JP2012105113A - On-vehicle receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle receiver allowing for continuous receiving of digital terrestrial television broadcasting.SOLUTION: An on-vehicle receiver 1 comprises a tuner 12 which is configured to input thereto a receiving signal of digital terrestrial television broadcasting through an antenna 11, and performs gain adjustment of the receiving signal and a broadcasting station selection. The on-vehicle receiver 1 further comprises: a band pas filter 17 for removing an interference wave component from the receiving signal of the antenna 11; and determination means 10 for determining whether or not to receive the digital terrestrial television broadcasting on the basis of an output signal of the tuner 12. The receiving signal of the antenna 11 is inputted to the tuner 12 without interposing the band pass filter 17 therebetween. When the determination means 10 determines not to receive the receiving signal, and the receiving signal of the antenna 11 is strong, the receiving signal of the antenna 11 is inputted to the tuner 12 through the band pass filter 17.

Description

  The present invention relates to a vehicle-mounted receiving device that is mounted on a vehicle and receives digital terrestrial television broadcasting, and a reception control method for the vehicle-mounted receiving device.

  Conventionally, a vehicle-mounted receiving device that is mounted on a vehicle and can receive terrestrial digital television broadcasting is known. This type of in-vehicle receiving apparatus removes interference waves outside the frequency band of digital terrestrial television broadcasting using a band-pass filter built in the tuner (see, for example, Patent Document 1).

JP 2009-224908 A

However, a frequency band close to the frequency band of terrestrial digital broadcasting is used for intelligent transportation systems, mobile phones, and the like. Bands such as intelligent transportation systems and mobile phones have a small frequency interval (guard band) with the band of television broadcasting. In order to prevent radio waves having a small frequency interval from causing mutual interference, it is necessary to incorporate a band pass filter having a very steep attenuation characteristic in the tuner. However, such a high-performance band-pass filter having a steep attenuation characteristic is very expensive.
In particular, in-vehicle receivers receive broadcasts with a plurality of antennas in order to stabilize output video or audio signals, perform frequency conversion of radio waves received by tuners connected to each antenna, Synthetic diversity reception is performed in which an output signal is synthesized by a demodulation circuit and converted into a video or audio signal. For this reason, it has been difficult in terms of cost to employ a high-performance band-pass filter for each tuner of a vehicle-mounted receiving apparatus that performs combined diversity reception.

  In order to reduce the cost, it is conceivable to use an inexpensive band-pass filter with a gentle attenuation characteristic. However, when a band-pass filter having a narrow bandwidth of the radio wave to be passed is used to remove the interference wave outside the band, the received wave within the band is attenuated. On the other hand, when a band-pass filter having a wide band of radio waves to be passed is used so as not to attenuate the received waves in the band, there is a problem that the out-of-band interference waves cannot be sufficiently attenuated.

In addition, this type of in-vehicle receiving apparatus includes an AGC circuit in a tuner and performs gain adjustment of a signal received by the AGC circuit in order to stabilize the output. For this reason, when a strong interference wave outside the band is input to the tuner, there is a problem that the AGC circuit suppresses the reception sensitivity and the terrestrial digital television cannot be received.
An object of the present invention is to provide a vehicle-mounted receiving device that solves the problems of the conventional techniques described above and enables continuous reception of digital terrestrial television.

  In order to achieve the above object, the present invention provides an in-vehicle receiver provided with a tuner for receiving a terrestrial digital television broadcast reception signal via an antenna, adjusting the gain of the reception signal, and selecting a broadcast station. A band-pass filter that removes an interference wave component from a received signal from the antenna, and a determination unit that determines whether or not the digital terrestrial television broadcast can be received based on an output signal of the tuner, the band-pass filter When the reception signal from the antenna is input to the tuner without being passed through, and it is determined that reception is impossible by the determination means, and the reception signal from the antenna is strong, the signal is transmitted from the antenna through the band pass filter. The received signal is input to the tuner.

