JPS6057775A - Signal generator - Google Patents

Abstract

PURPOSE:To obtain a signal having a desired leading edge and trailing edge characteristic by providing an upper limit and a lower limit variable limiter to a pulse signal source to change the amplitude and passing an output of the limiters through an active low pass filter. CONSTITUTION:When a signal is applied to an input terminal 71, this signal is fed to a comparator comprising transistors (Trs) 72, 73 and fed to a connecting point of Trs 76, 77 constituting the limiters through Trs 74, 75. Since voltages V1, V2 from voltage sources 78, 79 are applied to the Trs 76, 77 respectively, a signal where the upper limit is limted to V1+VBE and the lowe limit is limited to V2-VBE is fed to a base of a Tr80. Then this signal is fed to the active low pass filter 16 having a T filter characteristic comprising TRs 80, 81 and 82 or the like and the signal having the characteristic of the T filter is outputted to an output terminal 83. Further, the output amplitude is adjusted by changing the voltages V1 and V2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a signal generation device suitable for use as a reference signal generator used in a ghost removal device or the like.

Background technology and its problems Conventionally, the following ghost removal devices have been proposed.

For example, in FIG. 1, a signal from an antenna (1) is supplied to a video detection circuit (4) through a tuner (2) and a video intermediate frequency amplifier (3), and a video signal is detected.

This video signal is fed to a synthesizer (6) via a delay circuit (5) corresponding to the period for eliminating the preceding ghost, and a canceling signal simulating a ghost from a transversal filter, which will be described later, is applied to this synthesizer. The video signal from which ghosts have been removed is taken out to an output terminal (7) from the synthesizer (6).

Further, a video signal obtained from the video detection circuit (4) is supplied to a delay circuit (8) constituting a transversal filter. This delay circuit (8) has a sampling period (
For example, a plurality of stages (n (If, l)) of delay elements each having a unit of 10 (ns) are connected to have a delay time equal to the preceding ghost removal period, and n1 from between each stage.
The lIil tap is derived. The weighted signals from each of the taps are supplied to circuits (9>), (92), . . . (9n), each consisting of a multiplier.

Further, the signal from the end of the delay circuit (8) is supplied to the terminal (10f) of the mote switch αU), and the signal from the end of the delay circuit (8) is also supplied to the terminal (10f) of the
The output signal of 6) is supplied to the terminal (10b) of the switch αθ). The signal from this switch Uω is transmitted to the delay circuit (1
1). In this delay circuit (11), delay elements each having a sampling period as a unit are connected in multiple stages (m111j) to have a delay time equal to the post-ghost removal period, and m taps are derived from between each stage. It is something. The signals from each tap are weighted by multipliers (=J circuits (121), (122)
...(12m).

Also, the video signal from the synthesizer (6) is sent to the subtraction circuit (13).
supplied to Furthermore, the video signal from the delay circuit (5) is supplied to the synchronization separation circuit (14), and the separated vertical synchronization signal is sent to the pulse generation circuit (
15), the signal is supplied to a low-pass filter (16) to form a waveform that approximates the step waveform of the leading edge VE of the vertical synchronizing signal. This standard waveform is supplied to a subtraction circuit (13).

The signal from this subtraction circuit (13) is supplied to a differentiation circuit (17) to detect ghosts.

Here, as a signal for ghost detection and measurement, a signal that is included in a standard television signal and is not affected by other signals for as long as possible, such as a vertical synchronization signal, is used. As shown in FIG. 2, the leading edge VE of the vertical synchronizing signal and its i;1 subsequent edge +H (H is a horizontal period) are not affected by other signals. Therefore, the above-mentioned standard waveform is subtracted from the signal during this period, and this subtracted signal is differentiated to obtain I4.
Detect the I locating coefficient.

For example, the phase difference ψ(-ωC
τ, where ωC is a video signal with a waveform as shown in FIG. 3A when the image at the high frequency stage (general angular frequency) includes a 45° ghost.

