JP2007143018A - Digital data receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcast receiving apparatus capable of improving the application efficiency of a signal from an antenna having high receiving sensitivity by a simple constitution without completely switching a signal from the antenna to use the signal. <P>SOLUTION: The digital data receiver (100) comprises: a first attenuator (10) for attenuating a received signal from a first antenna; a second attenuator (20) for attenuating a received signal from a second antenna; a synthesis part (30) for mutually synthesizing a first signal outputted from the first attenuator (10) and a second signal outputted from the second attenuator (20); and a control part (90) for controlling the attenuation rate of the first attenuator (10) or the second attenuator (20). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a digital data receiver such as a digital broadcast receiver that uses received signals from a plurality of antennas.

  There is known an analog broadcast receiving apparatus that periodically switches a plurality of antennas and uses an antenna having the highest reception level for reception. In analog broadcasting, since a break between image frames can be found by a vertical synchronization signal, the antenna is switched during a period for vertical feedback so that the image frame is not disturbed. However, in digital broadcasting, it is difficult to find the timing of each frame before demodulation because the received data is OFDM demodulated and reconstructed, etc., and the technique used in analog broadcasting is diverted to digital broadcasting. Was difficult.

  There is also known a digital broadcast receiving apparatus that has two combinations of a tuner unit and a demodulation unit, synthesizes signals from the two systems by a diversity combining unit, and outputs the combined signals to one display unit (for example, Patent Document 1). ).

  In addition, there are two combinations of tuner and demodulator, and a double tuner reception mode that individually outputs signals from the two systems and a diversity reception mode that combines and outputs the signals from the two systems are received. There is known a digital broadcast receiving apparatus that switches in accordance with (for example, Patent Document 2).

  Furthermore, there is known a digital broadcast receiving apparatus that has two combinations of a tuner unit and a demodulation unit, and that allows a user to watch a program on one system and record on a recording medium using the other system (patent) Reference 3).

Japanese Patent Laying-Open No. 2005-117226 (FIG. 1) Japanese Patent Laying-Open No. 2004-343210 (FIG. 1) JP 2003-125302 A (page 3)

  However, the conventional example has a plurality of tuner units and demodulating units, so that there are problems such as an increase in the overall configuration of the receiver, an increase in cost, and difficulty in downsizing the apparatus.

  Therefore, the present invention provides a digital broadcast receiver capable of improving the efficiency of use of a signal from an antenna having a high reception sensitivity with a simple configuration, instead of completely switching and using the signal from the antenna. For the purpose.

  A digital data receiver according to the present invention includes a first attenuator for attenuating a received signal from a first antenna, a second attenuator for attenuating a received signal from a second antenna, A combining unit that combines the first signal output from the attenuator and the second signal output from the second attenuator, and a control unit for controlling the attenuation rate of the first attenuator or the attenuation rate of the second attenuator It is characterized by having.

  In the digital data receiver according to the present invention, the digital data receiver further includes a detection unit that detects the signal level of the signal output from the synthesis unit, and the control unit determines the attenuation rate of the first attenuator based on the detection result of the detection unit. Alternatively, it is preferable to control the attenuation rate of the second attenuator. The attenuation rate can be controlled based on the signal level.

  Further, the digital data receiver according to the present invention further includes a demodulator that demodulates the signal output from the synthesizer and detects the signal state, and the controller is configured to detect the signal state based on the detection result of the signal state in the demodulator. It is preferable to control the attenuation rate of the first attenuator and the second attenuator, and detection of the signal state in the demodulator is preferably performed based on BER or CNR. The attenuation rate can be controlled based on BER or CNR.

  Furthermore, in the digital data receiver according to the present invention, the control unit preferably changes the attenuation rate of the first attenuator and the attenuation rate of the second attenuator based on a predetermined time constant or a predetermined control amount. The time constant or the control amount is preferably set according to the signal level of the signal output from the combining unit, the traveling speed of the vehicle on which the digital data receiver is mounted, or the broadcast parameter.

  Furthermore, in the digital data receiver according to the present invention, the control unit includes the attenuation rate of the first attenuator and the attenuation rate of the second attenuator so that the combined ratio of the first signal and the second signal is 100%. It is preferable to control the rate.

