Stack antenna

Abstract

To provide a compact stack antenna that can be used in two different frequency bands.SOLUTION: A stack antenna 1 includes a first antenna in which first and second stages each consisting of two sets of dipole antennas are stacked in two stages, and a second antenna in which slot elements A-1 to A-4 are stacked in four stages. A pair of hot elements 11b-1, 11b-2 and a pair of earth elements 11a-1, 11a-2 constituting the first and second stages of the dipole antennas are formed on the surface of a substrate 10. The slot elements A-1 to A-4 are arranged to surround the center portions of the dipole antennas and are arranged between the stages of the dipole antennas. Since the first antenna and the second antenna are arranged inside each other, the stack antenna 1 can be miniaturized.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a broadband, compact stack antenna. [Background technology]

[0002] A conventional wideband antenna that is mainly used in communication modules and broadband communications is disclosed in Reference 1. The configuration of the conventional wideband antenna 100 disclosed in Reference 1 is shown in FIG. The conventional wideband antenna 100 shown in Fig. 19 is configured by vertically stacking four conventional wideband antennas 200 shown in Fig. 20(a) and (b). The conventional wideband antenna 200 shown in Fig. 20(a) and (b) will now be described. Fig. 20(a) is a front view showing the configuration of the conventional wideband antenna 200, and Fig. 20(b) is a bottom view showing the configuration of the conventional wideband antenna 200. The conventional wideband antenna 200 shown in these figures is composed of a first-stage element consisting of two dipole elements each consisting of two hot elements 211b-1 and two earth elements 211a-1, and a pair of parasitic elements C-201 with an arc-shaped cross section arranged closely surrounding the dipole elements, and a second-stage element consisting of two dipole elements each consisting of two hot elements 211b-2 and two earth elements 211a-2, and a pair of parasitic elements C-202 with an arc-shaped cross section arranged closely surrounding the dipole elements.

[0003] The two hot elements 211b-1, 211b-2 and the two earth elements 211a-1, 211a-2 are formed on a vertically elongated rectangular substrate 210 such as a fluororesin substrate having good high frequency characteristics. In this case, two hot elements 111b-1 are formed in a vertically elongated rectangular shape along the longitudinal direction of both edges at the bottom of one surface of the substrate 210, and two hot elements 211b-2 are formed in a vertically elongated rectangular shape along the longitudinal direction of both edges at the top of the center of one surface of the substrate 210. Furthermore, two earth elements 111a-1 are formed in a vertically elongated rectangular shape along the longitudinal direction of both edges at the bottom of the center of the other surface of the substrate 210, and two earth elements 211a-2 are formed in a vertically elongated rectangular shape along the longitudinal direction of both edges at the top of the other surface of the substrate 210. The hot element 211b-1 and the earth element 211a-1 are formed opposite each other, and two pairs of dipole antennas are configured in the first stage elements, while the hot element 211b-2 and the earth element 211a-2 are formed opposite each other, and two pairs of dipole antennas are configured in the second stage elements. In the first stage element, a pair of parasitic elements C-201, each having a cross section shaped like an arc with a radian angle of θ3, are arranged symmetrically in close proximity to the dipole antenna consisting of the hot element 211b-1 and the earth element 211a-1. Similarly, in the second stage element, a pair of parasitic elements C-202, each having a cross section shaped like an arc with a radian angle of θ3, are arranged symmetrically in close proximity to the dipole antenna consisting of the hot element 211b-2 and the earth element 211a-2.

[0004] A power feed point 213 is disposed at approximately the center of the substrate 210, and a branch line 214 connected to the hot side of the power feed point 213 is formed on one surface of the substrate 210 so as to extend vertically approximately along the center line in the longitudinal direction. The upper ends of a pair of hot elements 211b-1 of the first stage elements are connected to the branch line 214 extending downward from the power feed point 213, and the upper ends of a pair of hot elements 211b-2 of the second stage elements are connected to the branch line 214 extending upward from the power feed point 213. In addition, a ground line 215 connected to the ground side of the power feed point 213 is formed wide on the other surface of the substrate 210 so as to extend vertically approximately along the center line in the longitudinal direction. The lower ends of a pair of ground elements 211a-1 of the first stage element are connected to ground line 215 extending downward from feed point 213, and the lower ends of a pair of ground elements 211a-2 of the second stage element are connected to ground line 215 extending upward from feed point 213. As a result, power is fed in parallel from feed point 213 to the dipole antennas of the first and second stage elements via the transmission line consisting of branch line 214 and ground line 215. The branch line 214 formed on one surface of the substrate 210 is formed on a wide earth line 215 formed on the other surface of the substrate 210, and the above transmission line is a strip line.

[0005] The conventional wideband antennas 200 configured as described above are stacked vertically in four stages to form the conventional wideband antenna 100 shown in Fig. 19. Since the conventional wideband antennas 200 are stacked in two stages, the conventional wideband antenna 100 is stacked in eight stages as shown in Fig. 19. The first stage is composed of two dipole antennas each consisting of two hot elements 111b-1 and two earth elements 111a-1, and a pair of parasitic elements C-101 arranged closely to surround the two dipole antennas, and the second stage is composed of two dipole antennas each consisting of two hot elements 111b-2 and two earth elements 111a-2, and a pair of parasitic elements C-102 arranged closely to surround the two dipole antennas. The third through eighth stages are similarly configured, with each stage consisting of two dipole antennas each consisting of two hot elements 111b-3 to 111b-8 and two earth elements 111a-3 to 111a-8, and a pair of parasitic elements C-103 to C-108 arranged closely surrounding the two dipole antennas. In the conventional wideband antenna 100, power is fed in parallel to the first to eighth stages of dipole antennas in a tournament fashion from a feeding point (not shown). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5964487 Summary of the Invention [Problem to be solved by the invention]

[0007] When using a conventional broadband antenna 100 in two different frequency bands, it was necessary to connect multiple antenna stages configured to operate in each frequency band at the top and bottom, which resulted in the antenna needing to be twice as long, resulting in a problem of the antenna becoming large.

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a small stack antenna that can be used in two different frequency bands. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the stack antenna of the present invention comprises a first antenna in which dipole antennas composed of a hot element and an earth element are stacked in n (n is a power of 2) stages, and a second antenna in which arc-shaped slot elements are stacked in 2n stages, and the first antenna and the second antenna are configured by being disposed inside each other, and the most main feature is that the second installation spacing of the slot elements of the second antenna is 1 / 2 of the first installation spacing of the dipole antenna of the first antenna. Effect of the Invention

[0010] The stack antenna of the present invention comprises a first antenna in which dipole antennas, each consisting of a hot element and an earth element, are stacked in n (n is a power of 2) stages, and a second antenna in which arc-shaped slot elements are stacked in 2n stages, and since the first antenna and the second antenna are arranged inside each other, it is not necessary to increase the length of the stack antenna, and the stack antenna can be made smaller. In this case, the slot elements are arranged so as to surround the center of the dipole antenna and are arranged between the stages of the dipole antenna, so that the installation interval at which the slot elements are installed is half the installation interval at which the dipole antennas are installed, and the desired half-value angle and side lobe characteristics can be satisfied. [Brief description of the drawings]

[0011] [Figure 1] 1A and 1B are a front view and a side view showing the configuration of a stack antenna according to a first embodiment of the present invention [Diagram 2] 1 is a bottom view showing the configuration of a stack antenna according to a first embodiment of the present invention. [Diagram 3]1 is a front view showing a configuration of a substrate in a stack antenna according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a development view showing the configuration of a slot element in the stack antenna according to the first embodiment of the present invention. [Diagram 5] 11A and 11B are front and rear views showing the configuration of a stack antenna according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a bottom view showing the configuration of a stack antenna according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a front view showing the configuration of a substrate in a stack antenna according to a second embodiment of the present invention. [Figure 8] 2 is a perspective view showing multiple configurations of slot elements in a stack antenna according to an embodiment of the present invention; FIG. [Figure 9] FIG. 11 is a front view showing the configuration of a stack antenna according to a third embodiment of the present invention. [Figure 10] FIG. 11 is a diagram showing the directional characteristics of a stack antenna according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing another directional characteristic of the stack antenna according to the third embodiment of the present invention. [Figure 12] 1 is a graph showing a half-value angle versus the installation interval of an antenna of a stack antenna according to an embodiment of the present invention. [Figure 13] 1 is a graph showing the side lobe level versus the antenna installation interval of a stack antenna according to an embodiment of the present invention. [Figure 14] 13A to 13C are front views showing three configurations of the stack antenna according to the fourth embodiment of the present invention. [Figure 15] 13A and 13B are a left side view and a front view showing the configuration of a stack antenna according to a fifth embodiment of the present invention. [Figure 16] 13A and 13B are a right side view and a rear view showing the configuration of a stack antenna according to a fifth embodiment of the present invention. [Figure 17] FIG. 13 is a development view showing the configuration of slot elements in a stack antenna according to a fifth embodiment of the present invention. [Figure 18] 1A and 1B are diagrams for explaining the number of stages and antenna characteristics in a stack antenna of the present invention. [Figure 19] FIG. 1 is a front view showing the configuration of a conventional wideband antenna. [Figure 20] 1A and 1B are a front view and a bottom view showing a configuration of a conventional wideband antenna; [Figure 21] FIG. 1 is a diagram showing the directional characteristics of a conventional wideband antenna. [Figure 22] FIG. 1 is a diagram showing another directional characteristic of a conventional wideband antenna. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Stack antenna according to the first embodiment of the present invention> FIG. 1(a) is a front view showing the configuration of a stack antenna 1 of the first embodiment of the present invention, FIG. 1(b) is a side view thereof, FIG. 2 is a bottom view thereof, FIG. 3 is a front view showing the configuration of the substrate in the stack antenna 1 of the first embodiment, and FIG. 4 is an expanded view of the slot elements in the stack antenna 1 of the first embodiment. The stack antenna 1 of the first embodiment of the present invention shown in these figures is composed of a first antenna in which a first stage and a second stage each composed of two sets of dipole antennas are stacked in two stages, and a second antenna in which slot elements A-1 to A-4 are stacked in four stages. The first stage of the first antenna is composed of two sets of dipole antennas composed of a pair of hot elements 11b-1 and a pair of earth elements 11a-1, and the second stage is composed of two sets of dipole antennas composed of a pair of hot elements 11b-2 and a pair of earth elements 11a-2. As shown in FIG. 3, the pair of hot elements 11b-1, the pair of hot elements 11b-2, the pair of earth elements 11a-1, and the pair of earth elements 11a-2 are formed on a substrate 10 such as a fluororesin substrate having good high-frequency characteristics. That is, on the lower part of one surface of the substrate 10 having a vertically elongated rectangular shape, a pair of hot elements 11b-1 constituting the first stage are formed in a vertically elongated rectangular shape facing each other along the longitudinal direction of both edges. Moreover, above the center of one surface of the substrate 10, a pair of hot elements 11b-2 constituting the second stage are formed in a vertically elongated rectangular shape facing each other along the longitudinal direction of both edges. Furthermore, below the center of the other surface of the substrate 10, a pair of earth elements 11a-1 constituting the first stage are formed in a vertically elongated rectangular shape facing each other along the longitudinal direction of both edges. Moreover, above the other surface of the substrate 10, a pair of earth elements 11a-2 constituting the second stage are formed in a vertically elongated rectangular shape facing each other along the longitudinal direction of both edges. In the first stage of the first antenna, a pair of hot elements 11b-1 and a pair of earth elements 11a-1 are formed facing each other vertically, so that two dipole antennas are formed. In the second stage of the first antenna, a pair of hot elements 11b-2 and a pair of earth elements 11a-2 are formed facing each other vertically, so that two dipole antennas are formed.

