JP3145532B2 - Microstrip antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna incorporated in a portable radio device or the like, and more particularly, to a structure of a microstrip antenna capable of easily manufacturing an antenna having uniform characteristics without requiring high working accuracy. According to.

[0002]

2. Description of the Related Art FIG. 15 is a view showing an example of the configuration of a conventional microstrip antenna, wherein FIG.
(B) is a side view, and (c) is a bottom view. In the figure, 39 is an antenna radiating element, 40 is a dielectric plate, 4
1 denotes a ground conductor, 42 denotes an outer conductor of a coaxial line, 43 denotes an inner conductor of a coaxial line, and 44 denotes a feeding point of the antenna radiating element 39. In a conventional microstrip antenna in which the antenna radiating element 39 is fed by a coaxial line as shown in this figure, a ground conductor 41, a dielectric plate 40, and a hole penetrating the antenna radiating element 39 are provided, and The outer conductor 42 is soldered to the ground conductor 41 and the inner conductor 4
Reference numeral 3 denotes a configuration in which the antenna 3 is soldered to the antenna radiating element 39 through a hole passing through the dielectric plate 40 and the antenna radiating element 39.

FIG. 16 is a diagram showing an example of the configuration of a portable radio device incorporating the conventional microstrip antenna as described above, and reference numeral 45 denotes a housing of the portable radio device. In a conventional portable wireless device having such a configuration, when the wireless device is in an upright state, the microstrip antenna operates as a vertically polarized antenna.

[0004]

As described above, the power supply of the conventional microstrip antenna relies on a coaxial line. Therefore, holes are formed through the ground conductor, the dielectric plate, and the antenna radiating element. Since the method of soldering the outer conductor of the coaxial line to the ground conductor and soldering the inner conductor to the antenna radiating element through this hole is adopted, the number of manufacturing steps increases.

Since the input impedance characteristic of the microstrip antenna changes depending on the position of the feed point 44, the position of the feed point 44 must be set accurately. Therefore, it has been very difficult to produce an antenna with many characteristics.

As described above, the conventional microstrip antenna requires many manufacturing steps and requires high manufacturing accuracy, so that it is difficult to manufacture an antenna having uniform characteristics, and it is inferior in mass productivity. Had problems.

[0007] Looking at a portable radio equipped with such an antenna, as shown in FIG. 17, the portable radio is held by a user's hand 46 and held on a human head 47 in an actual call state. It is used by being tilted from the vertical direction.

Accordingly, the polarization characteristic of the antenna becomes directional not only for vertical polarization but also for horizontal polarization.
The antenna effective gain decreases. FIG. 18 shows a change in the antenna effective gain with respect to the inclination angle of the portable wireless device housing. As is apparent from FIG.
In the case of °, the effective gain is reduced by about 10 dB.

As described above, the conventional portable wireless device has a problem that the polarization characteristic of the antenna fluctuates depending on the use conditions and the effective gain of the antenna changes.

The present invention has been made to solve such a conventional problem, and provides a microstrip antenna in which uniform characteristics can be easily obtained without requiring high manufacturing accuracy. In addition, when this is mounted on a portable radio, when the portable radio is actually used, the structure is such that the effective gain does not decrease even if the portable radio is tilted.
It is intended to realize a microstrip antenna.

[0011]

According to the present invention, the above-mentioned object is solved by the means described in the claims.

That is, in the first aspect of the present invention, the antenna radiating element is attached to one surface, and the strip line is attached to the other surface, and the strip line and the antenna radiating element are connected by a conductor. A first dielectric plate and a second dielectric plate having a strip line attached to one surface and a ground conductor attached to the other surface, each having a strip line of the dielectric plate; The microstrip antenna is disposed close to each other so as to face each other, and the stripline on the first dielectric plate and the stripline on the second dielectric plate are electromagnetically coupled.

According to a second aspect of the present invention, in the above-mentioned antenna, the first dielectric plate is formed by an electromagnetic coupling between a strip line on the first dielectric plate and a strip line on the second dielectric plate. The rotation center axis is provided at a position deviated from the position of the center of gravity of the first dielectric plate while maintaining the proper coupling.

