JP7088998B2 - Signal measuring instrument - Google Patents

Description

The present invention relates to a signal measuring instrument.

Conventionally, a broadcast wave transmission system via an optical signal is known. In this broadcast wave transmission system, for example, broadcast signals of a plurality of channels are supplied to a transmitter from an antenna, a coaxial cable, or the like. The transmitter converts a broadcast band signal including a modulated broadcast signal in which each broadcast signal is intensity-modulated into an optical signal, and outputs the optical signal to an optical transmission line.

Here, the modulation degree of the modulated broadcast signal is the amplitude ratio of the broadcast signal and the carrier signal thereof. The larger the modulation degree value, the larger the amplitude of the modulated broadcast signal, and the better the intelligibility (signal quality). However, if the degree of modulation exceeds 100%, overmodulation occurs and the waveform of the broadcast signal after demodulation is distorted. Therefore, on the transmitter side, not only the modulation degree of each modulated broadcast signal but also the modulation degree of the optical signal (in other words, the broadcast band signal on the receiving side) is modulated to the extent that the modulation degree of each modulated broadcast signal is not overmodulated. It is necessary to set the degree and limit the number of channels included in the broadcast band signal.

On the transmitter side, a uniform modulation degree of the modulated broadcast signal is set so that the modulation degree of the broadcast band signal is lower than 100% with a margin. On the receiving side, the degree of modulation of the electric signal (that is, the broadcast band signal) obtained by photoelectrically converting the optical signal is measured each time the setting is made, for example, by the method shown in Patent Document 1, and it is confirmed whether or not the signal is overmodulated.

Japanese Unexamined Patent Publication No. 10-51394

However, Patent Document 1 only discloses measuring the degree of modulation of an electric signal obtained by photoelectrically converting an optical signal, and does not assume that the electric signal includes a plurality of broadcast signals. Therefore, even if the method of Patent Document 1 is adopted, the modulation degree and the number of channels of the modulated broadcast signal on the transmitter side cannot be easily grasped. Therefore, it has been difficult to increase the degree of modulation of each modulated broadcast signal as much as possible or to increase the number of channels included in the broadcast band signal as much as possible so that the broadcast band signal on the receiving side does not become overmodulated.

In view of the above situation, it is an object of the present invention to provide a signal measuring instrument capable of more appropriately setting the modulation degree and the number of channels of a modulated broadcast signal on the transmitter side.

In order to achieve the above object, the signal measuring instrument according to one aspect of the present invention includes an extraction unit that extracts the modulated broadcast signal from a broadcast band signal including a plurality of modulated broadcast signals in which the broadcast signal of each channel is intensity-modulated. The first calculation unit that calculates the first modulation degree of each of the modulated broadcast signals based on the signal level of the modulated broadcast signal, and the first modulation degree of all the modulated broadcast signals included in the broadcast band signal. Based on the above, the configuration includes a second calculation unit for calculating the second modulation degree of the broadcast band signal (first configuration).

The signal measuring instrument having the first configuration further includes a photoelectric conversion unit that converts an optical signal transmitted via an optical transmission path into an electrical signal, and the electrical signal includes the broadcast band signal (second configuration). The configuration of) may be used.

The signal measuring instrument having the second configuration may further include a light intensity detection unit that detects the light intensity of the optical signal based on the electric signal (third configuration).

In the signal measuring instrument having any of the first to third configurations, the broadcast band signal is at least one of a CATV band signal having a CATV band frequency and a satellite broadcast band signal having a satellite broadcast band frequency. It may be a configuration including (fourth configuration).

The signal measuring instrument having any of the first to fourth configurations further includes a demodulation unit that demodulates the modulated broadcast signal into the broadcast signal, and a signal quality calculation unit that calculates the signal quality of the broadcast signal. It may be a configuration (fifth configuration).

In the signal measuring instrument having the fifth configuration, the signal quality may be configured to include at least one of CNR, BER, and MER (sixth configuration).

In the signal measuring instrument having any one of the first to sixth configurations, the signal measuring instrument may have a portable configuration (seventh configuration).

According to the present invention, it is possible to provide a signal measuring instrument capable of more appropriately setting the modulation degree and the number of channels of the modulated broadcast signal on the transmitter side.

