JP4126002B2 - Directional variable antenna - Google Patents

Description

  The present invention relates to a variable directivity antenna particularly suitable as a transmission / reception antenna used in various information devices such as mobile phones and information terminals.

  In recent years, with the spread of products using wireless communication technology, great expectations are placed on research for expanding transmission capacity by multiplexing signals in multiple dimensions such as time and space, and polarization and code. In particular, with regard to multiplexing by space, it is considered to realize an adaptive array antenna including a circuit that employs a plurality of omnidirectional antennas and vector-synthesizes these signals. However, the adaptive array antenna has become a large practical bottleneck depending on the equipment used because the size and interval of a plurality of omnidirectional antennas are increased and the size thereof is increased. In particular, for use in mobile devices, it is required to reduce the size of the antenna as much as possible.

  On the other hand, a variable directivity antenna that can change the antenna directivity with respect to such an omnidirectional antenna is well known. The directivity variable antenna is a structure that changes the directivity by a pair of antennas and a feeding circuit, and can be downsized compared to the above-described adaptive array antenna. However, there are few studies and reports at present.

The following are examples of conventional directional variable antennas.
FIG. 5 is disclosed in Patent Document 1 below, and has a structure in which the antenna directivity is changed by the reflection element 2 circling around the radiating element 1 in a “mechanical” manner.
FIG. 6 is disclosed in Patent Document 2 below, in which a central driving element 4 and a parasitic element 5 are disposed on a circular ground conductor 3 so as to surround the central driving element 4 in a radial manner. The antenna directivity is switched to “electrical” by switching the impedance load 6 provided at the lower part of the parasitic element 5. The distance between the central driving element 4 and the parasitic element 5 is about λ / 4, and the entire antenna has a wavelength of 2λ or more.
Further, FIG. 7 is disclosed in the following Patent Document 3, which also has a circular grounding conductor 7, a feeding antenna element 8 on the grounding conductor 7, and a power-feeding variable surrounding it radially. A reactance element 9 is arranged. The distance d between the feeding antenna element and the parasitic variable reactance element has a value of about λ / 4, and the entire antenna has a wavelength of about λ.

  The directivity variable antennas shown as conventional examples in FIGS. 5, 6, and 7 mainly have a structure that changes the antenna directivity to “mechanical” or “electrical”. That is, a parasitic element is arranged around the radiator, which is the antenna body, and the directivity of the antenna is controlled using electromagnetic mutual coupling between the radiator and the parasitic element. Such a directivity control system performs directivity control by increasing the equivalent synthetic aperture of the antenna and increasing the gain, but considering the operating principle, the antenna size is relatively non-directional. It is difficult to reduce the size to the same size as the antenna. In particular, in the case of the conventional example shown in FIG. 5, since the space around which the reflecting element 2 circulates is provided, it is inevitable to increase the size of the entire momentum antenna. Further, as a general problem, when the wavelength used is as low as several GHz or less, the length of the wavelength becomes 10 cm or more, and a slight increase in size significantly hinders the convenience of the device. For these reasons, the variable directivity antenna could not be used for communication terminals.

JP-A-6-350334 Japanese Patent No. 3294155 JP 2001-24431 A

As a result of diligent research on the above problems, the present inventors applied an omnidirectional antenna that can be easily downsized as a basic structure, and thus achieved an omnidirectional antenna without increasing the equivalent synthetic aperture. We have developed a structure that can change the antenna directivity by making the electric field distribution nonuniform in the power supply. The reason behind this is as follows.
(1) Usually, a coaxial line is used as a transmission line for feeding power to the omnidirectional antenna, and the electric field distribution is uniform inside the coaxial line.
(2) Even when the electric field distribution of the coaxial line is changed by some technique, there is a characteristic that the electric field distribution immediately returns to uniform during propagation in the coaxial line.
(3) Therefore, if the electric field distribution in the coaxial line is intentionally changed immediately before feeding to the omnidirectional antenna, the antenna can be radiated before the electric field distribution returns uniformly. That is, the electric field distribution during power feeding can be made non-uniform.

