JPH04298123A - Antenna system for automobile - Google Patents

Abstract

PURPOSE:To realize the glass antenna system in which intermodulation noise due to an FM broadcast radio wave invaded at the reception of an AM station in a district in which two FM broadcast radio waves or over with a large electric field intensity whose frequency difference is set within a frequency range of an AM broadcast are in existence. CONSTITUTION:The antenna system is provided with an FM dynamic matching circuit 14 and an AM dynamic matching circuit 15 connecting directly to an FM antenna 9 and an AM antenna 11 provided to a window glass 10 of an automobile, the outputs are superimposed and sent to a radio receiver via a transmission cable. Both the dynamic matching circuits have respectively a varactor diode and the varactor diode is controlled by a frequency selection signal sent from the radio receiver via a transmission cable. The FM dynamic matching circuit has a comparatively steep frequency selectivity and is in operation even at the reception of an AM broadcast signal, then the band of the FM radio wave causing intermodulation noise at the reception of the Am broadcast signal is substantially made narrow thereby reducing the intermodulation noise of the FM radio wave at the reception of the AM broadcast.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an FM antenna and an AM antenna provided on the window glass of an automobile, an FM dynamic matching circuit connected to each of these antennas, and an AM antenna.
The present invention relates to an automotive antenna device equipped with a dynamic matching circuit.

0002

[Prior Art] In a reception system using a conventional automobile window glass antenna device using a preamplifier, FIG.
As shown in FIG. 2, an FM preamplifier 3 is connected to an FM antenna 2 printed on a rear glass 1 of an automobile, and an AM preamplifier 5 is connected to a plurality of heater wires functioning as an AM antenna 4. These FM preamplifiers 3 and AM
The FM signal and AM signal from each output section of the preamplifier 5 are superimposed on each other, and this superimposed signal is guided to the car radio 7 via the transmission cable 6.

In such a conventional receiving system, the FM preamplifier 3 operates even when an AM station is being received. This FM preamplifier 3 has a wide frequency characteristic that covers the FM band, and does not have steep frequency selectivity for the radio waves you want to receive. moves, and if the difference in frequency between at least two FM broadcast waves is within the AM band, these FM radio waves cause intermodulation in the FM preamplifier 3 and the high frequency amplification section of the car radio 7, Undesired signals in the AM frequency band result.

0004

[Problems to be Solved by the Invention] Therefore, in the reception system using the conventional automobile antenna device with a preamplifier shown in FIG. 1, the field strength of radio waves transmitted from two or more FM broadcast stations is large, and If a car moves to an area where the frequency difference falls within the frequency range of the AM band, when receiving radio waves from an AM broadcast station, F
Intermodulation noise due to M radio waves is mixed.

[0005] In view of the above-mentioned problems, the present invention has been developed to provide two or more powerful FM broadcasts whose frequency difference falls within the frequency range of AM broadcasting.
It is an object of the present invention to provide an antenna device for an automobile that reduces intermodulation noise mixed in when receiving AM broadcasting in an area where broadcasting radio waves exist.

[0006]

[Means for Solving the Problems] In order to achieve the above object, an antenna device for an automobile according to the present invention includes an FM antenna and an AM antenna provided on a window glass of an automobile;
FM dynamic matching circuit connected to each of these antennas and A
M dynamic matching circuits, each of which includes at least one variable reactance element to which a DC frequency selection signal is applied from a car radio via a transmission cable.

Therefore, according to the present invention, while the AM dynamic matching circuit operates based on the AM frequency selection signal during AM broadcast reception, the FM dynamic matching circuit also operates at the same time. In the operating state, since it has frequency selection characteristics of FM signals, the frequency range of interfering FM waves that can cause intermodulation noise is limited, and it is possible to reduce intermodulation noise caused by FM radio waves when receiving AM broadcasts. can.

[0008]

Embodiment FIG. 2 shows an embodiment of an antenna device for an automobile according to the present invention. This antenna device is an FM antenna that also serves as an anti-fog heater wire attached to the rear window 10 of a car.
Antenna 11 and an inverted T attached to the top of the heater wire
FM antenna 9, an FM dynamic matching circuit 14 and an AM dynamic matching circuit 15 connected to the AM antenna and the FM antenna, respectively, and the outputs of these dynamic matching circuits are integrated and transmitted via a transmission cable 12. and is connected to the car radio 13. These FM dynamic matching circuit 14 and AM dynamic matching circuit 15 are attached to the rear glass 10 as an integrated dynamic matching circuit configured on a common substrate.

As shown in FIG. 3, the FM dynamic matching circuit 14 includes variable capacitance diodes 16 and 17 to which a DC frequency selection signal is applied from the car radio 13 via the transmission cable 12. 15 includes a variable capacitance diode 18 to which the frequency selection signal is applied.