It is a block diagram which shows the configuration example of a broadcast wave transmission system. It is a front view of a signal measuring instrument. It is a block diagram which shows the structural example of a signal measuring instrument.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Broadcast wave transmission system>
The broadcast wave transmission system 200 is an optical communication system such as FTTH (Fiber To The Home), and transmits an optical signal output from a transmitter 220 to each receiver via an optical fiber. The broadcast wave transmission system 200 is installed in, for example, a detached house or an apartment house.

FIG. 1 is a block diagram showing a configuration example of a broadcast wave transmission system 200. In FIG. 1, the broadcast wave transmission system 200 outputs a CATV broadcast signal and a satellite broadcast signal to, for example, a television receiver in each home by using an optical signal. In the following, the television receiver will be referred to as a "TV device 400".

As shown in FIG. 1, the broadcast wave transmission system 200 includes a channel processor 210, a transmitter 220, an optical transmission line 230, and a V-ONU (Video Optical Network Unit) 240.

A CATV broadcast reception signal is input to the channel processor 210, for example, through a coaxial cable (reference numeral omitted). Further, a received signal of the satellite broadcast wave is input from the satellite broadcast receiving antenna 300. In the present embodiment, the satellite broadcast wave received by the satellite broadcast receiving antenna 300 includes a BS (broadcasting satellite) broadcast wave and a CS (communications satellite) broadcast wave. Further, the BS broadcast wave and the CS broadcast wave include a right-handed circularly polarized wave and a left-handed circularly polarized wave, respectively. The broadcast signal of each channel included in the received signals of CATV broadcasting and satellite broadcasting is an intensity-modulated signal. Hereinafter, the intensity-modulated broadcast signal is referred to as a “modulated broadcast signal”, and the modulation degree of the intensity-modulated signal is referred to as a “modulation degree”.

The channel processor 210 selects the CATV broadcast and satellite broadcast channels to be transmitted to the TV device 400 from the received signals of the CATV broadcast and satellite broadcast. The channel can be selected, for example, based on the operation input in the operation unit (not shown) of the channel processor 210. The channel processor 210 further mixes all the selected modulated broadcast signals and outputs them to the transmitter 220. In the following, a signal including all the selected modulated broadcast signals will be referred to as a broadcast band signal.

The transmitter 220 has a booster 221 and an E / O converter 222. The booster 221 amplifies the broadcast band signal. Further, the E / O converter 222 converts the broadcast band signal into an optical signal. The optical signal is a laser beam having a wavelength of 1578 nm in the present embodiment, and is output from an optical output terminal (not shown) to an optical transmission line 230.

The E / O converter 222 determines the signal strength of the modulated broadcast signal of each channel included in the amplified broadcast band signal based on the operation input in the operation unit (not shown) of the transmitter 220, for example. By adjusting individually, the degree of modulation of the modulated broadcast signal of each channel can be adjusted. In this case, the E / O converter 222 converts the broadcast band signal including the adjusted modulated broadcast signal into an optical signal.

The optical transmission line 230 is an optical fiber in this embodiment. A transmitter 220 is connected to one end of the optical transmission line 230, and an optical output terminal 231 is provided at the other end. The optical transmission line 230 transmits an optical signal output from the transmitter 220. As shown in FIG. 1, the optical output terminal 231 can be connected to a V-ONU 240, a signal measuring instrument 100 described later, and the like.

The V-ONU 240 is an O / E converter, which performs photoelectric conversion of an optical signal output from the optical output terminal 231 of the optical transmission line 230 and outputs the optical signal to a TV device 400 or the like. The electric signal output from the V-ONU 240 includes broadcast signals of CATV broadcasting and satellite broadcasting. In the TV device 400, channels of CATV broadcasting and satellite broadcasting are selected, and the selected broadcasting is viewed.

In the broadcast wave transmission system 200 of this embodiment, the number of transmitters 220 is singular. However, the present invention is not limited to this example, and the number of transmitters 220 may be plural. In this case, a WDM (Wavelength Division Multiplexing) filter is connected to the output end of the optical transmission line 230. The WDM filter separates a specific optical signal (that is, an optical signal including a broadcast band signal for the TV device 400) from a plurality of optical signals transmitted by the optical transmission line 230 and outputs the specific optical signal to the optical output terminal 231.