[0013] In the first stage of the first antenna, an arc-shaped slot element A-1 having a radian angle of θ1 is arranged adjacently to two dipole antennas each consisting of a pair of hot elements 11b-1 and a pair of earth elements 11a-1, and in the second stage, an arc-shaped slot element A-3 having a radian angle of θ1 is arranged adjacently to two dipole antennas each consisting of a pair of hot elements 11b-2 and a pair of earth elements 11a-2. In addition, between the first stage and the second stage, an arc-shaped slot element A-2 having a radian angle of θ1 is arranged adjacently to surround the substrate 10, and an arc-shaped slot element A-4 having a radian angle of θ1 is arranged adjacently to surround the upper end of the substrate 10. In this case, the slot elements A-1 to A-4 are arranged on a circle whose center is approximately the central axis of the substrate 10.

[0014] The slot elements A-1 to A-4 constitute a second antenna stacked in four stages. That is, the stack antenna 1 of the first embodiment of the present invention is composed of a composite antenna including a first antenna in which the first and second stages, which are composed of two sets of dipole antennas, are stacked in two stages, and a second antenna in which the slot elements A-1 to A-4 are stacked in four stages. In this case, the first usable frequency band of the first antenna and the second usable frequency band of the second antenna are different, and the stack antenna 1 of the first embodiment of the present invention is a wideband antenna that operates in the first usable frequency band and the second usable frequency band. The slot elements A-1 and A-3, which are arranged close to each other so as to surround the two sets of dipole antennas, also function as parasitic elements of the first antenna. The slot elements A-1 to A-4 have the same configuration, and as an example, an expanded view of the slot element A-1 is shown in Fig. 4. As shown in Fig. 4, the slot element A-1 is composed of a bent portion Aa made of a metal plate having a horizontally long rectangular shape, a horizontally long narrow slot Ab is formed in the center of the bent portion Aa, and a feed point Ad is provided at a predetermined position of the slot Ab. The slot element A-1 is formed by bending the bent portion Aa into an arc shape with a radius of θ1. The width of the bent portion Aa in the slot elements A-1 to A-4 is SL1, the length in the vertical direction is W6, the width of the slot Ab is S1 and the length is S2, and the feed point Ad is provided at a distance S3 from the left end of the slot Ad.

[0015] A power feed point 15 is disposed at approximately the center between the first and second stages of the first antenna constituting the stack antenna 1 of the first embodiment, and a branch line 13 connected to the hot side of this power feed point 15 is formed on one surface of the substrate 10 so as to extend vertically approximately along the center line in the longitudinal direction. The tips of a pair of hot elements 11b-1 in the first stage, whose upper ends are bent in an L-shape so as to face each other, are connected to the branch line 13 extending downward from the power feed point 15, and the tips of a pair of hot elements 11b-2 in the second stage, whose upper ends are bent in an L-shape so as to face each other, are connected to the branch line 13 extending upward from the power feed point 15. In addition, a wide earth line 14 connected to the earth side of the power feed point 15 is formed wide on the other surface of the substrate 10 so as to extend vertically approximately along the center line in the longitudinal direction. The tips of a pair of ground elements 11a-1 in the first stage, whose lower ends are bent in an L shape so as to face each other, are connected to the ground line 14 extending downward from the feed point 15, and the tips of a pair of ground elements 11a-2 in the second stage, whose lower ends are bent in an L shape so as to face each other, are connected to the ground line 14 extending upward from the feed point 15. As a result, power is fed in parallel from the feed point 15 to the two pairs of dipole antennas in the first and second stages via the transmission line consisting of the branch line 13 and the ground line 14. The branch line 13 formed on one surface of the substrate 10 is formed on a wide earth line 14 formed on the other surface of the substrate 10, and the transmission line is a strip line. This strip line feeds power in parallel from a feed point 15 to two sets of dipole antennas in the first and second stages. The frequency of the signal transmitted and received at the feed point 15 is set to a frequency in the first usable frequency band. Moreover, the slot elements A-1 to A-4 stacked in four stages are fed in parallel from a feed point different from the feed point 15. The frequency of the signal transmitted and received at the different feed point is set to a frequency of the second usable frequency band.

[0016] In the stack antenna 1 of the first embodiment of the present invention thus configured, as shown in Fig. 1, the vertical length of the slot elements A-1 to A-4 is W1, and the installation interval of the slot elements A-1 to A-4 is L1. The outer diameter of the slot elements A-1 to A-4 is D1, and the horizontal width of the substrate 10 is W2. Furthermore, as shown in Fig. 3, the vertical length from the ends of the hot elements 11b-1 and 11b-2 to the ends of the earth elements 11a-1 and 11a-2 is L2, the installation interval between the hot elements 11b-1 and 11b-2 is L3, the line width of the hot elements 11b-1 and 11b-2 is W3, the outer width of the pair of hot elements 11b-1 and the pair of hot elements 11b-2 is D2, and the inner width is W4. Although not shown, the installation interval between the earth elements 11a-1 and 11a-2 is L3, the line width of the earth elements 11a-1 and 11a-2 is W3, the outer width of the pair of earth elements 11a-1 and the pair of earth elements 11a-2 is D2, and the inner width is W4. Furthermore, the width of the earth line 14 is W5. Thus, the installation interval between the two pairs of dipole antennas is L3.

[0017] The stack antenna 1 of the first embodiment of the present invention is configured as described above, and the first antenna, which is made up of two sets of dipole antennas stacked in two stages, is erected and placed on a vertical plane. The second antenna, which is made up of slot elements A-1 to A-4 stacked in four stages, is also erected and placed on a vertical plane. As a result, the stack antenna 1 of the first embodiment of the present invention operates as a vertically polarized antenna, which is a composite antenna made up of the first antenna made up of two sets of dipole antennas stacked in two stages and the second antenna, which is made up of slot elements A-1 to A-4 stacked in four stages.

[0018] Here, when the first usable frequency band of the first antenna in which two dipole antennas each consisting of a hot element 11b-1 and a ground element 11a-1 and two dipole antennas each consisting of a hot element 11b-2 and a ground element 11a-2 are stacked in two stages is f1 (2593MHz) to f2 (3500MHz), the element lengths of the two dipole antennas are derived using the center frequency (3046.5MHz) of the frequency f1 and the frequency f2. When the second usable frequency band of the second antenna in which the slot elements A-1 to A-4 are stacked in four stages is f3 (3850MHz) to f4 (4750MHz), the element lengths of the slot elements A-1 to A-4 are derived using the center frequency (4300MHz) of the frequency f3 and the frequency f4. The dimensions of the stack antenna 1 of the first embodiment are as follows: the installation interval L1 is about 44 mm, the length L2 is about 44 mm, the installation interval L3 is about 88 mm, the length W1 is about 24 mm, the width W2 is about 20 mm, the line width W3 is about 3 mm, the inner width W4 is about 12.5 mm, the outer diameter D1 is about 22 mm, and the outer width D1 is about 18.5 mm. The width SL1 is about 55 mm, the length W6 is about 24 mm, the width S1 is about 2 mm, the length S2 is about 34.9 mm, the distance S3 is about 9.6 mm, and the arc degree θ1 is about 300°. As a result, the stack antenna 1 of the first embodiment of the present invention operates well in the first usable frequency band of about 2593 MHz to about 3500 MHz and the second usable frequency band of about 3850 MHz to about 4750 MHz. Here, it is known that the side lobe becomes smaller when the ratio of element interval / wavelength can be reduced, and since the installation interval L1 of the slot elements A-1 to A-4 stacked in four stages is set to about 1 / 2 of the installation interval L3 of the two sets of dipole antennas stacked in two stages, it is possible to reduce the side lobe in the second operating frequency band. Also, the stack antenna 1 of the first embodiment is a composite antenna consisting of a first antenna in which two sets of dipole antennas are stacked in two stages, and a second antenna in which the slot elements A-1 to A-4 are stacked in four stages, and since the first antenna and the second antenna are arranged inside each other, it can be made compact.

[0019] <Stack antenna according to a second embodiment of the present invention> FIG. 5(a) shows a front view showing the configuration of a stack antenna 2 according to the second embodiment of the present invention, FIG. 5(b) shows a rear view thereof, FIG. 6 shows a bottom view thereof, and FIG. 7 shows a front view showing the configuration of the substrate in the stack antenna 2 according to the second embodiment. The stack antenna 2 of the second embodiment of the present invention shown in these figures is composed of a first antenna in which a first stage and a second stage each composed of a dipole antenna are stacked in two stages, and a second antenna in which slot elements A-1 to A-4 are stacked in four stages. The first stage of the first antenna is composed of two sets of dipole antennas composed of a pair of hot elements 21b-1 and a pair of earth elements 21a-1, and the second stage is composed of two sets of dipole antennas composed of a pair of hot elements 21b-2 and a pair of earth elements 21a-2. As shown in FIG. 7, the pair of hot elements 21b-1, the pair of hot elements 21b-2, the pair of earth elements 21a-1, and the pair of earth elements 21a-2 are formed on a substrate 20 such as a fluororesin substrate having good high-frequency characteristics. That is, on the lower part of one surface of the substrate 20 having a vertically elongated rectangular shape, a pair of hot elements 21b-1 constituting the first stage are formed in a vertically elongated rectangular shape facing each other along the longitudinal direction of both edges. Moreover, above the center of one surface of the substrate 20, a pair of hot elements 21b-2 constituting the second stage are formed in a vertically elongated rectangular shape facing each other along the longitudinal direction of both edges. Further, below the center of one surface of the substrate 10, a pair of earth elements 21a-1 constituting the first stage are formed in a vertically elongated rectangular shape facing each other along the longitudinal direction of both edges. Further, above the one surface of the substrate 20, a pair of earth elements 21a-2 constituting the second stage are formed in a vertically elongated rectangular shape facing each other along the longitudinal direction of both edges. In the first stage of the first antenna, a pair of hot elements 21b-1 and a pair of earth elements 21a-1 are formed facing each other vertically, so that two dipole antennas are formed. In the second stage of the first antenna, a pair of hot elements 21b-2 and a pair of earth elements 21a-2 are formed facing each other vertically, so that two dipole antennas are formed.

