JPH04291520A - Signal processing unit - Google Patents

Abstract

PURPOSE:To enhance the waveform reproducibility without reducing an emphasis quantity by providing a preshoot and an overshoot to the waveform. CONSTITUTION:An input signal is inputted to a transmission circuit 2 whose transfer characteristic is G, and its output has a waveform having an overshoot when the circuit 2 is an emphasis circuit and is distributed into two series, and they are inputted to storage means 3, 5. An input signal to the means 3 is read in a reverse time series to a time series at the storage and inputted to a transmission circuit 4 whose transfer characteristic is G. Thus, an overshoot and a preshoot are formed to both leading and trailing edges. Furthermore, the input signal to the means 5 is stored with a delay by only M/2 from a timing stored in the means 3 and the time axis is inverted for each period M. A switch 7 selects an output signal of the circuit 4 or 6 and the selected signal is outputted. Moreover, an emphasis waveform having a preshoot and an overshoot with respect to the input signal is obtained by inverting the time axis for each period M at a storage means 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus for processing the frequency characteristics of an input signal such as a video signal or an audio signal.

0002

[Prior Art] In video tape recorders and the like that record and reproduce video signals, in a frequency modulation/demodulation system, if the noise on the FM transmission line is white noise, the noise added to the demodulated signal will increase in noise level as the frequency increases. It exhibits an increasing so-called triangular noise characteristic. In order to alleviate this, the level of the medium and high range of the input signal is increased before frequency modulation (so-called emphasis is applied to increase the frequency deviation width), and the level of the medium and high range is increased after frequency demodulation. Signal processing is performed to lower the signal (so-called de-emphasis). However, since the band of the FM transmission line is limited by the electromagnetic conversion system, there is a limit to the increase in frequency deviation width due to the amount of emphasis, which causes the problem of limiting the S/N ratio of the reproduced signal. Ta. Note that this problem occurs not only in video tape recorders but also in all systems in which video signals are frequency modulated and transmitted, such as satellite broadcasting.

FIG. 6 shows a conventional emphasis circuit. In FIG. 6, the video signal applied to the input terminal 10 is subjected to emphasis processing and output to the output terminal 14. The conventional emphasis circuit in (Fig. 6) includes a capacitor 11 (capacitance value C), a resistor 12 (resistance value Rb), and a resistor 13.
(resistance value Ra). In a circuit like this (
When a signal as shown in a of FIG. 7 is input, a signal as shown in b of FIG. 7 is obtained at the output terminal 14. In the case of a video tape recorder, the signal shown in b in Figure 7 is frequency-modulated and recorded on a magnetic tape, but because the frequency band of the electromagnetic conversion system that is the FM transmission line is limited ( ) is clipped and frequency modulated at the levels shown by broken lines S1 and S2 in b. For this reason, there is a problem that the frequency demodulated signal causes waveform distortion, and in order to avoid clipping, the emphasis amount (Ra + Rb) / Ra
If is set to 1/2, the effect of emphasis becomes 1/2,
There was a problem in that the SN ratio of the reproduced signal decreased accordingly.

0004

These problems are significant in all systems involving frequency modulation in signal transmission. In other words, when the amount of emphasis for improving SN in frequency modulation is increased, the waveform reproducibility deteriorates due to clipping, and when the amount of emphasis is decreased to improve the waveform reproducibility, the amount of SN improvement also decreases. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a signal processing device that eliminates the above-mentioned drawbacks, uses a sufficient amount of emphasis, and obtains good waveform reproducibility.