On the other hand, by differentiating this signal and inverting the polarity, a ghost I detection signal with the differential waveform shown in FIG. 3B is obtained, and this differential waveform can be approximately regarded as a ghost impulse response. can.

Then, the differential waveform ghost detection signal ζ appearing from the differentiating circuit (17) is supplied via the amplifier (18) to the demultiplexers (19) and (20) connected in series. These demultiplexers (19) and (20) are connected to the delay circuit II.
Similar to Ir(81, (11)), delay elements each having a sampling period as a unit are connected in multiple stages, and m and n taps are derived from between each stage.The output of each tap is are the switch circuit (2h) and (
212) ... (21n), (221), (2
22) ... is supplied to (22m).

Further, the vertical synchronization signal from the synchronization separation circuit (14) is supplied to the gate pulse generator (23), and a gate pulse corresponding to the end of the +■ (section) is formed from the leading edge VE of the vertical synchronization signal mentioned above. , this pulse causes the switch circuit (
21s) to (22m) are turned on.

Signals from these switch circuits (2b) to (22m) are sent to analog accumulators (241) and (242), respectively.
・ (24n), (251) + (252) ...
(25m). This analog accumulator (24
i) The signals from (25m) are connected to the circuit (
91) to (9n), (121) to (12m).

These weights are applied to circuits (91) to (9n), (12z
) to (12m) are added by an adder circuit (26) to form a cancellation signal. This cancellation signal is then supplied to the combiner (6).

As mentioned above, the delay circuit +81. (11), the number of times h8 (9t) ~ (9n), (12t) - (
12m) and the adder circuit (26) constitute a transversal filter to remove ghosts. In this case, after detecting the waveform distortion of the leading edge of a certain vertical synchronization signal and the +11 sections before and after it and determining the coefficient of the wheel attachment,
If ghost remains unerased, the above-mentioned detection is performed, and in order to reduce the unerased ghost, an analog accumulator (2
41) to (25 m) are installed.

Note that by switching the mode switch α0), the rear ghost removal can be switched between the feedforward mode and the feedhack mode.

Furthermore, Fig. 4 shows a case where ghosts are removed using a manually added type transversal filter, and the same parts as in Fig. 1 are given a detailed explanation by marking the same parts as in Fig. 1. omitted.

In the figure, the video signal from the video detection circuit νh(4) is supplied to the weighted circuits @ (91) to (9n), and the weighted signals from the circuits (9]) to (9n) are delayed, respectively. (J) is supplied to the input terminal of the circuit (8'). This delay circuit (8') is connected with n delay elements each having a sampling period as a unit, and has n input terminals between each stage. was established.

Also, the signals on the input side and output side of the synthesizer (6) are the terminals (10f') + (10b) of the mode switch (10').
') is supplied. Signals from this switch (10') are supplied to weighted circuits (121) to (12m), and signals from the weighted circuits (121) to (12m) are input to delay circuits (11'), respectively. Supplied to the terminal. This delay circuit (11') has m delay elements connected in units of sampling periods, and m input terminals provided between each stage.

Signals taken out from the respective terminal ends of these delay circuits (8') and (11') are added by an adder circuit (26') to form a cancellation signal. This cancellation signal is then supplied to the combiner (6).

In this circuit as well, ghosts are removed in the same way as in the circuit using the output addition type transversal filter described above.

Furthermore, in the above-mentioned circuit, a differential output is obtained by using the difference between the outputs of adjacent bits of the demultiplexers (19) and (20) without providing a differentiating circuit (17), and this differential output is used to detect a vehicle. You can also do this.

Also, the demultiplexers (19), (20) and the delay circuit'
I! F! It is also possible to make (81 and (11) common), supply a weight signal to the slow purification circuit when setting market &j, store this in a memory element, and perform Kiji addition using this memory signal thereafter. .

In this way, ghosts can be removed, for example in the video m stage.

