JP2013168744A - In-vehicle receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-vehicle receiver in which noise can be canceled excellently through simple processing while reducing devices for noise cancellation.SOLUTION: In a radio receiver 1 which is mounted in a vehicle and comprises a broadcast wave antenna 10, under a bottom 31 of a car body 30 that is a place which a radio wave is more unlikely to reach than the broadcast wave antenna 10, a noise detection antenna 21 is installed being electrically spaced apart from the car body 30, and a voltage between the car body 30 and the noise detection antenna 21 is detected by a voltage detection circuit 22. The voltage detected by the voltage detection circuit 22 is regarded as a noise, and the noise is canceled from a radio wave received by the broadcast wave antenna 10.

Description

  The present invention relates to an in-vehicle receiver, and more particularly to a technique for removing noise from radio waves received by a receiving antenna.

  Various techniques for removing noise from radio waves received by a receiving antenna of a receiver are known. For example, Patent Document 1 discloses a technique for detecting a noise voltage fluctuation in a power supply line by a power supply line noise detection circuit and removing noise detected by the power supply line noise detection circuit from a radio wave received by an antenna by a noise canceller. Yes.

  In addition, Patent Document 1 also discloses a technique for removing noise generated by a plurality of electrical components disposed around a receiver. Specifically, when a plurality of electrical components arranged around the receiver is energized, a receiving circuit that receives a notification of energization from each electrical component is provided. In addition, a noise environment evaluation circuit including a weighting circuit and a voltage signal generation circuit is provided. In the weighting circuit, the weighting is determined according to the electrical component that has received the notification that the receiving circuit is energized, and the voltage signal generation circuit generates a voltage signal corresponding to the weighting. This voltage signal is removed from the radio wave received by the antenna as noise generated by the current electrical component.

Japanese Patent No. 4177437

  In the technique of Patent Literature 1, since it is necessary for the receiving circuit to receive a notification of energization from each electric component, it is necessary to connect the electric component and the receiving circuit with a wire harness, and the cost increases due to an increase in the number of wire harnesses. End up.

  In addition, since it is necessary to perform weighting processing by the weighting addition circuit of the noise environment evaluation circuit, there is also a problem that the processing load is high.

  In addition, the voltage signal generated by the voltage signal generation circuit of the noise environment evaluation circuit reflects only whether each electrical component is energized or not, but in reality, it is generated while each electrical component is energized. The noise you do is not always the same. Therefore, there is a possibility that the technique of Patent Document 1 cannot sufficiently remove noise.

  Patent Document 1 also discloses a technique for detecting noise by a noise detection circuit for a power supply line. As with the power supply line, a noise detection circuit may be provided for the electrical component. However, if a noise detection circuit is provided for each electrical component, the cost becomes very high.

  The present invention has been made based on this situation, and an object of the present invention is to provide an in-vehicle receiver that can remove noise satisfactorily by simple processing while reducing the number of devices for noise removal. Is to provide.

  In order to achieve the object, the present invention provides an in-vehicle receiver (1) including a receiving antenna (10) that is mounted on a vehicle and receives a target radio wave coming from outside the vehicle. A metal body (21, 21A) disposed at a position where the target radio wave is difficult to reach from a vehicle body of the vehicle, and a voltage detection unit for detecting a voltage between the metal body and the vehicle body ( 22) and a noise removing unit (17) for removing noise from the radio wave received by the receiving antenna using the voltage detected by the voltage detecting unit as noise.

  Various devices generate noise in vehicles, but the noise generated by various devices is due to the partial pressure between the stray capacitance between the vehicle body and the receiving antenna and the stray capacitance between the receiving antenna and the ground. I found it to be received by the antenna. Therefore, in the present invention, the metal body is disposed in a place where the target radio wave is less likely to reach than the receiving antenna, and is electrically separated from the vehicle body. Thereby, the noise which various apparatuses generate | occur | produce by the partial pressure of the stray capacitance between a vehicle body-metal body and the stray capacitance between a metal body-ground is received also by a metal body. Therefore, by detecting the voltage between the vehicle body and the metal body by the voltage detection unit, it is possible to detect noise having a frequency characteristic close to noise received by the receiving antenna.

  Moreover, the metal body is disposed in a place where the target radio wave is less likely to reach than the receiving antenna. Therefore, the voltage between the vehicle body and the metal body has a relatively high ratio of noise components as compared with the radio wave received by the receiving antenna. Therefore, noise can be satisfactorily removed from radio waves received by the receiving antenna by using the voltage detected by the voltage detection unit as noise.

  Further, since the noise indicated by the voltage between the metal body and the vehicle body is a combination of various noises, it is not necessary to provide a noise detector for each noise source. Therefore, cost can be reduced.