[0020] In the first stage of the first antenna, an arc-shaped slot element A-1 having a radian angle of θ1 is arranged adjacently to two dipole antennas each consisting of a pair of hot elements 21b-1 and a pair of earth elements 21a-1, and in the second stage, an arc-shaped slot element A-3 having a radian angle of θ1 is arranged adjacently to two dipole antennas each consisting of a pair of hot elements 21b-2 and a pair of earth elements 21a-2. In addition, between the first stage and the second stage, an arc-shaped slot element A-2 having a radian angle of θ1 is arranged adjacently to surround the substrate 20, and an arc-shaped slot element A-4 having a radian angle of θ1 is arranged adjacently to surround the upper end of the substrate 20. In this case, the slot elements A-1 to A-4 are arranged on a circle whose center is approximately the central axis of the substrate 20.

[0021] The slot elements A-1 to A-4 constitute a second antenna stacked in four stages. That is, the stack antenna 2 of the second embodiment is composed of a composite antenna including a first antenna in which the first and second stages, which are composed of two sets of dipole antennas, are stacked in two stages, and a second antenna in which the slot elements A-1 to A-4 are stacked in four stages. In this case, the first usable frequency band of the first antenna and the second usable frequency band of the second antenna are different, and the stack antenna 2 of the second embodiment of the present invention is a wideband antenna that operates in the first usable frequency band and the second usable frequency band. The slot elements A-1 and A-3, which are arranged close to each other so as to surround the two sets of dipole antennas, also function as parasitic elements of the first antenna. The slot elements A-1 to A-4 have the same configuration and are configured as described in the stack antenna 1 of the first embodiment, so the explanation will be omitted, but the dimensions of the slot elements A-1 to A-4 are also the same as described in the stack antenna 1 of the first embodiment.

[0022] In the stack antenna 2 of the second embodiment, a feed point 15 is disposed at approximately the center between the first and second stages of the first antenna, and a wide earth line 24 connected to the earth side of the feed point 15 is formed wide on one surface of the substrate 20 so as to extend vertically approximately along the center line in the longitudinal direction. The tips of a pair of earth elements 21a-1 in the first stage, whose lower ends are bent in an L-shape so as to face each other, are connected to the earth line 24 extending downward from the feed point 15, and the tips of a pair of earth elements 21a-2 in the second stage, whose lower ends are bent in an L-shape so as to face each other, are connected to the earth line 24 extending upward from the feed point 15. In addition, a branch line 23 connected to the hot side of the feed point 15 is formed on the other surface of the substrate 20 so as to extend vertically approximately along the center line in the longitudinal direction. The tip of the branch line 23 extending downward from the power feed point 15 is formed into a T-shape, and the tip is further bent downward, and both ends are connected to a pair of hot elements 21b-1 of the first stage via a pair of through holes 26a. The tip of the branch line 23 extending upward from the power feed point 15 is formed into a T-shape, and the tip is further bent downward, and both ends are connected to a pair of hot elements 21b-2 of the second stage via a pair of through holes 26b. As a result, power is fed in parallel from the power feed point 15 to the two dipole antennas of the first and second stages via the transmission line consisting of the branch line 23 and the earth line 24. The branch line 23 formed on the other surface of the substrate 20 is formed on a wide earth line 24 formed on one surface of the substrate 20, and the transmission line is a strip line. This strip line feeds power in parallel from the feed point 15 to the two sets of dipole antennas in the first and second stages. The frequency of the signal transmitted and received at the feed point 15 is set to a frequency in the first usable frequency band. Moreover, the slot elements A-1 to A-4 stacked in four stages are fed in parallel from a feed point different from the feed point 15. The frequency of the signal transmitted and received at the different feed point is set to a frequency of the second usable frequency band.

[0023] The stack antenna 2 of the second embodiment of the present invention configured in this manner has the same dimensions as the stack antenna 1 of the first embodiment. In this case, the hot elements 11b-1 and 11b-2 should be read as hot elements 21b-1 and 21b-2, and the earth elements 11a-1 and 11a-2 should be read as earth elements 21a-1 and 21a-2.

[0024] The stack antenna 2 of the second embodiment of the present invention is constructed as described above, and the first antenna, which is made up of two sets of dipole antennas stacked in two stages, and the second antenna, which is made up of slot elements A-1 to A-4 stacked in four stages, are erected and placed on a vertical plane. As a result, the stack antenna 2 of the second embodiment of the present invention operates as a vertically polarized antenna, which is a composite antenna made up of two sets of dipole antennas stacked in two stages and the second antenna, which is made up of slot elements A-1 to A-4 stacked in four stages.

[0025] Here, when the first usable frequency band of the first antenna in which two dipole antennas consisting of hot element 21b-1 and earth element 21a-1 and two dipole antennas consisting of hot element 21b-2 and earth element 21a-2 are stacked in two stages is f1 (2593MHz) to f2 (3500MHz), the element lengths of the two dipole antennas are derived using the center frequency (3046.5MHz) of frequency f1 and frequency f2. When the second usable frequency band of the second antenna in which slot elements A-1 to A-4 are stacked in four stages is f3 (3850MHz) to f4 (4750MHz), the element lengths of the slot elements are derived using the center frequency (4300MHz) of frequency f3 and frequency f4. Since the dimensions of the stack antenna 2 of the second embodiment are similar to the dimensions of the stack antenna 1 of the first embodiment, their explanation will be omitted, but this enables the stack antenna 2 of the second embodiment of the present invention to operate well in the first usable frequency band of approximately 2593 MHz to approximately 3500 MHz and the second usable frequency band of approximately 3850 MHz to approximately 4750 MHz. Here, it is known that the side lobe becomes smaller when the ratio of element interval / wavelength can be reduced, and since the installation interval L1 of the slot elements A-1 to A-4 stacked in four stages is set to about 1 / 2 of the installation interval L3 of the two sets of dipole antennas, it is possible to reduce the side lobe in the second operating frequency band. Also, the stack antenna 2 of the second embodiment is a composite antenna consisting of a first antenna in which two sets of dipole antennas are stacked in two stages, and a second antenna in which the slot elements A-1 to A-4 are stacked in four stages, and since the first antenna and the second antenna are arranged inside each other, it can be made compact.

[0026] <Multiple configurations of slot elements> A number of configurations of slot elements that can be used in the stack antenna according to the embodiment of the present invention are shown in perspective views in FIGS. 8(a) to (f). The slot element A shown in Fig. 8(a) is the slot element A-1 to slot element A-4 used in the stack antennas 1 and 2 of the first and second embodiments. The slot element A is configured by bending the bending portion Aa into an arc shape, and a gap portion Ac of a predetermined width is formed. A horizontally long narrow slot Ab is formed in the approximate center, and a feed point Ad is provided at a predetermined position of the slot Ab. 8(b), the slot element B is configured such that the bent portion Ba1 and the bent portion Ba2, which are bent in a semicircular shape and facing each other, are arranged on a circle approximately centered on the central axis of the substrate 20, and the gaps Bc1 and Bc2 are formed between the opposing edges of the bent portion Ba1 and the bent portion Ba2. The bent portion Ba1 and the bent portion Ba2 are respectively formed in the approximate center thereof with the horizontally long narrow slots Bb1 and Bb2, and the slots Bb1 and Bb2 are respectively provided at predetermined positions thereof with the power feed points Bd1 and Bd2.

[0027] The slot element C shown in Fig. 8(c) is a non-power-fed slot element. The slot element C is configured by bending the bending portion Ca into an arc shape, and a gap portion Cc of a certain width is formed. A horizontally long narrow slot Ab is formed in the approximate center, but no power feed point is provided. The slot element D shown in Fig. 8(d) is a non-power-fed slot element, and is configured by bending the bent portion Da1 and the bent portion Da2 in a semicircular shape so that they face each other and are arranged so as to be positioned on a circle. A gap portion Dc1 and a gap portion Dc2 are formed between the opposing edges of the bent portion Da1 and the bent portion Da2. A horizontally long narrow slot Db1 and a slot Db2 are formed in the approximate center of the bent portion Da1 and the bent portion Da2, respectively, but no power feed point is provided. A slot element E shown in FIG. 8(e) is a parasitic slot element, and is composed of a cylindrical portion Ea formed in a cylindrical shape. The slot element F shown in Fig. 8(f) is a non-powered slot element, and is configured such that the bent portion Fa1 and the bent portion Fa2 are bent in a semicircular shape and arranged so as to face each other on a circle. A gap portion Fc1 and a gap portion Fc2 are formed between the opposing edges of the bent portion Fa1 and the bent portion Fa2. The use of slot elements A to F shown in Figs. 8(a) to (f) will be described later.

[0028] <Stack antenna according to the third embodiment of the present invention> Next, the configuration of a stack antenna 3 according to a third embodiment of the present invention is shown in FIG. 9, the stack antenna 3 of the third embodiment of the present invention is a composite antenna including a first antenna in which two sets of dipole antennas, each consisting of a pair of hot elements and a pair of earth elements, are stacked in eight stages, and a second antenna in which slot elements are stacked in 16 stages. The two sets of dipole antennas have the same configuration as the two sets of dipole antennas constituting the first and second stages in the stack antenna 1 of the first embodiment. That is, the first stage is composed of two dipole antennas each consisting of a pair of hot elements 11b-1 and a pair of earth elements 11a-1, the second stage is composed of two dipole antennas each consisting of a pair of hot elements 11b-2 and a pair of earth elements 11a-2, the third stage is composed of two dipole antennas each consisting of a pair of hot elements 11b-3 and a pair of earth elements 11a-3, the fourth stage is composed of two dipole antennas each consisting of a pair of hot elements 11b-4 and a pair of earth elements 11a-4, the fifth stage is composed of two dipole antennas each consisting of a pair of hot elements 11b-5 and a pair of earth elements 11a-5, and the sixth stage is composed of two dipole antennas each consisting of a pair of hot elements 11b-6 and a pair of earth elements 11a-6. Furthermore, the seventh stage consists of two pairs of dipole antennas each consisting of a pair of hot elements 11b-7 and a pair of earth elements 11a-7, and the eighth stage consists of two pairs of dipole antennas each consisting of a pair of hot elements 11b-8 and a pair of earth elements 11a-8.

