JP3871930B2 - Radio wave lens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio wave lens for electronically controlling the traveling direction of a radio wave based on an externally input signal.
[0002]
[Prior art]
Conventionally, a radio wave lens 300 disclosed in Japanese Patent Publication No. 3-6683 and configured as shown in FIG. 3 is known. The radio wave lens 300 having the configuration shown in FIG. 3 uses liquid crystal as a medium used for changing the traveling direction of radio waves. Here, the radio wave lens 300 includes a plurality of phase shifters 310 as shown in FIG. In FIG. 3A, it is assumed that the radio wave is radiated from the horn antenna 400 toward the radio wave lens 300, and the electric field of the radiated radio wave is directed in the direction 20.
[0003]
FIG. 3B is a partially omitted view showing a configuration example of the phase shifter 310. The phase shifter 310 is constituted by four phase shift elements 320 as shown in FIG. 3B, and operates as a 4-bit phase shifter. It is assumed that the radio wave radiated from the horn antenna 400 propagates in the direction 10 shown in FIG. 3B, and the direction of the electric field at that time is in the direction 20 shown in FIG. As shown in FIG. 3B, the phase shift element 320 is a liquid crystal filled in a rectangular parallelepiped cell surrounded by two sets of dielectric thin plates 321, one set of conductive thin plates 322, the dielectric thin plates 321 and the electrode thin plates 322. 323 and a connection line 324.
[0004]
The orientation direction of each molecule constituting the liquid crystal 323 filled in the phase shifter 320 can be changed by the voltage applied to the conductor thin plate 322 via the connection line 324. Here, the change of the dielectric constant depending on the orientation direction of each molecule constituting the liquid crystal is known as anisotropy of the dielectric constant. Since liquid crystal has anisotropy in dielectric constant, the dielectric constant can be changed by controlling the orientation direction of the molecules, and the propagation speed of the radio wave passing through each phase shifter 320 can be changed. As a result, the operation as the radio wave lens 300 can be realized by adjusting the propagation velocity of the radio wave passing through each phase shift element 320 constituting the phase shifter 310 for each phase shift element 320.
[0005]
[Problems to be solved by the invention]
Here, since the liquid crystal used in the radio wave lens is a liquid, it is necessary to create a space for filling the liquid crystal with a ceramic plate or a metal plate. Conventionally, the liquid crystal cell is composed of a dielectric thin plate 321, a conductor thin plate 322, and a liquid crystal 323 as shown in FIG. In order to stably control the orientation of the liquid crystal 323, particularly in order to stably control the orientation of the liquid crystal 323 when no voltage is applied between the conductor thin plates 322, the thickness of the liquid crystal 323 is, for example, about 100 μm. The following must be thinned.
[0006]
On the other hand, the conductor thin plate 322 is required to have sufficient mechanical strength to maintain the shape of the liquid crystal cell in order to constitute the liquid crystal cell. For this reason, the thickness of the conductor thin plate 322 has to be about 100 μm or more, for example. Alternatively, it is conceivable to use a dielectric thin plate deposited with a conductive thin film instead of the conductive thin plate 322. Even in this case, the thickness of the dielectric thin plate must be, for example, about 50 μm or more.
[0007]
Due to the above restrictions, the ratio of the area of the liquid crystal part to the aperture area of the radio lens is reduced, the radio wave transmittance is remarkably reduced, and the rate of change of the dielectric constant of the radio lens is reduced. Problems such as narrowing of the range occurred.
Further, in order to secure a certain range of radio wave transmittance and radio wave traveling direction, it is required to make the liquid crystal 323 as thick as possible within a range of about 100 μm or less, for example. When the thickness of the liquid crystal 323 is increased in the conventional configuration, the response of the change in the alignment of the liquid crystal molecules to the change in the control voltage is delayed. As a result, there has been a problem that the response speed of radio wave beam control is reduced.
[0008]
The present invention has been made to solve such problems, and its purpose is to improve the transmittance of incident radio waves, expand the control range of the radio wave traveling direction, and improve the response speed of radio wave beam control. It is providing the radio wave lens which can do.
[0009]
[Means for Solving the Problems]
In view of the above points, the invention according to claim 1 is the first and second electrodes made of metal foil alternately arranged in parallel to the traveling direction of the radio wave, the first electrode, and the first electrode. A liquid crystal impregnated material sandwiched between two electrodes and impregnated with a predetermined liquid crystal in a predetermined material .
