Patent Grant
8698689
The present invention relates to a design method for a Rotman lens usable in a multi-beam antenna device utilizable for millimeter band signal transmitting/receiving.
To begin with, a conventional antenna device using a Rotman lens will be explained with its top plan view in
In the conventional antenna device configured as above, when one of the input ports (21),(22), - - - (2m) is excited, electric power is fed into the Rotman lens (1). The electric power in the Rotman lens (1) is extracted from each of the output ports (31),(32), - - - (3n), and transmitted to a corresponding one of the antenna elements (41),(42), - - - (4n) through a respective one of the transmission lines (61),(62), - - - (6n). An excitation amplitude and an excitation phase of the array antenna (5) are determined by which of the input ports (21),(22), - - - (2m) is excited, and the spatial beam direction is determined by the excitation phase of the array antenna (5).
In the conventional antenna device illustrated in
x=[2w(1−g)−b02η2]/2(g−a0) (1)
y=η(1−w) (2)
w=[−b−√{square root over ((b2−4ac))}]/2a (3)
In the above Formulas 1 to 3,
g=G/F,η=Ln/F,a0=cos α,b0=sin α,
a=1−η2−[(g−1)/(g−a0)]2,
b=2g(g−1)/(g−a0)−[(g−1)/(g−a0)2]b02η2+2η2−2g, and
c=gb02η2/(g−a0)−b04η4/[4(g−a0)2]−η2.
Further, the radius R is expressed in the following formula:
R=[(Fa0−G)2+F2+b02]/[2(G−Fa0)] (4)
In the Formula 4, G is a size of the Rotman lens defined by a distance between S2 and S3. Further, F is a distance between the input port (21) and S2, and 2 Ln is an aperture length of the array antenna (5). In the basic design process, it is commonly considered that it is desirable to set approximately in the following range: 0.8<η<1, i.e., set F in a range of about 1 to 1.25 times Ln, and set g to about 1.137, under a defined condition of β=α, in view of an advantage of being able to reduce an error in excitation phase at each of the output ports (31), (32), - - - (3n).
However, in the conventional antenna device illustrated in
b2−4ac≧0 (5)
As a prerequisite to satisfying the Formula 5, η=Ln/F has to be equal to or less than 1 (η=Ln/F≦1). This means that, in cases where the aperture 2 Ln of the array antenna (5) becomes larger due to an increase in the number of the antenna elements (41),(42), - - - (4n), it is necessary to increase the distance F between the input port (21) and S2 in proportion to the aperture 2 Ln of the array antenna (5), resulting in an increase in the size G of the Rotman lens. Therefore, when the number of the antenna elements (41),(42), - - - (4n) is increased, it is necessary to increase the size G of the Rotman lens in conformity to an increasing rate of the antenna elements, which causes a problem that, even though the number of the antenna elements is increased, an appropriate gain enhancement effect cannot be obtained.
The present invention is directed to providing a low-loss multi-beam antenna device capable of, under a condition that β with respect to α is set to satisfy the following relation: β<α, where: β is a spatial beam-forming angle of an array antenna (5); and α is an angle between a center line (8) and a line segment which connects one of a plurality of input ports and an intersecting point S2 of the center line (8) with a curve segment having a plurality of output ports (31), (32), - - - , (3n) arranged thereon, reducing G which is a size of a Rotman lens, to less than a value of G set out through a basic design process, i.e., a basic value of G when designed under a defined condition of β=α, and thereby suppressing an increase in loss of the Rotman lens so as to achieve enhanced gain.