  Furthermore, in the digital data receiver according to the present invention, the control unit adds the attenuation factor of the first attenuator and the second attenuator so that the combined ratio of the first signal and the second signal is greater than 100%. It is preferable to control the attenuation rate.

  Furthermore, the digital data receiver according to the present invention further includes a setting unit for setting a combining ratio of the first signal and the second signal, and the control unit has a combining ratio set in the setting unit in the initial state. Thus, it is preferable to control the attenuation rate of the first attenuator and the second attenuator, and the synthesis rate set in the setting unit is a synthesis rate in the end state of the digital data receiver or a synthesis rate determined from the history information. Preferably there is.

  The digital data receiver according to the present invention combines an attenuator for attenuating at least one of the received signals from a plurality of antennas, a signal output from the attenuator and a received signal from another antenna. It has a combining unit and a control unit for controlling the attenuation rate of the attenuator.

  According to the digital data receiver according to the present invention, it is possible to increase the utilization efficiency of a signal before demodulation from an antenna with good reception sensitivity, and thus it is possible to reduce the cost and / or size of the apparatus.

  Further, according to the digital data receiver of the present invention, it is possible to control to change the attenuation rate according to the reception situation by using a level signal or the like, so that the best received signal can always be obtained. It became.

  A digital data (broadcast) receiver according to the present invention will be described below with reference to the drawings.

  The digital data receiver according to the present invention is a receiver compatible with Japanese terrestrial digital television broadcasting. In digital terrestrial television broadcasting, the bandwidth for one channel is divided into 13 segments, 12 of which are used for fixed services (for home use), and the remaining 1 segment is used for mobile services (mobile receiver terminals). Assigned for use. The fixed service employs the MPEG2 system as a data compression system, and the mobile service employs the H.264 data compression system. The H.264 system (one of the video compression systems also known as MPEG-4 Part 10) (or the MPEG4 system) is employed. Encoded digital data for fixed services is encoded by the MPEG2 system and is high quality, but the bit rate is high, so noise resistance is weak, and good when the distance from the broadcast station is long. Reception may be difficult. On the other hand, encoded digital data for mobile services is H.264. H.264 format (or MPEG4 format) encoded with a lower bit rate than the MPEG2 format, so it has high noise resistance and can be received well even when the distance from the broadcasting station is longer. It becomes possible.

  FIG. 1 is a block diagram showing an outline of a digital data receiver 100 according to the present invention.

  Hereinafter, the case where the digital data receiver 100 according to the present invention is mounted on a vehicle will be described. However, the digital data receiver 100 according to the present invention is not limited to being used in a vehicle, but may be used for other purposes. For example, the present invention can also be applied to residential and other moving means. In this case, the vehicle speed detection unit 130 and the navigation device 150 described later may not necessarily be necessary.

  The digital data receiver 100 includes a first attenuator 10, a second attenuator 20, a synthesis unit 30, an RF (Radio Frequency) / IF (Intermediate Frequency) processing unit 31, a signal level detection unit 32, and an FFT (Fast Fourier Transform). Unit 33, OFDM (Orthogonal Frequency Division Multiplexing) demodulator 40, demultiplexer 41, decoder 50, hard disk device (HDD) 60, audio switching processor 70, D / A converter 71, video switching processor 80, scaling A processing unit 81, a drawing processing unit 82, a GDC (graphic) drawing processing unit 83, a control unit 90, a storage unit 91, an I / O 92, a system bus 93, and the like are included.

  The digital data receiver 100 includes a first antenna 110, a second antenna 120, a vehicle speed detector 130 for detecting the speed of the vehicle on which the digital data receiver 100 is mounted, a navigation device 150, an in-vehicle speaker 170, an in-vehicle speaker 170, The display unit 180 and the remote controller 190 were connected. The digital data receiver 100 may include any one or more of the antennas 110 and 120, the vehicle speed detection unit 130, the navigation device 150, the in-vehicle speaker 170, the in-vehicle display unit 180, and the remote controller 190 described above. It may be configured to be included in one or more. In addition, as the 1st antenna 110 and the 2nd antenna 120, all types, for example, the film-type antenna used for a vehicle, can be utilized.

