JP4870399B2 - Digital broadcast receiver - Google Patents

Description

  The present invention relates to a digital broadcast receiving apparatus mounted on a moving body such as a vehicle.

  In recent terrestrial digital broadcasting, hierarchical transmission is performed in which a transmission band assigned to each broadcasting station is divided into a number of segments and a plurality of layers composed of one or more segments are transmitted simultaneously. In hierarchical transmission, the higher the number of segments that make up a hierarchy, the higher the resolution of the video that can be transmitted. However, it becomes difficult to receive data without error during movement in a vehicle or the like. Therefore, for example, in the ISDB-T system compliant with Japan, one channel of the digital broadcasting band is divided into 13 segments, and 12 segments among them are used to achieve high resolution for a fixed receiver. An image is provided, and a low-resolution image is provided by a transmission method that is highly resistant to transmission errors using the remaining one segment.

  This enables high-resolution digital broadcasts to be received by fixed receivers installed in homes, etc., and mobile receivers such as mobile phones and PDAs to receive stable digital broadcasts while moving, even though they are low-resolution. It becomes.

  However, in a mobile reception device that is mounted on a mobile body and has a larger screen than a mobile phone, PDA, or the like, such as a navigation device mounted on a vehicle, as many as 12 pieces are possible even during movement. There is a desire to display high-resolution video using segments.

  In order to make this possible, for example, Patent Document 1 is a digital broadcast receiving device mounted on a vehicle, and has a database in which the reception rate of a digital broadcast signal is measured in advance at each point on a map, While guiding the travel route to the destination by the navigation function, the high-definition video using 12 segments is obtained by obtaining from the database the digital broadcast signal reception rate on the travel route and presenting it to the user. A user is provided with a material for determining which of the images using one segment, which is low resolution but excellent in reception while moving, should be received.

JP 2003-274303 A

  By the way, there is known a receiving apparatus that is connected to each of a plurality of antennas installed at different locations and has a plurality of demodulation means capable of demodulating radio waves of different frequency channels, and is capable of spatial diversity reception and frequency diversity reception. ing. For example, when the reception quality of radio waves is better than a predetermined quality, such a receiving apparatus demodulates radio waves of the same frequency channel to a plurality of demodulation means, and a demodulated signal from the demodulation means in a better reception state Decode. Thereby, even if the reception quality of one demodulation means deteriorates due to fading or shadowing, the reception apparatus can decode a demodulated signal with higher quality if the reception quality from other demodulation means is good. Therefore, the receiving apparatus can suppress the fluctuation of the demodulated signal due to fading and shadowing, and can improve the reception quality.

  In addition, when the reception quality of radio waves is worse than the predetermined quality, the receiving device can cause any demodulation means to search for other frequency channels, and to find other frequency channels with better reception quality, Also in this case, when the reception quality of the radio wave transmitted through another frequency channel is good, the reception device can improve the reception quality.

  In addition, a relay station that relays digital broadcasting may use a frequency channel different from that of an adjacent relay station even when the same program is broadcast. For this reason, when moving between relay stations using different frequency channels, the digital broadcast receiving apparatus mounted on the moving body needs to switch the frequency channel to be received.

  In this case, if the digital broadcast receiving apparatus has a spatial diversity reception function and a frequency diversity reception function, the digital broadcast reception apparatus is the same when the digital broadcast radio wave from the relay station has a sufficient reception quality. In the frequency channel, spatial diversity reception may be performed to decode a demodulated signal from a demodulation means with better reception quality. On the other hand, if the reception quality of the digital broadcast radio wave from the relay station becomes worse than the predetermined quality when moving away from the currently receiving relay station, the digital broadcast reception device cancels the spatial diversity reception. It is conceivable to start searching for another frequency channel using any demodulation means.