By the way, when such a ghost removal device is turned on, standard waveform formation and switch times IM (21+) to (22
For example, the leading edge of the vertical synchronization signal is used as the reference time for the switching timing in m). In this case, extremely high precision is required to detect this reference time, and it has been experimentally shown that precision within 35 nsec is required.

In the case of a conventional synchronous separation circuit, since the circuit includes a low-pass filter, the 1111 area information (・shi is missing,
The rise of the signal, etc. will be blunted, and there is a risk that a time delay will occur if the reference time is detected from the vertical synchronization signal separated in this way.

On the other hand, it has been proposed to form a masking pulse of approximately +H period including the leading edge of the vertical synchronizing signal, and to directly detect the transit of the leading edge using this masking pulse and Hide No. 4g.

However, in the case of this method, ff(j'
If the formation position of the masking pulse at Jl is incorrect, another transit may be detected and the reference time may be significantly deviated. This is especially true when the ghost removal device is in a weak electric field.
This is a problem because they are often used in poor conditions.

Since the above-mentioned masking pulse only needs to have a +I period that includes the leading edge of the vertical synchronizing signal, very high precision is not required in forming this masking pulse. Furthermore, since the conventional synchronous separation circuit includes a low-pass filter, noise is suppressed and there is less risk of malfunction due to noise.

Therefore, the inventor of the present application previously proposed the following circuit. In FIG. 5, C1 (31) is an input terminal to which a video signal is supplied, and the signal from this terminal (31) is input to a comparator (
32) and a low-pass filter (33), and the signal from this low-pass filter (33) (to Fig. 6) is fed to the vertical synchronization separation circuit (34) consisting of a bus filter. This separation circuit (3
The vertical synchronizing signal (FIG. 6B) separated in step 4) is supplied to a masking pulse forming circuit (35), and is converted into a triangular wave (
6C) is formed, and this and the reference potential (broken line) form a masking pulse (FIG. 6D) corresponding to the →-H period including the leading edge of the vertical synchronizing signal. This masking pulse is supplied to the control terminal of the comparator (36). Also, the signal from the terminal (31) passes through the amplifier (37) to °C.
It is supplied to the ratio ratio device (36). And this comparator (36
), the leading edge of the vertical synchronization signal (Fig. 6 E), which is the reference time, is detected by detecting the rising edge of the signal (Fig. 6 E), and the 1 = 0 pulse (Fig. 6 F ) is taken out to the output terminal (38).

Alternatively, in FIG. 7, the signal from the input terminal (31) passes through a clamping capacitor (41) to a transistor (42), a resistor (43), which constitutes a bias circuit.
An electric current is supplied to the connection point between the resistor (43) and the constant current source (44) in the series circuit of the constant current source (44). Further, the signal at the midpoint of this connection is supplied to the base of one transistor (45) constituting the differential amplifier. Further, the base of the other transistor (46) is connected to an I
・Landisk (47), resistor (48), constant current source (
49) series circuit resistor (48) and constant current dJ51
The voltage from the connection midpoint of (49) is supplied. A signal current flowing through the collector of the transistor (46) is extracted through a current mirror circuit (50).

Furthermore, this signal is supplied to a low-pass filter (52) and a buffer amplifier (53) through a switch (51), and is also supplied to a low-pass filter (54) through a switch (54).
5) and a buffer amplifier (56). Signals from the buffer amplifiers (53) and (56) are added by resistors (57) and (5B) and supplied to a comparator (59). A signal from the current mirror circuit (5o) is also supplied to the comparator (59).

The signal from this comparator (59) is supplied to the D terminal of the D flip-flop circuit (60), and at the same time its polarity is inverted and supplied to the clear terminal of the flip-flop circuit (60). Further, the masking pulse from the formation circuit 1M (35) is supplied to the clock terminal of the flip-flop circuit II (60), and the output of this flip-flop circuit (60) is taken out to the output terminal (38).

In this circuit, current mirror times 11Pt (50)
For example, a signal as shown in FIG. 8 is taken out from.