  The digital data receiver 100 is configured to be controlled by operation inputs from various input devices (buttons, touch panel, etc.) provided in the in-vehicle display unit 180 and / or the remote controller 190.

  The decoder unit 50 includes a first audio decoder 51 that decodes audio data for fixed services, a second audio decoder 52 that decodes audio data for mobile services, a first video decoder 53 that decodes video data for fixed services, A second video decoder 54 for decoding video data for mobile service and a data decoder 55 for decoding digital broadcast data are provided. Each of the decoders 51 to 55 may be configured as an individual electronic circuit having each function, or may be a single decoder device in terms of hardware that achieves each function in software. .

Signals received by the first and second antennas 110 and 120 attached to different positions of the vehicle body are respectively synthesized by the synthesis unit 30 via the first attenuator 10 and the second attenuator 20, and then RF / The data is input to the IF processing unit 31. The RF / IF processing unit 31 extracts only the signal related to the selected channel and inputs it to the level detection unit 32 and the FFT unit 33. The signal Fourier-transformed by the FFT unit 33 is input to the OFDM demodulator 40.
The signal level detection unit 32 incorporates an AGC (Auto Gain Control) circuit and outputs a level signal indicating a reception signal level for feedback control of the RF / IF processing unit 31 so that the reception signal becomes a desired reception level. And transmitted to the control unit 90 via the system bus 93. That is, the control unit 90 can know the reception status from the level signal.

  The OFDM demodulator 40 performs synchronization processing, detection processing, error correction processing, and the like, and outputs a TS (Transport Stream) packet signal. Also, a correction error signal (for example, a Reed-Solomon signal) indicating that error correction could not be performed by error correction processing is transmitted from the OFDM demodulator 40 to the controller 90 via the system bus 93. Further, the OFDM demodulator 40 uses a CRC (Cyclic Redundancy Check) code included in the header portion of the TS packet to detect a bit error in transmission, and the bit error exceeds a predetermined threshold. In this case, a BER (Bit Error Ratio) signal is transmitted to the control unit 90 via the system bus 93. Further, the OFDM demodulator 40 transmits a CNR (Carrier to Noise Ratio) signal to the controller 90 via the system bus 93. That is, the control unit 90 can determine that the reception status is bad when the correction error signal, the BER signal, and the CNR signal received from the OFDM demodulation unit 40 are received.

  The demultiplexing unit 41 demultiplexes the TS packet signal from the OFDM demodulating unit 40, sends TS packets related to voice for fixed services to the first voice decoder 51, and TS packets related to voice for portable services to the second voice decoder 52. TS packets related to video for fixed services are sent to the first video decoder 53, TS packets related to video for mobile services are sent to the second video decoder 54, and TS packets related to digital data for data broadcasting are sent to the data decoder 55, respectively. To do.

  The first audio decoder 51 decodes the data included in the TS packet received from the demultiplexing unit 41 to generate audio data for fixed service (MPEG2 system). Data included in the received TS packet is decoded to generate audio data for mobile service (H.264 system or MPEG4 system).

  The first video decoder 53 decodes data included in the TS packet received from the demultiplexing unit 41 to generate video data for a fixed service (MPEG2 system). The second video decoder 53 includes the demultiplexing unit 41. The data included in the TS packet received from is decoded to generate video data for the mobile service (H.264 system or MPEG4 system).

  The data decoder 55 decodes the data included in the TS packet received from the demultiplexing unit 41 to generate EPG (program guide information) data and the like, and outputs the generated data to the control unit 90 via the system bus 93. Configured to do. That is, the control unit 90 can determine the type of broadcast program being received based on EPG data or the like.

  The audio data from the first audio decoder 51 and the second audio decoder is transmitted to the audio switching processing unit 70 via the hard disk drive (HDD) 60, and the video from the first video decoder 53 and the second video decoder is transmitted. The data is transmitted to the voice switching processing unit 70 via the HDD 60.