A multi-beam antenna of the present invention is characterized in that, under a condition that β with respect to α is set to satisfy the following relation: β<α, where: β is a spatial beam-forming angle of an array antenna; and α is an angle between a center line (8), and a line segment which connects one of a plurality of input ports and an intersecting point S2 of the center line (8) with a curve segment having a plurality of output ports (31), (32), - - - , (3n) arranged thereon, a shape of a Rotman lens is set to satisfy the following relation: η=(β/α)·(Ln/F)<1 (Formula 6), and reduce G to less than a basic value of G when designed under a defined condition of β=α, where: F is a distance between the one input port (21) and S2; 2 Ln is an aperture length of the array antenna (5); and G is a size of the Rotman lens, and defined as a distance between S2 and S3 (wherein S3 is an intersecting point of the center line (8) with a curve segment having the input ports (21), (22), - - - , (2m) arranged thereon).
In one embodiment of the present invention, the multi-beam antenna device is further characterized in that the Rotman lens is formed using a triplate.
In one embodiment of the present invention, the multi-beam antenna device is further characterized in that the array antenna is formed using a triplate.
In one embodiment of the present invention, the multi-beam antenna device is further characterized in that each of the input ports is partially formed as two branched transmission lines to distribute and feed electric power.
In another aspect, a multi-beam antenna device of the present invention comprises: a Rotman lens having a plurality of input ports (21), (22), - - - , (2m) for feeding electric power, and a plurality of output ports (31), (32), - - - , (3n) for extracting the electric power from the input ports; an array antenna comprised of a plurality of antenna elements and adapted to radiate electromagnetic waves to space; and a plurality of transmission lines connecting respective ones of the output ports to respective ones of the antenna elements, wherein a curve for arranging the output ports thereon and a length of each of the transmission lines are set such that, when a given one of the input ports is excited, a beam is formed in a direction at an angle corresponding to that of the given input port. The multi-beam antenna device is characterized in that: β with respect to α is set to satisfy the following relation: β<α, where: β is a spatial beam-forming angle of the array antenna when viewed from a direction facing a front of the array antenna; and α is an angle between a center line (8) of the Rotman lens, and a line segment which connects one of the input ports and an intersecting point S2 of the center line (8) with a curve segment having the output ports (31), (32), - - - , (3n) arranged thereon; and a shape of the Rotman lens is set to reduce G to less than a value of G when designed under a condition of β=α, where G is a size of the Rotman lens, and defined as a distance between S2 and S3 (wherein S3 is an intersecting point of the center line (8) with a curve segment having the input ports (21), (22), - - - , (2m) arranged thereon).
In yet another aspect, a multi-beam antenna device of the present invention comprises: a Rotman lens having a plurality of input ports (21), (22), - - - , (2m) for feeding electric power, and a plurality of output ports (31), (32), - - - , (3n) for extracting the electric power from the input ports; an array antenna comprised of a plurality of antenna elements and adapted to radiate electromagnetic waves to space; and a plurality of transmission lines connecting respective ones of the output ports to respective ones of the antenna elements, wherein a curve for arranging the output ports thereon and a length of each of the transmission lines are set such that, when a given one of the input ports is excited, a beam is formed in a direction at an angle corresponding to that of the given input port. The multi-beam antenna device is characterized in that the Rotman lens is designed according to a design procedure comprising the steps of: setting a number n of element arrays of the input or output ports; setting an arrangement pitch P of the element arrays; setting a beam number and a beam step angle; setting β with respect to α to satisfy the following relation: β<α, where: β is a spatial beam-forming angle of the array antenna when viewed from a direction facing a front of the array antenna; and α is an angle between a center line (8) of the Rotman lens, and a line segment which connects one of the input ports and an intersecting point S2 of the center line (8) with a curve segment having the output ports (31), (32), - - - , (3n) arranged thereon; calculating Fx which allows b2−4ac=0; setting a value of F; setting a value of G; and calculating respective coordinates (x, y) of the output ports of a number N corresponding to the number n of the element arrays, and a corrective line phase w in each of the output ports, whereby a shape of the Rotman lens is set to reduce G to less than a value of G when designed under a condition of β=α, where G is a size of the Rotman lens, and defined as a distance between S2 and S3 (wherein S3 is an intersecting point of the center line (8) with a curve segment having the input ports (21), (22), - - - , (2m) arranged thereon). In the multi-beam antenna device,
a=1−η2−[(g−1)/(g−a0)]2,
b=2g(g−1)/(g−a0)−[(g−1)/(g−a0)2]b02η2+2η2−2g, and
c=gb02η2/(g−a0)−b04η4/[4(g−a0)2]η2,
where g=G/F, η=(β/α)·(Ln/F), a0=cos α, and b0=sin α.
