JPH04122107A - Microstrip antenna - Google Patents

Abstract

PURPOSE:To reduce a diameter of an antenna element while suppressing a dielectric constant of a dielectric board by providing four slots to a conductor plate in a shape of a cross and feeding at least one slot. CONSTITUTION:An electromagnetic field is induced in four slots 6-9 by feeding the slot 6 from a tri-plate line respectively. Then a disk shaped radiation element 4 is excited by the electromagnetic field and a radio wave radiates therefrom. In this case, in the relation between the electromagnetic field at the lower side of a microstrip antenna and the slots 6-9, the direction of the magnetic field and the direction of the slots 6-9 are coincident with each other as show in figure and the TM 21 mode is easily excited. The TM 21 mode is excited from the disk shaped radiation element 4 with a comparatively small diameter by providing the slots 6-9 in a shape of a cross.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a microstrip antenna that resonates in higher-order modes and radiates a conical beam.

(Prior art) Microstrip antennas are easy to manufacture and suitable for thinning and weight reduction, and they also incorporate active elements such as amplifiers and feeder circuits using MMIC (monolithic microwave integrated circuit) devices. Therefore, it is being considered for use in a variety of fields, including antennas onboard satellites and antennas for mobile objects.

Among them, electromagnetically coupled antennas, such as the slot-coupled fed microstrip antenna, are suitable for multilayer structures and require fewer electrical connections between upper and lower layers, making production easier. It has the advantage of being

In addition, by forming an array of such microstrip antennas, it is possible to realize highly functional antennas such as beam scanning and low sidelobes.

By the way, when circular microstrip antennas are arranged into an array, for example, it is common to use them by resonating in the TMII mode, which is the fundamental mode.

However, in Japan, when used as a satellite communication antenna mounted on a mobile object, the angle at which the stationary satellite is viewed from the ground is about BO degrees from the zenith, as shown in Figure 7, so the main beam is directed toward the zenith. An antenna that resonates in a higher-order mode such as the 7M21 mode that emits a conical beam (see figure (b)) is more convenient as an array antenna element than an antenna that resonates depending on the fundamental mode toward which it is directed (see figure (a)). good.

However, in order to cause the microstrip antenna to resonate in the 7M21 mode, it is necessary to increase the diameter of the antenna element, so it is difficult to arrange the antenna elements at intervals that do not generate grating lobes.

Therefore, it is conceivable to reduce the diameter of the antenna element by using a dielectric substrate with a high dielectric constant, but this causes problems such as increased dielectric loss and narrowed band.

(Problem to be Solved by the Invention) In the conventional array antenna that uses a microstrip antenna that resonates in a higher-order mode as an antenna element, the diameter of the antenna element becomes large, so it is necessary to meet conditions that do not generate grating lobes. It is difficult to arrange antenna elements at intervals of . Therefore, it is conceivable to reduce the diameter of the antenna element by using a dielectric substrate with a high dielectric constant, but this causes problems such as increased dielectric loss and narrowed band.

The present invention was made based on the above-mentioned circumstances, and an object of the present invention is to provide a microstrip antenna in which the diameter of an antenna element can be reduced while suppressing the dielectric constant of a dielectric substrate.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a conductor plate in which four slots are provided in a cross shape, and at least one slot provided in this conductor plate. and a circular radiating element arranged to face the conductive plate and excited by the four slots.

Further, a second invention provides a conductor plate in which six slots are provided radially at approximately equal intervals, a power feeding means for feeding power to at least one slot provided in the conductor plate, and a power supply unit facing the conductor plate. and a circular radiating element excited by the six slots.

(Function) In the present invention, by feeding power to at least one slot provided in the conductive plate, an electromagnetic field is induced in each slot, and the circular radiating element is excited by this electromagnetic field. At that time, the resonant frequency of the higher-order mode can be controlled according to the length and width of the slot provided in the conductor plate.
By setting the length and width of the slot to appropriate values, it is possible to reduce the diameter while suppressing the dielectric constant of the heavy substrate.

(Example) Hereinafter, details of embodiments of the present invention will be explained based on the drawings.