  In the voice switching processing unit 70, switching control is performed so that either one for a fixed service or one for a portable service is output in accordance with a control signal from the control unit 90, and is mounted on the vehicle via the D / A converter 71. It was configured to output from the speaker 170. The voice switching processing unit 70 receives an analog TV broadcast voice signal received by the analog tuner unit 30 and replaces the voice data for the fixed service and the portable service according to the control signal from the control unit 90. It was configured to be able to output.

  In the video switching processing unit 80, switching control is performed so that either one for the fixed service or the portable service is output in accordance with the control signal from the control unit 90, and the video switching processing unit 80 outputs the signal to the scaling processing unit 81. Configured. The video switching processing unit 80 receives the analog TV broadcast video signal received by the analog tuner unit 30 and replaces the audio data for the fixed service and the portable service according to the control signal from the control unit 90. It was configured to be able to output.

  In the scaling processing unit 81, the image size for the selected fixed service (SD: 720 × 480 pixels, HD: 1920 × 1080 pixels or 720P: 1280 × 720 pixels) or the image size for mobile services (QCIF: 176 × 144) Pixels, QVGA: 320 × 240 pixels or 16: 9 size: 320 × 180 pixels) are configured to be resized to fit the screen size (800 × 640 pixels) of the in-vehicle display unit 180. Note that the above-described screen size of the in-vehicle display unit 50 is an example, and displays having other image sizes can be used.

  The GDC rendering processing unit 83 is configured to generate an image or video by performing bitmap development or the like based on the graphic data for data broadcasting received from the data decoder 55.

  The drawing processing unit 82 is configured to generate display data by combining the video data received from the scaling processing unit 81 and the image or video received from the GDC drawing processing unit 83, and display the data on the in-vehicle display unit 180. In addition, the drawing processing unit 82 performs a calculation process including a storage unit such as a VRAM for temporarily storing video data, an interpolation process, a replacement process, and the like for generating still image data (freeze image data) from the video data. It is preferable to have an arithmetic processing unit to perform.

  The control unit 90 includes a CPU, a RAM, a ROM, and the like, operates according to a program installed in advance, and controls each element connected to the system bus 93. The control unit 90 also receives the level signal from the level detection unit 32, the correction error signal from the OFDM demodulation unit 40, the BER signal and the CNR signal, the vehicle speed signal from the vehicle speed detection unit 130, and the program type information from the data decoder 55. Receiving and determining an optimal first attenuation factor for the first attenuator and a second attenuation factor for the second attenuator based on all or part of each signal, and according to the first attenuation factor and the second attenuation factor, Control for the first attenuator and the second attenuator. Further, the control unit 90 selects an optimal service from among a fixed service (for home use) and a mobile service (mobile reception terminal), and the video and audio related to the service are displayed on the display unit 180 and the in-vehicle speaker. The output is controlled from 170.

  FIG. 2 is a diagram showing an example of a control flow for determining the attenuation rate in the digital data receiver according to the present invention.

  The control flow shown in FIG. 2 is mainly executed by the control unit 90 of the digital data receiver 100 in cooperation with each element of the digital data receiver 100 in accordance with a program installed in advance. The digital data receiver 100 is assumed to be in a state where the power is turned on and various functions can operate.

  Furthermore, it is assumed that the first attenuation factor of the first attenuator and the second attenuation factor of the second attenuator are both set to 50%, for example. That is, 50% of the received signal from the first antenna 110 and 50% of the received signal from the second antenna 120 are combined.

  First, the control unit 90 acquires a level signal from the level detection unit 32 (S201), and determines whether or not it is equal to or less than a predetermined threshold (S202).

  If the level signal is larger than the threshold value, it is determined that the reception state is good, the attenuation rate is maintained as it is, and steps S201 and S202 are periodically repeated.

  When it is determined in S202 that the level signal is equal to or less than the threshold (the reception state is bad), the control unit 90 acquires time constant data and control amount data described later from the storage unit 91 (S203), and the acquired time constant data and The first attenuation rate is increased and the second attenuation rate is decreased according to the control amount data (S204). That is, first, the attenuation rate is controlled so as to increase the signal from the second antenna.

  Next, the control unit 90 acquires the level signal from the level detection unit 32 again (S205), and determines whether or not the level signal acquired in S201 is improved (S206).