  However, spatial diversity reception is canceled when the reception quality of the digital broadcast radio wave is worse than a predetermined quality even though the fluctuation of the demodulated signal is suppressed by the spatial diversity reception. For this reason, the effect of spatial diversity reception that suppresses the influence of fading and shadowing is lost, and the digital broadcast receiving apparatus may not be able to display the digital broadcast video properly during the frequency channel search.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a digital broadcast receiving apparatus capable of reducing the disturbance of a display video caused by a channel search.

  In order to solve the above problems, the digital broadcast receiving apparatus of the present invention has a plurality of demodulation means, and when performing a channel search, causes at least one demodulation means to perform the channel search so that the channel search is performed. In the meantime, the demodulated signal of the digital broadcasting radio wave from the remaining demodulating means is decoded by a decoder that decodes the video with the lowest resolution.

For example, the present invention is a digital broadcast receiving device mounted on a mobile body,
With a digital broadcast wave and demodulates and outputs a demodulated signal, and multiple demodulation means you outputs the reception quality of the radio waves,
Decoding the pre Kifuku tone signals, and a plurality of digital broadcast decoders that a digital broadcast image of different resolutions formed raw,
Decoder selection means for causing a demodulated signal from any one of the plurality of demodulation means to be decoded by any of the plurality of digital broadcasting decoders;
Among the reception qualities output from each of the plurality of demodulation means, when the one having the best reception quality is less than a predetermined reception quality, the demodulation means outputting the worst reception quality Channel search instruction means for searching for other frequency channels ;
With
The decoder selection means includes
While the demodulation means outputting the worst reception quality is searching for other frequency channels, the demodulated signal from the demodulation means outputting the best reception quality is decoded into the digital broadcast video with the lowest resolution. Provided is a digital broadcast receiver characterized in that a digital broadcast decoder decodes the digital broadcast receiver.

  According to the digital broadcast receiving apparatus of the present invention, it is possible to reduce the disturbance of the display video due to the channel search.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration of a digital broadcasting system 10 according to an embodiment of the present invention. The digital broadcast system 10 includes a relay station 13, a digital broadcast antenna 14, a digital broadcast receiver 20, a navigation device 30, a display device 16, and a sound reproduction device 17. The relay station 13 receives a digital broadcast signal including a high-resolution video for a fixed reception device and a low-resolution video for a mobile reception device, which are created in the broadcast station, via a wired cable or the like, and receives the received digital broadcast signal on the ground Modulation is performed by a modulation method defined in digital broadcasting, and broadcasting is performed using radio waves.

  The vehicle 15 includes a GPS antenna 12, a digital broadcast antenna 14, a display device 16, a sound reproduction device 17, a sensor 18, a digital broadcast reception device 20, and a navigation device 30.

  The digital broadcast receiver 20 receives a digital broadcast signal from the relay station 13 via the digital broadcast antenna 14, and selects a high-frequency signal for the fixed receiver from the digital broadcast signal according to the reception quality of the received digital broadcast signal. A resolution video or a low-resolution video for a mobile reception device is extracted, audio data to be reproduced together with these videos is extracted, and the extracted video and audio data are sent to the navigation device 30.

  The navigation device 30 has map data, and is based on the GPS signal from the geodetic satellite 11 such as a GPS satellite, the speed of the vehicle 15 from the sensor 18, the traveling direction of the vehicle 15, and the like. Is estimated on the map. Then, the navigation device 30 displays the estimated current position of the vehicle 15 on the display device 16 together with the map data near the current position.

  In addition, the navigation device 30 sends the estimated current position of the vehicle 15 to the digital broadcast receiving device 20. At this time, the navigation device 30 sends the latitude and longitude of the vehicle 15 to the digital broadcast receiving device 20 as the estimated current position of the vehicle 15. As another example, the navigation device 30 may send the coordinates on the map data to the digital broadcast receiving device 20 as the estimated current position of the vehicle 15.

  In addition, the navigation device 30 receives the high-resolution video for the fixed reception device or the low-resolution video for the mobile reception device extracted by the digital broadcast reception device 20 and displays it on the display device 16, and also displays the corresponding sound in the sound reproduction device. 17 to play.

