JPH03201804A - Print antenna - Google Patents

Abstract

PURPOSE:To make design ability satisfactory and to improve gain even when a reflection board is mounted by providing a window and a strip conductor on one surface of the ground conductor of a microslot line. CONSTITUTION:On one surface of an insulator substrate 16, a microstrip line 12 for excitation is formed by using printing technique and on the other surface, a linear strip antenna element (strip conductor) 10 is formed at a position slightly separated from the microstrip line 12. Then, a window 14 is formed to remove the surrounding ground conductor. Since the window 14 and the strip conductor 10 are formed on the same surface, a relative position relation between the both can be made comparatively easy and accurate. Thus, even when the reflection board is mounted, the design ability is made satisfactory and an antenna equipment can be obtained with a wide frequency band and high gain.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a printed antenna (printed array antenna) for transmitting and receiving microwaves, and particularly to a printed antenna used for transmitting and receiving circularly polarized waves.

(Prior art) Printed antennas have many advantages, such as being thin and can be installed so they do not take up much space, are aesthetically pleasing, and can be manufactured relatively easily and at low cost using printing technology. The frequency band of the antenna is narrower than that of other types of antennas that use the same principle as condensing light using reflective surfaces, and high gain is achieved by arranging a large number of radiating elements with a size of about λ/2 (λ is the wavelength of the electromagnetic wave). When attempting to increase the antenna gain, the length of the microstrip line that excites each element becomes longer, which increases the transmission loss of the microstrip line, resulting in the disadvantage that the antenna gain cannot be increased.

Of these, the transmission loss of a microstrip line can be divided into dielectric loss, which is determined by the dielectric loss of the insulating substrate material, conduction loss, which increases as the substrate becomes thinner for the same line width, and radiation loss from the line. can. Therefore, the loss can be suppressed by not exposing the microstrip line, by making the radiation loss negligible, and by using a thick substrate made of a low-loss material.

On the other hand, several proposals have been made for ways to widen the frequency band of printed antennas, but for linear strip antenna elements, a window with the ground conductor removed on the opposite side of the strip element across the board is provided. Suggestions have been made.

A printed antenna using a strip element that has a wide band using this method is superior in that it has only one resonance mode and is stable in operation, unlike other printed antennas that use patch-type elements or the like.

Furthermore, when using this linear strip antenna element as an antenna for transmitting and receiving circularly polarized waves used for satellite broadcast reception, etc., it is necessary to combine it with a slot antenna element, which is also a linear element, and use a microstrip line for excitation. It has been proposed to arrange the power supply so that the power supply phase difference is 90° along the line. When arranged in this way, the radiated electric field of the strip element and the radiated electric field of the slot are spatially orthogonal, so they are excited with a temporal phase difference of 90°, and circularly polarized waves can be efficiently generated. It can be radiated.

In this way, the circularly polarized wave transmitting/receiving printed antenna constructed by combining linear elements has the characteristic of stable operation of the linear elements, and is arranged so that the feeding phase difference is 90°, so that each A feature of this device is that the reflected wave components from the device cancel each other out on the excitation microstrip line, resulting in a wide band.

Conventional examples of printed antennas that radiate circularly polarized waves using a combination of linear elements as described above are shown in FIGS. 9, 10, and 11.

FIG. 9 is a plan view showing a conventional example of a printed antenna that radiates circularly polarized waves by a combination of linear elements;
FIG. 0 is a plan view showing a pair of a conventional windowed strip antenna element and a slot element that constitute the printed antenna of FIG. 9, and FIG. 11 also shows a reflecting plate, which will be described later.
11 is a cross-sectional view taken along line 11-11 of FIGS. 9 and 10. FIG.

Referring to these drawings, a linear strip antenna element (strip conductor) 24 is provided on one side of the insulating substrate 16, and due to electromagnetic coupling with the microstrip line 12, a frequency determined by the length of the linear strip antenna element is achieved. Electromagnetic waves of fO are efficiently radiated.The frequency band is widened by the window 14, which removes a portion of the ground conductor 18, but at the same time, electromagnetic waves are radiated to both sides of the antenna.

In order to cause the electromagnetic waves radiated to both sides of the antenna to be radiated only to one side, a reflecting plate 20 as shown in FIG. 11 is provided. The reflector may be provided on either side of the board, but in the example shown in FIG. is equipped with a reflective plate.

