Receiving device and receiving method

Abstract

To provide a receiving device and a receiving method that can prevent a decrease in reception quality caused by intermodulation interference.SOLUTION: A receiving device includes a plurality of tuners that respectively select a plurality of radio waves corresponding to a plurality of tuning frequencies, and a control unit that sets the plurality of tuning frequencies, and changes the setting of at least one tuning frequency included in the plurality of tuning frequencies when the reception quality of at least one radio wave included in the plurality of radio waves does not satisfy a condition after the plurality of tuning frequencies have been set.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present disclosure relates to a receiving device and a receiving method. [Background technology]

[0002] Patent Document 1 discloses a receiver. In the receiver, a main tuner receives broadcast radio waves, and a sub-tuner detects the state of the broadcast radio waves. A tuning frequency control unit seeks and controls the sub-tuner to detect an FM broadcast station that is an intermodulation interference station. When the difference between the frequency of the intermodulation interference station closer to the receiving station among two intermodulation interference stations and the frequency of the receiving station is equal to or less than a first set value, the tuning frequency control unit moves the tuning frequency of the tuning circuit away from the interfering station frequency. When the difference is equal to or more than a second set value, the tuning frequency control unit moves the tuning frequency of the tuning circuit closer to the interfering station frequency. This makes it possible to reduce intermodulation interference (paragraphs 0006, 0012, 0014, and 0015). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-229170 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the receiver disclosed in Patent Document 1, the sub-tuner is used to detect two intermodulation interference stations. Therefore, it is not possible to simultaneously receive broadcast waves from two stations using the main tuner and the sub-tuner. For example, it is not possible to receive broadcast waves for viewing using the main tuner and at the same time receive broadcast waves for recording using the sub-tuner.

[0005] Furthermore, in the receiver disclosed in Patent Document 1, a circuit provided in the receiver must have high accuracy in order to calculate the amount of shift in tuning frequency when moving the tuning frequency away from the jamming station frequency or when moving the tuning frequency closer to the jamming station frequency.

[0006] In view of these problems, an aspect of the present disclosure provides a receiving device and a receiving method that can suppress degradation of reception quality due to intermodulation interference without, for example, adding a special circuit to the receiving device. [Means for solving the problem]

[0007] A receiving device of a first aspect of the present disclosure includes a plurality of tuners that respectively select a plurality of radio waves corresponding to a plurality of tuning frequencies, and a control unit that sets the plurality of tuning frequencies and, when the reception quality of at least one radio wave included in the plurality of radio waves does not satisfy a condition after the plurality of tuning frequencies have been set, changes the setting of at least one tuning frequency included in the plurality of tuning frequencies.

[0008] A receiving method of a second aspect of the present disclosure comprises selecting a plurality of radio waves corresponding to a plurality of tuning frequencies, respectively, setting the plurality of tuning frequencies, and, when the reception quality of at least one radio wave included in the plurality of radio waves does not satisfy a condition after the plurality of tuning frequencies have been set, changing the setting of at least one tuning frequency included in the plurality of tuning frequencies. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing the frequencies of a broadcast wave input to an amplifier provided in a terrestrial digital broadcast receiver and an interference wave output from the amplifier. [Figure 2A] FIG. 1 is a diagram showing broadcast waves of current terrestrial digital broadcasting (hereinafter referred to as "current broadcasting"). [Figure 2B]A diagram showing a broadcast wave having the same center frequency offset as the center frequency offset of the broadcast wave of a current broadcast and a bandwidth wider than the bandwidth of the broadcast wave of the current broadcast. [Figure 2C] FIG. 1 is a diagram showing broadcast waves of advanced terrestrial digital broadcasting (hereinafter referred to as "advanced broadcasting"). [Diagram 3] A diagram showing interference waves, broadcast waves that generate interference waves, broadcast waves of current broadcasts other than the broadcast waves that generate interference waves, and broadcast waves of advanced broadcasts other than the broadcast waves that generate interference waves. [Figure 4] 1 is a table showing the relationship between a broadcast wave selected by a dual tuner provided in a terrestrial digital broadcast receiver and the frequency interval between two adjacent interference waves. [Diagram 5] FIG. 1 is a diagram for explaining intermodulation interference that occurs when only current broadcasting is carried out. [Figure 6] FIG. 1 is a diagram explaining intermodulation interference that occurs when current broadcasting and advanced broadcasting are mixed. [Figure 7] FIG. 2 is a block diagram of a receiving system according to the first embodiment. [Figure 8] 3 is a diagram showing data handled in a receiving device provided in the receiving system of the first embodiment. FIG. [Figure 9] FIG. 2 is a diagram showing the contents of reception quality handled in a receiving device provided in the receiving systems of the first and second embodiments. [Figure 10] FIG. 1 is a diagram showing broadcast waves, as well as the tuning frequencies and frequency bands of a first tuner and a second tuner of a receiving device provided in a receiving system of a first embodiment, (1) at the point when the tuning frequencies of the first tuner and the second tuner are set, (2) at the point when the tuning frequency settings of the first tuner and the second tuner are changed to the higher frequency side, and (3) at the point when the tuning frequency settings of the first tuner and the second tuner are changed to the lower frequency side, and interference waves. [Figure 11] 5 is a flowchart showing a flow of processing performed by a control unit of a receiving device provided in the receiving system of the first embodiment. [Figure 12] 5 is a flowchart showing a flow of processing performed by a control unit of a receiving device provided in the receiving system of the first embodiment. [Figure 13] 4 is a diagram showing a screen that a control unit of a receiving device provided in the receiving system of the first and second embodiments causes to be displayed on a display panel. FIG. [Figure 14] 10 is a flowchart showing a flow of processing performed by a control unit of a receiving device provided in a receiving system according to a first modified example of the first embodiment. [Figure 15] 5 is a flowchart showing the flow of a first loop process performed by a control unit of a receiving device provided in the receiving system of the first embodiment. [Figure 16] 10 is a flowchart showing the flow of a second loop process performed by a control unit of the receiving device provided in the receiving system of the first embodiment. [Figure 17] FIG. 1 is a block diagram of a receiving system according to a reference example. [Figure 18] FIG. 11 is a block diagram of a receiving system according to a second embodiment. [Figure 19] 3 is a diagram showing data handled in a receiving device provided in the receiving system of the first embodiment. FIG. [Figure 20] FIG. 13 is a diagram showing the frequency band of broadcast waves, as well as the tuning frequencies and frequency bands of a first tuner, a second tuner, and a third tuner of a receiving device provided in a receiving system of a second embodiment, and interference waves at (1) the point in time when the tuning frequencies of the first tuner, the second tuner, and the third tuner are set, (2) the point in time when the tuning frequency settings of the first tuner and the second tuner are changed, and (3) the point in time when the tuning frequency setting of the third tuner is changed. [Figure 21] 10 is a flowchart showing a flow of processing performed by a control unit of a receiving device provided in a receiving system of a second embodiment. [Figure 22] 10 is a flowchart showing a flow of processing performed by a control unit of a receiving device provided in a receiving system of a second embodiment. [Diagram 23] 10 is a flowchart showing a flow of processing performed by a control unit of a receiving device provided in a receiving system of a second embodiment. [Figure 24] 10 is a flowchart showing the flow of a first loop process performed by a control unit of a receiving device provided in a receiving system of a second embodiment. [Diagram 25] 10 is a flowchart showing the flow of a second loop process performed by a control unit of a receiving device provided in a receiving system of a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0011] 1. The need for measures against intermodulation interference 1.1 Intermodulation interference FIG. 1 is a diagram showing the frequencies of broadcast waves input to an amplifier provided in a terrestrial digital broadcast receiver and interference waves output from the amplifier.

[0012] 1, when a broadcast wave BW1 of channel CH1 having a frequency f1 and a broadcast wave BW2 of channel CH2 having a frequency f2 are selected by a double tuner provided in a terrestrial digital broadcast receiver, and the broadcast wave BW1 and the broadcast wave BW2 are input to an amplifier provided in the terrestrial digital broadcast receiver, interference waves IW1, IW2, IW3, IW4, etc. having frequencies different from frequency f1 and frequency f2 may be output from the amplifier. The interference waves IW1, IW2, IW3, IW4, etc. that may be output are called intermodulation distortion.

[0013] The frequency interval between two adjacent interference waves included in the interference waves IW1, IW2, IW3, IW4, etc., is equal to the difference f2-f1 between the frequency f1 of the broadcast wave BW1 and the frequency f2 of the broadcast wave BW2.

[0014] If the frequency of interference waves included in interference waves IW1, IW2, IW3, IW4, etc. falls within the frequency band of the broadcast wave you want to receive, and the level of the interference waves is high, problems will occur such as the sensitivity of the terrestrial digital broadcast receiver to the frequency band of the broadcast wave you want to receive being reduced, block noise occurring in the image displayed by the terrestrial digital broadcast receiver due to demodulation errors, and audio output by the terrestrial digital broadcast receiver being cut off due to demodulation errors. Furthermore, if the situation worsens further, problems will occur such as the terrestrial digital broadcast receiver being unable to maintain tuning to the broadcast wave you want to receive. The occurrence of these problems is called intermodulation interference.

[0015] 1.2 Advances in terrestrial digital broadcasting FIG. 2A is a diagram showing broadcast waves of current terrestrial digital broadcasting (hereinafter referred to as "current broadcasting").

[0016] As shown in FIG. 2A, the channel assigned to the current broadcast wave BW11 has a channel width of 6 MHz. The current broadcast wave BW11 has a bandwidth of 5.57 MHz, which is necessary for 2K broadcasting. The center frequency of the current broadcast wave BW11 is offset by 1 / 7 MHz from the center frequency of the channel to the higher frequency side. For example, the center frequency of the current broadcast wave BW11, which is assigned to the U16 channel, is 491.143 MHz, which is offset by 1 / 7 MHz from the center frequency of the U16 channel, 491 MHz.

[0017] FIG. 2B is a diagram showing a broadcast wave having the same center frequency offset as the center frequency offset of the broadcast wave of the current broadcast and a bandwidth wider than the bandwidth of the broadcast wave of the current broadcast.

[0018] In order to improve terrestrial digital broadcasting, it is being considered to widen the bandwidth of the broadcast wave from 5.57MHz to 5.83MHz. However, as shown in Fig. 2B, if the bandwidth of the broadcast wave BW12 is widened to 5.83MHz without changing the offset of the center frequency of the broadcast wave BW12, the upper end frequency of the broadcast wave BW12 will be higher than the upper end frequency of the channel assigned to the broadcast wave BW12. For example, the difference between the upper end frequency of the broadcast wave BW12 to which the U16 channel is assigned and the center frequency of the U16 channel (1 / 7+5.83 / 2=3.05MHz) is larger than the difference between the upper end frequency of the U16 channel and the center frequency of the U16 channel (6 / 2=3MHz).

[0019] FIG. 2C is a diagram showing broadcast waves of advanced terrestrial digital broadcasting (hereinafter, referred to as "advanced broadcasting").

[0020] Therefore, as shown in Fig. 2C, the center frequency of the advanced broadcasting airwave BW13 is offset by 1 / 18 MHz toward the higher frequency side from the center frequency of the channel assigned to the advanced broadcasting airwave BW13. For example, the center frequency 491.056 MHz of the advanced broadcasting airwave BW13 to which the U16 channel is assigned is offset by 1 / 18 MHz toward the higher frequency side from the center frequency 491 MHz of the U16 channel. By reducing the offset from 1 / 7 MHz to 1 / 18 MHz in this way, the upper end frequency of the advanced broadcasting airwave BW13 becomes lower than the upper end frequency of the channel assigned to the advanced broadcasting airwave BW13.

[0021] 1.3 Increase in channels broadcasting FIG. 3 is a diagram showing interference waves, broadcast waves that generate interference waves, broadcast waves of current broadcasting other than the broadcast waves that generate interference waves, and broadcast waves of advanced broadcasting other than the broadcast waves that generate interference waves.

[0022] The modulation method of advanced broadcasting is different from that of current broadcasting. Therefore, as shown in FIG. 3, channels that are not assigned to the broadcast wave BW11 of current broadcasting are assigned to the broadcast wave BW13 of advanced broadcasting. Therefore, when current broadcasting and advanced broadcasting are performed together, the number of channels assigned to the broadcast wave BW10 doubles within the frequency band of terrestrial digital broadcasting from 470 to 710 MHz. Therefore, the frequency of the interference wave IW2 generated by the broadcast wave BW1 having the frequency f1 and the broadcast wave BW2 having the frequency f2 is likely to fall within the frequency band of the broadcast wave BW10. Therefore, when current broadcasting and advanced broadcasting are performed together, the broadcast wave to be received is likely to be subjected to intermodulation interference.