  In this configuration, when the reception signal from the antenna is input to the tuner via the band-pass filter, if it is determined by the determination means that reception is not possible, the same as the selected broadcast station It may be configured to search for and receive broadcasts from relay stations that are broadcasting. A plurality of pairs of the antenna and the tuner may be provided, and the output signals of the tuners may be demodulated by diversity combining.

  According to the present invention, gain adjustment is performed in accordance with a strong interference wave outside the band, and the attenuation characteristic is moderately low only when the signal of the terrestrial digital television broadcast is relatively weak and cannot be received. An effective band pass filter can be effectively used to attenuate the interference wave included in the received signal from the antenna. As a result, when the signal is not affected by the interference wave, the received signal from the antenna is input to the tuner without passing through the bandpass filter, so that the received signal is affected by attenuation or insertion loss by the bandpass filter. In other words, there is an effect that the reception level can be improved to enable continuous reception of digital terrestrial television.

It is a block diagram which shows the functional structure of the vehicle-mounted receiving apparatus of this embodiment. It is a flowchart which shows operation | movement of the vehicle-mounted receiving apparatus. It is a figure which shows the characteristic with respect to the input level of an AGC voltage. It is a figure which shows the attenuation | damping characteristic of LPF. It is a block diagram which shows the functional structure of the vehicle-mounted receiving apparatus of another embodiment. It is a flowchart which shows operation | movement of another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a functional configuration of an in-vehicle receiver 1 according to an embodiment to which the present invention is applied. The in-vehicle receiving device 1 is a receiving device for receiving a terrestrial digital television broadcast mounted on a vehicle. The in-vehicle receiving device 1 includes a microcomputer 10, and the microcomputer 10 functions as a control unit that controls each unit of the in-vehicle receiving device 1. Further, the microcomputer 10 performs inter-system communication with an ITS (Intelligent Transport System) receiver 2 and a navigation system 3 that transmit and receive radio waves related to information emitted from an intelligent road traffic system (ITS system). The ITS transceiver 2 includes a reception antenna 2a and performs wireless communication with an ITS system that is an external system.

The in-vehicle receiving device 1 includes four antennas 11A to 11D that receive digital terrestrial television broadcasting (broadcast waves), and reception signals (RF signals) of the antennas 11A to 11D are transmitted to the antennas 11A to 11D. And input to the connected tuners 12A to 12D. Each of the tuners 12A to 12D includes an AGCAMP (Automatic Gain Control Amplifier) 13A to 13D and tuning units 31A to 31D.
The RF (Radio Frequency) signal input to the tuners 12A to 12D varies in amplitude in a moving vehicle. Therefore, the gains of the RF signals input to the tuners 12A to 12D are adjusted by the AGCAMPs 13A to 13D to make the output constant. The AGCAMPs 13A to 13D reduce the applied voltage when the signals input to the tuners 12A to 12D are strong, and increase the applied voltage when the signals input to the tuners 12A to 12D are weak. Adjust the gain so that it is constant.

The tuning units 31 </ b> A to 31 </ b> D perform channel selection under the control of the microcomputer 10. The tuners 12 </ b> A to 12 </ b> D downconvert the RF signal of the reception frequency (reception channel) corresponding to the channel selection to generate an IF (Intermediate Frequency) signal. The generated IF signal is output to an OFDM (Orthogonal Frequency Division Multiplexing) demodulation IC 15.
When a broadcast station is selected by the user via an operation unit (not shown), the reception frequency is specified by the microcomputer 10 searching for a receivable relay station or affiliated station based on the information on the broadcast station. The The relay station is a frequency channel that performs the same broadcast as the selected broadcast station.