(Problem to be Solved by the Invention) It is known that this reflector can increase the antenna gain depending on the position where it is placed, and the antenna gain can be doubled (+3 dB) at the maximum. However, when we actually made a printed antenna with the configuration shown in Figure 9 and measured the gain difference between before and after loading the reflector, we found that it was 1.6 times (+2.0dB). There were disadvantages in that there was no L, and the frequency band of the antenna became narrower.

On the other hand, the electrical characteristics of each element change depending on the position where the reflector is placed, and this change is thought to cause the aforementioned drawbacks, so it is necessary to design the antenna with the reflector loaded. However, for example, it is not very practical to perform a three-dimensional analysis of only the L element of a windowed strip antenna element including a reflector from the viewpoint of calculation time, computer storage capacity, etc.

Further, the characteristics of a windowed strip antenna element change even if the relative positions of the window and the strip conductor are shifted, but it is difficult to align the front and back sides of a thick substrate.

On the line 11-11 in FIGS. 10 and 11 and in the vicinity of the microstrip line 12, the strip conductor 24
Since the relative positions of the window 14 and the end of the window 14 are close to each other, accuracy cannot be expected when obtaining design data through experiments.

As mentioned above, the characteristics of a printed antenna that radiates circularly polarized waves by combining a windowed strip antenna element and a slot antenna element change when a reflector is loaded, but there are several reasons for this change. Even if the changes were known through experiments, it was difficult to extract the influence of the reflector, and there was a drawback that designability was poor.

Therefore, it is an object of the present invention to provide a printed antenna that eliminates the above-mentioned drawbacks, has good design even when a reflector is loaded, has a wide frequency band, and has a high gain.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a printed antenna for transmitting and receiving microwaves, which includes a window formed in a ground conductor provided on one surface of an insulating substrate; A printed antenna characterized in that it has a strip conductor formed as a strip antenna element within the window.

(Function) The present invention provides a window and a strip conductor on one surface (side) of the ground conductor of the microslot line, so it is easy to design even when a reflector is loaded, and it is also better than the conventional one. This can improve the drawbacks such as narrow frequency band and limited increase in gain.

(Example) Next, a preferred example of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged plan view of essential parts of a first embodiment of the printed antenna of the present invention, FIG. 2 is a sectional view taken along line 2-2 in FIG. 1, and FIG. The second example applies a printed antenna to a printed antenna for transmitting and receiving circularly polarized waves with a reflector.
FIG. 4 is a cross-sectional view taken along the line 4-4 in FIG. 6A and 6B are cross-sectional views and coordinate systems for explaining the characteristics of the printed antenna of the present invention; FIG. 7 is a plan view showing the entire third embodiment applied to an antenna; FIG. FIG. 8 is a characteristic diagram of a conventional printed antenna for comparison with the characteristics of the printed antenna of the present invention.

Referring first to FIGS. 1 and 2, the insulator substrate 16 (
A microstrip line 12 for excitation is formed using printing technology on one side of the antenna (Fig. 2), and a linear strip antenna element 10 is formed on the other side from the aforementioned microstrip line 12. A window is formed by removing the ground conductor around the window so that it is formed at a slightly distant position.

The linear strip antenna element 10 is excited by a microstrip line and efficiently radiates a frequency determined by its length.

On the other hand, the window 14 is excited by the microstrip line 12 and radiates unnecessary electromagnetic waves, but as described later, it is canceled out by the electromagnetic waves radiated from the window of the paired window-equipped strip antenna element, so the overall radiation is radiated. Therefore, the band of the strip antenna element can be expanded without unnecessary radiation.

Furthermore, since the window 14 and the strip antenna element 10 are formed on the same surface, the relative positional relationship between the window and the strip antenna element can be determined relatively easily and accurately. Therefore,
For example, even when experimentally determining the change in the characteristics of a windowed strip antenna element caused by the above-mentioned reflector, data with less variation can be obtained, resulting in good design efficiency.

Next, referring to FIGS. 3 and 4, FIGS. 3 and 4 show an example in which the printed antenna shown in FIGS. 1 and 2 is applied to a printed antenna for transmitting and receiving circularly polarized waves with a reflector. It shows. This printed antenna has the same structure as the previously described printed antenna, except that a slot antenna element 22 and a reflector 20 are added.

