JPH054857B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a television relay broadcasting system having an automatic gain control function used in an intermediate frequency band, for example, in order to stabilize the transmission output level of a television relay broadcasting machine. This invention relates to a machine equalizer.

[Technical background of the invention and its problems]

In television relay broadcasting equipment, in order to keep the transmission output level constant, there is a means using an automatic gain control circuit or a means combining this with a circuit for equalizing the video/audio level ratio. Each of the circuits shown in FIGS. 1 to 3 is a conventional equalization device. In the apparatus shown in FIG. 1, when a television intermediate frequency signal is derived through an amplifier circuit 11, a combination circuit 12 and a filter circuit 1 are selected from the output of this circuit.
A video intermediate frequency signal is extracted through a detector circuit 3, and is added to a detection circuit 4 for AM detection. Since the output level of the detection circuit 14 corresponds to fluctuations in the input level, it is applied to the control circuit 5 to determine a control amount, and is used as a gain control signal for the amplifier circuit 11. The input/output characteristics of the above device regarding the video intermediate frequency signal level are as shown in Figure b.
There is a range in which the output can be maintained constant even if the input level changes. Further, the input/output characteristics regarding the level ratio (V/A) between the video intermediate frequency signal and the audio intermediate frequency signal are the characteristics shown in FIG.

The equalizer shown in FIG. 1 is a general type that uses only a video intermediate frequency signal and is economical. However, there is a drawback that it cannot deal with changes in the balance between the video intermediate frequency signal level and the audio intermediate frequency signal level of the input signal itself. For this reason, the output may not comply with the Radio Law, or the output characteristics of the device may change significantly, resulting in deterioration, resulting in a lack of stability as a broadcasting device.

In the device shown in FIG. 2, the output of an amplifier circuit 20 is passed through a variable frequency characteristic circuit 21 and outputted to an output terminal 22. In this device, the video intermediate frequency signal is derived via a coupling circuit 23 and a filter circuit 24 and is applied to a detection circuit 25. Further, the audio intermediate frequency signal is passed through the coupling circuit 26 and the filter circuit 2.
7 and applied to the detection circuit 28.
The output of the detection circuit 25 is transmitted to a first control circuit 29.
is added to determine the control amount, and the amplifier circuit 2
The control signal is set to 0. Furthermore, the outputs of the detection circuit 25 and the detection circuit 28 are applied to a second control circuit 30 that detects the level ratio of both outputs and determines the control amount, and the output indicating the level ratio is used to change the frequency characteristic. This is used as a control signal for the circuit 21. The input/output characteristics of the above device regarding the video intermediate frequency signal level are as shown in FIG. In addition, in the case of this device, since the video intermediate frequency signal and the audio intermediate frequency signal are also equalized, the input/output characteristics regarding the level ratio (V/A) of the video intermediate frequency signal and the audio intermediate frequency signal are shown in the figure. The characteristic shown in c is obtained, and the level ratio can be kept constant. Frequency characteristic variable circuit 21
The control dynamic characteristics are as shown in figure d, and the gain control ranges for the video intermediate frequency signal (fv) side and the audio intermediate frequency signal f _A side are set as shown by the broken lines, and the level ratio of both is constant. It can be controlled so that

The equalizer shown in FIG. 2 can compensate for variations in the ratio of the video intermediate frequency signal level to the audio intermediate frequency signal level. However, if an amplitude modulation component is generated in the audio signal due to propagation, there is a drawback that the generation of audio beats cannot be prevented and the image quality is adversely affected.

Next, an equalization device as shown in Fig. 3 can be considered to compensate for the drawbacks of the above device, but it has a drawback in the configuration that separates the video intermediate frequency signal and the audio intermediate frequency signal, and the output characteristics of the device deteriorate. I'm letting you do it. That is, the output of the amplifier circuit 31 is supplied to the distributor 32. One output of this divider 32 is supplied to a filter circuit 33 set to the video intermediate frequency band, and the other output is supplied to a filter circuit 34 set to the audio intermediate frequency band.

The output of the filter circuit 33 is supplied to the synthesis circuit 36 via the output amplification circuit 35, and the output of the filter circuit 34 is supplied to the level limiting circuit 37 and the amplifier circuit 3.
8 to the synthesis circuit 36. The output of the synthesis circuit 36 is led out to an output terminal 39 and is also supplied via a coupling circuit 40 to a filter circuit 41 set to the video intermediate frequency band. The output of this filter circuit 41 is subjected to AM detection by a detection circuit 42, and the control amount of its DC output is determined by a control circuit 43, and is applied to the amplifier circuit 31 as a control signal.

