JP2007195123A - Monitor circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate an influence of a high frequency signal which is not measured among a plurality of high frequency signals. <P>SOLUTION: This monitor circuit 34 provided in an amplifier which amplifies a high frequency signal at a low noise level of a first frequency band and a high frequency signal at a high noise level of a second frequency band different from the first frequency band has a first branching device 36 to which the high frequency signals of the first and second frequency bands are supplied and a low-pass filter 40 which eliminates the high frequency signal of the second frequency band and a monitor terminal 42. A changeover switch 39 switches a state that a branching signal of the one branching device 36 passing through the low-pass filter 40 is supplied to the monitor terminal 42 to a state that the branching signal of the one branching device 36 is supplied to the monitor terminal as it is and vice versa. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a monitor circuit provided in an amplifier, and more particularly to an amplifier monitor circuit that amplifies a plurality of high-frequency signals in different frequency bands.

  An amplifier provided with a monitor circuit may be used, for example, as a relay amplifier in a joint reception system. An example of this relay amplifier is disclosed in Patent Document 1. In the relay amplifier of Patent Document 1, a branching device is provided on the output side of an amplifier that amplifies a television broadcast signal of each channel. The output signal of the branching device is supplied to the output terminal of the relay amplifier as the output of the relay amplifier. The branch signal of the branching device is supplied to the monitor terminal of the relay amplifier, and is supplied from this monitor terminal to the spectrum analyzer. A changeover switch and a pseudo transmission line are provided between the branch terminal and the monitor terminal of the branching device. The pseudo transmission network has a frequency characteristic opposite to the frequency characteristic of the branch signal of each channel. The changeover switch is switched between a state in which the pseudo transmission network is connected between the branch terminal and the monitor terminal and a state in which the branch signal is supplied to the monitor terminal as it is.

JP-A-8-18944

  In this relay amplifier, in a state where the pseudo transmission network is connected between the monitor terminal and the branch terminal of the branching device, for example, the branch signal of each channel having a tilt characteristic whose level increases as the frequency increases, By letting it pass, the tilt characteristic can be canceled, and the level deviation of the signal of each channel and the variation of the signal can be confirmed by the spectrum analyzer.

  By the way, the relay amplifier may amplify high frequency signals in different frequency bands. For example, UHF band and VHF band television broadcast signals and satellite broadcast and satellite communication intermediate frequency signals (satellite broadcast signals and satellite communication signals received by an antenna are converted into 1 GHz band intermediate frequency signals by a converter attached to the antenna. May be amplified). In this case, the UHF band and VHF band television broadcast signals include low noise levels, but satellite broadcast and satellite communication intermediate frequency signals include high noise levels and high total power. Therefore, for example, when a measuring instrument is connected to a monitor terminal to measure a television broadcast signal in the UHF band and the VHF band, an intermediate frequency signal for satellite broadcasting and satellite communication is also supplied to the measuring instrument, and the influence thereof. As a result, the measuring instrument becomes over-input, and it becomes impossible to accurately measure television broadcast signals in the UHF band and the VHF band.

  An object of this invention is to provide the monitor circuit which can remove the influence of the high frequency signal which is not measured among several high frequency signals.

  The monitor circuit of one embodiment of the present invention includes a high-frequency signal having a low noise level in the first frequency band and a high-frequency signal having a high noise level in a second frequency band that is a frequency band different from the first frequency band. It is provided in the amplifier to amplify. The amplifier is provided with an amplification stage for amplifying the high-frequency signal in the first frequency band and an amplification stage for amplifying the high-frequency signal in the second frequency band, and synthesizes the output signals of these amplification stages. It is also possible to use a wideband amplifier that amplifies all high-frequency signals in the first and second frequency bands. Branch means for supplying high-frequency signals in the first and second frequency bands is provided. This branching means can be provided on the output side of the amplifier, can be provided on the input side of the amplifier, or can be provided in an intermediate stage when the amplifier is composed of a plurality of amplification stages. A filter having a frequency characteristic for removing a high-frequency signal in the second frequency band and a monitor terminal are provided. A state selected from a first state in which the branch signal of the branching means that has passed through the filter is supplied to the monitor terminal and a second state in which the branch signal of the branching means is supplied to the monitor terminal as it is The switching means switches to.