  If it is determined in S206 that the level signal has been improved, the control for increasing the signal from the second antenna is correct. Therefore, returning to S202, it is determined whether or not the level signal acquired in S205 is equal to or less than the threshold value. If the level signal is still equal to or less than the threshold value, the attenuation rate is controlled so that the signal from the second antenna is further increased ( S204). The following steps are repeated thereafter.

  If it is determined in S206 that the level signal is not improved, the control for increasing the signal from the second antenna is not correct, and conversely, the control for increasing the signal from the first antenna is performed. . That is, time constant data and control amount data, which will be described later, are acquired from the storage unit 91 (S207), and the first attenuation rate is decreased and the second attenuation rate is increased according to the acquired time constant data and control amount data. (S208). That is, the attenuation rate is controlled so that the signal from the first antenna is increased.

  Next, the control unit 90 acquires a level signal from the level detection unit 32 again (S209), and determines whether or not the level signal is improved from the previously acquired level signal (S210).

  If it is determined in S210 that the level signal has been improved, the control for increasing the signal from the first antenna is correct. Therefore, returning to S211, it is determined whether or not the level signal acquired in S209 is equal to or less than the threshold value. If the level signal is still equal to or less than the threshold value, the attenuation rate is controlled so as to further increase the signal from the first antenna ( S207). The following steps are repeated thereafter.

  If it is determined in S210 that the level signal is not improved, the control for increasing the signal from the first antenna is not correct, and conversely, the signal from the second antenna is increased so that S203 is increased. Perform steps ~ 206.

  In S211, when the level signal acquired in S209 is larger than the threshold value, it is determined that the reception state is good, the attenuation rate is maintained as it is, and the steps of S201 and S202 are periodically repeated.

  In the example of FIG. 2, the attenuation rate is controlled according to the level signal from the level detection unit 32, but the attenuation rate is based on the correction error signal, BER signal, and CNR signal output from the OFDM demodulation unit 40. May be controlled. As described above, in the digital data receiver according to the present invention, it is preferable that the control unit controls the attenuation rate according to the signal indicating the reception status including the level signal, the correction error signal, the BER signal, the CNR signal, and the like.

  It is also possible to control the attenuation rate so as to change according to the area in which the vehicle is moving, not the reception status. Depending on the location of the broadcasting station, etc., and the geographical situation, the optimum signal can be obtained by using any attenuation factor depending on the current position of the vehicle equipped with the digital data receiver according to the present invention and the traveling direction of the vehicle. It is possible to predict in advance whether or not reception is possible. Therefore, the control unit 90 creates a database in which the attenuation rate corresponds to the map information and stores the database in the storage unit 91 or the like, and based on the vehicle position information from the navigation device 150 and the information indicating the traveling direction of the vehicle. , Control can be performed to determine the attenuation rate.

  Further, as shown in FIG. 2, the attenuation rate is determined based on the level signal, the determined attenuation rate is stored in association with the map information, and recorded again in the past when the vehicle passes through the same area again. It is also possible to control so that the attenuation rate is utilized.

  FIG. 3 shows an example of switching of the attenuation rate.

  FIG. 3 shows the first attenuation factor 301 of the first attenuator 10 and the second attenuation factor 302 of the second attenuator 20 as an example of dynamically switching the attenuation factor. Time t1 indicates an initial state of the digital data receiver (when the power is turned on). In the initial state, the first attenuation rate is set to 50% and the second attenuation rate is set to 50%. That is, in this case, the attenuation rate is set to 21 steps every 5%. Further, the sum of the first attenuation rate and the second attenuation rate is always set to 100%.

  Further, the time constant p1 (for example, 100 ms) and the control amount s1 (for example, 5%) are set at the time t1 to t2, and the time constant p2 (for example, 50 ms) and the control amount s2 (10%) at the time t2 to t3. Is set to That is, in this case, the attenuation rate is set to 11 steps every 10%. Further, the sum of the first attenuation rate and the second attenuation rate is always set to 100%.

