WO2009093779A1

WO2009093779A1 - Feeding network structure for flat type antenna

Info

Publication number: WO2009093779A1
Application number: PCT/KR2008/002842
Authority: WO
Inventors: Ju-Wan Kim
Original assignee: Microface Co., Ltd
Priority date: 2008-01-25
Filing date: 2008-05-22
Publication date: 2009-07-30
Also published as: EP2237371A2; WO2009093875A2; EP2237371A4; WO2009093875A3; KR20090082146A; KR101035093B1

Abstract

The present invention relates to a feeding network structure for a flat type antenna, which reduces sidelobes by controlling radio wave transmission and reception intensities so that a center of an antenna has radio wave transmission and reception intensities higher than a peripheral portion by configuring a 'T' type distributor of a feeding network in an asymmetrical structure having different widths.

Description

Description FEEDING NETWORK STRUCTURE FOR FLAT TYPE

ANTENNA Technical Field

[1] The present invention relates to a feeding network structure for a flat type antenna, and more particularly, to a feeding network structure for a flat type antenna, which reduces sidelobes by controlling radio wave transmission and reception intensities so that a center of an antenna has radio wave transmission and reception intensities higher than a peripheral portion by configuring a "T" type distributor of a feeding network in an asymmetrical structure having different widths. Background Art

[2] A microwave was progressed by development of a radar during the Second World

War. The microwave represents an electromagnetic wave having a wavelength of 1 mm (300 Hz) to 1 m (30 GHz). Since the microwave has a frequency higher than a very high frequency, the microwave is called an ultra high frequency. The microwave is divided into an EHF (Extremely High Frequency) having a wavelength of several millimeters, an SHF (Super High Frequency) having a wavelength of 1 to 10 cm, and a UHF (Ultra High Frequency) having a wavelength of 0.1 to 1 m for each wavelength area.

[3] A waveguide is used as a transmission passage of such microwave. The waveguide is a metallic pipe used in transmission of the microwave. Since a radio wave may be diverged from a surface of a metallic conductor to the air at the time of using the metallic conductor to guide the radio wave transmitted from a radio transmitter to an antenna, a method of guiding the radio wave into the metallic pipe is used. In particular, the waveguide has low resistance loss and low dielectric loss, no radiation material, functions as a high-pass filter and large power, has large available power, and can be isolated from an external electromagnetic field.

[4] A type of the waveguide includes a rectangular shape, a round shape, an oval shape, and the like. A sectional dimension is determined by the lowest transmittable frequency (cut-off frequency).

[5] A flat-type antenna using the waveguide includes a waveguide antenna.

[6] A configuration of the general waveguide antenna will be described in brief below.

The waveguide antenna includes an upper panel and a lower panel each having waveguides corresponding to each other on a top surface and a bottom surface of each of the upper panel and the lower panel. Cells of the upper panel are opened through the top surface of the upper panel. The upper panel and the lower panel have conductivity. [7] However, a feeding network structure of the existing waveguide antenna has been designed to obtain the maximum antenna gain by supplying the maximum power to the cell at equivalent intensity. An asymmetrical waveguide T type distributor structure has also been used as the feeding network structure of the waveguide antenna due to a size of the antenna. However, an arrangement structure of the asymmetrical waveguide distributor used herein was just a pipeline for supplying a radio wave of equivalent intensity to all the cells. An array antenna in which the radio wave is supplied to each cell with the equivalent intensity has a demerit in that the sidelobes are very high.

[8] The antenna having the high sidelobes may be weak to tapping of transmission and reception signals by a third party and radio wave interference in communication between base stations. Particularly, a reception error caused by the sidelobes often occurs in a region where satellites are densely arranged, such as Europe.

[9] For such reason, a method for enhancing a sidelobe characteristic of the waveguide antenna includes a first method of avoiding a sidelobe beam direction of the waveguide antenna and a second method of controlling output intensities of stacked cells of the waveguide antenna.

[10] However, in the first method, the sidelobe itself is not reduced, but it is just avoided as well as it is difficult to design the waveguide antenna compactly in a rectangular shape. In the second method, most of the waveguide antennas have a structure for maximizing the antenna gain rather than the sidelobe. The existing waveguide antenna was not an antenna having low sidelobes except the method of avoiding the sidelobe beam direction to another direction.

