JP2012124848A - Broadcast wave transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broadcast wave transmission system which can detect transmission of a broadcast wave in shorter time compared to a conventional case.SOLUTION: A broadcast wave transmission system 1 detecting an idle channel where broadcasting is not performed and transmitting the broadcast wave in the idle channel includes: a level detecting portion detecting levels of a plurality of prescribed partial segments among the plurality of segments included in a channel of a detection object; a channel determining portion determining whether the channel of the detection object is the idle channel or not based on the levels of the plurality of partial segments detected by the level detecting portion, and on a mutual difference between the levels; and a broadcast wave transmission device 20 transmitting the broadcast wave in the channel of the detection object, which is determined to be the idle channel in the channel determining portion.

Description

  The present invention relates to a broadcast wave transmission system that detects a vacant channel that is not being broadcast and transmits a broadcast wave in the vacant channel.

  In 2011, it is scheduled to end analog television broadcasting (hereinafter referred to as analog broadcasting) and shift to terrestrial digital television broadcasting (hereinafter referred to as digital broadcasting). When performing this digital broadcasting, it is necessary to detect a channel on which broadcasting is currently performed and to specify an empty channel other than the channel in order to determine a channel on which broadcasting is performed. As a method for specifying an empty channel in this way, conventionally, the electric field strength of each channel is measured, and when the electric field strength is equal to or higher than a predetermined strength, it is determined that broadcasting is being performed on the channel. There is a way.

  However, under the current situation where the transition to digital broadcasting is not completely completed, analog broadcasting and digital broadcasting are mixed, and even if the method using electric field strength is applied as described above, There is a possibility that the signal is mistakenly detected as a digital broadcast signal, and the digital broadcast cannot be performed even if the channel is actually vacant.

  In order to solve such problems, it has also been proposed to detect the symbol of each channel in addition to the electric field strength, and to determine the presence and type of the channel currently being broadcast based on this symbol. (For example, refer to Patent Document 1). In this method, the electric field strength of each channel is sequentially measured, and for a channel whose electric field strength is equal to or higher than a predetermined strength, a broadcast wave is demodulated to detect a symbol. When broadcasting is performed and no symbol is detected, it is determined that analog broadcasting is performed on the channel.

JP 09-232984 A

  However, when the presence / absence or type of a channel is determined based on a symbol as in the conventional case, it is necessary to demodulate a broadcast wave after measuring the electric field strength, and thus it takes time to determine. There was a problem.

  The present invention has been made in view of the above, and an object of the present invention is to provide a broadcast wave transmission system that can detect transmission of broadcast waves in a shorter time than conventional.

  In order to solve the above-described problems and achieve the object, the broadcast wave transmission system according to claim 1 detects a vacant channel on which broadcasting is not performed and transmits a broadcast wave on the vacant channel. A system for detecting a level of each of a plurality of predetermined segments among a plurality of segments included in a channel to be detected, and the portion detected by the level detection unit Channel determination means for determining whether or not the detection target channel is an empty channel based on the level of each of the plurality of segments and the mutual difference between these levels; Transmission means for transmitting broadcast waves in the detection target channel determined to be present.

  Further, the broadcast wave transmission system according to claim 2 is the broadcast wave transmission system according to claim 1, further comprising quality determination means for determining the quality of the broadcast wave in the detection target channel, wherein the quality determination means includes: The quality of the broadcast wave transmitted by the transmission means of the broadcast wave transmission system is determined.

  Further, the broadcast wave transmission system according to claim 3 is the broadcast wave transmission system according to claim 2, wherein the transmission means is the quality of the broadcast wave transmitted by the transmission means of the broadcast wave transmission system. Is determined to be equal to or less than a predetermined standard by the quality determination means, the channel on which the broadcast wave is currently transmitted is changed to another channel determined to be an empty channel by the channel determination means. Switch.

  Further, the broadcast wave transmission system according to claim 4 is the broadcast wave transmission system according to claim 3, wherein the transmission means switches the channel in which the broadcast wave is currently transmitted to another channel. The broadcast information for notifying the switching is included in the broadcast wave and transmitted on the channel through which the broadcast wave is currently transmitted.