  In this example, the digital broadcast receiving device 20, the navigation device 30, the display device 16, and the sound reproduction device 17 are shown as separate bodies, but they may all be integrated as one device. Any two or more of them may be realized as an integrated device.

  FIG. 2 shows an example of a detailed configuration of the digital broadcast receiving apparatus 20. The digital broadcast receiving apparatus 20 includes a high-resolution video decoder 21, a low-resolution video decoder 22, a switching unit 23, a plurality of demodulation units 24, a channel search instruction unit 25, a channel extraction unit 26, and a relay station information storage unit 27.

  The relay station information storage unit 27 stores in advance information on at least one frequency channel used by each relay station 13 for transmission of digital broadcasting in association with the position information of each relay station 13.

  When instructed by the channel search instruction unit 25, the channel extraction unit 26 acquires information indicating the position of the vehicle 15 from the navigation device 30, and refers to the relay station information storage unit 27 to determine the current position of the vehicle 15. The relay station 13 existing in a predetermined range (in this example, a radius of 50 km from the current position of the vehicle 15) is extracted. Then, the channel extraction unit 26 acquires the extracted frequency channel used by the relay station 13 from the relay station information storage unit 27, and sends the acquired frequency channel information to the channel search instruction unit 25.

  The demodulator 24a demodulates the digital broadcast signal received from the relay station 13 via the digital broadcast antenna 14a based on, for example, the OFDM system, and extracts 13 segments by performing FFT conversion on the demodulated signal. Supply to the switching unit 23. Further, the demodulator 24 a generates a signal indicating the reception quality of the digital broadcast signal received via the digital broadcast antenna 14 a and supplies the signal to the switching unit 23 and the channel search instruction unit 25.

  Similarly to the demodulator 24a, the demodulator 24b also demodulates the digital broadcast signal received from the relay station 13 via the digital broadcast antenna 14b based on, for example, the OFDM system, and performs FFT conversion on the demodulated signal. Are extracted and supplied to the switching unit 23. Further, the demodulator 24 b generates a signal indicating the reception quality of the digital broadcast signal received via the digital broadcast antenna 14 b and supplies the signal to the switching unit 23 and the channel search instruction unit 25.

  Here, in this example, the signal indicating the reception quality is the received electric field strength of the digital broadcast radio wave to be received. As another example, the demodulator 24a and the demodulator 24b receive, as a signal indicating reception quality, a CN ratio (Carrier to Noise ratio), which is a noise level with respect to a reception level of a carrier wave in a digital broadcast signal to be received, Based on the data constellation, a constellation error amount or the like that is a variance value calculated in advance from reception coordinates of a known pilot signal may be generated.

  The switching unit 23 outputs the demodulated output of the demodulating unit 24, which outputs information indicating high received electric field strength, of the demodulating unit 24a and the demodulating unit 24b according to the value of the received electric field strength. Alternatively, it is supplied to the low resolution video decoder 22. In this example, the switching unit 23 causes the high-resolution video decoder 21 to decode the demodulated output from the demodulating unit 24 when the received electric field strength is equal to or higher than a predetermined first threshold value (−80 dBm in this example). If it is less than the first threshold, the demodulated output from the demodulator 24 is decoded by the low resolution video decoder 22.

  Further, when instructed by the channel search instruction unit 25, the switching unit 23 causes the low-resolution video decoder 22 to decode the demodulated output from the instructed demodulation unit 24.

  The high resolution video decoder 21 decodes 12 segments including the digital broadcast video for fixed reception out of the 13 segments extracted by the demodulator 24a or the demodulator 24b, and outputs the high resolution video for the fixed receiver and The accompanying audio data is extracted, and the extracted high-resolution video and audio data are sent to the navigation device 30.

