JPH0611673Y2 - Car receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an automobile receiving device capable of obtaining a received signal in a wide range of frequency bands with optimum sensitivity under various conditions.

[Outline of device]

A plurality of auxiliary coils that can be connected to the ground in the signal path of the antenna are switched by the change-over switch means so that the resonance point of the inductance element that resonates in parallel with the ground stray capacitance of the antenna can be varied, and a damper is provided for each auxiliary coil. This is a vehicle receiver in which a resistor is connected to reduce a gain reduction caused by routing of a feeder cable over a wide reception frequency band.

[Conventional technology]

A heater conductor for defrosting is attached to a window glass of an automobile (particularly a rear window glass) by printing or embedding. It is known to use this heater conductor as part of an antenna or antenna element for the AM broadcast band, for example.

FIG. 8 is a conductor pattern diagram of such a window glass antenna, showing a large number of heater wires 2 in the defrosted area of the rear window glass 1.
Is attached to the heater wire 2, and the heater wires 2 are divided into upper and lower groups. The heater wires 2 are connected to one end through the power supply buses 3 and 4 and are fed back via the relay bus 5 at the other end. In order to use the heater wire 2 as a receiving antenna for AM broadcasting, a feeder 7a such as a coaxial wire is connected to the feeding point 6 provided on the relay bus 5, and the received signal is supplied to the preamplifier 9 through the DC cut capacitor 8. Then, the amplifier output is led to the tuner through the impedance correction capacitor 10 through the coaxial feeder cable 7b.

The heating current is magnetically coupled to the choke coil 11a,
11b through the power supply lines 12 and 13, and the power supply bus lines 3 and 4
Be washed away. Choke coil 11a connected to main power supply + B
And the choke coil 11b connected to the ground point are negatively coupled, and the magnetic fluxes due to the respective heating currents are canceled in the core, so that the small volume core can be operated in a non-saturated state. With respect to the received high frequency, the choke coils 11a and 11b exhibit high impedance, and the received signal induced in the heater wire 2 does not escape to the low impedance power source or the ground, so that the receiving efficiency is improved. A decoupling capacitor 14 is coupled to the line connected to the main power source + B to prevent power source noise from being included in the received signal.

9 is an equivalent circuit of the antenna of FIG. 8, where e ₀ is the induced electromotive force of the heater wire 2, C ₁ is the effective capacitance of the antenna,
C ₂ is the reactive capacitance of the antenna, C _L is the stray capacitance of the feeder lines 12 and 13, L _X is the equivalent inductance of the choke coils 11a and 11b (1/2 of the inductance of each coil).
Considerable), C _d is the self-capacitance of the choke coil, C _c is the capacitance of the DC cut capacitor 8, the C _k feeder cable 7
The stray capacitance of b and C _s are the capacitance of the correction capacitor 10. The output from the correction capacitor 10 is supplied to the front end of the receiver including a tuning circuit generally called a μ-tuner which is composed of a parallel circuit (tank circuit) of a variable capacitor 15 and a variable inductance 16.

[Problems to be solved by the invention]

The correction capacitor 10 shown in FIGS. 8 and 9 has a predetermined value (80 pF) for the capacitance on the antenna side as seen from the input of the receiver.
It is inserted to match with. The capacity on the antenna side is 8
If it deviates from 0 pF, the tuning point of the LC tank circuit of the receiver designed to connect the antenna having this capacitance is deviated, and the tracking error (IF frequency deviation) increases and the reception gain decreases. To do.

Further, since the correction capacitor 10 is inserted in series with the tuner input, it becomes a factor of attenuation of the reception gain. For this reason, the preamplifier 9 must be inserted before the correction capacitor 10. However, since the preamplifier 9 has non-linearity in the large amplitude range and has a limited dynamic range,
When a strong electric field is applied, interference due to intermodulation distortion increases and clipping may occur. In addition to the cost increase, the preamplifier 9 is provided on the rear window glass 1 side, which causes problems in arrangement space and power supply of the operating power supply.

In view of this problem, the present invention has an object to prevent the reception gain from being reduced over a wide range of frequencies even if the preamplifier 9 is removed.

[Means for solving problems]

The vehicle receiver of the present invention includes an inductance element that resonates in parallel with the floating capacitance to the ground of the antenna when the antenna side is viewed from the input end of the tuner. The inductance element includes a plurality of auxiliary coils that can be connected to the ground in a signal path from the output end of the antenna to the input end of the tuner, and a damping resistance connected in parallel or in series to each auxiliary coil. . These auxiliary coils are switched by the changeover switch means according to the reception band changeover signal to change the resonance point of the inductance element.