In still another aspect, an in-vehicle multi-beam antenna device of the present invention comprises: a Rotman lens having a plurality of input ports (21), (22), - - - , (2m) for feeding electric power, and a plurality of output ports (31), (32), - - - , (3n) for extracting the electric power from the input ports; an array antenna comprised of a plurality of antenna elements and each adapted to radiate electromagnetic waves to space; and a plurality of transmission lines connecting respective ones of the output ports to respective ones of the antenna elements, wherein a curve for arranging the output ports thereon and a length of each of the transmission lines are set such that, when a given one of the input ports is excited, a beam is formed in a direction at an angle corresponding to that of the given input port. The multi-beam antenna device is characterized in that β with respect to α is set to satisfy the following relation: β<α, where: β is a spatial beam-forming angle of the array antenna when viewed from a direction facing a front of the array antenna; and α is an angle between a center line (8) of the Rotman lens, and a line segment which connects one of the input ports and an intersecting point S2 of the center line (8) with a curve segment having the output ports (31), (32), - - - , (3n) arranged thereon.
The present invention can provide a low-loss multi-beam antenna device which is capable of, under a condition that β with respect to α is set to satisfy the following relation: β<α, where: β is a spatial beam-forming angle of an array antenna (5); and α is an angle between a center line (8) and a line segment which connects one of a plurality of input ports and an intersecting point S2 of the center line (8) with a curve segment having a plurality of output ports (31), (32), - - - , (3n) arranged thereon, reducing G which is a size of a Rotman lens, to less than a basic value of G when designed under a defined condition of β=α, and thereby suppressing an increase in loss of the Rotman lens so as to achieve enhanced gain.
A multi-beam antenna according to the present invention is characterized in that, under a condition that β with respect to α is set to satisfy the following relation: β<α, where: β is a spatial beam-forming angle of an array antenna (5); and α is an elevation angle between a center line (8), and a line segment which connects one of a plurality of input ports and an intersecting point S2 of the center line (8) with a curve segment having a plurality of output ports (31), (32), - - - , (3n) arranged thereon, a shape of a Rotman lens is set to satisfy the Formula 6, and reduce G to less than a basic value of G when designed under a defined condition of β=α, where: F is a distance between the one input port (21) and S2; G is a size of the Rotman lens, and defined as a distance between S2 and S3; and 2 Ln is an aperture length of the array antenna (5).
Specifically, in cases where a Rotman lens is designed under the defined condition of β=α, as a prerequisite to satisfying the Formula 5, η=Ln/F has to be equal to or less than 1 (η=Ln/F≦1). Further, it is generally considered that it is desirable to set η approximately in the following range: 0.8<η<1, i.e., set F in a range of about 1 to 1.25 times Ln, and set g to about 1.137, in view of an advantage of being able to reduce an error in excitation phase at each of the output ports (31), (32), - - - (3n). Thus, it is preferable to set F and G in the following respective ranges with respect to Ln:
Ln<F<1.25Ln,1.137Ln<G<1.42Ln
Moreover, if the aperture 2 Ln of the array antenna (5) becomes larger due to an increase in the number of the antenna elements (41),(42), - - - (4n), the distance F between the input port (21) and S2 is increased in proportion to 2 Ln, resulting in an increase in the basic value of G.