  As shown in FIG. 3, the time constants p1 and p2 are data relating to the period for switching the attenuation rate. If the time constant is set to be long, the antenna switching is performed slowly (for example, times t2 to t3). On the contrary, if the time constant is set short, the antenna is switched quickly (for example, time t3 to t2).

  Also, as shown in FIG. 3, the control amounts s1 and s2 are data relating to the step width for switching the attenuation rate, and if the control amount is set to a small value, the antenna is switched slowly (for example, time t2 to t3). ). On the contrary, if the control amount is set large, fast antenna switching is performed (for example, time t3 to t2).

  Further, in the example of FIG. 3, the time constant and / or the control amount are set to be changed in two stages according to the strength of the level signal. That is, when the intensity of the level signal is high, the time constant is changed and the control amount is shortened (see t2 to t3). This is because when the intensity of the level signal is high, the reception state may change greatly thereafter, so that the change can be dealt with quickly. When the intensity of the level signal is small, the time constant is changed to be long and the control amount is small (t1 to t2). The change of the time constant and the control amount is executed when the control unit 90 selects data stored in advance in the storage unit 91 based on the level signal from the level detection unit 32. In the case of FIG. 3, at time t <b> 2, the control unit 90 changes the time constant and the control amount based on the signal from the level detection unit 32.

  Further, the time constant and / or the control amount may be fixed, or the user may be able to set the time constant and the control amount independently using the remote controller 190 or the like, or according to other signals. It may be set to change dynamically.

  Further, the time constant and / or the control amount may be dynamically changed according to the vehicle speed of the vehicle on which the digital data receiver 100 is mounted. For example, when the vehicle speed is high, the time constant is shortened and / or the control amount is increased. This is because when the moving speed is high, the reception state may change greatly thereafter, so that the change can be dealt with quickly. When the vehicle speed is low, the time constant is increased and / or the control amount is decreased. The control unit 90 changes the time constant and / or the control amount based on the vehicle speed signal from the vehicle speed detection unit 130.

  Further, the time constant and / or the control amount may be dynamically changed depending on whether the service is a fixed service or a mobile service currently being viewed. For example, when viewing a fixed service, the time constant is changed and / or the control amount is increased. This is because the fixed service has a high quality but has a low bitrate due to a high bit rate, and the reception state may change greatly, so that it can quickly respond to the change. When viewing the mobile service, the time constant is changed to be long and / or the control amount is reduced. This is because the mobile service has a high noise resistance, and thus the reception state is unlikely to change significantly compared to the fixed service. The change of the time constant and / or the control amount is performed by the control unit 90 that performs switching control between fixed and mobile services.

  Further, the time constant and / or the control amount may be dynamically changed according to broadcast parameters such as an error correction coding rate and a modulation method. One of 1/2, 2/3, 3/4, 5/6, and 7/8 is used as the error correction coding rate. Depending on which one is used, a time constant is used. And / or the control amount can be changed. As a modulation method, any one of QPSK, 16QAM, 64QAM, MR-16QAM, and MR-64QAM can be selected for each carrier. Depending on which one is used, the time constant and The control amount can be changed. The change of the time constant and / or the control amount is performed in the control unit 90 that receives the broadcast parameter output from the OFDM demodulator 40.

  The time constant and the control amount shown in FIG. 3 are examples, and it goes without saying that optimum values can be used according to the situation.

  Further, in the example shown in FIG. 3, control is performed so that the sum of the first attenuation rate 301 and the second attenuation rate 302 is 100%, but it is not always necessary to control to be always 100%. For example, the control unit 90 always fixes the attenuation rate of the first attenuator 10 to 100%, and controls the attenuation rate of the second attenuator 20 between 0% and 100% to obtain an optimal received signal. May be. In such a case, since the first attenuator 10 is not necessary, one attenuator is not necessarily required for every antenna. Furthermore, the control unit 90 can control the first and second attenuation factors completely separately so as to obtain an optimal received signal.