  According to the broadcast wave transmission system of claim 1, since the presence or absence of broadcast waves in the detection target channel is determined based on the level of each of a plurality of segments and the difference between these levels, The presence / absence of a broadcast wave can be determined based only on the level, and it is not necessary to perform demodulation or symbol detection. Therefore, it is possible to detect the presence / absence of a broadcast wave in a shorter time than before.

  Further, according to the broadcast wave transmission system of the second aspect, since the quality of the broadcast wave transmitted by the transmission means of the broadcast wave transmission system is determined, the current broadcast is performed by the broadcast wave transmission system. It is possible to easily grasp the quality of broadcasts.

  Further, the broadcast wave transmission system according to claim 3, when the quality of the broadcast wave transmitted by the broadcast wave transmission system is not more than a predetermined standard, the channel through which the broadcast wave is currently transmitted is Since switching to another channel, the quality of the broadcast wave can be automatically improved.

  Moreover, since the broadcast wave transmission system of Claim 4 transmits the alerting | reporting information which alert | reports channel switching, when switching a channel to another channel, channel switching is performed with respect to a viewer. It is possible to notify in advance.

It is a block diagram which shows functionally the structure of the broadcast wave transmission system which concerns on embodiment of this invention. It is a block diagram which shows the structure of the broadcast wave detection apparatus of FIG. 1 functionally conceptually. It is a block diagram which shows the structure of the principal part of the broadcast wave detection apparatus of FIG. 2 functionally conceptually. It is a block diagram which shows the structure of the broadcast wave transmission apparatus of FIG. 1 functionally conceptually. It is a flowchart of a broadcast wave detection process. It is a figure which shows notionally the segment contained in one channel. It is a flowchart of a broadcast quality monitoring process. It is a flowchart of a channel switching process.

  Hereinafter, an embodiment of a broadcast wave transmission system according to the present invention will be described in detail with reference to the accompanying drawings. [I] First, the basic concept of the present embodiment will be described, then [II] the specific contents of the present embodiment will be described, and [III] Finally, a modification to the present embodiment will be described. However, the present invention is not limited by the present embodiment.

[I] Basic concept of the present embodiment First, the basic concept of the present embodiment will be described. The broadcast wave transmission system according to the present embodiment is a broadcast wave transmission system that detects a vacant channel that is not being broadcast and transmits a broadcast wave in the vacant channel. Here, the broadcast wave includes a broadcast wave of an arbitrary method and content, and includes, for example, a television broadcast wave and a radio broadcast wave. Hereinafter, a case where a television broadcast wave is targeted will be described. Detecting an empty channel that is not being broadcast means detecting a channel that does not have a broadcast wave. However, when there is no broadcast wave, the broadcast wave exists with an electric field strength that exceeds a predetermined reference level. As a predetermined reference level, any level other than the zero level can be set.

  One of the features of this broadcast wave transmission system is that level detection means for detecting the level of each of a plurality of predetermined segments among the plurality of segments included in the detection target channel, and the level detection means Channel determination means for determining whether or not the detection target channel is an empty channel based on the level of each of the plurality of segments detected in part and a difference between these levels; and the channel Transmission means for transmitting a broadcast wave in the channel to be detected, which is determined to be an empty channel by the determination means, is provided. That is, roughly, the level of some segments included in the channel to be detected is detected, and based on the relative relationship, an empty channel is determined, and each channel is not demodulated. Since the broadcast wave can be transmitted on the empty channel after the determination of the empty channel, the broadcast wave can be transmitted more quickly than in the past.

[II] Specific contents of the present embodiment Next, specific contents of the present embodiment will be described. First, the configuration of the broadcast wave transmission system according to the present embodiment will be described, and then various processes performed using the broadcast wave transmission system will be described.

(Constitution)
FIG. 1 is a block diagram functionally conceptually showing the configuration of the broadcast wave transmission system according to the present embodiment. The broadcast wave transmission system 1 is generally configured to include a reception antenna 2, a broadcast wave detection device 10, a broadcast wave transmission device 20, and a transmission antenna 3.

