JPH0630347A - On-vehicle tv antenna system - Google Patents

Abstract

PURPOSE:To provide the system not disturbed by distortion in a picture signal and an audio signal caused in a strong electric field area and an FM broadcast signal other than a TV band or the like. CONSTITUTION:The system is provided with antennas 11-14 receiving a television broadcast to output signals S1-S4, impedance matching modules 17-20 connected to the antennas 11-14, and a diversity circuit applying an optimum signal outputted from the impedance matching modules 17-20 to a TV 16, and each of the impedance matching modules 17-20 is provided with RF switches 21-23 whose any of plural output terminals is conductive in response to a band switching signal BS generated from the TV 16 and outputting a signal S1 from the output terminal and with plural impedance matching circuits 24-26 connecting respectively to the plural output terminals to provide the matching of the impedance between the antennas 11-14 and the TV 16 and selecting a frequency for the signals S1-S4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile TV antenna device for diversity receiving television broadcasting.

[0002]

2. Description of the Related Art As a conventional automobile TV antenna device, as shown in FIG. 1, four antennas 11, 12, 1 for receiving a television broadcast are provided on a rear glass 10 of the automobile.
There are those in which 3, 14 are arranged. Reference numeral 15 is a heater wire.

Television signals received by the antennas 11 to 14 are supplied to the TV amplifier 7, respectively. TV amplifier 7 with built-in non-linear amplification element such as transistor
Performs amplification processing on each of the four television signals and amplifies and outputs the four television signals to a level sufficient for the diversity unit 8 to process. The diversity unit 8 selects, for example, one of the four television signals having the highest signal-to-noise ratio level and supplies it to the TV 16. Therefore, the TV 16
Of the four television signals, the television signal in the best reception state is always supplied.

[0004]

However, in the above-described automobile TV antenna apparatus, not only distortion occurs due to the non-linearity of the non-linear amplification element used in the amplification circuit in the TV amplifier 7, but also a strong electric field area is generated. When an electromagnetic force acts on the non-linear amplification element from the outside, the operating point of the non-linear amplification element may move to cause distortion more than previously assumed in the image signal and the audio signal.

Further, since the TV amplifier 7 does not have a frequency selection function, radio waves other than the TV band, such as FM broadcast signals, are directly input to the TV 16, which may interfere with reception of television signals. is there.

In order to solve the above-mentioned problems, the present invention provides a distortion of an image signal and an audio signal generated in a high electric field area, and T.
It is an object of the present invention to provide a TV antenna device for an automobile that is not disturbed by FM broadcast signals other than the V band.

[0007]

In order to achieve the above object, an automobile TV antenna apparatus of the present invention is an antenna for receiving a television broadcast and outputting a television signal, and a band generated by a TV. According to the switching signal, any one of the plurality of output terminals to conduct, a changeover switch for outputting the television signal from the output terminal,
A plurality of impedance matching circuits are provided, which are connected to the plurality of output terminals, respectively, to provide impedance matching between the antenna and the TV, and to select a frequency for the television signal. .

Also, a plurality of antennas each receiving a television broadcast and outputting a television signal, a plurality of impedance matching modules connected to the respective antennas, and a plurality of impedance matching modules output from the plurality of impedance matching modules. The best TV signal is the TV
The impedance matching module supplies each of the plurality of output terminals to be conductive according to a band switching signal generated by the TV, and the impedance matching module supplies each of the output terminals with the diversity circuit. A plurality of change-over switches for outputting a television signal and a plurality of output terminals are connected to each other to provide impedance matching between the antenna and the TV and to select a frequency for the television signal. The TV antenna device for an automobile may be configured to have an impedance matching circuit.

Further, as the configuration of the impedance matching circuit used in the automobile antenna device according to the first and second aspects, the following three configurations are effective. The impedance matching circuit is configured by connecting the cathodes of the first and second variable capacitance diodes and connecting the anodes of these first and second variable capacitance diodes through the first coil. The variable capacitance resonance circuit of
A second variable capacitance resonance circuit configured by connecting the cathodes of the fourth variable capacitance diodes and connecting the anodes of these third and fourth variable capacitance diodes through the second coil; Frequency selection is performed by applying a tuning voltage to the cathodes of the first and second variable capacitance diodes and the cathodes of the third and fourth variable capacitance diodes.

