JP4530833B2 - Terrestrial digital broadcast signal level adjusting apparatus and television joint receiving method - Google Patents

Description

  In a local network having a plurality of terminals such as apartment houses such as apartments, houses in difficult-to-view areas, shopping streets, schools, companies, etc., a television broadcast signal is received as a spatial radio wave by a joint antenna. The present invention relates to a television joint reception system for supplying a broadcast signal to each terminal and a terrestrial digital broadcast signal level adjusting device used in the system. In particular, the apparatus and method for improving the reception quality of analog broadcasting by equalizing the level of the prefectural terrestrial digital broadcast signal with the level of the wide-area terrestrial digital broadcast signal and outputting the level to a transmission line having a booster About.

  Recently, terrestrial digital broadcasting has been put into practical use. In the future, after a transition period to terrestrial digital broadcasting, analog broadcasting is scheduled to stop service. However, in the transition period, it is necessary to be able to receive both analog broadcasting and terrestrial digital broadcasting. In a collective housing such as condominiums, a collection of houses in difficult-to-view areas, a shopping street, a school, a company, etc. It is difficult to switch to a broadcast receiving apparatus, and it is necessary to propagate an analog broadcast signal and a terrestrial digital broadcast signal to the transmission path of this joint reception system.

  On the other hand, there are two types of television broadcasting: wide-area broadcasting in which a plurality of prefectures are within the reception area and prefectural-area broadcasting in which a single prefecture is receivable. As for terrestrial digital broadcasting, transmission of terrestrial digital broadcasting has started as well as analog broadcasting for prefectural broadcasting. In this case, the prefectural broadcast is transmitted with a directivity at the time of transmission so that it cannot be received in other prefectures, and at a lower transmission signal level than the wide-area broadcast signal.

  For this reason, regarding the reception level of the terrestrial digital broadcast signal in the television joint reception system described above, the level of the prefectural area broadcast signal is lower than the level of the wide area broadcast signal. On the other hand, in the television joint reception system, after a terrestrial digital signal and an analog signal are mixed, a transmission signal is amplified by a booster provided at various points in the transmission path and transmitted to each terminal. At this time, the mixing ratio between the terrestrial digital broadcast signal and the analog broadcast signal is controlled by changing the level of each signal using an attenuator. When the ratio of the broadcast signal is increased, there is a problem that the reception quality of the analog broadcast is deteriorated due to the amplification by the booster, and the digital noise caused by the amplification distortion of the wide-area broadcast signal is superimposed on the analog broadcast signal. On the contrary, if the ratio of the terrestrial digital broadcast wave signal is reduced, the level of the prefectural broadcast signal is lowered and a block distortion failure occurs in the prefectural broadcast signal.

  In addition, it is possible to match the level of the prefectural broadcast signal with the level of the wide area broadcast signal using a filter, but to the extent that the prefectural broadcast signal band can match the level of the broadcast signal of one channel of the adjacent wide area broadcast, When a filter is used, the signal level in the band adjacent to the prefectural broadcast band cannot be attenuated completely, and eventually the difference between this signal level and the prefectural broadcast signal level is There is a problem that it remains without compensation.

  On the other hand, as described in the following patent document, when the reception level of the terrestrial digital broadcast signal is lower than the reception level of the analog broadcast signal, if the entire band is amplified at once by the booster, the reception level is caused by the distortion of the amplifier. Low terrestrial digital broadcast signals are affected. In order to solve this problem, a booster is proposed to match only the level of the terrestrial digital broadcast signal with the level of the analog broadcast signal by separating only the terrestrial digital broadcast signal with a band pass filter and amplifying it separately from the analog broadcast signal. Has been.

  However, the technology according to this document eliminates the problem of the reception level of only the terrestrial digital broadcast signal due to fading and multipath peculiar to the digital broadcast signal, and improves the reception quality of analog broadcasting. This is not a technique for adjusting the level in the television joint reception system so that the prefectural broadcast signal can be received. The terrestrial digital broadcast signal is extracted by a band pass filter and matched with the level of the analog broadcast signal. However, since the technique according to this document uses a band pass filter in the RF band, it is the same as the technique using the above filter. Furthermore, since the cutoff characteristic of the filter cannot be made steep, the level of the terrestrial digital broadcast signal cannot be matched with the level of the analog broadcast signal on a channel basis.