[0006]

[Means for Solving the Problems] In order to solve the above problems, a signal processing device of the present invention provides a first signal processing device having a transfer characteristic of G.
and a transmission circuit connected to the first transmission circuit, having a storage capacity for a period M that is at least twice the impulse response duration α of the first transmission circuit, and storing an input signal for each period M. The first step is to output sequentially the reverse time series and the reverse time series.
a second transmission circuit having a transfer characteristic G connected to the output of the first storage means; a second transmission circuit connected to the first transmission circuit and having a storage capacity of a period M; a second storage means that has a time delay from the period α to the period (M−α) than the storage means and sequentially outputs the input signal for each period M in a time series opposite to the stored time series; a third transmission circuit having a transfer characteristic G connected to the output of the storage means; a switch for switching the output signals of the second and third transmission circuits so that the signals within each period M are not dropped; The third storage means has a storage capacity of M and sequentially outputs the output signals of the switches in a time series opposite to the time series stored in each switching period.

[0007]

[Operation] By adopting the above-mentioned configuration of the present invention, the conventional problems can be solved without significantly increasing the circuit scale, and if the same FM transmission path is used, the same frequency deviation width as the conventional one can be achieved. Enables use of more emphasis than before. Alternatively, it is possible to realize a signal processing device in which the peak of the waveform is significantly lower than that of the conventional one with the same amount of emphasis as the conventional one. Furthermore, it is possible to provide a signal processing device having arbitrary transfer characteristics with preshoot and overshoot. Furthermore, it is possible to compensate for the phase characteristics of the transmission circuit and make the phase change of the processed signal zero in real time.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a signal processing apparatus according to the present invention will be described below with reference to the drawings. (FIG. 1) is a block diagram showing an example of a signal processing device of the present invention. Moreover, (FIG. 2) to (FIG. 5) are waveform diagrams showing signal waveforms of each part of the signal processing device of (FIG. 1).

In FIG. 1, 1 is an input terminal, 2 is a first transmission circuit having a transfer characteristic G, and 3 is a storage capacity for a period M that is at least twice the impulse response duration α of the transmission circuit 2. 4, storage means for storing a period M that is at least twice as long as the impulse response duration α of the transmission circuit 2; It has a capacity, has a time delay from period α to period (M-α) than the first storage means, and has a period M
4 and 5 are the first transmission circuit 2; 4 and 5 are the first transmission circuit 2;
7 is a second transmission circuit having the same transfer characteristic as M.
A switch 8 switches the output signals of the transmission circuits 4 and 5 so that the signals in the transmission circuits 4 and 5 are not lost, and 8 is a storage means for sequentially outputting the output signals of the switch 7 in a time series opposite to the time series stored in each switching period. It is.

The signal input to the first transmission circuit 2 is input to the first transmission circuit 2 whose transmission characteristic is G. For example, a signal as shown in a in FIG. 2 is input to the input terminal 1. The output signal of the first transmission circuit 2 has a waveform with an overshoot if the first transmission circuit 2 is an emphasis circuit, as shown in b of FIG. 2. Here, the first transmission circuit 2
Let α be the impulse response duration of . Also (Figure 2)
In the above, each period such as t0 to t1, t1 to t2, t2 to t3, etc. is set to be at least longer than the period α. The signal that has passed through the first transmission circuit 2 is divided into two streams and input into the first storage means 3 and the second storage means 5. The signal input to the first storage means 3 is transmitted during periods t0 to t2 and t2 to t2.
After being stored every t4, it is read out in the reverse chronological order to the stored chronological order. A waveform diagram is shown in a of FIG. 3. The signal whose time axis has been reversed is input to the second transmission circuit 4 having the same transmission characteristics as the first transmission circuit. That is, as shown in FIG. 3b, overshoots and preshoots are formed at both the rising and falling edges. Furthermore, the signal input to the first storage means 5 is stored with a delay of M/2 from the timing at which it is stored in the first storage means 3, and the time axis is reversed every period M. That is, it is processed every period t1 to t3 and t3 to t5. The waveform diagram is shown in (FIG. 4) b. The switch 7 is activated during the period t1~
t2, t3-t4, t5-t6 are the output signals of the transmission circuit 4, and t2-t3, t4-t5, t6-t7 are the output signals of the transmission circuit 6.
Select and output the output signal. The signal thus obtained has a waveform as shown in (a) of FIG. 5. Furthermore, by reversing the time axis every period M in the second storage means 8 (FIG. 5), the waveform shown in b is obtained. (FIG. 5) b shows that an emphasis waveform having preshoot and overshoot is obtained for the input signal. Here, since the emphasis preshoot and overshoot do not affect either the clip levels S1 or S2, no distortion occurs in the reproduced waveform after FM demodulation.

