Patent Grant
8896492
The present application is based on and claims priority to Japanese Patent Applications No. 2009-265491 filed on Nov. 20, 2009, and No. 2010-214051 filed on Sep. 24, 2010, the contents of which are incorporated in their entirety herein by reference.
1. Field of the Invention
The present invention relates to a deformed folded dipole antenna in which two parallel sections coupled through short sections are deformed into U-shapes opposed to each other. The present invention also relates to a method of controlling an impedance of a deformed folded dipole antenna and an antenna device including a deformed folded dipole antenna.
2. Description of the Related Art
As an example of a folded dipole antenna, JP-A-2005-260567 discloses a deformed folded dipole antenna.
The deformed folded dipole antenna includes a pair of parallel sections (side portions 9, 12 and side portions 10, 13 in FIG. 1 of JP-A-2005-260567) arranged in parallel with each other and short sections (folded structure 11, 14) respectively coupling ends of the pair of parallel sections. One of the parallel sections (side portions 9, 12) has a feeding point at a middle point of an electric length in a longitudinal direction.
The other parallel section (side portions 10, 13) without a feeding point has a U-shape including a pair of opposing side portions opposed to each other and a connecting side portion (a portion between the folded structures 16, 18) connecting ends of the opposing side portions.
The parallel section (side portions 9, 12) having the feeding point includes two L-shape sections. One (side portion 9) of the L-shape sections is arranged in parallel with a part of the connecting side portion and one of the opposing side portions (side portion 10). The other (side portion 12) of the L-shape sections is arranged in parallel with a part of the connecting side portion and the other of the opposing side portions (side portion 13).
In the two L-shape sections (side portions 9, 12), portions (portions between the folded structures 15, 17) opposed to the connecting side portions (portions between the folded structures 16, 18) are opposed to each other at a predetermined distance therebetween and are arranged in the same straight line with each other. Accordingly, the two L-shape sections form a cut U-shape. The feeding point is provided at end portions of the L-shape sections opposed to the connecting side portion.
Thus, in the deformed folded dipole antenna, the two parallel sections opposed to each other are coupled through the short sections, one of the parallel sections has the U-shape, and the other of the parallel sections has the cut U-shape.
When a width of each parallel section is uniform throughout a longitudinal direction, an impedance of a folded dipole antenna can be controlled by changing a ratio of a width of a parallel section having a feeding point with respect to a width of a parallel section without a feeding point as described, for example, in JP-A-2004-228917.
When the conventional impedance control method is applied to the deformed folded dipole antenna having the U-shape, a width of the cut U-shape of the parallel section having the feeding point are set to be smaller than a width of the U-shape of the parallel section without a feeding point throughout the longitudinal direction of each parallel section.
For example, when two parallel sections in a deformed folded dipole antenna have the same width, in order to increase an impedance of the deformed folded dipole antenna, the width of the parallel section including the feeding points is decreased throughout the longitudinal direction and the width of the parallel section without a feeding point is increased throughout the longitudinal direction. In the above-described case, an outside dimension of the deformed folded dipole antenna along a plane on which the U-shape are arranged depends on an outside dimension of the parallel section without a feeding point whose width is increased. Thus, the outside dimension of the deformed folded dipole antenna is increased both in a direction along the opposing side portions and a direction along the connecting side potion. Especially in a deformed folded dipole antenna in which parallel sections have U-shapes, because two opposing side portions are arranged in parallel with each other in a direction perpendicular to a connecting side portion, an outside dimension in a direction along the connecting side portion is increased by an increased amount of the widths of the two opposing side portions.
In contrast, in order to decrease the impedance, the width of the parallel section including the feeding points is increased throughout the longitudinal direction compared with the width of the parallel section without a feeding point.
For example, when two U-shaped parallel sections in a deformed folded dipole antenna have the same width, in order to decrease an impedance of the deformed folded dipole antenna, the width of the parallel section including the feeding points is increased throughout the longitudinal direction and the width of the parallel section without a feeding point is decreased throughout the longitudinal direction. In the above-described case, an outside dimension of the deformed folded dipole antenna along a plane on which the U-shape is arranged depends on an outside dimension of the parallel section having the feeding points whose width is increased. Thus, the outside dimension of the antenna is increased both in a direction along the opposing side portions and a direction along the connecting side portion. Especially in a folded dipole antenna in which parallel sections have U-shapes, because two opposing side portions are arranged in parallel with each other in a direction perpendicular to a connecting side portion, an outside dimension in a direction along the connecting side portion is increased by an increased amount of the widths of both of the opposing side portions.
In this way, when an impedance of a deformed folded dipole antenna having a U-shape is controlled so as to ensure an impedance matching with an external device such a coaxial cable and a parallel feeder line, widths of two opposing end portions in one of parallel sections are larger than before controlling impedance, and thereby the outside dimension of the deformed folded dipole antenna along the connecting side portion may be increased.
An increase of the outside dimension may also be restricted by fixing the width of one parallel section and decreasing a width of the other parallel section. However, there is a manufacturing limitation in decreasing the width. Especially, in a small antenna originally having a small width, a control range of impedance is small.