JP 2003-8929 A

  The present invention has been made to solve the above-described problems, and receives a terrestrial digital broadcast signal composed of a wide-area broadcast signal and a prefectural-area broadcast signal and an analog broadcast signal by a spatial radio wave from an antenna and a transmission line. An object of the present invention is to improve the reception quality of analog broadcasts in a television joint reception system that is supplied to each terminal via a TV.

  In order to solve the above-mentioned problem, the invention of claim 1 is to receive a terrestrial digital broadcast signal composed of a wide-area broadcast signal and a prefectural-area broadcast signal and an analog broadcast signal by an antenna using a spatial radio wave, and each terminal via a transmission line. In a terrestrial digital broadcast signal level adjusting device used in a television joint reception system to be supplied to a branch / distributor for branching / distributing a signal including at least a terrestrial digital broadcast signal from a transmission path, and a branched / distributed signal A first frequency conversion device that converts the frequency to a low predetermined frequency band, a SAW filter that extracts only the prefectural broadcast signal from the frequency band signal converted by the first frequency conversion device, and the prefectural broadcast signal extracted by the SAW filter Around the prefectural broadcast signal band that can be received by each terminal of the television joint reception system. A second frequency conversion device that performs number conversion, an amplifier that amplifies the prefectural broadcast signal band frequency-converted by the second frequency conversion device to a predetermined level, and a combiner / synthesizer that superimposes the output signal of the amplifier on the transmission line A terrestrial digital broadcast signal level adjusting device.

  Here, the television joint reception system refers to a system in which terminals, which are television receivers such as apartments, regions, and schools, are gathered in a network. Any system that receives spatial radio waves with an antenna and retransmits it to the network is not limited to that system. The number of channels for digital broadcasting and analog broadcasting is not particularly limited.

  Further, the antenna may be provided separately from the antenna that receives the terrestrial digital broadcast signal and the antenna that receives the analog broadcast signal, or may be provided with one antenna that receives in common. When a common receiving antenna is provided, after receiving by the antenna, the terrestrial digital broadcasting signal band and the analog broadcasting signal band are demultiplexed into a plurality of systems, and the system is configured to propagate the terrestrial digital broadcasting signal band. A terrestrial digital broadcast signal level adjusting device may be provided. When providing an antenna in common, a terrestrial digital broadcast signal level adjusting device may be provided in a transmission path through which the terrestrial digital broadcast signal and the analog broadcast signal propagate. In this case, the signal branched / distributed by the branch / distributor may be a signal including a terrestrial digital broadcast signal and an analog broadcast signal, or only the terrestrial digital broadcast signal is demultiplexed to be branched / distributed. You may make it do. Further, when the terrestrial digital broadcast signal level adjusting device is provided in a system through which only the terrestrial digital broadcast signal propagates, the terrestrial digital broadcast signal is branched / distributed. Therefore, branching / distributing at least a signal including a terrestrial digital broadcast signal from a transmission path may include branching / distributing including an analog broadcast signal, or only a terrestrial digital broadcast signal may be branched / distributed. Also means good. The same meaning applies to other claims.

  Moreover, the frequency band converted by the first frequency conversion device may be any frequency band lower than the band of the received prefectural broadcast signal. Generally, an intermediate frequency band of a television system is used. That is, the frequency conversion is performed so that the prefectural broadcast signal of terrestrial digital broadcasting is located in this intermediate frequency band. Thereafter, only the prefectural broadcast signal is accurately extracted by the SAW filter. Further, the frequency band subjected to frequency conversion by the second frequency conversion device may be the same band as the prefectural broadcast signal band at the time of reception, or may be a different band as long as it can be demodulated by the terminal. The frequencies of the carriers input to the first frequency conversion device and the second frequency conversion device are the same, and in the case of different bands, the frequencies of the carriers are different.