  However, it should be noted about the above (1) to (3) that in order to change the electric field distribution of the coaxial line, a coaxial line having a certain size in dimension is required from the relationship with the operating wavelength. It is a point to do. This can be easily understood from the fact that a structure very small compared to the wavelength cannot be recognized as an electromagnetic wave. For example, in a coaxial circuit used for a general SMA connector or the like, it is possible to change the electric field distribution of the coaxial line with a frequency of about 8 GHz or more when the internal ground conductor has an inner diameter of about 4 mm. Therefore, as the inner diameter of the ground conductor is increased to 8 mm and 16 mm, the electric field distribution of the coaxial line can be changed to frequencies of about 4 GHz and 2 GHz, respectively.

  As described above, it is understood that if the inner diameter specification of the ground conductor incorporated in the coaxial line is increased, the electric field distribution is changed. However, there is a limit to increasing the coaxial line, and if possible, it depends on the general size specifications on the market. It is desirable to use a coaxial line connected to the feeding side. In order to satisfy such circumstances, the coaxial line connected to the feeding part of the antenna has a general size specification, and the diameter of the coaxial line is enlarged immediately before the feeding part, so that it can be coaxial even in the low frequency range. It becomes possible to change the electric field distribution of the line.

  The object of the present invention is to operate in a frequency band of several GHz, and have a directivity that can be obtained as large as an omnidirectional antenna and can be expected to be applied to a mobile communication terminal that requires a reduction in size. It is to provide a variable antenna.

  In order to achieve the above object, the directional variable antenna according to claim 1 of the present invention is a directional variable antenna that feeds power using a coaxial line, and includes an omnidirectional antenna unit and the antenna unit. Is connected to the coaxial line consisting of a signal line on the central axis and a cylindrical grounding conductor on the same axis, and is electrically connected to the enlarged diameter part. And electric field distribution varying means for changing the electric field distribution in a specific direction.

  According to the first aspect of the present invention, for example, a monopole antenna is used as a basic structure as an omnidirectional antenna portion, so that it is relatively the same size as this monopole antenna and has high sensitivity even in a frequency band of several GHz. A directional variable antenna can be realized. Directivity in a specific direction can be changed by changing the electric field distribution nonuniformly in the diameter-enlarged portion of the coaxial line connected immediately before feeding to such an omnidirectional antenna portion. In other words, by electrically changing the electric field distribution in the diameter-enlarged part of the coaxial line, a directional variable antenna that can switch the directivity at high speed with the same size as the omnidirectional antenna is realized. it can.

  The variable directivity antenna according to claim 2 is characterized in that slits or grooves are provided radially from the center of the conductor plate constituting the antenna portion.

  Depending on the shape of the omnidirectional antenna, the electric field distribution may be unevenly changed in the enlarged diameter part of the coaxial line connected immediately before the radiation from the radiating element (radiator). It can be considered that the electric field distribution returns to a uniform state. In order to avoid this, it is effective to provide slits or grooves radially from the center of the conductor plate of the antenna section. Providing slits or grooves in a radial manner has an effect of limiting the current path on the antenna surface that occurs when the electric field distribution tries to return uniformly to only the radiation direction from the center. As a result, it is possible to radiate electromagnetic waves radially while maintaining a non-uniform electric field distribution in the power feeding unit.

  The variable directivity antenna according to claim 3 is characterized in that the electric field distribution variable means includes a short-circuit means for short-circuiting a part between the signal line of the coaxial line and the ground conductor.

  As a technique for making the electric field distribution of the coaxial line non-uniform, it is necessary to electrically change the electric field distribution of the coaxial line from the outside of the antenna in order to switch the directivity of the antenna section at high speed. That is, the electric field distribution of the coaxial line can be changed by electrically short-circuiting only a part between the signal line and the ground conductor by the short-circuit means. In this case, it is necessary to sufficiently reduce the area of the portion to be short-circuited with respect to the area between the signal line of the coaxial line and the ground conductor. If the area of the short-circuited portion is not sufficiently small with respect to the area between the signal line of the coaxial line and the ground conductor, the reflection here becomes large and the radiation efficiency of the antenna itself is lowered. If the area of the portion to be short-circuited is reduced so that such reflection does not increase, the electric field distribution of the coaxial line can be changed at the time of short-circuit. Of course, since the short circuit can be electrically controlled, it is possible to easily change the directivity by switching the short circuit part at high speed, or to return to the non-directivity if all the short circuit parts are opened.