In view of the foregoing problems, it is an object of the present invention to provide a deformed folded dipole antenna having a U-shape. Another object of the present invention is to provide a method of controlling an impedance of a deformed folded dipole antenna. Another object of the present invention is to provide an antenna device including a deformed folded dipole antenna.
According to first to third aspects of the present invention, methods of controlling an impedance of a deformed folded dipole antenna are provided. The deformed folded dipole antenna includes a first parallel section, a second parallel section, and two short sections. The first parallel section and the second parallel section are made of a conductive material and are arranged in parallel with each other along a plane. The short sections are made of a conductive material. Each of the short sections is shorter than the first parallel section and the second parallel section. Each of the short sections couples an end of the first parallel section with a corresponding end of the second parallel section. The second parallel section has a U-shape including a first opposing side portion, a second opposing side portion, and a connecting side portion. The first opposing side portion and the second opposing side portion are opposed to each other and the connecting side portion couples an end of the first opposing side portion with an end of the second opposing side portion. The first parallel section has a cut U-shape including a first L-shape section and a second L-shape section. The first L-shape section includes a portion arranged in parallel with the first opposing side portion and a portion arranged in parallel with a part of the connecting side portion. The second L-shape section includes a portion arranged in parallel with the second opposing side portion and a portion arranged in parallel with another part of the connecting side portion. The first L-shape section has a feeding point at an end of the portion arranged in parallel with the connecting side portion. The second L-shape section has a feeing point at an end of the portion arranged in parallel with the connecting side portion. The portion of the first L-shape section arranged in parallel with the connecting side portion is arranged in a same straight line with the portion of the second L-shape section arranged in parallel with the connecting side portion. The end of the first L-shape section is opposed to the end of the second L-shape section at a distance. The portion of the first L-shape section arranged in parallel with the first opposing side portion and the portion of the second L-shape section arranged in parallel with the second opposing side portion have a width W1 in a direction along the plane. The portion of the first L-shape section arranged in parallel with the connecting side portion and the portion of the second L-shape section arranged in parallel with the connecting side portion have a width W2 in the direction along the plane. The first opposing side portion and the second opposing side portion have a width W3 in the direction along the plane. The connecting side portion has a width W4 in the direction along the plane.
The method of controlling the impedance of the deformed folded dipole antenna according to the first aspect includes setting the width W2 to be larger than the widths W1, W3, and W4. In the present case, the impedance of the deformed folded dipole antenna can be increased compared with a case where the width W2 is equal to the width W4 and a case where the width W2 is smaller than the width W4.
The method of controlling the impedance of the deformed folded dipole antenna according to the second aspect includes setting the width W4 to be larger than the widths W1-W3. In the present case, the impedance of the deformed folded dipole antenna can be decreased compared with a case where the width W4 is equal to the width W2 and a case where the width W4 is smaller than the width W2.
The method of controlling the impedance of the deformed folded dipole antenna according to the third aspect includes controlling a ratio of the width W2 with respect to the width W4 in a state where the width W1 and the width W3 are fixed. The impedance can be increased by increasing the ratio W2/W4, and the impedance can be decreased by decreasing the ratio W2/W4. Because the width W1 and the width W3 are fixed, an increase of a dimension in a direction along the connecting side portion can be effectively restricted.
According to a fourth aspect of the present invention, a deformed folded dipole antenna includes a first parallel section, a second parallel section, and two short sections. The first parallel section and the second parallel section are made of a conductive material and are arranged in parallel with each other along a plane. The short sections are made of a conductive material. Each of the short sections is shorter than the first parallel section and the second parallel section. Each of the short sections couples an end of the first parallel section with a corresponding end of the second parallel section. The second parallel section has a U-shape including a first opposing side portion, a second opposing side portion, and a connecting side portion. The first opposing side portion and the second opposing side portion are opposed to each other and the connecting side portion couples an end of the first opposing side portion with an end of the second opposing side portion. The first parallel section has a cut U-shape including a first L-shape section and a second L-shape section. The first L-shape section includes a portion arranged in parallel with the first opposing side portion and a portion arranged in parallel with a part of the connecting side portion. The second L-shape section includes a portion arranged in parallel with the second opposing side portion and a portion arranged in parallel with another part of the connecting side portion. The first L-shape section has a feeding point at an end of the portion arranged in parallel with the connecting side portion. The second L-shape section has a feeing point at an end of the portion arranged in parallel with the connecting side portion. The portion of the first L-shape section arranged in parallel with the connecting side portion is arranged in a same straight line with the portion of the second L-shape section arranged in parallel with the connecting side portion. The end of the first L-shape section is opposed to the end of the second L-shape section at a distance. The portion of the first L-shape section arranged in parallel with the first opposing side portion and the portion of the second L-shape section arranged in parallel with the second opposing side portion have a width W1 in a direction along the plane. The portion of the first L-shape section arranged in parallel with the connecting side portion and the portion of the second L-shape section arranged in parallel with the connecting side portion have a width W2 in the direction along the plane. The first opposing side portion and the second opposing side portion have a width W3 in the direction along the plane. The connecting side portion has a width W4 in the direction along the plane. The width W2 is larger than the widths W1, W3, and W4.
