JPH02164107A - Microstrip antenna - Google Patents

Abstract

PURPOSE:To make the distance between a feeder and an antenna element narrow and to make the size of the antenna small by forming a couple of branch lines having a prescribed offset length as straight lines extended in nearly a perpendicular direction with respect to the feeder within the width of antenna elements. CONSTITUTION:A crank shaped antenna element 5 consists of a couple of U shaped parts 53, 54 formed back to back whose aperture are directed opposite to each other, a couple of feeder side straight line parts 51, 52 prolonged in a direction to be connected to the antenna element from the feeder circuit 4 of the U shaped parts 53, 54 and other terminals, and a couple of straight line parts 55, 56 at the termination side. Moreover, the feeder circuit 4 branches the terminal of the feeder 42 linked with the feeding point 41 at the side of the antenna element 5 into two ways. The branch point is formed to a position of the antenna element 5 closer to any straight line part in a couple of feeder side straight line parts 51, 52 so as to differentiate the length of both the branches 43, 44. Thus, it is possible to form the feeder 42 and the antenna element 5 closely.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a planar antenna used for receiving satellite broadcasting, etc., and particularly relates to an improvement of a microstrip line antenna in which the antenna element is formed of a microstrip line. .

(Prior art) As shown in FIG. 7, a microstrip line antenna has a ground conductor (2) made of aluminum on the bottom surface of a dielectric substrate (1) made of Teflon, for example, and a ground conductor (2) made of aluminum on the top surface of the substrate. A copper strip line conductor (30) is formed into a predetermined pattern.

For example, as shown in FIG. 6, the strip line conductor (30) is connected to a power feeding circuit (
40), a crank-shaped antenna element (7) is attached to each output end of the
are repeatedly connected in series, and a patch element (6) is connected to each terminal antenna element.
(see 18).

FIG. 8 shows the shape of the stripline conductor of the antenna element (7) directly connected to the feeder circuit (40), and shows a pair of U-shaped parts (73) formed so that the openings face each other. ) ()4) and each U-shaped part (73) (74)
A pair of feeding side linear portions (71) ()2) extending from the end on the feeding circuit (40) side in the antenna element connection direction, and each U
A pair of terminal straight portions (75) (76) extending from the other end of the character portions (73) (74) in the antenna element connection direction.
).

The feed line (42) led from the feed point (41) branches into two branches, and the branch lines (48) and (49) connect to the antenna element (
7) A pair of sleeves! @Connected to the straight portions (71) and (72), respectively.

By the way, in a planar antenna, when each antenna element is excited in the same phase, it exhibits directivity perpendicular to the element formation surface, but there is a difference in the length of the feed line from the feed point to each antenna element ( It is known that if a phase difference is provided to the microwaves propagating through each antenna element by providing an offset), the main beam direction will be biased from the vertical direction, and the directivity can be controlled by this ( NHK
TL Ho monthly report, June 1988 issue p185-p188%
(see).

Such a beam tilt type planar antenna has the advantage that the planar antenna can be attached closely to the wall of a building.

(Problem to be solved) In the beam tilt type planar antenna, the length of the pair of branch lines (48) and (49) from the feeder line (42) to the antenna element (7) shown in FIG. A desired beam tilt angle can be achieved by providing a predetermined difference (offset length) between J5 and J2.

For example, on a Teflon 11 dielectric substrate with a thickness of 0.8,
In a microstripline antenna equipped with a stripline conductor with a characteristic impedance of 50Ω, in order to set the antenna element spacing shown in Figure 8 to 12.5mm = beam tilt angle of 30°, use the side-look antenna described below. According to the design formula, the offset length is 4.2 wheels -
It is necessary to set it to .

However, as shown in FIG. 8, in the conventional antenna, the pair of straight portions (71) on the feeding side of the antenna element (7) (
72) is as narrow as 6.2 m, for example, and the feeder line (42) and antenna element (7) must be placed as close as possible due to the demand for smaller antennas.
The branch point of the feed line (42) and the pair of feed-side straight portions (71) (72) of the antenna element (7) face each other with a small distance therebetween. Therefore, both branch lines (48
) To provide an offset length of, for example, 4.2 mm to (49), the routes of branch lines (48) and (49) are greatly curved outward, and then both branch lines (48) and (49) are It is necessary to provide a difference of 4.2 mm in length.

However, the microstrip line has a predetermined width W (approximately 21
), the feed line (42) and the antenna element (
7) It is actually impossible to curve the route of the branch line while maintaining a small distance from the branch line.

That is, in a conventional microstrip line antenna, in order to give the main beam a predetermined directivity, the feed line (4
2) and the antenna element (7) must be formed sufficiently apart, and a pair of branch lines (48) and (49) having a predetermined offset length must be provided in the space created thereby.

As a result, there is a problem in that the area occupied by the feeder circuit (40) increases and the antenna becomes larger.

