JP2966394B1 - Television retransmitter with monitoring circuit - Google Patents

Abstract

Kind Code: A1 Abstract: Monitoring is performed with a simple configuration without requiring a special measuring device. A part of a television signal to be output is branched, and a branched output is down-converted in a third mixer by a local signal supplied to a second mixer. As a result, regardless of the output channel value, the down-converted television signal has an intermediate frequency, so that a filter for separating the video signal and the audio signal from the television signal can have a simple configuration. All you have to do is prepare a filter. Then, the level of the separated video signal and the level of the audio signal can be displayed and monitored.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television retransmitting device used for a CATV system or the like.
The present invention relates to a television retransmitting device including a monitoring circuit capable of monitoring output levels of a video signal and an audio signal in the television retransmitting device without using a measuring device.

[0002]

2. Description of the Related Art In a CATV system, a television signal of a predetermined channel is received, the received television signal is separated into a video signal and an audio signal, the level is adjusted to a specified value, and the level is adjusted. There is provided a television retransmitting device which combines a video signal and an audio signal into a television signal again and sends out the television signal at a specified output level. In CATV stations and the like, maintenance is regularly performed, and the output level of a television signal and the ratio of the video signal level to the audio signal level (VA ratio) are checked. The maintenance in this case is performed on a large scale using a measuring device such as a video analyzer different from the device provided in the CATV station. However, small-scale CATV stations and radio interference countermeasures facilities often do not have the above-mentioned special and expensive measuring instruments, so that it is not possible to confirm the output level of the television signal and its VA ratio. there were.

[0005] Therefore, a television retransmitting apparatus including a monitoring circuit capable of easily confirming the output level of a television signal and its VA ratio can be considered. FIG. 5 shows an example of the configuration.
Shown in In FIG. 5, a television signal received by an antenna or the like is input to a channel selection unit 101, and a television signal of an arbitrarily selected channel is output to a high-frequency amplifier 102. The high frequency amplifier 102 amplifies the television signal of the selected channel and amplifies the signal by the first mixer (MIX).
1) Supply to 103.

A first mixer 103 is supplied with a first local oscillation signal oscillated by a first local oscillator 104, which is a variable frequency oscillator, and converts a television signal of a selected channel into an intermediate frequency. Note that the frequency of the first local oscillation signal is changed to a frequency at which the frequency of the selected channel can be converted to an intermediate frequency. The television signal of the selected channel converted to the intermediate frequency is amplified by an intermediate frequency amplifier (IF amplifier) 105, and its output is supplied to a first bandpass filter (BPF1) 106 and a second bandpass filter (BPF2). 109. The first bandpass filter 106 extracts a video signal, and the video signal is supplied to the synthesis unit 107. Further, the extracted video signal is supplied to an AGC circuit, where an AGC signal is generated based on the level of the video signal, and the high frequency amplifier 102 and the intermediate frequency amplifier 105 are controlled, and the squelch circuit 108 described later is controlled. Is done.

In the second band pass filter 109,
The audio signal is extracted, and the audio signal is supplied to the audio level adjustment unit 111 after the noise component of the audio signal frequency-modulated by the limiter 110 is removed. The audio level adjustment unit 111 adjusts the level of the audio signal so that the carrier of the audio signal does not interfere with the video signal of the adjacent channel when the adjacent channel is transmitted. This is because when transmitting a television signal, the carrier of the audio signal is generally prevented from interfering with the video signal of the adjacent channel by not using the adjacent channel. Therefore, adjacent channel transmission using an adjacent channel may be performed in order to effectively use a frequency band. In this case, since the frequency of the carrier of the audio signal is close to the carrier of the video signal of the adjacent channel, the level of the audio signal is set lower than a specified value so as not to interfere with the video signal of the adjacent channel. Adjusted.

That is, the level of the audio signal is adjusted so that the V (Video) / A (Audio) ratio becomes smaller than a specified value. The audio signal whose level has been adjusted so as not to cause interference is supplied to the synthesizing section 107 and synthesized with the video signal to be a television signal. The television signal output from the synthesizing unit 107 is supplied to a squelch circuit 108, and is output as it is if the signal level input to the squelch circuit 108 is equal to or higher than a threshold. In this case, the input signal is blocked. The specified value of the V / A ratio is such that the ratio between the power of the video signal of the television signal and the power of the audio signal in Japan is 4: 1. This is a signal that is attenuated by 6 dB from the video signal.