In the deformed folded dipole antenna according to the fourth aspect, the impedance can be increased compared with a case where the width W2 is equal to the width W4 and a case where the width W2 is smaller than the width W4.
According to a fifth aspect of the present invention, an antenna device includes the deformed folded dipole antenna according to the fourth aspect, the connecting side portion is arranged in parallel with a vertical direction, and the first opposing side portion and the second opposing side portion are perpendicular to the vertical direction.
In the antenna device according to the fifth aspect, an antenna gain (vertically polarized wave gain) can be improved compared with a case where the connecting side portion and the portions of the first L-shape section and the second L-shape section arranged in parallel with the connecting side portion are perpendicular to the vertical direction. Furthermore, a directivity in a hemisphere face provided on an upper side of the deformed folded dipole antenna can be non-directional for a vertically polarized wave.
According to a sixth aspect of the present invention, a deformed folded dipole antenna includes a first parallel section, a second parallel section, and two short sections. The first parallel section and the second parallel section are made of a conductive material and are arranged in parallel with each other along a plane. The short sections are made of a conductive material. Each of the short sections is shorter than the first parallel section and the second parallel section. Each of the short sections couples an end of the first parallel section with a corresponding end of the second parallel section. The second parallel section has a U-shape including a first opposing side portion, a second opposing side portion, and a connecting side portion. The first opposing side portion and the second opposing side portion are opposed to each other and the connecting side portion couples an end of the first opposing side portion with an end of the second opposing side portion. The first parallel section has a cut U-shape including a first L-shape section and a second L-shape section. The first L-shape section includes a portion arranged in parallel with the first opposing side portion and a portion arranged in parallel with a part of the connecting side portion. The second L-shape section includes a portion arranged in parallel with the second opposing side portion and a portion arranged in parallel with another part of the connecting side portion. The first L-shape section has a feeding point at an end of the portion arranged in parallel with the connecting side portion. The second L-shape section has a feeing point at an end of the portion arranged in parallel with the connecting side portion. The portion of the first L-shape section arranged in parallel with the connecting side portion is arranged in a same straight line with the portion of the second L-shape section arranged in parallel with the connecting side portion. The end of the first L-shape section is opposed to the end of the second L-shape section at a distance. The portion of the first L-shape section arranged in parallel with the first opposing side portion and the portion of the second L-shape section arranged in parallel with the second opposing side portion have a width W1 in a direction along the plane. The portion of the first L-shape section arranged in parallel with the connecting side portion and the portion of the second L-shape section arranged in parallel with the connecting side portion have a width W2 in the direction along the plane. The first opposing side portion and the second opposing side portion have a width W3 in the direction along the plane. The connecting side portion has a width W4 in the direction along the plane. The width W4 is larger than the widths W1-W3.
In the deformed folded dipole antenna according to the sixth aspect, the impedance can be decreased compared with a case where the width W4 is equal to the width W2 and a case where the width W4 is smaller than the width W2.
According to a seventh aspect of the present invention, an antenna device includes the deformed folded dipole antenna according to the sixth aspect, the connecting side portion is arranged in parallel with a vertical direction, and the first opposing side portion and the second opposing side portion are perpendicular to the vertical direction.
In the antenna device according to the seventh aspect, an antenna gain (vertically polarized wave gain) can be improved compared with a case where the connecting side portion and the portions of the first L-shape section and the second L-shape section arranged in parallel with the connecting side portion are perpendicular to the vertical direction. Furthermore, a directivity in a hemisphere face provided on an upper side of the deformed folded dipole antenna can be non-directional for a vertically polarized wave.
Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings. In the drawings:
A process that the inventors of the present application created the present invention will be described before describing preferred embodiments of the present invention.
First of all, a conventional folded dipole antenna will be described with reference to
In folded dipole antennas, the inventors studied a deformed folded dipole antenna 20 as shown in
The deformed folded dipole antenna 20 can be used for a band range (2.5 GHz) of a Vehicle Information and Communication System (VICS). In Japan, “VICS” is a registered trademark of a Vehicle Information and Communication System Center. In other words, the deformed folded dipole antenna 20 can be configured to receive road traffic information.
The deformed folded dipole antenna 20 can be formed as shown in
The conductive films on the front surface 31 and the rear surface 32 are treated with patterning and the parallel sections 21 having U-shapes are formed. For example, the first parallel section 22 is formed on the front surface 31 and the second parallel section 23 is formed on the rear surface 32. Through holes 33 that penetrate the substrate 30 in a thickness direction of the substrate 30 are provided. By filling the through holes 33 with a conductive member, the short sections 24 coupling end portions of the feed parallel portion 22 with end portions of the second parallel sections 23 are formed. For example, each of the short sections 24 is formed by plating and has a diameter of 0.3 mm.