Further, the impedance matching circuit includes a third variable capacitance resonance circuit formed by connecting a third coil in parallel with a fifth variable capacitance diode and a sixth variable capacitance diode. And a fourth variable capacitance resonance circuit formed by connecting a fourth coil in parallel with each other, and frequency selection is performed by applying a tuning voltage to the cathodes of the fifth and sixth variable capacitance diodes. May be performed. Furthermore, the impedance matching circuit includes a fifth variable capacitance resonance circuit having a seventh variable capacitance diode and a fifth coil, and a sixth variable capacitance having an eighth variable capacitance diode and a sixth coil. A resonance circuit, a seventh variable capacitance resonance circuit including a ninth variable capacitance diode and a seventh coil, and a capacitor connecting the seventh variable capacitance resonance circuit and the sixth variable capacitance resonance circuit. The frequency selection may be performed by applying a tuning voltage to the cathodes of the seventh, eighth, and ninth variable capacitance diodes.

[0011]

According to the first aspect of the present invention, it is difficult for the impedance matching circuit to have a frequency selection function or the like over the entire frequency band of the television signal due to its configuration. , And impedance matching circuits for that number are prepared,
Each constant constituting each impedance matching circuit is set corresponding to the frequency band processed by the matching circuit. Each output terminal of the changeover switch is connected to the impedance matching circuit. When any one of the plurality of output terminals is turned on in response to the band switching signal generated from the TV, the television signal is supplied to the impedance matching circuit via the output terminal. The impedance matching circuit has frequency selectivity and allows the television signal of the selected frequency to pass through with almost no loss, but causes impedance loss at other frequencies.

According to the second aspect, when the plurality of impedance matching modules and the diversity circuit are provided, the television signals of the selected frequency are supplied to the diversity circuit as many as the impedance matching modules. The number of impedance matching modules is set so that the number of antennas is the same or smaller than the number of antennas.
The diversity circuit selects the optimum one of the input television signals and supplies it to the TV.

Further, when the impedance matching circuit according to claims 1 and 2 is the matching circuit according to claim 3, the cathodes of the first and second variable capacitance diodes and the third and fourth variable capacitors are provided. By applying the tuning voltage to the cathode of the capacitance diode, the first and second variable capacitance resonance circuits select television signals of the same frequency. This matching circuit cancels the reactance component of the antenna and the reactance component of the TV, and converts the impedance on the antenna side and the impedance on the TV side.

Also, the third to seventh aspects of the present invention are set forth.
The variable capacitance resonance circuit of is similar to claim 3 in that the frequency is selected for each, but the capacitor connecting the seventh variable capacitance resonance circuit and the fifth variable capacitance resonance circuit is the ninth variation. By cutting the tuning voltage (DC voltage) for reverse biasing the variable capacitance diode, the tuning voltage is arranged to prevent forward biasing of the eighth variable capacitance diode. On the other hand, the tuning voltage is also applied to the cathodes of the seventh and eighth variable capacitance diodes. Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the same parts as those of the conventional example shown in FIG.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 2, four antennas 11, 12, 13, 14 are arranged on a rear glass 10, and the antennas 11 to 14 belong to all TV bands of VHF band and UHF band, respectively. In addition to the signals, the television signals S ₁ , S ₂ , S ₃ , S ₄ including FM broadcast signals are output. Signal S ₁ output from antennas 11-14
~ S ₄ are impedance matching modules 17,
It is supplied to 18, 19, 20. The impedance matching module 17 includes three RF switches 21, 22, 23 that receive the signal S ₁ via the input terminal 33 and impedance matching circuits 24, 25 connected to the output terminals of these RF switches 21-23. , 26.