  The OFDM demodulation IC 15 performs a combination diversity process that combines the IF signals input from the tuners 12A to 12D. Further, the OFDM demodulation IC 15 generates a TS (Transport Stream) signal by OFDM demodulating the IF signal. The generated TS signal is output to the MPEG-IC 16. The TS signal includes a video signal and an audio signal encoded by the MPEG (Moving Picture Experts Group) method. The MPEG-IC 16 decodes these TS signals to generate a video signal and an audio signal. The generated video signal and audio signal are output to a video / audio output unit mounted on an in-vehicle device such as an in-vehicle audio device (not shown). This makes it possible to view digital terrestrial television broadcasting in the passenger compartment.

  The OFDM demodulation IC 15 also outputs the BER and AGC levels to the microcomputer 10. The microcomputer 10 functions as a determination unit that detects the reception status (reception level) of each of the tuners 12A to 12D from the level of the input TS signal and determines whether or not the digital terrestrial television broadcast can be received. When the reception level falls below a predetermined threshold value (for example, a level that cannot withstand viewing), the microcomputer 10 determines that the currently received reception frequency cannot be received.

  The gain (amplification factor) of the AGCAMPs 13A to 13D may be controlled in the tuner, or based on the AGC signal indicating the received radio wave intensity output from the AGCAMPs 13A to 13D, the OFDM demodulating IC 15 or the microcomputer 10 may be performed. The signals whose gains have been adjusted by the AGCAMPs 13A to 13D are then generated by generating IF signals from the RF signals of the reception frequencies selected by the microcomputer 10 in the tuning units 31A to 31D.

  Switches (switching means) 14A to 14D are provided between the antennas 11A to 11D and the tuners 12A to 12D, respectively. The switches 14A to 14D are provided so as to be switchable. The switches 14A to 14D are controlled and switched by the microcomputer 10, and receive signals (RF signals) received by the antennas 11A to 11D are LPFs (bandpass filters) provided between the antennas 11A to 11D, respectively. Low Path Filter) is input to tuners 12A to 12D via 17A to 17D, or is input to tuners 12A to 12D without LPF 17A to 17D.

Next, reception control of the in-vehicle receiver 1 that removes out-of-band interference waves will be described with reference to FIGS. 3 and 4 using FIG.
During normal reception of digital terrestrial television broadcasting, the microcomputer 10 determines the reception status from the BER or AGC level (reception level) based on the outputs of the tuners 12A to 12D (step S1). If it is determined that the reception level is less than the threshold value (reception is impossible) (step S1: Yes), the microcomputer 10 next determines whether the ITS transceiver 2 is communicating (step S2).

  Generally, terrestrial digital and analog terrestrial television broadcasts use the UHF band of 470 MHz to 710 MHz, but the ITS system uses radio waves in a band (715 MHz to 725 MHz) close to the band used for this television broadcast. Are communicating. When radio waves of the ITS system are input to the in-vehicle receiving device 1, since the transmission / reception power of the ITS system is large, the interference signal component from the ITS system is included in the received signal, and television broadcasting is suppressed, Digital terrestrial television broadcasting cannot be received. If the ITS transceiver 2 is not communicating (step S2: No), the microcomputer 10 terminates the process because it is determined that the cause of the reception failure is not due to the interference wave from the ITS system. On the other hand, when the ITS transceiver 2 is communicating (step S2: Yes), strong interference waves outside the TV broadcast band from the ITS system are input to the tuners 12A to 12D, and the TV broadcast is suppressed. It is possible that

  In AGCAMP 13A to 13D, the control voltage (AGC voltage) applied for gain adjustment changes according to the strength of the input signal. As shown in FIG. 3, when the reception signal input to each of the tuners 12 </ b> A to 12 </ b> D becomes strong, the AGC voltage has a characteristic to decrease in order to suppress reception sensitivity. When the input of the jamming wave is strong, gain adjustment is performed in accordance with the strong jamming wave, and the terrestrial digital television broadcast signal becomes relatively weak and may not be received. Therefore, in order to detect the strength of the received signal using the characteristics of the AGC voltage, the microcomputer 10 detects the AGC voltage (step S3). Subsequently, the microcomputer 10 determines whether the AGC voltage is equal to or lower than the threshold value a (step S4). When the AGC voltage is less than or equal to the threshold value a, it is considered that the received signal from the antenna probably contains a disturbing wave component, the received signal becomes strong, and the sensitivity of the AGCAMPs 13A to 13D is suppressed.