As shown in
A center line CL4 shown in
As described above, both of the opposing side portions 23a1 and 23a2 have the width W3, and both of the opposing side portions 23a1 and 23a2 have the length (electric length) L2. As shown in
The first parallel section 22 includes an L-shape section 40 and an L-shape section 41. The L-shape section 40 is arranged in parallel with a part of the connecting side portion 23b and the opposing side portion 23a1. The L-shape section 41 is arranged in parallel with a part of the connecting side portion 23b and the opposing side portion 23a2. The L-shape section 40 includes an opposing side portion 22a1 arranged in parallel with the opposing side portion 23a1 and a connecting side portion 22b1 arranged in parallel with a part of the connecting side portion 23b. The L-shape section 41 includes an opposing side portion 22a2 arranged in parallel with the opposing side portion 23a2 and a connecting side portion 22b2 arranged in parallel with a part of the connecting side portion 23b.
The first parallel section 22 receives electric power from an end of the connecting side portion 22b1 of the L-shape section 40 and an end of the connecting side portion 22b2 of the L-shape section 41. Thus, the L-shape section 40 has a feeding point at the end of the connecting side portion 22b1 arranged in parallel with the connecting side portion 23b, and the L-shape section 41 has a feeding point at the end of the connecting side portion 22b2 arranged in parallel with the connecting side portion 23b.
The connecting side portions 22b1 and 22b2 are arranged in the same straight line with each other in such a manner that the ends of the L-shape sections 40 and 41 functioning as the feeding points are opposed to each other at a distance. Accordingly, the first parallel section 22 has a cut U-shape. In the study, the distance between the ends of the L-shape sections 40 and 41 functioning as the feeding points is set to be 1 mm.
A center line CL1 shown in
Both of the opposing side portions 23a1 and 23a2 has a width W1, and both of the connecting side portions 23b1 and 23b2 arranged in the same straight line with each other have a width W2. The width W1 and the width W2 are widths in directions perpendicular to a flow direction of electric current.
Both of the opposing side portions 22a1 and 22a2 have the length (electric length) L2 that is same as the length of the opposing side portions 23a1 and 23a2. As shown in
The deformed folded dipole antenna 20 has an outside dimension V1 in the V-direction. The outside dimension V1 is at least one of an outside dimension of the first parallel section 22 in the V-direction and an outside dimension of the second parallel section 23 in the V-direction which is longer. In the example shown in
The deformed folded dipole antenna 20 has an outside dimension H1 in the H-direction. The outside dimension H1 is at least one of an outside dimension of the first parallel section 22 in the H-direction and an outside dimension of the second parallel section 23 in the H-direction which is longer. In the example shown in
The inventors prepared various samples of the deformed folded dipole antennas 20 in which the widths W1-W4 are changed and measured an impedance R (Ω) of each antenna.
A conventional impedance control method will be described below. In the conventional impedance controlling method, the width W1 of the opposing side portions 22a1 and 22a2 is equal to the width W2 of the connecting side portions 22b1 and 22b2, and the width W3 of the opposing side portions 23a1 and 23a2 is equal to the width W4 of the connecting side portion 23b. Then, the impedance is controlled by controlling a ratio W1/W3, that is, a ratio of the width W1 (=W2) of the first parallel section 22 with respect to the width W3 (=W4) of the second parallel section 23.
In a case where all the widths W1-W4 of the deformed folded dipole antenna 20 are equal to each other (specifically, 1 mm) as shown in
In other words, in a case where the widths W1 and W2 of the first parallel section 22 having the feeding points are larger than the widths W3 and W4 of the second parallel section 23 without a feeding point, the impedance R of the deformed folded dipole antenna 20 decreases. In a case where the widths W1 and W2 of the first parallel section 22 having the feeding points are smaller than the widths W3 and W4 of the second parallel section 23 without a feeding point, the impedance R of the deformed folded dipole antenna 20 increases. This result is known.
In the example shown in
In this way, in the conventional impedance control method, the widths of the first parallel section 22 and the second parallel section 23 are changed throughout the longitudinal direction. Thus, when the impedance of the deformed folded dipole antenna 20 having the U-shape is controlled by the conventional method for ensuring an impedance matching with an external device such as a coaxial cable having an impedance of 50 Ω or 75Ω, the widths of two opposing side portions of one of the first parallel section 22 and the second parallel section 23 are larger than before controlling impedance, and the outside dimension of the deformed folded dipole antenna 20 in a direction along the connecting side portion (V-direction) may be increased.
For example, in a case where the impedance of the deformed folded dipole antenna 20 in which all the widths W1-W4 are equal to each other as shown in
In contrast, in a case where the impedance of the deformed folded dipole antenna 20 in which all the widths W1-W4 are equal to each other as shown in
In this way, in the conventional impedance control method in which the width is changed throughout the longitudinal direction, the widths of the opposing side portions of one of the first parallel section 22 and the second parallel section 23 become larger than before controlling, and thereby the outside dimension in the V-direction is increased.
An increase of the outside dimension may also be restricted by fixing the width of one of the parallel sections 22 and 23 and decreasing the width of the other of the parallel sections 22 and 23. However, there is a manufacturing limitation in decreasing the width. Especially, in a small antenna originally having a small width, a control range of impedance is small.