[0023] 1.4 Increase in the types of interference waves FIG. 4 is a table showing the relationship between a broadcast wave selected by a dual tuner provided in a terrestrial digital broadcast receiver and the frequency interval between two adjacent interference waves.

[0024] As shown in Figure 4, when the broadcast wave BW1 selected by the double tuner is a broadcast wave of a current broadcast having a center frequency of f1 + 1 / 7 (MHz), and the broadcast wave BW2 selected by the double tuner is a broadcast wave of a current broadcast having a center frequency of f2 + 1 / 7 (MHz), the frequency interval between two adjacent interference waves IWB generated matches the difference f2 - f1 (MHz) between the center frequency f1 + 1 / 7 (MHz) of the broadcast wave BW1 and the center frequency f2 + 1 / 7 (MHz) of the broadcast wave BW2.

[0025] Furthermore, if the broadcast wave BW1 is a current broadcast wave having a center frequency of f1+1 / 7 (MHz) and the broadcast wave BW2 is an advanced broadcast wave having a center frequency of f2+1 / 18 (MHz), the frequency interval between two adjacent interference waves IWA that are generated will be equal to the difference f2-f1-11 / 126 (MHz) between the center frequency f1+1 / 7 (MHz) of the broadcast wave BW1 and the center frequency f2+1 / 18 (MHz) of the broadcast wave BW2.

[0026] Furthermore, if the broadcast wave BW1 is an advanced broadcast wave having a center frequency of f1+1 / 18 (MHz) and the broadcast wave BW2 is a current broadcast wave having a center frequency of f2+1 / 7 (MHz), the frequency interval between two adjacent interference waves IWC generated will be equal to the difference f2-f1+11 / 126 (MHz) between the center frequency f1+1 / 18 (MHz) of the broadcast wave BW1 and the center frequency f2+1 / 7 (MHz) of the broadcast wave BW2.

[0027] Furthermore, when the broadcast wave BW1 is an advanced broadcast wave having a center frequency of f1+1 / 18 (MHz) and the broadcast wave BW2 is an advanced broadcast wave having a center frequency of f2+1 / 18 (MHz), the frequency interval between two adjacent interference waves IWB' generated matches the difference f2-f1 (MHz) between the center frequency f1+1 / 18 (MHz) of the broadcast wave BW1 and the center frequency f2+1 / 18 (MHz) of the broadcast wave BW2.

[0028] Therefore, the frequency interval between two adjacent interference waves IWA and the frequency interval between two adjacent interference waves IWC are different from the frequency interval between two adjacent interference waves IWB and the frequency interval between two adjacent interference waves IWB'. Therefore, the harmonic frequencies of the interference waves IWA and IWC are different from the harmonic frequencies of the interference waves IWB and IWB'. Also, the frequency interval between two adjacent interference waves IWB and the frequency interval between two adjacent interference waves IWB' are the same, but the starting frequency of the row of the interference wave IWB and the starting frequency of the row of the interference wave IWB' are different from each other. Therefore, the harmonic frequencies of the interference waves IWB and IWB' are different from each other. For these reasons, the harmonic frequencies of the interference waves IWA, IWB, IWB', and IWC are different from each other. Therefore, when only current broadcasting is performed, only one type of interference wave, the interference wave IWB, occurs, whereas when current broadcasting and advanced broadcasting are performed together, four types of interference waves, the interference waves IWA, IWB, IWB', and IWC, occur. Therefore, when current broadcasting and advanced broadcasting are performed together, there is a high possibility that the broadcast wave you want to receive will be subject to intermodulation interference.

[0029] 1.5 Intermodulation interference occurring when only current broadcasts are being transmitted FIG. 5 is a diagram for explaining intermodulation interference that occurs when only the current broadcast is being carried out.

[0030] As shown in Fig. 5, when the selected channel of a first tuner provided in a terrestrial digital broadcasting receiver is U13 channel assigned to the current broadcasting, and the selected frequency of the first tuner is 473+1 / 7 (MHz), and the selected channel of a second tuner provided in the terrestrial digital broadcasting receiver is U14 channel assigned to the current broadcasting, and the selected frequency of the second tuner is 479+1 / 7 (MHz), an interference wave IWB is generated. The frequency interval between two adjacent interference waves IWB is 6.000 MHz. The harmonic frequency of the interference wave IWB is 479.143+n*6.000 (MHz), where n is an integer equal to or greater than 1.

[0031] The interference wave that occurs is one type of interference wave consisting of an interference wave IWB.

[0032] The harmonic frequencies of the interference wave IWB are 485.143 MHz, , 527.143 MHz, , 599.143 MHz, , 707.143, , MHz when n is 1, , 8, , 20, , 38, , respectively.

[0033] When n is 8, the harmonic frequency of the IWB interference wave, 527.143 MHz, falls within the frequency band of the U22 channel. When n is 20, the harmonic frequency of the IWB interference wave, 599.143 MHz, falls within the frequency band of the U34 channel. Therefore, the U22 channel and the U34 channel may be subject to intermodulation interference.

[0034] The harmonic frequency of the IWB interference wave, 527.143 MHz, which may cause intermodulation interference to the U22 channel, coincides with the center frequency of the U22 channel, 527.143 MHz. The harmonic frequency of the IWB interference wave, 599.143 MHz, which may cause intermodulation interference to the U34 channel, coincides with the center frequency of the U34 channel, 599.143 MHz.

[0035] In this way, when only the current broadcast is being performed, there is only one type of interference wave that may cause intermodulation interference to the channel. Furthermore, the harmonic frequency of the interference wave coincides with the center frequency of the channel. Therefore, the position of the harmonic frequency of the interference wave within the frequency band of the channel is fixed. Therefore, by providing a filter that attenuates a signal having a specific frequency inside a tuner module having a first tuner and a second tuner, it is possible to attenuate the interference wave that may cause intermodulation interference to the channel, and easily prevent the channel from being subjected to intermodulation interference.

[0036] 1.6 Intermodulation interference occurring when current broadcasting and advanced broadcasting are mixed FIG. 6 is a diagram for explaining intermodulation interference that occurs when current broadcasting and advanced broadcasting are carried out together.

[0037] As shown in Fig. 6, when the selected channel of a first tuner provided in a terrestrial digital broadcasting receiver is U13 channel assigned to the current broadcasting, and the selected frequency of the first tuner is 473+1 / 7 (MHz), and the selected channel of a second tuner provided in the terrestrial digital broadcasting receiver is U14 channel assigned to the current broadcasting, and the selected frequency of the second tuner is 479+1 / 7 (MHz), an interference wave IWB is generated. The frequency interval between two adjacent interference waves IWB is 6.000 MHz. The harmonic frequency of the interference wave IWB is 479.143+n*6.000 (MHz), where n is an integer equal to or greater than 1.

[0038] In addition, when the selected channel of the first tuner is channel U13 assigned to current broadcasting, the selected frequency of the first tuner is 473+1 / 7 (MHz), and the selected channel of the second tuner is channel U14 assigned to advanced broadcasting, and the selected frequency of the second tuner is 479+1 / 18 (MHz), an interference wave IWA occurs. The frequency interval between two adjacent interference waves IWA is 5.913 MHz. The harmonic frequency of the interference wave IWA is 479.056+n*5.913 (MHz), where n is an integer equal to or greater than 1.

[0039] In addition, when the selected channel of the first tuner is U13 channel assigned to advanced broadcasting and the selected frequency of the first tuner is 473+1 / 18 (MHz), and the selected channel of the second tuner is U14 channel assigned to current broadcasting and the selected frequency of the second tuner is 479+1 / 7 (MHz), an interference wave IWC is generated. The frequency interval between two adjacent interference waves IWC is 6.087 MHz. The harmonic frequency of the interference wave IWC is 479.143+n*6.087 (MHz), where n is an integer equal to or greater than 1.

[0040] In addition, when the selected channel of the first tuner is channel U13 assigned to advanced broadcasting and the selected frequency of the first tuner is 473+1 / 18 (MHz), and the selected channel of the second tuner is channel U14 assigned to advanced broadcasting and the selected frequency of the second tuner is 479+1 / 18 (MHz), an interference wave IWB' is generated. The frequency interval between two adjacent interference waves IWB' is 6.000 MHz. The harmonic frequency of the interference wave IWB' is 479.056+n*6.000 (MHz), where n is an integer equal to or greater than 1.

[0041] The interference waves that occur are four types of interference waves IWA, IWB, IWB', and IWC.

[0042] The harmonic frequencies of the interference wave IWA are 484.969 MHz, 523.360 MHz, 597.316 MHz, 703.750 MHz, and when n is 1, 8, 20, 38, and respectively.

[0043] The harmonic frequencies of the interference wave IWB are 485.143 MHz, , 527.143 MHz, , 599.143 MHz, , 707.143 MHz, and when n is 1, , 8, , 20, , 38, and so on, respectively.

[0044] The harmonic frequencies of the interference wave IWB' are 485.056 MHz, 527.056 MHz, 599.056 MHz, 707.056 MHz, and when n is 1, 8, 20, 38, and respectively.

[0045] The harmonic frequencies of the interference wave IWC are 485.230 MHz, 527.839 MHz, 600.883 MHz, and 710.449 MHz when n is 1, 8, 20, 38, and so on, respectively.

[0046] When n is 8, the harmonic frequencies of the interference waves IWA, IWB, IWB', and IWC, 523.360 MHz, 527.143 MHz, 527.056 MHz, and 527.839 MHz, fall within the frequency band of the U22 channel. When n is 20, the harmonic frequencies of the interference waves IWA, IWB, IWB', and IWC, 597.316 MHz, 599.143 MHz, 599.056 MHz, and 600.883 MHz, fall within the frequency band of the U34 channel. For this reason, the U22 channel and the U34 channel may be subject to intermodulation interference.

[0047] The harmonic frequency 527.143MHz of the interference wave IWB, which may cause intermodulation interference to the U22 channel, coincides with the center frequency 527.143MHz of the U22 channel. However, the harmonic frequencies 523.360MHz, 527.056MHz, and 527.839MHz of the interference waves IWA, IWB', and IWC, which may cause intermodulation interference to the U22 channel, do not coincide with the center frequency 527.143MHz of the U22 channel. The harmonic frequency 599.143MHz of the interference wave IWB, which may cause intermodulation interference to the U34 channel, coincides with the center frequency 599.143MHz of the U34 channel. However, the harmonic frequencies 597.316MHz, 599.056MHz, and 600.883MHz of the interference waves IWA, IWB', and IWC, which may cause intermodulation interference to the U34 channel, do not coincide with the center frequency 599.143MHz of the U34 channel.

[0048] Thus, when current broadcasting and advanced broadcasting are mixed, there are four types of interference waves that may cause intermodulation interference to a channel. In addition, the harmonic frequency of the interference wave that may cause intermodulation interference to a channel does not necessarily match the center frequency of the channel. Therefore, the position of the harmonic frequency of the interference wave within the frequency band of the channel is not fixed. Therefore, it is not easy to prevent the channel from receiving intermodulation interference by attenuating the interference wave that may cause intermodulation interference to the channel by providing a filter that attenuates a signal having a specific frequency inside a tuner module that includes a first tuner and a second tuner.

[0049] The first and second embodiments described below are suitable for suppressing a channel from being subjected to the above-mentioned intermodulation interference.

[0050] 2. First embodiment 2.1 Receiving System FIG. 7 is a block diagram of the receiving system according to the first embodiment.

[0051] The receiving system 1 of the first embodiment shown in Fig. 7 is a receiving system for terrestrial digital broadcasting. Therefore, the receiving system 1 receives broadcast waves of terrestrial digital broadcasting, displays video corresponding to the received broadcast waves, and outputs audio corresponding to the received broadcast waves. The receiving system 1 may be a receiving system for satellite digital broadcasting.

[0052] As shown in FIG. 7, the receiving system 1 includes an antenna device 11, a receiving device 12, and an external recording device 13.

[0053] The antenna device 11 receives broadcast waves and outputs a radio frequency (RF) signal corresponding to the received broadcast waves.

[0054] The receiving device 12 is a terrestrial digital broadcast receiver. The receiving device 12 is a television receiver. Therefore, the receiving device 12 displays video corresponding to the output RF signal and outputs audio corresponding to the output RF signal. The receiving device 12 also outputs video / audio signals for recording corresponding to the output RF signal.