FIG. 1(a) is a vertical cross-sectional view of a microstrip antenna according to an embodiment of the present invention, FIG. 1(b) is a plan view thereof, FIG. 1(C) is a cross-sectional view along CC, and FIG. 1(d) is a dd cross-sectional view taken in the direction of arrows.

The microstrip antenna shown in the figure is constructed by stacking three dielectric substrates 1.2.3.

A circular radiating element 4 made of a thin conductive film is formed on the surface of the first dielectric substrate 1.

A conductive plate 5 made of a thin conductive film is formed on the entire surface of the second dielectric substrate 1, and four slots 6 are formed on the surface of the second dielectric substrate 1.
．． 7, 8, and 9 are provided in a cross shape. The intersection center 10 of these slots 6.7, 8.9 is arranged to coincide with the center 11 of the circular radiating element 4.

There are four slots 6.7 on the surface of the third dielectric substrate 3.
, 8.9 (here, slot 6
shall be. ) at a predetermined position. A ground conductor 13 made of a thin conductive film is formed on the entire surface of the back surface of the third dielectric substrate 3, and a connector 1 is connected to the center conductor 12 and the ground conductor 13.
4 are provided.

The RF multiplied signal is input and output to the connector 14 .

The conductor plate 5, the center conductor 12, and the ground conductor 13 function as a triplate line that supplies power to the slot 6.

Note that the conductor on the dielectric substrate 1.2.3 is formed, for example, by etching a pattern of a thin conductive film on the surface of the substrate.

Next, the operation of the microstrip antenna configured in this way will be explained.

When power is supplied to slot 6 from the triplate line, electromagnetic fields are induced in each of the four slots 6.7 and 8.9.

The circular radiating element 4 is excited by these electromagnetic fields and radio waves are radiated.

At this time, the relationship between the electromagnetic field at the bottom of the microstrip antenna and each slot 6.7, 8.9 is such that the direction of the magnetic field matches the direction of each slot 6.7, 8.9, as shown in Figure 2. This makes it easier to excite the 7M21 mode.

Here, the most important parameter that determines the resonant frequency of the TM21 mode is the diameter of the circular radiating element 4, but the length of each slot 6.7, 8.9 is also related to the resonant frequency; By increasing the length of 8.9, the resonant frequency can be made lower than the resonant frequency determined by the circular radiating element 4. That is, in the microstrip antenna of this embodiment, the slots 6.7, 8.9
By arranging them in a cross shape, the TM21 mode can be excited by the circular radiation element 4 having a relatively small diameter.

Furthermore, in the microstrip antenna of this embodiment, since it is sufficient to feed power to at least one slot 6, the configuration is simplified.

Furthermore, since a triplate line is used, a quarter wavelength transformer, an oven stub, etc. can be easily constructed, and it is easy to match the slot and the line.

Next, the present invention will be explained in detail.

FIG. 3 shows the measurement results of the reflection characteristics seen from the connector 14.

Here, the radius of the circular radiating element 4 is 32cm, and the slot 6 is
．． 7,8.9 length is 22si+, dielectric substrate 1°2.
The dielectric constant of 3 was set to 2.55.

From the measurement results shown in the figure, it can be seen that the resonance frequency of the 7M21 mode is 2141 MHz. That is, the resonance of the 7M21 mode occurs when the radius of the circular radiating element 4 is about 0.228λ (λ is the free space wavelength).

This shows that the resonant radiation radius of the 7M21 mode of the circular microstrip antenna is around 0.3λ in the case of single-point feeding, so it is possible to excite higher-order modes with a very small radiating element.

FIG. 4 shows the measurement results of the radiation directivity of this antenna.

From the results shown in the figure, it can be seen that a conical beam is formed when the 7M21 mode is excited.

Thus, in the case of a negative point feeding radiating element, the spacing between the antenna elements becomes large, many grating lobes are generated during beam scanning, and the gain is reduced. On the other hand, according to the microstrip antenna of the present invention, since the TM mode is resonated by the radiating element with a small radius, the gain does not decrease even when beam scanning is performed in an array and is effective.

In addition, although the above embodiment uses a triplate line as a power feeding means to the slot, the same effect can be obtained even if a microstrip line is used as a power feeding means. Regardless of which power feeding means is used, since electromagnetic field coupling type power feeding is performed, there is no need to electrically connect the upper and lower layers, and manufacturing is easy.