Slot antenna element 22 is formed by removing a portion of ground conductor 18. The slot antenna element 22 is λg/4〈λ
g is the wavelength of electromagnetic waves transmitted by the microstrip line
The strip antenna element 10 is placed at a position of
An electric field spatially shifted by 90' from the radiated electric field of is efficiently radiated at a frequency determined by the length of the slot antenna element 22. Furthermore, the excitation voltage that excites the strip antenna element 10 and the oscillating current that excites the slot antenna element 22 are as follows:
Since the phase is temporally shifted by 90°, the combined radiated electric field of the strip antenna element 10 and the slot antenna element 22 becomes a circularly polarized wave.

Furthermore, a reflector 20 is loaded at a position of approximately λ/4 (λ is the wavelength of the electromagnetic wave) behind the substrate, and the electromagnetic waves directly radiated from the multi-element and the electromagnetic waves reflected by the -degree reflector are As will be described later, better circularly polarized waves are emitted in a wider frequency band than in the conventional example, and the gain is also increased.

Next, referring to FIG. 5, FIG.
1 shows an entire example of a printed antenna for transmitting and receiving circularly polarized waves, which is configured using the printed antenna shown in the figure as a basic element (subunit).

The strip antenna element 10 and the slot antenna element 22 each have a wavelength of λ on one side of the microstrip line.
g (λg is the wavelength of electromagnetic waves on the microstrip line)
They are arranged along the line at intervals, and on the other side of the microstrip line, the strip antenna elements are similarly arranged with only the position of the strip antenna element being shifted by λg/2. As a result, the strip antenna elements 10 excited by the electric field radiate electromagnetic fields having the same phase in pairs placed across the line.

On the other hand, in a window excited by a magnetic field caused by an oscillating current on a microstrip line, the pairs placed across the line radiate electromagnetic fields of opposite phase, so they cancel each other out and eliminate unnecessary radiation as described above. , the band of the strip antenna element can be expanded.

Next, when the printed antenna of the present invention is configured by loading a reflector, the band for emitting good circularly polarized waves becomes wider,
It will also be explained that the gain also increases.

The thickness of the insulating substrate is h, the wave number of electromagnetic waves in the insulating substrate is ', the distance between the insulating substrate and the reflecting plate is R1, the wave number in air is k, and is shown in Figures 6A and 6B. Using a coordinate system with the X2 plane as the antenna plane, in the case of the printed antenna of the present invention, the combined radiated electric field of the strip antenna element 10 and the slot antenna element 22 is Eθ (θ φ) = Est (θ, φ) cos θ cos φ ×
sin[(k'h+kR)sinθsinφ]−Esl
(θ, φ) x sin φ sin [(k' h+kR)s
inθsinφ]−(1)Eφ(θ,φ)=−Est(
θ, φ) sin φ × sin [(k'h+ kR) sin
θsinφ]−Esl(θ2φ)x cos θco
s φsin[(k'h+kR)sinθsin
φ ] (2) The linear polarization component can be displayed.

Here, E st (θ, φ) represents the radiated electric field from the strip, and E sl (θ, φ) represents the radiated electric field from the slot.

When Eθ (θ, φ) and Eφ (θ, φ) are rewritten as the expression for circularly polarized wave components, ER (θ, φ) − 1/rf × (Eθ (θ, φ) + ”Eφ
(θ, φ)) ...<3> E, L (θ, φ)-1/flX(Eθ(θ, φ)jE
It can be expressed as φ(θ, φ)) ...(4). Here, ER (θ, φ) is the right-handed circularly polarized component,
Et, (θ, φ) are left-handed circularly polarized components and are jr7go.

In addition, the axial ratio AR, which indicates the quality of circularly polarized waves, is AR-IER (
θ, φ〉−EL(θ, φ)/IER(θ, φ)+EL(
θ, φ)1...(5), and the combined radiation power P is: P= (Eθ(θ, φ)+2+lφ(θ, φ))2(6
), so using this, we can calculate a certain angle (θ.

The characteristics of the antenna at the position φ) can be expressed.

Here, in order to see the influence of the reflector 20 at the position rIt (7 antennas in front) at θ=90", φ=90M), originally,
E st (θ, φ) and E s that vary with frequency
When l(θ, φ) is a constant, equations (5) and (6) become as shown in FIG.