According to the above device, changes in the ratio of the video intermediate frequency signal level to the audio intermediate frequency signal level and amplitude modulation components of the audio intermediate frequency signal can be effectively dealt with. This is because the video intermediate frequency signal and the audio intermediate frequency signal are separated by the distributor 32 and each is adjusted by an amplifier circuit, and the audio intermediate frequency signal is also suppressed by the level limiting circuit 37. However, when separating audio intermediate frequency signals, there is a drawback that when the bandwidth becomes large, color subcarriers are located close to each other, and color signals are mixed, making it difficult to suppress deterioration of characteristics. In other words, residual amplitude modulation distortion occurs more often in characteristics related to audio signals. Furthermore, it is observed that large group delay distortion occurs in characteristics related to video signals.

[Purpose of the invention]

The present invention has been made to address the above-mentioned circumstances, and is capable of detecting various signal changes occurring in relay line propagation paths such as television broadcast waves, and is capable of detecting the ratio of video intermediate frequency signal level to audio intermediate frequency signal level. An object of the present invention is to provide an equalization device for a television relay broadcaster that can stabilize the amplitude modulation component of an audio signal and suppress the amplitude modulation component of an audio signal.

[Summary of the invention]

In this invention, for example, as shown in FIG.
7, 69, control circuits 70, 68, a distributor 54, a filter circuit 57, an amplitude modulation component extraction circuit 58, etc. to form a loop to achieve the above object.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 4 to 6.

FIG. 4 shows an equalizer for a television relay broadcaster, in which a television intermediate frequency signal is supplied to an amplifier circuit 52 via an input terminal 51. The output of this amplifier circuit 52 is transmitted to the frequency characteristic variable circuit 53.
The output of this circuit is supplied to a distributor 54. One output of this divider 54 is supplied to one input end of a synthesis circuit 56 via a phase shifter 55, and the other output is supplied to a filter circuit 57 in which audio intermediate frequency band characteristics are set. be done.

The output of the filter circuit 57 is supplied to a distributor 59 of a circuit 58 for removing amplitude modulation components contained in the FM modulated audio signal (hereinafter referred to as an amplitude modulation component extraction circuit). One output of this divider 59 is supplied to an amplitude limiting amplifier circuit 60, and the other output is supplied to an amplifier circuit 61 for amplifying to a required level.
supplied to The amplitude limiting amplifier circuit 6
0 and the respective outputs of the amplifier circuit 61 are connected to a combining circuit 6.
2. The output of this combining circuit 62 is supplied to the other input terminal of the combining circuit 56. The output of this synthesis circuit 56 is supplied to a distributor 63, one output of this distributor 63 is led out to an output terminal 64, and the other output is supplied to a filter circuit 65 and a filter circuit 65 in which audio intermediate frequency passband characteristics are set. Filter circuit 66 in which video intermediate frequency passband characteristics are set
supplied to

The output of the filter circuit 65 is sent to a detection circuit 67.
The output of this detection circuit 67 is
It is supplied to one input terminal of the level ratio control circuit 68. Further, the output of the filter circuit 66 is subjected to AM detection in a detection circuit 69, and the output of this detection circuit 69 is supplied to the other input terminal of the level ratio control circuit 68, and is also supplied to the input terminal of the gain control circuit 70. supplied to The output control signal of the level ratio control circuit 68 is supplied to the control terminal of the frequency characteristic variable circuit 53, and the output control signal of the level ratio control circuit 68 is supplied to the control terminal of the frequency characteristic variable circuit 53.
The output control signal is supplied to the gain control terminal of the amplifier circuit 52.

One embodiment of the present invention is constructed as described above, and its operation will be explained next.

The television intermediate frequency signal applied to the input terminal 51 is equalized in level to the video intermediate frequency signal by the amplifier circuit 52, and is supplied to the frequency characteristic variable circuit 53. In step 53, the ratio (V/A) between the level of the video intermediate frequency signal and the level of the audio intermediate frequency signal is controlled to a constant ratio. As shown in FIG. 5, the dynamic characteristics of the variable frequency characteristic circuit 53 are such that the level increases or decreases from the video intermediate frequency signal (f _V ) toward the audio intermediate frequency signal (f _A ). It is a characteristic that can be controlled. That is, the range shown by the broken line is based on the level shown by the solid line. The output of this variable frequency characteristic circuit 53 is supplied to a distributor 54, one output of this distributor 54 is applied to a combining circuit 56 via a phase shift circuit 55, and the other output is supplied to a filter circuit 57. Ru.

