JPH0575284B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a parasitic element whose one side is short-circuited to a ground conductor (hereinafter, such a parasitic element is also referred to as a one-sided short-circuited parasitic element). By changing the length from the connection part with the ground conductor (hereinafter also referred to as the short-circuit surface), using a square or circular feeding element,
This invention relates to a microstrip antenna that generates circularly polarized waves through single-point feeding.

[Conventional technology]

FIG. 1 is a diagram showing an example of the configuration of a conventional microstrip antenna that generates circularly polarized waves by single-point feeding, where 51 is a radiating element of the microstrip antenna, 52 is a dielectric, and 53 is a dielectric. ground conductor,
54 represents a power feeding point.

The shape of the radiating element 51 is rectangular, and by making the ratio (a/b) between dimension a and dimension b shown in the figure smaller than 1, circularly polarized waves are generated in the Z-axis direction.

In order to generate circularly polarized waves with single point feeding, two orthogonal modes must exist, and these two
It is sufficient that the electric field vectors of the two radiation fields are spatially orthogonal, have the same amplitude, and have a phase of 90°.

In a microstrip antenna, by resonating two frequencies, the phase difference between them is 90°.
As a result, circularly polarized waves are generated.

Figure 2 shows the shape of the radiating element and feeding position for generating circularly polarized waves in a conventional single-point feeding microstrip antenna, where F indicates the feeding point. Two frequencies resonate, and both use a radiating element in the shape of a rectangle or a slightly modified rectangle.

In the same figure, those shown in a-1 to a-4 are:
Circularly polarized waves are realized by a rectangular radiating element having notches and protrusions on the radiating element, and the feeding point is located midway in the height direction in the figure.

b-1 to b-4 are examples in which feeding points are provided on diagonals, and the radiation elements are formed into protrusions, notches, and rectangular shapes. In the case of a rectangle, b-2, b-3
In this case, the feeding point is slightly off the diagonal line.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional microstrip antenna, the shape of the radiating element is not circular or rectangular, but is slightly modified. When the shape of the solar element is square or circular, there are no two resonant frequencies, so it is impossible to generate circularly polarized waves by feeding at one point.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microstrip antenna capable of generating circularly polarized waves with single-point feeding even with radiating elements having symmetrical shapes such as squares and circles.

[Means for explaining the problem]

According to the invention, the above objects are achieved by the means specified in the claims.

That is, it is well known that if the shape of the radiating element of a microstrip antenna is, for example, a square, orthogonal polarization consisting of two modes having the same phase is generated by feeding power to diagonally located points.

Circularly polarized waves are generated by creating a 90° phase difference between these two modes.

In the present invention, in order to create a 90° phase difference, parasitic elements short-circuited on one side are attached to the side of the microstrip antenna, and changes in susceptance are utilized by changing the length of these parasitic elements from the short-circuited surface. This gives a phase difference of 90°.

In addition, in order to improve the axial ratio of circularly polarized waves, as an implementation example, the end face of a square radiating element is installed not parallel to the short-circuit surface of the parasitic element, and when the radiating element is circular, the angle of ±45° It is also possible to supply power off-axis.

〔Example〕

FIG. 3 is a diagram showing the first embodiment of the present invention, in which a is a top view and b is a sectional view between a and a' shown in FIG.

In the figure, 1 is a square radiating element, 2 is a dielectric of a microstrip antenna, 3 is a ground conductor, 4 is a feeding point, 5 is a parasitic element with one side short-circuited, and 6
represents a power supply connector.

The parasitic elements 5 are installed every 90 degrees, and the lengths from the short-circuit surface of the opposing parasitic elements 5 are equal.
The length is different from that of the other parasitic element 5. The distance between the end surface of the radiating element 1 and the short-circuit surface is constant. The feeding point 4 is provided at one point on the diagonal of the square. At this time, if there is no parasitic element 5 or if the length of the parasitic element is l ₁ = l ₂ , no circularly polarized waves are generated.

Figure 4 shows an example of measuring conductance and susceptance when changing the length of the parasitic element from the short-circuit surface at 1560MHz. It can be seen that the conductance and susceptance change greatly by changing the length of the parasitic element. Recognize.

Here, when l ₁ and l ₂ in Fig. 3 are obtained from Fig. 4, for example, if l ₁ = 14 mm, the phase φ ₁ at this time is tan ^-1 (B ₁ /G ₁ )≒-58 in °, l ₂ = 22 mm
Then, φ ₂ = tan ⁻¹ (B ₂ /G ₂ )≒26°, and |φ ₁ −
When φ ₂ |=94°, a phase difference of approximately 90° occurs between the modes, and circularly polarized waves are generated.

However, if you just change the length of the parasitic element,
Although the phase changes, since G ₁ = G ₂ does not hold, the axial ratio of the circularly polarized wave deteriorates. As a method of controlling conductance to improve this axial ratio, it is also possible to make the radiating element of the microstrip antenna rectangular and to optimize the ratio of the vertical dimension to the horizontal dimension of the rectangle. be.