  In the monitor circuit configured as described above, when the high-frequency signal in the first frequency band is measured, the switching unit is switched to the first state. As a result, the high-frequency signal in the second frequency band is removed, and only the high-frequency signal in the first frequency band is supplied to the monitor terminal. Therefore, when measuring a high-frequency signal in the first frequency band, it is not affected by the high-frequency signal in the second frequency band. Further, when measuring the high frequency signal in the second frequency band, the switching means is switched to the second state. As a result, both the high frequency signals in the first and second frequency bands are supplied to the measuring instrument via the monitor terminal. However, since the high frequency signal in the first frequency band has a low noise level, this is supplied to the measuring instrument. However, the measurement of the high frequency signal in the second frequency band is not affected.

  The output side of the filter is connected to the monitor terminal, and the switching means is configured to supply the branch signal of the branch means to the filter in the first state and to the monitor terminal in the second state. You can also For example, the branch signal is supplied to the input side of the filter, and in the first state, the switching means supplies the output signal of the filter to the monitor terminal, and in the second state, the branch signal is supplied to the monitor terminal. In this case, in the first state, a high-frequency signal in the second frequency band may leak from the transmission line formed from the branch terminal of the branching device to the switching unit. On the other hand, as described above, if the switching means supplies the branch signal of the branch means to the filter in the first state, the transmission path from the branch terminal to the monitor terminal of the branch means is The first and second high-frequency signals do not flow and do not leak, and the second high-frequency signal does not affect the measurement.

  The high frequency signal in the first frequency band is at least one of the television broadcast signals in the UHF band and the VHF band, and the high frequency signal in the second frequency band is at least one of the intermediate frequency signals of the satellite broadcast and the satellite communication signal. You can also There may be a difference in noise level among other high frequency signals in a plurality of frequency bands, but at least one of the UHF band and VHF band television broadcast signals and the intermediate frequency signals of the satellite broadcast and satellite communication signals. In the case of at least one of them, when measuring at least one of the UHF band and VHF band television broadcast signals, it is susceptible to at least one of the intermediate frequency signals of the satellite broadcast and the satellite communication signal. The effect of the invention becomes remarkable.

  Further, the filter may be a low-pass filter in which the first frequency band is in the pass band and the second frequency band is in the cutoff band. For example, a band removal filter that removes the second frequency band can be used, but the configuration of the low-pass filter is simpler than that of the band-pass filter, and the cost can be reduced.

  As described above, according to the present invention, when measuring a high-frequency signal in one frequency band among a plurality of high-frequency signals in different frequency bands, the influence of the high-frequency signal in another frequency band can be removed. .

  The monitor circuit of one embodiment of the present invention is implemented in a relay amplifier that is interposed in the transmission line of the joint reception system as shown in FIG. This relay amplifier amplifies a television broadcast signal in a first frequency band, for example, UHF band and VHF band, and a satellite broadcast and satellite communication intermediate frequency signal in a second frequency band, for example, 1 GHz band. Television broadcast signals in the UHF band and the VHF band are received by the receiving antennas in the UHF band and the VHF band at the head end of the joint reception system, and transmitted to the transmission path of the joint reception system. The satellite broadcast and satellite communication intermediate frequency signal is generated by frequency-converting the satellite broadcast and satellite communication signal received by the satellite broadcast and satellite communication receiving antenna at the head end with a converter attached to the satellite broadcast and satellite communication receiving antenna. And transmitted to the transmission line of the joint reception system.