[11] Accordingly, it is required to provide an antenna having the low sidelobes and high antenna gain by allowing the antenna to have selectivity to a radio wave transmitted from a desired direction larger than to a radio wave transmitted from an undesired direction.

Disclosure of Invention Technical Problem

[12] The present invention has been finalized in order to solve the above-described problems. An object of the present invention is to provide a feeding network structure of a flat type antenna capable of reducing sidelobes without changing a structure in order to reduce the sidelobes in a configuration similar to an existing waveguide antenna.

[13] Another object of the present invention is to provide a feeding network structure of a flat type antenna capable of reducing the side lobes by asymmetrical outputs of stacked cells of the waveguide antenna. Technical Solution [14] In order to achieve the above-described object, according to the present invention, there is provided a feeding network structure of a flat type antenna formed on at least one surface of the flat type antenna. In this case, two branch lines of a "T" type distributor branched in the same direction as a direction to reduce sidelobes in a feeding network are formed in an asymmetrical structure in which a branch line comparatively closer to a center of the flat type antenna has a width larger than the other branch line so that power distribution of a radio wave becomes larger toward the center of the flat type antenna from both ends of the flat type antenna on the basis of the direction to reduce the sidelobes.

[15] The flat type antenna may be a waveguide antenna with a waveguide, which serves as the feeding network, formed on a conductive panel, and two branch lines of the "T" type distributor branched in the same direction as a direction to reduce the sidelobes in a waveguide may be formed in an asymmetrical structure in which a branch line comparatively closer to a center of the conductive panel has a width larger than the other branch line so that the power distribution of the radio wave becomes larger toward the center from both ends of the conductive panel on the basis of the direction to reduce the sidelobes.

[16] The waveguide antenna may include a lower panel with a lower waveguide formed on a top surface thereof and an upper panel with an upper waveguide, which corresponds to the lower waveguide, formed on a bottom surface thereof, and a cell of the upper waveguide may be opened through the top surface of the upper panel.

[17] The feeding network structure may further include a horn antenna formed by installing a horn being in communication with the opened cell of the upper panel on a conductive panel and coupled to the top surface of the upper panel.

[18] The feeding network structure may further include a slot antenna formed by installing slots on a conductive panel and coupled to the top surface of the upper panel.

[19] Some of the "T" type distributors of the feeding network may be formed in the asymmetrical structure in which the two branch lines have the widths different from each other.

[20] All "T" type distributors of the feeding network may be formed in the asymmetrical structure in which the two branch lines have the widths different from each other.

[21] The "T" type distributor of the feeding network may be formed in the asymmetrical structure in which the two branch lines have the widths different from each other.

[22] The "T" type distributor of the feeding network may be formed in a symmetrical structure in which the two branch lines have the same width, and an additional conductor for reducing the width may be disposed on a branch line comparatively distant from the center of the flat type antenna.

[23] The two branch lines of the "T" type distributor of the feeding network may be formed in the symmetrical structure in which the two branch lines have the same width, and a protrusion portion for reducing the width may be formed on an inner surface of a branch line comparatively distant from the center of the flat type antenna. [24] The flat type antenna may be a microstrip antenna with a microstrip line, which serves as the feeding network, formed on a substrate, and two branch lines of a "T" type distributor branched in the same direction as the direction to reduce the sidelobes in the microstrip line may be formed in the asymmetrical structure in which a branch line comparatively closer to a center of the substrate has a width larger than the other branch line so that the power distribution of the radio wave becomes larger toward the center of the substrate from both ends of the substrate on the basis of the direction to reduce the sidelobes.

Advantageous Effects

[25] Sidelobes of a flat type antenna are reduced by a feeding network structure of a flat type antenna according to the present invention, resulting in remarkably improving stability in transmitting and receiving a radio wave. In particular, in the case that a waveguide antenna is used as the flat type antenna, the waveguide antenna has a configuration similar to an existing waveguide antenna. Therefore, since the sidelobes are reduced without changing a structure in order to reduce the sidelobes, the stability in transmitting and receiving the radio wave can be remarkably improved. Brief Description of the Drawings

[26] FIG. 1 is a perspective view illustrating a whole configuration of a waveguide antenna according to a first embodiment of the present invention.