[0014]

The microstrip antenna of the present invention has a first
The antenna radiating element provided on the dielectric plate and the strip line provided on the rear surface thereof are connected by a conductor, and the strip line and the strip line provided on the second dielectric plate are partially connected to each other. It is configured to be electromagnetically coupled by overlapping or crossing.

Therefore, power supply to the antenna radiating element is performed in the following path: "strip line on the second dielectric plate → electromagnetic coupling → strip line on the first dielectric plate → connecting conductor → antenna radiating element". .

According to the present invention, since such a structure is used, an antenna can be manufactured only by simple bonding without performing perforation or soldering required for feeding power by a coaxial line. .

Further, since the input impedance characteristics do not greatly change even if the two strip lines are not accurately aligned, an antenna having uniform antenna characteristics can be obtained, which is excellent in mass productivity.

According to the second aspect of the present invention, the first dielectric plate having the antenna radiating element has a rotatable structure, and has a center of gravity outside the center of rotation, so that the surface of the dielectric plate can be rotated. Rotates so that the position of the center of gravity is on the lower side, and always keeps the antenna radiating element in a constant state. Therefore, when the portable wireless device is used, the predetermined polarization characteristic of the antenna radiating element can be maintained even if the inclination angle of the portable wireless device changes.

[0019]

1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a front view, FIG. 1B is a side view, and FIG. 1C is a bottom view. ), (B), and (c) are the same in the case of "FIG. 4" to "FIG. 7" described later).

In FIG. 1, reference numeral 1 denotes a first dielectric plate, 2 denotes a second dielectric plate, and 3 denotes an antenna radiating element made of a metal coating adhered to the surface of the first dielectric plate 1. Is a first dielectric film made of a metal film adhered to the back surface of the first dielectric plate 1.
5 is a second strip line made of a metal coating applied to the surface of the second dielectric plate 2, and 6 is made of a metal coating applied to the back surface of the second dielectric plate 2. Represents a ground conductor.

Reference numeral 7 denotes a third dielectric plate provided between the strip line 4 provided on the back surface of the first dielectric plate 1 and the strip line 5 provided on the surface of the second dielectric plate 2. And is inserted for ensuring the stability of the dielectric plate 1.

Further, reference numeral 8 denotes an antenna radiating element 3 made of a metal coating adhered to the surface of the first dielectric plate 1;
A metal conductor 9 for connecting the first strip line 4 made of a metal film adhered to the back surface of the dielectric plate 1 denotes an antenna plug.

The first strip line 4 is disposed above the second strip line 5 so that the two strip lines partially overlap when viewed from the direction perpendicular to the dielectric plate. The high-frequency current input from the plug 9 propagates through the second strip line 5 and induces a high-frequency current in the first strip line 4 by electromagnetic coupling.

Further, the high-frequency current induced in the first strip line 4 is supplied to the antenna radiating element 3 by the metal conductor 8 connecting the first strip line 4 and the antenna radiating element 3. By setting the element length of the antenna radiating element 3 to an electrical length of about の of the resonance wavelength in consideration of the dielectric constant of the dielectric plates 1, 2 and 7, resonance can be obtained in a desired frequency band.

FIG. 2 shows the return loss characteristics of the antenna of this embodiment, and it can be seen that good resonance characteristics are obtained. FIG. 3 is a diagram showing the radiation directivity of both vertical (Eθ) and horizontal (Eφ) polarizations in the horizontal plane of this embodiment. The antenna radiating element 3 is connected to the second strip line 4 via the metal conductor 8. It is understood that the antenna radiating element 3 is operating as an antenna having a main polarization in the longitudinal direction of the first strip line 4 because the power is supplied to the first strip line 4. Then, a directivity gain of about 2.0 dBd at the maximum is obtained, and it can be seen that good radiation characteristics are realized.

In the microstrip antenna of the present embodiment, as described above, the first strip line 4 and the second strip line 5 are electrically connected by electromagnetic coupling. The input impedance characteristic can be easily maintained without performing the measurement accurately.

Further, the first dielectric plate 1 can be easily removed, and the two lines are electromagnetically coupled even if the intersection angle between the first strip line 4 and the second strip line 5 changes. Therefore, even when the polarization characteristics are different depending on the installation location of the antenna, by manually changing the mounting angle of the first dielectric plate, the polarization characteristics of the antenna are adjusted so as to have sensitivity to the desired polarization. Can be changed.