<Signal measuring instrument>
The signal measuring instrument 100 is a handy type checker. By connecting the signal measuring instrument 100 to the optical output terminal 231 of the optical transmission line 230, the optical signal transmitted by the broadcast wave transmission system 200 can be directly read, and the signal level (that is, the optical intensity) of the optical signal can be read directly. And, the signal level, the degree of modulation, the signal quality, and the like of the broadcast signal transmitted by the optical signal can be measured. The signal measuring instrument 100 can also be connected to a wired transmission system using a conventional coaxial cable, and can measure the signal level, modulation degree, signal quality, etc. of the broadcast signal transmitted by the wired transmission system. ..

FIG. 2 is a front view of the signal measuring instrument 100. FIG. 3 is a block diagram showing a configuration example of the signal measuring instrument 100.

As shown in FIG. 2, the signal measuring instrument 100 includes a housing 101, an optical connection unit 102, a coaxial cable connection unit 103, a display unit 104, an operation unit 105, and a battery BT.

The optical connection portion 102 and the coaxial cable connection portion 103 are connection terminals provided at the upper end of the housing 101. The optical output terminal 231 of the optical transmission line 230 can be directly connected to the optical connection unit 102. At this time, an optical signal is input to the signal measuring instrument 100 via the optical connection unit 102. For example, a coaxial cable of a wired transmission system or an output terminal thereof can be connected to the coaxial cable connection unit 103. At this time, the broadcast band signal transmitted by the wired transmission system is input to the signal measuring instrument 100 via the coaxial cable connection unit 103.

The display unit 104 and the operation unit 105 are provided in the housing 101. The display unit 104 is, for example, a liquid crystal display. The display unit 104 may, for example, indicate, for example, the optical intensity of the above-mentioned optical signal and its modulation degree M, the modulation degrees Ma and _Mb of each of the _CATV band signal and the satellite broadcast band signal included in the optical signal, the CATV band signal and the satellite. Modulation of each channel included in the broadcast band signal Modulation degree of broadcast signal _ma1 to max, _mb1 to _mby , signal level of the broadcast signal obtained _by demodating each modulated broadcast signal, and its signal quality (for example, CNR, BER, MER), etc. can be displayed. The details of these will be described later. The operation unit 105 receives the user's operation input. In the present embodiment, the operation unit 105 is a mechanical type having a plurality of operation buttons, but the present invention is not limited to this example, and the operation unit 105 may be a touch panel integrated with the display unit 104.

The battery BT is a power supply unit built in the signal measuring instrument 100, and supplies power to each component of the signal measuring instrument 100. The battery BT is a rechargeable and dischargeable secondary battery, and is a lithium ion battery in this embodiment. However, the present invention is not limited to this, and a primary battery such as a dry battery may be adopted as the battery BT.

The signal measuring instrument 100 is portable and is driven by a battery BT. Therefore, the signal measuring instrument 100 can be used without being subject to much restrictions on the location.

Further, as shown in FIG. 3, the signal measuring instrument 100 includes a photoelectric conversion unit 11, an amplifier 12, a switch SW, a distributor 2, filters 31 and 32, a tuner IC 4, a demodulation IC 5, and a memory 6. And the microcomputer 7, and the electric resistances R1 and R2. These are housed inside the housing 101. In the present embodiment, the tuner IC 4, the demodulation IC 5, and the microcomputer 7 of the signal measuring instrument 100 are separate components. However, the present invention is not limited to this example, and at least two of these may be the same component.

The photoelectric conversion unit 11 converts an optical signal transmitted via the optical transmission line 230 into an electric signal. The electrical signal includes a broadcast band signal. By incorporating the photoelectric conversion unit 11 in the signal measuring instrument 100, the optical signal can be directly read without going through a separate V-ONU, the degree of modulation of the broadcast band signal, and the broadcasting transmitted by the optical signal. The signal level, modulation degree, signal quality, etc. of a signal can be easily measured. Therefore, the workability of the signal measuring instrument 100 can be improved. Further, unlike the conventional level checker, it is not necessary to connect to the output terminal of the V-ONU 240 for measurement, so that it is possible to prevent the occurrence of a problem in the measurement result due to a defect of the V-ONU 240 or the like. Therefore, the measurement accuracy of the signal measuring instrument 100 can be improved.