In Fig. 7, fo is the frequency of electromagnetic waves at which the distance between the insulator substrate and the reflection plate is 7 degrees and 1/4 wavelength, and the dielectric constant of the insulator substrate is 2.5 and the thickness is 0.1 wavelength. There is.

On the other hand, in the case of the conventional printed antenna, only equations (1) and (2) are different, and the strip antenna element 2
4 and the slot antenna element 22 is Eθ(θ, φ)−Est(θ, φ)cosθcosφ×
5in(kRsinθsinφ)−Esl(θ,φ)s
inφ×sin [(k'h+kR) sin θ si
n φ ] −(1)'Eφ (θ,
φ)=-Est(θ, φ)sinφ×sin (
kRsin θsin φ)−Esl(θ, φ)
cos θx cos φsin [(kR)sin
θsin φ] −12)'.

When the combined radiated power and the axial ratio are determined from equations (1) and (2) under the same conditions as in FIG. 7, they are as shown in FIG. 8.

Referring to FIGS. 7 and 8, in FIG. 7, a gain increase of 3 dB (2 times) is obtained at the center frequency by the reflector, but in FIG. 8, a gain increase of approximately 22 dB (
However, only a gain increase of 1,66 times was obtained.

Furthermore, regarding the axial ratio, only one point in Figure 8 has a good axial ratio of 0 decibels, but in Figure 7, the axial ratio is 0 decibels regardless of the frequency, which is considered here. It can be seen that when the frequency characteristics of the radiated electric field of the strip conductor and the slot antenna element are changed, the band in which good circularly polarized waves are radiated becomes wider.

(Effects of the Invention) As described above in detail, the present invention provides a printed antenna with good design, wide frequency band, and high gain even when a reflector is loaded.

[Brief explanation of drawings]

FIG. 1 is an enlarged plan view of essential parts of a first embodiment of the printed antenna of the present invention. FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. FIG. 3 is an enlarged plan view of a main part of a second embodiment in which the printed antenna is applied to a circularly polarized wave transmitting/receiving printed antenna with a reflector. FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. FIG. 5 is a plan view showing the entire third embodiment in which the printed antenna of FIG. 1 is applied to a circularly polarized wave transmitting/receiving printed antenna. FIGS. 6A and 6B are a cross-sectional view and a coordinate system for explaining the characteristics of the printed antenna of the present invention. FIG. 7 is a characteristic diagram of the printed antenna of the present invention. FIG. 8 is a characteristic diagram of a conventional printed antenna for comparison with the characteristics of the printed antenna of the present invention. FIG. 9 is a plan view showing a conventional example of a printed antenna that radiates circularly polarized waves using a combination of linear elements. FIG. 10 is a plan view showing a pair of a conventional windowed strip antenna element and a slot element that form the bottom of the printed antenna of FIG. 9. FIG. 11 also shows the reflectors described later, FIGS. 9 and 10.
FIG. 2 is a cross-sectional view taken along line 11-11 in the figure. DESCRIPTION OF SYMBOLS 10... Strip antenna element (strip conductor), 12... Microstrip line, 14... Window, 16... Insulator substrate, 18... Ground conductor, 20... Reflector, 22...Slot antenna element, 24...Strip antenna element body). (Strip conductivity Figure 5 Figure A Figure B Figure Sheep Figure 0 Figure 1 Figure Figure f/f○ f/f. Procedural Amendment February 26, 1990 1, Indication of Case 1999 Patent Application No. 344229 2, Name of the invention Printed antenna 3, Relationship with the person making the amendment case

Claims (5)

[Claims] (1) In the printed antenna for microwave transmission and reception,
1. A printed antenna comprising: a window formed in a ground conductor provided on one surface of an insulating substrate; and a strip conductor formed as a strip antenna element within the window. (2) The printed antenna according to claim 1, further comprising a slot antenna element formed on the ground conductor in association with the strip conductor. (3) The printed antenna according to claim 1 or 2, wherein the microstrip line is provided on the other surface of the insulating substrate. (4) The printed antenna according to any one of claims 1 to 3, wherein the printed antenna forms a subunit, and a plurality of the subunits are provided on an insulating substrate. printed antenna. (5) The printed antenna according to any one of claims 1 to 4, wherein reflective plates are provided at intervals on the insulating substrate.