[0055] The external recording device 13 is connected to the receiving device 12. The external recording device 13 records video / audio data corresponding to the output video / audio signals for recording. In this way, the external recording device 13 can record the broadcast. The external recording device 13 may be built into the receiving device 12.

[0056] The receiving device 12 is a receiving device equipped with a double tuner. Therefore, the receiving device 12 can simultaneously display video corresponding to the first broadcast wave, output audio corresponding to the first broadcast wave, and output video / audio signals for recording corresponding to the second broadcast wave to cause the external recording device 13 to record the broadcast broadcast by the second broadcast wave.

[0057] 7, antenna device 11 includes antenna 21 and booster 22. Antenna 21 receives broadcast waves and outputs an RF signal corresponding to the received broadcast waves. Booster 22 amplifies the output RF signal and outputs the RF signal output from antenna device 11. Booster 22 may be omitted.

[0058] 2.2 Receiving equipment As shown in FIG. 7, the receiving device 12 includes a main system 31, a display panel 32, a speaker 33, an output terminal 34, a transmitting / receiving module 35, and a remote controller 36.

[0059] The main system 31 receives an RF signal output by the antenna device 11. The main system 31 outputs a video signal for viewing, an audio signal for viewing, and a video / audio signal for recording in accordance with the input RF signal. The main system 31 receives a signal output by a transmission / reception module 35. The main system 31 may be built into a device other than a television receiver. For example, the main system 31 may be built into an external tuner, a personal computer, etc.

[0060] The display panel 32 displays an image according to the output video signal for viewing.

[0061] The speaker 33 outputs sound corresponding to the output audio signal for viewing.

[0062] The output terminal 34 outputs the output video / audio signals for recording. The external recording device 13 is connected to the output terminal 34. This allows the output terminal 34 to input the video / audio signals for recording to the external recording device 13.

[0063] The remote controller 36 transmits a remote control signal in response to an operation performed on the remote controller 36 by the user.

[0064] The transmitting / receiving module 35 outputs a signal corresponding to the transmitted remote control signal.

[0065] 2.3 Main System 7, the main system 31 includes a first tuner 41, a second tuner 42, a first demodulation unit 51, a second demodulation unit 52, a descrambling / demultiplexing unit 61, a video processing unit 62, an audio processing unit 63, an output processing unit 64, a flash memory 65, a storage unit 66, a high-speed digital interface (high-speed digital I / F) 67, and a control unit 68. The first tuner 41 and the second tuner 42 are built into a tuner module 71. Data 81 is stored in the flash memory 65. A control program 91 is stored in the storage unit 66.

[0066] The first tuner 41 and the second tuner 42 select first and second frequency components belonging to first and second frequency bands determined by tuning frequencies TF1 and TF2, respectively, from the RF signal input to the main system 31. As a result, the first tuner 41 and the second tuner 42 select first and second radio waves according to the tuning frequencies TF1 and TF2, respectively. As a result, the first tuner 41 and the second tuner 42 can tune to the first and second broadcast waves, respectively.

[0067] The first tuner 41 and the second tuner 42 generate first and second intermediate frequency (IF) signals from the selected first and second frequency components, respectively.

[0068] The first tuner 41 and the second tuner 42 are respectively constituted by first and second circuits that are independent of each other.

[0069] Each of the first tuner 41 and the second tuner 42 is a general tuner, and therefore each of the first tuner 41 and the second tuner 42 includes a tuning circuit, a local oscillation circuit, a mixing circuit, an amplifier circuit, and the like.

[0070] The tuner module 71 is a single circuit component. The tuner module 71 includes a metal shield that shields the first tuner 41 and the second tuner 42.

[0071] The first demodulation section 51 and the second demodulation section 52 demodulate the generated first and second IF signals into first and second baseband signals, respectively.

[0072] The first tuner 41 and the first demodulation unit 51 have a tuning pull-in performance. Therefore, even if the tuning frequency TF1 deviates from the center frequency of the broadcast wave to be received, the first tuner 41 and the first demodulation unit 51 can maintain a stable tuning state to the broadcast wave to be received as long as the deviation of the tuning frequency TF1 from the center frequency of the broadcast wave to be received does not exceed the tuning pull-in performance. Similarly, the second tuner 42 and the second demodulation unit 52 have a tuning pull-in performance. Therefore, even if the tuning frequency TF2 deviates from the center frequency of the broadcast wave to be received, the second tuner 42 and the second demodulation unit 52 can maintain a stable tuning state to the broadcast wave to be received as long as the deviation of the tuning frequency TF2 from the center frequency of the broadcast wave to be received does not exceed the tuning pull-in performance.

[0073] The descrambling / demultiplexing unit 61 performs descrambling and demultiplexing on the demodulated first baseband signal to generate video and audio signals for viewing. The descrambling / demultiplexing unit 61 performs descrambling and demultiplexing on the demodulated second baseband signal to generate video and audio signals for recording.

[0074] The video processor 62 processes the video signal for viewing, and uses the processed video signal to drive the display panel 32. In this way, the video processor 62 causes the display panel 32 to display an image corresponding to the first broadcast wave.

[0075] The audio processor 63 processes an audio signal for viewing and driving the speaker 33 with the processed audio signal. In this way, the audio processor 63 causes the speaker 33 to output audio corresponding to the first broadcast wave.

[0076] The output processing unit 64 processes the video / audio signals for recording, and supplies the processed video / audio signals to the output terminal 34. As a result, the output processing unit 64 causes the output terminal 34 to output video / audio signals corresponding to the second broadcast wave.

[0077] The first tuner path passing through the first tuner 41 and the first demodulation unit 51 is used for channel selection processing for viewing. The second tuner path passing through the second tuner 42 and the second demodulation unit 52 is used for channel selection processing for recording. The tuner paths used for channel selection processing for viewing and channel selection processing for recording are fixed. The tuner paths used for channel selection processing for viewing and channel selection processing for recording may be adaptively changed. In this case, the output destination of the signal generated by performing descrambling processing and demultiplexing processing on the baseband signal is switched between the video processing unit 62 and the audio processing unit 63 and the output processing unit 64.

[0078] The second tuner path may be used for channel selection processing as internal processing of the receiving device 12, such as channel search, program guide acquisition, and the like.

[0079] The first tuner 41 and the first demodulation unit 51 are controlled to be inactive during a period when the first tuner path is not used for channel selection processing. The second tuner 42 and the second demodulation unit 52 are controlled to be inactive during a period when the second tuner path is not used for channel selection processing.

[0080] The flash memory 65 serves as a storage unit that stores the written data 81. The flash memory 65 may be replaced with another type of storage element that serves as a storage unit.

[0081] The storage unit 66 stores a control program 91. The storage unit 66 is a random access memory (RAM), a read-only memory (ROM), or the like.

[0082] The high-speed digital I / F 67 provides an interface to which the transmission / reception module 35 is connected.

[0083] The control unit 68 controls the first tuner 41, the second tuner 42, the first demodulation unit 51, the second demodulation unit 52, the descrambling / demultiplexing unit 61, the video processing unit 62, the audio processing unit 63, the output processing unit 64 and the high-speed digital I / F 67.

[0084] The control unit 68 writes data 81 to the flash memory 65 and reads the written data 81 from the flash memory 65 .

[0085] The control unit 68 includes a processor and peripheral circuits. The processor executes a control program 91 to cause the processor and the peripheral circuits to operate as the control unit 68. All or part of the processing performed by the processor may be performed by a dedicated electronic circuit.

[0086] The control unit 68 receives a signal via the high-speed digital I / F 67 and performs control in accordance with the received signal, thereby performing control in accordance with an operation performed on the remote controller 36 by the user.

[0087] 2.4 Data handled by receiving devices FIG. 8 is a diagram showing data handled in the receiving device included in the receiving system of the first embodiment.

[0088] As shown in FIG. 8, the control unit 68 sets the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42. When a channel for viewing is selected by a user's operation, the control unit 68 sets the tuning frequency TF1 to the frequency of the selected channel for viewing. This allows the control unit 68 to display on the display panel 32 an image corresponding to the broadcast wave broadcast on the channel for viewing selected by a user's operation, and to output to the speaker 33 an audio corresponding to the broadcast wave. In addition, when a channel for recording is selected by a user's operation, the control unit 68 sets the tuning frequency TF2 to the frequency of the selected channel for recording. This allows the control unit 68 to record on the external recording device 13 the broadcast carried out on the channel for recording selected by a user's operation.

[0089] The control unit 68 acquires the first synchronization information 101 and the second synchronization information 102 from the first demodulation unit 51 and the second demodulation unit 52, respectively. Based on the acquired first synchronization information 101 and second synchronization information 102, the control unit 68 determines whether or not there are broadcast waves for broadcasting on the selected channel for viewing and channel for recording.

[0090] The control unit 68 acquires the first broadcast data 111 and the second broadcast data 112 from the first demodulation unit 51 and the second demodulation unit 52, respectively. Based on the acquired first broadcast data 111 and second broadcast data 112, the control unit 68 determines whether or not it is possible to select broadcast waves broadcasting on the selected channel for viewing and channel for recording.

[0091] The control unit 68 acquires, from the first tuner 41 and the first demodulation unit 51, a first reception quality 121 of the first radio wave selected by the first tuner 41, and monitors the reception state of the first radio wave. Also, the control unit 68 acquires, from the second tuner 42 and the second demodulation unit 52, a second reception quality 122 of the second radio wave selected by the second tuner 42, and monitors the reception state of the second radio wave.

[0092] 2.5 Reception Quality FIG. 9 is a diagram showing the contents of reception quality handled in the receiving device provided in the receiving system of the first embodiment.

[0093] As shown in FIG. 9, each of the first reception quality 121 and the second reception quality 122 includes at least one selected from the group consisting of signal strength 131, carrier-to-noise ratio (C / N ratio) 132, bit error rate (BER) 133, modulation error ratio (MER) 134, carrier interference monitor 135, multipath interference monitor 136, and inter-symbol interference monitor 137.

[0094] The signal strength 131 included in the first reception quality 121 is obtained from the first tuner 41. The C / N ratio 132, the BER 133, the MER 134, the carrier interference monitor 135, the multipath interference monitor 136 and the inter-symbol interference monitor 137 included in the first reception quality 121 are obtained from the first demodulation unit 51.

[0095] The signal strength 131 included in the second reception quality 122 is obtained from the second tuner 42. The C / N ratio 132, the BER 133, the MER 134, the carrier interference monitor 135, the multipath interference monitor 136 and the inter-symbol interference monitor 137 included in the second reception quality 122 are obtained from the second demodulation unit 52.

[0096] 2.6 Changing the tuning frequency setting FIG. 10 is a diagram showing broadcast waves, as well as the tuning frequencies and frequency bands of the first and second tuners of a receiving device provided in a receiving system of the first embodiment, (1) when the tuning frequencies of the first and second tuners are set, (2) when the tuning frequency settings of the first and second tuners are changed to the higher frequency side, and (3) when the tuning frequency settings of the first and second tuners are changed to the lower frequency side.

[0097] In the following, as shown in Figure 10, it is assumed that broadcasting is carried out on channel CH1 using broadcast wave BW21 having frequency f1, broadcasting is carried out on channel CH2 using broadcast wave BW22 having frequency f2, and broadcasting is carried out on channel CH3 using broadcast wave BW23 having frequency f3.

[0098] Generally, the tuning frequency of a tuner is set to a frequency obtained by increasing or decreasing the IF frequency of the IF signal output by the tuner relative to the center frequency of the broadcast wave to be received. However, in the following, for the sake of simplicity, it is assumed that the tuning frequency of the tuner is set to the center frequency of the broadcast wave to be received. This corresponds to the case where the IF frequency is set to 0.

[0099] 10, the control unit 68 sets two tuning frequencies TF1 and TF2. When setting the tuning frequencies TF1 and TF2, the control unit 68 sets the tuning frequencies TF1 and TF2 to, for example, frequencies f1 and f3, respectively. In this case, for example, intermodulation distortion occurs between a signal having a frequency f1 emitted by the first tuner 41 and a broadcast wave BW2 having a frequency f2, generating interference waves IW2, IW4, etc.

[0100] 10, when at least one of the reception qualities included in the first reception quality 121 and the second reception quality 122 (hereinafter referred to as the "reception quality to be evaluated") satisfies the condition in the state where the tuning frequencies TF1 and TF2 are set, the control unit 68 maintains the state where the tuning frequencies TF1 and TF2 are set. When the reception quality to be evaluated does not satisfy the condition in the state where the tuning frequencies TF1 and TF2 are set, the control unit 68 changes the setting of at least one of the tuning frequencies included in the tuning frequencies TF1 and TF2 (hereinafter referred to as the "tuning frequency to be changed in setting").

