JPH05327338A - Printed antenna - Google Patents

Abstract

PURPOSE:To provide a printed antenna for microwave transmission/reception, for which a cross polarized wave characteristic is satisfactory and a circularly polarized wave characteristic is satisfactory as well, by connecting a strip conductor and a ground conductor with a short-circuit conductor in one window on an insulated board. CONSTITUTION:From the edge of the opposite side window of a short-circuit conductor 11, a slot antenna element 19 is formed with a gap. On the side of a transmission line 14 on a board 15, a reflection board 18 is arranged through an insulated board 16 which thickness is 2.0mm. On the front face of this antenna, satisfactory circularly polarized waves can be obtained even without strongly coupling the element 19, and the strength of radiated power is maximum at a frequency 11.8GHz. In such a state, the element 19 is covered with the conductor, and the printed antenna for linearly polarized wave transmission/reception with the reflection board only for a strip antenna element with window is formed. Then, even when the window is rectangular, a cross polarized wave suppressing ratio is -25dB and it is a satisfactory value. Therefore, the band width of the gain/frequency characteristic of the antenna element and the cross polarized wave characteristic or the circularly polarized wave characteristic can be improved for this printed antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave transmitting / receiving printed antenna.

[0002]

2. Description of the Related Art A printed antenna having an antenna element and a transmission line formed on a printed circuit board has many advantages such as thinness, light weight, small size, suitable for mass production, and easy integration of electronic circuits. , Is used as an antenna for transmitting and receiving microwaves for mobile communication. There are various types of printed antennas, but a printed antenna that uses a linear strip antenna element and has a wide band by providing a window from which the ground conductor is removed is a printed antenna that is different from other printed antennas that use patch-type elements or the like. In contrast, attention is paid to the fact that there is only one resonance mode and the operation is stable.

Since this window also operates as a wide slot antenna element, it becomes a source of unwanted radiation for the strip antenna element. As a means for suppressing unnecessary radiation, the same inventor as that of the present invention has proposed to provide a convex portion on the window at the position of the central portion in the length direction of the strip antenna element (Japanese Patent Application No. 3-176212).

Further, when this linear strip antenna element is used as an antenna for orthogonal two-polarized wave reception and circular polarized wave transmission / reception used for satellite broadcast reception, etc., the strip antenna element and the slot antenna which is a linear element are used. It has been proposed to combine elements. If the strip antenna element and the slot antenna element are arranged along the excitation transmission line so that the feeding phase difference is 90 degrees, the radiated electric field of the strip element and the radiated electric field of the slot antenna element are spatially orthogonal to each other. Because there are 9
It has a phase difference of 0 degree and is a combination of excitation electromagnetic fields that are spatially orthogonal to each other and can efficiently radiate circularly polarized waves (the above description of the antenna relates to the transmitting antenna, Is due to the duality of the electromagnetic field,
It can be used for both sending and receiving).

Conventional examples of printed antennas that radiate circularly polarized waves by combining the linear elements described above are shown in FIGS.
Shown in.

FIG. 6 is a plan view showing a conventional example of a printed antenna that radiates circularly polarized waves by combining linear elements, and FIG. 7 is a conventional strip antenna with a window that constitutes the printed antenna of FIG. FIG. 9 is a plan view showing one of the elements, and FIG. 8 is a line 8 in FIGS. 6 and 7, which also shows a reflector.
It is sectional drawing in alignment with -8.

6 to 8, reference numeral 10 denotes a strip antenna element (strip conductor), and 12
Indicates a window, 13 indicates an input / output section, 14 indicates a transmission line, 15 and 16 indicate an insulator substrate, 17 indicates a ground conductor, 18 indicates a reflector, and 19 Indicates a slot antenna element, and 20 indicates a convex portion of the window. The convex portion 20 of the window is provided for the purpose of suppressing unnecessary radiation from the window 12, and the transmission line side is tapered for the purpose of weakening the coupling between the window 12 and the transmission line 14 and reducing the radiation from the window. It is provided. The detailed description of the function of the conventional printed antenna element is given in the above-mentioned patent application, and will not be repeated here.