[0007] The output of the squelch circuit 108 is input to a second mixer (MIX2) 112, and is up-converted by a local oscillation signal selected by a switch SW1 to be a high-frequency television signal. The switch SW1 can select any one of the first local oscillation signal oscillated by the first local oscillator 104 and the second local oscillation signal oscillated by the second local oscillator 113. Here, when outputting a television signal of the same channel as the input channel, the first local oscillator signal oscillated by the first local oscillator 104 is selected by the switch SW1, and the television signal of the original channel is selected by the second mixer 112. The frequency is converted to a signal. When transmitting on a different channel, switch S
A second local oscillator signal oscillated by the second local oscillator 113 is selected by W1 and frequency-converted by the second mixer 112 into a television signal of a predetermined channel.

The high-frequency television signal output from the second mixer 112 is amplified by a high-frequency amplification output level adjustment section 114 so that the television signal has a predetermined output level, and a third band-pass filter (BPF3) 115 Supplied to The television signal from which the unnecessary band has been removed by the third bandpass filter 115 is output through the splitter 116 so as to be retransmitted. Further, the branch signal branched by the branch unit 116 is detected by a diode D1 and supplied to a signal processing unit 118 such as an output level display, and a display process such as an output level is performed. By observing the output level displayed on the signal processing unit 118 such as the output level display, it is possible to monitor the retransmitted television signal.

[0009]

By the way, as shown in FIG. 5, a television signal extracted from the final stage is detected by a diode, and when its level is detected, the output level is adjusted. However, since the TV signal includes a video signal and an audio signal, even if the audio level is adjusted, the detection voltage changes. Therefore, the detection voltage also changes when the VA ratio is adjusted, and it is not possible to specify which of the output level adjustment and the audio level adjustment has changed the detection voltage. Therefore, in order to adjust the output level and the VA ratio, it is necessary to detect the output level of the video signal and the output level of the audio signal.

In consideration of the above, in order to detect the output level of the video signal and the output level of the audio signal in the television retransmission device having the monitoring circuit shown in FIG. The signal may be separated using a band-pass filter or the like, and the separated video signal and audio signal may be detected and their levels may be detected. However, the television signal extracted from the final stage has a high frequency higher than the VHF band, and there is a problem that it is difficult to realize a bandpass filter that separates a video signal and an audio signal in such a high frequency band. . Furthermore, since the output channel of the television signal output from the final stage is not fixed but variable, it is necessary to prepare a band-pass filter of a type corresponding to the settable number of output channels. There are also problems.

Furthermore, since the output channel of the television signal output from the final stage is not fixed but can be set to an arbitrary channel, it is output in a wide frequency range. . Therefore, there is a problem in that a diode for detecting the output signal must have flat detection characteristics over a wide band. Furthermore, even if the video signal can be separated from the output television signal, the amplitude of the video signal fluctuates depending on the picture because the video signal is amplitude modulated, and the video signal level cannot be directly detected from the detection voltage. There are points.

Therefore, the present invention provides a simple method for measuring the output level of an output television signal and the VA ratio of a video signal and an audio signal in the output television signal without requiring a special measuring device. It is an object of the present invention to provide a television retransmitting device including a monitoring circuit that can be accurately detected by a configuration.

[0013]

In order to achieve the above object, a television retransmitting apparatus equipped with a monitoring circuit according to the present invention converts an input high frequency television signal into a first local oscillator signal from a first local oscillator. First converting means for converting an intermediate frequency television signal into an intermediate frequency television signal, audio level adjusting means for separating an audio signal from the intermediate frequency television signal and adjusting the level of the separated audio signal, and the first local unit. Selecting means for selecting and outputting one of a first local signal from an oscillator and a second local signal from a second local oscillator; an audio signal whose level has been adjusted by the audio level adjusting means; A second converter for synthesizing the video signal separated from the frequency television signal, and then converting the local signal output from the selector into a high-frequency television signal; High-frequency output level adjusting means for adjusting the output level of the high-frequency television signal, and a branch output of the high-frequency television signal whose level has been adjusted by the high-frequency output level adjusting means is reduced by a local signal output from the selecting means. Third converting means for converting, and the down-converted television signal output from the third converting means are separated into a video signal and an audio signal by a filter means, and the levels of the separated video signal and audio signal are determined. Level display means for displaying each is provided.