The FM dynamic matching circuit 14 is T-shaped as shown in FIG. 3, and includes a capacitor 20 connected to the FM antenna 9 shown in FIG. 2 via an input terminal 19. The other end of this capacitor 20 is connected to a coil 21 and a capacitor 22, and the variable capacitance diode 16 is connected between the other ends of these coil 21 and capacitor 22 to form a first resonant circuit. The anode of the variable capacitance diode 16 is grounded via a resistor 23, and a capacitor 24 of, for example, 1 picofarad is connected between the anode and the cathode.

The other end of the coil 21 is connected to a capacitor 2.
5, and further connected to the second coil 26 and the cathode of the second variable capacitance diode 17. A capacitor 27 is connected between the other end of the second coil 26 and the anode of the variable capacitance diode 17 to form a second resonant circuit. This variable capacitance diode 1
The anode of 7 is connected to the capacitor 28 and the terminal 29 on the load side.
It is connected to the transmission cable 12 via. Further, a resistor 30 is connected between the load side terminal 29 and the other end of the second coil 26, and bypasses the capacitors 27 and 28.
The anode of the variable capacitance diode 17 is grounded via a resistor 31.

Therefore, the frequency selection signal applied to the load-side terminal 29 is supplied to the variable capacitance diodes 16 and 17 via the second coil 26. Further, between the anode and cathode of the variable capacitance diode 17, for example, 1
A picofarad capacitor 32 is connected in parallel.

On the other hand, the AM dynamic matching circuit 15 includes a capacitor 34 connected to the AM antenna 11 shown in FIG. 2 via an input terminal 33. The other end of this capacitor 34 is connected to a coil 35. The other end of this coil 35 is connected to a relatively large capacity capacitor 36 and a second coil 37.
The variable capacitance diode 18 is connected between the other ends of the capacitor 7 .

The anode of this variable capacitance diode 18 is grounded via a resistor 38. On the other hand, the cathode of the variable capacitance diode 18 is connected to the third coil 40 via a capacitor 39, and further connected to the load-side terminal 29 via a capacitor 41. In addition, a resistor 4 for applying a frequency selection signal to the variable capacitance diode 18 is connected between the cathode of the variable capacitance diode 18 and the terminal 29 on the load side.
2 is connected.

FIG. 4 shows an F constituting an integrated matching circuit which is a different embodiment from the AM/FM integrated matching circuit shown in FIG.
An M dynamic matching circuit 50 and an AM dynamic matching circuit 51 are shown. In FIG. 4, parts corresponding to those shown in FIG. 3 are given the same reference numerals. This FM dynamic matching circuit 50 differs from the FM dynamic matching circuit 14 shown in FIG. 3 in that the capacitors 24 and 32 are omitted.

Further, the AM dynamic matching circuit 51 is simplified compared to the AM dynamic matching circuit 15 shown in FIG. That is, capacitors 39 and 41 are omitted, their attachment points are shorted, and resistor 42 is omitted. Furthermore, a capacitor 43 of, for example, several picofarads is connected between the anode and cathode of the variable capacitance diode 18.
are connected in parallel. Therefore, a frequency selection signal is applied to the variable capacitance diode 18 via the coil 40.

In the embodiment shown in FIGS. 3 and 4, the value of capacitor 20 is 6 picofarads, the value of capacitors 22 and 27 is each 0.1 microfarads, and the value of capacitor 25 is 10 picofarads. , and the value of capacitor 28 may be 6 picofarads. The resistors 23, 30, 31, 38, and 42 may have a value of 100KΩ, but since the capacitance is adjusted by applying a reverse bias voltage to the variable capacitance diodes 16, 17, and 18, the resistors 23, 30, 31, 38, and 42 may have a value larger than 100KΩ. may also be used. The value of coils 21 and 26 may each be 200 nanoHenries. Variable capacitance diodes 16 and 17 are 1SV153
The variable capacitance diode 18 may have a model number of KV1.
450 model number.

The FM/AM shown in FIGS. 3 and 4
The integrated dynamic matching circuit is attached to the rear glass 10, and as shown in FIG. 2, its circuit constants are changed by a frequency selection signal from the car radio side. That is, the integrated matching circuit attached to the rear window is controlled by a frequency selection signal, ie, a tuning voltage, applied from the car radio side via the transmission cable 12.

This channel selection voltage is applied to both the AM dynamic matching circuit and the FM dynamic matching circuit, both when selecting an AM station or when selecting an FM station. Therefore, even when selecting an AM station, a voltage for controlling the AM dynamic matching circuit is applied to the FM dynamic matching circuit.