  The directivity variable antenna according to claim 4, wherein the short-circuit means has one end connected to the signal line and the other end connected to the cylinder inner peripheral surface of the ground conductor so as to be equiangular in all directions. It includes a plurality of short-circuit wires extending from.

  In the invention of claim 4, the electric field distribution of the coaxial line is electrically reduced by using, for example, a PIN diode or a MEMS switch as a switch for turning on / off the short-circuit line as a specific example of the short-circuit means. Can be changed.

  Further, in the variable directivity antenna according to claim 5, the electric field distribution varying means short-circuits a part of the floating conductor plate provided between the signal line of the coaxial line and the ground conductor with the ground conductor. It is characterized by having a short circuit line.

Even if a floating conductor plate is provided between the signal line of the coaxial line and the ground conductor, this alone does not disturb the electric field distribution of the coaxial line. However, the electric field distribution of the coaxial line is electrically reduced by short-circuiting a part of this floating conductor plate, preferably the tip part in the direction in which the signal of the coaxial line propagates, to the ground conductor using a PIN diode or a MEMS switch. Can be changed. And also in this case, the short circuit between the floating state and the ground conductor can be electrically controlled, so if the directivity is changed by switching the short-circuited part at high speed, or if all the short-circuited parts are opened, the omnidirectionality can be restored. Can also be easily done.
That is, it is possible to realize a variable directivity antenna having the same size as the omnidirectional antenna and capable of switching directivity at high speed.

  The variable directivity antenna according to claim 6 includes a plurality of floating conductor plates provided between the signal line of the coaxial line and the ground conductor, each having a length corresponding to the operating frequency. It is characterized by that.

  In the method of changing the electric field distribution of the coaxial line by short-circuiting a part of the floating conductor plate provided between the signal line of the coaxial line and the ground conductor with the ground conductor, a specific method depending on the size of the floating conductor plate is used. The effect can be obtained only at the frequency. Therefore, if floating conductors having different lengths are used, they have different operating frequencies. Therefore, if floating conductors having different lengths are controlled independently, directivity at a frequency corresponding to the length of each floating conductor can be independently controlled.

  The directivity variable antenna according to claim 7, wherein the electric field distribution varying means is interposed between and in contact with the signal line and the ground conductor in the diameter-enlarged portion of the coaxial line so that a part of the dielectric constant can be changed. It is characterized by including the dielectric material.

  According to the seventh aspect of the present invention, the electric field distribution of the coaxial line can be electrically changed by electrically changing only a part of the dielectric constant of the dielectric between the signal line of the coaxial line and the ground conductor. . In this case, it is possible to simply form a distribution using the refractive index difference, or to form an electric field distribution by changing the equivalent impedance in a periodic structure using the refractive index difference. Note that a liquid crystal material can be used as a specific example of the dielectric.

  The variable directivity antenna according to claim 8 is characterized in that a diameter-enlarged portion in the connection portion of the coaxial line is tapered so that an outer diameter gradually increases toward the antenna portion.

  In order to more effectively prevent reflection of electromagnetic waves in the enlarged diameter portion of the coaxial line, reflection can be minimized by making the enlarged diameter portion tapered.

  The directional variable antenna according to claim 9 is characterized in that the omnidirectional antenna section is a traveling wave antenna.

  The directivity control according to the present invention utilizes the electric field distribution modulation of the coaxial line, and therefore has a feature that there is not much control by frequency. In other words, as long as the omnidirectional antenna is widened, a wideband directional variable antenna can be realized. That is, by using a traveling wave antenna as the omnidirectional antenna, a broadband directional antenna having the same size as the omnidirectional antenna can be realized.

  The variable directivity antenna according to claim 10 is characterized in that the traveling wave antenna is a discone antenna.