The determination as to whether or not the in-vehicle receiver 1 is affected by a strong interference wave is made when the AGC voltage of at least one of the antennas 11A to 11D is equal to or lower than a preset range value a. It is good also as a structure which determines with being influenced by the strong interference wave. Or it is good also as a structure which determines with having received the influence of a strong jamming wave, when the AGC voltage of a some antenna system becomes below the threshold value a among antennas 11A-11D.
In the present embodiment, the AGC voltage is detected to determine the strength of the received signal. However, a configuration for separately providing a means for detecting the strength of the received signal may be used.

  When it is determined that the AGC voltage is equal to or lower than the threshold value a (step S4: Yes), it is considered that the interference signal component is probably included in the received signal. Therefore, the switches 14A to 14D are switched to the LPFs 17A to 17D, respectively, in order to attenuate the interference band radio waves (step S5). As shown in FIG. 4, the attenuation characteristics of the LPFs 17A to 17D are gentle and attenuate with respect to the band of the ITS system, but also attenuate with respect to the band of digital television broadcasting at a frequency equal to or higher than BMhz in FIG. It has the characteristic to do.

  When the switches 14A to 14D are switched to the LPFs 17A to 17D, the RF signals received by the antennas 11A to 11D are attenuated through the LPFs 17A to 17D and input to the tuners 12A to 12D. At this time, if the reception frequency is a frequency equal to or lower than B MHz in FIG. 4, there is no change in the band pass characteristic of the television broadcast, so the interference wave is attenuated and the reception level is improved. However, when the reception frequency is higher than B MHz, the interference level attenuates, but the reception level also attenuates due to the influence of the LPFs 17A to 17D. Therefore, it may be determined that reception is not possible based on the outputs of the tuners 12A to 12D. Therefore, the microcomputer 10 switches the switches 14A to 14D to the LPFs 17A to 17D, respectively, and when the reception signals of the antennas 11A to 11D are input to the tuners 12A to 12D via the LPFs 17A to 17D, the reception level is high. It is determined whether it is less than the threshold value (step S6).

  If the reception level is within the receivable range (step S6: No), the microcomputer 10 ends the process. If it is determined that the reception level is less than the threshold value (step S6: Yes), the microcomputer 10 performs the same broadcast as the currently selected broadcast station at a frequency different from the currently received reception frequency. The broadcast of the relay station is searched (step S7). There are many relay stations in each wide area such as Kanto, Chukyo, Kinki, etc., and in the same prefecture area. The channel configuration information of each relay station and the frequency information corresponding to the channel configuration information are described in an NIT (Network Information Table) stored in a storage unit (not shown) of the in-vehicle receiving device 1. The microcomputer 10 executes a search for a receivable relay station that is broadcasting in the frequency band of BMHz or lower in FIG. 4 from the information described in the NIT (step S7). Next, the microcomputer 10 determines whether or not the searched reception frequency is receivable from the reception level based on the outputs from the tuners 11A to 11D (step S8). If the receivable relay station cannot be detected, the microcomputer 10 may be configured to search the affiliated station of the currently selected broadcast station from the NIT.

  When a receivable relay station is detected (step S8: No), the microcomputer 10 selects the frequency of the detected relay station (step S9) and selects the tuner units 31A to 31D of the tuners 12A to 12D. Set the selected frequency. If no receivable relay station is detected after execution of the relay station search (step S8: Yes), the microcomputer 10 determines that there is no corresponding relay station and switches the switches 14A to 14D (step S10). The RF signals received by the antennas 11A to 11D are directly input to the tuners 12A to 12D. Subsequently, the microcomputer 10 returns the reception frequency set to the tuning units 31A to 31D to the original reception frequency (step S11), and ends the process.