  In some cases, UHF band and VHF band television broadcast signals are supplied to the input terminal 2 of the relay amplifier, and satellite broadcast and satellite communication intermediate frequency signals are supplied to the input terminal 4 of the relay amplifier. In addition, a mixed signal of a UHF band and a VHF band television broadcast signal and a satellite broadcast and satellite communication intermediate frequency signal may be supplied to the input terminal 4. When the UHF band and VHF band television broadcast signals are supplied to the input terminal 2, the UHF band and VHF band television broadcast signals are supplied to the duplexer 8 via the input switching circuit 6, and the UHF band television is transmitted. The signal is demultiplexed into a John broadcast signal and a VHF band television broadcast signal. When the mixed signal is supplied to the input terminal 4, the mixed signal is demultiplexed into a UHF band and VHF band television broadcast signal and a satellite broadcast and satellite communication intermediate frequency signal by the demultiplexer 7. The UHF band and VHF band television broadcast signals are supplied to the duplexer 8 via the input switching circuit 6. The demultiplexer 8 demultiplexes the UHF band television broadcast signal and the VHF band television broadcast signal.

  The demultiplexed UHF band television broadcast signal is attenuated by a predetermined amount by an attenuator, for example, an attenuator 10, and then amplified by the variable gain amplifier 12. The variable gain amplifier 12 includes two amplification stages 12a and 12b connected in cascade, and gain adjusting means, for example, a gain control circuit 12c, connected between them. A manual circuit can be used as the gain control circuit 12c.

  The VHF band television broadcast signal demultiplexed by the demultiplexer 8 is demultiplexed by the demultiplexer 9 into a VHF band high frequency television broadcast signal and a VHF band low frequency television broadcast signal.

  The VHF band high frequency television broadcast signal is attenuated by a predetermined amount by the attenuator 14 and then amplified by the variable gain amplifier 16. Similar to the variable gain amplifier 12, the variable gain amplifier 16 also includes amplification stages 16a and 16b and a gain control circuit 16c.

  The VHF band low-frequency television broadcast signal is supplied to the attenuator 20 via the FM switching circuit 18, attenuated by a predetermined amount, supplied to the variable gain amplifier 22, and amplified. Similarly to the variable gain amplifier 12, the variable gain amplifier 22 includes amplification stages 22a and 22b and a gain control circuit 22c.

  The VHF band high frequency television broadcast signal amplified by the variable gain amplifiers 16 and 22 and the VHF band low frequency television broadcast signal are mixed by the mixer 24 to obtain a mixed VHF band television broadcast signal. The mixed VHF band television broadcast signal and the UHF band television broadcast signal amplified by the variable gain amplifier 12 are mixed by the mixer 26 to obtain a mixed UHF band and VHF band television broadcast signal.

  The satellite broadcast and satellite communication intermediate frequency signals demultiplexed by the demultiplexer 7 are attenuated by a predetermined amount by the attenuator 28 and then amplified by the variable gain amplifier 30. Similar to the variable gain amplifier 12, the variable gain amplifier 30 includes two amplification stages 30a and 30b and a gain control circuit 30c, and also includes a tilt circuit 30d cascaded with the gain control circuit 30c. .

  The satellite broadcast and satellite communication intermediate frequency signals amplified in the variable gain amplifier 30 are mixed with the mixed UHF band and VHF band television broadcast signals from the mixer 26 in the mixer 32 and supplied to the monitor circuit 34.

  The monitor circuit 34 includes a branching unit, for example, one branching unit 36, and a mixed signal of the satellite broadcast and satellite communication intermediate frequency signal from the mixer 32 and the UHF band and VHF band television broadcast signal is supplied to the input side thereof. ing. The output of the one branching device 36 is supplied to an output terminal 38.