  The receiving antenna 2 is a receiving unit that receives a broadcast wave and outputs the broadcast wave as a broadcast signal to the broadcast wave detection device 10. The broadcast wave detection device 10 is a vacant channel detection unit that detects a vacant channel using the broadcast signal output from the receiving antenna 2. The broadcast wave transmission device 20 is a broadcast unit that generates a broadcast signal, modulates the broadcast signal to the frequency of an empty channel detected by the broadcast wave detection device 10, and outputs the modulated signal to the transmission antenna 3. The transmission antenna 3 is a transmission unit that transmits a broadcast signal output from the broadcast wave transmitter 20 as a broadcast wave. Note that the receiving antenna 2 and the transmitting antenna 3 can be configured in the same manner as in the prior art, and the details thereof are omitted.

(Configuration-Broadcasting wave detection device)
Next, the configuration of the broadcast wave detection device 10 will be described. FIG. 2 is a block diagram functionally conceptually showing the configuration of the broadcast wave detection device 10 of FIG. The broadcast wave detection device 10 includes a frequency selection unit 11, a level detection unit 12, a demodulation unit 13, a channel determination unit 14, a quality determination unit 15, a display unit 16, and a control unit 17.

  The frequency selection unit 11 is a frequency selection unit that extracts a broadcast signal having a desired frequency from the broadcast signal output from the receiving antenna 2 and outputs the broadcast signal to the level detection unit 12. The level detection unit 12 is level detection means for detecting the level of a broadcast signal having a desired frequency extracted by the frequency selection unit 11. The demodulator 13 is a demodulator that demodulates a broadcast signal having a desired frequency extracted by the frequency selector 11 and subjected to level detection by the level detector 12. The channel determination unit 14 determines whether the detection target channel is an empty channel based on the level of the broadcast signal detected by the level detection unit 12 and the broadcast signal demodulated by the demodulation unit 13. Channel determining means. The quality determination unit 15 is a quality determination unit that determines the quality of the broadcast wave in the detection target channel. The display unit 16 is a display unit that displays information about the detected broadcast wave, and here, includes a liquid crystal display. The control unit 17 is a control unit that controls each unit of the broadcast wave detection device 10. For example, the control unit 17 includes a CPU (Central Processing Unit) and is installed via an arbitrary storage medium or network. Is interpreted and executed.

  FIG. 3 is a block diagram functionally conceptually showing the configuration of the main part of the broadcast wave detecting apparatus of FIG. FIG. 3 shows only a part of each part of the broadcast wave detection apparatus of FIG. 2, and in fact, a configuration for performing the above-described functions may be included. As shown in FIG. 3, the frequency selection unit 11 includes a mixer 11a, an oscillator 11b, and a 1-segment Saw filter 11c. The frequency selection unit 11 oscillates the oscillator 11b at a frequency controlled by the control unit 17, and the oscillator 11b By inputting the output to the mixer 11a, a broadcast signal of a desired segment is extracted. The broadcast signal thus extracted is output to the level detector 12 after the noise component is removed by the 1-segment Saw filter 11c.

  The level detection unit 12 includes an AGC 12a and an AGC detection unit 12b. The AGC 12a adjusts the gain of a desired segment broadcast signal output from the frequency selection unit 11, and the AGC detection unit 12b Detect the level of the broadcast signal.

  The channel determination unit 14 includes a holding memory 14a and a pattern comparator 14b. The level detected by the AGC detection unit 12b is temporarily stored in the holding memory 14a, and a plurality of the stored levels are stored. The presence or absence of an analog broadcast wave is determined by comparing the segments with each other or with a predetermined value by the pattern comparator 14b.