[Action]

By switching the auxiliary coil with a switch, the parallel resonance point can be changed, and the ground impedance of the antenna viewed from the tuner can be increased for each reception band, and signal loss is reduced over a wide range of reception frequencies, and power reception efficiency is improved. Increase. Further, even if an inexpensive high-capacity cable is routed from the antenna to the tuner and connected, signal attenuation is suppressed, and a decrease in reception sensitivity can be compensated. Further, by connecting a damping resistor to each auxiliary coil, the peak of the reception sensitivity characteristic curve becomes gentle, the sensitivity difference when the auxiliary coil is switched becomes small, and a wider band reception characteristic can be obtained.

〔Example〕

FIG. 1 shows an antenna device for explaining the principle of the present invention, and FIG. 2 shows an example of its equivalent circuit. The conductor pattern of the rear window glass 1 and the feeding circuit for the heating current are the eighth
It is the same as the figure. In FIG. 1, instead of a conventional μ tuner having an LC tank circuit at the front end (antenna input stage), a presettable electronic tuner 20 including a variable capacitance element such as a variable capacitance diode in a tuning circuit is provided.
(Called a varactor tuner). Since this tuner 20 does not have a tank circuit at the antenna input stage, the correction capacitor 10 shown in FIG. 8 is unnecessary, and therefore the loss due to this capacitor 10 is eliminated.
The preamplifier 9 is also unnecessary. The reduction in loss due to the removal of the correction capacitor 10 is 2 to 4 dB.

Since the DC cut capacitor 8 is necessary, the capacitor 8 is directly or indirectly coupled to the feeding point 6 provided on the relay bus 5, and then the received signal is derived to the electronic tuner 20 via the feeder cable 7, or A capacitor 8 is provided at the input end of the electronic tuner 20.

If the preamplifier 9 is removed, the problem is that the sensitivity is lowered in the weak electric field. The sensitivity is lowered because the stray capacitance of the feeder cable 7, the stray capacitance C _L of the feeder lines 3 and 4 and the self-capacitance C _d of the choke coils 11a and 11b shown in FIG. 2 are ineffective capacitances that cause signal loss. .

FIG. 3 is a graph showing the amount of attenuation of the feeder cable 7 (circulation length 4 m) to the input end 21 (point B) of the electronic tuner 20 with reference to the feeding point 6 (point A) on the side of the window glass 1.
The cable 7 has a unit stray capacitance of 46 pF / m and 23
Those of pF / m are compared. As is clear from this graph, the smaller the stray capacitance, the less the reactive loss and the less the attenuation. However, low capacity cables are expensive.

Therefore, by selecting the equivalent inductance L _x of the choke coils 11a and 11b and causing them to resonate in parallel with the reactive capacitance, the impedance of the antenna viewed from the input end 21 of the electronic tuner 20 can be increased to prevent a decrease in reception sensitivity. Conceivable. The optimum value of L _x is 30 to 500 μH, which is about half of the equivalent inductance of the conventional choke coil for μ tuner of 0.5 to 1 mH under various conditions.

Next, FIG. 4 shows another example of an equivalent circuit of an antenna similar to that shown in FIG. In this example, the choke coils 11a and 11b
The auxiliary coil 22 is added without changing the inductance value, and the inductance L _a causes parallel resonance with the reactive capacitance. As shown by the dotted line in FIG. 1, the auxiliary coil 22 can be inserted between the signal output terminal and the grounding point in the vicinity of the feeding point 6 of the window glass antenna in parallel with the reactive capacitance. . Alternatively, as shown by a dotted line 22 ′, it may be provided on the side of the input end 21 of the electronic tuner 20 or inside the electronic tuner 20.

Although the sensitivity can be increased by inserting the auxiliary coil 22, there is also an advantage that the constant values for the conventional μ tuner can be used as the choke coils 11a and 11b. That is, for a vehicle type that does not use the expensive preset type electronic tuner 20. The auxiliary coil 22 may be removed and the correction capacitor 10 and the amplifier 9 may be used as shown in FIG. If the auxiliary coil 22 is provided inside the electronic tuner 20, it is convenient because the auxiliary coil 22 is inserted into the antenna system only by converting the μ tuner into the electronic tuner.

FIG. 5 is a graph showing the receiving sensitivity when the inductance value L _a of the auxiliary coil is changed, and it can be seen that a value of about 60 to 100 μ can obtain the effect of sensitivity enhancement by parallel resonance. In this graph, the reception gain when the auxiliary coil 22 is not provided is used as a reference (0 dB).