In response to this signal, the switches (51) and (54) are turned on, for example, during the periods shown in FIGS. 8B and 8C, respectively. As a result, from the buffer amplifiers (53) and (56),
Shift values (L, E 2 ) corresponding to the pedestal of the synchronization signal and the level of the sync tip, respectively, are obtained. These potentials are added by resistors (57) and (5B). Here, if the resistance values of the resistors (57) and (5B) are R1 and R2, the potential E3 obtained by addition is EI R2 E2 RI E3=□ R1+ R2, and if R2<R1, Ei E2 E3 □ becomes. When this potential E3 is supplied to the comparator (59), a signal as shown in the eighth diagram is taken out from the comparator (59). On the other hand, the masking pulse forming circuit (35
) outputs a signal as shown in FIG. 8E. By supplying these signals to the flip-flop circuit (60), a signal as shown in FIG. 8F is output to the output terminal (38).
) is taken out.

In this way, the reference time is detected.

By the way, in such a device, the pulse generation circuit (1
5) and a low-pass filter (16), a standard waveform similar to the step waveform of the leading edge VE of the vertical synchronization signal in the standard television signal is formed.

In that case, the step waveform of the leading edge VE of the vertical synchronization signal is a waveform obtained by filtering a 1:J-pass filter called a 1θ''F filter in the NTSC system by 1III!J.Here, In order to obtain this waveform, it is sufficient to form a steep pulse with a predetermined one-line width in the pulse generation circuit (15) and supply this pulse to a low-pass filter (16) having T-filter characteristics.

However, in this case, it is difficult to obtain a sudden pulse with a predetermined amplitude, and because conventional circuits have been discrete, for example, a circuit as shown in Fig. 9 is used. There was C. In the figure, the ζ pulse generation circuit (15
) generates a sharp pulse with sufficient amplitude flit, and after passing this signal through a low-pass filter (16), it is supplied to a desired amplitude control circuit (70) to obtain a predetermined waveform.

However, in this device 6 -"- bath soiler (1
6) What happens when the human input signal has a large amplitude, especially when using an active filter for IC, etc.? This results in insufficient source voltage, making it difficult to obtain good filter l) and li properties.

For example, if the one-pass filter (16) as shown in Fig. 10 is configured with discrete components and the amplitude control circuit (70) is configured with a volume, when the volume is moved to adjust the amplitude, the DC current of the signal is The components also fluctuate, and in particular, in a ghost removal device, the dynamic range of the subsequent transversal filter, etc. is narrow, so it becomes necessary to perform additional clamping or the like.

OBJECTS OF THE INVENTION In view of these points, the present invention is intended to enable a desired waveform to be obtained with a simple configuration.

SUMMARY OF THE INVENTION The present invention provides a pulse signal source with a sufficiently steep rise.
An upper limit limiter and a -t limiter are provided, and at least one of the limiters is moved to change the amplitude, and
A signal generator that passes the output of the limiter through an active low-pass filter to obtain a signal having a desired rise or fall characteristic, and with this, a desired waveform can be obtained with a simple configuration. .

In FIG. 11 of the embodiment, the input terminal (71) includes, for example, the first
A signal having a falling edge a at the timing of the vertical synchronization signal as shown in FIG. 2A is supplied. This signal is supplied to a comparator consisting of transistors (72) and (73),
A pulse as shown in FIG. 12B is taken out to the collector of the transistor (74).

Note that this pulse is the same as that shown in FIG. 6E, and the rising edge of this leading edge has a sufficiently steep waveform.

This signal is supplied through transistors (74) and (75) to a connection point between transistors (76) and (77) forming a limiter. These transistors (76), (77
) have voltages V from voltage sources (78) and (79), respectively.
1, V2 is supplied. This allows the transistor (
80), the upper limit shown in Figure 12C is V1.
+VRE, a signal whose limit is V 2 V 6H is supplied.

This signal is connected to transistors (80), (81), (82)
The signal is supplied to an active low-pass filter (16) having T-filter characteristics, and a signal having T-filter characteristics, such as a blur in the twelfth diagram, is formed and taken out to an output terminal (83).