(Configuration-broadcast wave transmitter)
Next, the configuration of the broadcast wave transmission device 20 of FIG. 1 will be described. FIG. 4 is a block diagram functionally conceptually showing the configuration of the broadcast wave transmitting apparatus 20 of FIG. The broadcast wave transmitting apparatus 20 includes an input unit 21, a broadcast signal generation unit 22, an amplification unit 23, a modulation unit 24, and a control unit 25. The input unit 21 is an input unit that receives broadcast data input and a broadcast start or end instruction. As the broadcast data, a video signal from a video device (not shown) or a voice signal from a voice device (not shown) is used. Accept input. The broadcast signal generation unit 22 is broadcast signal generation means for generating a broadcast signal by synthesizing the broadcast data received by the input unit 21. The amplification unit 23 is an amplification unit that amplifies the broadcast signal generated by the broadcast signal generation unit 22 to a predetermined level. The modulation unit 24 is a modulation unit that modulates the broadcast signal amplified by the amplification unit 23 according to a predetermined modulation method (for example, 64QAM (Quadrature Amplitude Modulation)), and an empty channel detected by the broadcast wave detection device 10. Modulation is performed according to the frequency. The control unit 25 is a control unit that controls each unit of the broadcast wave transmission device 20, and includes, for example, a CPU, and interprets and executes a broadcast wave detection program installed via an arbitrary storage medium or network. .

(processing)
Next, broadcast processing performed in the broadcast wave transmission system 1 will be described. This broadcast processing mainly includes a broadcast wave detection process performed by the broadcast wave detection device 10 in order to detect an empty channel, a broadcast wave transmission process mainly performed by the broadcast wave transmission device 20 in order to transmit a broadcast wave, In order to determine the quality of the broadcast wave transmitted by the wave transmission system 1, the broadcast quality monitoring process mainly performed by the broadcast wave detection device 10 and the channel through which the broadcast wave is transmitted by the broadcast wave transmission system 1 are determined. Since the switching is roughly divided into channel switching processing mainly performed by the broadcast wave transmission device 20, each of these processing will be described below in order. Hereinafter, the step is abbreviated as “S”.

(Processing-Broadcast wave detection processing)
First, the broadcast wave detection process will be described. FIG. 5 is a flowchart of the broadcast wave detection process. This broadcast wave detection process is repeatedly executed after the power to each device of the broadcast wave transmission system 1 is turned on. Unless otherwise specified, each step of the broadcast wave detection process is executed by the control unit 17 of the broadcast wave detection device 10.

  First, a broadcast wave is received by the receiving antenna 2 and is output to the broadcast wave detection device 10 as a broadcast signal. In this broadcast wave detection device 10, the control unit 17 determines the frequency of the channel that is the detection target of the broadcast wave, and outputs a control signal to the frequency selection unit 11 based on this determination, so that the channel that is the detection target Are extracted by the frequency selector 11 (SA1).

  This broadcast signal extraction is performed by combining a channel scan and a segment scan. The channel scan means that the broadcast signal is extracted by switching the frequency in units of channels. Here, in the channel divided every 6 MHz between 470 MHz and 770 MHz, which is the frequency band of digital broadcasting, Frequency band (470 to 476 MHz) is extracted first, and when the determination by the channel determination unit 14 ends, the next frequency band (476 to 482 MHz) is extracted next, and thereafter the determination by the channel determination unit 14 ends in the same manner. Each time the next channel is sequentially extracted, each channel is scanned.

  Further, the segment scan means that the broadcast signal is extracted by switching the frequency for each segment in each channel. Here, the guard band is a guard band among 14 segments included in the channel scanned by the channel scan. A part of the segments with a predetermined segment number is scanned in a predetermined order, with 13 segments excluding. Here, the segment number is a segment number defined in ARIB STD-B31, which is a standard for the transmission system of digital terrestrial television broadcasting. As shown in FIG. This segment is number 0, and increases alternately one by one as the segment moves left and right. In this segment scan, a segment for one-segment broadcasting (specifically, segment No. 0) is extracted first, and then a segment corresponding to an analog broadcast carrier (specifically, an analog broadcast video carrier). No. 7 segment and No. 12 segment corresponding to an analog broadcast audio carrier) are extracted. The segment for one-segment broadcasting is first extracted when the level of this segment is equal to or higher than a predetermined level, and it can be determined that digital broadcasting is being performed. This is because the determination can be performed with higher sensitivity than in the case of 12 segments. In addition, the segment for analog broadcasting is extracted when the level of this segment is equal to or higher than the predetermined level, analog broadcasting is being performed, or analog jamming waves are mixed in digital broadcasting. This is because it can be determined.