  The low-resolution video decoder 22 decodes one segment including the digital broadcast video for mobile reception out of the 13 segments extracted by the demodulator 24a or the demodulator 24b, and the low-resolution video for the mobile receiver and The accompanying audio data is extracted, and the extracted low-resolution video and audio data are sent to the navigation device 30.

  The channel search instructing unit 25 controls the frequency channel received by the demodulating unit 24a and the demodulating unit 24b according to the received electric field strength of the digital broadcast radio wave from the demodulating unit 24a and the demodulating unit 24b. For example, among the received electric field strengths output from the demodulating unit 24a and the demodulating unit 24b, when the higher received electric field strength is greater than or equal to a predetermined second threshold (−70 dBm in this example), the lower received signal strength is received. By matching the frequency channel of the demodulator 24 that outputs the electric field strength with the frequency channel of the demodulator 24 that outputs a high received electric field strength, the demodulator 24a and the demodulator 24b perform spatial diversity reception.

  Further, for example, when the received electric field strength of the received electric field strength from the demodulating unit 24a and the demodulating unit 24b is less than the second threshold, the channel search instruction unit 25 inquires of the channel extracting unit 26, Get other frequency channels to search. Then, the channel search instructing unit 25 causes the demodulating unit 24 outputting a high received electric field strength to continue receiving digital broadcasting on the current frequency channel and outputting a low received electric field strength. 24, the channel search is executed for the frequency channel acquired from the channel extraction unit 26. In this way, the channel search instruction unit 25 causes the demodulation unit 24a and the demodulation unit 24b to perform frequency diversity reception for demodulating different frequency channels when the received electric field strength is low.

  At this time, the channel search instructing unit 25 instructs the switching unit 23 to cause the low-resolution video decoder 22 to decode the demodulated output of the demodulating unit 24 that has not performed the channel search.

  The channel search instructing unit 25 receives the received electric field strength measured by the demodulating unit 24 performing the channel search for each frequency channel to be searched. Then, the channel search instruction unit 25 selects the frequency channel when the highest received electric field strength among the received electric field strengths measured by the channel search is equal to or higher than the second threshold. The demodulator 24a and the demodulator 24b are instructed to demodulate, and the switch 23 is instructed to output the demodulated output of the demodulator 24 that outputs a high received electric field strength among the demodulator 24a and the demodulator 24b. The high-resolution video decoder 21 or the low-resolution video decoder 22 is supplied according to the value of the received electric field strength.

  Here, the channel search is performed by adjusting the reception frequency to each frequency channel to be searched, measuring the reception electric field strength of the digital broadcast radio wave transmitted in the frequency channel, and transmitting by the digital broadcast radio wave. The network information table (NIT) including the channel configuration information and frequency information transmitted by the relay station 13 is demodulated. When switching the relay station 13 to receive, the digital broadcast receiving apparatus 20 measures the received electric field strengths of all frequency channels used by the relay station 13 that is the switching destination based on the corresponding NIT, and performs digital broadcast. The frequency channel through which the radio wave is transmitted is detected, and the detected frequency channel is notified to the user of the digital broadcast receiving apparatus 20 as a selected channel.

  Further, in this example, the switching unit 23 and the channel search instruction unit 25 average the output values of the received electric field strengths from the demodulation unit 24a and the demodulation unit 24b, respectively, and then compare them with the first or second threshold value. In this case, the time constant used when the switching unit 23 averages the received electric field strength is smaller than the time constant used by the channel search instruction unit 25. Therefore, even if the channel search instruction unit 25 determines that the received electric field strength is −70 dBm or more, the switching unit 23 may determine that the received electric field strength is less than −80 dBm.

  FIG. 3 shows an example of the structure of data stored in the relay station information storage unit 27. The relay station information storage unit 27 sets the position information 271 that is information indicating the position of the relay station 13 and the frequency channel 272 that the relay station 13 uses for digital broadcasting to the relay station ID 270 that identifies each relay station 13. They are stored in advance in association with each other.

