JP4426541B2 - Digital broadcast receiver - Google Patents

Description

  The present invention relates to a digital broadcast receiver for receiving a digital broadcast such as a terrestrial digital television broadcast.

  In recent years, digital broadcasting such as terrestrial digital television broadcasting has started with the digitization of broadcasting media. A digital broadcast station does not transmit information of other stations as its transmission information (see, for example, Non-Patent Document 1). Therefore, in the digital broadcast receiver, it is necessary to scan (or search) all channels at the installation point, and to construct a channel list that covers the frequency channels of digital broadcast that can be received.

  In a conventional digital broadcast receiver, when a channel list of receivable frequency channels is constructed, it is determined whether a certain frequency channel is receivable, whether a transport stream (TS) signal is received. It is done by judging. Therefore, if the TS signal cannot be received within a certain time, it is determined that reception is impossible and the next channel scan is performed. Further, in the digital broadcast receiver described in Patent Document 1, when a channel list of receivable frequency channels is constructed, the presence / absence of a radio frequency signal of a predetermined frequency channel is determined before determining whether a TS signal is received. Deciding. The determination as to the presence or absence of a radio frequency signal of a predetermined frequency channel is performed by detecting an automatic gain control circuit voltage (AGC circuit voltage: hereinafter referred to as “AGC level”) in the tuner of the digital broadcast receiver and detecting the detected AGC level. Is compared to a fixed value. In this comparison, if the AGC level is less than the fixed value, a cut-off is performed and it is not determined whether the TS signal is received. Such determination based on the AGC level is equivalent to determination based on the electric field strength of the radio frequency signal estimated from the AGC level, but according to this, a certain frequency channel can be received. Is faster than making a decision based on the TS signal after the establishment of OFDM synchronization.

JP 2004-282221 A. The Japan Radio Industry Association, “Technical Data for Digital Terrestrial Television Broadcasting ARIB TR-B14”, 1.1, Second Volume, 6.2.1 Initial Scan, July 25, 2002.

  However, in digital broadcasting, one-segment (one-segment) broadcasting has a very low carrier power to noise power ratio (C / N) required for reception, which is only slightly higher than the noise level during no signal. It is difficult to determine the presence or absence of a radio frequency signal based on the AGC level. Considering variations in the sensitivity of antennas and tuners used in digital broadcast receivers, the AGC level cannot be cut off at a fixed value. Therefore, it takes a long time to perform channel scanning accurately. Become.

  An object of the present invention is to provide a digital broadcast receiver capable of solving the above-described problems and executing a channel scan accurately in a short time to generate a receivable channel list.

A digital broadcast receiver according to the present invention is a digital broadcast receiver that receives signals of a plurality of frequency channels.
The digital broadcast receiver includes control means for registering a receivable frequency channel among the frequency channels,
The control means determines whether the received signal level of the frequency channel is less than a predetermined first threshold value, and when the received signal level is less than the first threshold value, A first threshold value substantially corresponding to a noise level at the time of no signal is determined by updating the first threshold value with the received signal level.

  In the digital broadcast receiver, the control means has a received signal level for the plurality of frequency channels or for at least one frequency channel selected from the plurality of frequency channels less than the first threshold value. Whether the first threshold value is updated according to the received signal level.

  Further, in the digital broadcast receiver, the control means uses a second threshold value indicating a received signal level necessary for decoding the received signals of the plurality of frequency channels based on the first threshold value. It is characterized by calculating.

  Furthermore, in the digital broadcast receiver, the control means decodes the received signal of the frequency channel after determining whether or not the received signal level of the frequency channel is less than the first threshold value. It is characterized by determining whether or not it is possible. Here, the control means determines that the received signal level of the frequency channel is less than the first threshold value and determines that the received signal of the frequency channel can be decoded. The frequency channel is registered as a receivable frequency channel.