Differently, in the present invention, for example, assuming that β=α/2, as a prerequisite to satisfying the Formula 5, η=Ln /2 F has to be equal to or less than 1 (η=Ln/2F≦1), and it is desirable to set F in a range of about 0.5 to 0.625 times Ln, and set g to about 1.137, in view of an advantage of being able to reduce an error in excitation phase at each of the output ports (31), (32), - - - (3n). Thus, desirable design can be achieved when F and G are set in the following respective ranges with respect to Ln:
0.5Ln<F<0.625Ln,0.568Ln<G<0.71Ln
In this case, the Rotman lens can be designed to have a size which is ½ times a basic value of G when designed under the defined condition of β=α.
In addition, in the multi-beam antenna of the present invention which is designed based on respective coordinates (x, y) of the output ports (31), (32), - - - , (3n) and respective electrical lengths w of the transmission lines (61),(62), - - - (6n), each calculated using the Formulas 1 to 4, when electric power is fed from a given one of the input ports which has an angle α when viewed from S2, a phase inclination of a line representing respective excitation phases at the antenna elements (41),(42), - - - (4n) on the basis of that at an aperture center of the array antenna (5), as indicated by the straight line 2 in
Thus, in the present invention, under the condition of β<α, a shape of the Rotman lens is set to satisfy the relation of the Formula 6, so that it becomes possible to design a small-sized Rotman lens having a size which is β/α times a basic value of G when designed under the defined condition of β=α. This makes it possible to suppress an increase in loss of the Rotman lens which would otherwise occur in proportion to a size thereof. In addition, even if the aperture 2 Ln of the array antenna (5) becomes larger due to an increase in the number of the antenna elements (41),(42), - - - (4n), and thereby the distance F between the input port (21) and S2 is increased in proportion to 2 Ln, a small-sized Rotman lens having a size reduced to β/α times the basic value of G when designed under the defined condition of β<α can be designed so as to make up a multi-beam antenna device having a spatial beam-forming direction β of the array antenna (5).
As shown in
The above description has been made on an assumption that the present invention is applied to a commonly-used hollow parallel-plate Rotman lens, or a triplate structure in which a Rotman lens substrate (12) is supported by a dielectric having a low approximately equal to that of air. In a parallel plate or a triplate structure using a dielectric having a relative permittivity ∈r, it is apparent that the Formula 6 in the present invention may be handled as the following Formula 7.
η=(1/√{square root over (∈r)})·(β/α)·(Ln/F)<1 (7)
In the multi-beam antenna device according to the first embodiment, a radiation element (56) formed in the antenna substrate (52) illustrated in
The first connection section (58) formed in the antenna substrate (52) is electromagnetically coupled with the connection port sub-section (16) of the transmission line section (7) formed in the Rotman lens substrate (12) illustrated in
In this process, each of a metal spacer (51a, 51b) disposed on a respective one of upper and lower sides of the antenna substrate (52) and a metal spacer (11a, 11b) disposed a respective one of upper and lower sides of the Rotman lens substrate (12) holds a respective one of the antenna substrate (52) and the Rotman lens substrate (12) in a spaced manner, while forming a metal wall around an electromagnetic coupling region between the first connection section (58) formed in the antenna substrate (52) and the connection port sub-section (16) of the transmission line section (7) formed in the Rotman lens substrate (12), so that they can contribute to efficient transmission of electric power without leakage to the surroundings, so as to achieve low-loss characteristics even at high frequencies.
In order to stably hold the antenna substrate (52) and the Rotman lens substrate (12), each of a void (55a, 55b) in the metal spacer (51a, 51b) and a void (14a, 14b) in the metal spacers (11a, 11a) may be filled with a dielectric (71a, 71b).
The metal spacer (11a, 11b) also forms a metal wall around the input port section (17) of the antenna device, so that it can contribute to efficient transmission of electric power to a high-frequency circuit through a second connection hole (15) formed in the second ground conductor (13) without leakage to the surroundings, so as to achieve low-loss characteristics even at high frequencies.
Each of the first connection hole (59) and the second connection hole (15) may be formed as a waveguide opening suited to a frequency band to be used.