[0029] The pair of hot elements 11b-1, 11b-2, hot elements 11b-3, 11b-4, hot elements 11b-5, 11b-6, and hot elements 11b-7, 11b-8 are formed on one surface of a long and narrow rectangular substrate 30 such as a fluororesin substrate having good high frequency characteristics with the same configuration and dimensions as the pair of hot elements 11b-1, 11b-2 in the stack antenna 1 of the first embodiment. The pair of earth elements 11a-1, 11a-2, earth elements 11a-3, 11a-4, earth elements 11a-5, 11a-6, and earth elements 11a-7, 11a-8 are formed on the other surface of a long and narrow rectangular substrate 30 such as a fluororesin substrate having good high frequency characteristics with the same configuration and dimensions as the pair of earth elements 11a-1, 11a-2 in the stack antenna 1 of the first embodiment. Therefore, detailed description of these elements will be omitted.

[0030] The slot elements A-1 to A-16 stacked in 16 stages in the stack antenna 3 of the third embodiment of the present invention have the same configuration as the slot elements A-1 to A-4 in the stack antenna 1 of the first embodiment, so their description is omitted. However, slot element A-1 is arranged in close proximity to surround the two sets of dipole antennas in the first row, slot element A-3 is arranged in close proximity to surround the two sets of dipole antennas in the second row, slot element A-5 is arranged in close proximity to surround the two sets of dipole antennas in the third row, slot element A-7 is arranged in close proximity to surround the two sets of dipole antennas in the fourth row, slot element A-9 is arranged in close proximity to surround the two sets of dipole antennas in the fifth row, slot element A-11 is arranged in close proximity to surround the two sets of dipole antennas in the sixth row, slot element A-13 is arranged in close proximity to surround the two sets of dipole antennas in the seventh row, and slot element A-15 is arranged in close proximity to surround the two sets of dipole antennas in the eighth row. In addition, the slot element A-2 is arranged between the first and second stages so as to surround the substrate 30, the slot element A-4 is arranged between the second and third stages so as to surround the substrate 30, the slot element A-6 is arranged between the third and fourth stages so as to surround the substrate 30, the slot element A-8 is arranged between the fourth and fifth stages so as to surround the substrate 30, the slot element A-10 is arranged between the fifth and sixth stages so as to surround the substrate 30, the slot element A-12 is arranged between the sixth and seventh stages so as to surround the substrate 30, the slot element A-14 is arranged between the seventh and eighth stages so as to surround the substrate 30, and the slot element A-16 is arranged to surround the upper end of the substrate 30. In this case, the slot elements A-1 to A-16 are arranged on a circle approximately centered on the central axis of the substrate 30.

[0031] The slot elements A-1 to A-16 stacked in 16 stages constitute the second antenna. That is, the stack antenna 3 of the third embodiment of the present invention is composed of a composite antenna consisting of a first antenna in which two sets of dipole antennas are stacked in 8 stages, and a second antenna in which the slot elements A-1 to A-16 are stacked in 16 stages. In this case, the first usable frequency band of the first antenna is different from the second usable frequency band of the second antenna, and the stack antenna 3 of the third embodiment of the present invention is a wideband antenna that operates in the first usable frequency band and the second usable frequency band. The slot elements A-1, A-3, A-5, a-7, A-9, A-11, A-13, and A-15 arranged close to the two sets of dipole antennas so as to surround them also function as parasitic elements of the first antenna. Although the slot elements A-1 to A-16 are slot elements A shown in FIG. 8(a), they may be slot elements B shown in FIG. 8(b).

[0032] In the stack antenna 3 of the third embodiment, the first antenna, which is made of two sets of dipole antennas stacked in eight stages, is fed with power from the feed point 35. That is, the first antenna is branched into two from the feed point 35, and each branch is further branched into two, resulting in a total of four branches. Each of the four branches feeds two sets of dipole antennas in the first and second stages, two sets of dipole antennas in the third and fourth stages, two sets of dipole antennas in the fifth and sixth stages, and two sets of dipole antennas in the seventh and eighth stages. In this way, in the first antenna, which is made of two sets of dipole antennas stacked in eight stages, power is distributed from the feed point 35 to the two sets of dipole antennas in the first to eighth stages and fed in parallel, so that when the first antenna, which is made of two sets of dipole antennas stacked in eight stages, is erected and placed in a vertical plane, a sharp radiation pattern can be obtained in the vertical plane. In addition, the first antenna, which is made of two sets of dipole antennas stacked in eight stages, operates in a wide band. The first operating frequency band of the two dipole antennas, each consisting of a pair of hot elements and a pair of earth elements stacked in eight stages, is f1 (2593 MHz) to f2 (3500 MHz), and the element length is derived using the center frequency (3046.5 MHz) between the frequencies f1 and f2. The frequencies of signals transmitted and received at the feeding point 35 are f1 and f2, or the frequencies of the first operating frequency band.

[0033] In the stack antenna 3 of the third embodiment, the second antenna in which the slot elements are stacked in 16 stages is fed from the feed point 36. That is, the second antenna is branched into two from the feed point 36, each of which is further branched into two to form four branches, each of which is further branched into two to form eight branches, and each of which is further branched into two to form 16 branches. Each of the 16 branches feeds the slot elements A-1 to A-16 which are stacked in 16 stages. In this way, in the second antenna in which the slot elements are stacked in 16 stages, the slot elements A-1 to A-16 are power-distributed from the feed point 36 and fed in parallel, and when the second antenna in which the slot elements are stacked in 16 stages is erected and placed in a vertical plane, a sharp radiation pattern can be obtained in the vertical plane. In addition, the second antenna in which the slot elements are stacked in 16 stages operates in a wide band. The second operating frequency band of the 16-stacked slot elements is f3 (3850 MHz) to f4 (4750 MHz), and the element length is derived using the center frequency (4300 MHz) between frequencies f3 and f4. The frequency of the signal transmitted and received at the feeding point 36 is f3 or f4, or a frequency in the second operating frequency band. From the above, the stack antenna 3 of the third embodiment of the present invention is a composite antenna comprising a first antenna in which two dipole antennas, each consisting of a pair of hot elements and a pair of earth elements, are stacked in eight stages, and a second antenna in which slot elements A-1 to A-16 are stacked in 16 stages, and is a wideband antenna that operates in the first and second usable frequency bands. Here, it is known that the side lobe becomes smaller when the ratio of element interval / wavelength can be reduced, and since the installation interval of the slot elements A-1 to A-16 stacked in 16 stages is about 1 / 2 of the installation interval of the first antenna consisting of 8 stages of two sets of dipole antennas, it is possible to reduce the side lobe in the second operating frequency band. Also, the stack antenna 3 of the third embodiment is a composite antenna consisting of the first antenna consisting of 2 sets of dipole antennas stacked in 8 stages and the second antenna consisting of the slot elements A-1 to A-16 stacked in 16 stages, and since the first antenna and the second antenna are arranged inside each other, it can be made compact.

[0034] <Antenna characteristics of the stack antenna according to the third embodiment of the present invention> The antenna characteristics of the stack antenna 3 of the third embodiment of the present invention will be described. In the stack antenna 3 of the third embodiment of the present invention having the configuration shown in Fig. 9, the first usable frequency band of the first antenna in which two sets of dipole antennas, each consisting of a pair of hot elements and a pair of earth elements, are stacked in eight stages is f1 (2593MHz) to f2 (3500MHz) as described above, and the element length is derived using the center frequency (3046.5MHz) of the frequencies f1 and f2. The second usable frequency band of the second antenna in which 16 stages of slot elements are stacked is f3 (3850MHz) to f4 (4750MHz) as described above, and the element length is derived using the center frequency (4300MHz) of the frequencies f3 and f4. The installation interval between two dipole antennas, each consisting of a pair of hot elements and a pair of earth elements, stacked in eight stages, is designated as L3, and L3 is approximately 88 mm. The arrangement interval between slot elements A-1 to A-16, which are stacked in 16 stages, is designated as L1, and L1 is approximately 44 mm. Diagrams of the directional characteristics of stack antenna 3 of the third embodiment with these dimensions are shown in Figures 10(a) to (d).

[0035] FIG. 10(a) shows the directional characteristics at a frequency of 2593 MHz, and FIG. 10(b) shows the directional characteristics at a frequency of 3500 MHz. In this case, the installation interval L3 (about 88 mm) of two dipole antennas consisting of a pair of hot elements and a pair of earth elements stacked in eight stages is about 0.761 λ1 when the free space wavelength of f1 (2593 MHz) is λ1, and about 1.027 λ2 when the free space wavelength of f2 (3500 MHz) is λ2. The half-value angle at f1 (2593 MHz) is about 9 deg, the gain is +12.6 dBi, and the side lobe is -13.4 dB. The half-value angle at f2 (3500 MHz) is 6 deg, the gain is +13.9 dBi, and the side lobe is -13.1 dB. FIG. 10(c) is a diagram showing the directional characteristics at a frequency of f3 (3850 MHz), and FIG. 10(d) is a diagram showing the directional characteristics at a frequency of f4 (4750 MHz). In this case, the installation interval L1 (about 44 mm) of the slot elements stacked in 16 stages is about 0.565λ3 when the free space wavelength of f3 (3850 MHz) is λ3, and about 0.697λ4 when the free space wavelength of f4 (4750 MHz) is λ4. The half-value angle at f3 (3850 MHz) is 5.5 deg, the gain is +14.3 dBi, and the side lobe is -13.4 dB. The half-value angle at f4 (4750 MHz) is 4.5 deg, the gain is +15.3 dBi, and the side lobe is -13.5 dB.

[0036] 10(a)-(d), in the stack antenna 3 of the third embodiment of the present invention, the installation interval L3 (about 88 mm) is about 0.761 λ1 at f1 (2593 MHz), and the installation interval L3 (about 88 mm) is about 1.027 λ2 at f2 (3500 MHz), satisfying a half-value angle of 10 deg or less and a side lobe of -12 dB or less. Also, the installation interval L1 (about 44 mm) is about 0.565 λ3 at f3 (3850 MHz), and the installation interval L1 (about 44 mm) is about 0.697 λ4 at f4 (4750 MHz), satisfying a half-value angle of 10 deg or less and a side lobe of -12 dB or less.

[0037] Here, it will be explained that the conventional wideband antenna 100 shown in FIG. 19 does not satisfy the half-power angle of 10 deg or less and the side lobe of -12 dB or less in the first and second usable frequency bands described above. In comparing the stack antenna 3 of the third embodiment of the present invention with the conventional wideband antenna 100, since the eight-stage stacked parasitic elements C-103 to C-108 in the conventional wideband antenna 100 are not fed, the comparison will be made by replacing C-103 to C-108 with feeding elements C-103 to C-108 that feed power. That is, in the conventional wideband antenna 100, the installation interval between two dipole antennas, each consisting of a pair of hot elements and a pair of earth elements, stacked in eight stages, is designated as L103, and L103 is approximately 88 mm. Also, the installation interval between the eight-stage stacked feed elements C-103 to C-108 is designated as L101, and L101 is approximately 88 mm. Diagrams of the directional characteristics of the conventional wideband antenna 100 with these dimensions are shown in Figures 21(a) to (d).