According to these configurations, the antennas 11 </ b> A to 11 </ b> D are received only when the radio wave of the ITS system that uses a frequency band close to the frequency band of digital terrestrial television broadcasting is input to the in-vehicle receiver 1 as an interference wave. Switches 14A-14D can be switched to attenuate RF signals through LPFs 17A-17D. Therefore, the RF signals received by the antennas 11A to 11D are directly input to the tuners 12A to 12D and are not attenuated by the LPFs 17A to 17D except when the reception level is lowered due to the influence of the interference wave. If reception is not possible due to the influence of the interference wave and reception is not possible even if the interference wave is attenuated through the LPFs 17A to 17D, a relay station in the frequency band not attenuated by the LPFs 17A to 17D is searched for and selected. Therefore, the reception level can be maintained.
This effectively uses a bandpass filter (bandpass filter) with a gentle attenuation characteristic that is cheaper than a bandpass filter with a steep attenuation characteristic to effectively attenuate the interference wave and receive it. By executing a combination of level confirmation and relay station search, the user can continue to watch digital terrestrial television broadcasting in the vehicle.

Next, another embodiment will be described.
The in-vehicle receiving device 1 is not limited to out-of-band radio waves from the ITS system described above, but out-of-band radio waves such as mobile phones using a band of 730 MHz to 770 MHz and taxi radio using a frequency band lower than TV broadcasting. May be affected by interference. Therefore, in another embodiment, as shown in FIG. 5, BPFs (Band Path Filters) 27 </ b> A to 27 </ b> D that are band-pass filters that attenuate both a higher frequency band than the television broadcast and a lower frequency band than the television broadcast. Are arranged between the antennas 11A to 11D and the tuners 12A to 12D.
When the microcomputer 10 determines that the reception level is less than the threshold value (cannot be received) during normal reception of digital terrestrial television broadcasting, as shown in FIG. 6, the in-vehicle receiver 1 of another embodiment (step S21). : Yes), the microcomputer 10 next determines whether the control voltage (AGC voltage) of the AGCAMPs 13A to 13D is equal to or less than the threshold value a (step S22).

When it is determined that the AGC voltage is equal to or lower than the threshold value a (step S22: Yes), it is conceivable that the in-vehicle receiver 1 is affected by a strong interference wave outside the television broadcast band. Therefore, in order to attenuate the interference band, the switches 14A to 14D are respectively switched to the BPF 27A to 27D side in FIG. 6 (step S23). The BPFs 27 </ b> A to 27 </ b> D are configured by combining an HPF (High Path Filter) having a gentle attenuation characteristic and an LPF.
The microcomputer 10 again determines whether or not the reception level is less than the threshold value after switching the switches 14A to 14D to the BPFs 27A to 27D, respectively (step S24).

  When the microcomputer 10 determines that the reception level is within the receivable range (step S24: No), the microcomputer 10 ends the process. If it is determined that the reception level is less than the threshold value (step S24: Yes), the microcomputer 10 performs the same broadcast as the currently selected broadcast station at a frequency different from the currently received reception frequency. A search for a relay station is executed (step S25). Subsequently, the microcomputer 10 determines whether or not the searched reception frequency is receivable from the reception levels output from the tuners 11A to 11D (step S26).

  When a receivable relay station is detected (step S26: No), the microcomputer 10 selects the tuning units 31A to 31D for the detected frequency of the relay station (step S27). If no receivable relay station is detected after execution of the relay station search (step S26: Yes), the microcomputer 10 determines that there is no corresponding relay station, and switches the switches 14A to 14D (step S28). The RF signals received by the antennas 11A to 11D are directly input to the tuners 12A to 12D. Subsequently, the microcomputer 10 returns the reception frequency selected by the tuning units 31A to 31D to the original reception frequency (step S29), and ends the process.