[0101] When the setting of the tuning frequency to be changed is changed, at least one of the following moves: at least one frequency band included in the frequency band FB1 of the first tuner 41 and the frequency band FB2 of the second tuner 42 (hereinafter referred to as the "frequency band FB to be evaluated"), and the frequency of the interference wave included in the interference waves IW2, IW4, etc. (hereinafter referred to as the "frequency of the problematic interference wave IW"). Therefore, even if the frequency of the problematic interference wave IW falls within the frequency band FB to be evaluated at the time when the tuning frequencies TF1 and TF2 are set and the reception quality of the evaluation target does not satisfy the condition, it is possible to move the frequency of the problematic interference wave IW outside the frequency band FB to be evaluated by changing the setting of the tuning frequency to be changed and relatively move the frequency band FB to be evaluated and the frequency of the problematic interference wave IW, so that the reception quality of the evaluation target satisfies the condition. 10, even if the frequency of the interference wave IW2 is within the frequency band FB2 of the second tuner 42 when the tuning frequencies TF1 and TF2 are set to frequencies f1 and f3, respectively, the frequency of the interference wave IW2 can be moved out of the frequency band FB2 of the second tuner 42 by setting the tuning frequencies TF1 and TF2 to frequencies f1-fstep*n and f3-fstep*n, respectively. The control unit 68 utilizes this to search for settings of the tuning frequencies TF1 and TF2 that can move the frequency of the problematic interference wave IW out of the frequency band FB that is the target of the evaluation.

[0102] In the first embodiment, the frequency band FB to be evaluated is one of the two frequency bands FB1 and FB2 that the two tuners 41 and 42 have, respectively. Therefore, the reception quality to be evaluated is the reception quality of one of the two radio waves selected by the two tuners 41 and 42, respectively. However, the frequency band FB to be evaluated may be the two frequency bands FB1 and FB2. Therefore, the reception quality to be evaluated may be the reception quality of the two radio waves.

[0103] In the first embodiment, the reception quality to be evaluated is the C / N ratio 132 and the BER 133 included in the second reception quality 122. However, the reception quality to be evaluated may be another reception quality.

[0104] In the first embodiment, the condition that the reception quality to be evaluated must satisfy is that the C / N ratio 132 included in the second reception quality 122 is equal to or greater than the set C / N ratio, and the BER 133 included in the second reception quality 122 is equal to or less than the set BER. The condition that the reception quality to be evaluated must satisfy may be another condition. The set C / N ratio and the set BER may be the initial C / N ratio 132 and BER 133 acquired in a state in which the problematic interference wave IW is not generated.

[0105] In the first embodiment, changing the setting of the tuning frequency to be changed includes changing the setting of the tuning frequency TF1 to be the first tuning frequency, and if the reception quality of the evaluation target satisfies the condition in the state where the setting of the tuning frequency TF1 has been changed, maintaining the state where the tuning frequencies TF1 and TF2 have been set. Also, changing the setting of the tuning frequency to be changed includes changing the setting of the tuning frequency TF1, and if the reception quality of the evaluation target does not satisfy the condition in the state where the setting of the tuning frequency TF1 has been changed, further changing the setting of the tuning frequency TF2 to be the second tuning frequency. As a result, if the reception quality of the evaluation target can satisfy the condition by only changing the setting of the tuning frequency TF1, only the setting of the tuning frequency TF1 is changed, and if the reception quality of the evaluation target cannot satisfy the condition by only changing the setting of the tuning frequency TF1, the settings of the tuning frequencies TF1 and TF2 are changed. This makes it possible to minimize the change of the setting. However, changing the setting of the tuning frequency to be changed may be something else.

[0106] In the first embodiment, changing the setting of the tuning frequency TF1 includes changing the setting of the tuning frequency TF1 to the higher frequency side and changing the setting of the tuning frequency TF1 to the lower frequency side. When changing the setting of the tuning frequency TF1 to the higher frequency side, the control unit 68 sets the tuning frequency TF1 to, for example, a frequency f1+fstep*n. When changing the setting of the tuning frequency TF1 to the lower frequency side, the control unit 68 sets the tuning frequency TF1 to, for example, a frequency f1-fstep*n. Here, n is an integer equal to or greater than 1.

[0107] In the first embodiment, changing the setting of the tuning frequency TF2 includes changing the setting of the tuning frequency TF2 to the higher frequency side and changing the setting of the tuning frequency TF2 to the lower frequency side. When changing the setting of the tuning frequency TF2 to the higher frequency side, the control unit 68 sets the tuning frequency TF2 to, for example, a frequency f3+fstep*n. When changing the setting of the tuning frequency TF2 to the lower frequency side, the control unit 68 sets the tuning frequency TF2 to, for example, a frequency f3-fstep*n. Here, n is an integer equal to or greater than 1.

[0108] In the first embodiment, when the control unit 68 changes the tuning frequency TF1 to the higher frequency side in the change of the tuning frequency TF1 setting, the control unit 68 changes the tuning frequency TF2 to the higher frequency side in the change of the tuning frequency TF2 setting. That is, when the control unit 68 changes the tuning frequency TF1 to a higher frequency side in the change of the tuning frequency TF1 setting, the control unit 68 changes the tuning frequency TF2 to a higher frequency side in the change of the tuning frequency TF2 setting. When the control unit 68 changes the tuning frequency TF1 to the lower frequency side in the change of the tuning frequency TF1 setting, the control unit 68 changes the tuning frequency TF2 to the lower frequency side in the change of the tuning frequency TF2 setting. That is, when the control unit 68 changes the tuning frequency TF1 to a lower frequency side in the change of the tuning frequency TF1 setting, the control unit 68 changes the tuning frequency TF2 to a lower frequency side in the change of the tuning frequency TF2 setting. This makes it possible to move the frequency band FB of the evaluation target and the frequency of the problematic interference wave IW in opposite directions when the tuning frequencies TF1 and TF2 are changed to the higher frequency side or when the tuning frequencies TF1 and TF2 are changed to the lower frequency side, thereby increasing the possibility of moving the frequency of the problematic interference wave IW outside the frequency band FB of the evaluation target.

[0109] 2.7 Processing flow 11 and 12 are flowcharts showing the flow of processing performed by the control unit of the receiving device provided in the receiving system of the first embodiment.

[0110] This process is executed only when both the first tuner path and the second tuner path are not paused and are used for tuning, and therefore this process is not executed when one of the first tuner path and the second tuner path is paused and is not used for tuning.

[0111] When a user selects channel CH3 for recording and then selects channel CH1 for viewing, the control unit 68 executes steps S101 to S114 shown in Figures 11 and 12 to prevent the broadcast wave BW23 broadcast on channel CH3 from being subjected to intermodulation interference.

[0112] In step S101, the control unit 68 detects, based on a signal received via the high-speed digital I / F 67, a user's operation on the remote controller 36 to select channel CH3.

[0113] In the following step S102, the control unit 68 sets the tuning frequency TF2 of the second tuner 42 to frequency f3 in accordance with the user's operation to select the detected channel CH3, and causes the second tuner 42 to select the broadcast wave BW23 having the frequency f3.

[0114] At the time when step S102 is executed, the reception state of the broadcast wave BW23 is assumed to be good. This means that the reason why the reception state of the broadcast wave BW23 deteriorates after step S103 is because both tuning frequencies TF1 and TF2 are set and interference waves IW2, IW4, etc. are generated.

[0115] In the next step S103, the control unit 68 detects, based on a signal received via the high-speed digital I / F 67, a user operation performed on the remote controller 36 to select the channel CH1.

[0116] In the following step S104, the control unit 68 judges whether or not the first information is stored in the flash memory 65. The first information indicates the settings of the tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133 when the combination of the channels CH1 and CH3 is selected. If the control unit 68 judges that the first information is stored in the flash memory 65, it executes step S105 and then ends the process. If the control unit 68 judges that the first information is not stored in the flash memory 65, it executes step S106.

[0117] In step S105, the control unit 68 reproduces the settings of the tuning frequencies TF1 and TF2 having the contents indicated by the stored first information. As a result, when the combination of channels CH1 and CH3 is selected again, if there are settings of the tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133, which were searched for when the combination of channels CH1 and CH3 was previously selected, the control unit 68 reproduces the settings of the tuning frequencies TF1 and TF2 having the contents indicated by the first information. As a result, it is possible to omit the control unit 68 from re-searching for the settings of the tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133. As a result, when the channels CH1 and CH3 are selected, the receiving device 12 can quickly and stably achieve a state in which tuning to the broadcast waves BW21 and BW23 is completed.

[0118] In step S106, the control unit 68 determines whether or not the second information is stored in the flash memory 65. The second information indicates that when the combination of channels CH1 and CH3 is selected, there is no setting of tuning frequencies TF1 and TF2 that satisfies the conditions of C / N ratio 132 and BER 133. If the control unit 68 determines that the second information is stored in the flash memory 65, it executes step S107 and then ends the process. If the control unit 68 determines that the second information is not stored in the flash memory 65, it executes step S108.

[0119] FIG. 13 is a diagram showing a screen that the control unit of the receiving device provided in the receiving system of the first embodiment causes to be displayed on the display panel.

[0120] In step S107, the control unit 68 performs a process for notifying that there is no setting of the tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133. As a result, when the combination of the channels CH1 and CH3 is selected again, if there was no setting of the tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133 when the combination of the channels CH1 and CH3 was previously selected, the control unit 68 performs the process. In the first embodiment, the process is a process for displaying a screen 141 shown in FIG. 13 on the display panel 32. The process may be another process. For example, the process may be a process for generating an error report.

[0121] In step S108, control unit 68 sets tuning frequency TF1 of first tuner 41 to frequency f1 in accordance with the user's operation to select channel CH1, and causes first tuner 41 to select broadcast wave BW21 having frequency f1.

[0122] In steps S101, S102, S103 and S108, the control unit 68 sets the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42 in accordance with the channels CH1 and CH3 selected by the user's operation.

[0123] When the frequencies f1 and f3 are a combination that generates an interference wave IW2 having a frequency that falls within the frequency band FB2 of the second tuner 42, intermodulation interference occurs in the second tuner path, the reception state of the broadcast wave BW23 deteriorates, and the C / N ratio 132 and the BER 133 do not satisfy the conditions. When the frequencies f1 and f3 are a combination that does not generate an interference wave IW2 having a frequency that falls within the frequency band FB2 of the second tuner 42, intermodulation interference does not occur in the second tuner path, the reception state of the broadcast wave BW23 is maintained in a good state, and the C / N ratio 132 and the BER 133 are maintained in a state where they satisfy the conditions.

[0124] In the next step S 109 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0125] In the next step S110, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S111. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it executes step S113 and then ends the process.

[0126] In step S111, the control unit 68 starts executing a first loop process, and judges whether or not the C / N ratio 132 and the BER 133 satisfy the conditions during the first loop process. The first loop process is a process for judging whether or not the C / N ratio 132 and the BER 133 satisfy the conditions while moving the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42 to the high frequency side by the step frequency fstep at a time. If the control unit 68 judges that the C / N ratio 132 and the BER 133 do not satisfy the conditions, it executes step S112. If the control unit 68 judges that the C / N ratio 132 and the BER 133 satisfy the conditions, it executes step S113 and then ends the process.

[0127] In step S112, the control unit 68 starts executing the second loop process, and judges whether or not the C / N ratio 132 and the BER 133 satisfy the conditions while executing the second loop process. The second loop process is a process for judging whether or not the C / N ratio 132 and the BER 133 satisfy the conditions while moving the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42 to the lower frequency side by the step frequency fstep at a time. If the control unit 68 judges that the C / N ratio 132 and the BER 133 do not satisfy the conditions, it executes step S114. If the control unit 68 judges that the C / N ratio 132 and the BER 133 satisfy the conditions, it executes step S113 and then ends the process.

[0128] In step S113, the control unit 68 writes first information to the flash memory 65. The written first information constitutes the data 81 stored in the flash memory 65. The control unit 68 executes step S113 when there is a setting of the tuning frequencies TF1 and TF2 that satisfies the conditions of the C / N ratio 132 and the BER 133. The written first information indicates the content of the setting of the tuning frequencies TF1 and TF2 that satisfies the conditions of the C / N ratio 132 and the BER 133 when the combination of the channels CH1 and CH3 is selected.