[0038] FIG. 21(a) is a diagram showing the directional characteristics at a frequency of f1 (2593 MHz), and FIG. 21(b) is a diagram showing the directional characteristics at a frequency of f2 (3500 MHz). In this case, the installation interval L103 (about 88 mm) of the two dipole antennas stacked in eight stages is about 0.761 λ1 when the free space wavelength of f1 (2593 MHz) is λ1, and about 1.027 λ2 when the free space wavelength of f2 (3500 MHz) is λ2. And, the half-value angle at f1 (2593 MHz) is about 9 deg, the gain is +12.6 dBi, and the side lobe is -13.4 dB. And, the half-value angle at f2 (3500 MHz) is 6 deg, the gain is +13.9 dBi, and the side lobe is -13.1 dB. FIG. 21(c) is a diagram showing the directional characteristics at a frequency of f3 (3850 MHz), and FIG. 21(d) is a diagram showing the directional characteristics at a frequency of f4 (4750 MHz). In this case, the installation interval L101 (about 88 mm) of the eight-stage stacked feed elements C-103 to C-108 is about 1.129λ3 when the free space wavelength of f3 (3850 MHz) is λ3, and about 1.393λ4 when the free space wavelength of f4 (4750 MHz) is λ4. And, the half-value angle at f3 (3850 MHz) is 5 deg, the gain is +14.3 dBi, and the side lobe is -11.9 dB. And, the half-value angle at f4 (4750 MHz) is 4 deg, the gain is +14.7 dBi, and the side lobe is -5.9 dB.

[0039] In the conventional wideband antenna 100, the installation interval L103 of two dipole antennas, each consisting of a pair of hot elements and a pair of earth elements, stacked in eight stages, is changed from about 88 mm to about 44 mm, and the arrangement interval L101 of the eight-stage stacked feed elements C-103 to C-108 is changed from about 88 mm to about 44 mm. The directional characteristics of the conventional wideband antenna 100 with these dimensions are shown in Figures 22(a) to (d). FIG. 22(a) is a diagram showing the directional characteristics at a frequency of f1 (2593 MHz), and FIG. 22(b) is a diagram showing the directional characteristics at a frequency of f2 (3500 MHz). In this case, the installation interval L103 (about 44 mm) of the two dipole antennas stacked in eight stages is about 0.380λ1 when the free space wavelength of f1 (2593 MHz) is λ1, and about 0.513λ2 when the free space wavelength of f2 (3500 MHz) is λ2. The half-value angle at f1 (2593 MHz) is about 15 deg, the gain is +9.7 dBi, and the side lobe is -14.8 dB. The half-value angle at f2 (3500 MHz) is 13 deg, the gain is +11.0 dBi, and the side lobe is -13.9 dB. FIG. 22(c) is a diagram showing the directional characteristics at a frequency of f3 (3850 MHz), and FIG. 22(d) is a diagram showing the directional characteristics at a frequency of f4 (4750 MHz). In this case, the installation interval L101 (about 44 mm) of the eight-stage stacked feed elements C-103 to C-108 is about 0.565 λ3 when the free space wavelength of f3 (3850 MHz) is λ3, and about 0.697 λ4 when the free space wavelength of f4 (4750 MHz) is λ4. And, the half-value angle at f3 (3850 MHz) is 12 deg, the gain is +11.4 dBi, and the side lobe is -13.7 dB. And, the half-value angle at f4 (4750 MHz) is 10 deg, the gain is +12.2 dBi, and the side lobe is -13.4 dB.

[0040] 21(a) to (d) described above, in conventional wideband antenna 100, if the installation interval L103 of two sets of dipole antennas stacked in eight stages and the installation interval L101 of the eight-stage stacked feed elements C-103 to C-108 are approximately 88 mm, then in conventional wideband antenna 100 with these dimensions, the installation interval L103 (approximately 88 mm) at f1 (2593 MHz) is approximately 0.761 λ1, and the installation interval L103 (approximately 88 mm) at f2 (3500 MHz) is approximately 1.027 λ2, satisfying a half-value angle of 10 deg or less and a side lobe of -12 dB or less. In addition, at f3 (3850 MHz), the installation interval L101 (approximately 88 mm) is approximately 1.129λ3, and at f4 (4750 MHz), the installation interval L101 (approximately 88 mm) is approximately 1.393λ4, which satisfies the half-value angle of 10 deg or less, but does not satisfy the side lobe of -12 dB or less. Furthermore, referring to Figures 22(a) to (d) described above, in conventional wideband antenna 100, if the installation interval L103 of two sets of dipole antennas stacked in eight stages and the installation interval L101 of feed elements C-103 to C-108 stacked in eight stages are approximately 44 mm, in conventional wideband antenna 100 with these dimensions, the installation interval L103 (approximately 44 mm) at f1 (2593 MHz) is approximately 0.380λ1, and the installation interval L103 (approximately 44 mm) at f2 (3500 MHz) is approximately 0.513λ2, which satisfies the side lobe of -12 dB or less, but does not satisfy the half-value angle of 10 deg or less. Furthermore, at f3 (3850 MHz), the installation interval L101 (approximately 44 mm) is approximately 0.565λ3, which satisfies the side lobe requirement of -12 dB or less, but does not satisfy the half-value angle requirement of 10 deg or less. Thus, it can be seen that the conventional wideband antenna 100 cannot satisfy a half-power angle of 10 deg or less and a side lobe of -12 dB or less at f1, f2, f3, and f4, whether the installation interval is 88 mm or 44 mm.

[0041] In the stack antenna 3 of the third embodiment of the present invention, the installation interval between two dipole antennas consisting of a pair of hot elements and a pair of earth elements stacked in 8 stages is L3, and the installation interval between slot elements A-1 to A-16 stacked in 16 stages is L1.In this case, since the installation interval L1 is 1 / 2 of the installation interval L3, it is possible to configure an antenna that satisfies a half-value angle of 10 deg or less and a side lobe of -12 dB or less at the frequencies f1 (2593 MHz), f2 (3500 MHz), f3 (3850 MHz), and f4 (4750 MHz). In addition, in the stack antenna 3 of the third embodiment of the present invention, power is supplied with a phase difference to each of the two sets of dipole antennas stacked in eight stages, and power is supplied with a phase difference to each of the slot elements A-1 to A-4 stacked in 16 stages, thereby providing a downward tilt directivity. Figures 11(a) to (d) show the directional characteristics of the stack antenna 3 of the third embodiment when power is supplied to each of two dipole antennas consisting of a pair of hot elements and a pair of earth elements stacked in 8 stages, and to each of slot elements A-1 to A-16 stacked in 16 stages with a phase difference that results in a downward tilt angle of approximately 5 degrees.

[0042] FIG. 11(a) shows the directional characteristics at a frequency of f1 (2593 MHz), FIG. 11(b) shows the directional characteristics at a frequency of f2 (3500 MHz), FIG. 11(c) shows the directional characteristics at a frequency of f3 (3850 MHz), and FIG. 11(d) shows the directional characteristics at a frequency of f4 (4750 MHz). All the directional characteristics are the directional characteristics when power is fed with a phase difference that results in a downward tilt angle of about 5 deg. In this case, the installation interval of two dipole antennas consisting of a pair of hot elements and a pair of earth elements stacked in 8 stages is L3 (about 88 mm), and the installation interval of the slot elements A-1 to A-16 stacked in 16 stages is L1 (about 44 mm). Referring to FIG. 11(a), the half-value angle at f1 (2593 MHz) is about 10 deg, the gain is +12.6 dBi, and the side lobe is -13.0 dB. Referring to FIG. 11(b), the half-value angle at f2 (3500 MHz) is 8 deg, the gain is +13.8 dBi, and the side lobe is -11.7 dB. Referring to FIG. 11(c), the half-value angle at f3 (3850 MHz) is 7 deg, the gain is +14.4 dBi, and the side lobe is -13.1 dB. Referring to FIG. 11(d), the half-value angle at f4 (4750 MHz) is 7 deg, the gain is +15.3 dBi, and the side lobe is -13.3 dB. 11(a) to (d), in the stack antenna 3 of the third embodiment of the present invention, even when power is fed with a phase difference that results in a downward tilt angle of approximately 5 deg, the half-value angle is approximately 10 deg or less and the side lobe is approximately -12 dB or less, almost satisfying the requirements.

[0043] <Relationship between antenna installation interval and antenna characteristics> Graphs showing the relationship between antenna installation intervals and antenna characteristics when the number of stacked antenna elements is 4, 8, and 16 are shown in Figures 12 and 13. Figure 12 is a graph showing the relationship between the half-power angle and the antenna installation interval, and Figure 13 is a graph showing the relationship between the side lobe level and the antenna installation interval. 12, to keep the half-power angle at 10 deg or less, when the number of elements in the stacked antenna is 4, the installation interval must be about 1.13 λ or more, when the number of elements in the stacked antenna is 8, the installation interval must be about 0.7 λ or more, and when the number of elements in the stacked antenna is 16, an installation interval of about 0.4 λ is sufficient, where λ is the free space wavelength of the frequency used. Also, referring to FIG. 13, the side lobe levels have the same characteristics when the number of stacked antenna elements is 4, 8, or 16, and in order to keep the side lobe level at -12 dB or less, the antenna installation spacing should be approximately 1.12 λ or less.

[0044] <Stack antenna according to the fourth embodiment of the present invention> Next, three configurations of the stack antenna 4 according to the fourth embodiment of the present invention are shown in Fig. 14(a), (b), and (c). Fig. 14(a) is a front view showing the configuration of the stack antenna 4-1 according to the fourth embodiment of the first configuration, Fig. 14(b) is a front view showing the configuration of the stack antenna 4-2 according to the fourth embodiment of the second configuration, and Fig. 14(c) is a front view showing the configuration of the stack antenna 4-3 according to the fourth embodiment of the third configuration. The stack antenna 4-1 of the fourth embodiment of the first configuration shown in FIG. 14(a) is a composite antenna including a first antenna in which two sets of dipole antennas, each consisting of a pair of hot elements and a pair of earth elements formed on one surface of the substrate 30, are stacked in eight stages, and a second antenna in which slot elements A-1 to A-8 are stacked in eight stages. The configuration of the first antenna in which two sets of dipole antennas are stacked in eight stages is the same as the configuration of the first antenna in the stack antenna 3 of the third embodiment, but non-powered slot elements C-9 to C-12 are arranged adjacent to each other so as to surround the two sets of dipole antennas in the fifth to eighth stages. The configuration of the second antenna in which slot elements are stacked in eight stages is the same as the configuration in which slot elements A-1 to A-8 are stacked in eight stages in the second antenna in the stack antenna 3 of the third embodiment. The second antenna in which slot elements are stacked in eight stages is arranged at the bottom of the substrate 30. In this case, the slot elements C-9 to C-12 are arranged on a circle that is approximately centered on the central axis of the substrate 30.