The impedance matching circuit 24 is VHF.
-H, and the impedance matching circuit 25 is VHF-
The impedance matching circuit 26 is for L, and the impedance matching circuit 26 is for UHF. The capacitors 27, 28 and 29 also serve as a direct current cutoff and a part of each matching circuit 24 to 26, and are shown separately from each matching circuit in FIG. 2 for convenience of description. The capacitor 27 takes out the frequency-selected television signal from the output terminals of the matching circuits 24 to 26 and applies the tuning voltage V _s (DC voltage) to the control terminals of the matching circuits 24 to 26. Impedance matching module 18,
19 and 20 have the same structure as the impedance matching module 17. The diversity circuit 31 selects, for example, the television signal having the highest SN ratio level from the television signals supplied from the impedance matching modules 17 to 20, and supplies it to the TV 16.

The RF switches 21 to 23 are constructed, for example, as shown in FIG. PIN diodes 34, which are the main components of the RF switches 21, 22, and 23,
Bias resistors 38, 39, 40 are connected to 35, 36, and capacitors 42, 43, 4 are connected through the connection points.
One of the electrodes 4 is connected. Capacitors 42-4
The other electrode of 4 is connected to the impedance matching circuits 24, 25, 26 via output terminals 46, 47, 48. The input terminals 33 that receive the television signal S ₁ from the antenna 11 via the capacitor 49 are provided on the input sides of the PIN diodes 34 to 36. In addition, the capacitor 49 and the PIN diodes 34 to 3
A ground resistor 51 is provided between the terminals 6. As described above, the frequency band of the television signal is divided into three by using the RF switches 21 to 23 because the entire frequency band of the television signal is 90M from the VHF band to the UHF band.
Hz to 770MHz, VHF band and UHF
There is a space of several hundred MHz of television signal between the bands, and several tens of MHz between the VHF-H band and the VHF-L band.
Because there is a blank of, it is the most reasonable to split as above. As a result, accurate processing can be performed for each of the divided frequency bands.

A band switching signal B _s (DC voltage) generated from the TV 16 in response to a channel operation is alternatively supplied to the RF switches 21-23. In the band switching signal B _s , the frequency band to which the frequency of the channel belongs is V
If it is in the HF-H band, it is supplied to the PIN diode 34,
In the VHF-L band, it is supplied to the PIN diode 35, and in the UHF band, it is supplied to the PIN diode 36. Each of the PIN diodes 34 to 36 has a band switching signal B
_{When s} is supplied, it becomes conductive. The tuning voltage V _s can also be used as the band switching signal B _s . In that case, the lines drawn from the wiring for the corresponding band switching signal B _s are connected to the control terminals of the matching circuits 24 to 26, respectively. Even when the lowest level tuning voltage is applied, the PIN diode 34 to
The constants for each element need to be set so that 36 can switch to the conducting state.

The impedance matching circuit 24 for VHF-H has a structure as shown in FIG. 4, for example.
The input terminal 52 is connected to the output terminal 46 of the RF switch, and the output terminal 53 is connected to the diversity circuit 31. The output terminal 53 is an output terminal for a television signal of a specific frequency selected by the impedance matching circuit 24. The tuning voltage V _s is applied to the control terminal 55. A first coil 56, a capacitor 57, and first and second variable capacitance diodes 58 and 59 are connected to the input terminal 52 via a capacitor 54. The variable capacitance diodes 58, 59, the coil 56, and the capacitors 54, 57 constitute a first variable capacitance resonance circuit 61.

Like the first variable capacitance resonance circuit 61, the second
Coil 62, capacitors 27, 63, and second and third
A second variable capacitance resonance circuit 67 composed of the variable capacitance diodes 64 and 65 is connected to the right side of the variable capacitance resonance circuit 61. The variable capacitance resonance circuit 61 and the variable capacitance resonance circuit 67 are set to have the same resonance frequency. The cathodes of the variable capacitance diodes 58 and 59 are connected to the control terminal 55 via the resistor 68. Similarly, the cathodes of the variable capacitance diodes 64 and 65 are connected to the control terminal 55 via the resistor 71. The resistor 68 connected to the variable capacitance resonance circuit 61 is a variable capacitance diode 5
The resistor 71 is provided to give a predetermined bias to 8, 59, and the resistor 71 is provided to give a predetermined bias to the variable capacitance diodes 64, 65.
Further, the variable capacitance resonance circuit 61 includes a capacitor 72 and a resistor 7
It is grounded through 3. When the two variable capacitance diodes 64 and 65 are connected in the opposite directions in this way, noise can be reduced, which is preferable.