When the auxiliary coil 22 is tuned as shown in FIG. 5, the peak value Q is large and the band becomes too narrow. In this case, the problem can be solved by inserting a damping resistor in series or in parallel with the auxiliary coil 22. FIG. 6 is a graph showing a change in receiving sensitivity when the series damping resistor 23 or the parallel damping resistor 24 is provided in the auxiliary coil 22 of 100 μH.
It can be seen that a relatively good wide band characteristic can be obtained with 230Ω (series) and 100 μH // 1KΩ (parallel).

FIG. 7 shows an embodiment of a circuit diagram of a main part of the present invention of a constant switching type in which the reception frequency band is divided into two. As described above, a relatively good wide band characteristic can be obtained by using the auxiliary coil, but the present invention selectively switches the auxiliary coil by a switch in order to obtain the effect of sensitivity enhancement due to parallel resonance over the entire band. The inductance value can be varied by grounding to. In this embodiment, as shown in FIG. 7, two auxiliary coils are used, and the auxiliary coil L ₁ resonates with the reactive capacitance in the high range, and the auxiliary coils L ₁ and L in the low range.
It is configured to resonate with the parallel inductance of ₂ . In the high range of the coil L ₁ and the series of damping resistor R ₁ acts, the diode D is a coil L ₂ in series with the change-over switch means is off, one end of the coil L ₂ is in a high impedance. DC voltage + on the anode of diode D
When B is supplied as a reception band switching signal and turned on, the circuit of the coil L ₂ and the damping resistor R ₂ is activated, and resonance occurs due to the parallel inductance value of L ₁ and L ₂ as a whole, and the resonance frequency decreases. To do. The reception band switching signal can be supplied from the tuner side in response to the tuner selection operation.

The receiving device according to the present invention is not limited to the above embodiment, and the number of auxiliary coils to be used and the switching method can be appropriately selected according to the frequency band to be received. Further, it can be applied to automobile antennas such as pillar antennas and pole antennas other than window glass antennas.

[Effect of device]

According to the present invention, as described above, the constant of the inductance element that resonates in parallel with the ground capacitance of the antenna when the antenna side is viewed from the input terminal of the tuner is configured to be switchable according to the reception band, and a plurality of inductance elements are configured. Since a damping resistor is connected to the auxiliary coil of, the peak of the receiving sensitivity characteristic curve can be smoothed for each receiving band to reduce the difference in receiving sensitivity due to frequency, and therefore the parallel resonance inductance of the antenna can be set in the receiving band. Along with the fact that it is configured to be changed accordingly, high gain and flat reception sensitivity characteristics can be obtained over a very wide band.

[Brief description of drawings]

FIG. 1 is a wiring diagram of a rear window glass antenna of an automobile shown as an example for explaining the principle of the present invention, and FIG.
FIG. 3 is an equivalent circuit diagram of the wiring shown in the figure, FIG. 3 is a graph showing changes in receiving sensitivity when the feeder cable is changed, and FIG. 4 is an equivalent circuit showing an example different from the equivalent circuit shown in FIG. 5 and 5 are graphs showing the change in sensitivity when the auxiliary coil is changed, FIG. 6 is a graph showing the change in sensitivity when a damping resistor is added, and FIG. 7 is a main circuit of the present invention in which the inductance is switched. It is a principal part circuit diagram which shows one Example. FIG. 8 is a wiring diagram of a conventional window glass antenna, and FIG. 9 is an equivalent circuit diagram. In the reference numerals used in the drawings, 1 ... rear window glass 2 ... heater wire 3, 4 ... feeding busbar 5 ... relay busbar 6 ... feeding point 7 ... feeder cable 11a, 11b ... choke coil 12 , 13 ...... feed line 20 ...... electronic tuner 22 ...... auxiliary coil D ...... diode (switch) R ₁ is ...... damping resistor R ₂ ...... damping resistor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Iijima 4-8 Doshomachi, Higashi-ku, Osaka City, Osaka Prefecture Nihon Sheet Glass Co., Ltd. (56) Reference JP-A-54-89512 (JP, A) JP-A-SHO 55-110438 (JP, A) JP-A-63-146521 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. An inductance element is provided which resonates in parallel with a ground stray capacitance of the antenna when the antenna side is viewed from the input end of the tuner, and the inductance element extends from the output end of the antenna to the input end of the tuner. A plurality of auxiliary coils that can be connected to the ground in a signal path between them, and a damping resistor that is connected in parallel or in series to each auxiliary coil are provided, and these auxiliary coils are switched according to the reception band switching signal to switch the inductance element. An automobile receiver comprising changeover switch means for varying a resonance point.