In addition, based on the simple laminated structure of the components, transmission/receiving of electric power is performed by means of electromagnetic coupling, so that it is not necessary to ensure high positional accuracy during assembly at a level of conventional assembly accuracy.
Preferably, in the multi-beam antenna device according to the first embodiment, as each of the antenna substrate (52) and the Rotman lens substrate (12), a flexible substrate prepared by laminating a polyimide film to a copper foil is employed, wherein the radiation element (56), the feeder line (57), the first connection section (58), the Rotman lens (1), the transmission line section (7), the connection port sub-section (16) of the transmission line section (7), and the input port section (17) of the antenna device, are formed by etchingly removing an unnecessary part of the copper foil.
The flexible substrate may be prepared by employing a film as a base material and laminating a metal foil, such as a copper foil, onto the film. In this case, the radiation elements and a plurality of the feeder lines connecting therebetween may be formed by etchingly removing an unnecessary part of the copper foil (metal foil). Alternatively, the flexible substrate may be made up using a copper-cladded laminate prepared by laminating a copper foil on a thin resin sheet consisting of a glass cloth impregnated with resin. The film may be made of a material, such as polyethylene, polypropylene, polytetrafluoroethylene, ethylene fluoride-polypropylene copolymer, ethylene-tetrafluoroethylene copolymer, polyamide, polyimide, polyamide-imide, polyarylate, thermoplastic polyimide, polyetherimide, polyether ether ketone, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polysulfone, polyphenylene ether, polyphenylene sulfide, or polymethylpentene. An adhesive may be used for lamination between the film and the metal foil. In view of thermal resistance, dielectric characteristics and versatility, it is preferable to use a flexible substrate prepared by laminating a polyimide film to a copper foil. In view of dielectric characteristics, a fluorine-based film is preferably used.
As the ground conductor or the metal spacer for use in the multi-beam antenna device according to the first embodiment, a metal plate or a coated plastic plate may be used. Particularly, it is preferable to use an aluminum plate in view of an advantage of being able to produce the ground conductor or the metal spacer in a low weight and at a low cost. Alternatively, the ground conductor or the metal spacer may be made up using a flexible substrate prepared by employing a film as a base material and laminating a copper foil onto the film, or a copper-cladded laminate prepared by laminating a copper foil on a thin resin sheet consisting of a glass cloth impregnated with resin. A slot or coupling hole-forming section formed in the ground conductor may be formed by punching based on mechanical press or by etching. In view of simplicity, productivity, etc., the punching based on mechanical press is preferable.
For example, as the substrate-supporting dielectric (71a, 71b) for use in the multi-beam antenna device according to the first embodiment, it is preferable to use a foamed material having a small relative permittivity with respect to air. The foamed material may include: a polyolefin-based foamed material such as polyethylene or polypropylene; a polystyrene-based foamed material; a polyurethane-based foamed material; a polysilicone-based foamed material; and a rubber-based foamed material. Among them, a polyolefin-based foamed material is preferable, because it is lower in the relative permittivity with respect to air.
The multi-beam antenna device according to the first embodiment will be further viewed in terms of dimensions of each member, etc., and described as a second embodiment with reference to
In this process, each of the radiation elements (41) is formed in a square shape having a side length of 1.5 mm which is about 0.38 times a free space wavelength (λo=3.95 mm) at a frequency of 76 GHz. Further, the slot (54) formed in the slotted plate (50) is formed in a square shape having a side length of 2.3 mm which is about 0.58 times the free space wavelength (λo=3.95 mm) at the desired frequency of 76 GHz, and each of the first connection hole (59) formed in the first ground conductor (53) and the second connection hole (15) formed in the second ground conductor (13) is formed as a waveguide opening having a size of 1.25 mm length×2.53 mm width. Twenty four antenna element arrays each made up of the radiation elements (56) formed in the antenna substrate (52) illustrated in
Further, the Rotman lens (1) having the 24 output ports to be formed in the Rotman lens substrate (12) illustrated in
The above members were actually laminated in order as illustrated in
On the other hand, in a conventional Rotman lens designed in the following range: 1.137 Ln<G<1.42 Ln, while satisfying the condition of the Formula 5 under the defined condition of β=α, i.e., =Ln/F<1, it is at least necessary that G=1.137, Ln=10.5 λo, so that the size G of the conventional Rotman lens is set to a value which is about 10.5 times the free space wavelength λo=3.95 mm) at the desired frequency of 76 GHz, i.e., to 41.5 mm. In this case, an insertion loss of the Rotman lens (1) was about 5 dB.