An object of the present invention is to provide a microstrip line antenna that can provide a desired offset length without increasing the size of the feeder circuit.

(Means for Solving the Problems) In the microstrip line antenna according to the present invention, the crank-type antenna element (5) has a pair of U-shaped elements formed back to back with openings in opposite directions. (53) (54) and each U-shaped portion (53) (5
4) from the other end of the pair of feeding side linear parts (51) (52) extending in the antenna element connection direction from the end on the feeding circuit (4) side, and each of the U-shaped parts (53) (54). A pair of terminal side straight portions (55) (5) extending in the antenna element connection direction.
6).

In addition, the feed circuit (4) branches the end of the feed line (42) connected to the feed point (41) on the antenna element (5) side into two, and each branch line (43) (4,4) Antenna element (5)
The branch point of the feed line (42) is connected to the pair of feed side straight portions (51) (52) of the antenna element (5), respectively. The branch lines (43) and (44) have different lengths.

(Function) As shown in Fig. 3, the feed-side straight parts (51) and (52) of the antenna element (5) to be connected to the feed circuit (4) extend at intervals corresponding to the total width of the antenna element (5). Therefore, when designing the route of the branch line (43) (44) extending from the branch point of the feeder line (<42) to the both room line sections (51) and (52), it is necessary to Feed t@straight section (51) (52)
By simply connecting them with a straight line, a branch line (43) (44) longer than the conventional one can be formed, and along with this, the feed line (
By simply shifting the branch point H1 of 42) to a position biased toward one of the power feeding side straight portions, it is possible to set the offset length according to the amount of shift.

<Effects of the Invention> According to the microstrip line antenna according to the present invention, a pair of branch lines (43) having a predetermined offset length
(44) can be formed in a straight line extending approximately perpendicularly to the feed line (42) within the width region of the antenna element (5), so that the distance between the feed line (42) and the antenna element (5) is It is possible to make the antenna narrower than before, and thereby the antenna can be made smaller.

(Example) Hereinafter, an example in which the present invention is implemented in a receiving antenna with a center frequency of 12 GHz will be described.

It should be noted that the examples are for illustrating the present invention, and should not be construed as limiting the invention described in the claims or reducing its scope.

As shown in Figure 2, an aluminum ground conductor (2) is formed on the bottom surface of a 0.8 mm thick Teflon dielectric substrate (1), and a copper strip line conductor (2) is formed on the top surface of the substrate. 3) is formed into a predetermined pattern.

The strip line conductor (3) is connected to the feed point <
A crank-shaped antenna element (5) is repeatedly connected in series to each output end of the feeder circuit (4) that branches off from 41), and a batch element (6) similar to the conventional one is connected to the terminal antenna element. This is what I did.

As shown in FIG. 3, each antenna element (5) consists of a pair of U antennas formed back to back so as to open in opposite directions.
and each U-shaped portion (53) (54).
4) from the other end of the pair of feeding side linear parts (51) (52) extending in the antenna element connection direction from the end on the feeding circuit (4) side, and each of the U-shaped parts (53) (54). A pair of terminal side straight portions (55) extending in the antenna element connection direction (
56).

The dimensions of each part shown in the figure are, for example, as specified in the Technical Report of the Television Society Vol. 1.10. No, 44. It can be determined using the method proposed in p13 to p18.

Here, the width W of the microstrip line is 21II
I, the length A of the lower U-shaped part (54) is 14.6 - ring;
The width C of the upper U-shaped part (53) is 6.3 mm, and the height B of both U-shaped parts is 6.3.
and the center distance of the lower U-shaped part (54) is 12.5me.
i, center distance 11iE of both U-shaped parts (53) (54) is 6.21, taper part (45) of branch line (43) (44)
) The length T of (46) is 3°31, and the length (offset length) L of the straight part extending from the end of the tapered part is 4.2eb.
+s, the radius R of the circular arc portion formed at the end of the branch line (43) <44) is 3 mm.

The offset lengths of the branch lines (43) and (44) are selected to satisfy the following side-look antenna design formula.

KoDsinθ=β. L Here, β0 is the phase constant within the microstrip line, D is the antenna element spacing shown in FIG. 3, θ is the desired beam tilt angle, and Ko is the wave number in air.

This formula shows that when multiple antenna elements are arranged in a straight line at a constant pitch, the phase difference between the microwaves reaching each antenna element and the phase of the microwaves radiated from each antenna element match. It is a formula derived from the relationship with the radiation direction (for example, "antenna engineering") written by Endo, Sato, and Nagai,
General Electronic Publishing, see pages 46-47).

When setting the beam tilt angle θ to 30°, substituting the above formula % 0.37m+@-' gives L=4.2mm, and the power supply circuit (4) is as shown in Figure 5. The microstrip line led from the feeding point (41) is branched into two branches one after another, and the antenna element (5
), and each feeder line (42) is branched into two to form a pair of branch lines (4Z).
43) (44) are connected to a pair of feeding-side straight portions of each antenna element (5), respectively.

