JP2009278501A - Housing for antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a housing 20 for antenna which is a radome covering an antenna radiation element 12, and is improved in sensitivity in a low elevation angle direction. <P>SOLUTION: In the housing 20 for antenna covering the antenna radiation element 12 from zenith side to low elevation angle side, the inner peripheral surface 20a of the housing 20 and the outer peripheral surface 20b of the housing 20 are configured such that an angle (θ1) becomes smaller than an angle (θ2) (θ1<θ2). The angle (θ1) is formed between a lower portion than an incident position A of a tangent on a longitudinal cross section including the zenith direction of the inner peripheral surface 20a and a direction in which a radio wave is incident. At the incident position A, a radio wave radiated from the antenna radiation element 12 is incident into a dielectric member constituting the antenna element 20 in at least a low elevation angle side portion. The angle (θ2) is formed between a lower portion than a radiation position B of a tangent on a longitudinal cross section including the zenith direction of the outer peripheral surface 20b and a direction in which a radio wave is incident into the dielectric member. At the radiation position B, the radio wave incident into the dielectric member is radiated from the dielectric member to the outside of the housing 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antenna casing in which antenna sensitivity in a low elevation angle direction is improved by an antenna casing covering a planar antenna radiating element such as a GPS antenna or a mobile communication antenna.

As a planar antenna radiating element such as a GPS antenna or a mobile communication antenna, a microstrip antenna having a discharge electrode on a dielectric substrate is widely used. In this antenna radiating element, the sensitivity in the zenith direction is excellent, but the sensitivity in the low elevation angle direction is lower than that in the zenith direction. Therefore, Japanese Patent Laid-Open No. 05-199032 proposes a technique for improving the sensitivity in the low elevation angle direction. In this technique, a dielectric having a triangular cross section is disposed around an outer peripheral end of a microstrip antenna. This section is a prism effect of a dielectric having a triangular shape, and the antenna sensitivity in the low elevation angle direction is improved by refracting radio waves in the low elevation angle direction.
Japanese Patent Laid-Open No. 05-199032

  By the way, in order to mechanically protect a planar antenna radiating element such as a GPS antenna or a mobile communication antenna, a radome that covers from the zenith direction to a low elevation angle direction is generally provided. Is done. In the conventional redome, as shown in FIGS. 8 and 9, the cross section of the antenna casing 10 as the radome has a constant thickness and is formed of ABS resin, ASA resin, or the like, and has mechanical strength. The dielectric material (εγ = 2 to 3) having a small relative dielectric constant is used so that the antenna characteristics of the antenna radiating element 12 are not affected as much as possible. FIG. 8 is an external perspective view of a conventional antenna casing, and FIG. 9 is an AA longitudinal sectional view of the antenna radiating element covered with the conventional antenna casing of FIG.

  The technique proposed in the above-mentioned Japanese Patent Application Laid-Open No. 05-199032 is excellent in that it can transmit and receive radio waves in the low elevation angle direction with high sensitivity. However, since a dielectric having a triangular cross section is arranged around the outer peripheral edge of the microstrip antenna, the sensitivity between the elevation angle affected by this dielectric and the elevation angle not affected at all is improved. There can be a big difference. In addition, a radome for protecting the microstrip antenna is required separately. Therefore, the inventors considered not only using the antenna housing as a radome as a member for protecting the antenna radiating element but also improving the antenna characteristics of the antenna radiating element.

  The present invention has been invented under the circumstances as described above, and it is an object of the present invention to provide an antenna casing in which the sensitivity in the low elevation angle direction is improved by the antenna casing as a radome covering the antenna radiating element. And

  In order to achieve such an object, an antenna casing of the present invention is an antenna casing that covers an antenna radiating element from a zenith side to a low elevation angle side, and at least a portion on the low elevation angle side of the antenna casing. Then, a tangent line on a longitudinal section including the zenith direction of the inner peripheral surface of the antenna casing at an incident position where the radio wave radiated from the antenna radiating element enters the dielectric member constituting the antenna casing. The angle (θ1) between the portion below the incident position and the direction in which the radio wave is incident is such that the radio wave incident on the dielectric member is radiated from the dielectric member to the outside of the antenna housing. More than the angle (θ2) between the portion below the radiation position of the tangent on the longitudinal section including the zenith direction of the outer peripheral surface of the antenna housing at the position and the direction in which the radio wave enters the dielectric member, small( The inner peripheral surface and the outer peripheral surface of the antenna housing are configured to satisfy θ1 <θ2).