[0045] The first usable frequency band of the two dipole antennas, each consisting of a pair of hot elements and a pair of earth elements stacked in eight stages, is f1 (2593 MHz) to f2 (3500 MHz), and the element length is derived using the center frequency (3046.5 MHz) of frequencies f1 and f2. In the first antenna, in which two dipole antennas are stacked in eight stages, power is fed from a feed point of the frequency of the first usable frequency band to each of the two dipole antennas in a tournament manner similar to the power feeding shown in Fig. 9. The second usable frequency band of the second antenna in which the slot elements A-1 to A-8 are stacked in eight stages is f3 (3850 MHz) to f4 (4750 MHz), and the element length is derived using the center frequency (4300 MHz) between the frequencies f3 and f4. In the second antenna in which the slot elements A-1 to A-8 are stacked in eight stages, power is fed from a feeding point of the frequency of the second usable frequency band to the slot elements A-1 to A-8 in the eight stages in a tournament manner similar to the feeding shown in FIG.

[0046] In the second antenna, slot elements C-9 to C-12 arranged closely so as to surround two sets of dipole antennas in the fifth to eighth stages of the first antenna are non-powered slot elements, and therefore slot elements C-9 to C-12 are either slot elements C to F shown in Fig. 8(c) to (f). Also, eight-stage stacked slot elements A-1 to A-8 are either slot elements A or slot elements B shown in Fig. 8(a) and (b). The installation spacing between the dipole antennas in two sets of dipole antennas, each consisting of a pair of hot elements and a pair of earth elements stacked in eight stages, is L3, and the installation spacing between the slot elements in the eight-stacked slot elements A-1 to A-8 is L1, with the installation spacing L1 being 1 / 2 of the installation spacing L3. The stack antenna 4-1 of the first configuration of the fourth embodiment of the present invention is configured as described above, and is a wideband antenna that operates in the first and second operating frequency bands, and since the installation interval L1 is 1 / 2 of the installation interval L3, it is possible to reduce the side lobe in the second operating frequency band. Also, the stack antenna 4-1 of the fourth embodiment of the first configuration is a composite antenna of a first antenna in which two sets of dipole antennas are stacked in eight stages, and a second antenna in which slot elements A-1 to A-8 are stacked in eight stages, and since the first antenna and the second antenna are arranged inside each other, it can be made compact.

[0047] The stack antenna 4-2 of the fourth embodiment having the second configuration shown in FIG. 14(b) is a composite antenna including a first antenna in which two sets of dipole antennas, each consisting of a pair of hot elements and a pair of earth elements formed on one surface of the substrate 30, are stacked in eight stages, and a second antenna in which slot elements A-3 to A-10 are stacked in eight stages. The configuration of the first antenna in which two sets of dipole antennas are stacked in eight stages is the same as the configuration of the first antenna in the stack antenna 3 of the third embodiment, but non-powered slot elements C-1, C-2 and slot elements C-11, C-12 are arranged adjacent to each other so as to surround the two sets of dipole antennas in the first and second stages and the seventh and eighth stages. The configuration of the second antenna in which slot elements are stacked in eight stages is the same as the configuration in which slot elements A-1 to A-8 are stacked in eight stages in the second antenna in the stack antenna 3 of the third embodiment. The second antenna in which slot elements are stacked in eight stages is arranged in the center of the substrate 30.

[0048] The first usable frequency band of the two dipole antennas, each consisting of a pair of hot elements and a pair of earth elements stacked in eight stages, is f1 (2593 MHz) to f2 (3500 MHz), and the element length is derived using the center frequency (3046.5 MHz) of frequencies f1 and f2. In the first antenna, in which two dipole antennas are stacked in eight stages, power is fed from a feed point of the frequency of the first usable frequency band to each of the two dipole antennas in a tournament manner similar to the power feeding shown in Fig. 9. The second usable frequency band of the second antenna in which the slot elements A-3 to A-10 are stacked in eight stages is f3 (3850 MHz) to f4 (4750 MHz), and the element length is derived using the center frequency (4300 MHz) between the frequencies f3 and f4. In the second antenna in which the slot elements A-3 to A-10 are stacked in eight stages, power is fed from a feeding point of the frequency of the second usable frequency band to the slot elements A-3 to A-10 in the eight stages in a tournament manner similar to the feeding shown in FIG.

[0049] In the second antenna, slot elements C-1, C-2 and slot elements C-11, C-12 arranged closely so as to surround two sets of dipole antennas in the first and second stages and the seventh and eighth stages of the first antenna are non-powered slot elements, so that slot elements C-1, C-2 and slot elements C-11, C-12 are either slot elements C to F shown in Figures 8(c) to (f). In addition, eight-stage stacked slot elements A-3 to A-10 are either slot elements A or slot elements B shown in Figures 8(a) and (b). The installation spacing between the dipole antennas in two sets of dipole antennas, each consisting of a pair of hot elements and a pair of earth elements stacked in eight stages, is L3, and the installation spacing between the slot elements A-3 to A-10, each consisting of eight stages stacked, is L1, and the installation spacing L1 is 1 / 2 of the installation spacing L3. The stack antenna 4-2 of the second configuration of the fourth embodiment of the present invention is configured as described above, and is a wideband antenna that operates in the first and second operating frequency bands, and since the installation interval L1 is 1 / 2 of the installation interval L3, it is possible to reduce the side lobe in the second operating frequency band. Also, the stack antenna 4-2 of the fourth embodiment of the second configuration is a composite antenna of a first antenna in which two sets of dipole antennas are stacked in eight stages, and a second antenna in which slot elements A-3 to A-10 are stacked in eight stages, and since the first antenna and the second antenna are arranged inside each other, it can be made compact.

[0050] The stack antenna 4-3 of the fourth embodiment of the third configuration shown in FIG. 14(c) is a composite antenna including a first antenna in which two sets of dipole antennas, each consisting of a pair of hot elements and a pair of earth elements formed on one surface of the substrate 30, are stacked in eight stages, and a second antenna in which slot elements A-5 to A-12 are stacked in eight stages. The first antenna in which two sets of dipole antennas are stacked in eight stages is the same as the first antenna in the stack antenna 3 of the third embodiment, but non-powered slot elements C-1 to C-4 are arranged adjacent to each other so as to surround the two sets of dipole antennas in the first to fourth stages. The second antenna in which slot elements are stacked in eight stages is the same as the second antenna in the stack antenna 3 of the third embodiment in which slot elements A-1 to A-8 are stacked in eight stages. The second antenna in which slot elements are stacked in eight stages is arranged on the upper part of the substrate 30.

[0051] The first usable frequency band of the two dipole antennas, each consisting of a pair of hot elements and a pair of earth elements stacked in eight stages, is f1 (2593 MHz) to f2 (3500 MHz), and the element length is derived using the center frequency (3046.5 MHz) of frequencies f1 and f2. In the first antenna, in which two dipole antennas are stacked in eight stages, power is fed from a feed point of the frequency of the first usable frequency band to each of the two dipole antennas in a tournament manner similar to the power feeding shown in Fig. 9. The second usable frequency band of the second antenna in which slot elements A-5 to A-12 are stacked in eight stages is f3 (3850 MHz) to f4 (4750 MHz), and the element length is derived using the center frequency (4300 MHz) between frequencies f3 and f4. In the second antenna in which slot elements A-3 to A-10 are stacked in eight stages, power is fed from a feeding point of the frequency of the second usable frequency band to the slot elements A-5 to A-12 in the eight stages in a tournament manner similar to the feeding shown in FIG.

[0052] In the second antenna, slot elements C-1 to C-4 arranged closely so as to surround two sets of dipole antennas in the first to fourth stages of the first antenna are non-powered slot elements, and therefore slot elements C-1 to C-4 are either slot elements C to F shown in Figures 8(c) to (f). Also, eight-stage stacked slot elements A-5 to A-12 are either slot elements A or slot elements B shown in Figures 8(a) and (b). The installation spacing between the dipole antennas in two sets of dipole antennas, each consisting of a pair of hot elements and a pair of earth elements stacked in eight stages, is L3, and the installation spacing between the slot elements A-3 to A-10, each consisting of eight stages stacked, is L1, and the installation spacing L1 is 1 / 2 of the installation spacing L3. The stack antenna 4-3 of the third configuration of the fourth embodiment of the present invention is configured as described above, and is a wideband antenna that operates in the first and second operating frequency bands, and since the installation interval L1 is half the installation interval L3, it is possible to reduce the side lobe in the second operating frequency band. Also, the stack antenna 4-2 of the fourth embodiment of the third configuration is a composite antenna of a first antenna in which two sets of dipole antennas are stacked in eight stages, and a second antenna in which slot elements A-5 to A-12 are stacked in eight stages, and since the first antenna and the second antenna are arranged inside each other, it can be made compact.

[0053] <Stack antenna according to the fifth embodiment of the present invention> FIG. 15(a) shows a left side view of the configuration of a stack antenna 5 of the fifth embodiment of the present invention, FIG. 15(b) shows a front view of the same, FIG. 16(a) shows a right side view of the same, FIG. 16(b) shows a rear view of the same, and FIG. 16(c) shows a bottom view of the same, and FIGS. 17(a) and (b) show expanded views of slot elements in the stack antenna 5 of the fifth embodiment. The stack antenna 5 of the fifth embodiment of the present invention shown in these figures is composed of a first antenna in which the first and second stages, each of which is composed of two sets of dipole antennas, are stacked in two stages, and a second antenna in which slot elements B-1 to B-4 are stacked in four stages. The first stage of the first antenna is composed of two sets of dipole antennas composed of a pair of hot elements 21b-1 and a pair of earth elements 21a-1, and the second stage is composed of two sets of dipole antennas composed of a pair of hot elements 21b-2 and a pair of earth elements 21a-2. As shown in Figures 15(b) and 16(b), the pair of hot elements 21b-1, the pair of hot elements 21b-2, the pair of earth elements 21a-1, and the pair of earth elements 21a-2 are formed on a substrate 20 such as a fluororesin substrate having good high-frequency characteristics. The configuration of the substrate 20 and the configurations and dimensions of the pair of hot elements 21b-1 and 21b-2 and the pair of earth elements 21a-1 and 21a-2 are the same as those in the stack antenna 2 of the second embodiment, and therefore description thereof will be omitted.