According to another aspect of the present invention, there is provided a television retransmitting apparatus including a monitoring circuit, which converts an input high-frequency television signal into an intermediate signal by a first local oscillator signal from a first local oscillator. First converting means for converting the signal into a television signal of a frequency, audio level adjusting means for separating an audio signal from the intermediate frequency television signal and adjusting the level of the separated audio signal, and Selecting means for selecting and outputting one of the first local oscillation signal and the second local oscillation signal from the second local oscillator; an audio signal whose level has been adjusted by the audio level adjusting means; A second converter for synthesizing a video signal separated from the television signal and then converting the signal into a high-frequency television signal by a local signal output from the selector, and an output from the second converter; High-frequency output level adjusting means for adjusting the output level of the high-frequency television signal; A third converting means for performing
A video level display unit that separates a video signal from a down-converted television signal output from the conversion unit by a filter unit and displays a level of the separated video signal; and an audio level in the audio level adjustment unit. Audio level display means for displaying the level of the audio signal based on the level of the adjustment signal to be adjusted.

Further, in the television retransmitting device provided with the above-mentioned monitoring circuit, the video level display means may include:
Supplying the separated video signal to a video signal demodulation circuit,
The level of the video signal may be detected based on the level of an AGC signal output from a video signal demodulation circuit.

According to the present invention, the output television signal is down-converted by the local signal supplied to the second conversion means, so that the output television signal is fixed as a result. Is converted to the intermediate frequency. Therefore, the video signal and the audio signal can be easily separated from the TV signal converted into the fixed intermediate frequency by using a general band-pass filter such as a surface acoustic wave (SAW) filter. . Also, since the down-converted intermediate frequency is always a constant frequency irrespective of the output channel value, the detection characteristics of the diode for detecting the separated video signal and audio signal do not require wide band characteristics. Become. Furthermore, if the level of the video signal is detected based on the AGC signal in the video demodulation circuit, the level does not fluctuate due to the picture, and the level of the video signal can be accurately detected.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a first embodiment of a television retransmitting apparatus having a monitoring circuit according to the present invention. In FIG. 1, a television signal received by an antenna or the like is input to a channel selection unit 1, and a selected television signal of an arbitrary channel is output to a high-frequency amplifier 2.
The high frequency amplifier 2 amplifies the television signal of the selected channel and supplies it to the first mixer (MIX1) 3.

The first mixer 3 is supplied with a first local oscillation signal oscillated by a first local oscillator 4 composed of a variable frequency oscillator, and converts a television signal of a selected channel into an intermediate frequency. . The frequency of the first local oscillation signal is set to a frequency at which the frequency of the selected channel can be converted to an intermediate frequency. The television signal of the selected channel converted to the intermediate frequency is amplified by an intermediate frequency amplifier (IF amplifier) 5, and the output is output from a first band-pass filter (BPF1) 6 and a second band-pass filter (BPF2). 9. The first bandpass filter 6 extracts a video signal, and the video signal is supplied to the combining unit 7. Further, the extracted video signal is supplied to an AGC circuit 17, where an AGC signal is generated based on the level of the video signal, the amplification of the high frequency amplifier 2 and the intermediate frequency amplifier 5 is controlled, and a squelch described later is provided. The circuit 8 is controlled.

