JP2004297498A - In-vehicle antenna assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost in-vehicle antenna assembly to which a cable is easily attached by reducing the number of lines of the cable. <P>SOLUTION: The in-vehicle antenna assembly comprises at least one or more first antennas (2a) capable of receiving first frequency bands, a plurality of second antennas (2b to 2d) capable of receiving second frequency bands and an antenna switching circuit (1) which switches the antennas according to a voltage of a control signal and is provided with a selection means (3) which outputs the control signal which has a voltage equal to or higher than a prescribed threshold when the first frequency band is selected and has a voltage lower than the prescribed threshold when the second frequency band is selected to the antenna switching circuit (1). Then, the antenna switching circuit (1) switches the antenna to the first antenna (2a) when the control signal has a voltage equal to or higher than the prescribed threshold and switches the antenna to one of the plurality of second antennas (2b to 2d) according to the voltage when the control signal has a voltage smaller than the prescribed threshold. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an in-vehicle antenna device that can receive FM and TV, and more particularly to an in-vehicle antenna device that uses a plurality of antennas to select an antenna having the best reception state.
[0002]
[Prior art]
As an in-vehicle TV antenna device, an antenna device in which two antenna elements are arranged at right and left symmetric positions behind the vehicle body is generally used. In this antenna device, each of the four elements is designed to have a length capable of receiving TV broadcast radio waves with high sensitivity. By selecting a signal having the highest gain from among the received signals supplied by these antenna elements by a diversity circuit or the like, high-sensitivity reception can be performed.
[0003]
2. Description of the Related Art In recent years, a VICS service (Vehicle Information and Communication System) for providing traffic congestion information and the like to individual vehicles in real time has been provided. VICS information is provided from the VICS center by radio beacons, optical beacons, FM multiplex broadcasting, and the like. A navigation device that searches for an optimal route to a destination using the VICS information is commercially available. Many of these navigation devices are capable of receiving FM multiplex broadcasts and TV broadcasts.
[0004]
As an antenna for an FM / TV receiver of such a navigation device, an in-vehicle antenna device that can receive FM broadcasts with sufficient sensitivity using a plurality of antenna elements has been considered (for example, Patent Document 1). 1).
[0005]
In such an in-vehicle antenna device, signals received by a plurality of antenna elements are sent to an FM / TV receiver. Therefore, as many cables as the number of antenna elements must be provided from outside the vehicle body to the FM / TV receiver. , The task was cumbersome.
[0006]
Therefore, as shown in FIG. 2, an antenna switching circuit (1) is provided behind the car, connected to a plurality of antenna elements (2a to 2d), and received by the antenna element selected by the antenna switching circuit (1). An in-vehicle antenna device is conceivable in which a signal is sent to the FM / TV receiver (3) to reduce the number of cables (4) and to simplify the installation work.
[0007]
In such an in-vehicle antenna device, the switching of antenna elements can be performed at high speed during TV reception, so that there is no hindrance to viewing, and switching to an antenna element with good reception sensitivity is always beautiful. It is desirable to be able to display various images.
[0008]
On the other hand, if the antenna is switched during FM reception for receiving VICS information, the VICS information transmitted as continuous data is lost at the time of antenna switching, and the data cannot be restored. It is desirable not to switch.
[0009]
Therefore, the configuration of the vehicle-mounted antenna device shown in FIG. 2 will be described. The antenna switching circuit (1) includes a band switching circuit (6) and a TV antenna switching circuit (8). The band switching circuit (6) receives the FM by a band switching signal output from the FM / TV receiver (3), which is information on which of the FM and TV is selected, via the band switching cable (5). Or TV reception, and switches between the FM antenna element (2a) and the TV antenna element (2b to 2d) according to the result of the determination. This band switching signal is represented by a binary signal of Hi and Low. When the FM is selected, it is fixed by the FM antenna element (2a). When a TV is selected, the TV antenna switching circuit (8) transmits a reception signal received by each TV antenna element (2b to 2d) at predetermined time intervals to the FM / TV receiver via the cable (4). Output to (3).
[0010]
The FM / TV receiver (3) is tuned and controlled by tuning control means (not shown). After tuned to the received signal, the received signal is converted to a predetermined intermediate frequency (video signal = 58.75 MHz, audio signal = 54.25 MHz) to generate an intermediate frequency signal. Then, the signal of the adjacent channel is removed from the intermediate frequency signal, and only the reception channel is extracted. The reception channel is amplified to generate a video signal. An image can be displayed by color demodulating the image signal and supplying it to a display unit (not shown). Further, a part of the video signal is demodulated and output as sound when output to a speaker (not shown).