  Since the frequency channel stored in the relay station information storage unit 27 is used for measuring the reception electric field strength of the digital broadcast radio wave transmitted through the frequency channel in the channel search, the radio wave for digital broadcasting is always transmitted. Preferably, the frequency channel is

  In this example, the information stored in the position information 271 is a value indicating the latitude and longitude of the corresponding relay station 13. As another example, the position information 271 may store coordinates on map data held by the navigation device 30.

  The information stored in the relay station information storage unit 27 is stored, for example, at the time of shipment of the digital broadcast receiving device 20, for example, but when the relay station 13 is newly installed after shipment, In order to cope with a case where the transmission channel is changed, it is preferable to be configured to be able to be updated by data communication by digital broadcasting, a portable recording medium, a mobile phone or the like.

  FIG. 4 is a conceptual diagram for explaining processing when switching the relay station 13 to be received. FIG. 4A shows the positional relationship between the relay station 13 and the area 40 where the digital broadcast radio wave transmitted by the relay station 13 reaches with the intensity capable of demodulating the digital broadcast. FIG. 4B shows the relationship between the distance from the relay station 13 and the electric field strength of the digital broadcast radio wave transmitted from each relay station 13. FIG. 4C is an enlarged view of the region 43 in FIG.

  For example, as shown in FIG. 4 (a), areas 40a and 40b in which digital broadcast can be received by relay station A and relay station B are distributed, and vehicle 15 equipped with digital broadcast receiver 20 is connected to relay station A. Consider the case of moving from the vicinity to the vicinity of relay station B.

  As shown in FIG. 4B, the electric field intensity received by the digital broadcast receiving device 20 mounted on the vehicle 15 decreases as shown in the distribution 41 as the vehicle 15 moves away from the relay station A. Further, when approaching relay station B to some extent, digital broadcast receiving apparatus 20 can receive digital broadcast based on the digital broadcast radio wave from relay station B. Then, the electric field intensity from the relay station B received by the digital broadcast receiver 20 increases as shown in the distribution 42 as the distance from the relay station B approaches.

  In this example, the digital broadcast receiving apparatus 20 constantly monitors the received electric field strength from the relay station 13 (relay station A in FIG. 4) that is currently receiving the digital broadcast, and based on the received electric field strength, The measurement of the received electric field strength from another relay station 13 (relay station B in the example of FIG. 4) is started. When the received electric field strength from the other relay station 13 is higher than the received electric field strength from the relay station 13 that is currently receiving the digital broadcast, the digital broadcast receiving device 20 changes the received relay station 13 to the other relay station 13. Switch to the relay station 13.

Hereinafter, the operation of switching the receiving relay station 13 will be described in more detail with reference to FIG. Reception electric field strength E ₂ indicates the reception electric field strength of which can demodulate a high resolution video signal minimum (first threshold value in this example) using 12 segments in the digital broadcasting waves. Reception field strength E ₃ is a low resolution video signal using the one segment in a digital broadcast wave indicating the received field strength that can be demodulated minimum. Figure 4 (c) section (1) in indicates the section from the position of the relay station A to a position where the reception field strength E _1, section (2) is received electric field from the reception electric field strength E ₁ a position shows a section of a position where an intensity of E _3.

  During the section (1), the digital broadcast receiver 20 causes both the demodulator 24a and the demodulator 24b shown in FIG. 2 to receive the frequency channel from which the relay station A transmits the digital broadcast radio wave. , Spatial diversity reception is performed. As a result, the switching unit 23 allows the demodulating unit with the higher received electric field strength even when the received electric field strength of either the demodulating unit 24a or the demodulating unit 24b instantaneously decreases due to fading, shadowing, or the like. The 24 demodulated outputs can be supplied to the high resolution video decoder 21 or the low resolution video decoder 22. Therefore, the switching unit 23 can suppress frequent switching between the high-resolution video decoder 21 and the low-resolution video decoder 22 due to fluctuations in the received electric field strength during movement. Therefore, the digital broadcast system 10 can display the received digital broadcast on the display device 16 in a more easily viewable form.