The matching circuit 24 including the variable capacitance resonance circuits 61 and 67 cancels the reactance component of the antenna 11 and the reactance component of the TV 16 and converts the impedances on the antenna 11 side and the TV 16 side. As a result, the television signal of the frequency selected by the tuning voltage V _s is output from the output terminal 53 with almost no impedance loss, but the television signal of other frequencies, the FM broadcast signal, etc. cause impedance loss.

The VHF-L and UHF impedance matching circuits 25 and 26 have the same structure as the impedance matching circuit 24. However, the constants of the respective elements are selected so as to match the frequencies of the VHF-L band and the UHF band, respectively. Impedance matching circuit 24 ~
Since no amplifying element is used for 26, it is possible to reduce this kind of distortion as compared with the conventional device without amplifying the distortion induced in the transmission system in the strong electric field area. Hereinafter, the operation of the present embodiment having the above-mentioned configuration will be described.

First, when the channel of the TV 16 is operated to select the television signal of the frequency f _X1 belonging to the VHF-H band, the band switching signal B generated from the TV 16 is selected.
_s makes the PIN diode 34 conductive. At this time, the other PIN diodes 35 and 36 receive the band switching signal B _s.
Is not supplied, the non-conduction state is maintained. Therefore, the signal S ₁ output from the antenna 11 is sent to the input terminal 52 of the impedance matching circuit 24 via the PIN diode 34 and the output terminal 46.

The bias capacitances of the variable capacitance diodes 58, 59 and 64, 65 of the impedance matching circuit 24 are changed by applying the tuning voltage V _s via the resistors 68, 71, respectively, so that the junction capacitance thereof is changed. Only the television signal of the frequency f _X1 which changes and is selected from the signals S ₁ is selected. This television signal is output from the output terminal 53 with almost no impedance loss, but impedance loss occurs with respect to television signals or FM broadcast signals of other frequencies. As a result, F other than TV band
The levels of M broadcast signals and the like are reduced, and the occurrence of interference by these signals can be suppressed. Similarly, only the television signal of frequency f _X1 is output from the impedance matching modules 18 to 20 without impedance loss and supplied to the diversity circuit 31.

The diversity circuit 31 supplied with the four television signals of the frequency f _X1 selects the television signal having the highest SN ratio among the four television signals and sends it to the TV 16. By this, T
The V16 can perform excellent reception with much less noise and distortion than in the past. It should be noted that compared to conventional devices
Since the amplifier 7 is not used, the diversity circuit 31
Although the level of the television signal supplied to is reduced as a whole, since the frequency selection is performed, the level difference between the television signal of the selected frequency f _{X1 and} the signals of other frequencies is significantly large. Therefore, diversity circuit 3
Processing within 1 is rather easy.

In the above, the frequency f belonging to the VHF-H band is
_When the television signal of _X1 is selected, but the television signal of the frequency belonging to the VHF-L band or the UHF band is selected, the PIN diode 35 or 36 is made conductive, and the other PIN diodes are made non-conductive. maintain. After that, good reception is performed in the same manner as described above.

As a modification of the matching circuit 24, the circuit configuration shown in FIG. 5 can be adopted. In FIG. 5, parts corresponding to those of the matching circuit of FIG. 4 are designated by the same reference numerals. Fifth
The variable capacitance diode 80, and the third coil 81 and the capacitor 54 connected in parallel to the variable capacitance diode 80 constitute a third variable capacitance resonance circuit 82. Further, the sixth variable capacitance diode 83 and the fourth coil 84 and the capacitor 27 connected in parallel to the sixth variable capacitance diode 83 constitute a fourth variable capacitance resonance circuit 86. When tuning voltage V _s is applied to the control terminal 55, the tuning voltage V _s resistance 89
Is applied to the cathodes of the varactor diodes 80 and 83 via the, and the varactor diodes 80 and 83 are reversely biased. The capacitors 91 and 92 are provided so that the tuning voltage V _s reverse biases the variable capacitance diodes 80 and 83. Further, a resistor 93 is provided to enable reverse bias to the variable capacitance diode 83.