[0129] After determining that the C / N ratio 132 and the BER 133 satisfy the conditions in step S110, S111, or S112, the control unit 68 does not change the settings of the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42. Therefore, when the control unit 68 determines that the C / N ratio 132 and the BER 133 satisfy the conditions in a state in which the tuning frequencies TF1 and TF2 are set to the frequencies f1 and f3, respectively, the control unit 68 maintains the state. As a result, when the frequency of the interference wave IW2 is not within the frequency band FB2 of the second tuner 42 at the time when the tuning frequencies TF1 and TF2 are set to the frequencies f1 and f3, respectively, the state in which the frequency of the interference wave IW2 is not within the frequency band FB2 of the second tuner 42 is maintained. When the control unit 68 determines that the C / N ratio 132 and the BER 133 satisfy the conditions in a state in which the tuning frequencies TF1 and TF2 are moved to the higher frequency side, the control unit 68 maintains the state. As a result, if the frequency of the interference wave IW2 is not within the frequency band FB2 of the second tuner 42 at the time when the tuning frequencies TF1 and TF2 are moved to the higher frequency side, the state in which the frequency of the interference wave IW2 is not within the frequency band FB2 of the second tuner 42 is maintained. If the control unit 68 determines that the C / N ratio 132 and the BER 133 satisfy the conditions in the state in which the tuning frequencies TF1 and TF2 are moved to the lower frequency side, the control unit 68 maintains the state. As a result, if the frequency of the interference wave IW2 is not within the frequency band FB2 of the second tuner 42 at the time when the tuning frequencies TF1 and TF2 are moved to the lower frequency side, the state in which the frequency of the interference wave IW2 is not within the frequency band FB2 of the second tuner 42 is maintained.

[0130] In step S114, the control unit 68 writes second information to the flash memory 65. The written second information constitutes the data 81 stored in the flash memory 65. The control unit 68 executes step S114 when there are no settings of tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133 even after setting the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42, and performing the first loop process and the second loop process. The written second information indicates that there are no settings of tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133.

[0131] Also, the control unit 68 performs a process for notifying the user that there are no settings of the tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133, similar to step S107.

[0132] FIG. 14 is a flowchart showing the flow of processing performed by the control unit of the receiving device provided in the receiving system of the first modified example of the first embodiment.

[0133] In the first embodiment, as shown in Fig. 12, the control unit 68 executes a first loop process in step S111, and then executes a second loop process in step S112. In contrast, in the first modified example of the first embodiment, as shown in Fig. 14, the control unit 68 executes a second loop process in step S111, and then executes a first loop process in step S112.

[0134] 2.8 First Loop Processing Flow FIG. 15 is a flowchart showing the flow of the first loop process performed by the control unit of the receiving device provided in the receiving system of the first embodiment.

[0135] When executing the above-mentioned first loop process, the control unit 68 executes steps S121 to S129 shown in FIG.

[0136] In step S121, the control unit 68 initializes the number of loops n to zero.

[0137] In the following step S122, the control unit 68 increments the loop count n.

[0138] In the next step S123, the control unit 68 sets the tuning frequency TF1 of the first tuner 41 to the frequency f1+fstep*n. As a result, the control unit 68 moves the tuning frequency TF1 to the higher frequency side. The control unit 68 increases the amount of movement fstep*n of the tuning frequency TF1 as the loop count n increases.

[0139] In the next step S 124 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0140] In the next step S125, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S126. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it ends the first loop process and executes the above-mentioned step S113.

[0141] In step S126, the control unit 68 sets the tuning frequency TF2 of the second tuner 42 to the frequency f3+fstep*n. As a result, the control unit 68 moves the tuning frequency TF2 to the higher frequency side. The control unit 68 increases the amount of movement fstep*n of the tuning frequency TF2 as the loop count n increases.

[0142] In the next step S 127 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0143] In the next step S128, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S129. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it ends the first loop process and executes the above-mentioned step S113.

[0144] In step S129, the control unit 68 judges whether the loop number n has reached the maximum loop number nmax. If the control unit 68 judges that the loop number n has reached the maximum loop number nmax, it ends the first loop process and executes the above-mentioned step S112. If the control unit 68 judges that the loop number n has not reached the maximum loop number nmax, it executes step S122 again to continue the first loop process. The maximum loop number nmax determines the maximum movement amount of the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42. The maximum loop number nmax is set so that the movement amount fstep*n of the tuning frequencies TF1 and TF2 does not exceed the tuning pull-in performance of the first tuner 41 and the second tuner 42. This makes it possible to prevent the first tuner 41 and the second tuner 42 from being unable to maintain the tuning state to the broadcast waves BW21 and BW22, respectively, due to the first loop process. The maximum number of loops nmax decreases as the step frequency fstep increases, and increases as the step frequency fstep decreases.

[0145] According to steps S122 to S129, if the C / N ratio 132 and the BER 133 satisfy the conditions in a state in which the tuning frequency TF1 of the first tuner 41 is shifted to the higher frequency side, the control unit 68 ends the first loop processing. If the C / N ratio 132 and the BER 133 do not satisfy the conditions in this state, the control unit 68 further shifts the tuning frequency TF2 of the second tuner 42 to the higher frequency side.

[0146] Furthermore, if the C / N ratio 132 and the BER 133 satisfy the conditions in a state in which the tuning frequency TF2 of the second tuner 42 has been shifted to the higher frequency side, the control unit 68 ends the first loop process. If the C / N ratio 132 and the BER 133 do not satisfy the conditions in this state, the control unit 68 increases the amount of shift and continues the first loop process.

[0147] In the first embodiment, the amount of movement of the tuning frequency TF1 of the first tuner 41 when it moves to the higher frequency side and the amount of movement of the tuning frequency TF2 of the second tuner 42 when it moves to the higher frequency side are the same, fstep*n. This makes it possible to prevent a large shift in the timing at which the movement of the tuning frequency TF1 to the higher frequency side exceeds the tuning pull-in performance of the first tuner 41 and the timing at which the movement of the tuning frequency TF2 to the higher frequency side exceeds the tuning pull-in performance of the second tuner 42.

[0148] In the first embodiment, the control unit 68 moves the tuning frequency TF1 of the first tuner 41 to the higher frequency side in step S123, and then moves the tuning frequency TF2 of the second tuner 42 to the higher frequency side in step S126. However, the control unit 68 may move the tuning frequency TF1 to the higher frequency side after moving the tuning frequency TF2 to the higher frequency side.

[0149] 2.9 Second Loop Processing Flow FIG. 16 is a flowchart showing the flow of the second loop process performed by the control unit of the receiving device provided in the receiving system of the first embodiment.

[0150] When executing the above-mentioned second loop process, the control unit 68 executes steps S141 to S149 shown in FIG.

[0151] In step S141, the control unit 68 initializes the loop count n to zero.

[0152] In the following step S142, the control unit 68 increments the loop count n.

[0153] In the next step S143, the control unit 68 sets the tuning frequency TF1 of the first tuner 41 to the frequency f1-fstep*n. As a result, the control unit 68 shifts the tuning frequency TF1 to the lower frequency side. The control unit 68 also increases the shift amount fstep*n of the tuning frequency TF1 as the loop count n increases.

[0154] In the next step S 144 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0155] In the next step S145, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S146. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it ends the second loop process and executes the above-mentioned step S113.

[0156] In step S146, the control unit 68 sets the tuning frequency TF2 of the second tuner 42 to the frequency f3-fstep*n. As a result, the control unit 68 shifts the tuning frequency TF2 of the second tuner 42 to the lower frequency side. The control unit 68 increases the shift amount fstep*n of the tuning frequency TF2 of the second tuner 42 as the loop count n increases.

[0157] In the next step S 147 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0158] In the next step S148, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S149. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it ends the second loop process and executes the above-mentioned step S113.

[0159] In step S149, the control unit 68 judges whether the loop number n has reached the maximum loop number nmax. If the control unit 68 judges that the loop number n has reached the maximum loop number nmax, it ends the second loop process and executes the above-mentioned step S114. If the control unit 68 judges that the loop number n has not reached the maximum loop number nmax, it executes step S142 again to continue the second loop process. The maximum loop number nmax determines the maximum movement amount of the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42. The maximum loop number nmax is set so that the movement amount fstep*n of the tuning frequency TF1 and the tuning frequency TF2 does not exceed the tuning pull-in performance of the first tuner 41 and the second tuner 42. This makes it possible to prevent the first tuner 41 and the second tuner 42 from being unable to maintain the tuning state to the broadcast waves BW21 and BW22 due to the second loop process. The maximum number of loops nmax decreases as the step frequency fstep increases, and increases as the step frequency fstep decreases.

[0160] According to steps S142 to S149, if the C / N ratio 132 and the BER 133 satisfy the conditions in a state in which the tuning frequency TF1 of the first tuner 41 is shifted to the lower frequency side, the control unit 68 ends the second loop process. On the other hand, if the C / N ratio 132 and the BER 133 do not satisfy the conditions in that state, the control unit 68 further shifts the tuning frequency TF2 of the second tuner 42 to the lower frequency side.

[0161] Furthermore, if the C / N ratio 132 and the BER 133 satisfy the conditions in a state in which the tuning frequency TF2 of the second tuner 42 has been shifted to the lower frequency side, the control unit 68 ends the second loop process. On the other hand, if the C / N ratio 132 and the BER 133 do not satisfy the conditions in that state, the control unit 68 increases the amount of shift and continues the second loop process.

[0162] In the first embodiment, the amount of movement of the tuning frequency TF1 of the first tuner 41 when it moves to the lower frequency side and the amount of movement of the tuning frequency TF2 of the second tuner 42 when it moves to the lower frequency side are the same, fstep*n. This makes it possible to prevent a large shift in the timing at which the movement of the tuning frequency TF1 to the lower frequency side exceeds the tuning pull-in performance of the first tuner 41 and the timing at which the movement of the tuning frequency TF2 to the lower frequency side exceeds the tuning pull-in performance of the second tuner 42.

[0163] In the first embodiment, the control unit 68 moves the tuning frequency TF1 of the first tuner 41 to the lower frequency side in step S143, and then moves the tuning frequency TF2 of the second tuner 42 to the lower frequency side in step S146. However, the control unit 68 may move the tuning frequency TF1 to the lower frequency side after moving the tuning frequency TF2 to the lower frequency side.

[0164] When the first and second loop processes are executed in the order shown in Fig. 12, if the C / N ratio 132 and BER 133 do not satisfy the conditions when the number of times the tuning frequencies TF1 and TF2 are changed to increase the tuning frequencies TF1 and TF2 reaches the upper limit determined by the maximum loop number nmax, the control unit 68 changes the tuning frequencies TF1 and TF2 to decrease the tuning frequencies TF1 and TF2. On the other hand, when the first and second loop processes are executed in the order shown in Fig. 14, if the C / N ratio 132 and BER 133 do not satisfy the conditions when the number of times the tuning frequencies TF1 and TF2 are changed to increase the tuning frequencies TF1 and TF2 reaches the upper limit determined by the maximum loop number nmax, the control unit 68 changes the tuning frequencies TF1 and TF2 to increase the tuning frequencies TF1 and TF2. In either case, the control unit 68 can search for the tuning frequency TF1 that satisfies the conditions of the C / N ratio 132 and the BER 133 on both the higher and lower frequency sides than the frequency f1, and can search for the tuning frequency TF2 that satisfies the conditions of the C / N ratio 132 and the BER 133 on both the higher and lower frequency sides than the frequency f3. This increases the possibility of finding the settings of the tuning frequencies TF1 and TF2 that satisfy the conditions of the C / N ratio 132 and the BER 133.

[0165] 2.10 Comparison with Reference Examples FIG. 17 is a block diagram of a receiving system according to a reference example.

[0166] A receiving device 12X provided in a receiving system 1X of the reference example shown in FIG. 17 is a general terrestrial digital broadcast receiver having one tuner 40 and one demodulation section 50.

[0167] The receiving device 12 shown in Fig. 7 does not include any additional elements, except for the output processing unit 64 and the output terminal 34 for recording, as compared with the receiving device 12X shown in Fig. 17. That is, the receiving device 12 can suppress the deterioration of the reception quality due to intermodulation interference without adding any special circuit to the receiving device 12. For example, in the receiving device 12, even when the current broadcasting and advanced broadcasting are mixed and the number of channels assigned to the broadcasting increases, or when the current broadcasting and advanced broadcasting are mixed and the types of interference waves increase, the receiving device 12 can suppress the deterioration of the reception quality due to intermodulation interference without adding any special circuit to the receiving device 12. Furthermore, in the receiving device 12, the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42 are moved in steps each time a combination of two channels is selected, and the settings of the tuning frequency TF1 and the tuning frequency TF2 that improve the second reception quality 122 are searched for, thereby eliminating the need to check for the presence or absence of intermodulation interference and to take measures against intermodulation interference in advance for each of the many channel combinations.