  In a tenth aspect of the present invention, by adopting a discone antenna having the simplest structure as a specific example of a non-directional traveling wave antenna, a broadband directional antenna can be manufactured at low cost.

  In the directivity variable antenna according to claim 1 according to the present invention, for example, a monopole antenna having a basic structure as a non-directional antenna portion has a relatively same size as the monopole antenna. A highly directional variable antenna could be realized even in a frequency band of several GHz. That is, the directivity in a specific direction can be changed by changing the electric field distribution non-uniformly in the diameter-enlarged portion of the coaxial line connected immediately before feeding to the omnidirectional antenna part. By electrically changing the electric field distribution in the diameter-expanded portion, a directional variable antenna capable of switching the directivity at high speed with the same size as that of the omnidirectional antenna could be realized.

  3. The directional variable antenna according to claim 2, wherein a slit or a groove is provided radially in the conductor portion of the omnidirectional antenna portion, so that the electric field distribution is generated when the electric field distribution tries to return uniformly. The effect of limiting the current path on the surface to only the radiation direction from the center was obtained, and it became possible to radiate electromagnetic waves in a radial manner while maintaining a non-uniform electric field distribution in the power feeding part.

  According to the third aspect of the present invention, since the electric field distribution of the coaxial line can be electrically changed from the outside of the antenna, the directivity can be switched at high speed with the same size as the omnidirectional antenna. The directivity variable antenna could be achieved.

  According to the directional variable antenna according to claim 4, the means for changing the electric field distribution of the coaxial line is configured to short-circuit a part between the signal line of the coaxial line and the ground conductor. It was possible to realize a variable directivity antenna with the same size and capable of switching directivity at high speed.

  According to the variable directivity antenna according to claim 5, the means for changing the electric field distribution of the coaxial line short-circuits a part of the floating conductor plate provided between the signal line of the coaxial line and the ground conductor. By adopting the configuration, it was possible to realize a variable directivity antenna having the same size as the omnidirectional antenna and capable of switching directivity at high speed.

  According to the variable directivity antenna according to claim 6, a plurality of floating conductor plates are provided between the signal line of the coaxial line and the ground conductor, each having a length corresponding to the operating frequency, and different lengths. By controlling each floating conductor independently, it becomes possible to independently control the directivity at a frequency corresponding to the length of each floating conductor.

  According to the directional variable antenna according to claim 7, the electric field distribution of the coaxial line is electrically changed by electrically changing only a part of the dielectric constant of the dielectric between the signal line of the coaxial line and the ground conductor. I was able to change it. In this case, it is possible to form an electric field distribution by simply forming a distribution using a refractive index difference or by changing an equivalent impedance in a periodic structure using the refractive index difference. Note that a liquid crystal material can be used as a specific example of the dielectric.

  According to the directivity variable antenna of the eighth aspect, since the diameter-expanded portion of the coaxial line is tapered, it is possible to more effectively prevent electromagnetic waves from being reflected at the diameter-expanded portion of the coaxial line.

  According to the directional variable antenna of the ninth aspect, since the omnidirectional antenna is a traveling wave type antenna, it has the same size as the omnidirectional antenna, in other words, a wideband without increasing the size. The directivity variable antenna can be easily realized.

  According to the directional variable antenna according to claim 10, by using a discone antenna having the simplest structure as the non-directional traveling wave antenna, a wide-band directional antenna can be manufactured at low cost. I was able to.

Embodiments of a variable directivity antenna according to the present invention will be described below in detail with reference to the drawings.
[First Embodiment]
1 (a) and 1 (b) are a perspective view and a cross-sectional view showing a first embodiment of the present invention. In this case, a monopole antenna, which is a kind of omnidirectional antenna, is connected to the tip of the coaxial line 10 as the transmission line. The main body of the monopole antenna includes a disk-shaped ground plane 20 and a radiator (radiating element) 30 protruding from the center. In the ground plane 20, a metal film (or metal foil) 22 is coated or coated on the surface of a disk 21 made of a dielectric material. A through hole 23 is provided at the center of the ground plate 20, and the coaxial line 10 is connected to the back surface of the disk 21 through the connection fitting 13 in communication with the through hole 23. The coaxial line 10 is connected to the proximal end portion of the radiator 30 by a signal line 11 on the central axis. The coaxial line 10 has a cylindrical ground conductor 12 on the outer coaxial side of the signal line 11, and this end is connected to the metal film 22 on the surface of the ground plane 20.