  Next, the level detection unit 12 detects the level of the segment scanned by the segment scan among the 14 segments included in the channel scanned by the channel scan described above. Specifically, the level of the 0th segment (hereinafter referred to as the 0th level), the level of the 7th segment (hereinafter referred to as the 7th level), and the level of the 12th segment (hereinafter referred to as the 12th level) are sequentially detected. (SA2). The segment level thus detected is output to the channel determination unit 14.

  Then, the channel determination unit 14 determines the presence or type of a broadcast wave based on the level output from the level detection unit 12. Specifically, the channel determination unit 14 determines whether at least one of the 0th level, the 7th level, and the 12th level is equal to or higher than a predetermined level (SA3). . As this predetermined level, a minimum level that should be recognized as a broadcast wave or an interference wave is set. If one level is not equal to or greater than the predetermined range (SA3, No), both the digital broadcast wave and the analog broadcast wave are scanned in the channel scanned by the channel scan of the frequency selection unit 11 (hereinafter referred to as a detection target channel). If not, the process proceeds to SA10 described later (SA4). On the other hand, when at least one level is equal to or higher than the predetermined level (SA3, Yes), the process proceeds to SA5.

  In SA5, the channel determination unit 14 determines whether the difference between the 0th level, the 7th level, and the 12th level is within a predetermined range (SA5). If these differences are within a predetermined range (SA5, Yes), it is determined that there is a digital broadcast wave in the detection target channel (SA6). The reason for this determination is that when there is an analog broadcast wave, the 7th level corresponding to the video carrier and the 12th level corresponding to the audio carrier are larger than the 0th level where the one-segment signal is present. On the other hand, when there is a digital broadcast wave, it can be assumed that the 7th level and the 12th level are almost the same size as the 0th level with the one-segment signal. When such a determination is made, the process proceeds to SA10 described later, and details of the digital broadcast wave are specified.

  On the other hand, when these mutual differences are not within the predetermined range (SA5, No), the channel determination unit 14 determines whether the 0th level is equal to or higher than the predetermined level (SA7). As this predetermined level, a minimum level that should be recognized as having a one-segment broadcasting wave is set. If the 0th level is not equal to or higher than the predetermined level (SA7, No), it is determined that there is only an analog broadcast wave in the detection target channel (SA8).

  On the other hand, when the 0th level is equal to or higher than the predetermined level (SA7, Yes), it is determined that there is an analog interference wave in the detection target channel although digital broadcasting is being performed (SA9). In this case, the channel determination unit 14 proceeds to SA10 described later, and specifies details of the digital broadcast wave.

  In SA10, the demodulator 13 demodulates the 0th segment of the detection target channel, and outputs the demodulated broadcast signal to the channel determination unit 14 (SA10). Thereafter, the channel determination unit 14 specifies the channel number of the detection target channel based on the demodulation result by the demodulation unit 13 for the 0th segment (SA11). Specifically, from the broadcast signal of the 0th segment demodulated by the demodulation unit 13, an ID (for example, NIT (Network Information Table), SDT (Service Description Table), BIT ( (Broadcaster Information Table), EIT (Event Information Table), or CDT (Common Data Table)) is acquired, and a channel number is specified by a known method based on the acquired ID. Then, the channel determination unit 14 outputs the result specified in this way to the display unit 16. However, SA10 and SA11 may be omitted when it is not necessary to specify the channel number.

  The control unit 17 displays the determination result on the display unit 16 (SA12). For example, the frequency of the channel to be detected, the presence / absence and type of broadcast wave (whether digital broadcast wave or analog broadcast wave exists, and the presence / absence of analog broadcast wave as interference wave), and the level of each broadcast wave are written And display numerically.

  Next, the control unit 17 determines whether or not the detection of all the channels of the digital channel has been completed (SA13). If the detection has not been completed (SA13, No), the next channel is changed to the detection target channel. Accordingly, the frequency of the channel to be detected for the broadcast wave is determined, and in SA1, a control signal is output to the frequency selection unit 11 based on this frequency, so that the broadcast signal of the channel to be detected is converted to the frequency selection unit. 11 to extract. Thereafter, until all the channels are extracted as detection target channels, the detection target channels are changed, and every time the change is made, broadcast waves based on the 0th level, the 10th level, and the 5th level for the detection target channel. The presence / absence and type of the image and the determination result are displayed. When the detection of all the channels of the digital channel is completed (SA13, Yes), the control unit 17 outputs the determination result for each channel to the broadcast wave transmitting apparatus 20 (SA14), and the broadcast wave detection process is ended. To do.

