Antenna equipment

Abstract

In an antenna device that focuses electromagnetic waves to multiple focal points, this contributes to equalizing the path length of the electromagnetic waves at each of the multiple focal points and eliminating the phase difference. [Solution] The antenna device according to the present disclosure comprises a first electromagnetic wave focusing member that focuses electromagnetic waves incident parallel to a predetermined first direction to a first focal point, and a second electromagnetic wave focusing member that is incident parallel to the first electromagnetic wave focusing member from a predetermined second direction different from the first direction, and focuses the electromagnetic waves reflected by the first electromagnetic wave focusing member to a second focal point different from the first focal point.

Description

[Technical Field]

[0001] This disclosure relates to an antenna device. [Background technology]

[0002] For example, there are known antennas that focus electromagnetic waves incident on the reflective surface of a parabolic antenna from multiple directions to focal points corresponding to each of those directions. Furthermore, Patent Document 1 discloses an antenna device that controls the direction of a beam using a meta-surface. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2023-514436 [Overview of the project] [Problems that the invention aims to solve]

[0004] The disclosures in the above prior art documents are incorporated into this document by reference. The following analysis was performed by the inventors.

[0005] For example, when electromagnetic waves incident on the reflective surface of a parabolic antenna from multiple directions are focused to a focal point corresponding to each of those directions, a phase difference occurs due to the difference in path length between the electromagnetic waves reflected from different positions on the reflective surface. On the other hand, in an antenna device that focuses electromagnetic waves to multiple focal points, there is no known method for compensating for the path length and phase difference of the electromagnetic waves at each of the multiple focal points.

[0006] In view of the above-mentioned problems, the purpose of this disclosure is to contribute to equalizing the path difference of electromagnetic waves at each of the multiple focal points and eliminating the phase difference in an antenna device that focuses electromagnetic waves at each of the multiple focal points. [Means for solving the problem]

[0007] In one aspect of this disclosure, an antenna device is provided comprising a first electromagnetic wave focusing member and a second electromagnetic wave focusing member. The first electromagnetic wave focusing member focuses electromagnetic waves incident parallel to it from a predetermined first direction to a first focal point. The second electromagnetic wave focusing member receives electromagnetic waves incident parallel to the first electromagnetic wave focusing member from a predetermined second direction different from the first direction, guides the electromagnetic waves reflected by the first electromagnetic wave focusing member, and focuses them to a second focal point different from the first focal point. [Effects of the Invention]

[0008] From one perspective of this disclosure, in an antenna device that focuses electromagnetic waves to multiple focal points, it is possible to equalize the path difference of the electromagnetic waves at each of the multiple focal points and contribute to eliminating the phase difference. [Brief explanation of the drawing]

[0009] [Figure 1A] Figure 1A illustrates an example of a cross-sectional view and a top view of a parabolic antenna for angular diversity. [Figure 1B] Figure 1B illustrates how a radio signal incident on the parabolic antenna shown in Figure 1A at an angle of θ with respect to the z-axis does not converge to a single point near the secondary focus SF. [Figure 2A] Figure 2A is a cross-sectional view of an example of a reflective multifocal center-type parabolic antenna according to a first embodiment of the present disclosure. [Figure 2B] Figure 2B is a diagram illustrating a cross-sectional view of an example of a sub-reflector shown in Figure 2A. [Figure 2C] Figure 2C illustrates an example of the path of a radio wave signal when the sub-reflector is composed only of a reflector and no transmission correction member is provided on the reflective surface of the reflector. [Figure 2D] Figure 2D is a cross-sectional view of an example of a reflective multifocal offset parabolic antenna according to a first embodiment of the present disclosure. [Figure 3A]Figure 3A is a cross-sectional view of an example of a transmissive multifocal center-type parabolic antenna according to a second embodiment of the present disclosure. [Figure 3B] Figure 3B is a diagram illustrating an example of the configuration of the transmission correction member shown in Figure 3A. [Figure 3C] Figure 3C is a cross-sectional view of an example of a transmission-type multifocal offset parabolic antenna according to a second embodiment of the present disclosure. [Figure 4A] Figure 4A illustrates a modified example of the reflective multifocal center-type parabolic antenna shown in Figure 2A. [Figure 4B] Figure 4B illustrates a modified example of the transmissive multifocal center-type parabolic antenna shown in Figure 3A. [Figure 4C] Figure 4C illustrates a modified example of the reflective multifocal center type parabolic antenna and the transmissive multifocal center type parabolic antenna shown in Figures 2A and 3A. [Figure 5A] Figure 5A illustrates a modified parabolic antenna that uses a transmission correction member instead of a main reflector. [Figure 5B] Figure 5B illustrates a modified parabolic antenna that uses a transmission correction member instead of a main reflector. [Figure 6A] Figure 6A is a diagram illustrating one configuration of the transmission correction member shown in Figures 2B, 3B, etc. [Figure 6B] Figure 6B shows the arrangement patterns of adjacent elements that should be considered when calculating the path length corresponding to the amount of phase change that should be applied to a single element. [Figure 6C] Figure 6C illustrates an example of the physical distance between three adjacent elements in the arrangement shown in Figure 6A. [Figure 6D] Figure 6D is a diagram illustrating one configuration of the element shown in Figure 6A. [Figure 6E] Figure 6E illustrates an example of the shape of the resonator shown in Figure 6D. [Figure 6F] Figure 6F is a diagram showing the frequency-to-effective relative permeability characteristics of the element shown in Figure 6D, in Kraff format. [Figure 6G] Figure 6G is a schematic diagram showing an example of a split-ring resonator. [Figure 6H] Figure 6H illustrates an example of the wavefront of a radio wave signal generated by multiple elements, each with a different refractive index. [Figure 7] Figure 7 is a flowchart that schematically illustrates one method for designing the reflective surface of the sub-reflector or the correction surface of the support member of the transmission correction member shown in Figures 2B, 3C, etc., and for setting the relative permittivity and relative permeability of each of the numerous elements. [Figure 8] Figure 8 is a schematic diagram illustrating one hardware configuration of a processing unit that performs the processing shown in Figure 7. [Figure 9A] Figure 9A illustrates the positions of the cross-section of the primary reflector, points A and A' moving on the cross-section of the primary reflector, the reference point C located on the negative side of the x-axis in the cross-section of the primary reflector, the intersection points D and D' of the radio wave signal passing through point A and the reference wavefront, the primary focus MF, the secondary focus SF, and the reference wavefront of the radio wave signal passing through point C. [Figure 9B] Figure 9B illustrates points A, B, reference point C, and secondary focus SF used to derive the shape of the correction surface in a two-dimensional plane. [Figure 10A] Figure 10A illustrates an example of a radio wave signal that is incident on point A on the reflective surface of the main reflector and reflected. [Figure 10B] Figure 10B illustrates an example of the position of point A on the main reflector of a parabolic antenna, the primary focus MF, the secondary focus SF, and point B on the correction plane corresponding to point A. [Figure 10C] Figure 10C is a perspective view illustrating the reference wavefront and normal vector w of a radio wave signal incident on the reflective surface of a parabolic antenna's mirror at an angle of θ with respect to the z-axis. [Figure 10D] Figure 10D illustrates an example of a radio wave signal incident on the main reflector, tilted by θ with respect to the z-axis and ψ with respect to the x-axis. [Figure 10E] Figure 10E is a plan view of Figure 10D, seen from the positive z-axis to the negative z-axis. [Figure 11A]Figure 11A illustrates an example of radio wave signals passing through two adjacent elements in the same row on the correction surface, separated into the incident and outgoing sides of the radio wave signals. [Figure 11B] Figure 11B illustrates an example of a curved wave (a radio wave) that is incident on and emitted from two adjacent elements. [Figure 11C] Figure 11C shows the incident side as shown in Figure 11A. [Figure 11D] Figure 11D is a diagram showing the exit side as shown in Figure 11A. [Figure 11E] Figure 11E illustrates an example of a path length lφ(i) corresponding to the phase change φi that should be applied to the radio wave signal passing through the element. [Figure 12A] Figure 12A is a diagram illustrating the overview of the phase error correction process using the bisection method on the correction surface. [Figure 12B] Figure 12B illustrates the cross-sectional view of the corrected surface before correction by the correction process, using dotted lines, and the cross-sectional view of the corrected surface after correction, using solid lines. [Figure 12C] Figure 12C illustrates the total path length of the radio signal with respect to the x-coordinate of the cross-section of the main reflector before correction processing, and the total path length of the radio signal with respect to the x-coordinate of the cross-section of the main reflector after correction processing. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. However, this disclosure is not limited to the embodiments described below. In each drawing, the same or corresponding elements are appropriately denoted by the same reference numerals, and the same or corresponding processes and communications are appropriately denoted by the same reference numerals. Furthermore, it should be noted that the drawings are schematic, and the number, shape, and dimensions of each element, as well as the relationships between the number, dimensions, and proportions of each element, may differ from reality. Also, the number of components, the relationships between shapes and dimensions, and the proportions may differ between drawings.

[0011] Figure 1A illustrates an example of a cross-sectional view and a top view of a parabolic antenna 1 for angular diversity. As shown in Figure 1A, a coordinate system defined by mutually orthogonal coordinate axes x, y, and z is used as appropriate in each figure. The parabolic antenna 1 comprises a main reflector 100, a main horn antenna 110 positioned at the main focus (MF), and a secondary horn antenna 112 positioned at the secondary focus (SF). The configuration of the antenna device provided in this disclosure corresponds to the configuration shown in Figures 2A, 2B, 3A, 3C, 5A, and 5B.

[0012] The main horn antenna 110 is, for example, circular when viewed from above, and the z-coordinate of the cross-section of the reflective surface of the main reflector 100 on the xz-plane is z=x 2 It is given by / 4p. The main horn antenna is located at (0,0,p) on the z axis of the xyz coordinate system (p is the focal length of the main reflector 100). On the other hand, the focal point (sub-focus) SF of electromagnetic waves incident at an angle θ (°) predetermined by the designer with respect to the z axis is not on the z axis and is in a different position from the main focus MF.

[0013] Parabolic antenna 1, through these components, focuses electromagnetic waves incident parallel to the z-axis at the main focus MF and receives them with the main horn antenna 110, and focuses electromagnetic waves incident at an angle θ to the z-axis at the secondary focus SF and receives them with the secondary horn antenna 112. The electromagnetic waves received by the main horn antenna 110 and the secondary horn antenna 112 are guided as electrical signals to a combiner (not shown) via a waveguide or coaxial cable, and are combined by the combiner. Parabolic antenna 1 achieves angular diversity, which compensates for the received intensity of electromagnetic waves, by combining the electrical signals obtained from the radio wave signals received by the main horn antenna 110 and the secondary horn antenna 112.