  1B, the portion where the ground conductor 12 is fitted and connected to the through hole 23 of the ground plane 20 is a tapered enlarged portion 12b having a cylindrical inner diameter D. The step is formed to be slightly larger than the cylinder inner diameter d of the main portion 12a. Further, in the tapered enlarged portion 12b of the ground conductor 12, as a short-circuit means that is a specific example of the electric field distribution varying means referred to in the present invention, the four short-circuit lines 40, 41, 42, and 43 have a phase difference of 90 °. Thus, in radial directions in four directions, each end is connected to the signal line 11 and the other end is connected to the inner circumferential surface of the ground conductor 12. Further, switches 50, 51, 52, and 53 are connected to the base ends of the respective short-circuit lines 40, 41, 42, and 43, respectively.

  As the switches 50, 51, 52, and 53, for example, PIN diodes can be used, and an electrical on / off operation can be controlled by a control electrode (not shown) arranged outside the antenna. In this case, for example, if all the four switches 50, 51, 52, 53 are turned off, the electric field distribution in the coaxial line 10 can be prevented from being disturbed, and the radiation pattern as an antenna can be made "omnidirectional". Can be maintained. On the other hand, when any one of the four switches is turned “ON”, the electric field distribution of the coaxial line 10 is disturbed, and the radiation pattern as the antenna can have “directivity”. Further, the directivity of the antenna can be switched and changed by controlling switching of the “ON” states of the four switches 50, 51, 52, and 53 regularly or irregularly.

  Therefore, the variable directivity antenna according to the first embodiment operates as follows. When all the switches 50, 51, 52, 53 in the four directions are turned off, the electric field distribution of the coaxial line 10 is not disturbed, and the radiation pattern of the antenna remains omnidirectional. On the other hand, when only one of the four-way switches 50, 51, 52, 53 is turned on, the electric field in the coaxial line 10 is disturbed, and the radiation pattern of the antenna has directivity. In addition, the directivity of the antenna can be switched by switching an on-state switch. As is clear from this, the antenna directivity can be switched with the same size as that of a normal omnidirectional antenna, that is, without increasing the size.

[Second Embodiment]
2A and 2B are an overall perspective view and a cross-sectional view showing a second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same or common member in the material of each member shown in 1st Embodiment of FIG. 1 (a), (b), a shape, and a function. In this case as well, a monopole antenna, which is an omnidirectional antenna, has a basic structure, and slits 24 extend radially from the through hole 23 in the ground plane 20. The ground plane 20 is electrically divided into a plurality of regions by the plurality of slits 24.

  Further, in the second embodiment, as shown in FIG. 2 (b), in the taper enlarged portion 12b of the ground conductor 12 in the coaxial line 10, other short-circuit means of the electric field distribution varying means referred to in the present invention. As shown, four metal pieces 60, 61, 62, and 63 are provided. These four metal pieces are in a floating state with a phase difference of 90 ° in a radial manner in four directions and in a direction that hangs down in the vertical direction in the figure in a direction parallel to the signal line 11 and the ground conductor 12. That is, a part of each metal piece 60, 61, 62, 63 is electrically connected to the cylinder inner peripheral surface of the taper enlarged portion 12b of the ground conductor 12 via the switches 70, 71, 72, 73, respectively. .

  As the switches 70, 71, 72, 73, for example, MEMS switches are used, and an electrical on / off state can be controlled by a control electrode (not shown) arranged outside the antenna.