  Furthermore, since noise can be removed by the same process regardless of the number of noise sources, the process for removing noise becomes a simple process.

It is a block diagram which shows the whole structure of the vehicle-mounted radio receiver 1 to which the vehicle-mounted receiver of this invention was applied. FIG. 3 is a diagram illustrating the configuration and arrangement of a noise receiving unit 20. It is a figure which shows the path | route through which noise flows as an equivalent circuit. It is a figure which shows the path | route through which noise flows as an equivalent circuit. It is the schematic of the experiment which investigated the path | route which a noise flows. It is a graph which shows the result of the experiment shown in FIG. It is a figure which shows the vehicle body model 60 and the broadcast wave antenna 70 in the simulation which modeled the vehicle and measured the noise voltage. It is a figure which shows the vehicle body model 60 and the noise detection antenna 71 in the same simulation as FIG. 6A. It is a figure which shows the vehicle body model 60 and the noise source 72 in the same simulation as FIG. 6A. It is the result of the experiment conducted using the vehicle body model 60 shown in FIG. It is a figure explaining the content of the simulation which compared the broadcast wave detection sensitivity of the antenna 70 for broadcast waves, and the antenna 71 for noise detection. It is a graph which shows the result of the simulation which showed the content in FIG. It is a figure which shows the other example of arrangement | positioning of the antenna for noise detection.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a broadcast wave antenna 10 which is a reception antenna is an antenna installed in a vehicle to receive a broadcast wave (target radio wave) transmitted from a broadcast station outside the vehicle and reaching the vehicle. Therefore, it is installed at a position where it is easy to receive broadcast waves. As a specific installation position of the broadcast wave antenna 10, for example, there is an upper surface or a side surface of the vehicle body.

  The high frequency amplifier 11 amplifies the signal received by the broadcast wave antenna 10. The channel selection unit 12 is a part that is operated when the user performs a channel selection operation. The local oscillation unit 13 oscillates a signal having a frequency selected by the channel selection unit 12. The mixer unit 14 mixes the reception signal amplified by the high frequency amplification unit 11 and the signal generated by the local oscillation unit 13. Thus, the received signal is frequency-converted from a broadcast frequency signal to an intermediate frequency signal. The intermediate frequency amplification unit 15 amplifies the intermediate frequency signal frequency-converted by the mixer unit 14. The detector 16 detects the amplified intermediate frequency signal.

  The noise removing unit 17 removes noise from the signal detected by the detecting unit 16 based on the noise detected by the noise receiving unit 20. The signal processing unit 18 converts the electrical signal into an audio signal using the signal from which the noise has been removed by the noise removing unit 17 and outputs it.

  Next, the noise receiving unit 20 that is a feature of the present embodiment will be described. The noise receiving unit 20 includes a noise detection antenna 21 and a voltage detection circuit 22 shown in FIG. As shown in FIG. 2, the noise detection antenna 21 of this embodiment is attached to the bottom 31 of the vehicle body 30 via an insulator 32. That is, the noise detection antenna 21 is disposed below the bottom 31 of the vehicle body 30. At this position, the broadcast wave is less likely to reach than the broadcast wave antenna 10 because of the shielding by the vehicle body 30.

  The shape of the noise detection antenna 21 is a flat thin plate and is parallel to the bottom 31 of the vehicle body 30. In addition, the thickness of a thin plate means the board of the thinness of the grade called a film | membrane. The vehicle body 30 is made of metal (that is, made of conductor).

  The voltage detection circuit 22 detects a voltage between the bottom 31 of the vehicle body 30 and the noise detection antenna 21. The voltage detected by the voltage detection circuit 22 is input to the noise removing unit 17 as a signal indicating noise. The noise removing unit 17 removes noise based on the signal indicating this noise. For the specific processing for removing the noise, various known methods can be used. For example, the noise signal is amplified with a predetermined amplification factor, and the amplified signal is subtracted from the signal detected by the detection unit 16.

  Next, the fact that the voltage detected by the voltage detection circuit 22 indicates noise will be described with reference to FIGS. 3A and 3B. Note that FIG. 3B is the same circuit as FIG. 3A, but shows the broadcast wave antenna 10 and the noise detection antenna 21 more easily.

3A and 3B, Cg indicates the stray capacitance between the bottom 31 of the vehicle body 30 and the ground plane 40. Ca indicates a capacitance between the vehicle body 30 and the broadcast wave antenna 10, Cb indicates a capacitance between the broadcast wave antenna 10 and the ground plane 40, and Cc indicates a capacitance between the vehicle body 30 and the noise detection antenna. 21, and Cd represents the capacitance between the noise detection antenna 21 and the ground plane 40. Further, V _N indicates a noise voltage induced in the vehicle body 30 and flows from the bottom 31 of the vehicle body 30 to the ground plane 40 due to the capacitance Cg, and V _A is applied to the vehicle body 30 due to noise generated by electrical components inside the vehicle. A noise voltage induced and received by the broadcast wave antenna 10 is indicated, and V _Na indicates a noise voltage induced by the vehicle body 30 and received by the noise detection antenna 21.