The second band-pass filter 9 extracts the audio signal, removes the noise component of the audio signal that has been frequency-modulated by the limiter 10, removes the noise component from the audio signal, and supplies it to the audio level adjusting unit 11. Is done. The audio level adjustment unit 11 adjusts the level of the audio signal with respect to the video signal. That is, when adjacent channel transmission is performed, V (Video) / A (A) is set so that the carrier of the audio signal does not interfere with the video signal of the adjacent channel.
udio) The ratio is adjusted. This VA ratio is a ratio,
The audio signal is, for example, -9 dB to -14 with respect to the video signal.
The level of the audio signal is adjusted by the audio level adjustment unit 11 so as to attenuate the dB, so that the video signal of the adjacent channel is not disturbed. The level-adjusted audio signal is supplied to the synthesizing unit 7, where it is synthesized with the video signal extracted by the first band-pass filter 6, and re-synthesized into a television signal.

The recombined television signal output from the combining section 7 is supplied to a squelch circuit 8 where the squelch circuit 8
If the input signal level is equal to or higher than the threshold, the signal is output as it is. If the signal level is equal to or lower than the threshold, the input signal is blocked. The output of the squelch circuit 8 is supplied to a second mixer (MIX
2) The signal is input to 12 and up-converted by the local oscillation signal selected by the switch SW1 to be a high-frequency television signal. The switch SW1 is capable of selecting any one of a first local oscillation signal oscillated by the first local oscillator 4 and a second local oscillation signal oscillated by the second local oscillator 13. Here, in the case of a television signal of the same channel as the input channel, the first local oscillator signal oscillated by the first local oscillator 4 is selected by the switch SW1, and the television signal of the original channel is selected by the second mixer 12. Is frequency-converted. When transmitting on a different channel, the second local oscillator 1 is switched by the switch SW1.
3 oscillates and the second local oscillator signal is selected.
2 is frequency-converted into a television signal of a desired channel.

The high-frequency television signal output from the second mixer 12 is amplified by the high-frequency amplification output level adjusting section 14 so that the television signal has a predetermined output level, and is then subjected to a third band-pass filter (BPF3) 15. Supplied to The television signal from which the unnecessary band has been removed by the third band-pass filter 15 is output through the splitter 16 so as to be retransmitted. The branch signal branched by the branch unit 16 is supplied to the third mixer (MIX3) 18 and down-converted by the local oscillation signal selected by the switch SW1. Then, the down-converted television signal is supplied to a fourth band-pass filter (BPF).
4) supplied to 19 and a fifth bandpass filter (BPF5) 20; The video signal is extracted by the fourth bandpass filter 19, and the extracted video signal is detected by the diode D 1 and supplied to the video level display unit 21. The audio signal extracted by the fifth bandpass filter 20 is detected by the diode D2 and supplied to the audio level display unit 22. By observing the level of the video signal displayed on the video level display section 21 and the level of the audio signal displayed on the audio level display section 22, the levels of the video signal and the audio signal of the retransmitted television signal are observed. And the VA ratio can be monitored.

Since the second mixer 12 and the third mixer 18 are supplied with local signals of the same frequency,
Regardless of whether the movable contact a of the switch SW1 is switched to the fixed contact c or the fixed contact b, the third mixer 18
, The frequency of the signal down-converted becomes the intermediate frequency. Thereby, even if the channel of the input television signal is converted into an arbitrary channel and output, the third mixer 18 down-converts the signal to the same intermediate frequency as the intermediate frequency output from the first mixer 3. TV signals are output. That is, the third mixer 18 outputs a television signal having a constant frequency, regardless of which channel the television retransmission device is retransmitting. Therefore, it suffices to monitor the intermediate frequency television signal which is a fixed frequency. And audio signals can be extracted. Since the intermediate frequency is a low frequency, the fourth band-pass filter 19 and the fifth band-pass filter 2
0 can be constituted by a generally used inexpensive SAW filter or the like.

When adjusting the retransmitted television signal as described above, first, the video level display unit 21
The output level is adjusted by adjusting the high-frequency amplification output level adjustment unit 14 while observing the level of the video signal displayed on the screen. Next, by adjusting the audio level adjustment unit 11 while observing the level of the audio signal displayed on the audio level display unit 22, the VA ratio is adjusted to a predetermined value. In this case, in order to prevent the audio signal from interfering with the video signal of the adjacent channel, it is preferable to attenuate the audio signal with respect to the video signal by approximately -9 dB or more. However, if the audio signal is attenuated by -14 dB or more, the audio signal is degraded. Therefore, it is preferable that the audio signal be adjusted to be in a range of approximately -9 dB to -14 dB with respect to the video signal. In addition, as an example of the configuration of the video level display section 21 and the audio level display section 22, the A / D converter converts a detection output into a digital signal and a display driven by the converted digital signal. You.