Thus, the inventors made a study on whether the impedance can be controlled by changing only the widths W2 and W4 of the connecting side portions. The results of the study are shown in
In a case where the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 is 1 mm and the width W4 of the connecting side portion 23b of the second parallel section 23 is 3 mm, that is, in a case where the width W2 is smaller than the width W4 as shown in
In a case where the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 is 3 mm and the width W4 of the connecting side portion 23b of the second parallel section 23 is 3 mm, that is, in a case where the width W2 is equal to the width W4 as shown in
In a case where the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 is 3 mm and the width W4 of the connecting side portion 23b of the second parallel section 23 is 1 mm, that is, in a case where the width W2 is larger than the width W4 as shown in
In addition, the inventors found that there is no difference in directivity of the examples shown in
From the above-described study, the inventors obtained the knowledge that the impedance of the deformed folded dipole antenna can be controlled as follows without changing the width W1 of the opposing side portions 22a1 and 22a2 of the first parallel section 22 and the width W3 of the opposing side portions 23a1 and 23a2 of the second parallel section 23.
(i) By setting the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 to be larger than the width W4 of the connecting side portion 23b of the second parallel section 23 (W2>W4), the impedance of the deformed folded dipole antenna 20 can be increased compared with a case where the width W2 is equal to the width W4 (W2=W4) and a case where the width W2 is smaller than the width W4 (W2<W4).
(ii) By setting the width W4 of the connecting side portion 23b of the second parallel section 23 to be larger than the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 (W4>W2), the impedance of the deformed folded dipole antenna 20 can be decreased compared with a case where the width W4 is equal to the width W2 (W4=W2) and a case where the width. W4 is smaller than the width W2 (W4<W2).
(iii) By setting the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 to be larger than the widths W1, W3, and W4, the impedance of the deformed folded dipole antenna 20 can be increased.
(iv) By setting the width W4 of the connecting side portion 23b of the second parallel section 23 to be larger than the widths W1-W3, the impedance of the deformed folded dipole antenna 20 can be decreased.
The present invention is based on the above-described knowledge (i)-(iv).
A deformed folded dipole antenna 20 according to a first embodiment of the present invention will be described with reference to
A configuration of a deformed folded dipole antenna 20 according to the present embodiment is similar to the configuration of the deformed folded dipole antenna 20 shown in
In the direction along the plane, outside dimensions of the substrate 30 correspond to the outside dimensions V1 and H1 of the deformed folded dipole antenna 20 so that the outside dimensions of the deformed folded dipole antenna 20 including the substrate 30 can be small.
The width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 is larger than the width W4 of the connecting side portion 23b of the second parallel section 23 (W2>W4). Thus, the impedance of the folded dipole antenna 20 can be larger than a case where the width W2 is equal to the width W4 (W2=W4) and a case where the width W2 is smaller than the width W4 (W2<W4).
The width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 is larger than the width W1 of the opposing side portions 22a1 and 22a2 of the first parallel section 22, the width W3 of the opposing side portions 23a1 and 23a2 of the second parallel section 23, and the width W4 of the connecting side portion 23b of the second parallel section 23. Thus, an increase of the outside dimension V1 in the V-direction can be restricted.
In the deformed folded dipole antenna 20 according to the present embodiment, the outside dimension V1 in the V-direction can be restricted, and the impedance can be larger than before controlling.
The first parallel section 22 and the second parallel section 23 are formed by patterning a conductive film on the front surface 31 and the rear surface 32 of the substrate 30 made of a dielectric material, and the short sections 24 are formed by filling the through holes 33 provided in the substrate 30 with a conductive material. Because the deformed folded dipole antenna 20 is formed by using a part of a multilayer substrate, a configuration of the deformed folded dipole antenna 20 can be simplified and a manufacturing cost can be reduced compared with a case where at least a part of the parallel sections 22 and 23 and the short sections 24 are made of a metal plate or a metal wire. Furthermore, the dimensions of the deformed folded dipole antenna 20 can be decreased by gaining a line length due to a wavelength shortening effect of the substrate 30 made of the dielectric material.
An impedance control method for obtaining the deformed folded dipole antenna 20 according to the present embodiment will be described below.
The width W1 of the opposing side portions 22a1 and 22a2 of the first parallel section 22 and the width W3 of the opposing side portions 23a1 and 23a2 of the second parallel section 23 are fixed, and a ratio W2/W4, that is a ratio of the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 with respect to the width W4 of the connecting side portion 23b of the second parallel section 23 is changed.
The width W2 and the width W4 are controlled in a range where the ratio W2/W4 is larger than 1, that is, in a range where the width W2 is larger than the width W4 (W2>W4), so that the impedance of the deformed folded dipole antenna 20 is larger than before controlling and the impedance of the deformed folded dipole antenna 20 is substantially equal to the impedance (50Ω) of a coaxial cable. That is, the impedance matching with the coaxial cable is ensured.
In the impedance control method according to the present embodiment, as described in the knowledge (i), the impedance of the deformed folded dipole antenna 20 is increased by setting the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 to be larger than the width W4 of the connecting side portion 23b of the second parallel section 23 (W2>W4) without changing the width W1 of the opposing side portions 22a1 and 22a2 of the first parallel section 22 and the width W3 of the opposing side portions 23a1 and 23a2 of the second parallel section 23. Thus, an increase of the outside dimension V1 in the V-direction can be effectively restricted.