[0014] The parabolic antenna 1, as illustrated in Figure 1A, can receive electromagnetic waves of various wavelengths, such as radio signals of various frequencies including SHF (Super High Frequency), UHF (Ultra High Frequency), VHF (Very High Frequency), or HF (High Frequency), or optical signals of various wavelengths such as ultraviolet light, visible light, or infrared light, depending on the size of the main reflector 100, main horn antenna 110, and sub-horn antenna 112. However, in the following description, the case where the parabolic antenna 1 receives radio signals will be used as a specific example. Furthermore, the parabolic antenna 1 can be used not only to receive radio signals but also to transmit them, but in the following description, the case where the parabolic antenna 1 receives radio signals will be used as a specific example. Also, in the following drawings, the top view and the main horn antenna 110 and sub-horn antenna 112 are omitted.

[0015] Figure 1B illustrates how a radio wave signal incident on the parabolic antenna 1 shown in Figure 1A, at an angle of θ with respect to the z-axis, does not converge to a single point near the sub-focus SF. As shown in Figure 1B, a radio wave signal tilted by θ with respect to the z-axis does not converge to a single point at the sub-focus SF even when reflected by various parts of the main reflector 100. In other words, when a radio wave signal tilted by θ with respect to the z-axis is reflected by various parts of the main reflector 100, the path length at the sub-focus SF is not constant, resulting in a phase difference. Consequently, when the parabolic antenna 1 receives a radio wave signal tilted by θ with respect to the z-axis, the signal strength decreases. For these reasons, it is desirable that the parabolic antenna 1 converges not only radio wave signals incident parallel to the z-axis but also radio wave signals incident at an angle to the z-axis to a single point, and that there are no differences in path length or phase. The embodiments of the present disclosure described below are configured to meet these requirements.

[0016] [First Embodiment] First, a first embodiment of the present disclosure will be described. Figure 2A is a cross-sectional view of an example of a reflective multifocal center type parabolic antenna 20 (antenna device) according to the first embodiment of the present disclosure. The parabolic antenna 20 illustrated in Figure 2A is a parabolic antenna 1 shown in Figure 1A and includes a sub-reflector 200 located further away from the main reflector 100 than the sub-focus SF, which is incident on the main reflector 100 in a direction tilted by θ with respect to the z-axis (second direction), and which equalizes the path length of the radio wave signals reflected by each part of the main reflector 100, aligns the phase, and focuses them at the sub-focus SF. In the parabolic antenna 20, radio wave signals incident in a direction parallel to the z-axis (first direction) are reflected by the main reflector 100 and focused at the main focus MF (first focus), and radio wave signals incident at an angle of θ with respect to the z-axis are reflected by the main reflector 100, further reflected by the sub-reflector 200, and focused at the sub-focus SF (second focus) with equal path length and no phase difference.

[0017] The radio signal focused at the primary focus (MF) and the radio signal focused at the secondary focus (SF) are received by the primary horn antenna 110 and the secondary horn antenna 112 (not shown in Figure 2A), respectively, converted into electrical signals, guided via waveguides or coaxial cables, and combined by a combiner (neither shown). These components enable the parabolic antenna 20, similar to the parabolic antenna 1, to achieve angular diversity, compensating for the received intensity of radio signals incident parallel to the z-axis and radio signals incident at an angle of θ with respect to the z-axis. Alternatively, the parabolic antenna 20 receives both radio signals incident parallel to the z-axis and radio signals incident at an angle of θ with respect to the z-axis with high gain.

[0018] Figure 2B is a diagram illustrating a cross-sectional view of an example of the sub-reflector 200 shown in Figure 2A. As shown in Figure 2B, the sub-reflector 200 (second electromagnetic wave focusing member) has a reflector 202 (second reflector) and a correction member 204 (first correction member) disposed on and attached to the reflective surface of the reflector 202. The shape of the reflective surface of the reflector 202 is designed as described later with reference to Figure 7, etc. Radio wave signals that are incident on the reflective surface of the main reflector 100 (first electromagnetic wave focusing member; first reflector) in a direction tilted by θ with respect to the z axis (second direction), and reflected by the reflective surface of the main reflector 100, are incident on the reflective surface of the sub-reflector 200 via the correction member 204. The reflective surface of the sub-reflector 200 further reflects the incident radio wave signals and emits them via the correction member 204.

[0019] As shown in Figure 2A, the correcting member 204 is inclined by θ with respect to the z-axis and incident on each part of the main reflector 100, transmitting the radio wave signals reflected by each part of the main reflector 100 and guiding them to each part of the reflecting surface of the reflector 202. The correcting member 204 also transmits the radio wave signals reflected by each part of the reflecting surface of the reflector 202. The correcting member 204 ensures that the path length of the radio wave signal from the reference wavefront to the subfocus SF is equal to a constant length while transmitting radio wave signals incident on each part of the reflecting surface of the reflector 202 and while transmitting radio wave signals reflected from each part of the reflecting surface of the reflector 202, so as to prevent phase difference. The reference wavefront can be defined as a plane perpendicular to the direction of propagation of the radio wave signal, containing a reference point at a predetermined position that provides a reference for the wavefront of the radio wave signal. The correcting member 204 is, for example, a transparent film that functions as a metasurface, transmitting radio wave signals and changing their direction of propagation or path length to a direction desired by the user, such as the designer and operator of the parabolic antenna 20.

[0020] Figure 2C illustrates an example of the path of a radio wave signal when the sub-reflector 200 is composed only of the reflector 202 and no corrective member 204 is provided on the reflective surface of the reflector 202. Radio waves that are incident on the main reflector 100 of the parabolic antenna 20 at an angle θ with respect to the z-axis and reflected may not be focused to the sub-focus SF without the corrective member 204, even if they are further reflected by the reflector 202, which has a properly designed reflective surface shape. In such cases, it is necessary to design and form the shape of the reflective surface of the reflector 202 so that it reflects the radio wave signal and focuses it to the sub-focus SF, but designing and forming such a shape for the reflective surface of the reflector 202 is generally difficult.

[0021] On the other hand, the difference in path length and phase difference in the radio wave signal that is incident on the main reflector 100 of the parabolic antenna 20 at an angle of θ with respect to the z-axis and reflected can be compensated by appropriately designing, manufacturing, and attaching a corrective member 204, which is disposed on the reflective surface of the reflector 202 of the sub-reflector 200, to its shape, relative permittivity, and relative permeability. The design and manufacture of the shape, relative permittivity, and relative permeability of the corrective member 204 are generally easier than the design and formation of the shape of the reflective surface of the reflector 202. Details of the design method for the shape of the reflective surface of the reflector 202 of the sub-reflector 200 will be described later.

[0022] Figure 2A shows a center-type parabolic antenna 20 in which the primary focus MF and secondary focus SF are located on the primary reflector 100, but the configuration of the parabolic antenna 20 can be applied to an offset-type parabolic antenna. Figure 2D is a cross-sectional view of an example of a reflective multifocal offset parabolic antenna 22 according to the first embodiment of this disclosure.

[0023] As shown in Figure 2D, the parabolic antenna 22 comprises a main reflector 102 and a secondary reflector 200. The main reflector 102 has a reflective surface shaped like a section of its radiating surface. The main reflector 102 focuses radio wave signals incident parallel to the central axis of the parabolic surface of its reflective surface onto the main focus MF. The secondary reflector 200 receives radio waves at an angle θ with respect to the central axis of the parabolic surface of its reflective surface, reflects the radio wave signals reflected by each part of the main reflector 102's reflective surface, and focuses them onto the secondary focus SF.

[0024] For example, the parabolic antenna 20 shown in Figure 2A has a focal length p of 10m, an antenna diameter of 20m, coordinates of the secondary focal point SF are (2m, 0m, 10m), θ is 4°, the x-axis coordinate of reference point C (see Figure 9B, etc., described later) is -10m, and the distance (reference distance) d from the reference wavefront of the radio wave signal incident on the main reflector 100 to all positions on the main reflector 100 to the secondary reflector 200 to the secondary focal point SF is 10m. R (See Figure 9B, etc., below) is 16m.

[0025] As an example, the parabolic antenna 22 shown in Figure 2D has a focal length p of 16m, an antenna diameter of 18m, coordinates of the secondary focal point SF are (1m, 0m, 8m), θ is 4°, the x-axis coordinate of reference point C is -40m, and the reference distance d is from the reference wavefront of the radio wave signal incident on the main reflector 102 to all positions on the main reflector 102 to the secondary reflector 200 to the secondary focal point SF. R It is 55m.

[0026] [Second Embodiment] Next, a second embodiment of the present disclosure will be described. In the parabolic antennas 20 and 22 shown in the first embodiment above, the sub-reflector 200 is positioned further away from the main reflectors 100 and 102 than the sub-focus SF. However, even if the correcting member is positioned closer to the sub-reflector 200, similar to the parabolic antennas 20 and 22, radio wave signals incident parallel to the z-axis or the central axis of the parabolic surface of the reflecting surface can be focused to the main focus MF, and the path lengths of radio wave signals incident at an angle of θ with respect to the z-axis or the central axis of the parabolic surface of the reflecting surface can be made equal, and they can be focused to the sub-focus SF without phase difference.

[0027] Figure 3A is a cross-sectional view of an example of a transmissive multi-focus center type parabolic antenna 24 according to a second embodiment of the present disclosure. As shown in Figure 3A, the parabolic antenna 24 comprises a main reflector 100 and a transmission correction member 240 (second electromagnetic wave focusing member) positioned between the main reflector 100 and the secondary focus SF. The main reflector 100, similar to the main reflector 100 in the parabolic antenna 20, focuses radio wave signals incident along the z-axis to the main focus MF.

[0028] Furthermore, the main reflector 100 reflects the incident radio wave signal, which is tilted by θ with respect to the z-axis, onto the transmission-type transmission correction member 240. Similar to the correction member 204 shown in Figure 2B, the transmission correction member 240 transmits the radio wave signals reflected by each part of the main reflector 100, equalizing the path length and focusing them to the secondary focus SF without phase difference. In this way, by appropriately positioning the transmission correction member 240 between the main reflector 100 and the secondary focus SF, the path length and phase of the radio wave signal reflected by the main reflector 100 can be corrected and focused to the secondary focus SF.

[0029] Figure 3B illustrates an example of the configuration of the transmission correction member 240 shown in Figure 3A. As shown in Figure 3B, the transmission correction member 240 has a configuration in which a correction member 244 is attached to one surface of a support member 242. The transmission correction member 240 transmits the radio wave signals reflected by each part of the reflective surface of the main reflector 100, equalizes the path length, and focuses them at the secondary focus SF. In the support member 242, the shape of the surface to which the correction member 244 is attached, the relative permittivity and relative permeability of the element 260, and the arrangement position of the element 260 can be adjusted as described later with reference to Figure 7 and others.

[0030] Figure 3A shows a center-type parabolic antenna 24 in which the main focus MF and sub-focus SF are located on the main reflector 100, but the configuration of the parabolic antenna 24 can be applied to an offset-type parabolic antenna. Figure 3C is a cross-sectional view of an example of a transmission-type multi-focus offset parabolic antenna 26 according to a second embodiment of the present disclosure. As shown in Figure 3C, the parabolic antenna 26 comprises a main reflector 102 and a transmission correction member 240 disposed between the main reflector 102 and the sub-focus SF.