  Instead, in the digital broadcast receiver, the control means determines whether the received signal level of the frequency channel is before determining whether the received signal level of the frequency channel is less than the first threshold value. Whether or not the received signal level of the frequency channel is less than the first threshold value only for the frequency channel of the received signal that cannot be decoded. It is characterized by judging. Here, when it is determined that the received signal of the frequency channel can be decoded, the control means registers the frequency channel as a receivable frequency channel.

  In the digital broadcast receiver, when the reception signal level of the frequency channel is equal to or higher than the second threshold value, it is determined whether the reception signal of the frequency channel is decoded. The frequency channel is registered as a receivable frequency channel. Here, the second threshold value is different depending on a transmission method or a modulation method of a signal of a frequency channel to be received. That is, the second threshold value may be different depending on, for example, a transmission method for 1-segment broadcasting and a transmission method for 12-segment broadcasting. Further, the control means stores the second threshold value in a nonvolatile memory.

  Further, in the digital broadcast receiver, the control means stores the first threshold value in a nonvolatile memory.

Still further, in the digital broadcast receiver, the digital broadcast receiver includes a plurality of tuner means for receiving the received signals received by the plurality of antennas, respectively.
Combining means for combining and outputting the received signals received by the tuner means,
The control means is based on a reception signal received by at least one tuner means of the plurality of tuner means, and the received signal level of the received signal is a predetermined first level substantially corresponding to a noise level. It is determined whether or not the received signal level is lower than the threshold value, and when the received signal level is lower than the first threshold value, reception is possible by updating the first threshold value with the received signal level. A characteristic frequency channel is registered.

  Therefore, according to the present invention, it is possible to correct variations in sensitivity such as antennas and tuners used in digital broadcast receivers and fluctuations in the reception environment, and thereby, radio frequency signals can be corrected based on the first threshold value. Presence or absence can be accurately determined. Also, the second threshold value is calculated based on the first threshold value, and the channel scan is executed based on the calculated second threshold value, so that the channel scan is accurately executed in a short time. A channel list can be generated. Therefore, the digital broadcast receiver of the present invention can detect the presence / absence of a radio frequency signal in a short time even in a one-segment broadcast with a very low carrier power to noise power ratio (C / N) required for reception. It can be judged accurately.

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

First embodiment.
FIG. 1 is a block diagram showing a hardware configuration of a digital broadcast receiver 10 according to the first embodiment of the present invention. The digital broadcast receiver 10 according to the present embodiment includes a controller 16 that registers a receivable frequency channel among a plurality of equipped frequency channels and controls the overall operation of the digital broadcast receiver 10. The controller 16 determines whether or not the received signal levels of the plurality of frequency channels are less than a predetermined first threshold value (minimum AGC level L0 in FIG. 4) substantially corresponding to a noise level at the time of no signal. When the received signal level is less than the first threshold value, the first threshold value is updated with the received signal level, and the received signals of the plurality of frequency channels are decoded. A second threshold value (threshold value T1 or T2 in FIG. 4) indicating a received signal level that is necessary and used for determining the presence or absence of a broadcast wave is set to It is characterized by calculating on the basis of the threshold (L0). The feature according to this embodiment will be described in detail later.

  In FIG. 1, a radio frequency signal of a digital broadcast such as terrestrial digital television broadcast is received by an antenna 1 and then amplified by a low-noise amplifier (LNA) 2 with a built-in antenna. The amplified received signal is a digital broadcast receiver 10. To the wireless input terminal 3. The digital broadcast receiver 10 includes a tuner 11, a demodulator 13, a TS decoder 14, an AV decoder 15, a controller 16, a flash ROM 17, a RAM 18, and an EEPROM 19 connected to the bus 20. The reception signal received via the first is input to the tuner 11 first. The tuner 11 includes an automatic gain control circuit (AGC circuit) 11a, selects a channel having a predetermined frequency from a reception signal input via the wireless input terminal 3, and automatically selects a reception signal of the selected channel. The gain control is executed, and the reception signal subjected to the automatic gain control is output to the demodulator 13 and the AGC circuit voltage (AGC level) at the time of the automatic gain control of the reception signal is output to the controller 16. The demodulator 13 demodulates the received signal of the selected channel from the tuner 11 and outputs the demodulated baseband signal to the TS decoder 14. The TS decoder 14 transports the demodulated baseband signal from the demodulated baseband signal. The stream (TS) signal is decoded and output to the AV decoder 15. The AV decoder 15 decodes the video signal and the audio signal from the decoded TS signal, outputs the video signal from the video output terminal 4, and outputs the audio signal. Output from the audio output terminal 5.