As another modification of the matching circuit 24, the circuit configuration shown in FIG. 6 can be adopted. The fifth variable capacitance resonance circuit 95 includes a fifth coil 96, a seventh variable capacitance diode 97 and capacitors 54 and 111, and a sixth variable capacitance resonance circuit 98 includes an eighth variable capacitance diode 99 and a fifth variable capacitance resonance circuit 98. 6 coils 100 and capacitors 1
04, and the seventh variable capacitance resonance circuit 101 includes a ninth variable capacitance diode 102, a seventh coil 103, and a capacitor 27. Variable capacitance resonance circuit 1
01 and 98 are connected via a capacitor 104, and a ground capacitor 106 is provided at a connection point between the variable capacitance resonance circuits 98 and 95. Further, capacitors 107, 108 and 109 are provided to perform reverse bias on the variable capacitance diodes 97, 99 and 100. The variable capacitance resonance circuit 101 includes a ground capacitor 112.
Is provided. Although three matching circuits 24 to 26 are provided in one impedance matching module 17 in the above, the number of impedance matching circuits in one impedance matching module is reduced to two depending on the impedance of the TV antenna and the radio. The configuration can be simplified.

In the above embodiment, four antennas 11 are used.
However, the number of antennas may be two or more, and it is not necessary to limit the number to four. Furthermore, the variable capacitance diodes 58, 59, 64, 65 and the like may be replaced with other variable reactance elements that can be used in a circuit configuration that does not exhibit nonlinearity and amplification action.

The index for judging the quality of the television signal does not have to be limited to the above SN ratio, and various methods such as simply using the height of the signal level as a reference can be used. Further, in FIG. 2, since the wiring for transmitting the band switching signal B _s is drawn for each impedance matching module 17 to 20, 12 wirings drawn from the TV 16 for band switching are required. This can be reduced to three. As shown in FIG. 7, three wires are pulled out from the TV 16, and these three wires are branched into four near the impedance matching modules 17 to 20, and each of them corresponds to each impedance matching module 17 to 20. It is recommended to connect to the RF switch. As a result, the number of wirings pulled out from the TV 16 is 4 which is the sum of one cable for outputting the tuning voltage V _s and inputting a television signal and the three wirings for switching the band. It will be a book. When the diversity circuit 31 and the impedance matching modules 17 to 20 are arranged on or near the rear glass 10 and only the TV 16 is arranged in a place apart from the rear glass 10, wiring as shown in FIG. 7 is performed. Wiring can be greatly simplified by.

[0031]

As described above in detail, according to the present invention, since the impedance matching module is provided, the loss due to the mismatch between the input and output impedances of the transmission system between the antenna and the TV is eliminated. It is possible to prevent the occurrence, and it is possible to reduce the interference caused by the FM broadcast signal other than the television signal of the selected frequency. Moreover, since a TV amplifier is not used unlike the conventional device, there is no non-linear amplification element between the antenna and the TV. Therefore, no distortion is generated by the non-linear amplification element and the distortion induced in the strong electric field zone is not amplified, so that the influence of the distortion can be reduced as a whole. Further, when the diversity circuit is provided, the optimum one can be selected from the plurality of signals whose frequencies are selected by the impedance matching circuit and supplied to the TV.

[0032]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a conventional TV antenna device for an automobile.

FIG. 2 is a schematic view showing a TV antenna device for an automobile according to an embodiment of the present invention.

FIG. 3 is a diagram showing the RF switches 21 to 23 of the embodiment shown in FIG.
It is a circuit diagram which shows an example.

4 is a circuit diagram showing an example of an impedance matching circuit 24 of the embodiment shown in FIG.