[0031] Similar to the main reflector 102 in the parabolic antenna 22, the main reflector 102 focuses radio wave signals incident parallel to the central axis of the parabolic surface of the main reflector 102's reflecting surface to the main focus MF. The main reflector 102 also reflects radio wave signals incident at an angle of θ with respect to the z-axis onto the transmission-type transmission correction member 240. The transmission correction member 240 transmits the radio wave signals reflected by the main reflector 102, equalizing the path length and focusing them to the secondary focus SF without phase difference.

[0032] In this way, by placing the transmission correction member 240 between the main reflector 102 and the secondary focus SF, the path length and phase of the radio wave signal reflected by the main reflector 102 can be corrected and focused to the secondary focus SF. Note that while the parabolic antenna 20 is a center-type multifocal parabolic antenna, the parabolic antenna 26 is an offset transmission-type multifocal parabolic antenna, so in the parabolic antenna 26, the transmission correction member 240 does not cause blocking between the reflective surface (parabolic reflector) of the main reflector 100 and the main focus MF.

[0033] For example, the parabolic antenna 24 shown in Figure 3A has a focal length p of 10m, an antenna diameter of 20m, coordinates of the secondary focal point SF are (2m, 0m, 10m), θ is 4°, the x-axis coordinate of reference point C (see Figure 9B, etc., described later) is -10m, and the distance d is from the reference wavefront to the main reflector 100 to the secondary reflector 200 to the secondary focal point SF. R (See Figure 9B, etc., below) is 10m.

[0034] As an example, the parabolic antenna 26 shown in Figure 3C has a focal length p of 10m, an antenna diameter of 18m, the coordinates of the secondary focal point SF are (2m, 0m, 10m), θ is 4°, the x-axis coordinate of the reference point C is -40m, and the distance d is from the reference wavefront to the main reflector 100 to the secondary reflector 200 to the secondary focal point SF. R It is 52m.

[0035] Next, a modified example of the parabolic antennas 20, 22, 24, and 26 (Figures 2A and 3A) shown in the first and second embodiments will be described. Figure 4A illustrates a modified example of the reflective multi-focus center type parabolic antenna shown in Figure 2A. Figure 4B illustrates a modified example of the transmissive multi-focus center type parabolic antenna shown in Figure 3A. Figure 4C illustrates modified examples of the reflective multi-focus center type parabolic antenna and the transmissive multi-focus center type parabolic antenna shown in Figures 2A and 3A.

[0036] More generally, the parabolic antenna 32 consists of a main reflector 100 that focuses radio wave signals incident parallel to the z-axis to the main focus MF, and a mirror with θ1~θ relative to the z-axis. m The parabolic antenna 32 includes sub-reflectors 200-1 to 200-m that reflect radio waves incident at an angle of (m is an integer greater than or equal to 1) and the radio waves reflected at each position of the main reflector 100, and focus them at sub-focuses SF1 to SFm, respectively. With these components, the parabolic antenna 32 focuses radio waves incident parallel to the z-axis and with respect to the z-axis θ1 to θ m Each incoming radio signal, tilted to a specific angle, can be focused to the primary focus (MF) and secondary focuses (SF1-SFm), respectively.

[0037] As shown in Figure 4B, the parabolic antenna 32 comprises a main reflector 100 and transmission correction members 240-1 and 240-2 that transmit radio wave signals tilted by θ1 and θ2 with respect to the z-axis, respectively, and focus them at the secondary focal points SF1 and SF2, respectively. More generally, the parabolic antenna 32 comprises a main reflector 100 that focuses radio wave signals incident parallel to the z-axis to the main focal point MF, and a transmission correction member 240-1 and 240-2 that transmit radio wave signals tilted by θ1 to θ2 with respect to the z-axis, respectively. mIt includes transmission correction members 240-1 to 240-m that only incident obliquely and transmit the radio wave signals reflected by each part of the main reflector 100 and focus them on the sub-foci SF1 to SFm. The parabolic antenna 32, with these components, focuses the radio wave signals parallel to the z-axis and those incident obliquely at angles θ1 to θ m Each of the radio wave signals incident obliquely is focused on each of the sub-foci SF1 to SFm.

[0038] As shown in FIG. 4C, the parabolic antenna 34 includes a main reflector 100 that focuses the radio wave signal incident parallel to the z-axis on the main focus MF, a transmission correction member 240 that transmits the radio wave signal incident obliquely at an angle θ1 with respect to the z-axis and focuses it on the sub-focus SF1, and a sub-reflector 200 that transmits the radio wave signal incident obliquely at an angle θ2 with respect to the z-axis and focuses it on the sub-focus SF2. With these components, the parabolic antenna 34 can focus the radio wave signal incident parallel to the z-axis and the radio wave signals incident obliquely at angles θ1 and θ2 on the main focus MF and the sub-foci SF1 and SF2, respectively. As shown in FIG. 4C, one or more sub-reflectors 200 and one or more transmission correction members 240 can be mixed in one multi-focus parabolic antenna.

[0039] FIGS. 5A and 5B, FIG. 5A is a diagram illustrating a modified example of the parabolic antennas 20 and 24 (FIGS. 2A and 2B) using a transmission correction member 240 instead of the main reflector 100. As shown in FIG. 5A, the transmissive multi-focus center-type parabolic antenna 36 includes a transmission correction member 240-1 (the first electromagnetic wave focusing member) that transmits the radio wave signal incident parallel to the z-axis and focuses it on the main focus MF, and a transmission correction member 240-2 (the second electromagnetic wave focusing member) that incident obliquely at an angle θ with respect to the z-axis and transmits the radio wave signal that has passed through the transmission correction member 240-1 and focuses it on the sub-focus SF. With these components, the parabolic antenna 36 focuses the radio wave signal incident parallel to the z-axis on the main focus MF and the radio wave signal incident obliquely at an angle θ with respect to the z-axis on the sub-focus SF.

[0040] As shown in Figure 5B, the transmissive multi-focus center-type parabolic antenna 38 includes a transmission correction member 240 that transmits radio wave signals incident parallel to the z-axis and focuses them at the primary focus MF, and a sub-reflector 200 that reflects radio wave signals incident at an angle of θ with respect to the z-axis, which have passed through the transmission correction member 240, and focuses them at the secondary focus SF. With these components, the parabolic antenna 36 can focus radio wave signals incident parallel to the z-axis at the primary focus MF, and radio wave signals incident at an angle of θ with respect to the z-axis at the secondary focus SF. Although Figures 4A, 4B, 4C, 5A, and 5B show center-type parabolic antennas 30, 32, 34, 36, and 38, it will be obvious to those skilled in the art that these can be further modified into offset-type parabolic antennas.

[0041] According to the parabolic antennas 30, 32, 34, 36, and 38 described above, the radio wave signal incident parallel to the z-axis and the radio wave signal incident at an angle of θ with respect to the z-axis are separated when reflected by the main reflector 100. The radio wave signal incident parallel to the z-axis is focused at the main focus MF, and the radio wave signal incident at an angle of θ with respect to the z-axis is focused at the secondary focus SF via the reflective surface of the reflector 202 of the secondary reflector 200 or the surface of the support member 242 of the transmission correction member 240. Therefore, with the parabolic antennas 30, 32, 34, 36, and 38, as in array antennas, the synthesis or separation of radio wave signals is not required, and thus no loss occurs in the radio wave signal.

[0042] As will be described later with reference to Figure 6A, the reflective surface of the mirror 202 of the sub-reflector 200, or one or both of the two surfaces of the support member 242 of the transmission correction member 240, on which a large number of elements 206 are arranged, is referred to as the "correction surface." In other words, the transmission correction member 204 is composed of a large number of elements 206 arranged on one or both sides of the reflective surface of the mirror 202 of the sub-reflector 200, which is designated as the correction surface, or on one or both sides of the support member 242 of the transmission correction member 240, which is designated as the correction surface.

[0043] Although the correction surface actually takes on a three-dimensional shape, to facilitate understanding of the design method for a three-dimensional correction surface, the correction surface may first be represented by a two-dimensional curve of the cross-section passing through its center. In such cases, the position of the element 206 placed on the correction surface can be defined only by the x-coordinate, with the yz axis omitted from the xyz coordinate system.

[0044] Furthermore, the gain obtained by the main reflector 100 focusing the radio wave signal incident along the central axis of its parabolic surface to the main focus MF is approximately the same as the gain obtained by the main reflector 100 reflecting the radio wave signal tilted by θ with respect to the central axis of its parabolic surface, and further focusing it to the secondary focus SF by the secondary reflector 200 or the transmission correction member 240. Also, since any number of secondary focuses SF can be set in a single parabolic antenna, any number of sub-beams can be obtained in a single parabolic antenna.

[0045] [Design method for the configuration of sub-reflectors and corrective members, and the shape of the corrective surface] Next, the configuration of the sub-reflector 200 and transmission correction member 240 shown in Figures 2B and 3A, and the design method for the shape of the correction surface will be explained in detail. First, the configuration of the correction members 204 and 244 will be explained. Figure 6A is a diagram illustrating one configuration of the correction members 204 and 244 shown in Figures 2B and 3B. Although Figure 6A appears to show a correction member 204 or 244 having a large number of elements 206 arranged at equal intervals on a flat correction surface, in reality, the correction surface is curved.

[0046] As shown in Figure 6A, on the correction surface of the reflecting mirror 202 of the sub-reflecting mirror 200 or the support member 242 of the transmission correction member 240, a number of elements 206 are arranged in a matrix along the x and y axes and attached to the correction surface by adhesive or the like. The length of each side of the element 206 is a known value of λ / 2 or less, as explained with reference to Figure 6A, and the spacing between the elements 206 is a known value of λ / 2 to λ / 4. Therefore, for example, when a number of elements 206 are arranged at equal intervals parallel to the x and y coordinates, the position of each of the number of elements 206 can be defined by a two-dimensional arrangement on the correction surface, such as (0,0), (1,0),..., (i-1,j), (i,j-1), (i,j),..., (i+1,j), (i,j+1),..., etc., regardless of their position on the x,y, and z coordinates. Therefore, the element 206 at position (i,j) in the two-dimensional arrangement is element 206 in the drawing. i,j It is also written as follows.

[0047] The correction surface and the numerous elements 206 attached to the correction surface constitute correction members 204 and 244. Correction member 204 is tilted by θ with respect to the z-axis (Figure 2A, etc.) and incident on each part of the reflective surface of the main reflector 100, reflecting the radio waves, and equalizing the path length of the radio waves reflected by each part of the reflector 202 of the sub-reflector 200, eliminating the phase difference and focusing them at the sub-focus SF. Similarly, correction member 244 is tilted by θ with respect to the z-axis and incident on each part of the reflective surface of the main reflector 100, reflecting the radio waves, and equalizing the path length of the radio waves that have passed through each part of the support member 242 of the transmission correction member 240, eliminating the phase difference and focusing them at the sub-focus SF.