[0168] 2.11 Searching for tuning frequency settings when the receiving device is not in use A search for the setting of the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42 that satisfies the conditions for the C / N ratio 132 and the BER 133 may be performed as an internal process of the receiving device 12 during a time period when the receiving device 12 is not being used for viewing or recording. For example, the search may be performed at night.

[0169] When the search is performed during the time period, it is preferable to search for the setting of the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42, which satisfies the conditions of the C / N ratio 132 and the BER 133, for all combinations of two channels included in all channels registered by the channel search process. In this case, the flash memory 65 stores first information indicating the contents of the setting of the tuning frequencies TF1 and TF2, which satisfies the conditions of the C / N ratio 132 and the BER 133, for all combinations of two channels, or second information indicating that there is no setting of the tuning frequencies TF1 and TF2, which satisfies the conditions of the C / N ratio 132 and the BER 133. This makes it unnecessary to search for the setting of the tuning frequencies TF1 and TF2, which satisfies the conditions of the C / N ratio 132 and the BER 133, when a combination of two channels is selected by the user's operation.

[0170] 3. Second embodiment The following describes the differences between the second embodiment and the first embodiment. For points that are not described, the second embodiment employs the same configuration as that employed in the first embodiment.

[0171] 3.1 Receiving device FIG. 18 is a block diagram of a receiving system according to the second embodiment.

[0172] The receiving device 12 shown in Fig. 18 is a receiving device equipped with a triple tuner. Therefore, the receiving device 12 can simultaneously display video corresponding to the first broadcast wave, output audio corresponding to the first broadcast wave, output video / audio signals for recording corresponding to the second broadcast wave to record the broadcast broadcasted by the second broadcast wave in the external recording device 13, and output video / audio signals for recording corresponding to the third broadcast wave to record the broadcast broadcasted by the third broadcast wave in the external recording device 13.

[0173] In the second embodiment, the main system 31 includes a third tuner 43 and a third demodulation unit 53, as shown in FIG.

[0174] The third tuner 43 selects a third frequency component belonging to a third frequency band determined by the tuning frequency TF3 from the RF signal input to the main system 31. This allows the third tuner 43 to select a third radio wave according to the tuning frequency TF3. This allows the third tuner 43 to select the third broadcast wave.

[0175] The third tuner 43 generates a third IF signal from the selected third frequency component.

[0176] The third tuner 43 is a general tuner, and therefore includes a tuning circuit, a local oscillation circuit, a mixing circuit, an amplifier circuit, and the like.

[0177] The third demodulation unit 53 demodulates the generated third IF signal into a third baseband signal.

[0178] The third tuner 43 and the third demodulation unit 53 have a tuning pull-in performance. Therefore, even if the tuning frequency TF3 deviates from the center frequency of the broadcast wave to be received, the third tuner 43 and the third demodulation unit 53 can maintain a stable tuning state to the broadcast wave to be received as long as the deviation of the tuning frequency TF3 from the center frequency of the broadcast wave to be received does not exceed the tuning pull-in performance.

[0179] The descrambling / demultiplexing unit 61 performs descrambling and demultiplexing on the demodulated third baseband signal to generate video / audio signals for recording.

[0180] The third tuner path passing through the third tuner 43 and the third demodulation unit 53 is used for channel selection processing for recording. The tuner paths used for channel selection processing for viewing and channel selection processing for recording are fixed. The tuner paths used for channel selection processing for viewing and channel selection processing for recording may be adaptively changed. In this case, the output destination of the signal generated by performing descrambling processing and demultiplexing processing on the baseband signal is switched between the video processing unit 62 and audio processing unit 63 and the output processing unit 64.

[0181] The third tuner 43 and the third demodulation section 53 are controlled to be inactive during a period in which the second tuner path is not used for channel selection processing.

[0182] The control unit 68 controls the third tuner 43 and the third demodulation unit 53 .

[0183] 3.2 Data handled by the receiving device FIG. 19 is a diagram showing data handled in a receiving device provided in a receiving system of the second embodiment.

[0184] 19, the control unit 68 sets the tuning frequency TF3 of the third tuner 43. When a channel for recording is selected by a user's operation, the control unit 68 sets the tuning frequency TF2 or TF3 to the frequency of the selected channel for recording. This allows the control unit 68 to cause the external recording device 13 to record a broadcast that is broadcast by airwaves using the channel for recording selected by a user's operation.

[0185] The control unit 68 acquires the third synchronization information 103 from the third demodulation unit 53. Based on the acquired third synchronization information 103, the control unit 68 determines whether or not there is a broadcast wave broadcasting on the selected channel for recording.

[0186] The control unit 68 acquires the third broadcast data 113 from the third demodulation unit 53. Based on the acquired third broadcast data 113, the control unit 68 determines whether or not it is possible to select a broadcast wave broadcasting on the selected channel for recording.

[0187] The control unit 68 acquires the third reception quality 123 of the third radio wave selected by the third tuner 43 from the third tuner 43 and the third demodulation unit 53, and monitors the reception state of the third radio wave selected by the third tuner 43.

[0188] 3.3 Reception quality FIG. 9 described above is also a diagram showing the contents of the reception quality handled in the receiving device provided in the receiving system of the second embodiment.

[0189] As shown in FIG. 9, the third reception quality 123 includes at least one selected from the group consisting of a signal strength 131, a C / N ratio 132, a BER 133, an MER 134, a carrier interference monitor 135, a multipath interference monitor 136, and an inter-symbol interference monitor 137.

[0190] 3.4 Changing the tuning frequency setting FIG. 20 is a diagram showing the frequency band of broadcast waves, as well as the tuning frequencies and frequency bands of the first tuner, the second tuner, and the third tuner of a receiving device provided in a receiving system of the second embodiment, and interference waves at (1) the points in time when the tuning frequencies of the first tuner, the second tuner, and the third tuner are set, (2) the points in time when the tuning frequency settings of the first tuner and the second tuner are changed, and (3) the points in time when the tuning frequency setting of the third tuner is changed.

[0191] As shown in Fig. 20, the control unit 68 sets three tuning frequencies TF1, TF2, and TF3. When setting the tuning frequencies TF1, TF2, and TF3, the control unit 68 sets the tuning frequencies TF1, TF2, and TF3 to, for example, frequencies f1, f2, and f3, respectively. In this case, intermodulation distortion occurs between the signal having the frequency f1 emitted by the first tuner 41 and the signal having the frequency f2 emitted by the second tuner 42, generating interference waves IW2, IW4, etc.

[0192] 20, when at least one of the reception qualities included in the first reception quality 121, the second reception quality 122, and the third reception quality 123 (hereinafter referred to as "reception quality to be evaluated") satisfies a condition in the state where the tuning frequencies TF1 and TF2 are set, the control unit 68 maintains the state where the tuning frequencies TF1, TF2, and TF3 are set. When the reception quality to be evaluated does not satisfy a condition in the state where the tuning frequencies TF1, TF2, and TF3 are set, the control unit 68 changes the setting of at least one of the tuning frequencies included in the tuning frequencies TF1, TF2, and TF3 (hereinafter referred to as "tuning frequency to be changed in setting").

[0193] When the setting of the tuning frequency to be changed is changed, at least one of the frequency bands included in the frequency band FB1 of the first tuner 41, the frequency band FB2 of the second tuner 42, and the frequency band FB3 of the third tuner 43 (hereinafter referred to as the "frequency band FB to be evaluated") and the frequency of the interference wave included in the interference waves IW2, IW4, etc. (hereinafter referred to as the "frequency of the problematic interference wave IW") moves. Therefore, even if the frequency of the problematic interference wave IW falls within the frequency band FB to be evaluated at the time when the tuning frequencies TF1, TF2, and TF3 are set, and the reception quality to be evaluated does not satisfy the conditions, it is possible to move the frequency of the problematic interference wave IW outside the frequency band FB to be evaluated by changing the setting of the tuning frequency to be changed and relatively changing the frequency band FB to be evaluated and the frequency of the problematic interference wave IW, so that the reception quality to be evaluated satisfies the conditions. For example, as shown in Fig. 20, even if the frequency of the interference wave IW2 is within the frequency band FB3 of the third tuner 43 when the tuning frequencies TF1, TF2, and TF3 are set to frequencies f1, f2, and f3, respectively, the frequency of the interference wave IW2 can be made to fall outside the frequency band FB3 of the third tuner 43 by setting the tuning frequencies TF1, TF2, and TF3 to frequencies f1+fstep*n, f2-fstep*n, and f3+fstep*k, respectively. The control unit 68 utilizes this to search for tuning frequencies TF1, TF2, and TF3 that can make the frequency of the problematic interference wave IW fall outside the frequency band FB that is the subject of the evaluation.

[0194] In the second embodiment, the frequency band FB to be evaluated is two frequency bands included in the three frequency bands FB1, FB2, and FB3 that the three tuners 41, 42, and 43 have, respectively. Therefore, the reception quality to be evaluated is the reception quality of two radio waves included in the three radio waves selected by the three tuners 41, 42, and 43, respectively. However, the frequency band FB to be evaluated may be one frequency band included in the three frequency bands FB1, FB2, and FB3, or the three frequency bands FB1, FB2, and FB3. Therefore, the reception quality to be evaluated may be the reception quality of one radio wave included in the three radio waves, or the reception quality of the three radio waves.

[0195] In the second embodiment, the reception quality to be evaluated is the C / N ratio 132 and the BER 133 included in the second reception quality 122 and the third reception quality 123. However, the reception quality to be evaluated may be another reception quality.

[0196] In the second embodiment, the condition that the reception quality to be evaluated must satisfy is that the C / N ratio 132 included in the second reception quality 122 and the third reception quality 123 is equal to or greater than the set C / N ratio, and the BER 133 included in the second reception quality 122 and the third reception quality 123 is equal to or less than the set BER. The condition that the reception quality to be evaluated must satisfy may be another condition.

[0197] In the second embodiment, changing the setting of the tuning frequency to be changed includes changing the setting of the tuning frequency TF1 to be the first tuning frequency, and if the reception quality to be evaluated satisfies the condition in the state where the setting of the tuning frequency TF1 is changed, maintaining the state where the setting of the tuning frequency TF1 is changed and the state where the tuning frequencies TF2 and TF3 are set. Also, changing the setting of the tuning frequency to be changed includes changing the setting of the tuning frequency TF1, and if the reception quality to be evaluated does not satisfy the condition in the state where the setting of the tuning frequency TF1 is changed, changing the setting of the tuning frequency TF2 to be the second tuning frequency. However, changing the setting of the tuning frequency to be changed may be something else.

[0198] Also, changing the setting of the tuning frequency to be changed includes changing the setting of the tuning frequencies TF1 and TF2 to be the first tuning frequency, and if the reception quality to be evaluated satisfies the condition in the state where the settings of the tuning frequencies TF1 and TF2 have been changed, maintaining the state in which the settings of the tuning frequencies TF1 and TF2 have been changed and the state in which the tuning frequency TF3 has been set. Also, changing the setting of the tuning frequency to be changed includes changing the setting of the tuning frequencies TF1 and TF2, and if the reception quality to be evaluated does not satisfy the condition in the state where the settings of the tuning frequencies TF1 and TF2 have been changed, further changing the setting of the tuning frequency TF3 to be the second tuning frequency. However, changing the setting of the tuning frequency to be changed may be something else.

[0199] In the second embodiment, changing the setting of the tuning frequency TF1 includes changing the setting of the tuning frequency TF1 to the higher frequency side and changing the setting of the tuning frequency TF1 to the lower frequency side. When changing the setting of the tuning frequency TF1 to the higher frequency side, the control unit 68 sets the tuning frequency TF1 to, for example, a frequency f1+fstep*n. When changing the setting of the tuning frequency TF1 to the lower frequency side, the control unit 68 sets the tuning frequency TF1 to, for example, a frequency f1-fstep*n. Here, n is an integer equal to or greater than 1.