  The dielectric member of the antenna casing may be configured to be thicker at the lower elevation side where the operation is required as an antenna and at the lower elevation side.

  Further, the outer periphery at a radiation position where the radio wave is radiated outward from the dielectric member due to an inclination of the inner peripheral surface at an incident position where the radio wave radiated from the antenna radiation element enters the dielectric member. You may comprise the said internal peripheral surface and the said outer peripheral surface of the said housing | casing for antennas so that the inclination of a surface may become closer to a horizontal direction.

  Furthermore, both the inner peripheral surface and the outer peripheral surface of the antenna housing may be formed of a spherical surface or an elliptical spherical surface.

  Further, the dielectric member constituting the antenna housing may be made of a material having a relative dielectric constant of 10 or more and a dielectric loss tangent of 0.001 or less.

  4. The antenna housing according to claim 1, wherein the antenna housing at an incident position incident on a dielectric member constituting the antenna housing is at least a portion on the low elevation angle side of the antenna housing. The angle (θ1) between the inner peripheral surface of the light source and the direction in which the radio wave is incident is the angle (θ2) between the outer peripheral surface at the radiation position radiated outward from the dielectric member and the direction in which the radio wave enters the dielectric member Therefore, the inner peripheral surface and the outer peripheral surface are radiated at a lower elevation angle than the same angle with respect to the direction in which the radio wave enters. Accordingly, the sensitivity in the low elevation angle direction is improved. Moreover, since the sensitivity in the low elevation angle direction is improved by using the antenna casing as a radome that covers the antenna radiating element, the number of parts is the same as the conventional one.

  In the antenna housing according to claim 4, since the inner peripheral surface and the outer peripheral surface are spherical surfaces or elliptical spherical surfaces, the cross-sectional shape of the antenna housing is continuous from the zenith direction to the low elevation angle direction. It does not cause an elevation angle such that the sensitivity of the antenna characteristics changes suddenly due to the antenna housing.

  Further, in the antenna housing according to claim 5, since the relative permittivity of the dielectric member constituting the antenna housing is large, the radio wave when entering or radiating from the inside of the dielectric member. The angle at which the light is refracted is large, and radio waves can be emitted in the direction of lower elevation. In addition, according to experiments, the sensitivity in the zenith direction has also been improved, and it is considered that the antenna casing also acts as an antenna radiating element, and the sensitivity has been improved by the extent to which the radiation area has increased. Further, by using a material having a small dielectric loss tangent, the loss due to the antenna housing can be made as small as possible.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an external perspective view of a first embodiment of an antenna housing of the present invention. FIG. 2 is a BB longitudinal sectional view of FIG. 1 in a state where the antenna radiating element is covered with the antenna casing of FIG. FIG. 3 is a diagram for explaining that the sensitivity in the low elevation angle direction is improved by the structure of the antenna housing of FIG. 1.

  1 to 3, the antenna housing 20 according to the first embodiment of the present invention has a planar shape such that a circular bowl is turned down, and the inner peripheral surface 20a and the outer peripheral surface 20b are both spherical or elliptical. It is formed in a spherical shape, and has a shape in which the curvature of the outer peripheral surface 20b is larger than the curvature of the inner peripheral surface 20a. As an example, it is made of a dielectric member such as PPS resin having a large relative dielectric constant (εγ = 10 or more) and a small dielectric loss tangent (0.001 or less). Further, a flat type antenna radiating element 12 is disposed therein, and the antenna radiating element 12 is covered from the zenith side to the low elevation angle side by the antenna casing 20. In addition, at least at the portion of the antenna housing 20 on the low elevation angle side, the radio wave radiated from the antenna radiating element 12 is incident on the dielectric member constituting the antenna housing 20 at the incident position A of the antenna housing. The angle between the incident position A of the tangent on the longitudinal section including the zenith direction of the inner peripheral surface 20a and the direction in which the radio wave enters is θ1, and the radio wave incident in the dielectric member is transmitted from the dielectric member to the antenna housing. The direction below the tangential radiation position B on the longitudinal section including the zenith direction of the outer peripheral surface 20b of the antenna housing 20 at the radiation position B radiated to the outside of the body 20 and the direction in which the radio wave enters the dielectric member The inner circumferential surface 20a and the outer circumferential surface 20b of the antenna housing 20 are configured such that the angle θ1 is smaller than the angle θ2 (θ1 <θ2). Such a structure is also configured such that the dielectric member of the antenna casing 20 is thicker toward the lower side where the lower elevation angle is required at the portion on the lower elevation side where operation as an antenna is required. In addition, radiation is radiated outward from the dielectric member due to the inclination of the inner peripheral surface 20a at the incident position A where the radio wave radiated from the antenna radiating element 12 is incident on the dielectric member of the antenna housing 20. The inner peripheral surface 20a and the outer peripheral surface 20b of the antenna housing 20 are configured so that the inclination of the outer peripheral surface 20b at the position B is closer to the horizontal direction.