  According to a second aspect of the present invention, there is provided a television for receiving a terrestrial digital broadcast signal composed of a wide area broadcast signal and a prefectural area broadcast signal and an analog broadcast signal by a spatial radio wave with an antenna and supplying the terminal to each terminal via a transmission path. In a terrestrial digital broadcast signal level adjusting device used in a joint reception system, a branch / distributor for branching / distributing a signal including at least a terrestrial digital broadcast signal from a transmission line, and a lower predetermined frequency band for the branched / distributed signal A first frequency conversion device that converts the frequency into a frequency, a SAW filter that extracts only the prefectural broadcast signal from the frequency band signal converted by the first frequency conversion device, and amplifies the prefectural broadcast signal extracted by the SAW filter to a predetermined level Amplifier and the output signal of the amplifier at each terminal of the television joint reception system A second frequency converter for frequency-converting the prefectural broadcast signal band may signal a terrestrial digital broadcasting signal level adjusting device comprising a coupling / combiner and for superimposing the output signal of the second frequency converter to the transmission line.

  According to the present invention, in contrast to the invention of claim 1, only the prefectural broadcast signal is extracted and amplified by the SAW filter, and the amplified signal is converted into the frequency band on the transmission line by the second frequency converter, and transmitted. The only difference is that it is superimposed on the road.

According to a third aspect of the present invention, the terrestrial digital broadcast signal level adjusting device is inserted in a transmission path between the antenna and a booster closest to the antenna among the boosters inserted in the transmission path. A terrestrial digital broadcast signal level adjusting apparatus according to claim 1 or claim 2.
In other words, it is a device that adjusts the terrestrial digital broadcast signal level before it is input to the booster.

  According to a fourth aspect of the present invention, the terrestrial digital broadcast signal level adjusting device is inserted in a transmission path between an antenna and a mixer for mixing the terrestrial digital broadcast signal and the analog broadcast signal. The terrestrial digital broadcast signal level adjusting device according to claim 1 or 2. There are cases where there are two antennas for receiving a terrestrial digital broadcast signal and two antennas for receiving an analog broadcast signal, and cases where the signal is demultiplexed into a terrestrial digital broadcast signal and an analog broadcast signal after being received by a common antenna. In that case, a terrestrial digital broadcast signal level adjusting device is provided in a system through which the terrestrial digital broadcast signal propagates.

According to the fifth aspect of the present invention, there is a television joint reception in which a digital terrestrial broadcast signal composed of a wide-area broadcast signal and a prefectural broadcast signal and an analog broadcast signal are received by an antenna by spatial radio waves and supplied to each terminal via a transmission path. In the method, after branching / distributing a signal including at least a terrestrial digital broadcast signal from a transmission path, frequency-converting to a lower predetermined frequency band, and extracting only the prefectural broadcast signal from the frequency-converted signal by a SAW filter, The television joint reception method is characterized in that the frequency is converted into a prefectural broadcast signal band in the television joint reception system, amplified to a predetermined level, and then superimposed on a transmission line.
A method invention corresponding to the invention of claim 1.

According to the sixth aspect of the present invention, there is a television joint reception for receiving a terrestrial digital broadcast signal composed of a wide area broadcast signal and a prefectural area broadcast signal and an analog broadcast signal with a spatial radio wave by an antenna and supplying each terminal via a transmission line. In the method, after branching / distributing a signal including at least a terrestrial digital broadcast signal from a transmission path, the frequency is converted to a lower predetermined frequency band, and only the prefectural broadcast signal is extracted from the frequency converted signal by a SAW filter. The television joint reception method is characterized in that the extracted signal is amplified to a predetermined level, frequency-converted to a prefectural broadcast signal band in the television joint reception system, and then superimposed on a transmission line.
A method invention corresponding to the invention of claim 2.

  The invention of claim 7 is characterized in that the branching / distribution and the superposition are performed in a transmission line between the antenna and a booster closest to the antenna among the boosters inserted in the transmission line. Or it is the television joint reception method of Claim 6.

  The invention of claim 8 is characterized in that branching / distribution and superposition are performed in a transmission path between an antenna and a mixer for mixing a terrestrial digital broadcast signal and an analog broadcast signal. The television joint reception method according to claim 6.