[27] FIG. 2 is a perspective view of the lower panel of the waveguide antenna according to the first embodiment of the present invention.

[28] FIG. 3 is a plan view of the lower panel of the waveguide antenna according to the first embodiment of the present invention.

[29] FIG. 4 is a plan view of a waveguide antenna according to a second embodiment of the present invention.

[30] FIG. 5 is a plan view of a waveguide antenna according to a third embodiment of the present invention.

[31] FIG. 6 is a plan view of a waveguide antenna according to a fourth embodiment of the present invention.

[32] FIG. 7 is a perspective view of a whole configuration of a waveguide antenna according to a fifth embodiment of the present invention.

[33] FIG. 8 is a plan view of a lower panel of the waveguide antenna according to the fifth embodiment of FIG. 7.

[34] <Description of Reference Numerals Indicating Primary Elements in the Drawings> [35] 100: WAVEGUIDE ANTENNA, 110: UPPER PANEL, 111: LOWER

WAVEGUIDE, 112: "T" TYPE DISTRIBUTOR, 112a,112b: BRANCH LINE, 113: LOWER CELL, 120: UPPER PANEL, 121: UPPER CELL, 130: HORN ANTENNA, 131: HORN Best Mode for Carrying Out the Invention

[36] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that those skilled in the art can easily carrying out the present invention.

[37] FIG. 1 is a perspective view illustrating a whole configuration of a waveguide antenna according to a first embodiment of the present invention. FIG. 2 is a perspective view of a lower panel of the waveguide antenna according to the first embodiment of the present invention. FIG. 3 is a plan view of the lower panel of the waveguide antenna according to the first embodiment of the present invention.

[38] Referring to FIGS. 1 to 3, a waveguide antenna 100 according to the first embodiment of the present invention includes a lower panel 110 and an upper panel 120. The waveguide antenna 100 may further include a horn antenna 130.

[39] As shown in the drawings, the waveguide antenna 100 according to the first embodiment of the present invention includes the lower panel 110 having a lower waveguide 111 serving as a feeding network formed on a top surface thereof and the upper panel 120 having an upper waveguide corresponding to the lower waveguide 111 of the lower panel 110 formed on a bottom surface thereof. The upper panel 120 and the lower panel 110 each have conductivity. Herein, the upper panel 120 and the lower panel 110 according to this embodiment have a rectangular, but the present invention is not limited to it, and the upper panel 120 and the lower panel 110 may have various shapes including a square shape, and the like. The waveguide antenna 100 according to this embodiment is formed by coupling one upper panel 120 and one lower panel 110, but the present invention is not limited to it, and the waveguide antenna 100 may be formed by coupling two or more upper panels and two or more lower panels or by forming a waveguide in an inside of a single panel.

[40] Hereinafter, structures of the waveguides formed in the upper panel 120 and the lower panel 110 will be described. Herein, since the lower waveguide 111 of the lower panel 110 and the upper waveguide (not shown) of the upper panel 120 correspond to each other, the lower waveguide 111 of the lower panel 110 will be exemplified in the following description.

[41] Referring to FIG. 3, in the lower waveguide 111 of the lower panel 110, two branch lines 112a and 112b of a "T" type distributor 112 branched in a direction to reduce sidelobes are asymmetrical to each other in different widths. That is, among the two branch lines 112a and 112b of the "T" type distributor 112, the branch line 112a positioned comparatively closer to a center on the basis of both ends in the direction to reduce the sidelobes has a width larger than the other branch line 112b. A front end of the lower waveguide 111 forms a lower cell 113.

[42] As described above, the upper panel 120 has the upper waveguide corresponding to the lower waveguide 111 of the lower panel 110 formed on the bottom surface thereof. An upper cell 121 of the upper waveguide is opened through a top surface of the upper panel 120.

[43] The waveguide antenna 100 may be formed by coupling the horn antenna 130 onto the top surface of the upper panel 120. The horn antenna 130 is formed by installing a horn 131 being in communication with the upper cell 121 of the upper panel 120 on a conductive panel.