FIG. 5(a) shows an FM dynamic matching circuit 14,
50 indicates the frequency-gain characteristic when matching at a specific frequency f0 of the FM band. For comparison, the frequency-gain characteristics of the conventional receiving system with a preamplifier shown in FIG. 1 are also shown. AM according to the invention
The FM gain characteristic of the /FM integrated dynamic matching circuit has a relatively steep frequency selection characteristic, while the conventional receiving system with a preamplifier has a flat gain characteristic over the entire FM band.

Now, the matching frequency of the FM dynamic matching circuit at the AM station selection voltage when receiving a certain AM station is f0
Let fx and fy be two FM broadcast waves that interfere with the AM station being received. The matching frequency in the AM dynamic matching circuit at this time is fa. However, fa
= |fx−fy|. When using the integrated matching circuit according to the present invention, when fx and fy are far from f0 as shown in FIG. 5(b), both fx and fy are sufficiently attenuated when passing through the FM dynamic matching circuit. , intermodulation noise when receiving an AM station is also sufficiently reduced.

As shown in FIG. 5(c), fx and fy are
If it is close to 0, fx and f will change while passing through the FM dynamic matching circuit.
Since y is significantly attenuated, the intermodulation noise when receiving an AM station is therefore significantly reduced. That is, the AM/F according to the present invention
When an M-integrated matching circuit is used, when the frequencies of the FM jamming station pair fx and fy are far apart from f0, intermodulation noise is sufficiently reduced, and when they are close, intermodulation noise is considerably reduced. In any case, the FM dynamic matching circuit has relatively steep frequency selection characteristics with a peak at a specific FM frequency for a specific tuning voltage, and a nonlinear amplification element is used in the circuit. Therefore, intermodulation noise due to a pair of FM interfering stations is less likely to occur.

Furthermore, the matching frequency f0 of the FM dynamic matching circuit when a specific AM tuning voltage is applied by changing the circuit constants of the FM dynamic matching circuit or the AM dynamic matching circuit is shown in FIG.
By shifting to f1 shown in c), it is possible to avoid the states fx and fy shown in FIG. 5(c). Furthermore, in the embodiments shown in FIGS. 3 and 4, a common tuning voltage is applied to the FM dynamic matching circuit and the AM dynamic matching circuit, but as the tuning voltage increases, the FM dynamic matching frequency increases. By determining the circuit constants such that the AM dynamic matching frequency decreases and the AM dynamic matching frequency increases, the frequency change may be performed in ascending and descending order as the tuning voltage increases. That is, for example, when the tuning voltage is zero volts, the FM dynamic matching circuit matches at a frequency of 90 MHz, the AM dynamic matching circuit matches at a frequency of 535 KHz, and for example, when the tuning voltage is 10 volts,
The FM dynamic matching circuit may match at a frequency of 76 MHz, and the AM dynamic matching circuit may match at a frequency of 1605 KHz.

On the other hand, in the case of the conventional receiving system with an FM preamplifier shown in FIG. 1, the frequency characteristic of the amplification degree of the preamplifier is flat as shown in FIG. Not only is the FM signal not reduced anywhere within the range, but intermodulation occurs due to the nonlinearity of the preamplifier, resulting in larger intermodulation noise.

That is, according to the present invention, as shown in FIGS. 3 and 4, by providing the FM window glass antenna with a matching circuit that changes its circuit constant in accordance with the selected frequency, the FM station can Intermodulation noise can be reduced compared to the conventional receiving system shown in FIG.

The FM and AM dynamic matching circuits shown in FIGS. 3 and 4 are controlled by a common tuning voltage, but the FM dynamic matching circuit and AM dynamic matching circuit are controlled within each frequency band. The voltage ranges for matching may be different from each other. Variable capacitance diodes 16 and 17 are matched at frequencies in the FM band with a first voltage range of the frequency selection signal, while variable capacitance diode 18 is matched at frequencies in the AM band with a second voltage range of the frequency selection signal. The circuit constants may be determined as follows.

In this case, for example, the FM dynamic matching circuit is 0
~10.0 volts and matched at frequencies in the 76-90 MHz FM band, while the AM dynamic matching circuit
The model numbers of the capacitor and variable capacitance diode are set to match in the AM band frequency in the range of 0.1 to 20.0 volts. Therefore, in the AM dynamic matching circuit, 1
If a particular voltage in the range of 0.1 to 20.0 volts is applied, the FM dynamic matching circuit will be in a mismatched state in the FM band, and therefore the FM signal passing through this FM dynamic matching circuit will be Significantly attenuated. Further, the first voltage range and the second voltage range may partially overlap.

Although an unbalanced dynamic matching circuit is shown in FIGS. 3 and 4, it is clear that a balanced dynamic matching circuit can also be used. Therefore, the invention can be implemented not only in unbalanced antenna systems but also in balanced antenna systems.