[0048] Referring to Figures 6B and 6C, the arrangement of the elements 206 mounted on the correction surface as shown in Figure 6A will be further explained. Figure 6B shows the arrangement patterns of adjacent elements that should be considered when calculating the path length corresponding to the amount of phase change to be given to a single element. Figure 6C shows the elements 206 arranged as shown in Figure 6A. xy Of the three adjacent ones, the 206 i,j ,206 i-1,j ,206 i,j-1 The physical distance d between them i d jThis is a diagram illustrating an example.

[0049] Element 206 i-1,j and elements206 i,j-1 Using the amount of phase change of the radio wave signal passing through element 206 i,j The amount of phase change to be applied to the radio wave signal passing through is calculated. Specifically, for example, as shown in Figure 6B labeled (1), element 206 i,j It is located at the left end of the matrix, and as shown by the dotted line, it is adjacent to element 206 on both the left and above. i-1,j ,206 i,j-1 If there is no element 206 i,j The amount of phase change in the radio signal passing through is 0(l φi,j It is assumed that = 0). Also, as shown in Figure 6B with (2) attached, element 206 i,j Element 206 is shown on the left side by a solid line. i-1,j However, as shown by the dotted line, element 206 is located on the upper side. i,j-1 When it does not exist, element 206 i,j-1 The change in path length of the radio signal passing through, i.e., the amount of phase change, is set to 0. Element 206 i-1,j Using the amount of phase change of the radio wave signal passing through element 206 i,j The phase change that should be imparted to the radio signal can be calculated.

[0050] Furthermore, as shown in Figure 6B with (3) attached, element 206 i,j Element 206 is shown by a solid line above it. i,j-1 There is an element 206 on the left side, as indicated by the dotted line. i-1,j When it does not exist, element 206 i-1,j The amount of phase change of the radio signal passing through is set to 0. Element 206 i,j-1 Using the amount of phase change of the radio wave signal passing through element 206 i,j The amount of phase change that should be imparted to the radio signal can be calculated.

[0051] Furthermore, as shown in Figure 6B with (4) attached, element 206 i,j Element 206 is also located on the left and top sides. i-1,j ,206 i,j-1 When there is element 206 i-1,j and elements206i,j-1 Using the amount of phase change of the radio wave signal passing through element 206 i,j The amount of phase change that should be imparted to the radio signal can be calculated. In the example shown in Figure 6A, a certain element 206 i,j Element 206 adjacent to it in an oblique direction i-1,j-1 The phase change of the radio signal passing through these elements is due to element 206 i,j It is not used in the calculations, under the assumption that it does not affect the amount of phase change in the radio signal passing through it. Element 206 i,j It is not calculated based on the amount of change in motion that it imposes on the radio signal passing through it.

[0052] As explained with reference to Figure 6B, first, element 206 is located on both the left and upper sides. i-1、j ,206 i,j-1 Element 206 does not exist i,j The amount of phase change imparted to the radio signal passing through is assumed to be 0. Next, as shown in Figure 6B, element 206 is placed on the left or upper side. i-1,j ,206 i,j-1 Element 206 i,j This is selected. From the reference wavefront, element 206 i-1,j The path length to L x And element 206 i,j-1 The path length to L y And element 206 i,j Point B on the correction plane where the object is located. i Vector B from the secondary focus SF i The projection vector of F onto the xz plane is vector B. i F xz Let vector B i The projection vector of F onto the yz plane is vector B. i F yz Therefore, element206 i,j and elements206 i-1,j The phase gradient angle γ between i Element 206 i,j and elements206 i,j-1 The phase gradient angle γ between j , can be calculated. Using these values, element 206 i,j The amount of phase change that should be imparted to the radio signal passing through can be calculated.

[0053] Figure 6D illustrates one configuration of the element 206 shown in Figure 6A. Figure 6E illustrates an example of the shape of the resonator shown in Figure 6D. Figure 6F is a graph showing the frequency-to-effective relative permeability characteristics of the element 206 shown in Figure 6D. Figure 6G is a schematic diagram showing an example of a split-ring resonator. As shown in Figure 6D, the element 206 has a configuration in which resonators 210-1 and 201-2 are attached to both the front surface of the rectangular dielectric plate 208 and the back surface that is in contact with the reflector 202 or the support member 242.

[0054] The material of element 206 is, for example, plastic or ceramic, and element 206 is also called a meta-atom. Since resonators 210-1 and 201-2 need to be conductive, the material of resonators 210-1 and 201-2 is, for example, a metal or a composite material of metals such as Au, Ag, Al, Si, SiO2, Si3N4, GaN, or TiO2. When referring to a component without specifying one of several possible components, such as "resonator 210" or "resonator 210-2", the subscript may be omitted and the component may be written as "resonator 210".

[0055] The resonator 210 has the shape shown in Figure 6D, and as shown in Figure 6E, the resonant frequency of element 206 is set by adjusting the division interval, and as shown in Figure 6F, the relative permeability of element 206 changes significantly on both the positive and negative sides near the resonant frequency. On the other hand, the relative permittivity of element 206 near the resonant frequency hardly changes from the time of manufacture. Thus, by adjusting the division interval of the resonator, the relative permeability of element 206 at a specific frequency can be set not only to a positive value but also to a negative value. On the other hand, the relative permittivity of dielectric plate 208 is a positive value, but if a metal plate is used instead of dielectric plate 208, the relative permittivity of element 206 can be easily set to a negative value. Furthermore, the relative permittivity of dielectric plate 208 can be changed by changing the material of dielectric plate 208, adjusting the spacing between dielectric plates 208, or either of these.

[0056] Furthermore, a negative relative permittivity can be obtained not only by replacing the dielectric plate 208 with a metal plate, but also by arranging multiple dielectrics aligned in a certain direction on the dielectric plate 208. In addition, a negative relative permeability can be obtained not only by using the dielectric plate 208 with the configuration shown in Figure 6D, but also by using a magnetic material called a split-ring resonator, which consists of a resonator and a metal wire, as illustrated in Figure 6G.

[0057] Let's explain in more detail. The refractive index n for a radio wave signal of frequency ω is given by equation 1 below, where ε(ω) is the relative permittivity and μ(ω) is the relative permittivity.

[0058]

number

[0059] Furthermore, when both the relative permittivity ε(ω) and μ(ω) are negative values, the refractive index n is given by the following equation 2.

[0060]

number

[0061] As described above, a negative relative permittivity can be easily obtained by replacing the dielectric plate 208 with a metal plate. Therefore, if a negative relative permeability is obtained as shown in Figure 6F, the refractive index of element 206 can be set to a wide range from positive to negative values.

[0062] Figure 6H illustrates an example of the wavefront of a radio wave signal generated by multiple elements 206, each with an adjusted refractive index. When the refractive index of the radio wave signal of each of the multiple elements 206 is appropriately set, the propagation speed of the radio wave signal in each of the multiple elements 206 is appropriately set, and a change in the phase of the radio wave signal occurs in accordance with the change in the propagation speed of the radio wave signal in each of the multiple elements 206.

[0063] Furthermore, according to Huygens' principle, as will be described later with reference to equations 23 and 24 below, a phase gradient γ is applied to the radio wave signal that has passed through multiple elements 206.i γ j This occurs, and the direction of propagation of the radio wave signal changes. In this way, by appropriately setting the side length of each of the numerous elements 206 and the division interval of the resonator 210, the phase change (refractive index) of each of the numerous elements 206 can be set over a wide range. Furthermore, this allows the reflection direction and refraction direction of the sub-reflector 200 and the correction member 204 to be set over a wide range. As described above, the correction members 204 and 244 of the sub-reflector 200 and the transmission correction member 240 function as metasurfaces.

[0064] As explained above, the sub-reflector 200, equipped with a correction member 204 that functions as a metasurface, compensates for the path length and phase of radio wave signals incident on the parabolic antennas 20 and 22 at an angle of θ with respect to the z-axis as shown in Figures 2A and 3A, and focuses them at the sub-focus SF. Similarly, the transmission correction member 240, equipped with a correction member 244 that functions as a metasurface, compensates for the path length and phase of radio wave signals incident on the parabolic antennas 24 and 26 (Figures 3A and 3C) at an angle of θ with respect to the symmetry axis of the parabolic surface of the reflecting surface of the main reflector 100, and focuses such radio wave signals at the sub-focus SF.

[0065] Next, the design of the correction members 204 and 244 will be explained. Figure 7 is a flowchart that schematically illustrates one method for designing the reflective surface of the reflector 202 of the sub-reflector 200 or the correction surface of the support member 242 of the transmission correction member 240, as shown in Figures 2B and 3C, and for setting the relative permittivity and relative permeability of each of the numerous elements 206. As shown in Figure 7, in S100, the focal length p, the diameter 2r of the main reflector 100 (where r is a positive real number), and the inclination θ (°) of the radio wave signal with respect to the z axis are set as parameters for deriving the shape of the correction surface.

[0066] The inclination θ can be defined, for example, as the angle taken with respect to the central axis of the parabolic surface of the main reflector 100 when the radio wave signal focused at the secondary focus SF is incident on the main reflector 100. Therefore, if the central axis of the parabolic surface of the main reflector 100 is parallel to the z-axis, the inclination θ can be defined as the angle with respect to the z-axis in the direction of propagation of the radio wave signal incident on the main reflector, as explained with reference to Figure 6A.

[0067] Furthermore, the positions of each part of the reflective surface of the main reflector 100, the reflective surface of the reflector 202 of the correction member 204, or the correction surface of the support member 242 of the transmission correction member 240 can be defined by mutually orthogonal xyz coordinate systems. In Figure 9A and other figures, the center of the circular main reflector 100 xyz coordinate system is set as the origin of the coordinate system (O; (x,y,z)=(0,0,0)), and a specific example is the case where the z-axis is parallel to the central axis of the reflective surface (parabolic surface) of the main reflector 100. Also, the coordinates of the main focus MF(P) are (0,0,p), and the position of the secondary focus SF is (x in xyz coordinate system). F ,y F ,z F ) is defined as follows.

[0068] In S102, the shape of the correction surface is derived. Details of the process in S102 for deriving the curve of the two-dimensional cross-section of the correction surface will be described later with reference to Figures 9A, 9B, and 10A to 10E.

[0069] In S104, a number of elements 206 are placed at predetermined positions on the correction surface whose shape has been derived, as shown in Figure 6A. xy Assume that the elements are positioned and mounted. A number of elements 206 are assumed to be mounted on the correction surface in this manner. xy The path length of the radio signal passing through each is calculated. Element 206 xy Details of how to calculate the path length of the radio signal passing through each path, and the difference in path length between them, will be described later with reference to Figures 6B, 6C, and 11A to 11E.

[0070] In S106, a number of elements 206 are present on the correction surface. x,yIt is determined whether all the path lengths of the radio signals passing through the assumed location where the device is installed are equal. If all the path lengths of the radio signals are equal (Y in the process of S106), the process of S112 is executed; if there is a difference in the path lengths of the radio signals (N in the same process), the process of S108 is executed.