Next, FIG. 2 shows the configuration of a second embodiment of the television retransmitting apparatus provided with the monitoring circuit of the present invention. In FIG. 2, a television signal received by an antenna or the like is input to a channel selection unit 51, and a television signal of any selected channel is output to a high-frequency amplifier 52. The high frequency amplifier 52 amplifies the television signal of the selected channel and supplies it to the first mixer (MIX1) 53.

The first mixer 53 is supplied with a first local oscillation signal oscillated by a first local oscillator 54 composed of a variable frequency oscillator, and converts a television signal of a selected channel into an intermediate frequency. . The frequency of the first local oscillation signal is set to a frequency at which the frequency of the selected channel can be converted to an intermediate frequency. The television signal of the selected channel converted to the intermediate frequency is amplified by an intermediate frequency amplifier (IF amplifier) 55, and its output is supplied to a first bandpass filter (BPF1) 56 and a second bandpass filter (BPF1) 56.
It is supplied to a bandpass filter (BPF2) 59. The first band pass filter 56 extracts a video signal,
The video signal is supplied to the combining unit 57. Further, the extracted video signal is supplied to an AGC circuit 67, where an AGC signal is generated based on the level of the video signal, the amplification of the high frequency amplifier 52 and the intermediate frequency amplifier 55 is controlled, and a squelch described later is used. The circuit 58 is controlled.

The second band-pass filter 59 extracts an audio signal, removes noise components of the audio signal that has been frequency-modulated by the limiter 60, makes the audio signal have a constant amplitude, and supplies it to the audio level adjusting unit 61. Is done. The audio level adjustment unit 61 adjusts the level of the audio signal with respect to the video signal. That is, when adjacent channel transmission is performed, V (Video) / A (V (Video) / A
(Audio) ratio is adjusted. Since the VA ratio is a ratio, the audio signal is, for example, -9 dB with respect to the video signal.
The level of the audio signal is adjusted by the audio level adjustment unit 61 so that the signal is attenuated by -14 dB, so that the video signal of the adjacent channel is not disturbed. At this time,
A DC adjustment voltage for adjusting the level is output from the audio level adjustment unit 61 and supplied to the audio level display unit 71. The level-adjusted audio signal is supplied to the synthesizing unit 5.
7 and is combined with the video signal extracted by the first bandpass filter 56 and recombined into a television signal.

The recombined television signal output from the synthesizing section 57 is supplied to a squelch circuit 58, and is output as it is if the signal level input to the squelch circuit 58 is equal to or higher than a threshold. When the signal level is lower than the threshold, the input signal is blocked. The output of the squelch circuit 58 is input to a second mixer (MIX2) 62, and is up-converted by a local oscillation signal selected by the switch SW1, and is up-converted to a predetermined channel frequency. Switch S
W1 is a first local oscillation signal oscillated by the first local oscillator 54,
Further, any one of the second local oscillation signals oscillated by the second local oscillator 63 can be selected. Here, in the case of a television signal of the same channel as the input channel, the first local oscillator signal oscillated by the first local oscillator 54 is selected by the switch SW1, and the television signal of the original channel is selected by the second mixer 62. Is frequency-converted. When transmitting on a different channel, the second local oscillator 63 oscillates by the switch SW1.
The local oscillator signal is selected and frequency-converted by the second mixer 62 into a television signal of a desired channel.