  The controller 16 includes a CPU 16a, determines whether or not there is a receivable frequency channel, and generates a channel list relating to the receivable frequency channel (see FIG. 2) and channel scan processing (see FIG. 3). ) And the overall operation of the digital broadcast receiver 10 is controlled via the bus 20 in response to a user input from the operation unit 21. The flash ROM 17 is a nonvolatile storage device that stores programs and user-specific information, the RAM 18 is a storage device that stores internal information of programs, and the EEPROM 19 is user-specific information and system settings for the digital broadcast receiver 10. It is a non-volatile storage device that stores information and the like. The flash ROM 17 includes a channel list memory 17a that stores a channel scan initial process and a list of receivable frequency channels acquired by the channel scan process, and an EEPROM 19 has threshold values used for the channel scan initial process and the channel scan process. A threshold memory 19a for storing is provided.

  Here, the threshold memory 19a stores an initial minimum AGC level L0 that is preset at the time of shipment of the digital broadcast receiver 10, etc., and this minimum AGC level L0 is executed by the controller 16. Updated by the channel scan initial process and the channel scan process. The threshold memory 19a further stores an AGC level threshold T1 for 1-segment broadcast and an AGC level threshold T2 for 12-segment broadcast, which are calculated by the channel scan initial process and the channel scan process.

  When the digital broadcast receiver 10 of the present embodiment receives radio frequency signals of a plurality of frequency channels, the digital broadcast receiver 10 registers receivable frequency channels among these frequency channels and performs the operation of the entire digital broadcast receiver 10. A controller 16 for controlling, and the controller 16 determines whether or not the AGC level of the received signal of a certain frequency channel is lower than the minimum AGC level L0 that is a predetermined first threshold value. When the level is less than the minimum AGC level L0, the controller 16 updates the minimum AGC level L0 with the received signal level, thereby setting the first threshold value substantially corresponding to the noise level at the time of no signal. A certain minimum AGC level L0 is obtained. In addition, the controller 16 sets second threshold values T1 and T2 that are necessary and sufficient for decoding the reception signals of the plurality of frequency channels and that indicate the AGC level used for determining the presence or absence of broadcast waves, respectively, to a predetermined offset. O1 and O2 are calculated by adding to the minimum AGC level L0, and the AGC level of the received signal of the frequency channel measured by the AGC circuit 11a of the tuner 11 is the threshold value T1 or T2 (threshold for one segment broadcasting). By using the value T1, the threshold value T2 is used for 12-segment broadcasting.) By determining whether or not it is equal to or greater than that, it is determined whether or not the received signal of the frequency channel is decoded (that is, the TS signal is received). And when it is decoded, the frequency channel can be received as a frequency channel that can be received. It is characterized by registering the channel list in the channel list memory 17a Te.

  In the present embodiment, the controller 16 executes the channel scan initial process when the digital broadcast receiver 10 is operated for the first time, for example, when the user purchases the digital broadcast receiver 10 and operates the digital broadcast receiver 10 for the first time. The channel list is generated, the minimum AGC level L0 is measured, and the threshold values T1 and T2 of the AGC level are determined based on the minimum AGC level L0. The channel scan initial process may also be executed when the digital broadcast receiver 10 is moved to a different area, or when a new broadcast station is opened in an area where the digital broadcast receiver 10 is used. . The controller 16 also executes a channel scan process different from the channel scan initial process when the digital broadcast receiver 10 is operated for the second time or later and when the channel list needs to be updated. A channel list is generated based on the AGC level thresholds T1 and T2 determined in the scan initial process, and the minimum AGC level L0 is measured, and the AGC level thresholds T1 and T2 are updated based on the channel list.