  In the section (2), the digital broadcast receiving apparatus 20 causes either the demodulator 24a or the demodulator 24b to continuously receive the frequency channel from the relay station A, and transmits the frequency channel from the other relay station 13 to the other. Search for frequency channels of digital broadcast radio waves. At this time, the switching unit 23 causes the low-resolution video decoder 22 to decode the demodulated signal from either the demodulating unit 24a or the demodulating unit 24b. As a result, even when the spatial diversity is canceled, switching between the high resolution video decoder 21 and the low resolution video decoder 22 does not occur frequently, and the digital broadcast system 10 can prevent the received digital broadcast from becoming difficult to see. In addition, the received digital broadcast can be displayed reliably.

Then, in the section (2), when the digital broadcast radio wave having the reception electric field strength E ₄ higher than the reception electric field strength E ₁ is received from the relay station B, the channel search instruction unit 25 sends the demodulation unit 24a and the demodulation unit 24b to the demodulation unit 24a and the demodulation unit 24b. The frequency channel of the digital broadcast radio wave transmitted from the relay station B is received.

On the other hand, in the section (2), when the received electric field strength from the relay station B is lower than the reception field strength E _1, channel search instruction unit 25 includes a received signal strength from the relay station A currently being received, The received electric field intensity from relay station B detected by the search is compared.

  If the received electric field strength from the relay station A that is currently received is higher than the received electric field strength from the relay station B detected by the search, the channel search instructing unit 25 performs digital broadcasting from the relay station A. The demodulator 24 receiving the radio wave continuously receives the digital broadcast radio wave from the relay station A, and the remaining demodulator 24 continues the channel search.

  If the received electric field strength from the relay station A currently received is lower than the received electric field strength from the relay station B detected by the search, the channel search instructing unit 25 performs the digital broadcast from the relay station A. The demodulator 24 receiving the radio wave receives the digital broadcast radio wave from the relay station B, and the remaining demodulator 24 continues the channel search. As described above, the digital broadcast receiving apparatus 20 switches the receiving relay station 13.

Incidentally, the digital broadcast receiving apparatus 20, even when the received signal strength from the relay station A falls below E _1, a predetermined range from the current position of the vehicle 15 obtained from the navigation device 30 (e.g., the current vehicle 15 If the relay station 13 exists within a radius of 5 km from the position, the frequency channel of another relay station 13 may not be searched. Thereby, an unnecessary channel search performed by the demodulator 24 when the vehicle 15 is hidden behind a shield can be prevented, and the digital broadcast receiver 20 can suppress an increase in processing load.

FIG. 5 is a flowchart showing an example of the operation of the digital broadcast receiving apparatus 20 when the relay station 13 is switched. For example, the digital broadcast receiving apparatus 20 is receiving a digital broadcast radio wave having a reception electric field strength of E ₁ or more from the relay station 13, and both the demodulation units 24 a and 24 b demodulate the digital broadcast radio wave from the relay station 13. If so, the digital broadcast receiver 20 starts the processing shown in this flowchart.

First, channel search instruction unit 25 refers to the information indicating the received signal strength from the demodulator 24a and the demodulator 24b, among these, the reception field strength of the higher is whether it is less than the E ₁ Determine (S100). E ₁ or more when (S100: No), the channel search instruction unit 25 repeats step 100 until less than _{E 1.}

If among the demodulator 24a and the demodulator 24b, the received field strength of more that outputs a higher received field strength is less than the _{E 1} (S100: Yes), channel search instruction unit 25, instructs the switching unit 23 Then, the demodulated output from the designated demodulator 24 is decoded by the low resolution video decoder 22 (S101). In step 101, the demodulated output from either the demodulator 24a or demodulator 24b may be decoded by the low-resolution video decoder 22, but in this example, for convenience of explanation, the switching unit 23 receives the demodulator from the demodulator 24a. Assume that the output is decoded by the low-resolution video decoder 22.