The filter circuit 57 is set so that only the audio intermediate frequency signal component can pass therethrough, but is constructed so that no component related to the video signal remains. In other words, the audio intermediate frequency signal extracted by the filter circuit 57 is transmitted to the amplitude modulation component extraction circuit 8.
added to. In this circuit, the audio intermediate frequency signal is distributed by a distributor 59, and one is applied to an amplitude limiting amplifier circuit 60, where the amplitude modulation component is removed and the signal is amplified to a predetermined level. Therefore, the output of the amplitude limiting amplifier circuit 60 has a signal waveform of a constant level as shown in FIG. 6b. On the other hand, the amplifier circuit 61 amplifies the audio intermediate frequency signal to a required level, resulting in a signal waveform as shown in FIG. 6a. As shown in the figure, the level relationship between the signals in FIG. A minimum amplitude B appears. The relationship A≧C≧B is determined.

The outputs of the amplitude limiting amplifier circuit 60 and the amplifier circuit 61 are introduced into a combining circuit 62. in this case,
The input signals are set to have opposite phases to each other, and the intermediate reference level is synthesized at the same level (average level). Therefore, if an amplitude modulation component occurs in the audio intermediate frequency signal during propagation, the sixth
As shown in Figure C, only the amplitude modulation component is output. If the audio intermediate frequency signal is of good quality, there is usually no output signal. Note that a gain control circuit may be provided between the amplitude-limiting amplifier circuit 60 and the amplifier circuit 61 in order to make the output levels of the amplifier circuits 60 and 61 match.

The output of the amplitude modulation component extraction circuit 58 is supplied to a synthesis circuit 56. This synthesis circuit 56 includes
A television intermediate frequency signal is introduced as the main signal. In this case, the main signal is delayed by the phase shift circuit 55, and the time axis is made to coincide with the system on the amplitude modulation component extraction circuit 58 side. In this case, for the audio intermediate frequency signal, the distributor 54
The phase relationship of the two systems between the combining circuits 56 is set so that they are in opposite phase relationship to each other. This may be done using any system, but the phase of the audio signal carrier wave may be set to +180° or -180°. When the two systems of signals set in such a phase relationship are combined in the combining circuit 56, the amplitude modulation component of the audio intermediate frequency signal on the main signal side is extracted as shown in FIG. 6c above. It will be suppressed by the signal from the circuit.

In this case, the reference levels of the main signal and the output of the extraction circuit are adjusted to be the same. For this purpose,
A gain controller may be added to the amplitude modulation component extraction circuit 58 to match the extracted amplitude modulation component level with that of the main signal side.

The amplitude modulation component is removed by the above two loops and sent to the distributor 63. One output of this distributor 63 is led out to an output end 64, and the other output is supplied to a filter circuit 65 and a filter circuit 66. The filter circuit 65 has audio intermediate frequency passband characteristics, and its output is applied to a detection circuit 67 for AM detection. Further, the filter circuit 66 has video intermediate frequency passband characteristics, and this output is applied to the detection circuit 69 and
Detected. The outputs of the detection circuits 67 and 69 are:
Level ratio control circuit 6 that detects the level ratio of both outputs
Added to 8. This level ratio control circuit 8 controls the frequency characteristic variable circuit 53 so that the level of the video intermediate frequency signal and the level of the audio intermediate frequency signal become a predetermined ratio. Further, the detection circuit 69
The output of is also applied to a control circuit 70, which controls the gain of the amplifier circuit 52 according to the input signal level and equalizes the video intermediate frequency signal.

〔Effect of the invention〕

As described above, according to the device of the present invention, there is provided a comprehensive output signal level equalization circuit means including the distributor 63, the filter circuit 66, the detection circuit 69, the control circuit 70, and the amplifier circuit 52;
Filter circuits 65, 66, detection circuits 67, 69,
A control circuit 68 , a video/audio intermediate frequency signal output level ratio equalization circuit means by the second loop of the frequency characteristic variable circuit 53 , a distributor 54 , and a filter circuit 5
7. Audio intermediate frequency signal amplitude modulation component extraction circuit 5
8. It has an amplitude modulation component suppression circuit means formed by a synthesis circuit 56, a phase shift circuit 55, etc., and can contribute to high quality equalization and image quality.