As above, the multi-beam antenna device according to the second embodiment is improved in relative gain by 2.5 dB or more, in comparison on the basis of a loss in a multi-beam antenna device formed by the conventional design process, so that it can achieve excellent characteristics.
In a multi-beam antenna device according to a third embodiment, as shown in
(Supplementary Explanation about Objects and Effects of the Present Invention and Objects and Effects of Conventional Techniques)
As mentioned in the “Background Art”, design of a lens based on the Rotman's concept is generally performed under the condition of β=60. One feature of the present invention is that the present invention makes it possible to design a Rotman lens under the condition of β<α, using the aforementioned modified Rotman process based on the conventional Rotman lens design process. Specifically, under the condition of β<α, β (radiation angle on the side of the antenna elements) is less than a (beam angle on the side of the Rotman lens). Thus, the present invention is effective, particularly, when it a high resolution is required with respect to a narrow angle. For example, in cases where the multi-beam antenna device according to the present invention is mounted in a vehicle, it can realize a detection capability sensitive to a range of about 15 degrees in each of rightward and leftward directions with respect to 0 degree defined by a direction perpendicular to a frontward-rearward direction of the vehicle (i.e., it has an aperture angle of up to about 30 degrees as a total of the rightward and leftward angles).
In other words, the antenna device according to the present invention can obtain ideal electric power and phase distributions required for an in-vehicle antenna device or the like.
There is a conventional technique (the Patent Document 3) where lens design is performed under a condition of β>α, instead of β<α as in the present invention. Just to make sure, the Patent Document 3 will be mentioned below. The invention described in the Patent Document 3 is an antenna device which comprise parallel plates having a plurality of input elements adapted to be excited individually so as to feed electric power, and a plurality of output elements adapted to extract the electric power; and a transmission line for connection with an array antenna comprised of a plurality of antenna elements and adapted to radiate electromagnetic waves to space, wherein a curve for arranging the output elements thereon, and a length of the transmission line, are set based on three focal points on a curve for arranging the input elements thereon, in such a manner that, when a given one of the input elements is excited, a beam is radiated in a direction at an angle corresponding to that of the given input port, and wherein a shape of the curve for arranging the input elements thereon is not a part of a circle.
As can be understood from the above, due to the lens design performed under the condition of β>α (see
Considering the invention described in the Patent Document 3, an application having a need to set β (radiation angle on the side of the antenna elements) to be greater than a (beam angle on the side of the Rotman lens) would include a military radar operable to detect a wide angular range with a less phase error.
Thus, the antenna device according to the present invention and the antenna device described in the patent Document 3 are totally different from each other in terms of a configuration (lens shape) and a problem to be solved (object).
The Patent Document 4 filed by the applicant of this application will also be mentioned below. The Patent Document 4 describes a beam-scanning planar antenna excellent in thinning and simplification of an assembling process and capable of facilitating a reduction in size. The planar antenna comprises a connection module 104 for connection with a system, a Rotman lens module 103, and a beam-scan antenna module 102, which are laminated in this order, wherein the planar antenna is formed by laminating: a third ground conductor 13; a fourth dielectric 34; a Rotman lens substrate 62 having a Rotman lens pattern, a second connection section 52 and a third connection section 92; a third dielectric 33; a second ground conductor 12; a second dielectric 32; a feeder substrate 61 formed with a plurality of antenna groups each comprising a combination of a radiation element 50, a feeder line 40 and a first connection section 51; a first dielectric 31; and a first ground conductor 11, in this order.