In the present embodiment, the photoelectric conversion unit 11 includes a photodiode and photoelectrically converts the light incident from the optical connection unit 102 (that is, the optical signal transmitted through the optical transmission path 230) into an electric signal. The cathode of the photodiode is connected to the power supply voltage _VCC . The anode of the photodiode is grounded via the electrical resistance R1.

Further, the anode of the photodiode is connected to the microcomputer 7 via, for example, an electric resistance R2 of 100 kΩ. That is, the voltage signal of the photoelectric conversion current output from the photodiode is output to the microcomputer 7 via the electric resistance R2. The voltage signal output to the microcomputer 7 will be described later.

Further, the anode of the photodiode is connected to the amplifier 12. The amplifier 12 amplifies the electric signal output from the photoelectric conversion unit 11. The amplified electric signal is output to the switch SW via the capacitor C1. The DC component of the amplified electric signal is removed by the capacitor C1, and the AC component of the amplified electric signal is input to the switch SW.

The switch SW connects one of the two input ends to the distributor 2. One input end of the switch SW is connected to the amplifier 12 and the photoelectric conversion unit 11 via the capacitor C1. An AC component of an electric signal including a broadcast band signal transmitted by an optical signal from the broadcast wave transmission system 200 is input to one of the input ends. Further, the other input end of the switch SW is connected to the coaxial cable connection portion 103 via the capacitor C2. A broadcast band signal transmitted from a wired transmission system is input to the other input end. Switching of the input end in the switch SW can be performed, for example, based on the operation input received by the operation unit 105.

The distributor 2 distributes the signal output from the switch SW into the first signal and the second signal. The first signal is amplified by an amplifier (not shown) and then output to the filter 31. The second signal is amplified by an amplifier (not shown) and then output to the filter 32.

The filters 31 and 32 are bandpass filters, and are individually connected between the distributor 2 and the tuner IC 4. The filter 31 extracts a CATV band signal having a CATV band frequency from the first signal and outputs it to the tuner IC 4. The filter 32 extracts a satellite broadcasting band signal having a frequency of the satellite broadcasting band from the second signal and outputs it to the tuner IC 4.

The tuner IC 4 has an extraction unit 41 and a calculation unit 42. In other words, the signal measuring instrument 100 further includes an extraction unit 41 and a calculation unit 42. In this embodiment, the extraction unit 41 and the calculation unit 42 are functional components of the tuner IC 4. However, the present invention is not limited to this example, and at least one of these may be a physical component such as an electric circuit or a device.

The extraction unit 41 extracts the modulated broadcast signal from the broadcast band signal including a plurality of modulated broadcast signals in which the broadcast signal of each channel is intensity-modulated. For example, the extraction unit 41 converts the CATV band signal and the satellite broadcast band signal from analog to digital, extracts the modulated broadcast signals of all channels contained therein from the converted digital signals, and outputs them to the demodulation IC 5. ..

The calculation unit 42 calculates the signal level of the modulated broadcast signal extracted by the extraction unit 41, respectively. Further, the calculation unit 42 calculates the modulation degree of each modulated broadcast signal based on the signal level of the modulated broadcast signal. As described above, the modulated broadcast signal is a signal in which the broadcast signal of each channel is intensity-modulated. For example, the calculation unit 42 sets the modulation degree _ma1 to _max [%] (x is a positive integer of 1 or more) of the modulated broadcast signal of each channel included in the CATV band signal as the signal level of the modulated broadcast signal. Calculated based on. Similarly, the calculation unit 42 sets the modulation degree m _b1 to m _by [%] (y is a positive integer of 1 or more) of the modulated broadcast signal of each channel included in the satellite broadcast band signal of the modulated broadcast signal. Calculated based on the signal level. These modulation degrees _ma1 to _max and _mb1 to _mby are associated with the channel of the modulated broadcast signal and output to the microcomputer 7.