[0011]
The FM / TV receiver (3) outputs the above-described video signal to the TV antenna switching circuit (8) via the TV antenna switching cable (7). The TV antenna switching circuit (8) has the highest voltage value from the voltage value of the video signal generated from the reception signal received by each of the antenna elements (2b to 2d) input from the FM / TV receiver (3). The TV antenna switching circuit (8) outputs the reception signal of each antenna to the FM / TV receiver (3) again after a predetermined time has passed, selecting the antenna element having the best reception sensitivity.
[0012]
Alternatively, as shown in FIG. 3, a configuration in which the band switching circuit (6) is omitted from the above-described configuration is also conceivable. With this configuration, when the band switching signal from the FM / TV receiver (3) is determined to be FM, the antenna switching circuit (8) is fixed to the FM antenna element (2a). When it is determined that the TV is a TV, the antenna is switched from the TV antenna elements (2b to 2d) to the antenna element that can receive with the highest sensitivity by the above-described method. With this configuration, the band switching circuit (5) becomes unnecessary, and a simple circuit configuration can be achieved.
[0013]
[Patent Document 1]
JP-A-11-122020 (pages 3-5, FIG. 4)
[0014]
[Problems to be solved by the invention]
However, in the above-described in-vehicle antenna device, the FM / TV receiver (3) always demodulates the received signal received by the antenna elements (2b to 2d) into a demodulated signal during TV reception, and outputs the demodulated signal to the antenna switching circuit (3). Output to 1). The TV antenna switching signal is a voltage value that varies depending on the reception sensitivity, and may have a voltage in the same range as the band switching signal. Therefore, switching between the FM antenna (2a) and the TV antenna (2b to 2d) is performed as follows. It is necessary to output the band switching signal to the antenna switching circuit (1) so that the signal can be distinguished from the demodulated signal as another signal. Therefore, in any of the above-described configurations, in addition to the cable (4) for transmitting the reception signal received by the antenna elements (2a to 2d) to the FM / TV receiver (3), the band switching cable ( 5) A TV antenna switching cable (7) is required. Therefore, there is a problem in that the installation of these cables becomes troublesome and the cost of the cables increases.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, in a vehicle-mounted antenna device according to the present invention, at least one or more first antennas capable of receiving a first frequency band and a plurality of first antennas capable of receiving a second frequency band are provided. Antenna switching for switching between the first antenna and the second antenna according to a voltage of a control signal and a second antenna and switching to one of the plurality of second antennas according to the voltage of the control signal And a vehicle-mounted antenna device having a circuit,
Selection of outputting a control signal having a voltage equal to or higher than a predetermined threshold when the first frequency band is selected and lower than the predetermined threshold when the second frequency band is selected to the antenna switching circuit. With means,
The antenna switching circuit switches to the first antenna when the control signal has a voltage equal to or higher than the predetermined threshold, and switches the plurality of antennas according to the voltage when the control signal has a voltage lower than the predetermined threshold. Is switched to one of the second antennas.
[0016]
Further, at least one or more first antennas capable of receiving the first frequency band, a plurality of second antennas capable of receiving the second frequency band, and the first antenna depending on a voltage of a control signal. An antenna switching circuit that switches between an antenna and a second antenna and switches to one of the plurality of second antennas according to a voltage of a control signal, and demodulates a received signal input through the antenna switching circuit An in-vehicle antenna device having a selection unit that generates the control signal based on the demodulated signal and outputs the control signal to the antenna switching circuit,
The selecting means keeps the demodulated voltage when the second frequency band is selected, and is higher than when the second frequency band is selected when the first frequency band is selected. Selecting means for outputting to the antenna switching circuit a control signal that is a voltage equal to or higher than a predetermined threshold value that has increased the demodulated voltage to be a voltage,
The antenna switching circuit switches to the first antenna when the control signal has a voltage equal to or higher than the predetermined threshold, and switches the plurality of antennas according to the voltage when the control signal has a voltage lower than the predetermined threshold. Is switched to one of the second antennas.
[0017]
Further, the first frequency band is a band in which FM broadcasting can be received, and the second frequency band is a band in which TV broadcasting can be received.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a block diagram showing a configuration of a main part of the vehicle-mounted antenna device according to the embodiment. Parts having functions common to those of the related art will be described with the same reference numerals.
[0020]
In FIG. 1, when TV reception is selected by a switch (not shown) provided in the FM / TV receiver (3), the antenna switching circuit (1) switches the TV antenna elements (2b to 2d) at predetermined time intervals. Each is turned on for a predetermined time, and each received signal is output to the FM / TV receiver (3) via the cable (4).