In this embodiment, the case where the shape of the antenna radiating element 3 is square is shown, but the same antenna characteristics can be obtained even when the shape of the antenna radiating element 3 is rectangular or circular. Further, in this embodiment, the case where the shape of the dielectric plate 2 is a square is shown, but the shape of the dielectric plate 2 is not limited to a square, and the present invention can be applied to the case of a rectangle or a circle. Needless to say, The same applies to the other embodiments described below.

FIG. 4 is a view showing a second embodiment of the present invention, in which a metal conductor 8 connecting the antenna radiating element 3 and the first strip line 4 described in the first embodiment is passed through. It is constituted by a hole 10. In this case, in the antenna radiating element 3, the through hole 10
By changing the position, the input impedance characteristics viewed from the antenna plug 9 can be adjusted, and the antenna can be operated in the best condition.
A similar configuration can be adopted even if a metal pin is used instead of the through hole 10.

FIG. 5 is a view showing a third embodiment of the present invention. In the figure, 1 is a first dielectric plate, 2 is a second dielectric plate, 3 is an antenna radiating element made of a metal coating adhered to the surface of the first dielectric plate 1, and 4 is a first dielectric plate. A first strip line 5 made of a metal film adhered on the back surface of the dielectric plate 1 of the first embodiment, a second strip line 5 made of a metal film adhered on the surface of the second dielectric plate 2, and 6 A ground conductor made of a metal film adhered to the back surface of the second dielectric plate 2 is shown.

Reference numeral 7 denotes a dielectric plate provided between the strip line 4 provided on the back surface of the first dielectric plate 1 and the strip line 5 provided on the surface of the second dielectric plate 2. Are inserted to ensure the stability of the dielectric plate 1.

Further, reference numeral 8 denotes an antenna radiating element 3 made of a metal film adhered on the surface of the first dielectric plate 1;
A metal conductor for connecting a first strip line 4 made of a metal film adhered to the back surface of the dielectric plate 1; 9, an antenna plug; 11, a tip of the second strip line 5, 12
Is an arc-shaped third strip line connected to the end portion 11 of the second strip line 5, 13 is an end portion of the third strip line, and 14 is connected to an end portion 13 of the third strip line 12. , A fourth strip line 15 having an electrical length of about の of the resonance wavelength, and 15 represents the tip of the fourth strip line 14.

Since the present embodiment has such a configuration, the high-frequency current input from the antenna plug 9 is applied to the second strip line 5 and the third strip line 12.
And is reflected at the tip 15 of the fourth stripline 14. Since the element length of the fourth strip line 14 is set to an electrical length that is approximately 波長 of the resonance wavelength, the amplitude of the standing wave current in the third strip line 12 becomes maximum.

Since the first strip line 4 is disposed above the third strip line 12, a high-frequency current is induced in the first strip line 4 by electromagnetic coupling. Since the amplitude of the standing wave current is maximized in the line 12, strong electromagnetic coupling is obtained.

Further, the high-frequency current propagated through the first strip line 4 is transmitted to the antenna radiating element 3 by the first strip line 4 and the metal conductor 8 connecting the antenna radiating element 3.
Power is supplied to The element length of the antenna radiation element 3 is about 1 of the resonance wavelength in consideration of the dielectric constant of the dielectrics 1, 7 and 2.
By setting the electrical length to / 2, it is possible to resonate in a desired frequency band, and it is possible to obtain radiation directivity substantially similar to the radiation directivity shown in FIG.

FIG. 6 is a diagram showing an example of a configuration in which the arc-shaped strip line 12 in FIG. 5 is replaced by a short linear strip line 16. Even in such a configuration, the arc-shaped strip line 12 is used. Approximately the same antenna characteristics as in the case of using.

In FIGS. 5 and 6, an arc-shaped strip line 12 or a short strip line 16 is connected to the strip line 5 provided on the surface of the dielectric plate 2, and furthermore, the electric power of about 1/4 of the resonance wavelength is obtained. Although the configuration is such that the strip line 14 having a long length is connected, such a configuration can be applied to the strip line 4 provided on the back surface of the dielectric plate 1.