[44] According to the above-described configuration, during a process in which a radio wave received through the cell of the waveguide antenna 100 flows through the waveguide 111 serving as the feeding network of the waveguide antenna 100, power distribution of the radio wave is gradually increased in a direction of a center portion of the waveguide antenna 100 while the radio wave passes through the "T" type distributor 112. As a result, as the center portion of the waveguide antenna 100 has a maximum radiation characteristic, the sidelobes of the waveguide antenna 100 are comparatively reduced.

[45] Graphs 1 to 3 show the radiation characteristic of a general waveguide antenna having a structure in which power of the radio wave is equivalently distributed to cells of the waveguide. Graphs 4 to 6 show the radiation characteristic of the waveguide antenna having a structure in which the power distribution of the radio wave in the direction of the center portion of the waveguide is gradually increased according to the first embodiment of the present invention.

[46] Graph 1

[47] 10. 7 [GHz]

[48]

Theta/Degree

[49] Graph 2 [50] 11.7 [GHz] [51]

Theta/Degree

[52] Graph 3 [53] 12.27 [GHz]

[54]

Theta/Degree

[55] Graph 4 [56] 10. 7 [GHz] [57]

Theta/Degree

[58] Graph 5 [59] 11.7 [GHz] [60]

Theta/Degree

[61] Graph 6

[62] 12.27 [GHz]

[63]

Theta/Degree

[64] As can be confirmed from the graphs, the radiation characteristic of the waveguide antenna according to the first embodiment of the present invention reduces the sidelobes in comparison with the radiation characteristic of the existing waveguide antenna. Therefore, in the waveguide antenna 100 according to this embodiment, a phenomenon that a radio wave generated in a direction except a direction of a is received by is remarkably reduced and thus interference caused by adjacent satellites or other noise is remarkably reduced, resulting in improving a radio wave reception characteristic of the waveguide antenna 100. In particular, when the waveguide antenna 100 according to the first embodiment of the present invention is used in a region where satellites are densely arranged, such as Europe, it is possible to acquire a larger effect.

[65] An asymmetrical structure may be applied to all "T" type distributors formed in the waveguide of the waveguide antenna and the asymmetrical structure may be applied to only some "T" type distributors in the same manner as in this embodiment.

[66] Next, a waveguide antenna according to a second embodiment of the present invention will be described.

[67] FIG. 4 is a plan view of the waveguide antenna according to the second embodiment of the present invention.

[68] In a waveguide antenna 200 according to the second embodiment of the present invention, the asymmetrical structure is also applied to two branch lines 202a and 202b of a "T" type distributor 202 directly connected to a cell 203, which are opposite to each other. That is, even in the "T" type distributor 202 connected to the cell 203 of the waveguide antenna 200, the branch line 202a comparatively closer to a center of the waveguide antenna 200 among the branch lines 202a and 202b in two opposite directions has a width larger than the opposite branch line 202b.

[69] According to the above-described configuration, in the waveguide antenna 200 according to this embodiment, the power distribution of the radio wave becomes larger toward the center of the waveguide antenna 200 in comparison with the waveguide antenna 100 according to the first embodiment of FIGS. 1 and 2. That is, in the waveguide antenna 200 according to this embodiment, the sidelobes are further reduced in comparison with the waveguide antenna 100 according to the first embodiment of FIGS. 1 and 2.

[70] Herein, even though the waveguide antenna has low sidelobes, the waveguide antenna does not always have an excellent transmission and reception characteristic. Therefore, it is possible to control the sidelobes by properly adjusting an application position of the asymmetrical structure to the "T" type distributor of the waveguide antenna in consideration of a position of a peripheral radio wave generation source and a relationship with the peripheral radio wave generation source for receiving the radio wave.

[71] Next, a structure of the "T" type distributor of a waveguide antenna according to a third embodiment of the present invention will be described.

[72] FIG. 5 is a plan view illustrating the structure of the "T" type distributor of the waveguide antenna according to the third embodiment of the present invention.

