JPH0658611U - Glass antenna feeder wire connection structure - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a connection structure for a glass antenna feeder line in which the reception sensitivity is reduced and the reception sensitivity is hardly changed in the FM frequency band. A structure for connecting a glass antenna feeder line for connecting a glass antenna provided on a window glass of an automobile and a radio receiver, wherein the signal line is composed of only a coaxial feed line 2, and the glass antenna side terminal is provided. In the connection structure of the glass antenna feeder wire, which is provided with the grounding means 4 for fixing the outer conductor 7 to the vehicle body and electrically connecting the outer conductor 7 to the vehicle body at a position apart from the portion by a predetermined distance, the coaxial feed line 2 is a glass antenna. The inner conductor 5 is connected to the feeder line terminal 12 via the coil 3 at the side terminal portion.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a connection structure of a glass antenna feeder line that connects a glass antenna provided on a window glass of an automobile and a radio receiver.

[0002]

[Prior art]

 As a conventional connection structure for a glass antenna feeder line, as shown in FIG. 4, the radio receiver side is a coaxial feeder line 101, and at the antenna side terminal part, a grounding means 102 is connected to the outer conductor, The internal conductor has a structure in which a lead wire (feeder single wire) 103 and an antenna terminal 106 provided on the glass 105 are connected via a feeder wire terminal 104, or as shown in FIG. The machine side is a coaxial feed line 201, and a ground means 203 is connected to the outer conductor 202 of the coaxial feed line 201 at a position separated from the terminal end of the antenna by a predetermined distance. Japanese Utility Model Laid-Open No. 3-61708 discloses a configuration in which a feeder wire terminal 205 is connected via a wire.

[0003]

[Problems to be solved by the device]

 Since the length of the above-mentioned conventional feeder is usually about 100 mm to 200 mm in wiring when the antenna is mounted, the conventional glass antenna feeder wire 100 shown in FIG. 4 has a lead wire (referred to as a single feeder wire) fluctuation and a vehicle body. The stray capacitance between and causes an unstable change in sensitivity.

Therefore, in this case, in the conventional technique, a preamplifier is provided between the radio receiver and the window glass antenna to amplify the reception output.

Further, in the conventional glass antenna feeder wire connection structure shown in FIG. 5, the sensitivity change due to the fluctuation is small, but in the FM frequency band, about 20 pF between the inner conductor and the outer conductor (vehicle body of the automobile). Capacitance is generated, and its reactance component shows a capacitive reactance of about 100Ω, which means that it is in a non-tuned state and the reception sensitivity decreases (becomes worse).

The present invention has been made to solve the above problems, and an object of the present invention is to provide a glass antenna feeder wire connection structure in which the reception sensitivity is reduced and the reception sensitivity is hardly changed in the FM frequency band. .

[0007]

[Means for Solving the Problems]

 In order to solve the above problems, a glass antenna feeder wire connection structure according to the present invention is a glass antenna feeder wire connection structure for connecting a glass antenna provided on a window glass of an automobile and a radio receiver, The glass antenna feeder is composed of only coaxial feeder lines, and is provided with grounding means for fixing the outer conductor to the vehicle body and electrically connecting the outer conductor to the vehicle body at a position distant from the terminal end on the glass antenna side by a predetermined distance. In the wire connection structure, the coaxial feeder is characterized in that an inner conductor is connected to a feeder wire terminal through an impedance matching element at a terminal end on the glass antenna side.

[0008]

[Action]

 The reactance (capacitance) of the stray capacitance generated between the inner conductor and the outer conductor (vehicle body) of the feeder coaxial part of the coaxial feeder is canceled by the reactance (inductivity) of the same magnitude, and the reactance component is made zero. Synchronize.

[0009]

【Example】

 Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing a glass antenna feeder wire connection structure according to the present invention, and FIG. 2 is an equivalent circuit thereof.

The glass antenna feeder line 1 is composed of a coaxial feed line 2, a coil (inductive reactance) 3 which is an impedance matching element, and a ground plate 4 which is a grounding means.

The coaxial feed line 2 includes an inner conductor 5, an insulator 6 that covers the inner conductor 5, an outer conductor 7 that is wound around the insulator 6, and a coating that entirely covers them. It consists of eight.

The coaxial feed line 2 exposes the outer conductor 7 by removing the coating film 8 at a position apart from the glass antenna side end portion by a predetermined distance (about 150 mm in this embodiment).

The ground plate 4 is formed by providing one end with an arcuate bent portion having a radius of curvature smaller than the cross section of the coaxial feeder line 2, and at the other end, a set screw (for fixing the ground plate 4 to the vehicle body ( A mounting hole 9 for inserting (not shown) is formed.

When the ground plate 4 is attached to the vehicle body with a set screw, the exposed portion 10 is fixed so as to be wound around one end of the ground plate 4, and then the set screw is inserted through the mounting hole 9. This is done by tightening it into a screw hole (not shown) formed in the vehicle body.