The high-frequency television signal output from the second mixer 62 is amplified by a high-frequency amplification output level adjustment unit 64 so that the television signal has a predetermined output level, and a third band-pass filter (BPF3) 65 is provided. Supplied to The television signal from which the unnecessary band has been removed by the third band-pass filter 65 is output through the splitter 66 so as to be retransmitted. Further, the branch signal branched by the branch unit 66 is supplied to the third mixer (MIX3) 68 and down-converted by the local signal selected by the switch SW1. Then, the down-converted television signal is supplied to a fourth band-pass filter (BPF4).
69. The fourth bandpass filter 69 extracts a video signal, and the extracted video signal is supplied to a video level display unit 70. By observing the level of the video signal displayed on the video level display unit 70 and the level of the audio signal displayed on the audio level display unit 71,
The level and the VA ratio of the video signal and the audio signal of the retransmitted television signal can be monitored.

Since the second mixer 62 and the third mixer 68 are supplied with local signals of the same frequency,
Regardless of whether the movable contact a in the switch SW1 is switched to the fixed contact c or the fixed contact b, the third mixer 68
, The frequency of the signal down-converted becomes the intermediate frequency. Accordingly, even if the channel of the input television signal is converted into an arbitrary channel and output, the third mixer 68 down-converts the signal to the same intermediate frequency as the intermediate frequency output from the first mixer 53. TV signals are output. That is, the third mixer 68 outputs a television signal of a constant frequency, regardless of which channel the television retransmission device is retransmitting. Therefore, it suffices to monitor the television signal of the intermediate frequency, which is a fixed frequency, and the video signal can be extracted by preparing only one kind of band-pass filter as the fourth band-pass filter 69. Become like Further, since the intermediate frequency is a low frequency, the fourth band-pass filter 69 can be constituted by a generally used inexpensive SAW filter or the like.

When adjusting the retransmitted television signal as described above, first, the video level display unit 70
The output level is adjusted by adjusting the high-frequency amplification output level adjustment unit 64 while observing the level of the video signal displayed on the screen. Next, by adjusting the audio level adjustment unit 61 while observing the level of the audio signal displayed on the audio level display unit 71, the adjustment is performed so that the VA ratio becomes a predetermined value. In this case, in order to prevent the audio signal from interfering with the video signal of the adjacent channel, it is preferable to attenuate the audio signal with respect to the video signal by approximately -9 dB or more. However, if the audio signal is attenuated by -14 dB or more, the audio signal is degraded. Therefore, it is preferable that the audio signal be adjusted to be in a range of approximately -9 dB to -14 dB with respect to the video signal.

Next, one configuration of the video level display section 70 is shown in FIG. Here, if the video signal is simply detected and the level of the video signal is detected based on the detection output,
Since the video signal is AM-modulated, the amplitude varies depending on the picture, and the video signal level cannot be detected accurately. The solution was to solve this
This is a video level display unit 70 shown in FIG. 3, and this video level display unit 70 is a video demodulation circuit 7 incorporating an AGC circuit.
Using 0-1, the level of the video signal is detected based on the AGC signal. Hereinafter, the description will be made.

In FIG. 3, the video signal separated by the fourth band pass filter (BPF4) 69 is supplied to a video demodulation circuit 70-1 and demodulated by the video demodulation circuit 70-1. The AGC signal output at that time becomes a signal proportional to the level of the input video signal, and is supplied to the A / D converter 70-2 to be converted into a digital signal. This digital signal is supplied to the decoder 7
0-3, the digital signal is decoded, and a plurality of light emitting diodes LED are decoded according to the digital value.
1 to LEDn are turned on. In this case, the light-emitting diodes LED1 to LEDn are arranged so as to display a numerical value of seven segments or a bar. In this case, if the A / D converter 70-2 is of a parallel comparison type when the light emitting diodes LED1 to LEDn have a bar display configuration, the light emitting diodes LED1 to LEDn can be directly driven. -3 can be omitted. It should be noted that the video demodulation circuit 70-1 can be constituted by a general demodulation IC which is inexpensively supplied to the market. Also, the video level display unit 7 shown in FIG.
0 can be used instead of the diode D1 and the video level display unit 21 in FIG.