[73] As shown in the drawing, in a "T" type distributor 302 of the waveguide antenna 300 according to this embodiment, widths of two branch lines 302a and 302b of the "T" type distributor 302 opposite to each other are asymmetrical to each other by a conductor 303 through coupling a conductor 303 to the branch line 302a comparatively closer to a center of the waveguide antenna 300 among the two branch lines 302a and 302b opposite to each other. That is, the branch lines 112a and 112b themselves of the "T" type distributor 112 are asymmetrical to each other in the waveguide antenna 100 according to the first embodiment of FIGS. 1 to 3, while the two branch lines 302a and 302b of the "T" type distributor 302 of the waveguide antenna 300 according to this embodiment, which are opposite to each other, are symmetrical to each other and the width of the branch line 302a is reduced by installing the conductor 303 in the branch line 302a comparatively closer to the center of the waveguide antenna 300 among the two branch lines 302a and 302b of the "T" type distributor 302, which are opposite to each other. Reference numeral 304 that is not described represents a cell of the waveguide antenna 300.

[74] The waveguide antenna 300 employing the "T" type distributor 302 having the above-described configuration may also reduce the sidelobes in the same principle as the waveguide antenna 100 according to the first embodiment of FIGS. 1 to 3.

[75] Next, a structure of a "T" type distributor of a waveguide antenna according to a fourth embodiment of the present invention will be described.

[76] FIG. 6 is a plan view illustrating the structure of the "T" type distributor of the waveguide antenna according to the fourth embodiment of the present invention.

[77] As shown in the drawing, in a "T" type distributor 402 of a waveguide antenna 400 according to this embodiment, a protrusion portion 403 for reducing a width of a branch line 402a comparatively closer to a center of the waveguide antenna 400 among two branch lines 402a and 402b opposite to each other is formed on an inner surface of the branch line 402a. Reference numeral 404 that is not described represents a cell of the waveguide antenna 400.

[78] The waveguide antenna 400 employing the "T" type distributor 402 having the above-described configuration also may reduce the sidelobes in the same principle as the waveguide antenna 100 according to the first embodiment of FIGS. 1 to 3.

[79] Next, a waveguide antenna according to a fifth embodiment of the present invention will be described.

[80] FIG. 7 is a perspective view illustrating a whole configuration of the waveguide antenna according to the fifth embodiment of the present invention. FIG. 8 is a plan view of a lower panel of the waveguide antenna according to the fifth embodiment of FIG. 7. [81] A waveguide antenna 500 according to the fifth embodiment of the present invention includes a conductive lower panel 510, a conductive upper panel 520, and a slot antenna 530.

[82] The lower panel 510 has a lower waveguide 511 formed on a top surface thereof and the upper panel 520 has an upper waveguide (not shown), which corresponds to the lower waveguide 511 of the lower panel 510, formed a bottom surface thereof. Herein, the upper panel 510 and the lower panel 520 according to this embodiment have the square shape.

[83] Structures of the waveguides formed in the upper panel 520 and the lower panel 510 will now be described. Herein, since the lower waveguide 511 of the lower panel 510 and the upper waveguide (not shown) of the upper panel 520 correspond to each other, the lower waveguide 511 of the lower panel 510 will be exemplified in the following description.

[84] Referring to FIG. 8, in the lower waveguide 511 of the lower panel 510, two branch lines 512a and 512b of the "T" type distributor 512 branched in the direction to reduce the sidelobes have different widths and are asymmetrical to each other. That is, among the two branch lines 512a and 512b of the "T" type distributor 512, the branch line 512a positioned comparatively closer to a center on the basis of both ends in the direction to reduce the sidelobes has a width larger than the other branch line 512b. A front end of the lower waveguide 511 forms a lower cell 513.

[85] As described above, the upper panel 520 has the upper waveguide corresponding to the lower waveguide 511 of the lower panel 510 formed on the bottom surface thereof. An upper cell 521 of the upper waveguide is opened through a top surface of the upper panel 520.

[86] The waveguide antenna 500 may be formed by coupling the slot antenna 530 onto the top surface of the upper panel 520. Herein, the slot antenna 530 is formed by installing a plurality of slots 531 on a conductive panel.

[87] Since the sidelobes are reduced by the waveguide antenna 500 having the above- described configuration in the same principle as the sidelobes are reduced by the waveguide antennas according to the embodiments of FIGS. 1 to 6, the detailed description thereof will be omitted in the fifth embodiment.