(Processing-Broadcast wave transmission processing)
Next, the broadcast wave transmission process will be described. This broadcast wave transmission process is repeatedly executed after the power to each device of the broadcast wave transmission system 1 is turned on. Unless otherwise specified, each step of the broadcast wave transmission process is executed by the control unit 25 of the broadcast wave transmission apparatus 20.

  In this process, when the input unit 21 receives a broadcast start instruction, the broadcast signal generation unit 22 generates a broadcast signal by synthesizing the video signal and the audio signal input to the input unit 21, and the amplification unit 23 amplifies this broadcast signal generation. On the other hand, based on the output from the broadcast wave detection device 10, the control unit 25 outputs the frequency of the channel identified as an empty channel in the broadcast wave detection process to the modulation unit 24. Then, the modulation unit 24 modulates the broadcast signal amplified by the amplification unit 23 with the frequency of the empty channel output from the control unit 25 and outputs the modulated signal to the transmission antenna 3. As a result, the digital broadcast wave is transmitted at the frequency of the empty channel. Thereafter, the broadcast is continued until the input unit 21 receives a broadcast end instruction, and the broadcast wave transmission process ends when the input unit 21 receives the broadcast end instruction.

(Processing-Broadcast quality monitoring process)
Next, the broadcast quality monitoring process will be described. FIG. 7 is a flowchart of the broadcast quality monitoring process. This broadcast quality monitoring process is repeatedly executed while a broadcast wave is being transmitted by the broadcast wave transmission system 1 after powering on each device of the broadcast wave transmission system 1. Unless otherwise specified, each step of the broadcast quality monitoring process is executed by the control unit 17 of the broadcast wave detection device 10.

  First, a broadcast wave is received by the receiving antenna 2 and is output to the broadcast wave detection device 10 as a broadcast signal. In the broadcast wave detection device 10, the control unit 17 determines a frequency to be a broadcast wave detection target, and outputs a control signal to the frequency selection unit 11 based on this frequency, thereby converting the broadcast signal of the frequency into a frequency. The selection part 11 is made to extract (SB1). At this time, the control unit 17 acquires the channel through which the broadcast wave is currently transmitted in the broadcast wave transmission device 20 from the broadcast wave transmission device 20, and outputs a control signal to the frequency selection unit 11 based on the frequency of the channel. Then, the frequency selection unit 11 extracts the broadcast signal having the frequency.

  Next, the quality determination unit 15 calculates a predetermined index value regarding the quality of the broadcast signal extracted by the frequency selection unit 11 (SB2). Specifically, the quality determination unit 15 performs a C / N (Carrier / Noise) ratio, a bit error rate (BER), or a modulation error ratio (MER) on the broadcast signal. And at least one of the calculation results is output to the control unit 17. The control part 17 displays such a calculation result on the display part 16 with a character and a numerical value (SB3).

  Next, the quality determination unit 15 determines whether or not the quality of the broadcast signal is equal to or higher than a predetermined reference by comparing the index value calculated in SB2 with a predetermined value set in advance (SB4). The determination result is output to the control unit 17. When the determination result indicates that the quality of the broadcast signal does not satisfy the predetermined standard (SB4, No), the control unit 17 starts the channel switching process (SB5) and ends the broadcast quality monitoring process.

(Processing-Channel switching process)
Finally, the channel switching process will be described. FIG. 8 is a flowchart of the channel switching process. This channel switching process is started in SB 5 of the broadcast quality monitoring process of FIG. 7 after the power to each device of the broadcast wave transmission system 1 is turned on. Unless otherwise specified, each step of the channel switching process is executed by the control unit 17 of the broadcast wave detection device 10 or the control unit 25 of the broadcast wave transmission device 20.

