JPS6224961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distributed-coupled microstrip antenna that radiates electromagnetic waves from a conductor plate that is distributed-coupled to a microstrip line.

Conventionally, this type of distributed coupling type microstrip antenna has a dielectric substrate 3 as shown in FIG.
One method is to directly connect the conductor plate 1 to the microstrip line 2 formed above to supply power, and the other is to form the conductor plate 1 close to one microstrip line 2 as shown in FIG. Therefore, a method of distributively coupling the two (distributed coupling type) has been adopted.
In the figure, 4 indicates a ground conductor plate.

However, according to the direct connection type shown in Figure 1, one microstrip line 2 is required for each radiating element 1, so a power divider is required to arrange a large number of radiating elements and feed power to each element. This power distribution circuit requires a dielectric substrate with a size comparable to the effective radiation area, which detracts from the compact and lightweight characteristics of the microstrip antenna. Furthermore, according to the distributed coupling type shown in FIG. 2, multiple elements can be fed simultaneously with one line, so there is no need to prepare a dielectric substrate for the feeding circuit. When configuring an array antenna using a distributed coupling type and performing directional synthesis, the radiation intensity of the element is changed by changing the power coupling rate from the microstrip line to the radiating element. To achieve this, the distance between the microstrip line and the radiating element, s, and the width of the radiating element, w, are changed. However, if w becomes too large, a lateral current will flow in addition to the axial current parallel to the line. The magnitude becomes so large that it cannot be ignored, and the cross-polarization level of the radiated wave becomes larger than the permissible level. Therefore, there is a drawback that the range in which the radiation intensity can be weighted is narrow.

The present invention provides a distributed coupling type microstrip antenna in which generation of lateral current is suppressed even when the width of the radiation plate is increased, and radiation intensity can be weighted over a wide range.

That is, according to the present invention, a radiating element made of at least one conductive plate is formed between two parallel microstrip lines formed on a dielectric substrate, and the two microstrip lines are connected to each other. A distributed coupling microstrip antenna is obtained, characterized in that power is supplied from the line to the radiating element by distributed coupling.

Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 3 shows a row of distributed coupling microstrip antennas with input from a coaxial line. 5 in the diagram
6-1 and 6-2 indicate the connector (power input end) connecting the coaxial line and the microstrip line, and the non-reflection terminations. The input from connector 5 is divided into two equal parts,
Two parallel microstrip lines 2-1, 2
Traveling wave currents of the same phase and magnitude flow on -2. A part of the transmitted power accompanied by this traveling wave current is distributed and coupled to the radiation elements 1-1, 1-2, 1-3, 1-4 of the rectangular conductor plate and radiated, and the traveling wave power is transmitted in the traveling direction. , and the rest is absorbed by the non-reflection termination 6.

In the present invention having the above configuration, a rectangular conductor plate is placed between two parallel microstrip lines at an equal distance from both lines, and a portion of the transmitted power of both lines is transferred in equal proportions to the rectangular conductor plate. It is electromagnetically coupled to the plate, and radio waves are emitted from the current flowing in the axial direction on the outer surface of the rectangular conductor plate. The current flowing in the lateral direction is excited in opposite directions by the two microstrip lines, so it is canceled out, and even if the width of the rectangular conductor plate is varied over a wide range, the cross-polarized component of the radiated wave can be kept small. .

Next, design parameters that have important meaning when the present invention is put to practical use as an array antenna etc. will be explained using actual measured values.

In Fig. 3, the horizontal length of the rectangular conductor plate 1 is w, the distance between the microstrip 2 and the rectangular conductor plate 1 is s, the center distance of the rectangular conductor plate 1 is l, and the vertical direction of the rectangular conductor plate 1. Assume that the length of is lr, the thickness of telephone body substrate 3 is d, and the dielectric constant of dielectric substrate 3 is εr. The power coupling ratio η, which indicates the ratio of the power coupled and radiated to one element of the radiating element (rectangular conductor plate) 1 to the power transmitted to the microstrip 2, and the above-mentioned resonance frequency c at which this coupling is maximum. The relationship of the experimental data to the structural constants s and l is shown in FIGS. 4 and 5. Figures 4 and 5 are data obtained from experiments in the 3 GHz band. From Figure 4, the power coupling ratio η is determined by the interval s without changing the resonance frequency c, and from Figure 5, the resonant frequency c It is clear that is determined by the length l without changing the power coupling ratio η.

Therefore, the weighting of the element radiated power for directivity synthesis in this array antenna is as follows after determining the length l of the rectangular radiating element according to the operating frequency.
This can be done simply by adjusting the interval s. As a result, when the phase determined by the position of the radiating element is also considered, it is possible to relatively easily realize an array antenna with a low side lobe or an array antenna with special radiation directivity such as cosecant square.

In the above embodiment, the two microstrip lines are parallel and the radiating element is rectangular, but it is also possible to extend the shape to a non-parallel or non-rectangular shape.

In addition, in the above embodiment, the number of microstrip lines is two, but for three or more parallel lines, a conductor plate radiating element is provided in the middle of each line to make the planar antenna higher. It is also possible to expand the density to form.

As explained above, the present invention provides a conductor plate radiating element between two microstrip lines to reduce cross-polarized components and reduce side lobes while maintaining a thin structure. This has the effect of facilitating the realization of design parameters for directional synthesis.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional direct-coupled microstrip antenna, FIG. 2 is a perspective view of a conventional distributed-coupled microstrip antenna, and FIG. 3 is a distributed-coupled antenna showing an embodiment of the present invention. The perspective views of the microstrip antenna, FIGS. 4 and 5, are diagrams showing the relationship between the power coupling rate and the resonant frequency with respect to the structural constants in the distributed coupling type microstrip antenna according to the present invention. 1, 1-1, 1-2, 1-3, 1-4... Rectangular conductor plate (radiating element), 2-1, 2-2... Microstrip line, 3... Dielectric substrate, 4 ...Ground conductor plate, 5...Connector, 6-1, 6-2...
Non-reflective termination.

Claims (1)

[Claims] 1. A radiating element made of at least one conductor plate is formed between two parallel microstrip lines formed on a plane, and power is distributed from the two microstrip lines to the radiating element. A distributed coupling type microstrip antenna characterized in that the antenna is supplied by coupling.