FIGS. 7A and 7B are views showing a fourth embodiment of the present invention, wherein FIG. 7A is a front view, FIG.
(C) has shown the CC sectional view. This also applies to “FIG. 9” and “FIG. 13” described later. This shows an example of a configuration in the case where the second strip line 5 and the fourth strip line 14 in the third embodiment are triplate lines.

In the figure, reference numeral 17 denotes a fourth dielectric plate disposed above the second strip line 5, 18 denotes a second ground conductor disposed above the fourth dielectric plate 17, and 19 denotes a second ground conductor.
A fifth dielectric plate 20 disposed above the ground conductor 18 of FIG.
Represents a metal conductor connecting the third strip line 12, the second strip line 5, and the fourth strip line 14 through a small hole provided in the second ground conductor 18.

Since the present embodiment has such a configuration, it is possible to eliminate the influence of the mutual coupling between the second strip line 5 and the fourth strip line 14 and the antenna radiating element 3. Good resonance characteristics can be obtained.

The power supply by the triplate line described in the present embodiment can be similarly applied to the antenna structures of the above embodiments. FIG. 8 is a view for explaining the fifth embodiment of the present invention, and shows an example of the shape of the antenna radiating element 3 which can be used in the present invention (in this figure, in order to clarify the shape). The antenna radiating element is shown with diagonal lines).

In FIG. 8A, reference numeral 21 denotes a slot provided in the antenna radiating element 3. As described above, by changing the length, width, and installation position of the slot 21, the resonance frequency of the antenna can be reduced without changing the dimensions of the antenna radiating element 3. Therefore, it is effective for downsizing the antenna.

In FIG. 8B, reference numeral 22 denotes a notch provided in the antenna radiating element 3. Thus, even if the notch 22 is provided in the antenna radiating element 3, similarly to the slot,
The resonance frequency of the antenna can be reduced without changing the dimensions of the antenna radiating element 3.

In FIG. 8C, reference numeral 23 denotes a strip line provided on the surface of the dielectric plate 1, and reference numeral 24 denotes a strip line provided on the back surface of the dielectric plate 1 by the strip line 23 provided on the surface of the dielectric plate 1. 4 is a notch provided so as to be located at the upper part of FIG. By adjusting the length of the notch 24, the input impedance characteristics viewed from the antenna plug 9 can be optimized, so that good resonance characteristics can be obtained.

FIG. 8D shows an example of a configuration in which the parasitic element 25 is attached to the surface of the dielectric plate 1.
The element length of the antenna radiating element 3 is the dielectric plates 1, 2 and 7.
The resonance can be obtained in a desired frequency band by setting the electrical length to about 1/2 of the resonance wavelength in consideration of the dielectric constant of the above.

The parasitic element 25 is set at a resonance wavelength different from that of the antenna radiating element 3, and a current is induced on the parasitic element 25 via the antenna radiating element 3 at a frequency corresponding to the resonance wavelength. Is done. That is, an antenna radiating element operating at two different frequencies can be formed.

Such two resonance of the antenna radiating element by the parasitic element can be similarly applied to the antenna structure of each of the above embodiments. FIG. 9 is a view showing a sixth embodiment of the present invention.
, 27 is an antenna rotation axis provided on the first dielectric plate 1, 28 is an antenna rotation axis support provided on the surface of the second dielectric plate 2, 29 is an antenna cover made of a dielectric material Reference numeral 30 denotes an antenna rotating shaft support provided on the back surface of the antenna cover 29.

The antenna rotation shaft 27 provided on the first dielectric plate 1, the antenna rotation shaft support 28 provided on the second dielectric plate 2, and the antenna rotation shaft support 30 provided on the back of the antenna cover 29 However, the first dielectric plate 1 is superimposed on the second dielectric plate 2 so as to match each other, and the antenna cover 29 is further superimposed on the first dielectric plate 1.

As described above, the antenna radiating element 3 can freely rotate 360 ° about the antenna rotating axis 27 by providing the weight 26 and the antenna rotating axis 27 on the dielectric plate 1.

As shown in FIG. 10, when this antenna is mounted on a portable radio and used, the dielectric plate 1 has a weight 9
Rotate upright and stand upright. In the figure, reference numeral 2 denotes a dielectric plate of the antenna, and reference numeral 45 denotes a portable wireless device housing, and shows a state where the portable wireless device housing 45 is upright.