[0071] In S108, for example, element 206 through which radio signals with different path lengths pass. x,y When at least one of these is included, the optimal shape of the correction surface is searched for using the bisection method. Note that the search for the optimal shape of the correction surface using the bisection method may be performed in the column direction or the row direction of the array of elements 206x,y, or it may be performed in any direction regardless of the column and row directions. The process in S108 will be described later with reference to Figure 12A. In S110, the shape of the correction surface is modified. Note that the details of the process in S110 will be described later with reference to Figures 6B, 6C, 9A, 9B, 10A to 10E, and 11A to 11E. The result of the correction of the shape of the correction surface by the process in S110 will be described later with reference to Figures 12B and 12C. After the process in S110, the process in S106 is executed.

[0072] In S112, a number of elements 206 x,y The path length of the radio signal passing through each is the reference distance d. R A large number of elements 206 x,y At least one of the relative permittivity and relative permeability is set for each element. A number of elements 206 with at least one of the relative permittivity and relative permeability set. x,y Each of them is attached to a predetermined position on the correction surface, as shown in Figure 6A.

[0073] Figure 8 is a schematic diagram illustrating one hardware configuration of the arithmetic processing unit 5 that performs the processing shown in Figure 7. The processing shown in the flowchart in Figure 7 can be performed, for example, by the arithmetic processing unit 5 illustrated in Figure 8 or by a general computer. As shown in Figure 8, the arithmetic processing unit 5 includes one or more CPUs (Central Processing Units; processors) 500, a main memory 502, an auxiliary memory 504, and an interface (IF; Interface) circuit 506 that are connected to each other via a bus or the like to enable data input and output.

[0074] The CPU 500 may be further equipped with CPU peripheral circuits such as timer circuits and DSP (Digital Signal Processor; not shown), as appropriate, to include components necessary for executing the processes shown in Figure 7. Furthermore, the auxiliary storage device 504 may be used by the arithmetic processing unit 5 for purposes such as updating the program (software) required for the processes shown in Figure 7, but may be removed from the arithmetic processing unit 5 as appropriate when it is no longer needed, such as after the program update is complete.

[0075] The interface circuit 506 accepts user input from a keyboard or other input device to the arithmetic processing unit 5 and outputs input data indicating the accepted operation to the CPU 500. The interface circuit 506 also outputs output data showing the arrangement of elements 206 on the correction surface obtained as a result of the processing shown in Figure 7 by the CPU 500 via an output device such as a display, and shows it to the user of the arithmetic processing unit 5.

[0076] The main memory 502 includes memory elements such as RAM (Random Access Memory; not shown) and ROM, and stores programs that implement the processing shown in Figure 7 executed by the CPU 500, as well as data required for their execution. The auxiliary memory 504 includes non-volatile memory devices such as flash memory, and, similar to the main memory 502, stores programs that are executed by the CPU 500, as well as data required for their execution. The programs executed by the CPU 500 can be recorded on a non-transitory computer-readable storage medium such as flash memory and provided to the arithmetic processing unit 5.

[0077] In S102 shown in Figure 7, the process of deriving the cross-sectional shape of the correction surface in a two-dimensional plane will be explained in detail with reference to Figures 9A and 9B. In Figure 9B, a specific example is the derivation of a correction surface that focuses the radio wave signal, which is incident at an angle of θ with respect to the z-axis and reflected by the main reflector 100, onto the secondary focus SF. However, it will be obvious to those skilled in the art that this specific example can be applied to the correction surface of the support member 242 of the transmission correction member 240 of the parabolic antenna 24 shown in Figure 3A. Furthermore, the details of the process of deriving the shape of the correction surface in a three-dimensional curved surface will be described later with reference to Figures 10A to 10E.

[0078] Figure 9A illustrates the cross-section of the main reflector 100, points A and A' moving on the cross-section of the main reflector 100, the reference point C located on the most negative side of the x-axis in the cross-section of the main reflector 100, the intersection points D and D' of the radio wave signal passing through point A and the reference wavefront, the main focus MF, the secondary focus SF, and the position of the reference wavefront of the radio wave signal passing through point C. Figure 9B illustrates points A, B, reference point C, and secondary focus SF used to derive the shape of the correction surface in a two-dimensional plane.

[0079] First, to derive the shape of the correction surface in a two-dimensional plane, for example, the xz plane, we have the focal length p, the diameter of the primary reflector 100 2r (where r is a positive real number), and the coordinates (x) of the secondary focus SF in the xz plane.F , z F ), and the inclination θ (°) of the radio wave signal is set. Also, for example, the line indicating θ is inclined to the left with respect to the z-axis, and in the cross-section of the main reflector 100 on the x-axis, the point where the value of the x-coordinate becomes the largest on the negative side is defined as the reference point C. In such a case, the coordinates of the reference point C in the xz plane are (-r, r 2 / 4p). However, the reference point C does not necessarily have to be located at the end of the cross-section of the reflecting surface of the main reflector 100, and can be at any position on the parabolic surface including the reflecting surface of the main reflector 100. Therefore, the position of the reference point C on the x-axis is arbitrary, but the value of the coordinate of the reference point C on the x-axis becomes a negative value when θ is inclined to the left as shown in FIG. 9B, etc., and becomes a positive value when θ is inclined to the right. Also, the line indicating the inclination θ of the radio wave signal with respect to the z-axis does not necessarily have to be inclined to the left with respect to the z-axis, and may be inclined to the right or left with respect to the z-axis depending on the positional relationship between the main reflector 100 and the sub-focus SF.

[0080] Furthermore, as shown in FIG. 9B, the intersection of the line passing through the reference point C and inclined by θ with respect to the y-axis and the line passing through the point A (coordinates (x A , x A 2 / 4p)) moving on the cross-section of the reflecting surface of the main reflector 100 and inclined by θ to the left with respect to the z-axis is defined as the point D. The line passing through the reference point C and inclined by θ with respect to the x-axis is perpendicular to the traveling direction of the radio wave signal that is inclined by θ with respect to the z-axis and incident on the main reflector 100. Among the wave surfaces perpendicular to the traveling direction of the radio wave signal, the wave surface that is perpendicular to the traveling direction of the radio wave signal and includes the reference point C is defined as the reference wave surface.

[0081] For convenience of description, when the sub-focus SF is the end point of the line segment, the sub-focus SF is simply denoted as F. When the reference distance d R is longer than the line segment CF (d R > CF), a reflective multi-focus parabolic antenna using a sub-reflector 200 as shown in FIG. 2A, etc., is adopted. Also, when the reference distance d R is shorter than the line segment CF (CF > d R) As shown in FIG. 3A etc., a transmissive multi-focus parabolic antenna using a transmissive correction member 240 is employed.

[0082] Here, the path lengths of the radio wave signals that are reflected at each position on the reflecting surface of the main reflector 100, pass through the correction member 204, are further reflected by the reflector 202, pass through the correction member 204 again, and reach the sub-focus SF must all be equal to a certain length regardless of at which position on the reflecting surface of the main reflector 100 they are reflected. Similarly, the path lengths of the radio wave signals that are reflected at each position on the reflecting surface of the main reflector 100, pass through the support member 242 and the correction member 244 of the transmissive correction member 240, and reach the sub-focus SF must all be equal to a certain length regardless of at which position on the reflecting surface of the main reflector 100 they are reflected. Therefore, if an arbitrary point on the curved surface of the correction surface is defined as point B, the line segment DABF and the reference distance d R must always be equal (line segment DABF = reference distance d R ). Therefore, when point A moves over all of the cross-section of the reflecting surface of the main reflector 100, the set of points B that gives line segment DABF = reference distance d R gives the curved surface of the correction surface.

[0083] First, tanα is given by Equation 3 below.

[0084]

Equation

[0085] DA + AB + BF = d R Subtracting DF from both sides of this equation gives AB + BF = d R - DA. To obtain the x-coordinate x B of point B, it is necessary to express AB and BF using x B . DA is given by Equation 4 below, and the coordinate z B of point B's coordinates (x B , z B ) is given by Equation 5 below, AB is given by Equation 6 below, and BF is given by Equation 7 below.

[0086]

number

[0087]

number

[0088]

number

[0089]

number

[0090] Therefore, d R -DA is expressed by equation 8 below.

[0091]

number

[0092] Squaring both sides of equation 8 to remove the square root yields equation 9 below.

[0093]

number

[0094] Replace 7 in the above equation with x B Solving for , we obtain equation 10 below.

[0095]

number

[0096] Equations 9 and 10 above are based on the characteristic that the path length of the radio wave signal from the reference wavefront to the sub-focus SF is kept constant, and that the direction of propagation of the radio wave signal is changed by the numerous elements 206 arranged in the reflector 202 of the sub-reflector 200 or the support member 242 of the transmission correction member 240. However, equations 9 and 10 above do not take into account the error in path length that occurs when the radio wave signal passes through each of the numerous elements 206, i.e., the phase error. The amount of path length error that each of the numerous elements 206 imparts to the radio wave signal needs to be calculated after the change in the angle of the direction of propagation of the radio wave signal is calculated using equations 9 and 10 above.

[0097] In other words, the path length of the radio signal passing through each of the numerous elements 206 is no longer constant, so it is necessary to calculate the path length error that each of the numerous elements 206 imparts to the radio signal. Therefore, rather than correcting either the position or characteristics (relative permittivity and relative permeability) of each of the numerous elements 206 on the correction surface based on the calculation result of the phase error that each of the numerous elements 206 imparts to the radio signal, the position of each of the numerous elements 206 on the correction surface is recalculated so that the path length of the radio signal passing through each of the numerous elements 206 becomes constant, taking the phase error into consideration.

[0098] In equation 10 above, since cos(α-θ)>0, x B -x A When x = 0, that is, when the slope of the reflected wave from point A to point B is 0°, we need to differentiate between cases based on this. B -x A When = 0, tan(α-θ) = 0, so when tan(α-θ) ≥ 0, the above equation 10 becomes the lower equation 11, and when 0 > tan(α-θ), the above equation 10 becomes the lower equation 12.

[0099]

number

[0100]

number

[0101] As shown in Figure 9A, etc., a radio wave signal with a two-dimensional planar wavefront (plane wave) is incident on the reference wavefront of the main reflector 100 of the parabolic antennas 20, 24 (Figures 2A, 3A). On the other hand, when the incident radio wave signal is reflected by the reflecting surface of the main reflector 100, the wavefront of the radio wave signal becomes a three-dimensional curved surface and is incident as a curved wave on the correction surface of the sub-reflector 200 or the transmission correction member 240. The radio wave signal reflected by the correction surface of the sub-reflector 200, or the radio wave signal that has passed through the correction surface of the transmission correction member 240, is also a curved wave, and the curved wave is focused at the sub-focus SF.

[0102] On the other hand, when calculating the change in path length that multiple elements 206 should impart to the incident radio wave signal, that is, the phase change of the radio wave signal, a model is generally used in which the elements 206 are arranged on a plane, as shown in Figure 6H, for example, in a phased array antenna. In other words, generally, in order to calculate the change in path length that multiple elements 206 should impart to the incident radio wave signal, a model is used that is as if the correction surface were a plane, and a plane wave radio wave signal were incident on multiple elements 206 arranged on the plane correction surface.