[0011] In the above description, the process of reversing the time axis every period M is performed within the same period, but the process may be performed with a delay of M.

Furthermore, in the above explanation, the difference between the processing periods of the first storage means and the second storage means is M/2, but the difference between the transmission circuit impulse response duration α and the period (M-α) Similar results can be obtained with time. Also,
The switching timing of the switch is also M/2,
The output signals of the transmission circuits 4 and 5 may be switched at a timing such that the signals within the period M are not dropped.

[0013]

As described above, according to the signal processing device of the present invention, a signal is passed through a transmission circuit in a positive time series once, and then passed through a transmission circuit having the same transfer characteristics in a reverse time series. This output has the effect of making the phase characteristic of the transmission circuit zero phase, and is particularly useful for video signals. In addition, when processing continuous signals in sections, processing is performed over a period that is at least twice the duration α of the impulse response of the transmission circuit, so unnecessary waveform changes that occur in discontinuous portions of the signal can be avoided. Can be done. Furthermore, by performing the above processing in two series, it is possible to perform the task of dividing a continuous signal into segmented signals, processing them, and then outputting them again as continuous signals in real time.

Furthermore, as described above, when the signal processing device of the present invention is used as an emphasis circuit in a frequency modulation/demodulation system, by giving the waveform a preshoot and an overshoot, it can have the same amount of emphasis as the conventional one. ,
It is also possible to realize an emphasis circuit in which the peak value of the waveform is lower than before, without reducing the amount of emphasis.
This has the effect of significantly reducing the frequency deviation width compared to the conventional method. Alternatively, it is possible to add more emphasis than before, and it is possible to improve the waveform reproducibility of the reproduced signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a signal processing device that is an embodiment of the present invention.

FIG. 2 is a waveform diagram showing signal waveforms of each part of a signal processing device that is an embodiment of the present invention.

FIG. 3 is a waveform diagram showing signal waveforms of each part of a signal processing device that is an embodiment of the present invention.

FIG. 4 is a waveform diagram showing signal waveforms of each part of a signal processing device that is an embodiment of the present invention.

FIG. 5 is a waveform diagram showing signal waveforms of each part of a signal processing device that is an embodiment of the present invention.

[Fig. 6] Block diagram showing a conventional embodiment

[Fig. 7] Waveform diagram showing signal waveforms of conventional embodiments

[Explanation of symbols]

1 Input terminal 2 First transmission circuit 3. First storage means 4 Second transmission circuit 5 Second storage means 6 Third transmission circuit 7 Switch 8 Third storage means 9 Output terminal

Claims (1)

[Claims] 1. A first transmission circuit having a transfer characteristic of G, and a storage of a period M connected to the first transmission circuit and at least twice as long as an impulse response duration α of the first transmission circuit. a first storage means having a capacity and sequentially outputting the input signal in a time series opposite to the stored time series every period M; and a first storage means having a transfer characteristic G connected to the output of the first storage means. The second transmission circuit is connected to the first transmission circuit, has a storage capacity of a period M, has a time delay from period α to period (M-α), and has a time delay from period α to period (M-α) for each period M. a second storage means for sequentially outputting input signals in a time series opposite to the stored time series; a third transmission circuit having a transfer characteristic G connected to the output of the second storage means; a switch that switches the output signals of the second and third transmission circuits so that the signals in M are not lost; and a switch that has a storage capacity of at least M, and stores the output signals of the switch in a time series stored for each switching period. A signal processing device comprising: third storage means for sequentially outputting in reverse chronological order.