A part of the signal including at least the terrestrial digital broadcast signal received from the antenna is branched or distributed. The branched / distributed signal is frequency-converted so that the prefectural broadcast signal is converted into a predetermined band, preferably an intermediate frequency band. Thereafter, only the prefectural broadcast signal is extracted by the SAW filter. As a result, it is possible to accurately extract only the prefectural broadcast signal of terrestrial digital broadcasting. The signal is also frequency converted to a high frequency band and amplified to a predetermined level. As a result, the prefectural area broadcast signal is adjusted to a level difference signal that is equal to the level of the other wide area broadcast signal or does not cause a failure in amplification by the booster. Therefore, as a result of adjusting the level of the low prefectural broadcast signal among the terrestrial digital broadcast signals to a high level, no noise is generated in the analog broadcast signal.
The invention of claim 2 produces the same effect as claim 1 because amplification of the prefectural broadcast signal is performed in a low predetermined frequency band obtained by frequency conversion.
Claims 5 and 6 are also a method invention, and similarly, a television joint reception method that does not affect the analog broadcasting with noise.
According to the third and seventh aspects of the present invention, since the level adjustment of the present invention is performed before the booster closest to the antenna in the television joint reception system, digital noise is given to the analog broadcast signal from the first booster. There is no.
According to the fourth and eighth aspects of the present invention, the level adjustment processing of the present invention is performed in the transmission path before the mixer for mixing the analog broadcast signal and the terrestrial digital broadcast signal. The effect of noise can be eliminated most effectively.

Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the following examples.
FIG. 1 is a configuration diagram showing a television joint reception system used in an apartment or the like. An antenna 11 for receiving a terrestrial digital broadcast signal and an antenna 12 for receiving an analog broadcast signal are provided. A signal received by each antenna propagates through a transmission path 13 and a transmission path 14, and the UHF band. Are mixed by the mixer 15. Then, the mixed signal of the terrestrial digital broadcast signal and the analog broadcast signal is amplified by the boosters 16a and 16b and distributed to each terminal 19 (television receiver) using the distributor 17, the branching device 18, and the like. In the mixer 15, the terrestrial digital broadcast signal and the analog broadcast signal are mixed. The adjustment of the signal levels of both signals is performed by adjusting the attenuation rates of the attenuator 21 and the attenuator 22.

The present invention is characterized in that a terrestrial digital broadcast signal level adjusting device 30 is provided in the transmission path 13 between the antenna 11 and the attenuator 21. This terrestrial digital broadcast signal level adjusting device 30 has the configuration shown in FIG.
In FIG. 2, a transmission line 13 is provided with a branching unit 31 that is an example of a branching / distributing unit and a directional coupler 32 that is an example of a coupling / combining unit. A prefectural broadcast wave signal processor 40 that amplifies the signal level of only the prefectural broadcast is provided in a branch path between the branch terminals of the branching device 31 and the directional coupler 32. The prefectural broadcast wave signal processor 40 includes a local oscillator 23, a first frequency converter 24, a second frequency converter 25, a SAW filter 26 and an amplifier 27 disposed between the converters. The first frequency converter 24 receives a signal having a predetermined frequency from the local oscillator 23, and makes the frequency transition of the terrestrial digital broadcast signal to a predetermined intermediate frequency band. From the terrestrial digital broadcast signal converted to the intermediate frequency band, only the prefectural broadcast signal band is extracted by the SAW filter 26. In the intermediate frequency band of the television system, only the prefectural broadcast band can be extracted sharply by the SAW filter 26. Next, the prefectural broadcast signal extracted by the SAW filter 26 is returned to the prefectural broadcast signal band on the transmission line 13 by the second frequency converter 25 that receives the oscillation signal from the local oscillator 23 and converts the frequency. Next, the prefectural broadcast signal is converted into a signal level after being superimposed on the transmission line 13 by the directional coupler 32, and is converted by the gain adjustment amplifier 27 so as to be equal to the signal level of the wide-area broadcast signal wave. Adjusted. The amplified prefectural broadcast signal is superimposed on the transmission line 13 by the coupler 32.