The demodulation IC 5 is a demodulation unit that demodulates a modulated broadcast signal into a broadcast signal. The demodulation IC 5 demodulates the modulated broadcast signal extracted by the extraction unit 41 and outputs it to the microcomputer 7.

The memory 6 is a non-transient storage medium that maintains storage even when the power supply is stopped. The memory 6 stores, for example, a program and information used in each component of the signal measuring instrument 100.

The microcomputer 7 is a control unit that controls the signal measuring instrument 100 based on the program and information stored in the memory 6. The microcomputer 7 has a modulation degree calculation unit 71 and a signal quality calculation unit 72. In other words, the signal measuring instrument 100 further includes a modulation degree calculation unit 71 and a signal quality calculation unit 72.

The modulation degree calculation unit 71 calculates the modulation degrees _{Ma, M b ,} and M. The degree of modulation _Ma [%] is the degree of intensity modulation of the CATV band signal. The degree of modulation M _b [%] is the degree of intensity modulation of the satellite broadcast band signal. The degree of modulation M [%] is the degree of intensity modulation of the broadcast band signal included in the electric signal output from the photoelectric conversion unit 11. At least one of the degree of modulation _{Ma, M b ,} and M may be calculated by the calculation unit 42 of the tuner IC 4.

（式１） For example, the modulation degree calculation unit 71 calculates the modulation degree _Ma of the CATV band signal based on the modulation degree _ma1 to _max of the modulated broadcast signals of all channels included in the CATV band signal. For example, the modulation degree Ma is the sum of the modulation degrees _ma1 to max of the modulation degree _ma1 to _max of the modulation broadcast signals of all channels extracted from the CATV band signal by the extraction unit 41 as shown in Equation 1 below. It can be obtained by calculating the square root. Note that _Na is the total number of channels included in the CATV band signal.

(Equation 1)

In this way, the signal measuring instrument 100 can individually and simultaneously grasp the modulation degree _ma1 to _max of the modulation broadcast signal of the channel of the CATV band, the number x of the channel, and the modulation degree _Ma of the CATV band signal. .. Therefore, in the transmission station of the channel processor 210 and the transmitter 220 of the broadcast wave transmission system 200, or the transmission station of the wired transmission system connected to the coaxial cable connection unit 103, the modulation degree and the number of channels of the modulated broadcast signal of the channel in the CATV band. It becomes easier to set x and the like more appropriately. For example, when the transmitting side changes the modulation degree of the modulated broadcast signal of _a predetermined channel or increases or decreases the number of CATV band channels transmitted to the receiving side, the receiving side modifies the CATV band signal Ma. Can be clearly and accurately grasped how the change is made. Therefore, it becomes easy to operate and design the transmission of the broadcast signal in the CATV band in the broadcast wave transmission system 200 or the like.

（式２） Further, the modulation degree calculation unit 71 calculates the modulation degree _Mb of the satellite broadcast band signal based on the modulation degree _mb1 to _mby of the broadcast signals of all channels included in the satellite broadcast band signal. For example, the modulation degree M _b is the sum of the modulation degrees m b1 to m _by of the modulation degrees m _b1 to m by of the broadcast signals of all channels extracted from the satellite broadcast band signal by the extraction unit 41, as shown in Equation 2 below. It can be obtained by calculating the square root. N _b is the total number of channels included in the satellite broadcast band signal.

(Equation 2)

Then, by the signal measuring instrument 100, the modulation degree _mb1 to _mby of the channel of the satellite broadcasting band, the number y of the channel, and the modulation degree _Mb of the satellite broadcasting band signal are individually and simultaneously. I can grasp it. Therefore, in the transmission station of the channel processor 210 and the transmitter 220 of the broadcast wave transmission system 200, or the transmission station of the wired transmission system connected to the coaxial cable connection unit 103, the modulation degree of the channel of the satellite broadcasting band and the modulation degree of the channel It becomes easier to set the number y and the like more appropriately. For example, when the transmitting side changes the modulation degree of the modulated broadcasting signal of a predetermined channel, or the number of channels of the satellite broadcasting band transmitted to the receiving side is increased or decreased, the modulation degree of the satellite broadcasting band signal is changed on the receiving side. It is possible to clearly and accurately grasp how M _b changes. Therefore, it becomes easy to operate and design the transmission of the broadcast signal in the satellite broadcast band in the broadcast wave transmission system 200 or the like.