  FIG. 2 is a flowchart showing channel scan initial processing executed by the controller 16 of FIG. 1 in the first operation of the digital broadcast receiver 10, and FIG. 3 is executed by the controller 16 of FIG. 1 in the second and subsequent operations. It is a flowchart which shows the channel scan process performed.

  When the digital broadcast receiver 10 is first operated, the controller 16 initializes the contents of the channel list memory 17a and the threshold memory 19a in step S1 of FIG. 2, and then in step S1A, the target of channel scan initial processing is performed. Among the plurality of frequency channels, the frequency channel to be subjected to channel scanning is first selected using the tuner 11. The tuner 11 performs channel selection and simultaneously executes automatic gain control for the received signal of the selected frequency channel, and notifies the controller 16 of the AGC level of the received signal (step S2). In step S3, the controller 16 determines whether or not the AGC level of the received signal is lower than the minimum AGC level L0 preset by the controller 16. If YES, the process proceeds to step S4. If NO, Proceeds directly to step S5. In step S4, the controller 16 updates the minimum AGC level L0 with the AGC level of the received signal acquired in step S2, stores the updated minimum AGC level L0 in the threshold value memory 19a in the EEPROM 19, and proceeds to step S5. move on. In step S5, the TS decoder 14 is monitored to determine whether or not the TS signal has been received within a predetermined time (that is, whether or not the received signal has been decoded). If it is determined that the frequency channel in the station is receivable, the frequency channel currently selected in channel is registered in the channel list on the channel list memory 17a in step S6, and the process proceeds to step S7. The process proceeds to step S7 as it is. In step S7, the controller 16 determines whether or not the currently selected frequency channel is the last frequency channel to be subjected to the channel scan initial process. The tuner 11 is used to select the frequency channel to be scanned, and the process returns to step S2, and if it is the last frequency channel, the process proceeds to step S9. In step S9, the controller 16 adds a predetermined offset O1 to the minimum AGC level L0 to determine whether or not the radio frequency signal of the one-segment broadcast is received with sufficient electric field strength that can be decoded (the presence or absence of the broadcast wave). ) Is calculated, and similarly, a predetermined offset O2 is added to the minimum AGC level L0, so that an electric field necessary and sufficient for decoding a radio frequency signal of 12-segment broadcasting can be obtained. A threshold value T2 of the AGC level for determining whether or not it is received at the strength (presence / absence of broadcast wave) is calculated. The controller 16 stores the calculated AGC level threshold values T1 and T2 in the threshold value memory 19a in the EEPROM 19, and ends the channel scan initial process.

  FIG. 4 is a schematic diagram showing AGC level threshold values (both prior art and this embodiment) set in the digital broadcast receiver 10 of FIG.

  According to the prior art, the threshold values T1 'and T2' of the AGC level used for determining the presence / absence of a broadcast wave in the received digital reception signal are determined as follows. First, in the 12-segment broadcast frequency channel, the broadcast reception limit AGC level L2 is determined depending on the mounted electronic circuit and the like, and as shown in FIG. In consideration of environmental variations, a value that is lower than the reception limit AGC level L2 by a predetermined margin M2 ′ is determined as the AGC level threshold T2 ′ that is used to determine the presence or absence of the broadcast wave of the 12-segment broadcast digital reception signal. It was. Similarly, the reception limit AGC level L1 of the broadcast is determined in the frequency channel of the one-segment broadcast depending on the electronic circuit to be mounted, and as shown in FIG. In consideration of variations in the operating environment, a value that is lower than the reception limit AGC level L1 by a predetermined margin M1 ′ is determined as the AGC level threshold T1 ′ that is used to determine the presence or absence of the broadcast wave of the digital reception signal of one-segment broadcasting. It was done. In this case, the 12 segment broadcast AGC level threshold value T2 ′ cannot cope with variations during operation unless a larger margin M2 ′ is taken into consideration, and the 1 segment broadcast AGC level threshold value T2 ′. Regarding T1 ′, when a relatively large margin M1 ′ is taken into consideration, as shown in FIG. 4, the level is similar to the noise level at the time of no signal, and cannot be determined as the original threshold level. There was a problem that it could not be used practically.