Design of the Rotman lens of this beam-scanning planar antenna is performed under the condition of α=β as with the conventional technique, and the number of elements in the planar antenna described in the Patent Document 4 is less than the number of elements in the present invention, as can be understood from directivity characteristics in
(Feature of Present Invention from Perspective of Rotman Lens Design Flow)
One feature of the present invention is that the present invention makes it possible to design a Rotman lens under the condition of β<α, using the aforementioned modified Rotman process based on the conventional Rotman lens design process. This modified Rotman process will be more specifically described based on the flowcharts illustrated in
In the conventional Rotman process, the design is performed under the condition of α=0, and thereby F0=Ln. Further, Fx=β·F0/1. Thus, under the condition of a>β as in the present invention, it is obvious that Fx becomes less than F0 (Fx<F0). Thus, under the condition of α=β, in Fx, η=Ln/F becomes less than 1 (η=Ln/F≦1). In this case, b2−4ac in the Formula 5 has a negative value, which means that the design fails.
Then, in S906, the distance F between the input port (21) and S2 is set. In this case, the distance F is set in the following range: F0<F<1.25 F0. Then, the process advances to S907, wherein the lens size G is set. In this case, the size G is set in the following range: g F0<G<1.25 g F0. Specifically, when the shape factor g=G/F is set to a typical value of 1.136, the size G is set in the following range: 1.136 F0<G<1.4 F0.
Then, in S908, respective coordinates (x, y) of the output ports of a number n corresponding to the number n of the element arrays, and a corrective line phase w in each of the output ports, are calculated.
η=(β/α)·(Ln/F)<1 (6)
Based on the above difference, the design flow based on the modified Rotman process in the present invention is configured as follows. Upon start of the design flow in S911, the process advances to S912, wherein a number n of antenna element arrays is set. Then, the process advances to S913, wherein an arrangement pitch P of the n antenna element arrays is set. Then, the process advances to S914, wherein a beam number and a beam step angle are set. Then, in S915, a ratio of β to α can be set to satisfy the following relationship: α>β, as mentioned above. Then, the process advances to S916, wherein Fx which allows b2−4ac=0 is calculated. Under the condition of α>β, Fx=β·Ln/a. Then, in S917, the distance F between the input port (21) and S2 is set. In this case, the distance F is set in the following range: Fx<F<1.25 Fx. Then, the process advances to S918, wherein the lens size G is set. In this case, the size G is set in the following range: g Fx<G<1.25 g Fx. Specifically, when the shape factor g=G/F is set to a typical value of 1.136, the size G is set in the following range: 1.136 Fx<G<1.4 Fx.
Then, in S919, respective coordinates (x, y) of the output ports of a number n corresponding to the number n of the element arrays, and a corrective line phase w in each of the output ports, are calculated.
(Supplementary Explanation about First and Second Embodiments)
The first and second embodiments have been described together with specific numerical values under the following condition represented by the Formula 6: η=(β/α)·(Ln/F)<1(6). Some supplemental explanation will be added here. In a preferred embodiment, β/α is approximately in the following numerical range;
0.33≦β/α<1
An upper limit value, a standard value and a lower limit value of η are assumed as follows.
(1) Upper Limit Value of η
An upper limit value of η is assumed as η=(β/α)·(Ln/F)≈1. In this case, F is minimized (minimum value in a selection range of F).
(2) Standard Value of η
A standard value of η is assumed as η=(β/α)·(Ln/F)=0.88. In this case, F is optimized (optimal value in the selection range of F).
(3) Lower Limit Value of η
A lower limit value of η is assumed as η=(β/α)·(Ln/F)≦0.5 to 0.7. In this case, F is maximized (maximum value in the selection range of F).