When the input signal is normal, the amplitude modulation component suppression circuit means can maintain the quality of the input signal with no output from the combining circuit 62, and operates to achieve its purpose only when the input signal is abnormal. , this is a method for performing correction. Therefore, the reliability of the characteristics of the main signal line is improved and the suppression circuit means does not have any adverse effects. Furthermore, since the video intermediate frequency signal and the audio intermediate frequency signal are not treated separately as shown in FIG. 3, the system can operate with good performance even if the bandwidth for the audio signal is increased. Furthermore, the level ratio equalization circuit means can be used to equalize the level of the audio intermediate frequency signal as shown in the dynamic characteristic shown in FIG. It is also possible to cope with signal level changes due to aging.
(This is because a level change due to selective fading is considered to correspond similarly to a change in characteristics as shown in FIG. 5.) The present invention is not limited to the above embodiment, and the distributor 54, Similar effects can be obtained even if the arrangement of the combining circuit 56 is reversed. That is, in the embodiment, the distributor 54 is placed at the front stage and the synthesis circuit 56 is placed at the rear stage, but this is reversed, and the amplitude modulation component extraction circuit 58 is also placed in the opposite left and right from the arrangement shown in the figure. . With this arrangement, the configuration is such that amplitude modulation distortion is detected in the subsequent stage and fed back to the previous stage, and at the same time automatic correction of the gain change of this correction circuit is facilitated.

The present invention is characterized in that it is a device having the above-mentioned amplitude modulation component suppression circuit means. Therefore, in order to obtain the control amount for the amplifier circuit 52, the control amount may be obtained by smoothing not only the video intermediate frequency signal but also the entire output signal of this equalizer. In addition, video intermediate frequency signals and audio intermediate frequency signals were used to control the frequency characteristics.
In addition, a video intermediate frequency signal and a television color burst signal may be used, and a means as shown in FIG. 2 may be used.

As explained above, according to the present invention, various signal changes occurring in relay line propagation paths such as television broadcast waves can be detected, and the ratio of video intermediate frequency signal level to audio intermediate frequency signal level can be stabilized. In particular, an equalizer for a television relay broadcaster that can remove amplitude modulation components and suppress residual amplitude modulation distortion from FM modulated audio signals, and can also effectively exhibit its effects when increasing the bandwidth of audio signals. can be provided.

[Brief explanation of the drawing]

Figure 1a is an explanatory diagram of the configuration of a conventional equalizer;
Figures b and c are characteristic diagrams of the device shown in Figure a, Figure 2 a is an explanatory diagram of the configuration of a conventional equalizer, and Figures 2 b, c, and d are characteristic diagrams and dynamic characteristic diagrams of Figure A, respectively. , FIG. 3 is an explanatory diagram of the configuration of a conventional equalization device, FIG. 4 is an explanatory diagram of the configuration of an embodiment of the equalization device for a television relay broadcasting machine of the present invention, and FIG. FIGS. 6a, b, and c are dynamic characteristic diagrams of the frequency characteristic variable circuit shown in FIG. 52...Amplification circuit, 53...Variable frequency characteristic circuit, 54...Distributor, 55...Phase shift circuit, 57...
... Filter circuit, 58 ... Amplitude modulation component extraction circuit, 60 ... Amplitude limiting circuit, 61 ... Amplification circuit.

Claims (1)

[Scope of Claims] 1. means for equalizing the video intermediate frequency signal level by applying a control signal from automatic gain control means to an amplifier circuit into which the television intermediate frequency signal is introduced;
level ratio equalization circuit means to which the output of the amplification circuit is applied and which maintains a constant ratio between the video intermediate frequency signal level and the audio intermediate frequency signal level; and a main television intermediate circuit derived from the level ratio equalization circuit means. a first path consisting of a phase shift circuit to which a frequency signal is applied; and a first path provided in parallel with the first path to extract an amplitude modulation component of an FM audio intermediate frequency signal at a stage before or after the first path. For the above
an extraction means for extracting an amplitude modulation component by dividing the FM audio intermediate frequency signal into an amplitude-limited one and an amplified one, adjusting the levels of both, and recombining the two; and the amplitude obtained from the extraction means. synthesis means for synthesizing the modulation component with the main television intermediate frequency signal at the subsequent stage or the preceding stage of the first path to cancel amplitude modulation distortion of the audio intermediate frequency signal included in the main television intermediate frequency signal. An equalizer for a television relay broadcasting machine, characterized in that: 2. The extracting means includes a distributor to which the output of the main television intermediate frequency signal is applied via a filter circuit in the audio intermediate frequency band, and an amplitude limiter to which the output of one of the distributors is applied to limit the amplitude. The present invention further comprises: an amplifier circuit and an amplifier circuit which amplifies the power of the other one of the amplifier circuit and the divider to a required level; and a synthesis circuit which combines the output of the amplifier circuit and the output of the amplitude limiting amplifier circuit. An equalizer for a television relay broadcasting machine according to claim 1.