[0010]
With this configuration, in order to obtain the required range as the control range of the radio wave traveling direction, the size of the required radio wave lens can be made smaller than that of the conventional radio wave lens, so that the radio wave lens can be reduced in size and weight and easily formed. be able to.
In addition, if the radio lens of the present invention is considered as a part of the radio beam transmitter including the transmitter and the horn antenna, the radio lens has a higher transmittance than the conventional radio lens (the loss of the radio lens is reduced). Thus, the output power of the transmitter necessary for obtaining a desired transmission power can be reduced, and the entire apparatus can be reduced in size and weight.
[0011]
In addition, the invention according to claim 2 has a configuration according to claim 1, wherein the predetermined material includes paper, cloth, or fiber.
With this configuration, a radio wave lens can be configured using a normal material that can be easily impregnated with liquid crystal.
[0012]
According to a third aspect of the present invention, in the first aspect, the predetermined liquid crystal includes a nematic liquid crystal, a cholesteric liquid crystal, a smectic liquid crystal, or a liquid crystal obtained by mixing these liquid crystals.
With this configuration, since a liquid crystal having a strong dielectric anisotropy is used, a smaller radio wave lens can be realized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a radio wave lens according to a first embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a schematic configuration of a radio wave lens according to the first embodiment of the present invention. In FIG. 1A, the radio wave lens 100 includes a liquid crystal impregnated material 110, a first electrode 120, a second electrode 130, and a control power source 140.
[0014]
Each liquid crystal impregnated material 110 is obtained by impregnating a liquid crystal into a material that can be impregnated with paper, cloth, fiber, or other liquid crystal. Here, for example, a case where a thin plate having a thickness of about 200 μm is used will be described.
The first electrode 120 and the second electrode 130 are in the form of a film made of a conductive material, and may be, for example, a metal foil having a thickness of about 5 microns.
[0015]
Further, the liquid crystal impregnated material 110 is alternately stacked with the first and second electrodes 120 and 130 as shown in FIG. Here, as shown in FIG. 1A, the first electrode 120 and the second electrode 130 are further stacked alternately.
[0016]
Hereinafter, a portion sandwiched between the two closest second electrodes 130 illustrated in FIG. 1B is referred to as a liquid crystal cell layer. Here, the liquid crystal cell layer includes the two closest second electrodes 130. Therefore, the radio wave lens 100 can be considered structurally as a stack of liquid crystal cell layers. FIG. 1A shows the radio wave lens 100 when the number of stacks is n.
[0017]
Further, the first electrode 120 may have a structure in which strip-shaped electrodes are arranged in the horizontal direction, for example. Hereinafter, each of the strip-shaped electrodes is also referred to as a first electrode 120. In FIG. 1A, the number of strip-shaped electrodes arranged in the horizontal direction is m. Therefore, a total of n × m strip-shaped electrodes are arranged. In the following, as shown in FIG. 1B, the portion of the liquid crystal cell layer where one strip-shaped electrode is sandwiched between the second electrodes 130 is referred to as a liquid crystal cell. Here, the liquid crystal cell includes two second electrodes 130 sandwiching the liquid crystal impregnated material 110.
[0018]
Next, a control power supply 140 is connected between the first electrode 120 and the second electrode 130 of each liquid crystal cell. Here, the second electrode 130 has a predetermined reference potential such as ground, and the potential of the first electrode 120 is controlled by the control power supply 140.
[0019]
The operation of the liquid crystal cell will be described with reference to FIG. FIG. 2A shows the alignment direction of the liquid crystal when no voltage is applied between the first electrode 120 and the second electrode 130. Here, an example is shown in which the molecules 111 constituting the liquid crystal are arranged substantially parallel to the electrodes.
[0020]
Next, when a predetermined voltage is applied by the control power supply 140, the molecules 111 constituting the liquid crystal are substantially perpendicular to the first electrode 120 and the second electrode 130 as shown in FIG. It is comprised so that it may become. As described above, in the liquid crystal cell, when a predetermined voltage is applied between the first electrode 120 and the second electrode 130, the alignment direction of the liquid crystal molecules changes, and the dielectric constant of the liquid crystal impregnated material 110 changes. It has a configuration that can. The radio wave lens 100 can adjust the distribution of the dielectric constant in the radio wave lens 100 by adjusting the dielectric constant of each liquid crystal cell, and can control the direction of the radio wave beam.