An actual value of F measured when has an upper limit value, a standard value or a lower limit value, is expresses as multiples of wave length λ, and summarized in the following Table 2.
In the conventional process, η=1, and α=β, wherein F is a minimum value, specifically, F has a length of 9λ. This shows that a value equal to or less than the wavelength in the conventional process can be obtained in any case in the above Table 2. In the Table 2.5λ, in the column of η=Standard is a measured value corresponding to the second embodiment.
2 Ln (=(n−1) P) means an aperture length of the array antenna (5), and indicates a distance between one (a central one) of the radiation elements (56) in one of the element arrays on one side of the antenna substrate (52), and one (a central one) of the radiation elements (56) in one of the element arrays on the other side of the antenna substrate (52).
The angle β indicates an angle between a perpendicular line extending from the radiation element (56) toward the slotted plate, and a direction along which a beam is radiated from the radiation element.
In the present invention, in cases where a Rotman lens is designed from preset input port coordinates (x, y), and output port coordinates (x, y) calculated based on the Formulas 5, 6, etc., for example, when the connection portion of the input port is formed as two branched transmission lines, a preset position is two chevron-shaped input port joining points at respective distal ends of the two branched transmission lines. On the other hand, when the connection portion is not branched, the preset position is a center of an opening of a chevron-shaped counterpart input port. This concept for the preset position has heretofore been employed, and can be applied to the output ports in the same manner. Further, it can also be applied to the aftermentioned Table 3.
A level of reduction in G in the present invention as compared to G in the conventional technique will be described below.
G1 in the present invention with respect to G0 in the conventional technique can be technically achieved in the following range: 0.25 G0<G1<0.80 G0. Based on Table 2, the following range would be derived using the aforementioned Formulas: 0.33 G0<G1<0.67 G0. Further, it is noted that a significantly excellent result is actually obtained in the following range: 0.33 G0<G1<0.5 G0.
(Supplementary Explanation about Third Embodiment)
In the same way, an actual measurement result corresponding to the third embodiment is summarized in the following Table 3.
In the conventional process, η=1, and α=β, wherein F is a minimum value, specifically, F has a length of 9λ. This shows that a value equal to or less than the wavelength in the conventional process can be obtained in any case in the above Table 3.
(Supplementary Explanation about
The structure of the multi-beam antenna device according to the first embodiment illustrated in
The first ground conductor 53, the Rotman lens substrate and the second ground conductor are illustrated in
The metal spacer (51a, 51b) and the metal spacer (11a, 11b) are illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-303781 | Nov 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/070108 | 11/30/2009 | WO | 00 | 5/27/2011 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2010/061948 | 6/3/2010 | WO | A |
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| 6480167 | Matthews | Nov 2002 | B2 |
| 7724197 | Hardie et al. | May 2010 | B1 |
| 20020126062 | Matthews | Sep 2002 | A1 |
| 20110285598 | Oota et al. | Nov 2011 | A1 |
| 20120077530 | Wu et al. | Mar 2012 | A1 |
| 20120257653 | Nagaishi et al. | Oct 2012 | A1 |
| Number | Date | Country |
|---|---|---|
| 56-123105 | Sep 1981 | JP |
| 57-093701 | Jun 1982 | JP |
| 57-184305 | Nov 1982 | JP |
| 2000-124727 | Apr 2000 | JP |
| 2003-152422 | May 2003 | JP |
| Entry |
|---|
| Takashi Katagi et al., An Improved Design Method of Rotman Lens Antennas, IEEE Transactions on Antennas and Propagation, May 1984, pp. 524-527, vol. Ap-32, No. 5. |
| Jaeheung Kim, et al., Scaling and Focusing of the Rotman Lens, IEEE Antennas and Propagation Society International Symposium, 2001, pp. 773-776, vol. 2. |
| Number | Date | Country | |
|---|---|---|---|
| 20110241968 A1 | Oct 2011 | US |