The difference in length between the branch lines (43) and (44) at the branch point H2 closest to the antenna element (5) is set to the offset length obtained by the above design formula, and the length of the branch line at the next branch point H2 is set to the offset length obtained by the above design formula. The difference is 2L, and then the next branch point H3
The difference in length between the branch lines at is set to 4L.

This allows each antenna element (5
) The length of each line leading to the feeding side straight section is different by the offset length for each pair of adjacent straight sections, and the length of each line leading to the feeding side straight section of A phase difference corresponding to the offset length is given to each wave.

As a result, as shown in Figure 2, if the connection direction of the antenna element (5) is the X axis, the direction perpendicular to the antenna surface is the two axes, and the direction perpendicular to the X and Z axes is the Y axis, the main beam The direction M is offset by θ=30° with respect to the Z axis in the YZ plane.

In the feeder circuit (4) in Figure 3, a pair of tapered portions (45) and (46) are formed to achieve impedance matching between the feeder line (42) and the branch lines (43) and (44). Therefore, the offset length is limited to 4.21.

In Figure 4, in order to provide an even longer offset length, impedance matching was achieved by adopting the so-called transformer type branching method (see "Microwave Engineering Fundamentals and Principles" by Masamitsu Nakajima, Morikita Publishing, p.97-p.98g). An example is shown.

As shown in the figure, a wide portion (47) having a width Wl of 3, a jet length G of 1/4 of the line wavelength λg, and a characteristic impedance of 35.4Ω is provided at the end of the feeder line (42). Other dimensions are the same as in FIG.

In this case, the maximum value F of the offset length is 7. ．． 8mm, and the beam tilt angle corresponding to the offset length is 68.
It becomes 4°.

For example, the receiving angle of satellite broadcasting in Japan is 29° to 58°.
According to the microstrip line antenna shown in FIG. 4, it is possible to receive satellite broadcasting at an optimal beam tilt angle in various locations.

The repeating pattern of the antenna element (5) in Fig. 1 is as follows:
If the repetition period is shifted by half a period, it matches the conventional antenna pattern shown in FIG. 6, so it is clear that the microstrip line antenna of the present invention can also provide the same transmission and reception characteristics as the conventional antenna pattern.

According to the microstrip line antenna shown in FIGS. 1 to 4, the branch lines (43) (44) are
Since it can be formed in a straight line orthogonal to 2), it is possible to form the feed line (42) and the antenna element (5) as close as possible, thereby reducing the size of the antenna. I can do it.

The drawings and the description of the above embodiments are for illustrating the present invention, and do not limit the invention described in the claims.
Nor should it be construed as limiting the scope.

Further, it goes without saying that the configuration of each part of the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the technical scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a microstrip line antenna according to the present invention, and FIG. 2 is a perspective view showing the main parts of the antenna.
Fig. 3 is an enlarged plan view showing the main parts of the feeder circuit and the pattern of the antenna element, Fig. 4 is an enlarged plan view similar to Fig. 3 showing another embodiment, and Fig. 5 is the overall pattern of the feeder circuit. 6 is a plan view of a conventional microstrip line antenna, FIG. 7 is a perspective view showing the main parts of the antenna, and FIG. 8 is an enlarged plan view showing the main parts of the feeding circuit and the pattern of the antenna element. It is. (3)...Strip line conductor

Claims (1)

[Claims] [1] A ground conductor (2) and a stripline conductor (3) are formed on both sides of the dielectric substrate (1), and the stripline conductor (3) is connected to a power supply circuit (branching and extending from a power supply point (41)). 4) At each output end, a crank-type antenna element (
5) are repeatedly connected in series, the crank-type antenna element (5) consists of a pair of U-shaped parts formed back to back so as to open in opposite directions. (53), (54), and a pair of feed-side linear portions (51) and (52) extending from the end of each U-shaped portion (53) and (54) on the feed circuit (4) side in the antenna element connection direction; The feeding circuit (4) is composed of a pair of terminal side straight portions (55) (56) extending from the other end of each U-shaped portion (53) (54) in the direction of the antenna connection element, and the feeding circuit (4) has a feeding point ( The antenna element (5) side end of the feed line (42) connected to the antenna element (5) is branched into two, and each branch line (43) (44) connects to the pair of feed side straight portions (51) of the antenna element (5). ) (52), respectively, and the feeder line (
The branch point 42) is provided at a position biased toward one of the pair of feed side straight parts (51) (52) of the antenna element (5), and is located at a position biased toward one of the straight parts (51) (52) on the feeding side of the antenna element (5). A microstrip line antenna characterized by realizing a predetermined directivity by varying the length.