Next, detailed circuits of the audio level adjusting section 61 and the audio level display section 71 are shown in FIG. In FIG. 4, an audio signal output from a limiter 60 is input to an audio level adjusting unit 61, and a capacitor C connected in cascade.
1, a capacitor C2 and a PI acting as a damping resistor
Synthesizing circuit 5 via N diode D3 and capacitor C3
7 is output. The capacitors C1 and C
2, a PIN diode D1 and a PIN diode D2 are cascaded. Further, the anode of the PIN diode D1 is connected to the power supply Vcc via the resistor R1, and the cathode of the PIN diode D2 is connected to the ground via the resistor R4. The connection point between the PIN diode D1 and the PIN diode D2 is a capacitor C
4 is grounded.

A bias voltage Vb divided by a variable resistor R2 is applied to a connection point between the capacitor C2 and the PIN diode D3. The bias voltage Vb is applied to a voice signal via a choke coil L1 and a resistor R3. It is extracted as a DC voltage Va representing a level. Further, the audio level display section 71 includes an A / D converter 71-1 for converting the DC voltage Va into a digital signal, and a decoder 71-2 for decoding the converted digital signal so that the display device 71-3 can be driven. , And a display device 71-3 for displaying the DC voltage Va in numerical display or bar display.

Next, the operation of the configuration shown in FIG. 4 will be described. The PIN diode D1, PIN diode D2 and PIN diode D3 constitute a π-type attenuator. At this time, the capacitor C4 grounds the audio signal in an AC manner. Here, assuming that the bias voltage Vb is increased by changing the variable resistor R2, the forward bias voltage applied across the PIN diode D3 increases, and the equivalent resistance of the PIN diode D3 decreases.
Since the voltage drop of the resistor R4 increases, the equivalent resistance of the PIN diodes D1 and D2 increases. As a result, the audio signal input via the capacitors C1 and C2 has a reduced attenuation amount and is output via the capacitor C3. If the variable resistor R2 is varied to lower the bias voltage Vb, the forward bias voltage applied to both ends of the PIN diode D3 decreases,
The resistance of PIN diode D3 increases while resistance of R4
Is small, the PIN diodes D1, P
The equivalent resistance of the IN diode D2 decreases. As a result, the audio signal input via the capacitors C1 and C2 is further attenuated and output via the capacitor C3. Thus, the level of the audio signal is adjusted according to the bias voltage Vb.

The audio signal of the bias voltage Vb is blocked by the choke coil L1 and A / A
The signal is supplied to the D converter 71-1 and is converted into a digital signal. The converted digital signal is displayed on the display device 71-3.
Are decoded by the decoder 71-2 so that the analog DC voltage Va can be numerically displayed or displayed as a bar on the display device 71-3. The display device 71-3
Is a bar display configuration, the A / D converter 71
If -1 is a parallel comparison type, the display device 71-3 can be driven directly, and the decoder 71-2 can be omitted.

As described above, the audio level adjuster 61 adjusts the bias voltage Vb so that the audio level does not interfere with the video signal of the adjacent channel.
In this case, the ratio of the power of the video signal to the power of the audio signal of the television signal in Japan is 4: 1, that is, the audio signal is a signal that is a relative value to the video signal and is attenuated by 6 dB from the video signal. As described above, the V / A ratio of the television signal input to the television retransmission device is approximately -6 dB. Further, since the audio signal has a constant amplitude by the limiter 60, the level of the audio signal input to the audio level adjustment unit 61 can be assumed to be attenuated by -6 dB from the video signal. Therefore, PI
When the attenuation of the π-type attenuator including the N diode D1, the PIN diode D2, and the PIN diode D3 is set to the minimum (attenuation “0 dB”), the VA ratio is “−6 dB” in the display device 71-3. The display device 71-3 is set to be displayed. FIG.
The configuration of the audio level display section 71 shown in FIG. 1 can also be used as the audio level display section 22 shown in FIG.

[0038]

As described above, according to the present invention, the output television signal is down-converted by the local oscillation signal supplied to the second conversion means. As a result, the frequency is converted to a fixed intermediate frequency. Therefore, a video signal and an audio signal are converted from a television signal converted to a fixed intermediate frequency into a general SAW (Surface Acoustic Wav).
e) Separation can be easily performed using a band-pass filter such as a filter.

