JPH088635A - Antenna impedance matching box and antenna system using the impeadance matching box - Google Patents

Abstract

PURPOSE:To attain the impedance matching between an antenna and a transmission line in a wide band and neither adjustment nor complicated mechanism required by connecting an inverse circuit of antenna impedance to the output terminal of the antenna to constitute a constant resistance circuit. CONSTITUTION:An inverse circuit of antenna impedance is connected to the output terminal of an antenna so that a constant resistance circuit is constituted. Two monopole antennas are placed with a space 2r secured between them to construct an antenna system, and a 180-degree hybrid circuit 3 synthesizes both sum and difference outputs based on the outputs of two antennas which are led by the transmission lines of the same length. Then a 90-decree hybrid circuit 4 shifts the phase of the sum output by 90 degrees to the phase of the difference output. Therefore both outputs have the same phase. A goniometer 5 applies these outputs of the same phase to the fixed windings which are placed orthogonal to each other. Thus an output is obtained from the rotary winding of the goniometer 5 in response to the angle of the rotary winding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna matching device in the medium-wave band and the short-wave band and a receiving antenna system using the antenna matching device.

[0002]

2. Description of the Related Art A conventional receiving antenna used in the medium-wave band and the short-wave band has a short length as compared with the wavelength, and in many cases, the antenna impedance is capacitive. For this reason,
Neutralize the reactance for each frequency used,
The remaining resistance is increased to match the characteristic impedance of the transmission line. Further, in order to obtain a specific directivity, a method is adopted in which the output phases of a plurality of antennas are controlled by a phase shifter and combined.

[0003]

As described above, in the conventional matching device used in the medium-wave band and the short-wave band, complicated adjustment is required for each operating frequency, and it is complicated to automate. I needed a good servo mechanism. Furthermore, in an antenna system that performs directional synthesis, the phase to be controlled differs for each frequency, so a complicated control device is required when targeting a wide band.

The present invention has been made in order to solve such a problem and is unadjusted and has a wide frequency band.
Matching device with flat amplitude characteristics and using this matching device, the null direction of the directivity is directed to the desired direction by simple operation, or the same directivity for each frequency, for example, cardioid type directivity The purpose is to obtain a possible antenna system.

[0005]

In the antenna matching device according to the present invention, a constant resistance circuit is constructed by connecting an antenna impedance inverse circuit to the antenna output terminal. In addition, the directivity is controlled without directly controlling the phase.
One of the sum and difference of the base antenna outputs is phase-shifted by 90 degrees and processed by a goniometer.

[0006]

According to the present invention, since the matching unit is composed of a constant resistance circuit, matching with the characteristic impedance of the transmission line is possible over a wide band without adjustment, and a flat output characteristic with respect to frequency is obtained. To be Also, since the sum output and difference output of the two antennas are in proportion to the sine and cosine regardless of the frequency, if these are applied to the goniometer and the output is taken out, the output depends on the rotor angle. Directivity is obtained.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration when a matching device according to the present invention is used for a monopole antenna. In the figure,
C _a is the equivalent capacitance of the antenna, and C ₁ is a capacitor added to absorb the capacitance change of the antenna. L is an induction coil and resonates with C _a + C ₁ at the lower limit frequency of use. R is a resistor having a value of Q = 1 at the resonance frequency. C _{2 is} also a capacitor, and its value is C _a + C ₁ . T is a transformer,
R is transformed into the characteristic impedance Z of the transmission line. At this time, since the circuits surrounded by the dotted lines constitute reverse circuits to each other, the output impedance of the circuit seen from the primary side of the transformer T is R regardless of the frequency. This R is the metamorphic ratio (R
It is converted into a characteristic impedance Z ₀ of the transmission line by a transformer T of / Z ₀ ) ^1/2 . Effective height h of this antenna
_eff , the open output e ₀ (V) of this circuit due to the electric field of e (V / m) has a flat output characteristic with respect to frequencies above the resonance frequency as shown by the following equation.

[Equation 1] Here, ω ₀ is the resonance angular frequency, and ω is the used frequency.

FIG. 2 is a diagram showing a configuration of an antenna system for performing directivity synthesis using the two antennas and a matching unit,
FIG. 3 shows directional characteristics when directivity is directed in each direction.
Reference numeral 1 is a monopole antenna, and 2 is a matching unit having the above performance. These antennas are arranged with a spacing of 2r to form an antenna system. Reference numeral 3 denotes a 180-degree hybrid circuit, which synthesizes a sum output and a difference output from two antenna outputs guided by equal-length transmission lines. Reference numeral 4 denotes a 90-degree hybrid circuit, which shifts the phase of the sum output by 90 degrees with respect to the phase of the difference output. As a result, the phases of both outputs are in phase. Reference numeral 5 is a goniometer, and both outputs of the same phase are applied to fixed windings arranged orthogonally. Goniometer 5
An output corresponding to the angle of the rotary winding can be obtained from the rotary winding. Now, when the angle of the rotary winding is α and the space between both antennas is represented by a phase angle, and 2πr / λ (λ is a wavelength),
From this antenna system, the angle α of the rotary winding is 2πr · si
When there is a relationship of nα ′, the directivity of the output E of the goniometer 5 is as shown in FIG. 3 according to the rotary winding angle of the goniometer 5 as represented by the following equation. FIG. 3 shows the directional characteristics when the angle α ′ of the goniometer is 0 degree, 45 degrees, and 90 degrees, and “0 →” indicates the null direction.

[Equation 2] Where θ is the azimuth angle with respect to the antenna system.

As described above, according to the antenna matching device of the present invention, it is possible to perform the matching between the antenna and the transmission line in the medium wave band and the short wave band, which requires complicated adjustment, over a wide band without adjustment. In addition, it does not require a complicated mechanism and can be configured with a small number of circuit components. Furthermore, the antenna system according to the present invention enables unadjusted directional synthesis over a wide band with a simple configuration. Therefore, when interference occurs in the same frequency band, the interference wave can be removed and the desired wave can be effectively received by a simple operation of rotating the goniometer. Further, even when a cardioid type directivity having a large front-to-back ratio over a wide band is required, the object can be achieved by a simple operation of simply changing the angle of the goniometer for each frequency.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an antenna matching device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an antenna system according to an embodiment of the present invention.

FIG. 3 is a diagram showing the directivity of an antenna system according to an embodiment of the present invention.

[Explanation of symbols]

C _a ; Equivalent capacitance of antenna, C ₁ , C ₂ ; Battery, L; Induction wire ring, R; Resistor 1; Monopole antenna, 2; Matching device, 3; 180 degree hybrid circuit 4; 90 degree hybrid circuit, 5; Goniometer

Claims (2)

[Claims] 1. In a matching device for matching the output of an antenna with the characteristic impedance of a transmission line, a constant resistance circuit is constructed by adding a circuit network forming an inverse circuit of the equivalent impedance of the antenna to the output end of the antenna. Antenna matching device characterized by 2. Two antennas to which the antenna matching device of claim 1 is added are arranged at intervals, and one of the sum and difference of their outputs is phase-shifted by 90 degrees and applied to a goniometer. Antenna system characterized by