JPH03237803A - Three-wave common antenna for automobile with coaxial line - Google Patents

Abstract

PURPOSE:To simplify the structure by setting the length of an expanded inner conductor prolonged from an outer conductor and the length of the outer conductor of a coaxial conductor to be a length equivalent to a specific wavelength, feeding an automobile telephone wave to the outer conductor and feeding an AM/FM wave to the expanded inner conductor. CONSTITUTION:The length of an outer conductor 2 of a coaxial conductor is selected to be an integral number of multiple of a 1/2 wavelength of an automobile telephone radio wave and the length of an expanded inner conductor 1 prolonged from the outer conductor 2 is selected to be an integral number of multiple of a 3/4 wavelength of the automobile telephone radio wave in a 3-wave common use antenna comprising an automobile telephone antenna and an AM/FM antenna as one antenna. Then an automobile telephone radio wave is fed to the outer conductor 2 and the AM/FM wave is fed to the expanded inner conductor 1. Thus, no separation circuit is required after the three-wave common use antenna and the circuit constitution of a receiver is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a three-wave shared antenna for automobiles with parallel tracks.

[Prior Art] Recently, with the spread of car phones, a three-wave antenna that includes a car phone antenna and an AM/FM antenna in one antenna has been attracting attention. In this type of antenna, a certain length is required to obtain sufficient gain for AM/FM waves, and a broad characteristic of 3 to 4 dBi is required for car phone waves. ing.

[Invention tries to solve! 1111 In the above-mentioned conventional three-component antenna for automobiles, AM
/FM waves and car phone waves are fed at the same point, so after the three-wave common antenna, AM/FM waves are fed at the same point.
A separation circuit is provided to separate the waves from the car phone waves. As described above, since a separation circuit exists after the three-component automotive antenna, there is a problem in that the circuit configuration of the receiver becomes complicated.

An object of the present invention is to provide a three-component antenna for an automobile that has a simpler structure than a conventional three-wave antenna.

[Means for Solving the Problems] In the present invention, the length of the outer conductor of the coaxial conductor is set to an integral multiple of the 1/2 wavelength of the car telephone wave, and the length of the elongated inner conductor extended from the outer conductor is The wavelength is set to 3/4 or 5/4 of the car telephone wave, and the car phone wave is fed to the outer conductor, and the AM/FM wave is fed to the elongated inner conductor.

[Function] In the present invention, the length of the outer conductor of the coaxial conductor is set to an integral multiple of 1/2 wavelength of the automobile telephone wave, and the length of the elongated inner conductor extended from the outer conductor is set to the length of the outer conductor of the automobile telephone wave. 374 or 5/4 wavelength, and feeds the car telephone wave to the outer conductor and the AM/FM wave to the extended inner conductor, so there is no need for a separate circuit after the three-component car antenna, and the receiver The circuit configuration is simple.

[Example] FIG. 1 is a basic configuration diagram showing an embodiment of the present invention.

In the three-wave shared antenna lO shown in FIG.
The length of the outer conductor #2 is set to be an integral multiple of the 1/2 wavelength of the MT wave. Then, the MT wave is supplied to the outer conductor #2, and the extended inner conductor #2 is
AM/FM waves are fed to the internal conductor following 1.

FIG. 2 is a diagram showing an equivalent configuration of the above embodiment; FIG. 2(a) shows the MT operation (car phone operation), and FIG. 2(b) shows the AM/FM operation. It is something.

During MT operation, the AM/FM power supply side is regarded as a load, and during AM/FM operation, the MT power supply side (mobile telephone power supply side) is regarded as a load.

Note that the shaded portion in FIGS. 1 and 2 is the body of the automobile.

FIG. 3 is a diagram showing the above-mentioned load as a voltage drop at both ends, and an electrically equivalent configuration including an image.

FIG. 4 is a diagram showing a further exploded electrical circuit.

In this Figure 4, the line drawn from the (V■-Va) voltage source to the extended inner conductor #l and the outer conductor #2 is the first
This is the inner part of the coaxial line below point A shown in the figure. M
During T operation, the AM/FM power supply side can be regarded as a load Za.

Negative here? ifZ a is infinite, then! 1! Part of the coaxial line looking down from point A shown in Figure 4 (outer conductor #2)
becomes an open-ended line. Since the length of the outer conductor #2 is an integral multiple of the 172 wavelength of the MT wave, the impedance (impedance of the outer conductor #2) looking down from point A is infinite.

Therefore, the space between the outer conductor #2 and the elongated inner conductor #l is open.

For this reason, the MT wave fed to outer conductor #2 does not ride on extended inner conductor #1. When measuring , radio waves are also transmitted above point A. In addition, when the length above point A (the length of the extended internal conductor #l) is measured as an integral multiple of the 1/2 wavelength of the MT wave, that part is congested and the extended internal conductor #l is relatively large.
A current is applied to. This indicates that side lobes are caused in the radiation pattern. When the length above point A (length of extended internal conductor #l) is set to 3/4 wavelength of the MT wave, the current convergence above point A is 1/4 of the maximum value.
A gain of 2.98dlli was obtained with a broad radiation pattern.

FIG. 5 shows the current distribution measured when the length above point A (the length of the extended internal conductor #l) was set to 5/4 wavelength in the above example.

At this time, the gain is 4.63 dBi.

The same level of performance as the existing three-wave antenna was obtained. Compared to the existing radiation pattern, a smaller sight rope was obtained. In addition, the frequency characteristics of the input impedance have relatively large changes in both the real and imaginary parts, making it difficult to match.As for the current distribution for FM waves, there is no influence from the same part, and the antenna length is 0.15 wavelength. Due to the shortness of the wave, it became a triangular wave.

[Effects of the Invention] According to the present invention, there is no need for a separation circuit after the three-component automotive antenna, and the circuit configuration of the receiver is simple.

T! 55rE1 is 5 points above from point A in the above example.
FIG. 4 is a diagram showing the current distribution when the wavelength is set to /4.

lO・・・Three liquid common antenna, #1...Extended internal conductor, #2...Outer conductor.

Claims (2)

[Claims] (1) The length of the outer conductor of the coaxial conductor is 1
/2 wavelength, and the length of the extended inner conductor extended from the outer conductor is set to 3/4 or 5/4 wavelength of the car phone wave, and the car phone wave is applied to the outer conductor. A three-wave shared antenna for an automobile with a coaxial line, characterized in that it feeds power and feeds AM/FM waves to the elongated internal conductor. (2) The three-wave shared antenna for an automobile with a coaxial line according to claim (1), wherein the elongated internal conductor is expandable and retractable.