  In order to solve the above problems, in the embodiment according to the present invention, it is considered that predetermined margins M1 and M2 are generated with respect to the reception limit AGC levels L1 and L2, and when no signal is measured at any time. By adding an offset O1 of an AGC level for 1-segment broadcasting and an offset O2 of an AGC level for 12-segment broadcasting, respectively, to the minimum AGC level L0 substantially corresponding to the noise level, An AGC level threshold T1 and a 12 segment broadcast AGC level threshold T2 are calculated. Here, the minimum AGC level L0 indicates the AGC level at the time of no signal (that is, substantially corresponding to the noise level), and the value is preset in the digital broadcast receiver 10 at the time of manufacture and shipment. In order to correct the variation of each product of the antenna 1, the antenna built-in low-noise amplifier 2, and the digital broadcast receiver 10 and the variation of the reception environment, it is updated in the process of step S4 in FIG. In the digital broadcast receiver 10 according to the present embodiment, the reception limit AGC level L1 for 1-segment broadcast and the reception limit AGC level L2 for 12-segment broadcast, which are values determined depending on electronic circuits and the like mounted thereon, are set in advance. If the AGC level of the received signal is equal to or higher than the threshold T1 when determining the presence or absence of a one-segment broadcast radio frequency signal, the electric field strength of the radio frequency signal of the selected frequency channel is sufficient. It is determined that one-segment broadcasting can be received via the frequency channel. On the other hand, if the field strength of the radio frequency signal of the frequency channel being selected is sufficiently higher than the value necessary for receiving the one-segment broadcast, the carrier power to noise power ratio (C / N), and can receive 12-segment broadcasts transmitted at a higher transmission rate than 1-segment broadcasts. In this embodiment, when determining the presence / absence of a radio frequency signal of 12-segment broadcasting, as in the case of 1-segment broadcasting, if the AGC level of the received signal is equal to or higher than the threshold value T2, the frequency channel being selected is selected. Therefore, it is determined that the 12-segment broadcast can be received through the frequency channel. Thus, the AGC level threshold values T1 and T2 are set to be different depending on the transmission method or modulation method of the signal of the frequency channel to be received.

  Next, referring to FIG. 3, in the second and subsequent operations of the digital broadcast receiver 10 for generating a channel list based on the threshold value of the AGC level determined in the channel scan initial process of FIG. The channel scan process will be described. When the digital broadcast receiver 10 is to be operated for the second time or later and the channel list needs to be updated, the controller 16 in step S11 of FIG. First, the tuner 11 is used to select a frequency channel to be subjected to channel scanning. The tuner 11 performs channel selection and simultaneously performs automatic gain control on the received signal of the selected frequency channel, and notifies the controller 16 of the AGC level at this time (step S12). When receiving a 1-segment broadcast reception signal, the controller 16 determines whether or not the AGC level of the reception signal is equal to or higher than the threshold value T1 of the 1-segment broadcast AGC level. When a received signal is received, it is determined whether or not the AGC level of the received signal is equal to or higher than the threshold T2 of the AGC level of 12 segment broadcasting. If YES in step S13, the process proceeds to step S14. If NO, the process proceeds to step S16. In step S14, the controller 16 monitors the TS decoder 14 to determine whether or not the TS signal has been received within a predetermined time. If the TS signal can be received, the currently selected frequency channel can be received. In step S15, the currently selected frequency channel is registered in the channel list on the channel list memory 17a, the process proceeds to step S18, and if it cannot be received, the process proceeds to step S18.