As can be seen from the equivalent circuits of FIGS. 3A and 3B, the noise voltage V _N induced in the vehicle body 30 is received by the broadcast wave antenna 10 by the divided voltage of the capacitance Ca and the capacitance Cb. At the same time, the noise voltage V _N is received by the noise detection antenna 21 by the divided voltage of the electrostatic capacitance Cc and the electrostatic capacitance Cd. Therefore, the noise voltage _VNa is detected by the noise receiving unit 20, and noise can be removed from the radio wave received by the broadcast wave antenna 10 based on the detected noise voltage _VNa .

  Next, as an example of noise, an experiment in which a route through which noise flows when charging a plug-in hybrid (PHV) vehicle using the charging cable 50 will be described with reference to FIG. As shown in FIG. 4, in this experiment, a simulated power supply circuit (LISN) 52 is connected to the commercial power supply terminal 51, and the charging cable 50 is connected to the PHV vehicle via the LISN 52. 53 is also a cable. With this cable 53, the voltage between the vehicle body 30 and the ground plane 40 was measured when the negative terminal of the battery 54 and the ground plane 40 were connected and when the cable 53 was removed. Reference numeral 55 denotes a foaming material, which is an insulator. This experiment was conducted in an anechoic chamber.

  In the graph of FIG. 5 showing the results of the experiment, the horizontal axis indicates the frequency, and the vertical axis indicates the voltage between the vehicle body 30 and the ground plane 40. A solid line indicates a case where the cable 53 is removed, and a broken line indicates a case where the cable 53 is connected.

  From the experimental results shown in FIG. 5, the voltage between the vehicle body 30 and the ground plane 40 is reduced by connecting the cable 53, that is, by shorting the negative terminal of the battery 54 to the ground plane 40. I understand. From this, it can be seen that the common current generated in the charging cable 50 is transmitted to the vehicle body 30 and flows from the vehicle body 30 through the stray capacitance between the vehicle body 30 and the ground plane 40.

  FIGS. 6A, 6B, and 6C show a vehicle body model 60 in a simulation in which a vehicle is modeled and a noise voltage is measured. The vehicle body model 60 imitates a sedan-shaped vehicle, and its size is 1800 mm in width, 4800 mm in length, and 1700 mm in height (200 mm above ground).

  FIG. 6A shows the installation position of the broadcast wave antenna 70 in the vehicle body model 60. The broadcast wave antenna 70 is installed on the roof 61 of the vehicle body model 60. More specifically, it was installed 300 mm to the right and 600 mm behind the center of the roof 61. The element length was 300 mm. However, 60 mm out of 300 mm is the length on the installation side.

  FIG. 6B shows the installation position of the noise detection antenna 71 in the vehicle body model 60. The noise detection antenna 71 is installed on the bottom surface 62 of the vehicle body model 60. More specifically, the bottom surface 62 was installed at a position of 900 mm before the center. The distance from the bottom surface 62 was 10 mm. The shape of the noise detection antenna 71 was a rectangular thin film of 600 mm × 600 mm.

  FIG. 6C shows the installation position of the noise source 72 in the vehicle body model 60. The noise source 72 was installed in the vehicle body model 60 at a position corresponding to the actual engine room of the vehicle. The amplitude of noise generated by the noise source 72 is 1V.

  In FIG. 7 showing the result of the simulation of FIG. 6, the horizontal axis represents frequency and the vertical axis represents noise voltage. The black square is the terminal voltage of the broadcast wave antenna 70, and the white diamond is the terminal voltage of the noise detection antenna 71. As can be seen from FIG. 7, the noise detection antenna 71 can detect noise more efficiently than the broadcast wave antenna 70.

  Next, a simulation for confirming that the broadcast wave antenna 70 has better detection sensitivity than the noise detection antenna 71 will be described. In this simulation, as shown in FIG. 8, the antenna 80 of the broadcasting station has an antenna length of 10 m, and the distance between the antenna 80 and the vehicle body model 60 is 100 m.

  In the graph of the simulation result shown in FIG. 9, the horizontal axis represents frequency and the vertical axis represents voltage. Black squares and white diamonds are the terminal voltage of the broadcast wave antenna 70 and the terminal voltage of the noise detection antenna 71, respectively, as in FIG. As can be seen from FIG. 9, the noise detection antenna 71 also receives broadcast waves, but the broadcast wave antenna 70 can receive broadcast waves more efficiently.