  Next, the channel search instruction unit 25 instructs the channel extraction unit 26 to extract a frequency channel to be searched (S102). Then, the channel search instruction unit 25 selects one of the frequency channels extracted by the channel extraction unit 26 and instructs the demodulation unit 24b to receive the selected frequency channel (S103).

  Next, the demodulator 24b measures the received electric field strength of the digital broadcast radio wave transmitted in the designated frequency channel (S104). The channel search instruction unit 25 holds the received electric field strength measured by the demodulator 24b in association with the measured frequency channel.

Next, the channel search instructing unit 25 determines whether or not the received electric field strength has been measured for all frequency channels to be searched (S105). When the received electric field strength has not been measured for all frequency channels to be searched (S105: No), the channel search instruction unit 25 performs the process shown in step 103 again. On the other hand, if the received signal strength for all the frequency channels of the search target is measured (S105: Yes), channel search instruction unit 25, the highest ones whether E ₁ or more in the measured reception field strength Is determined (S106).

If the highest among the measured received field strength is less than _{E 1} (S106: No), the channel search instruction unit 25 performs the processing shown in step 101 again. At this time, when the demodulator 24a has the highest received electric field strength higher than the received electric field strength of the digital broadcast radio wave being demodulated, the channel search instruction unit 25 sends the highest received electric field strength to the demodulator 24a. Indicates to demodulate the frequency channel.

If the highest received electric field strength measured is E ₁ or more (S106: Yes), the channel search instructing unit 25 assigns the frequency channel having the highest received electric field strength to the demodulating unit 24a and the demodulating unit 24b. Instruct to demodulate (S107). Then, the channel search instructing unit 25 instructs the switching unit 23 to cause the high-resolution video decoder 21 or the low-resolution video decoder 22 to decode the demodulated output according to the received electric field strength from the demodulating unit 24a and the demodulating unit 24b. (S108) The channel search instructing unit 25 performs the process shown in step 100 again.

  The embodiment of the present invention has been described above.

  As is clear from the above description, according to the digital broadcast receiving apparatus 20 of the present embodiment, it is possible to reduce the disturbance of the display video caused by the channel search.

  In addition, this invention is not limited to said embodiment, Many deformation | transformation are possible within the range of the summary.

  For example, in the present embodiment, the digital broadcast receiving device 20 has acquired the position information of the vehicle 15 from the navigation device 30, but as another example, based on the GPS signal from the geodetic satellite 11 instead of the navigation device 30. You may acquire the position of the vehicle 15 in which the digital broadcast receiver 20 is mounted from the GPS receiver which estimates the own position.

  Further, when the departure point and the destination point are input from the user, the navigation device 30 searches for a recommended route using road data including road coordinates, travel time, etc., and drives the vehicle 15 according to the searched recommended route. If the current position of the vehicle 15 cannot be specified, the recommended route of the vehicle 15 may be transmitted to the digital broadcast receiving device 20. In this case, the digital broadcast receiving device 20 preferentially performs a channel search for the frequency channel of the relay station 13 that is within a predetermined range from the recommended route received from the navigation device 30. As a result, even when the GPS signal cannot be received and the current position of the vehicle 15 cannot be specified while traveling in a tunnel or an urban area, the frequency channel can be searched by narrowing the number to some extent.

  In the digital broadcast receiver 20 of the present embodiment, the digital broadcast receiver 20 that displays video and audio on the display device 16 and the sound reproduction device 17 mounted on the vehicle 15 and the like has been described as an example. However, the present invention is not limited to this, and the present invention may be applied to a PDA, a mobile phone, a goggle, a helmet-mounted head mounted display, or the like that can browse digital broadcasting. In this case, a GPS signal may be used as information for specifying the position of the digital broadcast receiver 20.