In addition, since the microstrip antenna of the present invention can configure each line in layers, the entire antenna can be made thin due to the multilayer structure, and a feeding circuit or MMIC device for arraying or circular polarization can be incorporated in each layer. It is easy to do.

Furthermore, by electrically connecting the center 11 of the circular radiating element 4 and the intersection center 10 of the slot 6.7°8.9, the microstrip antenna of the present invention eliminates unnecessary high-order signals such as TM12 and 7M22 modes. mode can be prevented from occurring. At this time, by using metal screws for electrical connection, each board of the multilayer structure can be firmly fixed.

Furthermore, by passing a coaxial line above and below the center 11 of the circular radiating element 4, another antenna having a different frequency, polarization, and radiation directivity can be used in common above this antenna. At this time, a circularly polarized antenna can be constructed by changing the polarization of the upper and lower antennas and connecting these two antennas using a T-branch, hybrid, or the like.

FIG. 5 is a diagram showing an example of the configuration of such a circularly polarized antenna.

Figure (a) is a vertical cross-sectional view of this circularly polarized antenna, Figure (b)
) is its plan view, the same figure (C) is a cc cross-sectional view, and the same figure (
d) is a DD cross-sectional view, and (e) is an ee cross-sectional view,
FIG. 5(f) is a cross-sectional view of ff, and FIG. 1(g) is a cross-sectional view of gg.

In the same figure, 21.27 is a circular radiating element, 23.29
have four slots 41, 42, 43, 44 and 51 respectively
．． 52.53.54 is a conductor plate provided in a cross shape, 25
is a triplate line, 31 is a triplate line including a T branch for circularly polarized power feeding, 33 is a ground conductor, 34 is a connector, 35 is a coaxial line for feeding power to the upper antenna, 22° 24.26 , 28, 30, and 32 indicate dielectric substrates.

The circularly polarized antenna configured in this way has three
It is said to be an antenna that radiates different polarized waves depending on the layer.
Each of the upper and lower antennas operates in the same manner as the antenna shown in FIG.

By adjusting the radius and slot size of the radiating elements of the upper and lower antennas, it is possible to easily achieve resonance at the same frequency. Circularly polarized waves can be synthesized by providing a desired phase difference.

In the above embodiments, the case of the 7M21 mode as the higher-order mode has been described, but it is also possible to radiate a conical beam using the same configuration in the case of the even higher-order 1M31 mode. In this case, the conductor plate 5 shown in FIG. 1(c) has six slots 61,
The conductor plates 67 may be provided radially at approximately equal intervals of 62, 63 degrees, 64 degrees, 65 degrees, and 66 degrees.

[Effects of the Invention] As explained above, according to the present invention, four slots are provided in the conductor plate in a cross shape, and power is supplied to at least one slot, so that while suppressing the dielectric constant of the electric substrate,
The diameter of the antenna element can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a microstrip antenna according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the microstrip antenna shown in FIG. 1, and FIGS. FIGS. 5 and 6 are diagrams showing experimental results of the present invention, FIGS. 5 and 6 are diagrams for explaining other embodiments of the present invention, and FIG. 7 is a diagram for explaining a conventional example. 1.2.3... Dielectric substrate, 4... Circular radiation element,
5... Conductor plate, 6, 7, 8.9... Slot, 10
... Center of intersection by slot, 11 ... Center of circular radiating element, 12 ... Center conductor, 13 ... Ground conductor, 1
4... Connector. Applicant Toshiba Corporation Patent Attorney Satoshi Suyama - (a) Figure 2 "0 (a) No. 5 Sub-No. 5- (g) No. 51

Claims (2)

[Claims] (1) A conductor plate in which four slots are provided in a cross shape; a power feeding means for feeding power to at least one slot provided in this conductor plate; A microstrip antenna comprising: a circular radiating element excited by two slots. (2) a conductor plate in which six slots are provided radially at approximately equal intervals; a power feeding means for feeding power to at least one slot provided in the conductor plate; , and a circular radiating element excited by the six slots.