  On the other hand, in step S16, the controller 16 determines whether or not the AGC level is less than the minimum AGC level L0. If YES, the process proceeds to step S17, and if NO, the process proceeds to step S18. In step S17, the controller 16 updates the minimum AGC level L0 with the AGC level of the received signal acquired in step S12, stores the updated minimum AGC level L0 in the threshold value memory 19a in the EEPROM 19, and in step S18. move on. In step S18, the controller 16 determines whether or not the currently selected frequency channel is the last frequency channel to be subjected to the channel scan process. If it is not the last frequency channel, the next channel is selected in step S19. The frequency channel to be scanned is selected using the tuner 11 and the process returns to step S12. If it is the last frequency channel, the process proceeds to step S20. In step S20, the controller 16 adds the predetermined offset O1 to the minimum AGC level L0 to calculate the AGC level threshold value T1 of the one-segment broadcasting, and similarly adds the predetermined offset O2 to the minimum AGC level L0. By doing so, the threshold value T2 of the AGC level of the 12 segment broadcast is calculated. The controller 16 stores the calculated AGC level threshold values T1 and T2 in the threshold value memory 19a in the EEPROM 19, and ends the channel scanning process.

  In the channel scan process of FIG. 3, the controller 16 determines that the frequency channel having the minimum AGC level L0 in the previous channel scan process is no signal, and offsets O1, O2 (one-segment broadcasts) to the minimum AGC level L0. When the 12-segment broadcast is used, the offset O1 is used) and the value obtained by adding the offset O1 is stored in the threshold value memory 19a as the AGC level threshold values T1 and T2. Then, in the next channel scan process, the AGC level of the received signal is cut off based on the threshold value T1 or T2 of the AGC level. According to the present embodiment, by performing the channel scan initial process of FIG. 2, the sensitivity variations of the antenna 1, the antenna built-in low noise amplifier 2, the antenna 1 and the tuner 11 used in the digital broadcast receiver 10, Variations in the reception environment can be corrected, whereby the presence or absence of a radio frequency signal can be accurately determined based on the AGC level. Further, AGC level threshold values T1 and T2 are calculated based on the minimum AGC level L0 acquired in the channel scan initial processing, and the channel scan processing of FIG. 3 is performed based on these AGC level threshold values T1 and T2. By executing the above, it is possible to execute a channel scan accurately in a short time and generate a channel list including receivable frequency channels. Therefore, the digital broadcast receiver 10 of the present embodiment can perform even one-segment broadcasting with a very low carrier power to noise power ratio (C / N) required for reception, that is, as shown in FIG. Even if the minimum AGC level L0 and the threshold value L1 ′ of the prior art are close to each other, the presence / absence of a radio frequency signal is determined using the threshold value T1 considering the offset O1 based on the minimum AGC level L0. Therefore, it has a specific effect that it can be judged accurately in a short time.

  When measuring the minimum AGC level L0, for example, if the radiating portion of the antenna 1 is shielded with an electromagnetic shielding material to block incoming radio waves, a more accurate noise level (thermal noise generated in the circuit of the digital broadcast receiver 10) is obtained. The minimum AGC level L0 can be measured, but in practice, if the minimum AGC level is measured in an unused frequency channel without shielding, it is practically equivalent to a sufficient noise level. It is considered that the minimum AGC level L0 to be measured can be measured.

Second embodiment.
FIG. 5 is a flowchart showing channel scan initial processing according to the second embodiment of the present invention. The same step number as the channel scan initial process in FIG. 2 indicates a step having the same content. When the digital broadcast receiver 10 is first operated, the controller 16 executes steps S1, S1A, and S2 similarly to the channel scan initial process in FIG. 2, and then executes step S5 in FIG. In step S5, the controller 16 monitors the TS decoder 14 to determine whether or not the TS signal has been received within a predetermined time (that is, whether or not the received signal has been decoded). Step S6 is executed and the process proceeds to step S7. If it cannot be received, steps S3 and S4 are executed and the process proceeds to step S7. The processes in steps S7, S8 and S9 are also executed in the same manner as the channel scan initial process in FIG.