[0054] In the first stage of the first antenna, two semicircular slot elements B-1 are arranged close to each other so as to surround two sets of dipole antennas consisting of a pair of hot elements 21b-1 and a pair of earth elements 21a-1, and in the second stage, two semicircular slot elements B-3 are arranged close to each other so as to surround two sets of dipole antennas consisting of a pair of hot elements 21b-2 and a pair of earth elements 21a-2. In addition, between the first stage and the second stage, two semicircular slot elements B-2 are arranged so as to surround the substrate 20, and two semicircular slot elements B-4 are arranged so as to surround the upper end of the substrate 20. The installation interval between the two sets of dipole antennas in the first stage and the two sets of dipole antennas in the second stage is L3. The installation interval between the four-stage stacked slot elements B-1 to B-4 is L1, which is 1 / 2 of L3. The slot elements B-1 to B-4 have the same configuration, and are configured as the slot element B shown in FIG. 8(b). Taking the configuration of the slot element B-1 shown in FIG. 19(a) as an example, the slot element B-1 is configured such that the bent portion Ba1 with a radius of θ2 and the bent portion Ba2 with a radius of θ2, which are bent in a semicircular shape and face each other, are arranged so as to be positioned on a circle approximately centered on the central axis of the substrate 20, and the gaps Bc1 and Bc2 are formed between the opposing edges of the bent portion Ba1 and the bent portion Ba2. As shown in FIG. 15(a)(b) and FIG. 16(a)(b), the bent portion Ba1 and the bent portion Ba2 are respectively formed in the approximately central portions thereof with horizontally long narrow slots Bb1 and Bb2, and power is fed from the power feed points to the predetermined positions of the slots Bb1 and Bb2. The substrate 20 is arranged approximately in the center of the bent portion Ba1 and the bent portion Ba2 arranged on the circle.

[0055] The slot elements B-1 to B-4 have the same configuration, and the slot elements B-1 to B-4 are shown in Fig. 17(a) and (b). Fig. 17(a) shows the configuration of the bent portion Ba1 when it is expanded, and Fig. 17(b) shows the configuration of the bent portion Ba2 when it is expanded. As shown in these figures, the bent portion Ba1 and the bent portion Ba2 are made of a metal plate having a horizontally long rectangular shape, and horizontally long narrow slots Bb1 and Bb2 are formed in the center of the bent portion Ba1 and the bent portion Ba2, respectively, and feed points Bd1 and Bd2 are provided at predetermined positions of the slots Bb1 and Bb2, respectively. The slot elements B-1 to B-4 are formed by bending the bent portion Ba1 and the bent portion Ba2 into an arc shape with a radius of θ2. The horizontal width of the bent portion Ba1 and the bent portion Ba2 is SL2, the vertical length is W6, the width of the slots Bb1 and Bb2 is S1 and the length is S2, the power feed point Bd1 is located at a distance S3 from the left end of the slot Bd1, and the power feed point Bd2 is located at a distance S3 from the right end of the slot Bd2. The slot elements B-1 to B-4 constitute a second antenna stacked in four stages. That is, the stack antenna 5 of the fifth embodiment is composed of a composite antenna including a first antenna in which the first and second stages, which are composed of two sets of dipole antennas, are stacked in two stages, and a second antenna in which the slot elements B-1 to B-4 are stacked in four stages. In this case, the first usable frequency band of the first antenna and the second usable frequency band of the second antenna are different, and the stack antenna 2 of the fifth embodiment of the present invention is a wideband antenna that operates in the first usable frequency band and the second usable frequency band. The slot elements B-1 and B-3 arranged in contact with each other so as to surround the two sets of dipole antennas also function as parasitic elements of the first antenna.

[0056] A power feed point (not shown) is disposed at approximately the center between the first and second stages of the first antenna in the stack antenna 5 of the fifth embodiment, and a wide earth line 24 connected to the earth side of the power feed point is formed wide on one surface of the substrate 20 so as to extend vertically approximately along the center line in the longitudinal direction. The tips of a pair of earth elements 21a-1 in the first stage, whose lower ends are bent in an L-shape so as to face each other, are connected to the earth line 24 extending downward from the power feed point, and the tips of a pair of earth elements 21a-2 in the second stage, whose lower ends are bent in an L-shape so as to face each other, are connected to the earth line 24 extending upward from the power feed point. In addition, a branch line 23 connected to the hot side of the power feed point is formed on the other surface of the substrate 20 so as to extend vertically approximately along the center line in the longitudinal direction. The tip of the branch line 23 extending downward from the power feed point is formed into a T-shape, and the tip is further bent downward, and both ends are connected to a pair of hot elements 21b-1 of the first stage via a pair of through holes (not shown). The tip of the branch line 23 extending upward from the power feed point 15 is formed into a T-shape, and the tip is further bent downward, and both ends are connected to a pair of hot elements 21b-2 of the second stage via a pair of through holes (not shown). As a result, power is fed in parallel from the power feed point to the two dipole antennas of the first and second stages via the transmission line consisting of the branch line 23 and the earth line 24. The branch line 23 formed on the other surface of the substrate 20 is formed on a wide earth line 24 formed on one surface of the substrate 20, and the transmission line is a strip line. This strip line feeds power in parallel from the power feed point to two sets of dipole antennas in the first and second stages. The frequency of the signal transmitted and received at the power feed point is set to a frequency in the first usable frequency band. Moreover, the slot elements B-1 to B-4 stacked in four stages are fed in parallel from a feeding point different from the feeding point described above. The frequency of the signal transmitted and received at the different feeding point is set to a frequency of the second usable frequency band.

[0057] The stack antenna 5 of the fifth embodiment of the present invention thus configured has the same dimensions as the stack antenna 1 of the first embodiment. In this case, the hot elements 11b-1 and 11b-2 should be read as hot elements 21b-1 and 21b-2, and the earth elements 11a-1 and 11a-2 should be read as earth elements 21a-1 and 21a-2.

[0058] Since the stack antenna 2 of the fifth embodiment of the present invention is configured as described above, the first antenna, which is made up of two sets of dipole antennas stacked in two stages, and the second antenna, which is made up of slot elements B-1 to B-4 stacked in four stages, are also erected and placed in a vertical plane. As a result, the stack antenna 5 of the fifth embodiment of the present invention operates as a vertically polarized antenna, which is a composite antenna made up of two sets of dipole antennas stacked in two stages and the second antenna, which is made up of slot elements B-1 to B-4 stacked in four stages.

[0059] Here, when the first usable frequency band of the first antenna in which two dipole antennas consisting of a hot element 21b-1 and a ground element 21a-1 and two dipole antennas consisting of a hot element 21b-2 and a ground element 21a-2 are stacked in two stages is f1 (2593MHz) to f2 (3500MHz), the element lengths of the two dipole antennas are derived using the center frequency (3046.5MHz) of the frequency f1 and the frequency f2. When the second usable frequency band of the second antenna in which slot elements B-1 to B-4 are stacked in four stages is f3 (3850MHz) to f4 (4750MHz), the element lengths of the slot elements B-1 to B-4 are derived using the center frequency (4300MHz) of the frequency f3 and the frequency f4. The dimensions of the first antenna of the stack antenna 5 of the fifth embodiment are as follows: the installation interval L1 of the slot elements B-1 to B-4 is about 44 mm, the outer diameter D3 is about 32 mm, the width SL2 is about 46 mm, the length W6 is about 24 mm, the width S1 is about 2 mm, the length S2 is about 34.9 mm, the distance S3 is about 9.6 mm, and the radian angle θ2 is about 170°. The installation interval L3 of the two dipole antennas is about 88 mm, and the width W2 of the substrate 20 is about 20 mm.

[0060] The stack antenna 5 of the fifth embodiment of the present invention operates well in the first usable frequency band of f1 (2593 MHz) to f2 (3500 MHz) and the second usable frequency band of f3 (3850 MHz) to f4 (4750 MHz). It is known that the side lobe is reduced when the element interval / wavelength ratio can be reduced, and the installation interval L1 of the slot elements stacked in four stages is set to about 1 / 2 of the installation interval L3 of the two sets of dipole antennas, so that the side lobe in the second usable frequency band can be reduced. In addition, the stack antenna 5 of the fifth embodiment is a composite antenna of the first antenna in which two sets of dipole antennas are stacked in two stages, and the second antenna in which slot elements B-1 to B-4 are stacked in four stages, and the first antenna and the second antenna are arranged inside each other, so that it can be made compact.

[0061] <Number of stages and antenna characteristics in the stack antenna of the present invention> 18(a) and 18(b) are diagrams for explaining the number of stages and antenna characteristics in the stack antenna of the present invention. Fig. 18(a) is a front view showing the configuration of a stack antenna 6-1 having two sets of dipole antennas stacked in four stages and slot elements A-1 to A-4 stacked in four stages, and Fig. 18(b) is a front view showing the configuration of a tack antenna 6-2 having two sets of dipole antennas stacked in four stages and slot elements A-1 to A-8 stacked in eight stages. In the stack antenna 6-1 shown in Fig. 18(a), the two sets of dipole antennas stacked in four stages have the same configuration as the two sets of dipole antennas constituting the first and second stages in the stack antenna 1 of the first embodiment, so the description is omitted, but the two sets of dipole antennas stacked in four stages are formed on a substrate 60 such as a fluororesin substrate with good high-frequency characteristics, and the installation interval between the two sets of dipole antennas is L13. In the stack antenna 6-1 shown in Fig. 18(a), the slot elements A-1 to A-4 stacked in four stages have the same configuration as the slot elements A-1 and A-3 in the stack antenna 1 of the first embodiment, so the description is omitted, but each of the slot elements A-1 to A-4 is closely arranged so as to surround the two sets of dipole antennas, and the installation interval between the slot elements A-1 to A-4 is L11. The installation interval L11 is the same dimension as the installation interval L13.

[0062] The antenna characteristics of the stack antenna 6-1 will be considered with reference to FIGS. Since the two dipole antennas are stacked in four stages, the side lobe requirement of -12 dB or less is met when the installation interval L13 is approximately 1.12 λ or less. If the operating frequency band of the two dipole antennas stacked in four stages is f1 (2593 MHz) to f2 (3500 MHz), then 1.12 λ1 (λ1 is the wavelength of f1) is approximately 129.6 mm, and 1.12 λ2 (λ2 is the wavelength of f2) is approximately 96.0 mm. From this, the installation interval L13 is approximately 96.0 mm or less. Moreover, since the slot elements A-1 to A-4 are also stacked in four stages, the installation interval L11 is the same dimension as the installation interval L13. If the operating frequency band of the four-stacked slot elements A-1 to A-4 is f3 (3850 MHz) to f4 (4750 MHz), 1.12λ3 (λ3 is the wavelength of f3) is approximately 87.2 mm, and 1.12λ4 (λ4 is the wavelength of f4) is approximately 71.4 mm. From this, the installation interval L11 is approximately 70.7 mm or less. Therefore, if the installation interval is set to L11=L13=70.7 mm or less, the stack antenna 6-1 satisfies the requirement of a side lobe of -12 dB or less in the above two operating frequency bands. In this case, since the half-value angle becomes smaller as the installation interval increases, it is preferable to set the installation interval to L11=L13=70.7 mm.