  The following can be understood from the simulation results shown in FIGS. That is, the broadcast wave antenna 70 and the noise detection antenna 71 both detect broadcast waves and noise, but the noise detection antenna 71 has better detection sensitivity for noise, while the broadcast wave antenna for broadcast waves. It can be seen that 70 has better detection sensitivity. Therefore, it can be said that noise can be effectively removed from the signal received by the broadcast wave antenna 70 based on the signal detected by the noise detection antenna 71.

  As described above, noises generated by various devices in the vehicle are the stray capacitance Ca between the vehicle body 30 and the broadcast wave antenna 10 and the stray capacitance between the broadcast wave antenna 10 and the ground plane 40. It is received by the broadcast wave antenna 10 by the partial pressure of Cb (FIG. 3). In the present embodiment, the noise detection antenna 21 is disposed below the bottom 31 of the vehicle body 30. Therefore, the noise is applied to the noise detection antenna 21 by the partial pressure of the stray capacitance Cc between the vehicle body 30 and the noise detection antenna 21 and the stray capacitance Cd between the noise detection antenna 21 and the ground plane 40. Is also received.

Therefore, by detecting the voltage V _Na between the vehicle body 30 and the noise detection antenna 21, noise having a frequency characteristic close to that of the noise received by the broadcast wave antenna 10 can be detected.

Moreover, the noise detection antenna 21 is disposed in a place where the broadcast wave is less likely to reach than the broadcast wave antenna 10. Therefore, the voltage V _Na between the vehicle body 30 and the noise detection antenna 21 has a relatively high ratio of noise components as compared with the radio wave received by the broadcast wave antenna 10. Therefore, noise can be satisfactorily removed from the radio wave received by the broadcast wave antenna 10 by using the voltage V _Na as noise.

Further, since the noise indicated by the voltage V _Na is a combination of various noises, it is not necessary to provide a noise detector for each noise source. Therefore, cost can be reduced. Furthermore, since noise can be removed by the same process regardless of the number of noise sources, the process for removing noise becomes a simple process.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The following embodiment is also contained in the technical scope of this invention, and also the summary other than the following is also included. Various modifications can be made without departing from the scope.

  For example, in the above-described embodiment, the noise detection antenna 21 is disposed below the vehicle body 30, but as shown in FIG. 10, the noise detection antenna 21 </ b> A is arranged inside the vehicle (that is, a vehicle formed by the vehicle body 30. It may be arranged in the inner space. The noise detection antenna 21A shown in FIG. 10 is disposed on the bottom 31 of the vehicle body 30 via an insulator 32 in the vehicle.

  As shown in FIG. 10, even when the noise detection antenna 21 </ b> A is disposed in the interior space of the conductive vehicle body 30, the vehicle body 30 has a window portion. Through the stray capacitance between the ground plane 40 and the ground plane 40. However, the noise detection level is lower than that of the noise detection antenna 21 disposed below the vehicle body 30. However, when it is arranged in a vehicle, it is difficult to receive broadcast waves, so that noise can be detected with high accuracy.

  Further, although the above-described noise detection antennas 21 and 21A have a flat plate shape, the noise detection antenna may have another shape (for example, a box shape or a spherical shape). Further, a line shape or a shape in which lines are combined, that is, a net shape may be used.

  Moreover, although the above-mentioned embodiment was a radio receiver 1, that is, a receiver that receives a broadcast wave, the present invention can also be applied to a receiver for bidirectional communication.

1: Car radio receiver (car receiver)
10: Broadcast wave antenna (receiving antenna)
17: Noise removing unit 20: Noise receiving unit 21, 21A: Noise detection antenna (metal body)
22: Voltage detection circuit (voltage detection unit)
30: Body 31: Bottom

Claims (4)

An in-vehicle receiver (1) equipped with a receiving antenna (10) that is mounted on a vehicle and receives a target radio wave coming from outside the vehicle,
A metal body (21, 21A) disposed at a position where the target radio wave is less likely to reach than the receiving antenna, and electrically separated from the vehicle body (30) of the vehicle;
A voltage detector (22) for detecting a voltage between the metal body and the vehicle body;
A vehicle-mounted receiver comprising: a noise removing unit (17) that removes noise from radio waves received by the receiving antenna using the voltage detected by the voltage detecting unit as noise. In claim 1,
The in-vehicle receiver, wherein the metal body (21) is disposed below the bottom portion (31) of the vehicle body (30) and electrically separated from the bottom portion. In claim 1,
The in-vehicle receiver, wherein the metal body (21A) is disposed electrically separated from the vehicle body in a vehicle interior space formed by the vehicle body. In any one of Claims 1-3,
The in-vehicle receiver, wherein the metal bodies (21, 21A) are flat.

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