[0021]
The FM / TV receiver (3) extracts a video signal or an audio signal based on the reception signal input from each antenna element in the same manner as the above-described method. The FM / TV receiver (3) outputs the extracted video signal to the antenna switching circuit (1) via the image signal cable (57). The antenna switching circuit (1) selects an antenna element from which a video signal having the highest voltage value is obtained from an input video signal.
[0022]
Next, when FM reception is selected by a switch (not shown) provided in the FM / TV receiver (3), the FM / TV receiver (3) transmits a signal having a higher voltage value than the video signal to the image signal cable. The signal is output to the antenna switching circuit (1) via (57).
[0023]
The antenna switching circuit (1) is provided with a threshold value regarding the voltage value of the video signal input via the video signal cable (57). The antenna element (2a) for TV is selected, and if it is equal to or less than a predetermined value, the TV antenna elements (2b to 2d) are turned on for a predetermined time at predetermined time intervals, and the received signals are transmitted to the FM / TV receiver (3). Output.
[0024]
In the above-described embodiment, the TV antenna elements (2b to 2d) are turned on for a predetermined time at predetermined time intervals, and the respective reception signals are output to the FM / TV receiver (3). When the voltage value of the video signal generated by the received signal received by the antenna element is lower than a predetermined value, the TV antenna elements (2b to 2d) are turned on for a predetermined time, and the respective reception signals are FM / You may make it output to a TV receiver (3).
[0025]
In the above-described embodiment, the case where one FM antenna element and three TV antenna elements have been described, but the number of each antenna is not limited to this, and the FM antenna element and the TV And a plurality of antenna elements for each.
[0026]
In this case, switching of the plurality of FM antenna elements uses an audio signal generated from a reception signal received by the FM antenna element. For example, an audio signal generated from a reception signal received by the plurality of FM antenna elements is used. The offset voltage may be applied so that the minimum value of the voltage value is larger than the maximum value of the voltage of the video signal generated from the received signal received by the TV antenna.
[0027]
【The invention's effect】
According to the present invention, the switching between the FM antenna and the TV antenna and the switching to the antenna having the highest reception sensitivity among the same type of antennas can be performed with one cable, so that the cable can be easily attached and Cable costs can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a main part of a vehicle-mounted antenna device of the present invention.
FIG. 2 is a block diagram showing a first configuration of a conventional vehicle-mounted antenna device.
FIG. 3 is a block diagram showing a second configuration of the conventional vehicle-mounted antenna device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Antenna switching circuit 2a FM antenna element 2b, 2c, 2d TV antenna element 3 FM / TV receiver 4 Cable 57 Video signal cable

Claims (3)

At least one or more first antennas capable of receiving a first frequency band, a plurality of second antennas capable of receiving a second frequency band, and the first antenna according to a voltage of a control signal; An antenna switching circuit that performs switching of the second antenna and switches to one of the plurality of second antennas according to the voltage of the control signal;
Selection of outputting a control signal having a voltage equal to or higher than a predetermined threshold when the first frequency band is selected and lower than the predetermined threshold when the second frequency band is selected to the antenna switching circuit. With means,
The antenna switching circuit switches to the first antenna when the control signal has a voltage equal to or higher than the predetermined threshold, and switches the plurality of antennas according to the voltage when the control signal has a voltage lower than the predetermined threshold. An on-vehicle antenna device characterized by switching to one of the second antennas. At least one or more first antennas capable of receiving a first frequency band, a plurality of second antennas capable of receiving a second frequency band, and the first antenna according to a voltage of a control signal; An antenna switching circuit for switching the second antenna and switching to one of the plurality of second antennas according to the voltage of the control signal; and demodulating and demodulating a received signal input via the antenna switching circuit. An in-vehicle antenna device having a selection unit that generates the control signal based on the signal and outputs the control signal to the antenna switching circuit,
The selecting means keeps the demodulated voltage when the second frequency band is selected, and is higher than when the second frequency band is selected when the first frequency band is selected. Selecting means for outputting to the antenna switching circuit a control signal that is a voltage equal to or higher than a predetermined threshold value that has increased the demodulated voltage to be a voltage,
The antenna switching circuit switches to the first antenna when the control signal has a voltage equal to or higher than the predetermined threshold, and switches the plurality of antennas according to the voltage when the control signal has a voltage lower than the predetermined threshold. An on-vehicle antenna device characterized by switching to one of the second antennas. The in-vehicle antenna device according to claim 1, wherein the first frequency band is a band in which FM broadcasting can be received, and the second frequency band is a band in which TV broadcasting can be received.

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