1 shows a configuration of a digital broadcasting system 10 according to an embodiment of the present invention. An example of a detailed configuration of the digital broadcast receiving apparatus 20 is shown. An example of the structure of the data stored in the relay station information storage unit 27 is shown. It is a conceptual diagram for demonstrating the process in the case of switching the relay station 13 to receive. 4 is a flowchart showing an example of the operation of the digital broadcast receiving apparatus 20 when switching the relay station 13;

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Digital broadcasting system, 11 ... Geodetic satellite, 12 ... GPS antenna, 13 ... Relay station, 14 ... Digital broadcasting antenna, 15 ... Vehicle, 16 ... Display device , 17 ... Sound reproduction device, 18 ... Sensor, 20 ... Digital broadcast receiving device, 21 ... High resolution video decoder, 22 ... Low resolution video decoder, 23 ... Switching unit, 24 ... Demodulation unit, 25 ... Channel search instruction unit, 26 ... Channel extraction unit, 27 ... Relay station information storage unit, 270 ... Relay station ID, 271 ... Location information, 272 ..Frequency channel, 30 ... navigation device, 40 ... area, 41, 42 ... distribution, 43 ... area

Claims (4)

A digital broadcast receiver mounted on a mobile body,
With a digital broadcast wave and demodulates and outputs a demodulated signal, and a plurality of demodulating means to output a reception quality of the radio waves,
Decoding the pre Kifuku tone signals, and a plurality of digital broadcast decoders that a digital broadcast image of different resolutions formed raw,
Decoder selection means for causing a demodulated signal from any one of the plurality of demodulation means to be decoded by any of the plurality of digital broadcasting decoders;
Among the reception qualities output from each of the plurality of demodulation means, when the one having the best reception quality is less than a predetermined reception quality, the demodulation means outputting the worst reception quality , and a Ruchi Yanerusachi instructing means to search for another frequency channel,
The decoder selection means includes
While the demodulation means outputting the worst reception quality is searching for other frequency channels, the demodulated signal from the demodulation means outputting the best reception quality is decoded into the digital broadcast video with the lowest resolution. A digital broadcast receiver characterized in that a digital broadcast decoder decodes the digital broadcast receiver. A digital broadcast receiver mounted on a mobile body,
With a digital broadcast wave and demodulates and outputs a demodulated signal, and two demodulation means you outputs the reception quality of the radio waves,
Decoding the pre Kifuku tone signal, and a high-resolution video decoder for generating a high-resolution digital broadcast image,
Decoding the pre Kifuku tone signal, and the low-resolution video decoder that forms the raw high resolution digital broadcast low resolution digital broadcast image lower resolution than the image produced by the high-resolution video decoder,
The demodulated signal from either one of the two demodulation means, a decoder selection means for decoding the high-resolution video decoder or the low-resolution video decoder,
Among the reception quality output from each of the two demodulation means, the better the reception quality, when it becomes a receiving less quality predetermined demodulation means towards which outputs a bad receiving quality Channel search instruction means for searching for other frequency channels ;
With
The decoder selection means includes
While the demodulating means outputting the poor reception quality searches for another frequency channel, the demodulated signal from the demodulating means outputting the good reception quality is decoded by the low-resolution video decoder. A digital broadcast receiver characterized by the above. The digital broadcast receiver according to claim 1 or 2,
Relay station information storage means for storing information of at least one frequency channel used for transmission of digital broadcast by each relay station relaying digital broadcast in association with position information of each of the relay stations;
Information indicating the position of the mobile unit is acquired from the outside, and a frequency channel used by a relay station located within a predetermined range from the position of the mobile unit is extracted with reference to the relay station information storage unit Channel extraction means,
The demodulating means includes
A digital broadcast receiving apparatus characterized in that when a search for a frequency channel is instructed by the channel search instruction means, the frequency channel extracted by the channel extraction means is preferentially searched. The digital broadcast receiver according to any one of claims 1 to 3,
The digital broadcast receiving apparatus, wherein the demodulation means receives digital broadcast radio waves via different antennas.

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