FIG. 5 is a circuit diagram showing another impedance matching circuit of FIG.

FIG. 6 is a circuit diagram showing another impedance matching circuit of FIG.

FIG. 7 is a schematic explanatory diagram showing a wiring pattern for transmitting a band switching signal B _s .

[Explanation of symbols]

11-14 Antenna 16 TV 17-20 Impedance matching module 21-23 RF switch 24-26 Impedance matching circuit 31 Diversity circuit 46-48 Output terminal 56,62,81,84,96,100,103 Coil 58,59,64 , 65, 80, 83, 97, 99, 1
02 variable capacitance diode 61, 67, 82, 86, 95, 98, 101 variable capacitance resonance circuit 104 capacitors S _{1 to} S ₄ television signal B _s band switching signal

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hirofumi Natsume 6 Kitahara, Tsukuba, Ibaraki Prefecture Sumitomo Chemical Co., Ltd. In-house (72) Inventor Hitoshi Kakizawa 3-5-11 Doshumachi, Chuo-ku, Osaka City, Osaka Prefecture Japan Sheet Glass Co., Ltd. (72) Inventor Yuji Baba 3-5-11, Doshumachi, Chuo-ku, Osaka, Japan Japan Within Sheet Glass Co., Ltd.

Claims (5)

[Claims] 1. An antenna for receiving a television broadcast and outputting a television signal, and one of a plurality of output terminals is made conductive in accordance with a band switching signal generated by a TV, A selector switch for outputting the television signal from the output terminal and each of the plurality of output terminals are connected to each other to provide impedance matching between the antenna and the TV and to select a frequency for the television signal. A TV antenna device for an automobile, comprising: a plurality of impedance matching circuits for performing the above. 2. A plurality of antennas each receiving a television broadcast and outputting a television signal, a plurality of impedance matching modules connected to the respective antennas, and a plurality of impedance matching modules output from the plurality of impedance matching modules. A diversity circuit for supplying the most suitable television signal to the TV, each impedance matching module being any one of a plurality of output terminals according to a band switching signal generated by the TV. A change-over switch that makes one of them conductive and outputs the television signal from its output terminal, and is connected to each of the plurality of output terminals, the antenna and the TV.
And a plurality of impedance matching circuits for performing frequency selection with respect to the television signal, and a TV antenna device for an automobile. 3. The impedance matching circuit connects cathodes of first and second variable capacitance diodes,
The first variable capacitance resonance circuit configured by connecting the anodes of these first and second variable capacitance diodes through the first coil and the cathodes of the third and fourth variable capacitance diodes are connected. ,
A second variable capacitance resonance circuit configured by connecting the anodes of the third and fourth variable capacitance diodes through a second coil, and the cathodes of the first and second variable capacitance diodes. 3. The vehicle TV antenna apparatus according to claim 1 or 2, wherein frequency selection is performed by applying a tuning voltage to the cathodes of the third and fourth variable capacitance diodes. 4. The impedance matching circuit includes a third variable capacitance resonance circuit formed by connecting a third coil in parallel to a fifth variable capacitance diode, and a sixth variable capacitance diode. And a fourth variable capacitance resonance circuit formed by connecting a fourth coil in parallel to each other, and frequency selection is performed by applying a tuning voltage to the cathodes of the fifth and sixth variable capacitance diodes. The TV antenna device for an automobile according to claim 1 or 2, wherein 5. The impedance matching circuit includes a fifth variable capacitance resonance circuit having a seventh variable capacitance diode and a fifth coil, and a sixth variable capacitance resonance circuit having an eighth variable capacitance diode and a sixth coil. Variable capacitance resonance circuit, a seventh variable capacitance resonance circuit including a ninth variable capacitance diode and a seventh coil, and connecting the seventh variable capacitance resonance circuit and the sixth variable capacitance resonance circuit. 3. The vehicle according to claim 1, further comprising a capacitor for performing frequency selection by applying a tuning voltage to the cathodes of the seventh, eighth, and ninth variable capacitance diodes. TV antenna device.