[0063] Next, in a stack antenna 6-2 shown in FIG. 18(b), the two sets of dipole antennas stacked in four stages have the same configuration as the two sets of dipole antennas stacked in four stages in the stack antenna 6-1, so a description thereof will be omitted. The installation interval between the two sets of dipole antennas is L13. Also, in the stack antenna 6-2 shown in FIG. 18(b), the slot elements A-1 to A-8 stacked in eight stages have the same configuration as the slot elements A-1 to A-8 in the stack antenna 1 of the first embodiment, so a description thereof will be omitted. The installation interval between the slot elements A-1 to A-8 is L11. The installation interval L11 is half the dimension of the installation interval L13.

[0064] The antenna characteristics of the stack antenna 6-2 will be considered with reference to FIGS. The two dipole antennas are stacked in four stages, so as mentioned above, when the installation interval L13 is approximately 96.0 mm or less, the side lobe is -12 dB or less. If the installation interval L13 is 96.0 mm, 96.0 mm is approximately 0.83 λ1, and 96.0 mm is approximately 1.12 λ2, so a half-value angle of approximately 10 deg can be obtained at f2 (3500 MHz). Since 96.0 mm is approximately 0.83 λ1, the half-value angle at f1 (2593 MHz) is approximately 16 deg. Moreover, since the slot elements A-1 to A-8 are stacked in eight stages, when the installation interval L11 is set to approximately 1.12λ or less, the side lobe is satisfied to be -12 dB or less. Here, if the operating frequency band of the eight-stage stacked slot elements A-1 to A-8 is f3 (3850 MHz) to f4 (4750 MHz), 1.12λ3 is approximately 87.2 mm, and 1.12λ4 is approximately 70.7 mm, so that the antenna installation interval L11 is 70.7 mm or less to satisfy the side lobe of -12 dB or less. In this case, the installation interval L11 is 1 / 2 of the installation interval L13, so the installation interval L13 is set to 96.0 mm and the installation interval L11 is set to 48 mm. As a result, the stack antenna 6-2 satisfies the side lobe of -12 dB or less in the above-mentioned two operating frequency bands. In addition, if the installation interval L11 is 48 mm, 48 mm is approximately 0.76 λ4, and at f4 (4750 MHz), the half-value angle satisfies 10 deg or less. Note that 48 mm is approximately 0.62 λ3, so at f3 (3850 MHz), the half-value angle is approximately 11 deg.

[0065] As described above, when two sets of dipole antennas are stacked in four stages, stacking the slot elements in eight stages can improve the antenna characteristics of the stack antenna. Also, when two sets of dipole antennas are stacked in eight stages, stacking the slot elements in 16 stages satisfies the side lobe of -12 dB or less at a half-value angle of 10 deg or less when the installation interval L3 is 88 mm and the installation interval L1 is L3 x (1 / 2) = 44 mm as described above. Therefore, when two dipole antennas are stacked in n stages, the antenna characteristics of the stack antenna can be improved by stacking the slot elements in 2n stages. [Industrial Applicability]

[0066] The stack antenna of the embodiment of the present invention described above is a composite antenna consisting of a first antenna in which dipole antennas are stacked in n stages (n is a power of 2) and a second antenna in which slot elements are stacked in 2n stages, and the first antenna and the second antenna are arranged inside each other. This makes it unnecessary to increase the length of the stack antenna, and makes it possible to reduce the size of the stack antenna. Furthermore, since the second installation interval of the slot elements of the second antenna is half the first installation interval of the dipole antennas of the first antenna, it is possible to satisfy the desired half-value angle and side lobe characteristics. The stack antenna according to the embodiment of the present invention described above may be housed in a cylindrical case, such as a cylindrical case. The electrical length of the hot element and earth element constituting the dipole antenna of the stack antenna according to the embodiment of the present invention is set to a length corresponding to the frequency band used. For example, it is generally set to 1 / 4 wavelength of the wavelength of the center frequency of the frequency band used. In this case, the physical length is determined taking into consideration the wavelength shortening rate due to the dielectric constant of the substrate. The length of the slot of the slot element is set to a length corresponding to the frequency band used. For example, it is generally set to 1 / 2 wavelength of the wavelength of the center frequency of the frequency band used. In addition, in the stack antenna of the embodiment of the present invention described above, an example has been given in which the tilt angle is 5°, but this is not limited to this and the tilt angle can be any desired angle (for example, 3°, 4°, ...). [Explanation of symbols]

[0067] 1 stack antenna, 2 stack antenna, 3 stack antenna, 4 stack antenna, 5 stack antenna, 6-1, 6-2 stack antenna, 10 board, 11a earth element, 11b hot element, 13 branch line, 14 earth line, 15 feed point, 16 slot element, 20 board, 21a earth element, 21b hot element, 23 branch line, 24 earth line, 26a through hole, 26b through hole, 30 board, 35 feed point, 36 feed point, 60 board, 100 broadband antenna, 111a earth element, 111b hot element, 200 broadband antenna, 210 board, 211a earth element, 211b hot element, 213 feed point, 214 branch line, 215 earth line, C-101 to C-108 Parasitic element, Aa bend, Ab slot, Ac gap, Ad slot, Ad feed point, B slot element, Ba1 bend, Ba2 bend, Bb1 slot, Bb2 slot, Bc1 gap, Bc2 gap, Bd1 slot, Bd1 feed point, Bd2 slot, Bd2 feed point, C slot element, Ca bend, Cc gap, D slot element, Da1 bend, Da2 bend, Db1 slot, Db2 slot, Dc1 gap, Dc2 gap, E slot element, Ea cylinder, F slot element, Fa1 bend, Fa2 bend, Fc1 gap, Fc2 gap

Claims

1. A first antenna in which dipole antennas each having a hot element and a ground element are stacked in n stages (n is a power of 2); a second antenna in which arc-shaped slot elements are stacked in 2n stages; A stack antenna characterized in that the first antenna and the second antenna are configured to be arranged inside each other, and a second installation spacing of the slot elements of the second antenna is 1 / 2 of a first installation spacing of the dipole antenna of the first antenna.

2. The device further comprises a substrate, The hot element is formed on one side of the substrate, and the earth element is formed on the other side of the substrate, The stack antenna according to claim 1, characterized in that the slot elements are arranged in close proximity to surround the central portion of the dipole antenna which is formed in n stages, and are arranged so as to surround the spaces between the stages of the dipole antenna and the substrate at the ends of the dipole antenna.

3. a first power supply means including a branch line formed on one surface of the substrate, connected to a hot side of a first power supply point, and supplying power to the hot element of each stage, and an earth connection line formed on the other surface of the substrate, connected to the earth side of the first power supply point, and supplying power to the earth element of each stage; and a second feeding means for feeding the slot elements of each stage from a second feeding point, 3. The stack antenna according to claim 2, wherein the slot elements are arranged on a circle whose center is approximately on a central axis of the substrate.

4. The device further comprises a substrate, the hot element and the earth element are formed on one side of the substrate; The stack antenna according to claim 1, characterized in that the slot elements are arranged in close proximity to surround the central portion of the dipole antenna which is formed in n stages, and are arranged so as to surround the spaces between the stages of the dipole antenna and the substrate at the ends of the dipole antenna.

5. a first power supply means including a branch line formed on the other surface of the substrate and connected to a hot side of a first power supply point to supply power to the hot element of each stage, and an earth connection line formed on one surface of the substrate and connected to an earth side of the first power supply point to supply power to the earth element of each stage; and a second feeding means for feeding the slot elements of each stage from a second feeding point, 5. The stack antenna according to claim 4, wherein the slot elements are arranged on a circle whose center is approximately on a central axis of the substrate.

6. a first antenna in which dipole antennas each having a hot element and a ground element formed on a surface of an elongated substrate are stacked in n stages (n is a power of 2); a second antenna in which arc-shaped slot elements are arranged adjacent to and surrounding the central portion of the dipole antenna of each stage, and which is arranged between the stages of the dipole antenna formed in a plurality of stages below the center of the substrate, and which is stacked in a plurality of stages; A stack antenna characterized in that the first antenna and the second antenna are configured to be arranged inside each other, and the slot elements arranged in close proximity to surround the central portion of the dipole antenna, excluding the dipole antenna formed in multiple stages below the center of the substrate, are parasitic elements.

7. The arc-shaped slot elements are arranged on a circle that is substantially centered on a central axis of the substrate, The stack antenna as described in claim 6, characterized in that the second installation spacing of the slot elements of the second antenna arranged below the center of the substrate is 1 / 2 of the first installation spacing of the dipole antenna of the first antenna.

8. a first antenna in which dipole antennas each having a hot element and a ground element formed on a surface of an elongated substrate are stacked in n stages (n is a power of 2); a second antenna in which arc-shaped slot elements are arranged adjacent to and surrounding a central portion of the dipole antenna of each stage, and are arranged between the stages of the dipole antennas formed in a plurality of stages in the central portion of the substrate, and are stacked in a plurality of stages; A stack antenna characterized in that the first antenna and the second antenna are arranged inside each other, and the slot elements arranged in close proximity to surround the central portion of the dipole antenna, excluding the dipole antenna formed in multiple stages in the central portion of the substrate, are parasitic elements.

9. The arc-shaped slot elements are arranged on a circle that is substantially centered on a central axis of the substrate, The stack antenna as described in claim 8, characterized in that the second installation spacing of the slot elements arranged in the center of the substrate of the second antenna is 1 / 2 of the first installation spacing of the dipole antenna of the first antenna.

10. a first antenna in which dipole antennas each having a hot element and a ground element formed on a surface of an elongated substrate are stacked in n stages (n is a power of 2); a second antenna in which arc-shaped slot elements are arranged adjacent to and surrounding a central portion of the dipole antenna of each stage, and which is arranged between the stages of the dipole antenna formed in a plurality of stages above the center of the substrate, and which is stacked in a plurality of stages; A stack antenna characterized in that the first antenna and the second antenna are configured to be arranged inside each other, and the slot elements arranged in close proximity to surround the central portion of the dipole antenna, excluding the dipole antenna formed in multiple stages above the center of the substrate, are parasitic elements.

11. The arc-shaped slot elements are arranged on a circle that is substantially centered on a central axis of the substrate, The stack antenna as described in claim 10, characterized in that the second installation spacing of the slot elements of the second antenna arranged above the center of the substrate is 1 / 2 of the first installation spacing of the dipole antenna of the first antenna.

12. 12. The stack antenna according to claim 1, wherein the slot element has a slot formed in a lateral direction and is formed in an arc shape with a predetermined arc degree.

13. A stack antenna as described in any one of claims 1 to 11, characterized in that the slot element is configured by a pair of elements having a slot formed in the horizontal direction and formed in an arc shape of a predetermined arc degree, which are arranged symmetrically.

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