In the above-described example, the width W4 is fixed. Alternatively, the width W4 may also be decreased so that the ratio W2/W4 is further increased and the impedance is further increased.
In the above-described example, the impedance is increased by controlling the widths W2 and W4 while fixing the widths W1 and W3. Alternatively, as described in the knowledge (iii), the impedance of the deformed folded dipole antenna 20 can be increased by setting the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 to be larger than the widths W1, W3, and W4. Thus, the widths W1 and W3 may also be changed in such a manner that, the above-described relationship is satisfied. In a modification shown in
A deformed folded dipole antenna 20 according to a second embodiment of the present invention will be described with reference to
Also in the deformed folded dipole antenna 20 according to the present embodiment, outside dimensions of the substrate 30 correspond to the outside dimensions V1 and H1 of the deformed folded dipole antenna 20 in the direction along the plane so that the outside dimensions of the deformed folded dipole antenna 20 including the substrate 30 can be small.
As described above, in the deformed folded dipole antenna 20 according to the present embodiment, the width W4 of the connecting side portion 23b of the second parallel section 23 is larger than the width W2 of the connecting side portions 22b1 and 22b2 of first parallel section (W4>W2). Thus, the impedance of the deformed folded dipole antenna 20 can be smaller than a case where the width W2 is equal to the width W4 (W2=W4) and when the width W4 is smaller than the width W2 (W4<W2).
In addition, the width W4 of the connecting side portion 23b of the second parallel section 23 is larger than the width W1 of the opposing side portions 22a1 and 22a2 of the first parallel section 22, the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22, and the width W3 of the opposing side portions 23a1 and 23a2 of the second parallel section 23. Thus, an increase of the outside dimension V1 in the V-direction can be restricted.
In the deformed folded dipole antenna 20 according to the present embodiment, the outside dimension V1 in the V-direction can be restricted, and the impedance can be smaller than before controlling.
The first parallel section 22 and the second parallel section 23 are formed by patterning a conductive film on the front surface 31 and the rear surface 32 of the substrate 30 made of a dielectric material, and the short sections 24 are formed by filling the through holes 33 provided in the substrate 30 with a conductive material. Thus, the configuration of the deformed folded dipole antenna 20 can be simplified and a manufacturing cost can be reduced. Furthermore, the dimensions of the deformed folded dipole antenna 20 can be decreased by gaining a line length due to a wavelength shortening effect of the substrate 30 made of the dielectric material.
An impedance control method for obtaining the deformed folded dipole antenna 20 according to the present embodiment will be described below.
Also in the deformed folded dipole antenna 20 according to the present embodiment, the width W1 of the opposing side portions 22a1 and 22a2 of the first parallel section 22 and the width W3 of the opposing side portions 23a1 and 23a2 of the second parallel section 23 are fixed, and a ratio W2/W4, that is a ratio of the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 with respect to the width W4 of the connecting side portion 23b of the second parallel section 23 is changed.
The width W2 and the width W4 are controlled in a range where the ratio W2/W4 is smaller than 1, that is, in a range where the width W4 is larger than the width W2 (W4>W2), so that the impedance of the deformed folded dipole antenna 20 becomes a predetermined value smaller than before controlling.
In the impedance control method according to the present embodiment, as described in the knowledge (ii), the width W4 of the connecting side portion 23b of the second parallel section 23 is set to be larger than the width W2 of the connecting side portions 22b1 and 22b2 of the first parallel section 22 (W4>W2) without changing the width W1 of the opposing side portions 22a1 and 22a2 of the first parallel section 22 and the width W3 of the opposing side portions 23a1 and 23a2 of the second parallel section 23 so that the impedance of the deformed folded dipole antenna 20 is decreased compared with a case were the width W4 is equal to the width W2 (W4=W2) and a case where the width W4 is smaller than the width W2 (W4<W2). Thus, an increase of the outside dimension V1 in the V-direction can be effectively restricted.
In the above-described example, the width W2 is fixed. Alternatively, the width W2 may also be decreased so that the ratio W2/W4 is further decreased and the impedance is further decreased.
In the above-described example, the impedance is decreased by controlling the widths W2 and W4 while fixing the widths W1 and W3. Alternatively, as described in the knowledge (iv), the impedance of the deformed folded dipole antenna 20 can be decreased by setting the width W4 of the connecting side portion 23b of the second parallel section 23 to be larger than the widths W1-W3. Thus, the widths W1 and W3 may also be changed in such a manner that the above-described relationship is satisfied. The impedance can be further decreased by changing at least one of the widths W1 and W3 in such a manner that the ratio W1/W3 is increased.
An antenna device 100 according to a third embodiment of the present invention will be described with reference to
In
The antenna device 100 includes a housing in which a deformed folded dipole antenna 20 and a global positioning system antenna (GPS antenna) 50 are disposed. The deformed folded dipole antenna 20 may be one of the deformed folded dipole antennas 20 described above. The deformed folded dipole antenna 20 is configurated to receive road traffic information. The GPS antenna 50 is configured as a so-called patch antenna. The GPS antenna 50 includes a dielectric body having a rectangular parallel piped shape. On a first surface of the dielectric body, a radiating element 50a is disposed. On a second surface of the dielectric body opposed to the first surface, a ground (not shown) is formed.