  In this process, the control unit 17 of the broadcast wave detecting device 10 acquires the channel through which the broadcast wave is currently transmitted in the broadcast wave transmitting device 20 from the broadcast wave transmitting device 20 and detects a free channel different from the channel. (SC1). This detection is performed in the same manner as the broadcast wave detection process described above except that the channel on which the broadcast wave is currently being transmitted is excluded from the target of the channel scan by the broadcast wave transmission device 20, so that the detailed description thereof will be given. Is omitted.

  When a new empty channel is detected in this way, the control unit 17 transmits a channel switching control signal including information specifying the frequency of the channel to the broadcast wave transmitting apparatus 20 (SC2). Upon receiving this channel switching control signal, the control unit 25 of the broadcast wave transmitting apparatus 20 synthesizes data including notification information related to channel switching with the broadcasting data input to the input unit 21. A broadcast signal is generated (SC3). The contents of the notification information include, for example, the fact that the channel is switched and the expected time when the channel is switched (for example, a standby time set in advance as a time to wait until the channel is actually switched). , Several seconds to several minutes), and the number of the channel to be switched to (for example, the number obtained by referring to a preset frequency-channel correspondence table based on the frequency of the channel to be switched to) Can do. Further, the output form of the notification information can be text data or voice data. The broadcast signal generated in this way is output as a broadcast wave by the transmission antenna 3 after being amplified by the amplifier 23 and modulated by the modulator 24, so that the channel can be switched for the viewer. Informed in advance.

  Next, the control unit 25 controls the modulation unit 24 so as to switch the frequency of the channel currently being broadcast to the frequency of the new empty channel included in the channel switching control signal (SC4). As a result, the broadcast signal is modulated by the frequency of the vacant channel and is output as a broadcast wave by the transmission antenna 3. Since the broadcast signal after switching in this way does not require data including notification information related to channel switching, a broadcast signal generated without combining the data is broadcast. However, data including broadcast information indicating the channel after switching may be combined for a predetermined time after the switching. The contents of the notification information include, for example, the fact that the channel is switched, the time when the channel is switched, and the number of the channel that is the switching source (for example, the frequency of the channel that is the switching source) , A number obtained by referring to a preset frequency-channel correspondence table). Moreover, the output form of the notification information can be text data or voice data. This completes the channel switching process.

(effect)
As described above, according to the present embodiment, it is determined whether or not the detection target channel is an empty channel based on the level of each of a plurality of segments and the difference between these levels. An empty channel can be determined based only on the level, and it is not essential to perform demodulation or symbol detection. Therefore, it is possible to determine an empty channel in a shorter time than in the past.

  Further, since the quality of the broadcast wave transmitted by the broadcast wave transmission device 20 of the broadcast wave transmission system 1 is determined, the quality of the broadcast currently being broadcast by the broadcast wave transmission system 1 can be easily grasped. It becomes possible.

  In addition, when the quality of the broadcast wave transmitted by the broadcast wave transmission system 1 is below a predetermined standard, the channel on which the broadcast wave is currently transmitted is switched to another channel. Can be improved automatically.

  Further, when the channel is switched to another channel, the notification information for notifying the channel switching is transmitted, so that it is possible to notify the viewer in advance that the channel switching is performed.

[III] Modifications to the Embodiments Although the embodiments of the invention have been described above, the specific configuration and means of the invention are within the scope of the technical idea of the inventions described in the claims. It can be arbitrarily modified and improved within. Hereinafter, such a modification will be described.

(About problems to be solved and effects of the invention)
First, the problems to be solved by the invention and the effects of the invention are not limited to the above-described contents, and the present invention solves the problems not described above or has the effects not described above. There are also cases where only some of the described problems are solved or only some of the described effects are achieved.

(About the detection unit of the empty channel)
In the above embodiment, the empty channel is detected in units of channels, but may be detected in units of segments. In other words, it is also under consideration that one-segment broadcasting will be liberalized in the future. If liberalization is permitted, broadcasting will be performed in any one of the 13 segments included in one channel. Even if it is performed, since it becomes possible to broadcast in another empty segment, it is possible to detect an empty segment and perform broadcasting in the empty segment. In other words, the empty channel in the claims is not limited to a channel in which broadcasting is not performed in all segments in the channel, and means a channel including at least one segment in which broadcasting is not performed.