According to these configurations, during reception of terrestrial digital TV broadcast, when reception of terrestrial digital TV broadcast becomes impossible due to the influence of interference waves outside the frequency band of terrestrial digital TV broadcast, The switches 14A to 14D are switched to the BPF 27A to 27D side, and the BPFs 27A to 27D attenuate the interference wave having a frequency lower than the frequency band of the terrestrial digital television broadcast and the interference wave having a frequency higher than the frequency band of the terrestrial digital television broadcast. It can be performed. If reception is not possible due to the influence of the interference wave and reception is impossible even if the interference wave is attenuated through the BPFs 27A to 27D, a relay station in the frequency band that is not attenuated by the BPFs 27A to 27D is searched for and selected. Therefore, the reception level can be maintained.
Therefore, even when a strong jamming wave out of the band enters, the inexpensive HPF and LPF are effectively used to attenuate the jamming wave, and further, the reception level check and the relay station search are executed in combination. Thus, the user can continuously watch digital terrestrial television broadcasting in the vehicle.

  As described above, only when the AGCAMP 13A to 13D adjusts the gain in accordance with the strong interference wave outside the band and the signal of the digital terrestrial television broadcasting becomes relatively weak and cannot be received, the antenna 11A. Since the received signal of ˜11D is removed through the band-pass filter, the received signal is input to the tuners 12 </ b> A to 12 </ b> D without passing through the band-pass filter when the interference signal is not affected. It is not affected by attenuation or insertion loss due to the pass filter. As a result, the reception level can be improved, and continuous reception of terrestrial digital television can be enabled.

  In addition, even when the reception signals of the antennas 11A to 11D input to the tuners 12A to 12D through the band pass filter are attenuated by the band pass filter and cannot be received, the same broadcast as the selected broadcast station is performed. Therefore, it is possible to search for a receivable relay station that performs reception, and to use an inexpensive band-pass filter with a gentle attenuation characteristic to reduce costs and enable continuous reception of digital terrestrial television.

  In addition, it is possible to improve the stability of the reception level by providing a plurality of pairs of antennas and tuners and diversity-combining and demodulating the output signals of the tuners 12A to 12D. In addition, when each tuner is connected to a tuner and affected by jamming waves, the bandpass filters connected to each tuner remove the jamming waves, but each bandpass filter has a gentle attenuation characteristic. Since a low-cost bandpass filter is used, it is possible to reduce the cost, perform composite diver reception, improve the stability of the reception level, and enable continuous reception of digital terrestrial television.

DESCRIPTION OF SYMBOLS 1 In-vehicle receiver 2 ITS transceiver 3 Navigation system 10 Microcomputer (determination means, voltage detection means)
11A, 11B, 11C, 11D Antenna 12A, 12B, 12C, 12D Tuner 13A, 13B, 13C, 13D AGCAMP (gain adjustment means)
14A, 14B, 14C, 14D Switch (switching means)
15 OFDM demodulation IC (demodulation means)
17A, 17B, 17C, 17D LPF (band pass filter)
27A, 27B, 27C, 27D BPF (band pass filter)

Claims (3)

In a vehicle-mounted receiving device provided with a tuner for receiving a terrestrial digital TV broadcast reception signal via an antenna, adjusting the gain of the reception signal, and selecting a broadcast station,
A band-pass filter that removes interference wave components from the received signal from the antenna; and
Determination means for determining whether or not to receive the terrestrial digital television broadcast based on the output signal of the tuner,
When the reception signal from the antenna is input to the tuner without passing through the bandpass filter, and when the determination means determines that reception is impossible and the reception signal from the antenna is strong, the signal is passed through the bandpass filter. And receiving a signal received from the antenna into the tuner.   When the reception signal from the antenna is input to the tuner via the band pass filter and the determination means determines that reception is not possible, the same broadcast as the selected broadcast station is performed. The in-vehicle receiving apparatus according to claim 1, wherein a broadcast of a relay station is searched and received.   The in-vehicle receiver according to claim 1 or 2, wherein a plurality of pairs of the antenna and the tuner are provided, and the output signals of the tuners are demodulated by diversity combining.

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