[0008]

In orthogonal dual polarization receiving antennas for transmitting and receiving satellite broadcasts, circular polarization and polarization switching receiving antennas, etc., the cross polarization suppression ratio (main polarization of cross polarization) of antenna elements is Radiated electric field intensity ratio) to −25 dB
The following is required: When a strip antenna element with a window is used as an element for constructing such an antenna, as described above, in order to suppress unnecessary radiation from the window (a main factor that deteriorates the cross polarization suppression ratio),
Provide a convex portion on the window. The narrower the gap between the convex portion and the strip conductor, the better the cross polarization suppression ratio can be realized. However, if the gap is set to 0, the radiation from the combined slot antenna elements becomes very weak. ..

When a strip antenna element with a window having this gap of 0 is used, when the strip element and the slot element are made to have the same radiation intensity for the purpose of obtaining circular polarization, the slot element is strongly coupled to the transmission line. However, there is a drawback in that the characteristics of the transmission line change due to this, which makes designing difficult. Further, this defect can be remedied to some extent by making the gap of the convex portion extremely narrow, but even in this case, since the antenna element is usually formed by etching, it is difficult to set the gap to 0.2 mm or less. There is a drawback that it is difficult to suppress unnecessary radiation by itself.

Therefore, an object of the present invention is to provide a microwave transmitting / receiving printed antenna in which the antenna element has good cross polarization characteristics and at the same time has good circular polarization characteristics.

[0011]

In order to achieve the above object, the present invention provides a window formed in a ground conductor provided on one surface of an insulating substrate, and a strip conductive formed in the window. A body, a slot antenna element formed on the ground conductor in relation to the strip conductor, and a short-circuit conductor connecting the center of the strip conductor in the longitudinal direction to the ground conductor. The printed antenna is adopted.

[0012]

The present invention suppresses unnecessary radiation from the window by connecting the strip conductor and the ground conductor with the short-circuit conductor in one window, and at the same time, the short-circuit conductor is not on the slot side. The disadvantage of the conventional example that the radiation from the slot becomes weak as a result of combining the windowed strip element and the slot can be improved.

If the width of the short-circuit conductor is wider than that of the strip conductor, the resonance frequency of the strip conductor increases, and the resonance frequency is not determined only by the length of the strip conductor, which deteriorates designability. Also, the unwanted radiation from the window is
If the size is the same, it increases as the frequency increases,
Since the resonance frequency of the strip element increases, the cross polarization characteristic also deteriorates.

The reflector usually has a wavelength of λ at the used frequency.
Is placed at a position of λ / 4 from the strip conductor, but it is not particularly limited to the above value as long as the purpose of radiating an electromagnetic wave to one of the antennas can be achieved. Further, another insulator substrate may be sandwiched between the reflector and the reflector in order to fix the position of the reflector.

The insulating substrate of the antenna is not particularly limited as long as it has a uniform thickness and desired dielectric characteristics.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an enlarged plan view of an essential part of a first embodiment of a printed antenna of the present invention, and FIG. 2 is a line 2 of FIG.
2 is a sectional view taken along line -2, FIG. 3 is an enlarged plan view of an essential part of a second embodiment in which the printed antenna is applied to a circularly polarized wave transmitting / receiving printed antenna with a reflector, and FIG.
4 is a sectional view taken along line 4-4 of FIG. 5, and FIG. 5 is a plan view showing an entire third embodiment in which the printed antenna of FIG. 1 is applied to a circularly polarized wave transmitting / receiving printed antenna.

Referring to FIGS. 1 and 2, the thickness is 2.0 m.
The antenna element 1 is made of a strip conductor having a width of 1.0 mm and a length of 9.2 mm in a rectangular window 12 having a length of 14 mm and a width of 5.5 mm on one surface of an insulating substrate 15 of m.
Formed 0. At this time, the center of the strip conductor was connected to the edge of the window by a short-circuit conductor 11 having a width of 0.4 mm. The transmission line 14 for excitation was formed on the other surface of the insulator substrate 15.

Next, referring to FIGS. 3 and 4, an example in which the printed antenna shown in FIGS. 1 and 2 is applied to a circularly polarized wave transmitting / receiving printed antenna with a reflector is shown in these drawings. There is. In this printed antenna, a slot antenna element 19 is formed at a distance from the edge of the window on the side opposite to the short-circuit conductor 11, and another thickness of 2.0 mm is provided on the transmission line 14 side of the substrate 15. Insulator board 1
A reflection plate 18 is provided so as to be interposed therebetween.