  The branch output of the one branching device 36 is supplied to switching means, for example, a contact point 39e of the changeover switch 39. The contacts 39 a and 39 b of the changeover switch 39 are connected to a filter, for example, a low-pass filter 40, and a contact 39 f of the changeover switch 39 is connected to the monitor terminal 42. The cutoff frequency of the low-pass filter 40 is selected so as to allow the UHF band and VHF band television broadcast signals to pass through and to block the satellite broadcast and satellite communication intermediate frequency signals. A line 41 short-circuits the contacts 39g and 39h of the changeover switch 39 with which the contacts 39a and 39b can contact. Accordingly, in the first state in which the contacts 39e and 39c are connected via the contact 39a and the contacts 39d and 39f are connected via the contact 39b, the satellite broadcast and satellite communication intermediate frequency generated on the branch side of the one branching device 36 is obtained. From the mixed signal of the signal and the UHF band and VHF band television broadcast signal, the satellite broadcast and satellite communication intermediate frequency signals are blocked by the low-pass filter 40, and the UHF band and VHF band television broadcast signals are extracted, and the monitor terminal 42 is extracted. To be supplied. In the second state in which the contacts 39e and 39g are connected via the contact 39a and the contacts 39d and 39f are connected via the contact 39b, the satellite broadcast and satellite communication intermediate frequency generated on the branch side of the one branching device 36. The mixed signal of the signal and the UHF band and VHF band television broadcast signal is supplied to the monitor terminal 42 as it is. The contact points 39g and 39h of the changeover switch 39 are short-circuited by the line 41 provided outside the changeover switch 39, but may be directly short-circuited inside the changeover switch 39.

  In general, UHF band and VHF band television broadcast signals are produced on the assumption that the UHF band and VHF band television broadcast signals have low noise levels, and the measuring instruments for measuring them are also low. Has been. On the other hand, the satellite broadcast and satellite communication intermediate frequency signals have a high noise level, and the total power is larger than the UHF band and VHF band television broadcast signals. Therefore, a measuring instrument for measuring UHF band and VHF band television broadcast signals in a state in which a mixed signal of UHF band and VHF band television broadcast signals and satellite broadcast and satellite communication intermediate frequency signals is supplied. For example, when a level measuring device is connected, the measuring device becomes over-input, and it becomes impossible to accurately measure television broadcast signals in the UHF band and the VHF band.

  Therefore, in the monitor circuit 34, when measuring the level of the UHF band and VHF band television broadcast signals, the contacts 39e and 39c are connected via the contact 39a of the changeover switch 39, and the contact 39b is connected. Switching to connect the contacts 39d and 39f, the UHF band and VHF band television signals are supplied to the monitor terminal 42 in a state where the satellite broadcast and satellite communication intermediate frequency signals are cut off, and the level is measured by the measuring instrument. Do. When measuring the level of satellite broadcasting and satellite communication intermediate frequency signals, the contacts 39e and 39g are connected via the contact 39a of the changeover switch 39, and the contacts 39f and 39h are connected via the contact 39b. Then, a mixed signal of the UHF band and VHF band television broadcast signal and the satellite broadcast and satellite communication intermediate frequency signal is supplied to the monitor terminal 42, and the level is measured by the measuring instrument.

  FIG. 2 is a frequency characteristic diagram measured at the monitor terminal 42 in a state where the contacts 39e and 39c are connected via the contact 39a of the changeover switch 39 and the contacts 39d and 39f are connected via the contact 39b. 3 is a frequency characteristic diagram measured at the monitor terminal 42 in a state where the contacts 39e and 39g are connected via the contact 39a of the changeover switch 39 and the contacts 39f and 39h are connected via the contact 39b. As is clear from the comparison between the two, in FIG. 2 in which the low-pass filter 40 is not used, the level at the frequency of about 1 GHz to about 1.9 GHz where the satellite broadcast and satellite communication intermediate frequency signals are present is in the UHF band and VHF. It is larger than the level at 50 MHz to about 800 MHz where a band television broadcast signal exists. Therefore, in this state, if the measuring instrument is connected to the monitor terminal 42 and the level of the UHF band and VHF band television broadcast signal is to be measured, as described above, the non-input state occurs. However, in the state of FIG. 3 that has passed through the low-pass filter 40, the level at a frequency of about 1 GHz to about 1.9 GHz is greatly attenuated, and is lower than the level of the UHF band and VHF band television broadcast signals. Therefore, even if the measuring device is connected to the monitor terminal 42 in this state and the levels of the UHF band and VHF band television broadcast signals are measured, the level measurement can be normally performed without being affected by excessive input. Can do.