The result of signal processing by the terrestrial digital broadcast signal level adjusting device 30 is shown in FIG. As shown in FIG. 3A, the reception level of the terrestrial digital broadcast signal received by the antenna 11 is lower than the level of the wide area broadcast signal. As a result of only the prefectural broadcast signal being amplified by the amplifier 27 and superimposed on the transmission line 13 by the coupler 32, the level of the wide area broadcast signal and the level of the prefectural broadcast signal are obtained as shown in FIG. Can be equal.
As a result, it is possible to optimally adjust the mixing of the terrestrial digital broadcast signal and the analog broadcast signal, and digital noise is not superimposed on the analog broadcast signal.

  In this way, in the present invention, digital noise is not added to the analog broadcast signal, and the reception quality of the analog broadcast can be improved.

In the above embodiment, the frequency band when the prefectural broadcast signal is extracted by the SAW filter 26 is an intermediate frequency band in the television system. However, the low frequency band in which only the prefectural broadcast signal can be extracted sharply by the SAW filter 26. If so, the bandwidth is arbitrary.
Moreover, the prefectural broadcast signal exists in a route passing through the branching device 31 and the coupler 32 and a branching route passing through the SAW filter 26, and the latter is delayed with respect to the former. However, since this delay time is within the guard interval, a demodulation error does not occur even if both are superimposed by the coupler 32.
The antennas 11 and 12 may be provided in common as long as the terrestrial digital broadcast signal and the analog broadcast signal can be received simultaneously. In that case, the terrestrial digital broadcast signal and the analog broadcast signal may be demultiplexed by a demultiplexer and configured in the same manner as in FIG. Further, the terrestrial digital broadcast signal and the analog broadcast signal may be propagated to the transmission line 13 in FIG. 2 without demultiplexing. In that case, only the prefectural broadcast signal is extracted by the SAW filter 26.
In the above embodiment, the variable gain amplifier 27 may be provided between the SAW filter 26 and the second frequency converter 25.
Further, two local oscillators 23 are provided, and the frequency conversion by the second frequency converter 25 can be a band that is not the same band as the received prefectural broadcast signal and can be demodulated by the terminal of the joint reception system.

  In one wide area broadcast area, there is an area where a wide area broadcast signal transmitted from a transmission station in another wide area broadcast area is received. In this case, a wide area broadcast signal in the wide area broadcast area of the self having a high reception level and a wide area broadcast signal from another wide area broadcast area having a low reception level may be received. In such a case, if the present invention is used as a wide area broadcast signal having a low reception level as the prefectural area broadcast signal of the present invention and a wide area broadcast signal having a high reception level as the wide area broadcast signal of the present invention, the wide area broadcast having a low reception level is used. It can also be used when adjusting the signal so that it can be demodulated. Even in such a case, the present invention can be applied. The present invention can also be used as a countermeasure when a wide-area broadcast signal in such a different broadcast area is received. In this case, the quality of the analog broadcast signal can be prevented from being lowered.

  The present invention, in a television joint reception system for receiving a terrestrial digital broadcast signal composed of a wide area broadcast signal and a prefectural area broadcast signal, and an analog broadcast signal by an antenna by a spatial radio wave and supplying each terminal via a transmission path, It can be used to improve the reception quality of analog broadcasting.

The block diagram of the television joint reception system which showed specific embodiment of this invention. The individuality figure of the terrestrial digital broadcast signal level adjustment apparatus which showed concrete embodiment of this invention. Explanatory drawing which showed the method in which a level adjustment is carried out by the present Example apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 12 ... Antenna 13 ... Transmission path 15 ... Mixer 16a, 16b ... Booster 23 ... Local oscillator 24 ... 1st frequency converter 25 ... 2nd frequency converter 26 ... SAW filter 30 ... Terrestrial digital broadcasting signal level adjustment apparatus 31 ... Branch 32 ... Directional coupler 40 ... Broadcast wave signal processor

Claims (8)