6 and 7, a plurality of heater wires 11 printed on the rear glass 10 are used as an AM antenna that also serves as an FM sub-antenna, and an inverted T-shaped FM main antenna is placed on the rear glass 10 above the plurality of heater wires 11. 60 is shown.

The FM and AM received signals from the AM antenna 11 which also serves as an FM sub-antenna shown in FIG.
Although it is input to the AM integrated dynamic matching circuit 61, FIG.
The AM antenna that also serves as an FM sub-antenna shown in FIG.
The difference is that the AM signal is directly input to the AM dynamic matching circuit from the power supply bus 62.

[0031] Therefore, the AM attached to the rear glass
/FM integrated dynamic matching circuit 61 integrates two FM dynamic matching circuits for FM main antenna and FM sub antenna and one AM dynamic matching circuit, and one FM dynamic matching circuit The output of the AM dynamic matching circuit and the output of the AM dynamic matching circuit are superimposed and connected to a car radio via a 5P3-30BA transmission cable 65, for example. The output of the remaining FM dynamic matching circuit is, for example, a 1.5C-2V transmission cable 66.
It is connected to the car radio through. In this case, the matching circuit for the FM main antenna and the AM dynamic matching circuit may be the FM dynamic matching circuits 14, 15 and the AM dynamic matching circuits 15, 51 shown in FIGS. 3 and 4. The matching circuit for FM dynamic matching circuit 1 shown in FIGS. 3 and 4 is
4 and 15 may have an independent circuit configuration.

The FM sub/AM antenna shown in FIG. 6 also includes FM coils 67 and 6 of, for example, 1.6 microhenry directly connected to the feeding buses 62 and 63 in order to monotonically change the frequency characteristics of impedance in the FM band.
There are 8. The other ends of these FM coils 67 and 68 are connected to a choke coil 69, and a 12 volt DC voltage is supplied when defrosting the rear window.

[0033]

[Effects of the Invention] As explained above, the automotive antenna device of the present invention can be realized by using an unpress method in which a circuit that integrates an FM dynamic matching circuit and an AM dynamic matching circuit is attached to a glass antenna. The FM dynamic matching circuit operates even during AM broadcast reception, and its gain characteristics for FM radio waves have frequency selectivity, so the probability of reducing interfering FM radio waves is higher than that of a receiving system with an amplifier. In areas where there are two or more FM broadcast waves with large electric field strengths that fall within the AM broadcast frequency range,
This provides the advantage of being able to reduce intermodulation noise mixed in when receiving M stations.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a conventional automobile antenna device with a preamplifier.

FIG. 2 is a schematic diagram showing an embodiment of an automotive antenna device equipped with an FM and AM dynamic matching circuit according to the present invention.

FIG. 3 is a circuit diagram showing one embodiment of the FM and AM dynamic matching circuit shown in FIG. 2;

FIG. 4 is a circuit diagram showing another embodiment of the FM and AM dynamic matching circuit shown in FIG. 2;

5 is a frequency-gain characteristic diagram of the FM dynamic matching circuit according to the present invention shown in FIGS. 3 and 4 and the conventional preamplifier shown in FIG. 1; FIG.

FIG. 6 is a schematic diagram showing an embodiment of a windowpane antenna according to the present invention.

FIG. 7 is a schematic diagram showing another embodiment of a windowpane antenna according to the invention.

[Explanation of symbols]

10 Rear glass (window glass) 11
Antenna 12 Transmission cable 14 FM dynamic matching circuit 15 AM dynamic matching circuit 16 Variable capacitance diode 17 Variable capacitance diode 18 Variable capacitance diode

Claims (4)

[Claims] 1. An FM antenna and an AM antenna provided on a window glass of an automobile, and an FM dynamic matching circuit and an AM dynamic matching circuit respectively connected to these antennas, the FM dynamic matching circuit and the AM An antenna device for an automobile, wherein the dynamic matching circuit includes at least one variable reactance element, each of which receives a DC frequency selection signal from a car radio via a transmission cable. 2. The FM dynamic matching circuit is configured to match an FM antenna impedance and an impedance of a car radio load viewed through a transmission cable at a frequency in an FM band in the first voltage range of the DC frequency selection signal. wherein the AM dynamic matching circuit is configured to be able to control resonance of a system including an antenna capacitance and a transmission cable capacitance at a frequency in the AM band in a second voltage range. Item 1. An antenna device for an automobile according to item 1. 3. The automobile antenna device according to claim 1, wherein the FM dynamic matching circuit is a T-type dynamic matching circuit. 4. The automobile antenna device according to claim 1, wherein the variable reactance element is a variable capacitance diode.