  In the antenna casing 20 of the first embodiment having such a configuration, the radiation direction of the radio wave radiated outward from the radiation position B of the outer peripheral surface 20b is incident on the incident position A of the inner peripheral surface 20a. The elevation angle direction is lower than the radio wave incident direction. Therefore, the antenna casing 20 can improve the sensitivity of the antenna on the low elevation side. This is because the inside and outside of the antenna housing 20 are air having a relative dielectric constant of 1, and the dielectric member of the antenna housing 20 has a relative dielectric constant much larger than that of air. When incident and radiated on the dielectric member, the direction of the radio wave is refracted according to Snell's law, and the angle (θ1) between the inner peripheral surface 20a at the incident position A and the direction in which the radio wave is incident is given by By making the angle (θ2) smaller than the angle (θ2) between the outer peripheral surface 20b at B and the direction in which the radio wave enters the dielectric member (θ1 <θ2), the radiation position is greater than the incident direction of the radio wave incident on the incident position A The radiation direction of the radio wave radiated from B is a low elevation angle direction.

  Here, it will be briefly described that the radiation direction of the radio wave radiated from the radiation position B is lower than the incident direction of the radio wave incident on the incident position A. First, in FIG. 3, the angle of the incident direction A perpendicular to the tangent to the inner peripheral surface 20a and the incident direction of the radio wave is α1, and the angle of the incident and bent direction in the dielectric member is γ1, The angle between the perpendicular line to the tangent to the outer peripheral surface 20b at the position B and the incident direction of the radio wave is α2, and the angle in the direction of being radiated and bent from the dielectric member is γ2. Further, an angle of a difference in inclination between the inner peripheral surface 20a and the outer peripheral surface 20b is β. This angle β is also an angle formed by vertical lines with respect to the tangent lines of the inner peripheral surface 20a and the outer peripheral surface 20b. Furthermore, an angle formed by the radiation direction of the radio wave radiated from the radiation position B with respect to a line parallel to the perpendicular line to the tangent line of the inner peripheral surface 20a is denoted by γ2 '. Then, θ1 = α1 + 90 ° and θ2 = θ1 + β. And according to Snell's law, γ1 / α1 = α2 / γ2. Furthermore, α2 = γ1 + β. And γ2 ′ = γ2−β. From these equations, γ2 ′ = α1 + β · α1 / γ1-β. Since α1> γ1, γ2 ′> α1 is established, and the radiation direction of the radio wave emitted from the radiation position B is lower than the incident direction of the radio wave incident on the incident position A.

