pulses. An output circuit that selectively outputs an output based on the output of the circuit is provided to selectively output the output.

Effects With the above configuration, both positive and negative polarity keying signals can be processed by a signal processing system that processes the input keying signal as it is, and a signal processing system that inverts it and processes it, and the output thereof also increases. The input keying signal can be obtained as a pulse signal of positive polarity, making it compatible with transmission systems in which the polarity of the input keying signal is different.

Embodiment Hereinafter, a keying pulse waveform shaping processing device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of the keying pulse waveform shaping processing circuit of this embodiment. Components similar to the conventional configuration shown in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, a keying signal is input from an input terminal 1. The keying signal input to the input terminal 1 is input to the DC CUT circuit 2 and the inverting circuit 6, respectively. The DC component of the keying signal input to the DC CUT circuit 2 is removed, and the keying signal is waveform-shaped by the positive polarity waveform shaping circuit 3. In other words, the pulse width is set to a constant pulse width, and
The DC level is set to a predetermined level and this
A slice level is calculated from the DC level and the peak level, and the input signal is sliced. The output of this positive polarity waveform shaping circuit 3 is input to a positive polarity pulse presence/absence determination circuit 5. In this positive polarity pulse presence determination circuit 5, the positive polarity waveform shaping circuit 3
It is determined whether or not there is a pulse signal in the output. If there is no pulse output, an H level signal is output, and if there is a pulse output, an L level signal is output.

The input keying signal applied to the inverting circuit 6 is inverted with respect to the DC level. When the input keying signal has positive polarity, it becomes negative polarity after passing through this inversion circuit 6. In the inverting circuit 6, the DC component of the signal is removed in the DC CUT circuit 7, and if the input keying is positive polarity, it becomes a negative polarity waveform in the form shown in Fig. 4a, and if it is negative polarity, it becomes a negative polarity waveform in the form shown in Fig. 3a. The signal is input to the shaping circuit 8. In the negative polarity waveform shaping circuit 8,
Similar to the positive polarity waveform shaping circuit 3, level slicing and pulse width setting are performed. If the input signal is
In the case shown in FIG. a, the DC level and the peak level almost match, and the pulses are removed after passing through the waveform shaping circuits 3 and 8. In the negative polarity pulse presence/absence determination circuit 9, in the same way as the positive polarity pulse presence/absence determination circuit 5, the negative polarity waveform shaping circuit 8
It is detected whether or not there is a pulse signal in the output.
The outputs of the waveform shaping circuits 3 and 8 and the pulse presence/absence determining circuits 5 and 9 are input to a pulse output buffer circuit 10. This pulse output buffer circuit 10
outputs the output pulses of the waveform shaping circuits 3 and 8 only in the case where the outputs of the pulse presence determination circuits 5 and 9 are at L level as keying pulse outputs. When the input keying signal is of positive polarity, only the output of the positive polarity waveform shaping circuit 3 is obtained as a keying pulse output, and when the input keying signal is of negative polarity, the output of the negative polarity waveform shaping circuit 8 is obtained as the keying pulse output.

In this way, as the keying signal input, the positive,
No matter which polarity of the negative signal is input, the waveform is shaped and all are output as positive polarity pulses.

As described above, according to this embodiment, a circuit configuration that can easily handle bipolar pulses and is suitable for integration while taking advantage of the features of the existing automatic waveform shaping circuit and pulse presence/absence determination circuit is created. can get.

Effects of the Invention As described above, according to the present invention, by making it possible to perform waveform shaping processing on bipolar pulses, it is possible to perform waveform shaping processing on several types of keying pulses. Its practical effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a keying pulse waveform shaping processing device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional example, and FIGS. 3 and 4 are waveform diagrams illustrating waveform shaping processing. 3, 8... Waveform shaping circuit, 5, 9... Pulse presence/absence determination circuit, 6... Inverting circuit, 10... Pulse output buffer circuit.

Claims (1)

[Claims] 1 Remove the DC component of the input keying signal,
a DC CUT circuit that sets the DC level to a predetermined level; first and second waveform shaping circuits that set a slice level from the predetermined level and the peak level, slice and pulse-shape the input keying signal; 1. First and second pulse presence/absence determination circuits each detecting the presence or absence of a pulse output of the second waveform shaping circuit, and are provided on the input side of the second waveform shaping circuit and invert the level of the input keying signal. and an output circuit that selectively outputs the output signals of the first and second waveform shaping circuits based on the outputs of the first and second pulse presence/absence determination circuits. Keying pulse waveform shaping processing device.