Digital terrestrial broadcasting used in a television joint reception system that receives a terrestrial digital broadcast signal composed of a wide-area broadcast signal and a prefectural broadcast signal and an analog broadcast signal by an antenna using spatial radio waves and supplies it to each terminal via a transmission path In the signal level adjustment device,
A branch / distributor for branching / distributing a signal including at least the terrestrial digital broadcast signal from the transmission path;
A first frequency conversion device for frequency-converting the branched / distributed signal to a low predetermined frequency band;
A SAW filter that extracts only the prefectural broadcast signal from the frequency band signal converted by the first frequency converter;
A second frequency conversion device that converts the frequency of the prefectural broadcast signal extracted by the SAW filter into a prefectural broadcast signal band that can be received by each terminal of the television joint reception system;
An amplifier that amplifies the prefectural broadcast signal band frequency-converted by the second frequency converter to a predetermined level;
A terrestrial digital broadcast signal level adjusting device comprising: a combiner / synthesizer for superimposing the output signal of the amplifier on the transmission line. Digital terrestrial broadcasting used in a television joint reception system that receives a terrestrial digital broadcast signal composed of a wide-area broadcast signal and a prefectural broadcast signal and an analog broadcast signal by an antenna using spatial radio waves and supplies it to each terminal via a transmission path In the signal level adjustment device,
A branch / distributor for branching / distributing a signal including at least the terrestrial digital broadcast signal from the transmission path;
A first frequency conversion device for frequency-converting the branched / distributed signal to a low predetermined frequency band;
A SAW filter that extracts only the prefectural broadcast signal from the frequency band signal converted by the first frequency converter;
An amplifier that amplifies the prefectural broadcast signal extracted by the SAW filter to a predetermined level;
A second frequency conversion device that converts the frequency of the output signal of the amplifier to a prefectural broadcast signal band that can be received by each terminal of the television joint reception system;
A terrestrial digital broadcast signal level adjusting device comprising: a combiner / synthesizer that superimposes the output signal of the second frequency converter on the transmission line. The terrestrial digital broadcast signal level adjusting device is inserted in a transmission path between the antenna and a booster closest to the antenna among boosters inserted in the transmission path. The terrestrial digital broadcast signal level adjusting device as described in 2. 2. The terrestrial digital broadcast signal level adjusting device is inserted in a transmission path between the antenna and a mixer for mixing the terrestrial digital broadcast signal and the analog broadcast signal. Item 3. The terrestrial digital broadcast signal level adjustment device according to Item 2. In the television joint reception method of receiving a terrestrial digital broadcast signal composed of a wide area broadcast signal and a prefectural area broadcast signal, and an analog broadcast signal by an antenna by a spatial radio wave and supplying each terminal via a transmission path,
After branching / distributing a signal including at least the terrestrial digital broadcast signal from the transmission path, frequency-converting to a lower predetermined frequency band, and extracting only the prefectural broadcast signal from the frequency-converted signal by a SAW filter, A television joint reception method comprising: frequency-converting to a prefectural broadcast signal band in the television joint reception system, amplifying the signal to a predetermined level, and then superimposing the signal on the transmission line. In the television joint reception method of receiving a terrestrial digital broadcast signal composed of a wide area broadcast signal and a prefectural area broadcast signal and an analog broadcast signal with a spatial radio wave by an antenna and supplying each terminal via a transmission path,
After branching / distributing a signal including at least the terrestrial digital broadcast signal from the transmission path, frequency-converting to a lower predetermined frequency band, and extracting only the prefectural broadcast signal from the frequency-converted signal by a SAW filter, A television joint reception method, wherein the extracted signal is amplified to a predetermined level, frequency-converted to a prefectural broadcast signal band in the television joint reception system, and then superimposed on the transmission line. 7. The branching / distribution and the superposition are performed in a transmission path between the antenna and a booster closest to the antenna among boosters inserted in the transmission path. The television joint reception method described in 1. 6. The branching / distribution and the superposition are performed in a transmission path between the antenna and a mixer for mixing the terrestrial digital broadcast signal and the analog broadcast signal. 6. The television joint reception method according to 6.