  The output terminal 38 has a DC power source for operating the amplification stages 12a, 12b, 16a, 16b, 22a and 22b of the relay amplifier and for operating a converter for a satellite broadcasting and satellite communication receiving antenna. May be supplied. This DC power supply is connected to each amplification stage 12a, 12b, 16a, 16b, 22a, 22b via the one branching device 36 (therefore, the one branching device 36 is energized), the high frequency blocking coil 44 and the backflow prevention diode 46. And is further supplied to the input terminal 4 via the open / close switch 48 and the high frequency blocking coil 50. When the converter for the satellite broadcasting and satellite communication receiving antenna is operated by another power source, the open / close switch 48 is opened. In addition, a constant voltage unit 52 that stabilizes the commercial AC power supply by converting it to DC is provided in case no DC power is supplied from the output terminal 38. A DC blocking capacitor 54 is provided between the input terminal 4 and the duplexer 7.

  In the above embodiment, the low-pass filter 40 is used. However, a filter capable of removing satellite broadcast and satellite communication intermediate frequency signals may be used. For example, the frequency band of satellite broadcast and satellite communication intermediate frequency signals is cut off. It is also possible to use a band elimination filter having a band or a band pass filter having a UHF band and VHF band television broadcast signal as a pass band. In the above embodiment, UHF band and VHF band television broadcast signals are used as signals in the first frequency band, and satellite broadcast and satellite communication intermediate frequency signals are used as signals in the second frequency band. For example, a UHF band television broadcast signal may be used as the first frequency band signal, and a VHF band television broadcast signal may be used as the second frequency band signal.

It is a block diagram of the relay amplifier provided with the monitor circuit of one Embodiment of this invention. FIG. 4 is a frequency characteristic diagram measured at a monitor terminal 42 while switching contacts 39a and 39b of the changeover switch 39 to the second state in the relay amplifier of FIG. FIG. 4 is a frequency characteristic diagram measured at a monitor terminal 42 by switching contacts 39a and 39b of the changeover switch 39 to the first state in the relay amplifier of FIG.

Explanation of symbols

34 monitor circuit 36 1 branching device (branching means)
39 Changeover switch (switching means)
40 Low-pass filter (filter)

Claims (4)

A monitor circuit provided in an amplifier that amplifies a high-frequency signal having a low noise level in the first frequency band and a high-frequency signal having a high noise level in a second frequency band that is a frequency band different from the first frequency band. There,
Branching means to which high-frequency signals in the first and second frequency bands are supplied;
A filter having frequency characteristics for removing high-frequency signals in the second frequency band;
A monitor terminal;
A state selected from a first state in which the branch signal of the branching means that has passed through the filter is supplied to the monitor terminal and a second state in which the branch signal of the branching means is supplied to the monitor terminal as it is Switching means for switching to
Monitor circuit provided.   2. The monitor circuit according to claim 1, wherein an output side of the filter is connected to the monitor terminal, and the switching unit supplies a branch signal of the branch unit to the filter in a first state, and a second state. A monitor circuit for supplying to the monitor terminal.   2. The monitor circuit according to claim 1, wherein the high frequency signal of the first frequency band is at least one of television broadcast signals of UHF band and VHF band, and the high frequency signal of the second frequency band is satellite broadcast and satellite communication signal. A monitor circuit that is at least one of the intermediate frequency signals.   4. The monitor circuit according to claim 3, wherein the filter is a low-pass filter having a first frequency band in a pass band and a second frequency band in a cutoff band.

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