[0103] However, as mentioned above, in reality, the radio wave signal is incident on the curved surface of the correction surface. Therefore, it is necessary to calculate the path length of the radio wave signal incident as a curved wave in a two-dimensional model of the cross-section between the main reflector 100 and the correction surface of the sub-reflector 200 or the transmission correction member 240. Furthermore, in a three-dimensional model of the correction surface of the main reflector 100 and the sub-reflector 200 or the transmission correction member 240, which actually have a three-dimensional shape, it is naturally necessary to calculate the path length of the radio wave signal incident as a curved wave.

[0104] Next, assuming the process of deriving the shape of the correction surface in a two-dimensional plane as explained with reference to Figures 9A and 9B, the process of deriving the shape of the correction surface in three-dimensional space will be explained in detail with reference to Figures 10A to 10E. Figure 10A is a diagram illustrating an example of a radio wave signal incident on point A on the reflective surface of the main reflector 100 and reflected.

[0105] Furthermore, for the sake of clarity in the specification, a vector connecting, for example, point A to the origin of the coordinate system O will be referred to as vector OA. T For example, the subscript T of a vector indicates that a column vector is written in the form of a row vector. Figure 10B shows an arbitrary point A(x) on the main reflector 100 of a parabolic antenna 20 (Figure 2A). A ,y A ,z A (=(x A 2 +y A 2 ) / p)), principal focus MF(x P (=0), y P (=0), z P (=p)), subfocal SF(x F ,y F (=0), z F )) and point B(x) on the correction plane corresponding to point A B ,y B ,z B This diagram illustrates an example of the position of the ) ). However, for the sake of simplicity in notation of mathematical formulas, the primary focus MF is sometimes simply referred to as P.

[0106] In three-dimensional space, point B on the correction surface can be defined using vectors, similar to the approach used in a two-dimensional plane. First, the vector of the radio wave signal reflected by the reflective surface of the main reflector 100 (reflected wave vector) is calculated. At any point A on the main reflector 100, a radio wave signal tilted by θ with respect to the z-axis (vector OP) is incident. Therefore, the reflected wave vector indicating the direction of the radio wave signal from any point A on the main reflector 100 to point B on the correction surface is the vector obtained by rotating the radio wave signal vector from point A to the main focus MF (vector AP) by θ around the y-axis when a radio wave signal parallel to the central axis of the antenna is incident at point A. As shown in Figures 10A and 10B, vector OP is (0,0,p) (vector OP=(0,0,p); p is the focal length), vector y indicating the direction of the coordinate axis y is (0,1,0) (y=(0,1,0)), and vector OA is (x A ,y A ,zA ) is (vector OA = (x A ,y A ,z A );z A =(x A 2 +y A 2 ) / 4p). According to Rodrigues' rotation formula, the vector AB of the reflected wave is given by equations 13 and 14 below.

[0107]

number

[0108]

number

[0109] Therefore, vector AB is given by equation 15 below, and vector OB is given by equation 16 below, where t is a real number in equation 16.

[0110]

number

[0111]

number

[0112] Next, the path length from when the radio wave signal incident on the main reflector 100 at an angle of θ with respect to the z-axis passes through the reference wavefront until it reaches the reflecting surface of the main reflector 100 is calculated. FIG. 10C is a perspective view illustrating the reference wavefront and the normal vector w of the reference wavefront of the radio wave signal incident on the reflecting surface of the main reflector 100 at an angle of θ with respect to the z-axis. Note that the reference wavefront shown in FIG. 10C is inclined such that the negative side of the x coordinate (the reference point C side) is closer to the xy plane and the positive side of the x coordinate is farther from the xy plane. Therefore, the normal vector w of the reference wavefront is inclined θ degrees to the left with respect to the direction parallel to the z-axis as shown by the dotted line in FIG. 10C. When the traveling direction of the radio wave signal incident on the main reflector 100 at an angle of θ with respect to the z-axis is taken as the incident wave vector, the incident wave vector and the normal vector w of the reference wavefront are parallel, and the normal vector w is given by, for example, the following equations 17 and 18.

[0113]

Number

[0114]

Number

[0115] The coordinates of the reference point C outside the cross-section of the reflecting surface of the main reflector 100 are (x C , y C , z C ), and since the normal vector w = (-sinθ, 0, -cosθ) T , the reference wavefront passing through the reference point C is given by the following equation 19.

[0116]

Number

[0117] The coordinates of a point A at an arbitrary position on the cross-section of the main reflector 100 shown in FIG. 10C are (x A , y A , z AAssuming this is the case, the length of the line segment DA of the radio wave signal that is incident on the main reflector 100 at an angle of θ with respect to the z axis, from the time it passes the reference wavefront to point A, is given by equation 20 below, based on equation 19 above.

[0118]

number

[0119] Also, from point A, the secondary focus SF (coordinate (x F ,y F ,z F The vector AB up to )) is given by equation 21 below.

[0120]

number

[0121] Next, we derive a point on the correction plane. The length of line segment DA is d. R The vector OB'' from the origin O of the coordinate axes to point B'' on the correction plane (the `` indicates that this is different from point B shown in Figure 9B, etc.) is given by equation 24. Also, the sum of line segments DA, AB, and BF is equal to the reference distance dR as shown in equation 22 below, so the variable t in equation 16 is given by equation 23 below.

[0122]

number

[0123]

number

[0124] Next, the position of point B on the sub-reflector surface when a radio wave signal inclined by θ with respect to the z-axis and inclined by ψ (°) with respect to the x-axis is incident on the main reflector 100 is calculated. FIG. 10D is a diagram illustrating a radio wave signal that is inclined by θ with respect to the z-axis and inclined by ψ (where rotation in the positive y-axis direction is positive) with respect to the x-axis and is incident on the main reflector 100. FIG. 10E is a plan view of FIG. 10D as viewed from the positive side to the negative side of the z-axis. When a radio wave signal inclined by θ with respect to the z-axis and inclined by ψ with respect to the x-axis is incident on the reflecting surface of the main reflector 100, the vector OB” from the origin O to point B” on the sub-reflector surface (the “” indicates that it is different from point B shown in FIG. 9B, etc.) is given by Equation 25 based on Equation 24 below.

[0125]

Number

[0126]

Number

[0127] Next, a method of equalizing the path lengths of radio wave signals that have passed through a large number of elements 206 arranged on the sub-reflector surface by correcting at least one of the shape of the sub-reflector surface and the positions of each of the large number of elements 206 will be described with reference to FIGS. 11A to 11E. A large number of elements 206 described with reference to FIGS. 6D to 6F are arranged on the sub-reflector surface of the support member 242 of the transmission correction member 240 derived as described with reference to FIGS. 9A, 9B, 10A to 10B as shown in FIGS. 6A to 6C. Each of the large number of elements 206 changes the traveling direction of the radio wave signal and changes the path length.

[0128] The path lengths of the radio waves passing through all of the numerous elements 206 arranged on the correction surface, as derived according to the design, must be equal, and therefore, the phases of these radio waves must be equal. Each of the numerous elements 206 arranged on the correction surface, whose shape is derived by the above formula, imparts a phase change to the radio wave signal, and the radio wave signal with a phase change is focused to a single point. On the other hand, each of the numerous elements 206 imparting a phase change to the radio wave signal is equivalent to each of the numerous elements 206 changing the path length of the radio wave signal by the amount of the phase change. Therefore, it is necessary to eliminate the difference in path length caused by the characteristics of each of the numerous elements 206, taking into account the difference in path length that each of the numerous elements 206 imparts to the radio wave signal.

[0129] Furthermore, explaining how to calculate the path length of a radio wave signal when it passes through a correction member 204 positioned on the correction surface of the reflector 202 of the sub-reflector 200, and the radio wave signal reflected by the reflector 202 passes through the correction member 204 again, becomes complicated. Therefore, in Figure 11A and other figures, the case in which the radio wave signal passes from the transmission correction member 240 to the correction surface of the support member 242 is shown without the support member 242. However, it will be obvious to those skilled in the art that the method for adjusting the path length, as explained with reference to Figure 11A and other figures, can be applied to adjusting the path length of a radio wave signal that has been reflected by the correction surface of the reflector 202 of the sub-reflector 200 and passed through a number of elements 206. Also, in Figure 11A and other figures, two elements 206 are positioned on the correction member 204. i-1 ,206 i The radio signals passing through are shown separately for the incident side and the outgoing side.

[0130] Figure 11A shows two adjacent elements 206 in the same row j on the correction surface. i-1, 206 i This figure illustrates an example of a radio wave signal passing through, separated into the incident and outgoing sides of the radio wave signal. As shown in Figure 11A, two elements 206 are included in the same row j in the matrix shown in Figure 6A and are adjacent to each other at a distance of d(m). i-1 ,206 i A radio signal tilted by β(°) with respect to the y-axis is incident from the incident side, and element 206 i-1 ,206j The radio wave signal, tilted by γ(°) with respect to the y-axis, is emitted to the output side. In this case, the wavefront of the radio wave signal on the input side is element 206 j These206 j-1 To reach it quickly and change the direction of travel on the output side, the radio signal is sent to element 206 j Faster than this: complex206 j It needs to be fired from there.

[0131] Figure 11B shows two adjacent elements 206 i-1 ,206 i This figure illustrates an example of a radio wave signal (curved wave) in which the incoming wavefront is curved. Note that Figure 11B shows element 206 i-1 ,206 i The curved wave ultimately generated by passing through is shown in Figure 11B, and the calculations required to generate the curved wave shown in Figure 11B will be described later by referring to the figures from Figure 11C onwards. i-1 The incident radio wave signal is measured from the z-axis to γ i-1 The path length is increased in the direction of the tilt and then emitted. In other words, element 206 i-1 This involves the radio signal from the z-axis to γ i-1 It is emitted with a phase delay in the direction tilted by that much. Meanwhile, element 206 i The incident radio wave signal is measured from the z-axis to γ i (≠γ i-1 The path length is increased and the phase is delayed in the direction tilted by ). As explained above, element 206 i-1 ,206 i Each of them measures the incoming radio wave signal from the z-axis to γ i-1 γ i When emitted in a direction tilted by only that much, element 206 i-1 ,206 j The wavefronts of the radio signals emitted from each are focused at the secondary focus SF.

[0132] Element 206 j The path length l corresponds to the phase change φ that should be applied to the radio signal. φ This is given by equation 26 below, using the symbols shown in Figure 11A.

[0133]

number

[0134] On the correction surface of the support member 242 of the transmission correction member 240, as shown in Figure 11B, the radio wave signal is a curved wave, as shown by element 206 i-1 ,206 i It passes through and exits in the direction of the secondary focus SF.