  An empty segment can be detected by, for example, combining channel scanning and segment scanning, sequentially detecting all the levels of each segment of each channel, and setting a segment below a certain level as an empty segment. Further, for each segment, a C / N ratio, a bit error rate, or a modulation error ratio may be calculated, and a segment to be broadcast may be selected based on the calculation result.

(About quality judgment)
In the above-described embodiment, the broadcast quality monitoring process performed by the broadcast wave detection device 10 is performed only for the channel through which the broadcast wave is currently transmitted in the broadcast wave transmission device 20, but is not available in the broadcast wave transmission process. You may make it carry out at the time of the detection of a channel. That is, when a vacant channel is detected in the broadcast wave transmission process, the quality of the vacant channel is determined in the same manner as described above, and only the vacant channel whose quality is determined to be equal to or higher than the predetermined standard is transmitted to the broadcast wave transmitter 20. You may output and broadcast. In this case, when a plurality of vacant channels are detected in the broadcast wave transmission processing, one vacant channel with the highest quality is selected from the plurality of vacant channels, and the broadcast wave transmitting device is selected in the selected vacant channel. 20 may be broadcast.

(About extracted segments)
In the above embodiment, as the segment to be extracted, segment No. 0 which is a segment for one-segment broadcasting and segments No. 7 and No. 12 which are segments corresponding to analog broadcast carriers are extracted. The segment to be extracted can be changed. For example, an environment in which sufficient sensitivity can be obtained even if a segment dedicated to digital broadcasting other than the one-segment broadcasting segment (that is, a segment other than the 0th segment and a segment other than the 7th or 12th segment) is used. Below, you may extract the segment only for the said other digital broadcasting, and may determine using the level of the extracted segment. In addition, since there is a possibility that one-segment broadcasting by segments other than No. 0 may be liberalized in the future, in such a case, other one-segment broadcasting segments other than No. 0 are used as segments for One-Seg broadcasting. And may be determined using the extracted segment level. In addition, as the segment corresponding to the analog broadcast carrier wave, it is considered that the determination accuracy is improved by using both the 7th and 12th segments, but it is necessary to use both the 7th and 12th segments. However, only one of the segments may be used and the other segments may be omitted.

DESCRIPTION OF SYMBOLS 1 Broadcasting wave transmission system 2 Receiving antenna 3 Transmitting antenna 10 Broadcasting wave detection apparatus 11 Frequency selection part 11a Mixer 11b Oscillator 11c 1 segment Saw filter 12 Level detection part 12a AGC
12b AGC detection unit 13 demodulation unit 14 channel determination unit 14a holding memory 14b pattern comparator 15 quality determination unit 16 display unit 17, 25 control unit 20 broadcast wave transmission device 21 input unit 22 broadcast signal generation unit 23 amplification unit 24 modulation unit

Claims (4)

A broadcast wave transmission system that detects a vacant channel that is not being broadcast and transmits a broadcast wave in the vacant channel,
Level detection means for detecting the level of each of a plurality of predetermined segments among the plurality of segments included in the channel to be detected;
Channel determination for determining whether or not the channel to be detected is an empty channel based on the level of each of the plurality of segments detected by the level detection means and the difference between these levels Means,
Transmission means for transmitting a broadcast wave in the detection target channel determined as an empty channel by the channel determination means;
A broadcast wave transmission system comprising: Comprising quality judging means for judging the quality of the broadcast wave in the channel to be detected;
The quality determination means determines the quality of the broadcast wave transmitted by the transmission means of the broadcast wave transmission system;
The broadcast wave transmission system according to claim 1. The transmission means transmits the broadcast wave currently transmitted when the quality determination means determines that the quality of the broadcast wave transmitted by the transmission means of the broadcast wave transmission system is a predetermined standard or less. The channel being switched is switched to another channel determined to be an empty channel by the channel determination means.
The broadcast wave transmission system according to claim 2. When the transmission means switches the channel on which the broadcast wave is currently transmitted to another channel, the transmission means includes the broadcast information informing the channel change in the broadcast wave and the channel on which the broadcast wave is currently transmitted. Send,
The broadcast wave transmission system according to claim 3.

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