Patent Application
20160365646
Embodiments described herein relate generally to an array antenna device.
In an antenna that transmits radio waves to and receives radio waves from a communications satellite, a sidelobe level is required to be suppressed to a certain level under the ITU-R standard, etc. To satisfy the requirement, an array antenna that includes radiating elements arranged in an array on a rectangular planar substrate and is designed to form a linearly polarized wave by keeping a certain angle with respect to the sides of the planar substrate is known.
In order to form a linearly polarized wave, the radiating elements should be connected to a feed point by a pattern of lines of equal length, respectively. In particular, in the case of forming a linearly polarized wave by keeping a certain angle with respect to the sides of the planar substrate, a method of aligning a direction of connection of feed lines to the radiating elements with a direction of a linearly polarized wave to be formed may be applied.
In the method of forming a linearly polarized wave by keeping a certain angle as described above, however, it is necessary to adjust lengths of the feed lines by making the feed lines meander in order to obtain a pattern of lines of equal length. In this case, characteristics of meandering parts of the feed lines vary according to a frequency of a transmission signal. More specifically, since some parts of the feed lines are bent at an acute angle, some feed lines may be close to other feed lines or radiating elements. In such an area where conductors are close to each other, electromagnetic interference occurs and quality of antenna deteriorates. Further, since the feed lines meander in the above method, there are problems that adjacent feed lines are coupled to each other, the feed lines should be arranged densely, etc.
Various embodiments will be described hereinafter with reference to the accompany drawings.
In general, according to one embodiment, there are provided an array antenna device comprises: a first substrate comprising a first feed point; a second substrate provided under the first substrate and comprising a second feed point; and a 180° hybrid circuit which feeds the first feed point and the second feed point with a phase difference of zero or 180°. The first substrate comprises: a first dielectric layer; a first radiating element array formed by arranging first radiating elements in an array on the first dielectric layer; first feed lines provided on the first dielectric layer and connecting the first feed point to the first radiating elements by a pattern of lines of equal length, respectively, such that the first radiating elements form a linearly polarized wave in a first polarization direction; a first ground conductor layer provided under the first dielectric layer; and a second dielectric layer provided under the first ground conductor layer. The second substrate comprises: a third dielectric layer located under the second dielectric layer; a second radiating element array formed by arranging second radiating elements in an array on the third dielectric layer such that the second radiating elements are opposed to the first radiating elements, respectively; second feed lines provided on the third dielectric layer and connecting the second feed point to the second radiating elements by a pattern of lines of equal length, which is the same as the pattern of the first feed lines, respectively, such that the second radiating elements form a linearly polarized wave in a second polarization direction orthogonal to the first polarization direction; and a second ground conductor layer provided under the third dielectric layer. The first ground conductor layer has openings in positions opposed to the first radiating elements and the second radiating elements. Connecting portions of the first feed lines to the first radiating elements are formed in a direction orthogonal to a direction of connecting portions of the second feed lines to the second radiating elements.
It should be noted that structures common in embodiments are denoted by the same reference numbers or symbols and overlapping explanations are omitted. Each figure is an exemplary diagram of an embodiment to prompt understanding of the embodiment. The shapes, dimensions or ratios in the drawings may differ from those of the actual device, but they can be appropriately changed in consideration of the explanation below and known art.
The first substrate 100 comprises a first dielectric layer 1, a first ground conductor layer 2 provided under the first dielectric layer 1 and a second dielectric layer 3 provided under the first ground conductor layer 2.
On a surface of the first dielectric layer 1, first radiating elements 101 are arranged in an array in two directions orthogonal to each other to form a first radiating element array. On the surface of the first dielectric layer 1, first feed lines 201 are also formed to connect a first feed point F1 provided at an end of the surface to the first radiating elements 101 by equal length.
The second substrate 200 comprises a third dielectric layer 4 and a second ground conductor layer 5 provided under the third dielectric layer 4. On a surface of the third dielectric layer 4, second radiating elements 102 are arranged in an array in positions opposed to the first radiating elements 101, respectively, to form a second radiating element array. On a surface of the third dielectric layer 4, second feed lines 202 are also formed to connect a second feed point F2 provided at an end of the surface to the second radiating elements 102 by equal length.
The structure of each of the first substrate 100 and the second substrate 200 is hereinafter described in detail.