  Therefore, the variable directivity antenna according to the second embodiment operates as follows. Also in this case, as in the first embodiment, for example, if all of the four switches 70, 71, 72, 73 are turned off, the electric field distribution in the coaxial line 10 can be prevented from being disturbed. The radiation pattern can be kept “omnidirectional”. On the other hand, when any one of the four switches is turned “ON”, the electric field distribution of the coaxial line 10 is disturbed, and the radiation pattern as the antenna can have “directivity”. In addition, the directivity of the antenna can be switched and changed by controlling switching of the “ON” states of the four switches 70, 71, 72, and 73 regularly or irregularly. In addition, the radial slits 24 provided in the ground plane 20 make it easy to maintain non-uniformity of the radiation electric field distribution.

[Third Embodiment]
FIGS. 3A and 3B are an overall perspective view and a sectional view showing a third embodiment of the present invention. The materials, shapes and functions of the respective members shown in the first embodiment of FIGS. 1A and 1B and the second embodiment of FIGS. 2A and 2B are the same. Or the same code | symbol is attached | subjected to the common member. In this case, a discone antenna comprising an upper conical electrode 80 and a ground plane 20 is shown as an omnidirectional antenna portion. Further, the base plate 20 and the conical electrode 80 are respectively provided with slits 24 and 81 in a radial manner.

  As is apparent from FIG. 3B, at the connection portion between the coaxial line 10 and the discone antenna, the tube of the tapered enlarged portion 12b of the ground conductor 12 is provided in parallel with the signal line 11 and the ground conductor 12 of the coaxial line 10. The first metal pieces 90, 91, 92, 93 partially connected to the inner peripheral surface and the second metal pieces 110, 111, 112, 113 are provided in a state of floating between the signal lines 11. In this case, a gap between the signal line 11 and the ground conductor 12 is filled with a dielectric 15 having a dielectric constant of 2.3, and the first and second metal pieces are buried in the dielectric 15. The upper and lower stages are connected at equal angular positions in all directions with a phase difference of 90 °. These first and second metal pieces are connected by first switches 100, 101, 102, 103 and second switches 120, 121, 122, 123, respectively. In the illustrated example, the length dimension of each of the first metal pieces 90, 91, 92, 93 is 0.8 mm, and the length dimension of each of the second metal pieces 110, 111, 112, 113 is 1.2 mm. The electric field distribution can be changed at each frequency of 25 GHz for the first metal piece and 19 GHz for the second metal piece. PIN diode switches are used as the first and second switches, and the on / off state can be electrically controlled from outside the antenna using a control electrode (not shown here).

  Therefore, the variable directivity antenna according to the second embodiment operates as follows. When all the first and second switches are turned off, the electric field distribution of the coaxial line 10 is not disturbed, and the radiation pattern of the antenna remains omnidirectional. When only one stage of the first switches 100, 101, 102, 103 is turned on, the electric field in the coaxial line is disturbed in the 25 GHz signal, and the radiation pattern of 25 GHz has directivity. On the other hand, when only the second switch 120, 121, 122, 123 at the second stage is turned on, the electric field in the coaxial line is disturbed in the 19 GHz signal, and the radiation pattern of 19 GHz has directivity. . By switching the direction of the switch to be turned on, the directivity of the antenna can be switched, and each frequency can be controlled independently. Further, the slits 24 and 81 of the base plate 20 and the upper conical electrode 80 facilitate radiation while maintaining the nonuniformity of the radiation field distribution. As is clear from the present embodiment, the directivity can be switched independently at a plurality of frequencies with a size relatively equal to that of a normal omnidirectional antenna.

[Fourth Embodiment]
FIGS. 4A and 4B are an overall perspective view and a sectional view showing a fourth embodiment of the present invention. In this case, a biconical antenna including a conical upper electrode 140 and a lower electrode 130 is employed as the omnidirectional antenna portion. In the present embodiment, a cylindrical control electrode 16 is coaxially connected to the upper end of the tapered enlarged diameter portion 12 b provided on the ground conductor 12 of the coaxial line 10, and between the control electrode 16 and the signal line 11. In addition, a liquid crystal member 150 (not shown is an electrode for taking out the antenna outside) is filled as a dielectric.