In other words, FIG. 13 is an enlarged view of the necessary rising waveform of the output signal, with the upper side being Vl 2Vee and the lower side being V2 4Vee.
At the voltage VBH, a signal whose interval has the characteristics of a T filter is formed.

Note that in this circuit, the voltage sources (78) for Vl and V2,
By making (79) variable, the amplitude of the filter output can be adjusted. Therefore, for example, if the original signal to be ghost canceled is pedestally clamped, Vl-2VH [I should match the clamp level. The amplitude of the signal can be adjusted to match the level of the original signal.

In the circuit roughly described above, the output signal has a voltage of -2V on the upper side.
, , has a temperature characteristic related to -4VB on the lower side,
This can be compensated for, for example, by providing the voltage sources (78) and (79) with temperature characteristics that offset this.

That is, FIG. 14 shows an example of a voltage source circuit having such temperature characteristics. In the figure, the voltage V corresponding to the center of the dynamic range of the subsequent circuit is applied to the base of the transistor (91).
o is supplied. The constant voltage obtained at the base of the transistor (92) is controlled by three diodes (93), a resistor (94), a constant current source (95), and a transistor (96).
), and the voltage ■1 becomes Vx=Vo+2Vsti+Δ■1, where Δ■1 is the voltage determined by the resistor (94) and constant current source (95). Also, the constant voltage is 3 diodes 1' (93) and 2
diodes (97), a resistor (9B), a constant current source (99), and an I-transistor (100). Assuming that the voltage determined by ζ is Δ■2, it becomes ζ V2-Vo +4VB days and Δ■2, so that the voltages Vl and V2 having the 11υ4 degree characteristic 11 of +2VB days and ]-4V volumes can be obtained.

As described above, a waveform with a desired amplitude and a predetermined '1' filter characteristic is formed. However, according to the above-mentioned step 1, an active filter can obtain -ζ accurate characteristics. At the same time, there is no fear of insufficient power supply voltage in the active filter, and a circuit particularly suitable for IC implementation can be obtained.

In addition, swing + + a control etc. can be easily performed, and there is no fear of fluctuations in the DC level at that time. Therefore, it is possible to easily match the dynamic range of the subsequent circuit.

Effects of the Invention According to the present invention, it has become possible to create a desired waveform (M) with a simple configuration.

[Brief explanation of the drawing]

Figures 1 to 10 are diagrams for explaining the conventional device.
FIG. 1 is a configuration diagram of an example of the present invention, and FIGS. 12 to 14 are diagrams for explaining the same. (15) is a pulse generation circuit, (16) is an active low-pass filter, (76) and (77) are limiter transistors, and (7B) and (79) are voltage sources. Procedural amendment document January 13, 1980 1, Indication of the case 1988 Patent Application No. 1625569 2, Title of the invention Signal generator 3, Relationship with the person making the amendment Patent applicant address Tokyo Parts Yoku Kita Product name 6-7-35 (2+
8) Norio Ohga, Representative Director of Sony Corporation 6. Number of inventions increased by amendment (1) In the specification, page 11, line 12 [Transistor I46
1 J is corrected to "transistor 05)". (2) Same, page 12, lines 4-6 [D terminal K... to clear terminal] is corrected to "to clock terminal". (3) Same page, line 8, “Clock terminal” should be replaced with “D”
At the same time as it is supplied to the terminal, the polarity is reversed and the clear terminal of the flip-flop circuit is activated.'' (4) Same, page 16, line 3, ``Falling a'' is corrected to ``Rising a.'' (5) In the drawings, Figures 12 and 14 will be corrected as shown in the attached sheet. that's all

Claims (1)

[Claims] A pulse signal source with a sufficiently steep rise is provided with upper and lower limiters, and at least one of these limiters is moved to change the amplitude, and the output of the limiter is passed through an active low-pass filter to obtain the desired value. A signal generator that obtains a signal having rising or falling characteristics.