On the first substrate 100, the first radiating element array is formed by, for example, evaporating a metal film onto the surface of the first dielectric layer 1 and then patterning and etching the first radiating elements 101. Each first radiating element 101 is rectangular in
As described above, the first feed lines 201 are provided on the surface of the first dielectric layer 1 and connect the first feed point F1 to the first radiating elements 101 by a pattern of lines of equal length, respectively, such that the first radiating element array forms a linearly polarized wave in a first polarization direction. The pattern of lines of equal length can be implemented by forming the lines into a right-angular branching layout by, for example, etching, together with the first radiating element array. If the feed lines are formed into a branching layout to have equal length, the feed lines do not include a part bent at an acute angle and thus the feed lines are not located close to each other. As a result, quality deterioration of antenna caused by electromagnetic interference between the feed lines can be prevented.
In the above structure, the first feed lines 201 are formed on the surface of the first dielectric layer 1 together with the first radiating elements 101, but the first dielectric layer 1 may be divided into layers and the first feed lines 201 may be formed between these layers. In this case, a pattern of the first feed lines 201 is designed to have feed ends extended under the centers of the first radiating elements 101, respectively, such that they are electromagnetically coupled under the first radiating elements 101.
The first ground conductor layer 2 provided under the first dielectric layer 1 functions as a ground of the first feed lines 201 and prevents electromagnetic interference between the first feed lines 201 and the second feed lines 202. The first ground conductor layer 2 has openings 400 in positions opposed to the first radiating elements 101 and the second radiating elements 102. The openings 400 are provided to combine a linearly polarized wave radiated from the first radiating element array with a linearly polarized wave radiated from the second radiating. element array, and can be formed by, for example, etching.
The second dielectric layer 3 provided under the first ground conductor layer 2 is a layer to insulate the first ground conductor layer 2 from the second radiating elements 102 and the second feed lines 202 formed on the second substrate 200.
On the second substrate 200, the second radiating element array is formed by, for example, evaporating a metal film onto the surface of the third dielectric layer 4 and then patterning and etching the second radiating elements in the same manner as the first radiating element array. Each second radiating element 102 is rectangular in
As described above, the second feed lines 202 are provided on the surface of the third dielectric layer 4 and connect the second feed point F2 to the second radiating elements 102 by a pattern of lines of equal length, which is the same as the pattern of the first feed lines 201, respectively, such that the second radiating element array forms a linearly polarized wave in a second polarization direction orthogonal to the first polarization direction. More specifically, when viewed from a direction perpendicular to the substrates, the first feed lines 201 and the second feed lines 202 are formed such that a direction of lines connected to the first radiating elements 101 is orthogonal to a direction of lines connected to the second radiating elements 102 which are opposed to the first radiating elements 101. The pattern of lines of equal length can be implemented by forming the lines into a right-angular branching layout by, for example, etching, together with the second radiating element array. As described above, quality deterioration of antenna can be prevented by forming the feed lines into a branching layout to have equal length.
In the above structure, the second feed lines 202 are formed on the surface of the third dielectric layer 4 together with the second radiating elements 102, but the third dielectric layer 4 may be divided into layers and the second feed lines 202 may be formed between these layers. In this case, a pattern of the second feed lines 202 is designed to have feed ends extended under the centers of the second radiating elements 102, respectively, such that they are electromagnetically coupled under the second radiating elements 102.
The second ground conductor layer 5 provided under the third dielectric layer 4 functions as a ground of the second feed lines 202.
Next, a structure of a feed system is described.
Connecting portions of the first feed lines 201 to the first radiating elements 101 are formed in the direction orthogonal to the direction of connecting portions of the second feed lines 202 to the second radiating elements 102. The first feed point F1 and the second feed point F2 are connected to output terminals of the 180° hybrid circuit 300, respectively, and are fed with a phase difference of zero or 180°. The 180° hybrid circuit 300 has two input terminals and two output terminals. If a signal is input to one of the input terminals, the 180° hybrid circuit 300 outputs in-phase signals from the two output terminals. If a signal is input to the other of the input terminals, the 180° hybrid circuit 300 outputs signals having a phase difference of 180°, i.e., out-of-phase signals from the two output terminals.
In the first embodiment, a transmitter and a receiver are connected to the two input terminals, respectively, but they are not shown in
As the 180° hybrid circuit 300, for example, a magic-T phase feed circuit can be used. The magic-T phase feed circuit may be either a waveguide type magic-T phase feed circuit 300′ or a magic-T phase feed circuit that can be formed on a substrate using a microstrip line and a slot line. Various well-known magic-T phase feed circuits can be used in place of the magic-T phase feed circuit as appropriate.