  The inventors of the present invention compared the antenna characteristics of the antenna casing 20 of the first embodiment of the present invention and the conventional antenna casing 10 by experiment. First, the antenna casings 10 and 20 were measured with the same dielectric member having a relative dielectric constant of 3. In the antenna housing 20 of the present invention, the planar dimension is a circle having a diameter of 46 mm and a height of 12 mm, and the conventional antenna housing 10 has the shape shown in FIGS. The plane dimensions are 35.5 × 30.4 mm and the height is 11.5 mm. The measurement result was that the antenna casing 20 of the present invention was 0.6 dBic in the zenith direction and −4.2 dBic in the low elevation angle direction of +10 degrees, whereas the conventional antenna casing 10 was in the zenith direction. It was -5.6 dBic in the low elevation direction of +10 degrees at 0.6 dBic. Therefore, the sensitivity is improved in the low elevation angle direction. Furthermore, the antenna casing 20 of the present invention was measured with a dielectric member having a relative dielectric constant of 20. Then, in the antenna casing 20 of the present invention having a relative dielectric constant of 20, it is 1.1 dBic in the zenith direction and −3.8 dBic in the low elevation angle direction of +10 degrees, and is changed to a dielectric member having a large relative dielectric constant. Overall, the sensitivity was improved in all elevation directions. It is considered that this is because the antenna casing 20 also acts as an antenna radiating element, and the sensitivity is improved by the extent that the radiation area is expanded. In addition, the loss by the antenna housing 20 is made as small as possible by using a material having a high relative dielectric constant and a dielectric loss tangent as small as 0.001 or less. Further, the inventors configured the antenna casing 20 of the first embodiment of the present invention with dielectric members having relative dielectric constants of 3, 5, 10, 20, 25, and 30, respectively, and changed the antenna characteristics. Measured. Then, respective sensitivities of -2.3 dBic, -2.1 dBic, -1.8 dBic, -1.5 dBic, -1.5 dBic, and -1.3 dBic were obtained in the low elevation direction of +10 degrees. From these measurement results, it was found that when a dielectric member having a relative dielectric constant of 10 or more was used, the sensitivity was further improved.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a vertical cross-sectional view of the antenna radiating element covered by the antenna casing of the second embodiment. FIG. 5 is a diagram for explaining that the sensitivity in the low elevation angle direction is improved by the structure of the antenna housing of FIG. 4. 4 and 5, the same or equivalent members as those in FIGS. 1 to 3 are denoted by the same reference numerals, and redundant description is omitted.

  4 and 5, the antenna housing 30 according to the second embodiment of the present invention is substantially the same in appearance as the conventional one shown in FIG. 8 and has a substantially trapezoidal cross section. The lower elevation side where the operation is required is configured such that the lower side of the lower elevation angle is thicker, and the radio wave radiated from the antenna radiating element 12 is within the dielectric member of the antenna housing 30. The antenna housing so that the inclination of the outer peripheral surface 30b at the radiation position B where the radio wave is radiated outward from the dielectric member is closer to the horizontal direction than the inclination of the inner peripheral surface 30a at the incident position A incident on the antenna 30 inner peripheral surfaces 30a and outer peripheral surfaces 30b are formed. In addition, a planar type antenna radiating element 12 is disposed therein, and the antenna radiating element 12 is covered from the zenith side to the low elevation angle side by the antenna housing 30. Accordingly, the tangent line on the longitudinal section including the zenith direction of the inner peripheral surface 30a of the antenna casing at the incident position A where the radio wave radiated from the antenna radiating element 12 enters the dielectric member constituting the antenna casing 30. An angle at a radiation position B at which a radio wave incident on the dielectric member is radiated from the dielectric member to the outside of the antenna housing 30 is defined as θ1. If the angle between the radiant position B of the tangent on the longitudinal section including the zenith direction of the outer peripheral surface 30b of the housing 30 and the direction in which the radio wave enters the dielectric member is θ2, the angle θ1 is greater than the angle θ2. The inner peripheral surface 30a and the outer peripheral surface 30b of the antenna housing 30 are configured so as to be smaller (θ1 <θ2).

  Even in the antenna casing 30 of the second embodiment having such a configuration, the radiation direction of the radio wave radiated outward from the radiation position B of the outer peripheral surface 30b is the inner peripheral surface, as in the first embodiment. The elevation angle direction is lower than the incident direction of the radio wave incident on the incident position A of 30a, and the antenna casing 30 improves the sensitivity of the antenna on the low elevation angle side.

  In addition, even in the low elevation angle portion, in the low elevation angle portion where the operation as an antenna is not required, as shown in FIG. 6, the outer edge portion 40c of the outer peripheral surface 40b of the antenna housing 40 is cut in the vertical direction. It may be. FIG. 6 is a longitudinal sectional view of the antenna radiating element 12 covered with the antenna casing 40 of the third embodiment. Of course, the inclination of the inner peripheral surface 40a and the outer peripheral surface 40b of the antenna housing 40 is set in the same manner as in the first and second embodiments in the portion on the low elevation side where operation as an antenna is required. It is.