At this time, since the portable radio is upright, the weight 26 is located at the lower end of the antenna due to gravity, whereby the antenna radiating element 3 has sensitivity to vertical polarization. FIG. 11 shows a state in which the portable wireless device is actually used, in which 46 indicates a user's hand, and 47 indicates a human head of the user. At this time, the portable wireless device housing 45 is inclined obliquely beside the user's head 47, but the antenna radiating element 3 is rotated by the weight 26 about the antenna rotating shaft 27 as the rotation center, and is shown in FIG. Move in a direction that is sensitive to vertical polarization.

That is, in the embodiment shown in FIG. 9, even if the inclination angle of the portable radio device fluctuates artificially due to the use conditions, the antenna radiating element 3 always moves so as to have sensitivity to vertical polarization. Since the polarization characteristics are maintained, the antenna effective gain can be kept constant.

FIG. 9 shows a case where the antenna rotation axis is provided on the strip line 4 provided on the back surface of the dielectric plate 1 and is provided at a position where the length of the strip line 4 in the longitudinal direction is bisected. However, when the axis of rotation of the antenna is on the strip line 4 provided on the back surface of the dielectric plate 1 or on an extension of the strip line 4, and is provided so as to be shifted from a position where the length of the strip line in the longitudinal direction is divided into two. However, exactly the same antenna characteristics can be obtained.

FIG. 12 is a view for explaining a seventh embodiment of the present invention. In the structure in which the dielectric plate having the antenna radiating element described above with reference to FIG. It is what showed the example of the support method variously as sectional drawing. FIG. 11A shows an example of a configuration in which the antenna rotation axis 27 in the sixth embodiment is replaced with an antenna rotation axis 31 penetrating the dielectric plate 1. In FIG. 2B, reference numeral 32 denotes an antenna rotation axis provided on the back surface of the dielectric plate 1;
Reference numeral 33 denotes an antenna rotating shaft support provided on the dielectric plate 2.
3 is a configuration example in the case where the diameter of No. 3 is not uniform.

With such a configuration, the antenna radiating element 3 can be provided no matter what angle the dielectric plate 2 is inclined.
Is maintained at a certain distance from the dielectric plate 2 without separating from the dielectric plate 2, and the antenna radiating element 3 is
Can rotate 0 °. Also, this configuration does not necessarily require an antenna cover.

FIG. 9C shows the dielectric plate 2 in FIG.
Is provided on the surface of the feeder line 5, and the same effect as in the above embodiment can be obtained. 3D, reference numeral 34 denotes an antenna rotation axis provided on the surface of the dielectric plate 1, and reference numeral 35 denotes an antenna rotation axis support provided on the back surface of the antenna cover 29. The antenna rotation axis 34 and the antenna rotation axis support are provided. This is a configuration example in the case where the diameter of 35 is not uniform.

With this configuration, the antenna radiating element 3 keeps a constant distance from the dielectric plate 2 without detaching from the antenna cover 12 regardless of the angle of the dielectric plate 2 at any angle. , Antenna radiating element 3 is 360 °
Can rotate.

The power supply line 5 provided on the surface of the dielectric plate 2
Since the antenna rotation axis is not provided between the power supply line 4 provided on the back surface of the dielectric plate 1 and the antenna rotation axis, the antenna rotation axis does not hinder electromagnetic coupling, and good resonance characteristics can be obtained.

In FIG. 12E, reference numeral 36 denotes the dielectric plate 1.
The antenna rotating shaft support portion 37 provided inside the above-mentioned is a holding member for the dielectric plate 1. By providing the holding member 37 on the antenna rotating shaft 31 in this manner, the distance between the dielectric plate 1 and the dielectric plate 2 can be kept constant, so that the antenna rotating shaft is attached to the antenna cover or the dielectric plate 2. Even if fixed, the dielectric plate 1 can rotate 360 °.

FIG. 13 is a view for explaining an eighth embodiment of the present invention. Reference numeral 38 denotes a dielectric plate in which the shape of the first dielectric plate is T-shaped. FIG. 10 shows an embodiment in which the shape of the dielectric plate 1 in FIG. 9 is different from the shape of the antenna radiating element 3.

With this configuration, the dielectric plate 38 itself operates like a pendulum, so that the dielectric plate 1 can freely rotate 360 ° about the antenna rotation axis 27 without providing a weight. can do.