[0135] For example, first, as shown in Figure 6A, elements 206 are arranged in a matrix on the correction surface. xy Of these, the first element 206 of the i-th row (i≧1; i is an integer less than or equal to the number of elements 206 included in the i-th row) i,1 Change in path length lφ (i,1) This can be calculated. However, this "matrix-like" arrangement simply means that the elements 206 are arranged regularly at regular intervals. Therefore, the number of elements 206 in each row and each column of the arrangement of elements 206 does not have to be constant.

[0136] Next, element206 i,1 Change in path length due to length lφ (i,1) Next, element 206, the second element from the beginning of this line. (1,2) Change in path length lφ (i.2) and path length change lφ (i,1) The difference Δlφ (i,12) Calculate the path length change lφ (i,1) By adding or subtracting from it, the second path length change lφ from the beginning is obtained. (i,2) ( lφ (1,2) =lφ (i,1) +Δlφ (i,12) ). Thus, element 206 at the beginning of the i-th row i,1 Once the path length change due to this is calculated and becomes a known value, proceed similarly to element 206 i,j-1 The path length change lφ (j≧1; j is an integer less than or equal to the number of elements 206 in the i-th row) (i,j-1) , element 206 i,j-1 Change in path length lφ (i,j-1) and elements206 i,j Change in path length lφ(i,j) The difference Δlφ (i,j-1) Calculate the path length change lφ (i,j-1) By repeatedly adding or subtracting, all elements 206 contained in the i-th row i,j Change in path length lφ (i,j) This can be calculated.

[0137] Note that this path length change lφ i,j This can be obtained not only by calculations along the row direction as described here, but also by similar calculations along the column direction. As described above, the element 206 at the beginning of each row i,1 Change in path length lφ (i,1) The value of, or the first element 206 in each column 1,j Change in path length lφ (i,1) The value of can be known by calculation. Subsequently, by sequentially calculating the difference in path length change between two adjacent elements 206 in the row or column direction, the elements 206 arranged in a matrix on the correction surface as shown in Figure 6A xy Change in path length lφ due to all of the above xy The value of can be calculated.

[0138] Click all buttons 206 xy Change in path length lφ due to all of the above xy Once the value is calculated, element 206 xy The distance from the correction plane to the secondary focal point SF where the element is positioned can also be calculated. Therefore, all elements 206 xy The shape of the correction surface of the subreflector 200 or the support member 242 can be designed such that the path length from the correction surface to the subfocus SF of the radio wave signal passing through is equal. xy If the path length from the correction surface to the subfocus SF of the radio wave signal passing through is made equal, then the path length from the correction surface to the subfocus SF of the reference wavefront to the main reflector 100 to the reflector 202 or the support member 242 can also be made equal. Conversely, when the shape of the correction surface is predetermined while maintaining a certain precision, element 206 xy By adjusting at least one of the relative permittivity and relative permeability, element 206 xy The path length from the correction plane to the subfocus SF of the radio signal passing through can be made equal.

[0139] Next, we will examine the incident and exit sides of Figure 11A separately. Figure 11C shows the incident side shown in Figure 11A. In the numerous elements 206 attached to the correction surface, a curved wave is formed by the interaction of two adjacent elements 206, as shown in Figure 11B. Specifically, first, the first two elements 206 of a certain row j 1,j ,206 2,j The combination of elements interacts to form a curved wave, such that element 206 2,j The amount of phase change that should be given is calculated. Furthermore, the second set of two elements 206 2,j ,206 3,j The combination of elements interacts to form a curved wave, such that element 206 3,j The amount of phase change that should be given is calculated. Through repeated calculations like this, the i-1th two elements 206 in column j are calculated as shown in Figure 11B. i-1,j ,206 i,j The combination of elements interacts to form a curved wave, such that element 206 i,j The amount of phase change that should be given is calculated. Furthermore, through the repetition of such calculations, ultimately, the element 206 in column j is calculated. 1,j If the amount of phase change to be given is known, then element 206 in this column j 2,j ~206 x,j The amount of phase change that should be given to each of these can be calculated. Furthermore, in order to form a curved wavefront in the direction to be refracted, Huygens' principle applies to the element 206 on the right. i d difference in path length i sinγ i It is sufficient to apply a phase change (phase lag) equivalent to a minute. Here, we have explained how to calculate the amount of phase change to be applied to the element so that curved waves are formed sequentially in the row direction within a specific column. However, the amount of phase change to be applied to the element so that surface waves are formed sequentially in the column direction within a specific row may also be calculated. Furthermore, the amount of phase change to be applied to the element so that surface waves are formed sequentially in any direction, regardless of row or column direction, may also be calculated.

[0140] Figure 11D is a diagram showing the output side shown in Figure 11A. As shown in Figure 11C, the signal passes through the reference wavefront explained with reference to Figure 10C before reaching element 206. i-1,j ,206 i,j The path length for the radio signal to reach each point is the path length L. i-1,j ,L i,j It is stated as follows. Next, the output side of Figure 11A is considered. As shown in Figure 11D, element 206 i,j The wavefront of the radio signal incident on it is set to a desired angle γ with respect to the xz axis. i,j To orient it in the direction of the tilt, according to Huygens' principle, element 206 i However, the incoming radio signal d i,j sinγ i,j The path length can be increased by that amount to create a phase delay.

[0141] Figure 11E shows element 206 i Phase change lφ to be applied to the radio signal that has passed through. (i,j) The corresponding path length l φ(i) This is a diagram illustrating an example. As mentioned above, if the wavelength of the radio wave signal is λ, then element 206 i-1,j ,206 i,j In order to make the path lengths of the incoming radio signals the same, it is sufficient to solve the equations shown in Equations 27 and 28 below.

[0142]

number

[0143]

number

[0144] Therefore, element 206 i The path length l of the radio signal passing through φ(i) This is given by equation 29 below.

[0145]

number

[0146] Figure 12A illustrates an overview of the phase error correction process using the bisection method on the correction surface. A number of elements 206 are arranged in a matrix on the correction surface. i,j Element 206 located at the very end of the row 1,j The change in path length that affects the radio signal passing through it, that is, the amount of phase change, is 0(l φ(1,j) If we set it to =0, then the adjacent element 206 in that column 2,j The phase change (lφ) that this imparts to the radio signal (2,j) ) can be calculated by equation 29 above.

[0147] Element 206 2,j The amount of phase change in (l φ2j When ) is calculated, then the adjacent element 206 in that column is calculated. 3,j The amount of phase change that (l) imparts to the radio signal φ3j ) can be calculated by the above equation 29. In this way, a number of elements 206 arranged in a matrix xy The amount of phase change caused in the radio wave signal that each element passes through is determined by the number of elements 206 arranged in a matrix. xy Element 206 at the beginning of the row 1,j However, the amount of phase change that is imparted to the radio signal passing through it is 0(l φ1,j If we set =0, then all 206 elements in this column 3,j The amount of phase change that (l) imparts to the radio signal φi,j All of these can be calculated sequentially, like a string of beads.

[0148] In a parabolic antenna 20, etc., element 206 i-1,j Total path length L of the radio signal passing through total(i-1,j) L total(i-1,j) =DA BF+l φ(i-1,j) It is given by the formula. Also, element 206 i,j Total path length L of the radio signal passing through total(i,j) L total(i,j) =DA BF+l φ(i,j) It is given by the following formula. See Figure 9B for DABF.

[0149] Element 206 i,j The total path length of the radio signal passing through and element 206 i-1,j The difference from the total path length of the radio signal passing through is, element 206 i,j The length of the portion of the radio signal path passing through point AB is the path length A. i,j B i,j And element 206 i-1,j The length of the portion of the radio signal path passing through point AB is the path length A. i-1,j B i-1,j If so, (L total(i,j) -L total (i-1,j) )=(A i,j B i,j -A i-1,j B i-1,j ) and (A i,j B i,j -A i-1,j B i-1,j ) is the function f(A i,j B i,j )=L total(i,j) -L total(i-1,j) It can be defined as follows.

[0150] For example, the function f(A i,j B i,j ) is A i,j B i,j When the function f(A) is monotonically increasing, the following bisection methods (1) to (4) are performed. Through this bisection method, the function f(A) i,j B i,j The shape of the correction surface or element 206 will be changed so that the value of ) approaches 0 as closely as possible. i,j The position of the elements is changed, or both are done.

[0151] (1) f(A i,j B i,j A such that )>0 i B i =high and f(A i,j B i,j A such that ) < 0 i B i We define =low. (2)A i,j B i,j =high and A i,j B i,jFind the midpoint between =low and = (high + low) / 2. (3) If f(mid) < 0, update low to low = mid, and if f(mid) > 0, update high to high = mid. (4) Repeat steps (2) and (3) until |f(mid)| ≤ ε. However, in (4), ε is not the relative permittivity, but a positive constant determined by the user of the parabolic antenna, or a value within the range of calculation error.

[0152] Figure 12B illustrates the cross-sectional view of the correction surface before correction by the above correction processes (1) to (4) with a dotted line, and the cross-sectional view of the correction surface after correction with a solid line. Figure 12C illustrates the total path length of the radio wave signal with respect to the x-coordinate of the cross-section of the main reflector 100 before correction by the above processes (1) to (4), and the total path length of the radio wave signal with respect to the x-coordinate of the cross-section of the main reflector 100 after correction. Due to the correction by the above processes (1) to (4), the cross-section of the correction surface is corrected as shown in Figure 12B. Furthermore, due to the correction by the above processes (1) to (4), as shown in Figure 12C, the total path length of the radio wave signal is made almost uniform across the entire surface of the correction surface, and the phase difference is eliminated.

[0153] For example, as shown above with (1) to (4) in Figure 6B, element 206 i,j The amount of phase change in the radio signal passing through is 0(l φi,j It is assumed that =0). Element 206 i,j Element 206 is on the left side. i-1,j When there is element 206 i-1,j The amount of phase change that (l) imparts to the radio signal φi-1,j ) can be calculated by applying the above equation 29 in the row direction. Also, element 206 i,j The upper side of the related 206 i,j-1 When there is element 206 i,j-1 The amount of phase change that (l) imparts to the radio signal φi,j-1 This can be calculated by applying the above formula 29 in the column direction.

[0154] Also, element 206 i,j Element 206 is located on the left and upper sides. i-1,j ,206i,j-1 When there is element 206 i-1,j ,206 i,j-1 The amount of phase change that (l) imparts to the radio signal φi-1,j ,l φi,j-1 ) can be calculated by applying the above equation 29 in the row and column directions. Note that here, element 206 i,j Element 206 located diagonally i-1,j-1 The amount of phase change (l φi-1,j-1 Although the calculation of ) is not explained, the diagonal element 206 i-1,j-1 The amount of phase change that (l) imparts to the radio signal φi-1,j-1 It will be obvious to those skilled in the art that this can be calculated by the above equation 29, which has been modified to be applicable in the diagonal direction.

[0155] Let's explain the calculation of the amount of phase change in more detail. As shown in Figure 6B, element 206 is located on the left or upper side. i-1,j ,206 i,j-1 Element 206 i,j This is selected. As described above, from the reference wavefront, element 206 i-1,j The path length to L x And element 206 i、j Point B on the correction plane where the object is located. i Vector B from the secondary focus SF i The projection vector of F onto the xz plane is vector B. i F xz Therefore, element206 i,j ,206 i-1,j The angle of the phase gradient between them γ i This is given by equation 30 below.