[88] In the above-described embodiments, although the feeding network of the flat type antenna has been described by using the waveguide antenna serving as the flat type antenna, the present invention is not limited to it and the feeding network structure may be applied to all flat type antennas with a feeding network formed on at least one surface thereof.

[89] For example, the feeding network structure may be applied to a microstrip antenna with a microstrip line, which serves as the feeding network, formed on a substrate. That is, among two branch lines of a "T" type distributor branched in the direction to reduce the sidelobes in the microstrip line, a branch line comparatively closer to a center of the substrate may have a width larger than the other branch line in the asymmetrical structure so that power distribution of the radio wave becomes larger toward the center of the substrate from both ends of the substrate on the basis of the direction to reduce the sidelobes.

[90] Only one embodiment for carrying out the waveguide slot antenna according to the present invention has been shown and described. The present invention is not limited to the above-described embodiments, and it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.

[91]

[92]

Claims

[1] A feeding network structure of a flat type antenna formed on at least one surface of the flat type antenna, wherein two branch lines of a "T" type distributor branched in the same direction as a direction to reduce sidelobes in a feeding network are formed in an asymmetrical structure in which a branch line comparatively closer to a center of the flat type antenna has a width larger than the other branch line so that power distribution of a radio wave becomes larger toward the center of the flat type antenna from both ends of the flat type antenna on the basis of the direction to reduce the sidelobes.

[2] The feeding network structure of claim 1 , wherein the flat type antenna is a waveguide antenna with a waveguide, which serves as the feeding network, formed on a conductive panel, and two branch lines of the "T" type distributor branched in the same direction as a direction to reduce the sidelobes in a waveguide are formed in an asymmetrical structure in which a branch line comparatively closer to a center of the conductive panel has a width larger than the other branch line so that the power distribution of the radio wave becomes larger toward the center from both ends of the conductive panel on the basis of the direction to reduce the sidelobes.

[3] The feeding network structure of claim 2, wherein the waveguide antenna includes a lower panel with a lower waveguide formed on a top surface thereof and an upper panel with an upper waveguide, which corresponds to the lower waveguide, formed on a bottom surface thereof, and a cell of the upper waveguide is opened through the top surface of the upper panel.

[4] The feeding network structure of claim 3, further comprising: a horn antenna formed by installing a horn being in communication with the opened cell of the upper panel on a conductive panel and coupled to the top surface of the upper panel.

[5] The feeding network structure of claim 3, further comprising: a slot antenna formed by installing slots on a conductive panel and coupled to the top surface of the upper panel.

[6] The feeding network structure of claim 1 , wherein some of the "T" type distributors of the feeding network are formed in the asymmetrical structure in which the two branch lines have the widths different from each other.

[7] The feeding network structure of claim 1, wherein all "T" type distributors of the feeding network are formed in the asymmetrical structure in which the two branch lines have the widths different from each other.

[8] The feeding network structure of claim 1 , wherein the "T" type distributor of the feeding network is formed in the asymmetrical structure in which the two branch lines have the widths different from each other.

[9] The feeding network structure of claim 1 , wherein the "T" type distributor of the feeding network is formed in a symmetrical structure in which the two branch lines have the same width, and an additional conductor for reducing the width is disposed on a branch line comparatively distant from the center of the flat type antenna.

[10] The feeding network structure of claim 1 , wherein the two branch lines of the "T" type distributor of the feeding network are formed in the symmetrical structure in which the two branch lines have the same width, and a protrusion portion for reducing the width is formed on an inner surface of a branch line comparatively distant from the center of the flat type antenna.

[11] The feeding network structure of claim 1 , wherein the flat type antenna is a microstrip antenna with a microstrip line, which serves as the feeding network, formed on a substrate, and two branch lines of a "T" type distributor branched in the same direction as the direction to reduce the sidelobes in the microstrip line are formed in the asymmetrical structure in which a branch line comparatively closer to a center of the substrate has a width larger than the other branch line so that the power distribution of the radio wave becomes larger toward the center of the substrate from both ends of the substrate on the basis of the direction to reduce the sidelobes.