The housing includes a case having an opening at one side and a cover 60 that covers the opening. In the example shown in
The deformed folded dipole antenna 20 and the GPS antenna 50 are disposed on a substrate 51. The substrate 51 can function as a common substrate. The substrate 51 has a first surface 51a and a second surface 51b opposed to the first surface 51a. The GPS antenna 50 is mounted on the substrate 51 in such a manner that the second surface of the dielectric body opposes the first surface 51a of the substrate 51. The substrate 51 has a through hole extending from the first surface 51a to the second surface 51b. The substrate 30 of the deformed folded dipole antenna 20 is inserted into the through hole. The substrate 30 is supported by a supporting member 52.
On the substrate 51, a matching circuit and a wireless circuit are formed. The deformed folded dipole antenna 20 and the GPS antenna 50 are electrically coupled with the matching circuit and the wireless circuit. The circuits formed on the substrate 51 are coupled with a connector (not shown) through a coaxial cable (not shown). The connector is coupled, for example, with a navigation device. On the second surface 51b of the substrate 51, an electromagnetic wave shielding member 53 is disposed.
The substrate 51 is disposed on a surface 60a of the cover 60 through the electromagnetic wave shielding member 53. In this way, the deformed folded dipole antenna 20 and the GPS antenna 50 are disposed above the cover 60.
Each of the deformed folded dipole antenna 20 and the GPS antenna 50 receives radio wave from infrastructures including a satellite and a device on a road. Arrival directions of the radio wave are directions within a hemisphere face provided on the upper side of each of the deformed folded dipole antenna 20 and the GPS antenna 50 in the vertical direction. Thus, it is preferred that each of the deformed folded dipole antenna 20 and the GPS antenna 50 is disposed in such a manner that the directivity in the hemisphere face is non-directional for a polarized wave. In the GPS antenna 50, the polarized wave is a right-handed circularly polarized wave. In the deformed folded dipole antenna 20, the polarized wave is a vertically polarized wave. In the antenna device 100 according to the present embodiment, the first surface 51a and the second surface 51b of the substrate 51 are arranged in parallel with the surface 60a of the cover 60, which can function as the ground plane, and the first surface of the GPS antenna 50 on which the radiating element 50a is formed is arranged in parallel with the surface 60a of the cover 60. The substrate 30 of the deformed folded dipole antenna 20 is inserted in the through hole of the substrate 51 in such a manner that the connecting side portions 22b1, 22b2, and 23b are parallel with a thickness direction of the substrate 51 and the opposing side portions 22a1, 22a2, 23a1, and 23a2 are perpendicular to the thickness direction of the substrate 51. Thus, the connecting side portions 22b1, 22b2, and 23b are perpendicular to the surface 60a of the cover 60, and the opposing side portions 22a1, 22a2, 23a1, and 23a2 are parallel with the surface 60a of the cover 60. Thus, when the antenna device 100 is mounted on a vehicle in such a manner that the surface 60a of the cover is perpendicular to the vertical direction of the vehicle, the first surface of the GPS antenna 50 on which the radiating element 50a is formed is perpendicular to the vertical direction. In addition, the connecting side portions 22b1, 22b2, and 23b of the deformed folded dipole antenna 20 are parallel with the vertical direction, and the opposing side portions 22a1, 22a2, 23a1, and 23a2 are perpendicular to the vertical direction.
In the antenna device 100, the connecting side portions 22b1, 22b2, and 23b close to the feeding points and having high current density are arranged in parallel with the vertical direction. Thus, an antenna gain (vertically polarized wave gain) can be improved compared with a case where the connecting side portions 22b1, 22b2, and 23b are perpendicular to the vertical direction. Furthermore, the directivity in the hemisphere face provided on the upper side of the deformed folded dipole antenna 20 can be non-directional for a vertically polarized wave.
Because the deformed folded dipole antenna 20 and the GPS antenna 50 are disposed on the common substrate 51, a configuration of the antenna device 100 can be simplified. In addition, in each of the deformed folded dipole antenna 20 and the GPS antenna 50, the directivity in the hemisphere face can be non-directional for the polarized wave of each antenna.