The operation of the array antenna device of the first embodiment is hereinafter described.
As described above, a length of a line from the first feed point F1 to each of the first radiating elements 101 is equal to a length of a line from the second feed point F2 to each of the second radiating elements 102. Further, when viewed from the direction perpendicular to the substrates, the first feed lines 201 and the second feed lines 202 are formed such that the direction of lines connected to the first radiating elements 101 is orthogonal to the direction of lines connected to the second radiating elements 102 which are opposed to the first radiating elements 101.
Therefore, if the 180° hybrid circuit 300 feeds the first radiating elements 101 and the second radiating elements 102 in phase with each other or with a phase difference of 180°, two polarized waves orthogonal to each other are combined into a polarized wave at an angle of 45° with respect to each polarized wave and radiated in the direction perpendicular to the substrates.
More specifically, for example, it is assumed that in-phase signals are input to the first feed lines 201 and the second feed lines 202 when a signal is input from the transmitter to the 180° hybrid circuit 300. At this time, it is also assumed that a linearly polarized wave in a direction shown by arrow a in
Next, a difference between a case of feeding the first feed point F1 and the second feed point F2 with a phase difference of 180° and a case of feeding these feed points in phase with each other is described. For example, in the case of feeding the second feed point F2 with a phase difference of 180° from the first feed point F1, the direction of the plane of vibration of the polarized wave radiated from the second radiating elements 102 is reversed in comparison with the case of feeding the second feed point F2 in phase with the first feed point F1. That is, as shown in
As is obvious from the above description, the array antenna device of the first embodiment can radiate a polarized wave having a plane of vibration at an angle of 45° with respect to the connection direction of the feed lines to the radiating elements. In other words, the feed lines can he connected or coupled to the radiating elements in the direction at an angle of 45° with respect to the direction of the plane of vibration of the radiated polarized wave. Therefore, for example, in the case where each radiating element is rectangular, a linearly polarized wave at a desired angle can be radiated without forming the radiating elements at an angle of 45° on the surface of the dielectric layer. Furthermore, intervals between the radiating elements can be reduced in comparison with the case of forming rectangular radiating elements at an angle of 45° with respect to the substrates. Moreover, sufficient space to form lines can be provided without reducing intervals between the radiating elements in comparison with the case of forming rectangular radiating elements at an angle of 45° with respect to the substrates.
In addition, the array antenna device of the first embodiment can change a direction of a plane of vibration of a polarized wave depending on whether it is used for transmission or reception by interchanging the terminals of the 180° hybrid circuit 300 connecting with the transmitter and the receiver. Therefore, the array antenna device of the first embodiment can easily switch the polarization direction even if the antenna is large in size and difficult to rotate.
The array antenna device of the second embodiment having the above structure operates in the same manner as the array antenna device of the first embodiment.
That is, the array antenna device of the second embodiment can radiate a polarized wave having a plane of vibration at an angle of 45° with respect to the connection direction of the feed lines to the radiating elements. In other words, the feed lines can be connected or coupled to the radiating elements in the direction at an angle of 45° with respect to the direction of the plane of vibration of the radiated polarized wave. Therefore, for example, in the case where each radiating element is rectangular, a linearly polarized wave at a desired angle can be radiated without forming the radiating elements at an angle of 45° on the surface of the dielectric layer.
Furthermore, intervals between the radiating elements can be reduced in comparison with the case of forming rectangular radiating elements at an angle of 45° with respect to the substrates. Moreover, sufficient space to form lines can be provided without reducing intervals between the radiating elements in comparison with the case of forming rectangular radiating elements at an angle of 45° with respect to the substrates.
In addition, the array antenna device of the second embodiment can change a direction of a plane of vibration of a polarized wave depending on whether it is used for transmission or reception by interchanging the terminals of the 180° hybrid circuit 300 or 300′ connecting with the transmitter and the receiver. Therefore, the array antenna device of the second embodiment can easily switch the polarization direction even if the antenna is large in size and difficult to rotate.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-036906 | Feb 2014 | JP | national |
This application is a Continuation Application of PCT Application No. PCT/JP2014/076291, filed Oct. 1, 2014 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2014-036906, filed Feb. 27, 2014, the entire contents of all of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2014/076291 | Oct 2014 | US |
| Child | 15245683 | US |