（式３） Further, the modulation degree calculation unit 71 is based on the modulation degrees _ma1 to _max and _mb1 to _mby of all the broadcast signals included in the broadcast band signal, and the modulation degree M of the broadcast band signal included in the electric signal. Is calculated. For example, the modulation degree M is the sum of the modulation degrees _ma1 to max and _mb1 to _mby of the broadcast signals of all the channels extracted _by the extraction unit 41 squared as shown in Equation 3 below. It can be obtained by calculating the square root.

(Equation 3)

Then, by the signal measuring instrument 100, the modulation degree of the channel included in the broadcast band signal, the modulation degree of the broadcast signal, _ma1 to _max and _mb1 to _mby , the number of the channels (x + y), and the broadcast band signal. The modulation degree M can be grasped individually and simultaneously. Therefore, in the transmission station of the channel processor 210 and the transmitter 220 of the broadcast wave transmission system 200, or the transmission station of the wired transmission system connected to the coaxial cable connection unit 103, the modulation degree of the modulated broadcast signal of the channel included in the broadcast band signal, It becomes easier to set the number of channels (x + y) more appropriately. For example, when the transmitting side changes the modulation degree of the modulated broadcast signal of a predetermined channel, or the number of channels of the satellite broadcasting band transmitted to the receiving side is increased or decreased, the modulation degree M of the broadcasting band signal on the receiving side. Can be clearly and accurately grasped how the signal changes. Therefore, it becomes easy to operate and design the transmission of the broadcast signal in the broadcast band in the broadcast wave transmission system 200 or the like.

The modulation degrees M _a , M _b , and M may be calculated, for example, as values at a time point according to a user's operation input, or may be calculated in real time. These can be stored in the memory 6 and can be displayed on the display unit 104 at a time according to a user's operation input or in real time, for example.

The signal quality calculation unit 72 calculates the signal quality of the broadcast signal of each channel. The signal quality is, for example, CNR (Carrier-to-Noise Ratio), BER (Bit Error Rate), MER (Modulation Error Rate), and the like. Alternatively, it may be any one of these. The signal quality may be calculated, for example, as a value at a time point according to a user's operation input, or may be calculated in real time. These can be stored in the memory 6 and can be displayed on the display unit 104 at a time according to a user's operation input or in real time, for example.

Next, the microcomputer 7 further includes an A / D conversion unit 73 and a light intensity detection unit 74. The signal measuring instrument 100 further includes an A / D conversion unit 73 and a light intensity detection unit 74.

The A / D conversion unit 73 converts an analog voltage signal output from the photoelectric conversion unit 11 via the electric resistance R2 into a digital voltage signal. The A / D conversion unit 73 may be a component different from the microcomputer 7 without being limited to the present embodiment.

The light intensity detection unit 74 detects the light intensity of the optical signal based on the electric signal output from the photoelectric conversion unit 11. In the present embodiment, the light intensity detection unit 74 determines the light intensity (that is, the signal level of the optical signal) from the digital voltage signal output from the A / D conversion unit 73 based on the light intensity information stored in the memory 6. calculate. The light intensity information indicates the correspondence between the signal level of the digital voltage signal and the light intensity. In this way, the signal measuring instrument 100 can be provided with the function of an optical power meter. The light intensity may be calculated, for example, as a value at a time point according to a user's operation input, or may be calculated in real time. Further, the light intensity can be stored in the memory 6 and can be displayed on the display unit 104 at a time according to a user's operation input or in real time, for example.

In this embodiment, the modulation degree calculation unit 71, the signal quality calculation unit 72, the A / D conversion unit 73, and the light intensity detection unit 74 are all functional components of the microcomputer 7. However, the present invention is not limited to this example, and at least one of these may be a physical component such as an electric circuit or a device.