In the opposing side portions 22a1, 22a2, 23a1, and 23a2, the opposing side portions 22a1 and 23a1 are called first opposing side portions, and the opposing side portions 22a2 and 23a2 are called second opposing side portions. The inventors found that, in a case where a length of the first opposing side portions 22a1 and 23a1 is equal to a length of the second opposing side portions 22a2 and 23a2, and a metal member is closer to the second opposing side portions 22a2 and 23a2 than the first opposing side portions 22a1 and 23a1, a distortion is generated in the directivity for a vertically polarized wave in the hemisphere face provided on the upper side of the deformed folded dipole antenna 20, that is, in a vertical directivity. An example of the distortion is shown in
The inventors studied in order to improve the distortion, that is, to improve the non-directivity. When electric current flows in the second opposing side portions 22a2 and 23a2 close to the metal member (for example, the cover 60 as the ground plane), image current is induced in the metal member. The inventors thought that the distortion is caused by the image current and set the electric length of the second opposing side portions 22a2 and 23a2 including the image current to be equal to the electric length of the first opposing side portions 22a1 and 23a1. In other words, as shown in
The directivity for a vertically polarized wave in the deformed folded dipole antenna 20 shown in
In the antenna device 100 according to the present embodiment, in view of the image current, the length L2b of the second opposing side portions 22a2 and 23a2 is set to shorter than the length L2a of the first opposing side portions 22a1 and 23a1. Thus, the non-directivity for a vertically polarized wave in the hemisphere face provided on the upper side in the vertical direction can be improved compared with a case where the length L2b of the second opposing side portions 22a2 and 23a2 is equal to the length L2a of the first opposing side portions 22a1 and 23a1.
In the example shown in
The antenna device 100 may also include only the deformed folded dipole antenna 20 as an antenna, and the connecting side portions 22b1, 22b2, and 23b close to the feeding points and having the high current density may be arranged in parallel with the vertical direction. Accordingly, an antenna gain of the deformed folded dipole antenna 20 can be improved. In addition, the directivity for a vertically polarized wave in the hemisphere face provided on the upper side in the vertical direction can be non-directional.
In the example shown in
In the example shown in
In the above-described example, the deformed folded dipole antenna 20 is configured to receive road traffic information. The deformed folded dipole antenna 20 may also be used as a vertically-polarized wave antenna for other application including, for example, a telephone antenna for mobile communication.
In the example shown in
In the above-described example, the width W4 is fixed. The impedance can be further increased by setting the width W4 to be smaller than before controlling and thereby increasing the ratio W2/W4.
In the example shown in
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.
Applications of the deformed folded dipole antenna 20 is not limited to an antenna for receiving road traffic information, and the deformed folded dipole antenna 20 may also be used as an antenna for other device including a wireless device and a portable device.
In the above-described embodiments, the first parallel section 22 and the second parallel section 23 are formed by patterning the conductive layers disposed on the front surface 31 and the rear surface 32 of the substrate 30, and the short sections 24 are interlayer connectors formed by filling the through holes 33 penetrating the substrate 30 with the conductive member. The configuration using the substrate 30 is not limited to the above-described example.
For example, the deformed folded dipole antenna 20 may include the substrate 30 made of an insulating material and including a plurality of conductive patterns arranged in a thickness direction, each of the first parallel section 22 and the second parallel section 23 may be provided by one of the conductive patterns, and the short section 24 may be provided by interlayer connectors formed by filling holes in the substrate 30 with a conductive material. At least one of the first parallel section 22 and the second parallel section 23 may also be provided by an internal layer pattern in the substrate 30. When the internal layer pattern is used, the interlayer connectors as the short section 24 are connecting via holes formed by filling via holes in the substrate 30 with a conductive material.
Alternatively, the substrate 30 may not include the interlayer connectors, and the first parallel section 22 and the second parallel section 23 located in different layers may be electrically coupled with a conductive member through a side surface of the substrate 30.
The deformed folded dipole antenna 20 may also be formed by using a metal plate and a metal wire instead of the substrate 30.
In the above-described embodiments, in the first parallel section 22 and the second parallel section 23, the electric length L2 in the H-direction is longer than the electric length L3 in the V-direction. Alternatively, the electric length L2 in the H-direction may also be shorter than the electric length L3 in the V-direction. Also in this case, the configuration and the impedance control methods described above can be applied.
As described above, the impedance of the folded dipole antenna is about 293Ω. In the example shown in
A dielectric member may be disposed at a region between the pair of opposing side portions 22a1 and 22a2 or 23a1 and 23a2. In this case, the dimensions of the deformed folded dipole antenna 20 can be decreased by gaining a line length due to a wavelength shortening effect.
In the above-described embodiments, the widths W1 and W3 are controlled while fixing the distance between the center lines CL1 and CL2 and the distance between the center lines CL4 and CL5. In other words, for example, in the opposing side portion 22a1, the width W1 is controlled in such a manner the widths on both sides of the center line CL1 are equal to each other. Alternatively, for example, in the opposing side portion 22a1, the width W1 may also be controlled in such a manner that the widths are different on both sides of the center line CL1.
The current density of the deformed folded dipole antenna 20 increases toward the feeding points and decreases towards the ends of the U-shape coupled with the short sections 24. Thus, the widths of the parallel sections 21 may be changed from the feeding points toward the ends. For example, the width may be decreased from a portion close to the feeding points where the current density is high to the ends of the U-shape. Accordingly, an arrangement area of the deformed folded dipole antenna 20 can be decreased. For example, in the substrate 30, a forming area of the deformed folded dipole antenna 20 can be decreased, and a mounting area of other parts can be ensured.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-265491 | Nov 2009 | JP | national |
| 2010-214051 | Sep 2010 | JP | national |
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| Office action dated Nov. 15, 2011 in corresponding Japanese Application No. 2010-214051. |
| Number | Date | Country | |
|---|---|---|---|
| 20110122038 A1 | May 2011 | US |