  Further, even in the low elevation angle portion, in the low elevation angle portion where the operation as an antenna is not required, as shown in FIG. 7, the outer edge portion 50c of the outer peripheral surface 50b of the antenna housing 50 bites the lower side inward. It may be cut by an inclined surface. FIG. 7 is a longitudinal sectional view of the antenna radiating element 12 covered with the antenna casing 50 of the fourth embodiment. Of course, the inclination of the inner peripheral surface 50a and the outer peripheral surface 50b of the antenna housing 50 is set in the same manner as in the first and second embodiments in the portion on the low elevation side where operation as an antenna is required. It is.

It is an external appearance perspective view of 1st Example of the housing | casing for antennas of this invention. FIG. 3 is a vertical cross-sectional view taken along the line BB in FIG. 1 in a state where the antenna radiating element is covered with the antenna casing in FIG. It is a figure for demonstrating that the sensitivity of a low elevation angle direction improves with the structure of the housing | casing for antennas of FIG. It is a longitudinal cross-sectional view of a state in which the antenna radiating element is covered with the antenna casing of the second embodiment. FIG. 5 is a diagram for explaining that the sensitivity in the low elevation angle direction is improved by the structure of the antenna casing of FIG. 4. It is a longitudinal cross-sectional view of the state which covered the antenna radiation | emission element with the antenna housing | casing of 3rd Example. It is a longitudinal cross-sectional view of the state which covered the antenna radiation | emission element with the antenna housing | casing of 4th Example. It is an external appearance perspective view of the conventional antenna housing | casing. It is an AA longitudinal cross-sectional view of the state which covered the antenna radiation | emission element with the conventional antenna housing | casing of FIG.

Explanation of symbols

10, 20, 30, 40, 50 Antenna housing 12 Antenna radiating element 20a, 30a, 40a, 50a Inner peripheral surface 20b, 30b, 40b, 50b Outer peripheral surface θ1 The tangent to the inner peripheral surface at incident position A and radio waves Angle with the incident direction θ2 Angle between the tangent of the outer peripheral surface at the radiation position B and the direction in which the radio wave enters the dielectric member

Claims (5)

An antenna casing that covers an antenna radiating element from a zenith side to a low elevation angle side, and radio waves radiated from the antenna radiating element at least in a portion on the low elevation angle side of the antenna casing. The angle between the lower part of the tangent on the longitudinal section including the zenith direction of the inner peripheral surface of the antenna housing at the incident position where the incident light enters the dielectric member and the direction in which the radio wave is incident ( θ1) is a longitudinal section including the zenith direction of the outer peripheral surface of the antenna casing at a radiation position where the radio wave incident on the dielectric member is radiated from the dielectric member to the outside of the antenna casing. The inside of the antenna casing is smaller than an angle (θ2) between a portion of the tangential line on the surface below the radiation position and a direction in which the radio wave is incident on the dielectric member (θ1 <θ2). With the circumference Antenna housing, characterized in that to constitute a Kigaishu surface. 2. The antenna housing according to claim 1, wherein the dielectric member of the antenna housing is thicker toward the lower side at a lower elevation angle at a portion on the lower elevation angle side that is required to operate as an antenna. An antenna housing characterized by comprising. The antenna casing according to claim 1, wherein the radio wave is outward from the dielectric member due to an inclination of the inner peripheral surface at an incident position where the radio wave radiated from the antenna radiating element enters the dielectric member. The antenna casing is characterized in that the inner peripheral surface and the outer peripheral surface of the antenna casing are configured such that the inclination of the outer peripheral surface at a radiation position radiated to the antenna is closer to the horizontal direction. 2. The antenna casing according to claim 1, wherein the inner peripheral surface and the outer peripheral surface of the antenna casing are both spherical or elliptical spherical surfaces. 5. The antenna casing according to claim 1, wherein the dielectric member constituting the antenna casing is made of a material having a relative dielectric constant of 10 or more and a dielectric loss tangent of 0.001 or less. An antenna housing characterized by the following.