[0200] In the second embodiment, changing the setting of the tuning frequency TF2 includes changing the setting of the tuning frequency TF2 to the higher frequency side and changing the setting of the tuning frequency TF2 to the lower frequency side. When changing the setting of the tuning frequency TF2 to the higher frequency side, the control unit 68 sets the tuning frequency TF2 to, for example, a frequency f2+fstep*n. When changing the setting of the tuning frequency TF2 to the lower frequency side, the control unit 68 sets the tuning frequency TF2 to, for example, a frequency f3-fstep*n. Here, n is an integer equal to or greater than 1.

[0201] In the second embodiment, changing the setting of the tuning frequency TF3 includes changing the setting of the tuning frequency TF3 to the higher frequency side and changing the setting of the tuning frequency TF3 to the lower frequency side. When changing the setting of the tuning frequency TF3 to the higher frequency side, the control unit 68 sets the tuning frequency TF3 to, for example, a frequency f3+fstep*k. When changing the setting of the tuning frequency TF3 to the lower frequency side, the control unit 68 sets the tuning frequency TF3 to, for example, a frequency f3-fstep*k. Here, k is an integer equal to or greater than 1.

[0202] In the second embodiment, when the control unit 68 changes the tuning frequency TF1 to the higher frequency side in the change of the tuning frequency TF1 setting, the control unit 68 changes the tuning frequency TF2 to the lower frequency side in the change of the tuning frequency TF2 setting. When the control unit 68 changes the tuning frequency TF1 to the lower frequency side in the change of the tuning frequency TF1 setting, the control unit 68 changes the tuning frequency TF2 to the higher frequency side in the change of the tuning frequency TF2 setting.

[0203] 3.5 Processing flow 21, 22 and 23 are flowcharts showing the flow of processing performed by the control unit of the receiving device provided in the receiving system of the second embodiment.

[0204] This process is executed exclusively when all of the first tuner path, the second tuner path, and the third tuner path are not paused and are used for channel selection. Therefore, this process is not executed when some of the first tuner path, the second tuner path, and the third tuner path are paused and are not used for channel selection. When one tuner path included in the first tuner path, the second tuner path, and the third tuner path is paused and is not used for channel selection, the process described in the first embodiment is executed.

[0205] When a user selects channel CH3 for recording and then selects channels CH1 and CH2 for viewing and recording, the control unit 68 executes steps S161 to S185 shown in Figures 21, 22, and 23 to prevent the broadcast waves BW22 and BW23 broadcast on channels CH2 and CH3, respectively, from being subjected to intermodulation interference.

[0206] In step S161, the control unit 68 detects, based on a signal received via the high-speed digital I / F 67, a user's operation on the remote controller 36 to select channel CH3.

[0207] In the following step S162, the control unit 68 sets the tuning frequency TF3 of the third tuner 43 to frequency f3 in accordance with the user's operation to select the detected channel CH3, and causes the third tuner 43 to select the broadcast wave BW23 having the frequency f3.

[0208] In the next step S163, the control unit 68 detects, based on a signal received via the high-speed digital I / F 67, a user operation performed on the remote controller 36 to select the channels CH1 and CH2.

[0209] In the following step S164, the control unit 68 judges whether or not the first information is stored in the flash memory 65. The first information indicates the settings of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133 included in the second reception quality 122 and the third reception quality 123 when the combination of channels CH1, CH2, and CH3 is selected. If the control unit 68 judges that the first information is stored in the flash memory 65, it executes step S165 and then ends the process. If the control unit 68 judges that the first information is not stored in the flash memory 65, it executes step S166.

[0210] In step S165, the control unit 68 reproduces the settings of tuning frequencies TF1, TF2, and TF3 having the contents indicated by the stored first information. As a result, when the combination of channels CH1, CH2, and CH3 is selected again, if there are settings of tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of C / N ratio 132 and BER 133, which were searched when the combination of channels CH1, CH2, and CH3 was previously selected, the control unit 68 reproduces the settings of tuning frequencies TF1, TF2, and TF3 having the contents indicated by the first information. As a result, it is possible to omit the control unit 68 from re-searching the settings of tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of C / N ratio 132 and BER 133. As a result, when channels CH1, CH2, and CH3 are selected, the receiving device 12 can quickly and stably achieve a state in which tuning to broadcast waves BW21, BW22, and BW23 is completed.

[0211] In step S166, the control unit 68 determines whether or not the second information is stored in the flash memory 65. The second information indicates that when the combination of channels CH1, CH2, and CH3 is selected, there are no settings of tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of C / N ratio 132 and BER 133. If the control unit 68 determines that the second information is stored in the flash memory 65, it executes step S167 and then ends the process. If the control unit 68 determines that the second information is not stored in the flash memory 65, it executes step S168.

[0212] FIG. 13 is also a diagram showing a screen that the control unit of the receiving device provided in the receiving system of the second embodiment causes to be displayed on the display panel.

[0213] In step S167, the control unit 68 performs a process for notifying that there is no setting of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133. In this way, when the combination of the channels CH1, CH2, and CH3 was previously selected and there was no setting of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133, the control unit 68 performs the process when the combination of the channels CH1, CH2, and CH3 is selected again. In the second embodiment, the process is a process for displaying the screen 141 shown in FIG. 13 on the display panel 32. The process may be another process. For example, the process may be a process for generating an error report.

[0214] In step S168, the control unit 68 initializes the number of loops k for the third loop process to zero.

[0215] In the next step S169, the control unit 68 sets the increment / decrement setting value j to 0. Setting the increment / decrement setting value to 0 means that when the C / N ratio 132 and the BER 133 cannot be made to satisfy the conditions by changing the settings of the tuning frequencies TF1 and TF2, the setting of the tuning frequency TF3 is changed so that the tuning frequency TF3 moves to the higher frequency side. Setting the increment / decrement setting value to 1 means that when the C / N ratio 132 and the BER 133 cannot be made to satisfy the conditions by changing the settings of the tuning frequencies TF1 and TF2, the setting of the tuning frequency TF3 is changed so that the tuning frequency TF3 moves to the lower frequency side.

[0216] In the next step S170, the control unit 68 determines whether the increase / decrease set value j is 0. If the control unit 68 determines that the increase / decrease set value j is 0, the control unit 68 executes step S171 and then step S173. If the control unit 68 determines that the increase / decrease set value j is not 0, the control unit 68 executes step S172 and then step S173.

[0217] In step S171, the control unit 68 sets the tuning frequency TF3 to the frequency f3+fstep*k.

[0218] In step S172, the control unit 68 sets the tuning frequency TF3 to the frequency f3-fstep*k.

[0219] In steps S171 and S172, the control unit 68 shifts the tuning frequency TF3 of the third tuner 43 to the higher frequency side and the lower frequency side, respectively. The control unit 68 increases the shift amount fstep*k of the tuning frequency TF3 as the loop count k increases.

[0220] In step S173, control unit 68 sets tuning frequency TF1 of first tuner 41 to frequency f1 in accordance with the user's operation to select channel CH1, and causes first tuner 41 to select broadcast wave BW21 having frequency f1.

[0221] In the next step S174, the control unit 68 sets the tuning frequency TF2 of the second tuner 42 to frequency f2 in accordance with the user's operation to select channel CH2, and causes the second tuner 42 to tune to the broadcast wave BW22 having frequency f2. If the control unit 68 is requested to cause the first tuner 41 to tune to a channel while the second tuner 42 is tuned to a broadcast wave, the control unit 68 redoes the tuning frequency setting from the tuning frequency TF2 of the second tuner 42. If the control unit 68 is requested to cause the second tuner 42 to tune to a channel while the first tuner 41 is tuned to a broadcast wave, the control unit 68 redoes the tuning frequency setting from the tuning frequency TF1 of the first tuner 41.

[0222] Through steps S161, S162, S163, S171, S172 and S173, the control unit 68 sets the tuning frequency TF1 of the first tuner 41, the tuning frequency TF2 of the second tuner 42 and the tuning frequency TF3 of the third tuner 43 in accordance with the channels CH1, CH2 and CH3 selected by user operation.

[0223] In the next step S 175 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0224] In the next step S176, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S177. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it executes step S179 and then ends the process.

[0225] In step S177, the control unit 68 starts executing a first loop process, and judges whether the C / N ratio 132 and the BER 133 satisfy the conditions while executing the first loop process. The first loop process is a process for judging whether the C / N ratio 132 and the BER 133 satisfy the conditions while moving the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42 to the high frequency side and the low frequency side, respectively, by the step frequency fstep. If the control unit 68 judges that the C / N ratio 132 and the BER 133 do not satisfy the conditions, it executes step S178. If the control unit 68 judges that the C / N ratio 132 and the BER 133 satisfy the conditions, it executes step S179 and then ends the process.

[0226] In step S178, the control unit 68 starts executing the second loop process, and judges whether or not the C / N ratio 132 and the BER 133 satisfy the conditions while executing the second loop process. The second loop process is a process for judging whether or not the C / N ratio 132 and the BER 133 satisfy the conditions while moving the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42 to the lower frequency side and the higher frequency side by the step frequency fstep, respectively. If the control unit 68 judges that the C / N ratio 132 and the BER 133 do not satisfy the conditions, it executes step S180. If the control unit 68 judges that the C / N ratio 132 and the BER 133 satisfy the conditions, it executes step S179 and then ends the process.

[0227] In step S179, the control unit 68 writes first information to the flash memory 65. The written first information constitutes the data 81 stored in the flash memory 65. The control unit 68 executes step S179 when there are settings of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133. The written first information indicates the contents of the settings of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133 when the combination of the channels CH1 and CH3 is selected.

[0228] In step S180, the control unit 68 increments the loop count k.

[0229] In the next step S181, the control unit 68 judges whether the loop number k has reached the maximum loop number kmax. If the control unit 68 judges that the loop number k has reached the maximum loop number kmax, it executes step S182. If the control unit 68 judges that the loop number k has not reached the maximum loop number kmax, it executes step S170 again to continue the third loop process. The maximum loop number kmax determines the maximum movement amount of the tuning frequency TF3 of the third tuner 43. The maximum loop number kmax is set so that the movement amount fstep*k of the tuning frequency TF3 does not exceed the tuning pull-in performance of the third tuner 43. This makes it possible to prevent the third tuner 43 from being unable to maintain tuning to the third broadcast wave BW23 due to the third loop process. The maximum loop number kmax becomes smaller as the step frequency fstep increases, and becomes larger as the step frequency fstep decreases.

[0230] In step S182, the control unit 68 determines whether the increase / decrease set value j is 0. If the control unit 68 determines that the increase / decrease set value j is 0, it sequentially executes steps S183 and S184, and then executes step S170 again to continue the third loop process. If the control unit 68 determines that the increase / decrease set value j is not 0, it executes step S185.

[0231] In step S183, the control unit 68 initializes the loop count k to zero.

[0232] In the following step S184, the control unit 68 sets the increase / decrease set value j to 1.

[0233] In steps S181 to S184, when the control unit 68 cannot find the settings of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133 even if the first and second loop processes are performed while moving the tuning frequency TF3 to the high frequency side in the third loop process, the control unit 68 changes the increase / decrease setting value j, and searches for the settings of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133 by performing the first and second loop processes while moving the tuning frequency TF3 to the low frequency side again in the third loop process. When the control unit 68 still cannot find the settings of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133, the control unit 68 ends the third loop process.

[0234] In step S185, the control unit 68 writes second information to the flash memory 65. The written second information constitutes the data 81 stored in the flash memory 65. The control unit 68 executes step S185 when there are no settings of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133 even after setting the tuning frequency TF1 of the first tuner 41, the tuning frequency TF2 of the second tuner 42, and the tuning frequency TF3 of the third tuner 43, and performing the first loop process, the second loop process, and the third loop process. The written second information indicates that there are no settings of the tuning frequencies TF1, TF2, and TF3 that satisfy the conditions of the C / N ratio 132 and the BER 133.

[0235] 3.6 First Loop Processing Flow FIG. 24 is a flowchart showing the flow of a first loop process performed by the control unit of the receiving device provided in the receiving system of the second embodiment.

[0236] When executing the first loop process described above, the control unit 68 executes steps S201 to S209 shown in FIG.

[0237] In step S201, the control unit 68 initializes the loop count n to zero.

[0238] In the next step S202, the control unit 68 increments the loop count n.

[0239] In the next step S203, the control unit 68 sets the tuning frequency TF1 of the first tuner 41 to the frequency f1+fstep*n. As a result, the control unit 68 moves the tuning frequency TF1 to the higher frequency side. The control unit 68 increases the amount of movement fstep*n of the tuning frequency TF1 as the loop count n increases.