  Therefore, the operation of the fourth embodiment can change the dielectric constant of the liquid crystal member 150 in an arbitrary portion under the control of the control electrode 16. Unless the dielectric constant of the liquid crystal member 150 is changed, the electric field distribution of the coaxial line 10 is not disturbed, and the radiation pattern of the antenna remains omnidirectional. On the other hand, when only a part of the dielectric constant of the liquid crystal member 150 is changed, the electric field in the coaxial line 10 is disturbed, and the radiation pattern of the antenna has directivity. In addition, the directivity of the antenna can be switched by switching the place where the dielectric constant of the liquid crystal member 150 is changed. Further, the slits 141 and 131 of the upper electrode 140 and the lower electrode 130 make it easy to radiate while maintaining the nonuniformity of the radiation electric field distribution. As is clear from the present embodiment, the directivity can be switched with a size relatively equal to that of a normal omnidirectional antenna.

  Although the first to fourth embodiments have been described above, the present invention is not limited to the requirements shown here, such as the shape of each member and the combination with other elements. These points can be changed within a range that does not impair the gist of the present invention, and can be appropriately determined according to the application form.

It is the whole perspective view and sectional view showing a 1st embodiment of a directivity variable antenna concerning the present invention. It is the whole perspective view and sectional drawing which show 2nd Embodiment of the directivity variable antenna concerning this invention. It is the whole perspective view and sectional drawing which show 3rd Embodiment of the directivity variable antenna concerning this invention. It is the whole perspective view and sectional drawing which show 4th Embodiment of the directivity variable antenna concerning this invention. It is a perspective view which shows the directional antenna of a prior art example. It is a perspective view which shows the directional antenna of another prior art example. It is a perspective view which shows the directional antenna of another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Coaxial line 11 Signal line 12 Cylindrical grounding conductor 12b Taper enlarged diameter part 13 Connection metal fitting 15 Dielectric 16 Control electrode 20 Ground plane 24 Slit 30 Radiator 40-43 Short-circuit line (short-circuit means)
50-53 Switch 60-63 Floating metal piece (short circuit means)
70 to 73 switch 80 conical electrode 100 to 103 first metal piece 110 to 113 second metal piece 130 lower electrode 140 upper electrode 150 liquid crystal member (dielectric)

Claims (10)

A directional variable antenna that feeds power using a coaxial line,
An omnidirectional antenna,
The connection part with the antenna part is an enlarged diameter part formed by expanding the diameter, and a coaxial line composed of a signal line on the central axis and a cylindrical ground conductor on the coaxial axis,
A variable directivity antenna, comprising: an electric field distribution variable means electrically connected to the diameter-expanded portion to change the electric field distribution in a specific direction.   2. The variable directivity antenna according to claim 1, wherein slits or grooves are provided radially from the center of the conductor plate constituting the antenna unit.   The variable directivity antenna according to claim 1 or 2, wherein the electric field distribution varying means includes short-circuit means for short-circuiting a part between the signal line and the ground conductor of the coaxial line.   The short-circuit means includes a plurality of short-circuit wires that have one end connected to the signal line of the coaxial line and the other end connected to the cylinder inner peripheral surface of the ground conductor and extending from equilateral positions in all directions. The directional variable antenna according to claim 3.   The electric field distribution varying means has a short-circuit line for short-circuiting a part of a floating conductor plate provided between the signal line of the coaxial line and the ground conductor to the ground conductor. Item 4. The variable directivity antenna according to any one of items 1 to 3.   6. The directivity variable according to claim 5, wherein a plurality of floating conductor plates are provided between the signal line of the coaxial line and the ground conductor, each having a length corresponding to an operating frequency. antenna.   The electric field distribution varying means includes a dielectric that is interposed between and in contact with the signal line and the ground conductor in the diameter-enlarged portion of the coaxial line so that a part of the dielectric constant can be changed. The directivity variable antenna according to any one of claims 1 to 3.   8. The directivity according to claim 1, wherein an enlarged diameter portion of the coaxial line connecting portion is tapered so that an outer diameter gradually increases toward the antenna portion. 9. Variable antenna.   9. The variable directivity antenna according to claim 1, wherein the omnidirectional antenna unit is a traveling wave antenna. The variable directivity antenna according to claim 9, wherein the traveling wave antenna is a discone antenna.

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