[0021]
Here, an example of the ratio of the area of the liquid crystal layer portion in the radio wave lens opening area using the values of the thickness of the liquid crystal impregnated material 110 exemplified above and the thicknesses of the first electrode 120 and the second electrode 130 is shown. Calculate it. The calculated value is 97% (= 200 / (200 + 5)), and the amount of decrease in transmittance due to the metal foil can be reduced by several tens of percent compared to the radio wave lens of the prior art, and can be almost negligible. This is because, by using the liquid crystal impregnated material 110, the mechanical strength can be secured only by the liquid crystal impregnated material 110, so that the electrode can be thinned.
[0022]
In addition, since the change in the dielectric constant of the entire radio wave lens can be increased, the control range of the traveling direction of the radio wave beam can be expanded. In other words, the size of the radio wave lens necessary for obtaining a required beam control range can be reduced. At the same time, the response speed of the radio wave beam control can be increased.
[0023]
Here, the liquid crystal impregnated in the liquid crystal impregnation material 110 has anisotropy of dielectric constant with respect to a high frequency, and the dielectric constant in the major axis direction of the elongated liquid crystal molecules is higher than that in the minor axis direction. . Since the larger the anisotropy of the dielectric constant, the larger the phase shift can be controlled, the liquid crystal impregnated material 110 is impregnated with nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, or a mixed liquid crystal of these liquid crystals with a large dielectric anisotropy. It can be used as a liquid crystal.
[0024]
However, in order to obtain high speed, nematic liquid crystal having low viscosity and high elasticity is suitable. In particular, cyanobiphenyl, terphenyl, pyridine, pyrimidine, and tolan nematic liquid crystals having a large refractive index anisotropy are suitable. On the other hand, when using a smectic liquid crystal, a ferroelectric liquid crystal having spontaneous polarization and showing a high-speed response is useful. In addition, as a material for impregnating such liquid crystal, a material or a structure that has little loss in a high frequency region and can contain more liquid crystal is effective.
[0025]
As described above, the radio wave lens according to the first embodiment of the present invention has a radio wave lens size required to obtain a required range as a control range of the radio wave traveling direction as compared with a conventional radio wave lens. Since the size can be reduced, the radio wave lens can be reduced in size and weight and can be easily formed.
[0026]
In addition, if the radio lens of the present invention is considered as a part of the radio beam transmitter including the transmitter and the horn antenna, the radio lens has a higher transmittance than the conventional radio lens (the loss of the radio lens is reduced). Thus, the output power of the transmitter necessary for obtaining a desired transmission power can be reduced, and the entire apparatus can be reduced in size and weight.
Furthermore, since the response speed of the radio wave beam control becomes high, the application range can be expanded to an apparatus that requires high-speed beam control such as radar.
[0027]
【The invention's effect】
As described above, the present invention realizes a radio wave lens capable of improving the transmittance of incident radio waves, extending the control range of the radio wave traveling direction, and improving the response speed of radio wave beam control. Can do.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a radio wave lens according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining the operation of the radio wave lens according to the first embodiment of the invention.
FIG. 3 is a diagram showing a schematic configuration of a conventional radio wave lens.
[Explanation of symbols]
10 Radio wave traveling direction 20 Electric field direction 100 Radio wave lens 110 Liquid crystal impregnated material 111 Molecule 120 constituting liquid crystal First electrode 130 Second electrode 140 Control power supply 300 Conventional radio wave lens 310 Phase shifter 320 Phase shift element 321 Dielectric Body thin plate 322 Conductor thin plate 323 Liquid crystal 324 Connection line 400 Horn antenna

Claims (3)

It is sandwiched between first and second electrodes made of metal foil alternately arranged in parallel to the traveling direction of the radio wave, the first electrode and the second electrode, and a predetermined liquid crystal is used as a predetermined material. A radio wave lens comprising a liquid impregnated material impregnated .   The radio wave lens according to claim 1, wherein the predetermined material includes paper, cloth, or fiber.   2. The radio wave lens according to claim 1, wherein the predetermined liquid crystal includes nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, or liquid crystal obtained by mixing these liquid crystals.

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