[0156]

number

[0157] Similarly, element 206 i,j Element 206 adjacent to the x-axis i,j-1 This is selected. From the reference wavefront, element 206 i,j-1 The path length to L y And element 206 i,j Point B on the correction plane where the object is located.i Vector B from the secondary focus SF i The projection vector of F onto the yz plane is vector B. i F yz Therefore, element206 i,j ,206 i,j-1 The angle of the phase gradient between them γ j This is given by equation 31 below.

[0158]

number

[0159] Therefore, element 206 i,j The path length l corresponds to the phase change φ(i,j) that should be applied to the radio signal. φ(i,j) This is given by equation 32 below. Note that in the right-hand side of equation 32, d i sinγ i from l φ(i-1,j) The part up to element206 i,j and elements206 i-1,j The path length that can be considered from the interaction with d is shown below. j sinγ j from l φ(i,j-1) The part up to element206 i,j and elements206 i,j-1 The path length that can be considered from the interaction with element 206 is shown. i,j The path length l corresponds to the phase change φ(i) that should be applied to the radio signal. φ(i,j) Once calculated, element 206 i,j This path length l φ(i,j) Element 206 is used to impart a phase change corresponding to the above to the radio wave signal. i,j The relative permittivity ε and relative permeability μ of the dielectric plate 208, and the division spacing of the resonator 210 are adjusted.

[0160] When the above adjustments are performed sequentially from one end to the other of the elements 206, which are arranged at equal intervals along the x and y axes as shown in Figure 6A, all of the elements 206 are ultimately adjusted. Once all of the elements 206 are adjusted, each of the elements 206 will have a path length l as shown in Equation 32 below, according to the preset relative permittivity and relative permeability. φ(i,j) A phase change φ(i,j) corresponding to this is applied to the radio signal. Note that, as described above, L in equation 32 below i,j The radio signal passes through the reference wavefront before element 206 i,j This is the path length to reach, L i-1 , j From the reference wavefront, element 206 i-1,j This is the path length to [the destination].

[0161]

number

[0162] Alternatively, instead of the numerous elements 206, a material whose relative permittivity ε and relative permeability μ can be adjusted by computer control, such as a liquid crystal film or liquid crystal panel, can be placed on the correction surface. By using a material whose relative permittivity ε and relative permeability μ can be adjusted by computer control, the process described with reference to Figure 7 can be realized through dynamic and real-time control.

[0163] Some or all of the above embodiments may also be described as follows, but are not limited to the following: [Note 1] An antenna device comprising: a first electromagnetic wave focusing member that focuses electromagnetic waves incident from a predetermined first direction to a first focal point; and a second electromagnetic wave focusing member that focuses electromagnetic waves incident from a predetermined second direction different from the first direction to the first electromagnetic wave focusing member, and reflected by the first electromagnetic wave focusing member to a second focal point different from the first focal point. [Note 2] The antenna device according to Appendix 1, wherein there are multiple second focal points and comprises multiple second electromagnetic wave focusing members, each of which focuses the electromagnetic waves to one of the multiple second focal points. [Note 3] The antenna device according to Appendix 1 or 2, wherein the first electromagnetic wave focusing member is a first reflector that reflects the electromagnetic waves. [Note 4] The antenna device according to any one of the appendices 1 to 3, wherein the first electromagnetic wave focusing member is a parabolic reflector that reflects the electromagnetic waves with a parabolic surface. [Note 5] The antenna device according to any one of the appendices 1 to 4, wherein the second electromagnetic wave focusing member is a second reflector that reflects the electromagnetic waves and focuses them to the second focal point. [Note 6] The antenna device according to any one of the appendices 1 to 5, wherein the second electromagnetic wave focusing member comprises a second reflector that reflects the electromagnetic waves and makes the path length of the electromagnetic waves equal, and a first correcting member that focuses the electromagnetic waves reflected by the second reflector to the second focal point. [Note 7] The antenna device according to any one of the appendices 1 to 6, wherein the first correcting member focuses the electromagnetic waves reflected by the second reflector so that the same phase is maintained at the second focal point. [Note 8] The antenna device according to any one of the appendices 1 to 7, wherein the first correcting member focuses the electromagnetic waves reflected by the second reflector so that the path lengths of the waves are kept equal. [Note 9] The first corrective member is a metasurface, as described in any of the appendices 1 to 8 of the antenna device. [Note 10] The antenna device according to any one of the appendices 1 to 9, wherein the metasurface comprises a plurality of metaatoms, each having a resonant frequency. [Note 11] The antenna device according to any one of the appendices 1 to 10, wherein the resonant frequency, relative permittivity, and relative permeability of each of the plurality of metaatoms, or one or more thereof, are adjusted so that the path lengths of the electromagnetic waves reflected by the second reflector are equal. [Note 12] The antenna device according to any one of the appendices 1 to 11, wherein the second electromagnetic wave focusing member transmits the electromagnetic waves reflected by the first electromagnetic wave focusing member and guides them to the second focal point for focusing. [Note 13] The antenna device according to any one of 1 to 12, wherein the second electromagnetic wave focusing member comprises a first correction member that transmits the electromagnetic waves reflected by the first electromagnetic wave focusing member, and a second reflector that reflects the electromagnetic waves that have passed through the first correction member, emits them through the first correction member, and focuses them so that the same phase is maintained at the second focal point. [Note 14] The antenna device according to any one of the appendices 1 to 13, wherein the first correcting member focuses the electromagnetic waves reflected by the second reflector so that the path lengths of the waves are kept equal. [Note 15] The antenna device according to any one of the appendices 1 to 14, wherein the second electromagnetic wave focusing member comprises a plurality of metaatoms each having a resonant frequency, and a support member that transmits the electromagnetic waves and holds the plurality of metaatoms on its surface. [Note 16] The antenna device according to any one of the appendices 1 to 15, wherein the first electromagnetic wave focusing member transmits the electromagnetic waves and focuses them to the first focal point. [Note 17] The first corrective member is a liquid crystal, as described in any of the appendices 1 to 16 of the antenna device. It goes without saying that any combination of the forms described in the appendices of this disclosure, or any combination of the elements described in each perspective and embodiment (including the non-selection of some elements), can be made from time to time by those skilled in the art, in accordance with the basic concepts of this disclosure.

[0164] Furthermore, each disclosure of the above-mentioned patent documents and other materials cited is incorporated into this document by reference. Within the framework of this disclosure (including the claims), further modifications and adjustments to the embodiments or examples are possible based on their fundamental technical concept. Also, within the framework of this disclosure, various disclosure elements (including each element of each claim, each element of each embodiment or example, each element of each drawing, etc.) can be combined in various ways, and one or more of the various disclosure elements can be selected (including partial deletion). In other words, this disclosure naturally includes various modifications and changes that a person skilled in the art could make in accordance with the entire disclosure, including the claims, and the technical concept. In particular, numerical ranges described in this document should be interpreted as specifically describing any numerical value or sub-range included within that range, even if not specifically noted. Furthermore, matters well known to a person skilled in the art are considered to be included in the disclosures of this application that can be used in combination with the matters described in this document. In addition, each disclosure of the above-mentioned cited documents is considered to be included in the disclosures of this application that can be used in part or in whole as part of this disclosure, in accordance with the spirit of this disclosure, as necessary. [Explanation of Symbols]

[0165] 1, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38 Parabolic antenna 100,102 Main reflector 110 Main horn antenna 112 Sub-horn antenna 200 Secondary reflector 202 Reflector 204,244 Correction Members 206 elements 208 Dielectric Plate 210 resonator 240 Transmission Correction Member 242 Support member 5. Arithmetic Processing Unit 500 CPU 502 Main storage 504 Auxiliary storage device 506 Interface Circuit MF main focus science fiction subfocus

Claims

1. A first electromagnetic wave focusing member that focuses electromagnetic waves incident from a predetermined first direction to a first focal point, A second electromagnetic wave focusing member receives electromagnetic waves from a predetermined second direction different from the first direction and focuses the electromagnetic waves reflected by the first electromagnetic wave focusing member to a second focal point different from the first focal point. An antenna device equipped with the following features.

2. The aforementioned second focus has multiple points, The system comprises a plurality of the second electromagnetic wave focusing members, Each of the multiple second electromagnetic wave focusing members focuses the electromagnetic waves to one of the multiple second focal points. The antenna device according to claim 1.

3. The first electromagnetic wave focusing member is a first reflector that reflects the electromagnetic waves. The antenna device according to claim 1.

4. The first electromagnetic wave focusing member is a parabolic reflector that reflects the electromagnetic waves using a parabolic surface. The antenna device according to claim 1.

5. The second electromagnetic wave focusing member is a second reflector that reflects the electromagnetic waves and focuses them to the second focal point. The antenna device according to claim 1.

6. The second electromagnetic wave focusing member is A second reflector that reflects the electromagnetic waves and makes the path length of the electromagnetic waves equal, A first correcting member that focuses the electromagnetic waves reflected by the second reflector to the second focal point, The antenna device according to claim 1, comprising:

7. The first correcting member focuses the electromagnetic waves reflected by the second reflector so that the same phase is maintained at the second focal point. The antenna device according to claim 6.

8. The first correction member focuses the electromagnetic waves reflected by the second reflector so that the path lengths of the reflected waves are kept equal. The antenna device according to claim 6.

9. The first corrective member is a metasurface. The antenna device according to claim 6.

10. The metasurface comprises a plurality of metaatoms, each having a resonant frequency. The antenna device according to claim 9, comprising:

11. The resonant frequency, relative permittivity, and relative permeability of each of the plurality of metaatoms, or one or more thereof, are adjusted so that the path lengths of the electromagnetic waves reflected by the second reflector are equal. The antenna device according to claim 9.

12. The second electromagnetic wave focusing member transmits the electromagnetic waves reflected by the first electromagnetic wave focusing member, guides them to the second focal point, and focuses them. The antenna device according to claim 1.

13. The second electromagnetic wave focusing member is A first correction member that transmits the electromagnetic waves reflected by the first electromagnetic wave focusing member, A second reflector that reflects electromagnetic waves that have passed through the first correcting member, emits them through the first correcting member, and focuses them so that the same phase is maintained at the second focal point. The antenna device according to claim 12, comprising:

14. The first correction member focuses the electromagnetic waves reflected by the second reflector so that the path lengths of the reflected waves are kept equal. The antenna device according to claim 13.

15. The second electromagnetic wave focusing member is Multiple metaatoms, each having its own resonant frequency, A support member that transmits the electromagnetic waves and holds the plurality of metaatoms on its surface. The antenna device according to claim 12, comprising:

16. The first electromagnetic wave focusing member transmits the electromagnetic waves and focuses them to the first focal point. The antenna device according to claim 1.

17. The first correction member is a liquid crystal. The antenna device according to claim 6.

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