The configuration of the antenna radiating element shown in this embodiment can be similarly applied to the antenna structures of the above embodiments. FIG. 14 is a view for explaining the ninth embodiment of the present invention, and shows an example of a method of arranging weights in the configuration like the embodiment shown in FIG. ~
For each of (e), the front view is on the left and B is on the right.
-The structure is shown by arranging a sectional view along line B. FIG. 3A shows a case where a weight is provided inside the dielectric plate 1, which is described in the above embodiment. FIG. 3B shows the weight 26 provided on the surface of the antenna radiating element 3. In addition, weight 26
May be provided on the back surface of the dielectric plate 1. (C) shows a configuration in which a plurality of weights 26 are provided on the surface of the antenna radiating element 3. Further, a plurality of weights 26 can be provided on the back surface of the dielectric plate 1. (D) and (e) show that the weight 26 is provided on the side surface of the dielectric plate 1.

The structure of the weight shown in this embodiment can be applied to all the antenna structures requiring a weight in the above-mentioned embodiment.

[0064]

According to the present invention, a microstrip antenna having uniform antenna characteristics can be easily realized. In addition, there is an advantage that it does not require delicate adjustment or the like in manufacturing, and can be superior in mass productivity.

According to the second aspect of the present invention, when the antenna is mounted on an actual portable radio, the polarization characteristics of the antenna can be kept constant even when the portable radio is used in an inclined state. , And a stable effective gain can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a return loss characteristic of the antenna of the present invention.

FIG. 3 is a diagram showing both vertical and horizontal polarization radiation directivities of the present invention.

FIG. 4 is a diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is a diagram showing another example of the third embodiment of the antenna according to the present invention.

FIG. 7 is a diagram showing a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a fifth embodiment of the present invention.

FIG. 9 is a diagram showing a sixth embodiment of the present invention.

FIG. 10 is a diagram showing an example of mounting the antenna of the present invention on a portable wireless device.

FIG. 11 is a diagram illustrating a state in which a portable wireless device equipped with the antenna of the present invention is used.

FIG. 12 is a diagram showing a seventh embodiment of the present invention.

FIG. 13 is a diagram showing an eighth embodiment of the present invention.

FIG. 14 is a diagram showing a ninth embodiment of the present invention.

FIG. 15 is a diagram illustrating an example of a configuration of a conventional microstrip antenna.

FIG. 16 is a diagram illustrating an example of a portable wireless device on which a conventional microstrip antenna is mounted.

FIG. 17 is a diagram illustrating a state in which a portable wireless device on which a conventional microstrip antenna is mounted is used.

FIG. 18 is a diagram showing a relationship between the tilt angle of the microstrip antenna and the antenna effective gain.

[Explanation of symbols]

 1, 2, 7, 17, 19, 38 Dielectric plate 3 Antenna radiation element 4, 5, 12, 14, 16, 23 Strip line 6, 18 Ground conductor 8, 20 Metal conductor 9 Antenna plug 10 Through hole 15 Strip Line tip 21 Slot 22, 24 Cut 25 Parasitic element 26 Weight 27, 31, 32, 34 Rotating shaft 28, 30, 33, 35, 36 Rotating shaft support 29 Antenna cover 37 Holding member 45 Portable radio case Body 46 User's hand 47 Human head

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-145327 (JP, A) JP-A-4-122104 (JP, A) JP-A-2-226803 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01Q 13/08 H01Q 1/24

Claims (2)

(57) [Claims] 1. An antenna radiating element is attached to one surface,
A first dielectric plate in which a strip line is attached to the other surface and the strip line and the antenna radiating element are connected by a conductor; and a strip line is attached to one surface and ground to the other surface. A second dielectric plate on which a conductor is applied is disposed close to each other so that the surfaces of the respective dielectric plates having the strip line face each other, and the strip line on the first dielectric plate and the second dielectric plate are disposed. A microstrip antenna wherein a strip line on a body plate is electromagnetically coupled. 2. The first dielectric plate is configured to be rotatable while maintaining electromagnetic coupling between the strip line on the first dielectric plate and the strip line on the second dielectric plate. 2. The microstrip antenna according to claim 1, wherein the rotation center axis is deviated from the position of the center of gravity of the first dielectric plate.