Further, in the above-described embodiment, the broadcast band signal transmitted by the broadcast wave transmission system 200 and the wired transmission system connected to the coaxial cable connection unit 103 includes a CATV band signal having a CATV band frequency and satellite broadcasting. Includes both satellite broadcast band signals with band frequencies. However, the present invention is not limited to this example, and the broadcast band signal may include one of a CATV band signal having a frequency in the CATV band and a satellite broadcast band signal having a frequency in the satellite broadcast band. That is, the broadcast band signal may include at least one of the CATV band signal and the satellite broadcast band signal. In this way, the signal measuring instrument 100 can individually and simultaneously grasp the modulation degree of the modulated broadcasting signal of at least one of the CATV band and the satellite broadcasting band and the number of the channels.

Further, the broadcast band signal may include a modulated broadcast signal of a channel in a frequency band other than the CATV band and the satellite broadcast band. Specifically, the broadcast band signal may include a modulated broadcast signal of a frequency band other than the CATV band and the satellite broadcast band, in addition to the modulated broadcast signal of the channels of the CATV band and the satellite broadcast band. It may include only the modulated broadcast signal of the channel of the frequency band other than the CATV band and the satellite broadcast band. For example, the broadcast band signal may include a modulated broadcast signal of a channel of a terrestrial digital broadcast wave. In this way, the signal measuring instrument 100 can individually and simultaneously grasp the modulation degree of the modulated broadcasting signal of the channel in the frequency band other than the CATV band and the satellite broadcasting band and the number of the channels.

The embodiment of the present invention has been described above. It should be noted that the above-described embodiment is an example, and it is understood by those skilled in the art that the combination of each component and each treatment can be variously modified and is within the scope of the present invention.

11 ... photoelectric conversion unit, 12 ... Amplifier, 2 ... Distributor, 31, 32 ... Filter, 4 ... Tuner IC, 41 ... Extraction unit, 42 ... Calculation unit, 5 ... Demodulation IC, 6 ... Memory, 7 ... Microcomputer, 71 ... Modulation degree calculation unit, 72 ... Signal quality calculation unit, 73 ... A / D conversion unit, 74 ... Light intensity detector,
100 ... Signal measuring instrument, 101 ... Housing, 102 ... Optical connection unit, 103 ... Coaxial cable connection unit, 104 ... Display unit, 105 ... Operation unit,
200 ... Broadcast wave transmission system, 210 ... Channel processor, 220 ... Transmitter, 221 ... Booster, 222 ... E / O converter, 230 ... Optical transmission line, 231 ...・ Optical output terminal, 240 ・ ・ ・ V-ONU, 300 ・ ・ ・ Satellite broadcast receiving antenna, 400 ・ ・ ・ TV device, _VCS・ ・ ・ Power supply voltage, C1, C2 ・ ・ ・ Capacitor, SW ・ ・ ・ Switch , R1, R2 ... Resistance element, BT ... Battery

Claims (7)

An extraction unit that extracts the modulated broadcast signal from a broadcast band signal including a plurality of intensity-modulated modulated broadcast signals of each channel, and an extraction unit.
A first calculation unit that calculates the first modulation degree of each of the modulated broadcast signals based on the signal level of the modulated broadcast signal, and
A signal measuring instrument including a second calculation unit that calculates a second modulation degree of the broadcast band signal based on the first modulation degree of all the modulated broadcast signals included in the broadcast band signal. Further equipped with a photoelectric conversion unit that converts an optical signal transmitted via an optical transmission line into an electric signal.
The signal measuring instrument according to claim 1, wherein the electric signal includes the broadcast band signal. The signal measuring instrument according to claim 2, further comprising a light intensity detecting unit that detects the light intensity of the optical signal based on the electric signal. The one according to any one of claims 1 to 3, wherein the broadcast band signal includes at least one of a CATV band signal having a CATV band frequency and a satellite broadcast band signal having a satellite broadcast band frequency. Signal measuring instrument. A demodulation unit that demodulates the modulated broadcast signal into the broadcast signal,
The signal measuring instrument according to any one of claims 1 to 4, further comprising a signal quality calculation unit for calculating the signal quality of the broadcast signal. The signal measuring instrument according to claim 5, wherein the signal quality includes at least one of CNR, BER, and MER. The signal measuring instrument according to any one of claims 1 to 6, wherein the signal measuring instrument is portable.

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