FIG. 5 is a diagram showing a second embodiment of the present invention.
a, 2a, 4a, 5a are 1, 2, 4,
It is the same as 5.

In this embodiment, in order to improve the axial ratio, the end face of the square radiating element 1a is not parallel to the short-circuit surface, but is slanted by an angle θ to provide a power distribution ratio, thereby controlling the conductance.

For this example, θ = 10°, l ₁ = 14 mm, l ₂ =
Figure 6 shows an example of measurement when the diameter is 22 mm.

The shaded area represents the axial ratio of circularly polarized waves, and the larger the width, the worse the axial ratio of circularly polarized waves.

As is clear from the figure, it can be seen that circularly polarized waves are generated satisfactorily in this example as well.

FIG. 7 is a diagram showing a third embodiment of the present invention,
1b, 2b, 4b, and 5b are the same as 1, 2, 4, and 5 in FIG. 3, respectively, and show an example in which the radiating element is circular.

In the figure, parasitic elements are attached every 90 degrees, the lengths of the opposing parasitic elements from the short-circuit surface are equal, and the lengths of the other parasitic elements are different. The distance between the end surface of the radiating element 1b and the short-circuit surface is constant. Microstrip antenna feed point 4
b is a, a' or b between the parasitic element,
Place it at a point on the axis b'.

FIG. 8 is a diagram showing a fourth embodiment of the present invention,
In order to improve the axial ratio of circularly polarized waves and change the conductance, the feeding point 4c is moved θ from the axes a and a'.
It's just shifted.

FIG. 10 shows a measurement example of the directivity of this example when θ=10°, and it can be seen that it has good characteristics.

〔Effect of the invention〕

As explained above, the use of the matrix strip antenna of the present invention has the advantage that even if the radiation element is square or circular, it is possible to easily generate single-point feeding circularly polarized waves.

[Brief explanation of the drawing]

Figure 1 shows an example of the structure of a conventional circularly polarized microstrip antenna with one point feeding, and Figure 2 shows the shape of the radiating element and feeding of the conventional circularly polarized microstrip antenna with one point feeding. A diagram showing the location,
FIG. 3 is a diagram showing the first embodiment of the present invention, FIG. 4 is a diagram showing an example of measurement of conductance and susceptance when the length of the parasitic element is changed, and FIG.
The figure shows a second embodiment of the present invention, and FIG. 6 shows an example of directivity measurement of the second embodiment of the present invention.
FIG. 7 is a diagram showing a third embodiment of the present invention, FIG. 8 is a diagram showing a fourth embodiment of the present invention, and FIG. 9 is an example of measuring directivity of the fourth embodiment of the present invention. FIG. 1, 1a, 1b...radiating element, 2, 2a, 2b
...Dielectric material of microstrip antenna, 3,
3a, 3b...ground conductor of microstrip antenna, 4, 4a, 4b, 4c...power feeding position,
5, 5a, 5b...One side short circuit parasitic element, 6...
Power supply connector.

Claims (1)

[Claims] 1. An unbalanced planar resonator consisting of a radiating element and a ground conductor facing each other with a dielectric plate thinner than the wavelength in between, and a conductor having a constant width surrounding the radiating element. A strip-shaped member is installed vertically, the lower edge of the strip-shaped member in the width direction is connected to the ground conductor, and the upper edge of the strip-shaped member in the width direction is provided with a plurality of conductor flat plates each having a smaller area than the radiating element. The parasitic elements of the parasitic elements are bent in the direction of the central axis of the unbalanced planar resonator without touching each other, and connected so that their surfaces are parallel to the radiating element, and the parasitic elements are connected to the end of the band-shaped member of the parasitic element. The distance from the connecting part to the tip of the parasitic element is such that there are different dimensions, and the distance is closer to the end than the center of the radiating element, and
A circularly polarized microstrip antenna characterized in that it is configured to feed power from a point that is approximately equidistant from each opposing end of an adjacent parasitic element when viewed from the side of the parasitic element. . 2. A patent in which four parasitic elements are arranged symmetrically on each axis of orthogonal coordinate axes, and the lengths of opposing parasitic elements from the connection part with the ground conductor of the parasitic elements are equal. A circularly polarized microstrip antenna according to claim 1. 3. The shape of the radiating element is square, and the end face of the radiating element is non-parallel to the ridge line at the connection portion between the upper edge of the band-shaped member in the width direction and the parasitic element, or The circularly polarized microstrip antenna according to item 2. 4. The radiating element is circular, the four parasitic elements are arranged at equal intervals on the orthogonal coordinate axes, are on the same plane as the orthogonal coordinate axes, have an angle of 45 degrees with the orthogonal coordinate axes, and are arranged at equal intervals on the orthogonal coordinate axes. Claim 1 or 2, wherein the feeding point is a point on the radiating element that is on a straight line passing through the intersection or has a certain angle with the straight line and is opposite to a point on the straight line passing through the intersection of the orthogonal axes. Circularly polarized microstrip antenna as described in .