In the front of the antenna shown in FIGS. 3 and 4, good circular polarization was obtained without increasing the coupling of the slot antenna element 19, and the radiated power intensity was maximized at the frequency of 11.8 GHz. .. In this state, when the slot antenna element 19 is covered with a conductor to form a linearly polarized wave transmission / reception print antenna with a reflector having only a window strip antenna element, the window shape is quadrangular (no taper is added). ), The cross polarization suppression ratio (the intensity ratio of the radiated electric field to the main polarization of cross polarization) is -25 dB.
And was a good value.

As a comparative example, in the printed antenna having the structure shown in FIGS. 7 and 8, the strip conductor 10 has a maximum radiated power intensity of main polarization at a frequency of 11.8 GHz.
When the length was adjusted to 9.4 mm, the cross polarization suppression ratio was -15 dB. The antenna of this comparative example is
Except for the shape of the window and the length of the strip element, the antenna is the same as the antenna shown in FIGS. 3 and 4 in which the slot antenna element is covered with a conductor.

As described above, the structure of the present invention has good cross polarization characteristics without the need to taper the window unlike the conventional strip antenna element with a window, and at the same time, when combined with a slot antenna element. It can be seen that the strip antenna element is capable of obtaining excellent circular polarization.

FIG. 5 shows an example of a circularly polarized wave transmitting / receiving print antenna formed by using the print antennas shown in FIGS. 3 and 4 as a basic element.

In the printed antenna shown in FIG. 5, when the arrangement interval of the basic elements was set to one wavelength of the transmission line 14, the radiation intensity was maximized in the front and at the same time the circular polarization characteristic was good. From this, it is understood that the coupling between the slot antenna element and the transmission line is not so strong as to disturb the characteristics of the transmission line, and the designability is good.

[0024]

As described in detail above, according to the present invention, it is possible to obtain a printed antenna having good cross polarization characteristics and circular polarization characteristics and good design.

[Brief description of drawings]

FIG. 1 is an enlarged plan view of a main part of a first embodiment of a printed antenna according to the present invention.

2 is a cross-sectional view taken along line 2-2 of FIG.

FIG. 3 is an enlarged plan view of an essential part of a second embodiment in which the printed antenna is applied to a circularly polarized wave transmitting / receiving printed antenna with a reflector.

4 is a cross-sectional view taken along line 4-4 of FIG.

FIG. 5 is a plan view showing an entire third embodiment in which the printed antenna of FIG. 1 is applied to a circularly polarized wave transmitting / receiving printed antenna.

FIG. 6 is a plan view showing a conventional example of a printed antenna that radiates circularly polarized waves by combining linear elements.

FIG. 7 is a plan view showing one of conventional strip antenna elements with a window which constitute the printed antenna of FIG.

FIG. 8 is a line 8 of FIGS. 6 and 7, showing also the reflector.
It is sectional drawing in alignment with -8.

[Explanation of symbols]

 10 Strip Antenna Element (Strip Conductor) 11 Short-Circuiting Conductor 12 Window 13 Input / Output Section 14 Transmission Lines 15 and 16 Insulator Substrate 17 Grounding Conductor 18 Reflector 19 Slot Antenna Element 20 Convex Portion of Window

Claims (5)

[Claims] 1. A window formed in a ground conductor provided on one surface of an insulating substrate, a strip conductor formed in the window, and formed in the ground conductor in association with the strip conductor. And a short-circuit conductor that connects the center of the strip conductor in the lengthwise direction to the ground conductor. 2. The printed antenna according to claim 1, wherein the short-circuit conductor connects the strip conductor to a ground conductor on the side opposite to the slot antenna element. 3. The printed antenna according to claim 1, wherein the width of the short-circuit conductor is narrower than the width of the strip conductor. 4. The printed antenna according to claim 1, wherein the printed antenna is a basic element, and a plurality of the basic elements are provided on an insulating substrate. 5. The printed antenna according to claim 1, wherein the insulating substrate is provided with reflectors at intervals.