  Further, in the example shown in FIG. 3, in the initial state of the digital data receiver 100 (when the power is turned on), both the first attenuation factor and the second attenuation factor are set to 50%. A predetermined value need not be fixed to 91. For example, the first attenuation factor and the second attenuation factor at the time when the power of the latest digital data receiver is turned off are stored in the storage unit 91, and these are set as initial state values. Also good. Also, statistics of the values of the first attenuation factor and the second attenuation factor that have been used so far are obtained from the history information of the digital data receiver, and the value that has been used for the longest time is set as the initial value. May be.

  In the above embodiment, an example using reception signals from two antennas has been described. However, if there are two or more, the present invention can be applied even if there are more reception paths. It is. For example, the present invention can be applied to a digital data receiver having four attenuators connected to four antennas.

  As described above, in the present invention, by gradually switching the reception signals before demodulation from a plurality of antennas, even in a digital data receiver, the signal from the optimum antenna can be obtained without impairing the continuity of the signals. The signal can be used effectively. Therefore, a simple configuration can be employed without requiring a plurality of tuner units and demodulation units.

It is a block diagram which shows the outline | summary of the digital data receiver which concerns on this invention. It is a figure which shows an example of a control flow. It is a figure which shows an example of switching of an attenuation factor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st attenuator 20 2nd attenuator 30 Synthesis | combination part 40 OFDM demodulation part 90 Control part 91 Memory | storage part 110 1st antenna 120 2nd antenna 130 Vehicle speed detection part

Claims (14)

In the digital data receiver
A first attenuator for attenuating the received signal from the first antenna;
A second attenuator for attenuating the received signal from the second antenna;
A combining unit that combines the first signal output from the first attenuator and the second signal output from the second attenuator;
A control unit for controlling the attenuation rate of the first attenuator or the attenuation rate of the second attenuator;
A digital data receiver comprising: A detection unit that detects a signal level of the signal output from the combining unit;
The digital data receiver according to claim 1, wherein the control unit controls an attenuation rate of the first attenuator or an attenuation rate of the second attenuator based on a detection result of the detection unit. A demodulator that demodulates the signal output from the combiner and detects the signal state;
The digital data receiver according to claim 1, wherein the control unit controls attenuation rates of the first attenuator and the second attenuator based on a detection result of a signal state in the demodulation unit.   The digital data receiver according to claim 3, wherein detection of a signal state in the demodulation unit is performed based on BER.   The digital data receiver according to claim 3, wherein detection of a signal state in the demodulation unit is performed based on CNR.   The said control part changes the attenuation factor of a said 1st attenuator and the attenuation factor of a said 2nd attenuator based on a predetermined | prescribed time constant or a predetermined | prescribed control amount, It is any one of Claims 1-5 The digital data receiver described.   The digital signal according to claim 6, wherein the predetermined time constant is set according to a signal level of a signal output from the combining unit, a traveling speed of a vehicle on which the digital data receiver is mounted, or a broadcast parameter. Data receiver.   The digital control according to claim 6, wherein the predetermined control amount is set according to a signal level of a signal output from the combining unit, a traveling speed of a vehicle on which the digital data receiver is mounted, or a broadcast parameter. Data receiver.   The control unit controls the attenuation rate of the first attenuator and the attenuation rate of the second attenuator so that a combined ratio of the first signal and the second signal becomes 100% in total. The digital data receiver according to any one of 1 to 8.   The control unit controls the attenuation rate of the first attenuator and the attenuation rate of the second attenuator so that a combined ratio of the first signal and the second signal is greater than 100%. Item 9. The digital data receiver according to any one of Items 1 to 8. A setting unit for setting a synthesis ratio of the first signal and the second signal;
The control unit according to any one of claims 1 to 10, wherein the control unit controls an attenuation rate of the first attenuator and the second attenuator so that a combination ratio set in the setting unit is obtained in an initial state. The digital data receiver described in the paragraph.   The digital data receiver according to claim 11, wherein the combination ratio set in the setting unit is a combination ratio in an end state of the digital data receiver.   The digital data receiver according to claim 11, wherein the composition ratio set in the setting unit is determined from history information. In the digital data receiver
An attenuator for attenuating at least one of the received signals from the plurality of antennas;
A combining unit that combines a signal output from the attenuator and a received signal from another antenna;
A control unit for controlling the attenuation rate of the attenuator;
A digital data receiver comprising:

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