[0240] In the next step S 204 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0241] In the next step S205, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S206. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it ends the first loop process and executes the above-mentioned step S179.

[0242] In step S206, the control unit 68 sets the tuning frequency TF2 of the second tuner 42 to the frequency f3-fstep*n. As a result, the control unit 68 moves the tuning frequency TF2 to the lower frequency side. The control unit 68 increases the amount of movement fstep*n of the tuning frequency TF2 as the number of loops n increases.

[0243] In the next step S 207 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0244] In the next step S208, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S209. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it ends the first loop process and executes the above-mentioned step S179.

[0245] In step S209, the control unit 68 judges whether the loop number n has reached the maximum loop number nmax. If the control unit 68 judges that the loop number n has reached the maximum loop number nmax, it ends the first loop process and executes the above-mentioned step S178. If the control unit 68 judges that the loop number n has not reached the maximum loop number nmax, it executes step S202 again to continue the first loop process. The maximum loop number nmax determines the maximum movement amount of the tuning frequency TF1 of the first tuner 41. The maximum loop number nmax is set so that the movement amount fstep*n of the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42 do not exceed the tuning pull-in performance of the first tuner 41 and the second tuner 42, respectively. This makes it possible to prevent the first tuner 41 and the second tuner 42 from being unable to maintain the tuning state to the broadcast waves BW21 and BW22, respectively, due to the first loop process. The maximum number of loops nmax decreases as the step frequency fstep increases, and increases as the step frequency fstep decreases.

[0246] According to steps S202 to S209, if the C / N ratio 132 and the BER 133 satisfy the conditions in a state in which the tuning frequency TF1 of the first tuner 41 is shifted to the higher frequency side, the control unit 68 ends the first loop process. If the C / N ratio 132 and the BER 133 do not satisfy the conditions in this state, the control unit 68 further shifts the tuning frequency TF2 to the lower frequency side.

[0247] Furthermore, when the C / N ratio 132 and the BER 133 satisfy the conditions in a state where the tuning frequency TF2 is shifted to the lower frequency side, the control unit 68 ends the first loop processing. When the C / N ratio 132 and the BER 133 do not satisfy the conditions in this state, the control unit 68 increases the amount of shift and continues the first loop processing.

[0248] In the second embodiment, the control unit 68 moves the tuning frequency TF1 of the first tuner 41 to the higher frequency side in step S203, and then moves the tuning frequency TF2 of the second tuner 42 to the lower frequency side in step S206. However, the control unit 68 may move the tuning frequency TF1 of the first tuner 41 to the higher frequency side after moving the tuning frequency TF2 of the second tuner 42 to the lower frequency side.

[0249] 3.7 Second Loop Processing Flow FIG. 25 is a flowchart showing the flow of the second loop process performed by the control unit of the receiving device provided in the receiving system of the second embodiment.

[0250] When executing the second loop process described above, the control unit 68 executes steps S221 to S229 shown in FIG.

[0251] In step S221, the control unit 68 initializes the loop count n to zero.

[0252] In the following step S222, the control unit 68 increments the loop count n.

[0253] In the next step S223, the control unit 68 sets the tuning frequency TF1 of the first tuner 41 to the frequency f1-fstep*n. As a result, the control unit 68 shifts the tuning frequency TF1 to the lower frequency side. The control unit 68 also increases the shift amount fstep*n of the tuning frequency TF1 as the loop count n increases.

[0254] In the next step S 224 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0255] In the next step S225, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S226. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it ends the second loop process and executes the above-mentioned step S179.

[0256] In step S226, the control unit 68 sets the tuning frequency TF2 of the second tuner 42 to the frequency f3+fstep*n. As a result, the control unit 68 moves the tuning frequency TF2 to the higher frequency side. The control unit 68 increases the amount of movement fstep*n of the tuning frequency TF2 as the loop count n increases.

[0257] In the next step S 227 , the control unit 68 acquires the C / N ratio 132 and the BER 133 .

[0258] In the next step S228, the control unit 68 judges whether or not the acquired C / N ratio 132 and BER 133 satisfy the conditions. If the control unit 68 judges that the C / N ratio 132 and BER 133 do not satisfy the conditions, it executes step S229. If the control unit 68 judges that the C / N ratio 132 and BER 133 satisfy the conditions, it ends the second loop process and executes the above-mentioned step S179.

[0259] In step S229, the control unit 68 judges whether the loop number n has reached the maximum loop number nmax. If the control unit 68 judges that the loop number n has reached the maximum loop number nmax, it ends the second loop process and executes the above-mentioned step S180. If the control unit 68 judges that the loop number n has not reached the maximum loop number nmax, it executes step S222 again to continue the second loop process. The maximum loop number nmax determines the maximum movement amount of the tuning frequency TF1 of the first tuner 41 and the tuning frequency TF2 of the second tuner 42. The maximum loop number nmax is set so that the movement amount fstep*n of the tuning frequencies TF1 and TF2 does not exceed the tuning pull-in performance of the first tuner 41 and the second tuner 42, respectively. This makes it possible to prevent the first tuner 41 and the second tuner 42 from being unable to maintain the tuning state to the broadcast waves BW21 and BW22 due to the second loop process. The maximum number of loops nmax decreases as the step frequency fstep increases, and increases as the step frequency fstep decreases.

[0260] According to steps S222 to S229, if the C / N ratio 132 and the BER 133 satisfy the conditions in a state in which the tuning frequency TF1 of the first tuner 41 is shifted to the lower frequency side, the control unit 68 ends the second loop processing. If the C / N ratio 132 and the BER 133 do not satisfy the conditions in this state, the control unit 68 further shifts the tuning frequency TF2 of the second tuner 42 to the higher frequency side.

[0261] Furthermore, when the C / N ratio 132 and the BER 133 satisfy the conditions in a state where the tuning frequency TF2 is shifted to the higher frequency side, the control unit 68 ends the second loop processing. When the C / N ratio 132 and the BER 133 do not satisfy the conditions in the corresponding state, the control unit 68 increases the shift amount and continues the second loop processing.

[0262] In the second embodiment, the control unit 68 moves the tuning frequency TF1 of the first tuner 41 to the lower frequency side in step S223, and then moves the tuning frequency TF2 of the second tuner 42 to the higher frequency side in step S226. However, the control unit 68 may move the tuning frequency TF1 of the first tuner 41 to the lower frequency side after moving the tuning frequency TF2 of the second tuner 42 to the higher frequency side.

[0263] The present disclosure is not limited to the above-described embodiments, and may be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiments, a configuration that has the same action and effect, or a configuration that can achieve the same purpose. [Explanation of symbols]

[0264] 1 Receiving system, 1X receiving system, 11 Antenna device, 12 Receiving device, 12X receiving device, 13 External recording device, 21 Antenna, 22 Booster, 31 Main system, 32 Display panel, 33 Speaker, 34 Output terminal, 35 Transmitting / receiving module, 36 Remote controller, 40 Tuner, 41 First tuner, 42 Second tuner, 43 Third tuner, 50 Demodulation unit, 51 First demodulation unit, 52 Second demodulation unit, 53 Third demodulation unit, 61 Descrambling / demultiplexing unit, 62 Video processing unit, 63 Audio processing unit, 64 Output processing unit, 65 Flash memory, 66 Storage unit, 67 High-speed digital interface (high-speed digital I / F), 68 Control unit, 71 Tuner module, 91 Control program, 101 First synchronization information, 102 Second synchronization information, 103 Third synchronization information, 111 First broadcast data, 112 Second broadcast data, 113 Third broadcast data, 121 First reception quality, 122 Second reception quality, 123 Third reception quality, 131 Signal strength, 132 Carrier-to-noise ratio (C / N ratio), 133 Bit error rate (BER), 134 Modulation error ratio (MER), 135 Carrier interference monitor, 136 Multipath interference monitor, 137 Intersymbol interference monitor, 141 Screen, BW1, BW2, BW10, BW12, BW21, BW22, BW23 Broadcast wave, BW11 Current broadcast broadcast wave, BW13 Advanced broadcast broadcast wave, IW Problematic interference wave, IW1, IW2, IW3, IW4, IWA, IWB, IWB', IWC Interference wave, FB The frequency bands to be evaluated are the FB1, FB2, and FB3 frequency bands.

Claims

1. A plurality of tuners each selecting a plurality of radio waves corresponding to a plurality of tuning frequencies; a control unit that sets the plurality of tuning frequencies, and when a reception quality of at least one radio wave included in the plurality of radio waves does not satisfy a condition in a state in which the plurality of tuning frequencies is set, changes the setting of at least one tuning frequency included in the plurality of tuning frequencies; A receiving device comprising:

2. The control unit maintains the state in which the plurality of tuning frequencies are set when the reception quality satisfies the condition in the state in which the plurality of tuning frequencies are set.

2. The receiving device according to claim 1.

3. Changing the setting of at least one tuning frequency includes changing the setting of a first tuning frequency included in the plurality of tuning frequencies, and, when the reception quality does not satisfy the condition in a state in which the setting of the first tuning frequency has been changed, changing the setting of a second tuning frequency included in the plurality of tuning frequencies.

3. A receiving device according to claim 1 or 2.

4. Changing the setting of at least one tuning frequency includes maintaining the state in which the setting of the first tuning frequency is changed and the state in which the setting of the second tuning frequency is changed when the reception quality satisfies the condition in a state in which the setting of the first tuning frequency is changed.

4. The receiving device according to claim 3.

5. When the control unit increases the first tuning frequency in changing the setting of the first tuning frequency, the control unit increases the second tuning frequency in changing the setting of the second tuning frequency, and when the control unit decreases the first tuning frequency in changing the setting of the first tuning frequency, the control unit decreases the second tuning frequency in changing the setting of the second tuning frequency.

4. The receiving device according to claim 3.

6. The amount of change of the second tuning frequency when the setting of the second tuning frequency is changed is the same as the amount of change of the first tuning frequency when the setting of the first tuning frequency is changed.

6. The receiving device according to claim 5.

7. When the number of times that the setting of the at least one tuning frequency has been changed so that the at least one tuning frequency is increased reaches an upper limit number, and the reception quality does not satisfy the condition, the control unit changes the setting of the at least one tuning frequency so that the at least one tuning frequency is decreased.

3. A receiving device according to claim 1 or 2.

8. When the number of times that the setting of the at least one tuning frequency has been changed so that the at least one tuning frequency is lowered reaches an upper limit number, and the reception quality does not satisfy the condition, the control unit changes the setting of the at least one tuning frequency so that the at least one tuning frequency is higher.

3. A receiving device according to claim 1 or 2.

9. the plurality of tuning frequencies are two tuning frequencies, The plurality of radio waves are two radio waves, the plurality of tuners is two tuners, The at least one radio wave is a single radio wave.

3. A receiving device according to claim 1 or 2.

10. the plurality of tuning frequencies is three tuning frequencies; The plurality of radio waves are three radio waves, the plurality of tuners is three tuners, The at least one radio wave is two radio waves.

3. A receiving device according to claim 1 or 2.

11. A memory unit is provided, The control unit sets the plurality of tuning frequencies according to the plurality of selected channels, and when there are the plurality of tuning frequency settings whose reception quality satisfies the condition, causes the storage unit to store information indicating the contents of the plurality of tuning frequency settings whose reception quality satisfies the condition, and when the plurality of channels are selected again, reproduces the plurality of tuning frequency settings having the contents.

3. A receiving device according to claim 1 or 2.

12. A memory unit is provided, The control unit sets the plurality of tuning frequencies according to the plurality of selected channels, and when there is no setting of the plurality of tuning frequencies whose reception quality satisfies the condition, causes the storage unit to store information indicating that there is no setting of the plurality of tuning frequencies whose reception quality satisfies the condition, and when the plurality of channels are selected again, performs processing for notifying that there is no setting of the plurality of tuning frequencies whose reception quality satisfies the condition.

3. A receiving device according to claim 1 or 2.

13. The reception quality includes at least one selected from the group consisting of signal strength, carrier-to-noise ratio, bit error rate, modulation error ratio, carrier interference monitor, multipath interference monitor, and intersymbol interference monitor.

3. A receiving device according to claim 1 or 2.

14. selecting a plurality of radio waves corresponding to a plurality of tuning frequencies, respectively; setting the plurality of tuning frequencies, and when a reception quality of at least one radio wave included in the plurality of radio waves does not satisfy a condition in a state in which the plurality of tuning frequencies have been set, changing the setting of at least one tuning frequency included in the plurality of tuning frequencies; A receiving method comprising:

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