Since the down-converted intermediate frequency is always a constant frequency irrespective of the output channel value, the detection characteristics of the diode for detecting the separated video signal and audio signal require wide band characteristics. Will not be. Furthermore, if the level of the video signal is detected based on the AGC signal in the video demodulation circuit, the level does not fluctuate due to the picture, and the level of the video signal can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a first embodiment in a television retransmission device including a monitoring circuit of the present invention.

FIG. 2 is a diagram illustrating a configuration of a second embodiment in a television retransmission device including a monitoring circuit of the present invention.

FIG. 3 is a diagram illustrating one configuration of a video level display unit in a television retransmission device including the monitoring circuit of the present invention.

FIG. 4 is a diagram showing one configuration of an audio level adjustment unit and an audio level display unit in a television retransmitting device including the monitoring circuit of the present invention.

FIG. 5 is a diagram illustrating one configuration of a television retransmission device including a conventional monitoring circuit.

[Explanation of symbols]

1,51 channel tuning section 2,520 high frequency amplification section 3,12,18,53,62,68 mixer 4,54 first local oscillator 5,55 IF amplifier 6,9,19,20,56,59,65 band Pass filter 7, 57 Synthesis unit 8, 58 Squelch circuit 10, 60 Limiter 11, 61 Audio level adjustment unit 13, 63 Second local oscillator 14, 64 High frequency amplification output level adjustment unit 16, 66 Branch unit 17, 67 AGC circuit 21 , 70 Video level display unit 22, 71 Audio level display unit

Claims (4)

(57) [Claims] 1. An input high-frequency television signal is transmitted to a first
First conversion means for converting into an intermediate frequency television signal by a first local oscillation signal from a local oscillator, separating an audio signal from the intermediate frequency television signal,
Audio level adjusting means for adjusting the level of the separated audio signal; and selecting and outputting any one of a first local signal from the first local oscillator and a second local signal from the second local oscillator. Selecting means for synthesizing the audio signal whose level has been adjusted by the audio level adjusting means and the video signal separated from the intermediate frequency television signal, and then outputting a high-frequency television signal based on a local signal output from the selecting means. Second converting means for converting the signal into a signal, high-frequency output level adjusting means for adjusting an output level of a high-frequency television signal output from the second converting means, and a high-frequency output level adjusted by the high-frequency output level adjusting means. Third conversion means for down-converting the branch output of the television signal by a local signal output from the selection means, and a down-converter output from the third conversion means. A monitoring circuit, characterized by comprising: level converting means for separating the converted television signal into a video signal and an audio signal by a filter means, and displaying the levels of the separated video signal and audio signal, respectively. Television retransmission device comprising: 2. The level display means, wherein the separated video signal is supplied to a video signal demodulation circuit, and the level of the video signal is supplied to an AG output from the video video signal demodulation circuit.
The television retransmitting device provided with the monitoring circuit according to claim 1, wherein the detection is performed based on a level of the C signal. 3. The input high-frequency television signal is transmitted to a first
First conversion means for converting into an intermediate frequency television signal by a first local oscillation signal from a local oscillator, separating an audio signal from the intermediate frequency television signal,
Audio level adjusting means for adjusting the level of the separated audio signal; and selecting and outputting any one of a first local signal from the first local oscillator and a second local signal from the second local oscillator. Selecting means for synthesizing the audio signal whose level has been adjusted by the audio level adjusting means and the video signal separated from the intermediate frequency television signal, and then outputting a high-frequency television signal based on a local signal output from the selecting means. Second converting means for converting the signal into a signal, high-frequency output level adjusting means for adjusting an output level of a high-frequency television signal output from the second converting means, and a high-frequency output level adjusted by the high-frequency output level adjusting means. Third conversion means for down-converting the branch output of the television signal by a local signal output from the selection means, and a down-converter output from the third conversion means. A video level display unit that separates a video signal from the converted television signal by a filter unit and displays a level of the separated video signal; and, in the audio level adjustment unit, based on a level of an adjustment signal for adjusting an audio level. And a sound level display means for displaying the level of the sound signal. 4. The video level display means supplies the separated video signal to a video signal demodulation circuit, and detects the level of the video signal based on the level of an AGC signal output from the video signal demodulation circuit. A television retransmitting device comprising the monitoring circuit according to claim 3.