At this time, preferably, the fixed portion is soldered (brazed), and further, it is preferable to mold it with a resin or the like. As a result, the coaxial power supply line 2 is mechanically fixed to the vehicle body and is electrically connected to the vehicle body to be grounded.

The feeder coaxial 11 portion of the coaxial feeder 2 having a length of about 150 mm described above has a capacitance of about 20 pF between the inner conductor 5 and the outer conductor 7 (vehicle body of the automobile), and the reactance component is 100Ω. In the present invention, in order to tune, the capacitive reactance is canceled out and the capacitive reactance is canceled out to make the reactance component zero, that is, a coil (impedance matching element). ) 3 is inserted.

The coil 3 is, for example, an air-core coil using an enameled wire or the like of about 1.0φ, one end of which is connected to the terminal end of the coaxial power supply line 2 by means of crimping or soldering, and the other end is connected. The feeder wire terminal 12 is connected by means such as crimping or soldering.

At this time, as can be seen from the equivalent circuit of FIG. 2, since the low-pass filter is constituted by the combination of the capacitor (capacitive reactance) and the coil (inductive reactance), the frequency characteristic of this low-pass filter is If the inductance of the coil is properly selected so that the gain drops sharply from around the desired frequency (cut-off frequency), the gain will almost never drop in the passband below the desired frequency, and the loss of reception sensitivity will occur. Is reduced.

In the present embodiment, in consideration of the above description, the cutoff frequency is 100 MHz, and the coil inductance is 0.8 μH.

At this time, according to the low-pass filter, the high frequency side of the cutoff frequency is in the attenuation range, so that unnecessary frequency components exceeding the cutoff frequency are almost removed.

FIG. 3 is a graph showing the inductive reactance, that is, the receiving sensitivity (gain) at each frequency when the inductance of the coil is 0.8 μH, and is shown as a graph. The horizontal axis shows the frequency (unit: MHz). The vertical axis represents the receiving sensitivity (unit: dB). Since the frequency covers a wide range, the horizontal axis has a logarithmic scale.

In the figure, (a) is a frequency characteristic of a glass antenna using a glass antenna feeder wire connection structure according to the present invention with a coil, and (b) is a conventional glass antenna feeder wire connection structure without a coil. The frequency characteristics of the glass antenna using is shown.

From this graph, it is understood that the characteristics of the low-pass filter are obtained because the low frequencies are passed and the high frequencies are attenuated.

Further, in the operation as the low-pass filter, the reactance of the coil increases as the input frequency becomes higher, while the reactance of the capacitor is inversely proportional to the frequency, so that it is understood that it is greatly attenuated.

In other words, the high frequency side of the cutoff frequency rapidly falls into the attenuation range, so that unnecessary frequency components exceeding the cutoff frequency are almost removed.

Further, it can be seen that the sensitivity is improved by at least 3 to 4 dB or more in the FM frequency band at 70 to 90 MHz.

[0027]

[Effect of device]

 The connection structure of the glass antenna feeder wire according to the present invention cancels the stray capacitive capacitive reactance of the feeder coaxial by the inductive reactance, so that the reactance component becomes zero and can be tuned, and the coil and the stray capacitance are low-pass filters. It is possible to prevent excessive frequency components from being removed and prevent the S / N ratio from decreasing due to interfering radio waves such as noise that are mixed in from the outside, so that the receiving sensitivity is improved and it is possible to reduce There is no need to install a preamplifier between the window glass antenna.

Further, since the fluctuation and the stray capacitance with the vehicle body do not change unlike those of the single feeder line, the receiving sensitivity becomes stable with little variation.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a glass antenna feeder wire connection structure according to the present invention.

2 is an equivalent circuit of FIG.

FIG. 3 is a graph showing the receiving sensitivity (gain) of the antenna when the glass antenna feeder wire connection structure according to the present invention is used.

FIG. 4 is an explanatory view showing a conventional glass antenna feeder wire connection structure (feeder single wire).

FIG. 5 is an explanatory view showing a conventional glass antenna feeder wire connection structure (feeder coaxial).

[Explanation of symbols]

1 ... Glass antenna feeder line, 2 ... coaxial feeder line, 3 ...
Coil, 4 ... Ground plate (grounding means), 5 ... Internal conductor, 6
... Insulator, 7 ... Outer conductor, 8 ... Coating, 9 ... Mounting hole, 10
... exposed part, 11 ... feeder coaxial, 12 ... feeder wire terminal.

Claims (1)

[Scope of utility model registration request] 1. A connection structure of a glass antenna feeder line for connecting a glass antenna provided on a window glass of an automobile and a radio receiver, wherein the signal line comprises only a coaxial feeder line, and the glass antenna side. In a glass antenna feeder wire connection structure in which an outer conductor is fixed to a vehicle body at a position separated from the terminal end portion by a grounding means for electrically connecting the outer conductor to the vehicle body, the coaxial feeder line is a glass antenna side terminal portion. In the connection structure of the glass antenna feeder line, the inner conductor is connected to the feeder line terminal through the impedance matching element.