  After executing the channel scan initial process as described above in the first operation, the controller 16 executes the channel scan process in the second and subsequent operations described with reference to FIG.

  According to the present embodiment, the processes of steps S3 and S4 are executed only for the frequency channel determined to be unreceivable in step S5. This has an advantage that the processing is faster than the channel scan initial processing of FIG.

Modified example.
In the embodiment described above, a single minimum AGC level L0 is used over the entire frequency band that can be received by the digital broadcast receiver 10. However, since the frequency characteristics are different in different frequency bands, the entire frequency band that can be received by the digital broadcast receiver 10 is divided into a plurality of bands, and the controller 16 calculates and updates the minimum AGC level for each of the divided bands. And calculating and updating the AGC level threshold value based on these minimum AGC levels, respectively.

  In the above embodiment, the minimum AGC level L0 is repeatedly searched and updated for all receivable frequency channels, and the AGC level of each broadcast is determined based on the updated minimum AGC level L0. Although the threshold values T1 and T2 are determined, the present invention is not limited to this, and at least one of a plurality of frequency channels that can be received by the digital broadcast receivers 10 and 10A or a plurality of representative reception frequencies. Channels (for example, a highest frequency channel, an approximately intermediate frequency channel, a lowest frequency channel, etc. may be selected from a plurality of no-signal frequency channels in a predetermined region to be a representative reception frequency channel). Search and update the minimum AGC level L0, and update the minimum A The threshold T1 and T2 of the AGC level for each broadcast may be determined based on the C level L0.

  In the present embodiment, the calculation of the AGC level threshold values T1 and T2 is performed such that margins M1 and M2 are generated between the reception limit AGC levels L1 and L2, respectively. It is not always necessary to consider M2.

  In the digital broadcast receiver 10 of the present embodiment, the AGC level of the AGC circuit 11a is used to execute the channel scan initial process and the channel scan process, but instead of this, other signals such as a received signal strength indication signal (RSSI) are used. The criteria may be used.

  In this embodiment, the AGC level threshold value T1 for 1-segment broadcasting and the AGC level threshold value T2 for 12-segment broadcasting are used, but the channel scan processing of FIG. May be executed. In addition to or instead of these, whether or not the three-segment broadcast can be received by using the AGC level threshold of the three-segment broadcast having a value between the thresholds T1 and T2. May be judged.

FIG. 6 is a block diagram showing a hardware configuration of a digital broadcast receiver 10A according to a modification of the present invention. The digital broadcast receiver 10A in FIG. 6 differs from the digital broadcast receiver 10 in FIG. 1 in that it includes a plurality of M antenna system circuits as described below.
(1) Instead of the antenna 1 and the low-noise amplifier 2 with a built-in antenna, for example, a plurality of M antennas 1-1 to 1-M that form space diversity with each other, and each of the antennas 1-1 to 1-M The antenna-containing low noise amplifiers 2-1 to 2-M are connected.
(2) Instead of the wireless input terminal 3 and the tuner 11 in the digital broadcast receiver 10, a plurality of M wireless input terminals 3-1 to 3-M and a plurality of M independent tuners 11-1 to 11-M And a maximum ratio synthesizer 12.

  In the digital broadcast receiver 10A configured as described above, radio frequency signals of digital broadcasts such as terrestrial digital television broadcasts are received by the antennas 1-1 to 1-M, and then the antenna built-in low noise amplifier (LNA). ) Each of the received signals after being amplified by 2-1 to 2-M and amplified is sent to the AGC circuits 11a-1 to 11a-M via the radio input terminals 3-1 to 3-M of the digital broadcast receiver 10A. Are input to tuners 11-1 to 11-M respectively. Each baseband signal output from each of the tuners 11-1 to 11 -M is input to the maximum ratio synthesizer 12, where the maximum ratio is combined, and then the combined baseband signal is output to the demodulator 13. Here, the channel scan initial processing in FIG. 2 or FIG. 5 and the channel scan processing in FIG. 3 do not need to be executed in the tuners 11-1 to 11-M of the plurality of M antenna system circuits, but at least one If executed in the tuner 11, the minimum AGC level L0 and the AGC level threshold values T1 and T2 can be determined based on the minimum AGC level L0. Therefore, the channel scan initial process and the channel scan process can be efficiently executed in a short time as compared with the case where all of the tuners 11-1 to 11-M execute, and the threshold used for the judgment is cut off. The values T1 and T2 also have a specific effect that the threshold values T1 and T2 necessary for relaxing the determination conditions can be determined.

  The digital broadcast receivers 10 and 10A described above are merely examples, and the digital broadcast receiver of the present invention is not limited to only the embodiments described in the present specification.

  The digital broadcast receivers 10 and 10A described above are not broadcast on all of the plurality of frequency channels of the digital broadcast receivers 10 and 10A, as in the case of channel authorization and operation of the current digital broadcast frequency. As a premise, the threshold value of the AGC level of the 12-segment broadcast and the threshold value of the AGC level of the 1-segment broadcast are determined based on the noise level that is the signal level in the frequency channel that is not broadcast.

It is a block diagram which shows the hardware constitutions of the digital broadcast receiver 10 which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the channel scan initializing process performed by the controller 16 of FIG. It is a flowchart which shows the channel scan process performed by the controller 16 of FIG. It is the schematic which shows the threshold value (both prior art and this embodiment) of the AGC level set to the digital broadcast receiver 10 of FIG. It is a flowchart which shows the channel scan initializing process which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the hardware constitutions of 10 A of digital broadcast receivers which concern on the modification of this invention.

Explanation of symbols

1,1-1 to 1-M ... antenna,
2, 2-1 to 2-M ... LNA with a built-in antenna,
3, 3-1 thru | or 3-M ... wireless input terminal,
4 ... Video output terminal,
5. Audio output terminal,
10, 10A ... Digital broadcast receiver,
11, 11-1 to 11-M ... tuner,
11a, 11a-1 to 11a-M ... AGC circuit,
12: Maximum ratio synthesizer,
13 ... demodulator,
14 ... TS decoder,
15 ... AV decoder,
16 ... Controller,
16a ... CPU,
17 ... Flash ROM,
17a ... Channel list memory,
18 ... RAM,
19… EEPROM,
19a ... threshold memory,
20 ... Bus
21: Operation unit.

Claims (3)

Receiving means for receiving signals of a plurality of frequency channels ;
Detecting means for detecting a received signal level of the signal received by the receiving means;
First storage means for storing a first threshold value corresponding to a noise level at the time of no signal and a second threshold value corresponding to a reception level indicating the presence of a broadcast signal;
Second storage means for storing a channel list including receivable frequency channels;
The first and second threshold values are determined and stored in the first storage means, and each of the frequency channels has a reception signal level equal to or higher than the second threshold value and can be received. a frequency channel and a control means for registering in the channel list,
The control means includes
The received signal level of the frequency channel is determined whether or not less than the first threshold, when the received signal level is below the first threshold, the first threshold value Update according to the received signal level ,
The digital broadcast receiver according to claim 1, wherein the second threshold value is determined by adding a predetermined offset value to the updated first threshold value . When the control means, when the received signal level of the frequency channels is equal to or greater than the second threshold value, the reception signal of the frequency channel is determined whether or not it is possible to decode a decodable, the digital broadcasting receiver as claimed in claim 1, wherein the register to the channel list the frequency channel as a receivable frequency channels. The control means determines whether it is possible to decode the received signal of the frequency channel before determining whether the received signal level of the frequency channel is less than the first threshold value. determination and, only for the frequency channels of the decoded non received signal, according to claim 1, wherein the received signal level of the frequency channel, characterized in that it is determined whether or not less than the first threshold value Digital broadcast receiver.

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