Array antenna and antenna system
The array antenna system addresses the challenge of providing uniform beamforming across extremely ultra-wideband frequencies by using concentric annular arrays and a fractal structure, resulting in enhanced performance and reduced element count.
Patent Information
- Application Number
- JP2023203453
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-30
- Publication Date
- 2025-06-11
AI Technical Summary
Existing array antenna systems struggle with providing homogeneous digital beamforming capabilities across a wide range of frequencies in extremely ultra-wideband applications, leading to performance degradation and challenges in specifying signal source positions and achieving required signal-to-noise ratios.
The array antenna system is designed with concentrically arranged annular antenna arrays, each with a different radius, and antenna elements positioned around the center of each array. This configuration, combined with a fractal structure that maintains similarity across different frequency bands, enables uniform beamforming capabilities across the extremely ultra-wideband frequency range.
This solution allows for homogeneous digital beamforming at all frequencies, minimizing the number of elements required in the adaptive array antenna, and ensuring consistent performance across the extremely ultra-wideband frequency range.
Smart Images
Figure 2025088633000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an array antenna and an antenna system.
Background Art
[0002] In beamforming over a bandwidth of three digits or more, which can be called an extremely ultra-wideband, compared with the conventional ultra-wideband of one to two digits, the directivity of the conventional antenna array changes greatly for each frequency, deteriorating the performance. Here, beamforming means a technique that enables observation in various directions simultaneously by digitally converting radio wave signals measured by a plurality of antennas. Many antennas have been proposed with self-complementary antennas as the leading broadband antennas (see, for example, Non-Patent Document 1), but they are discussed separately from the antenna array method, and the antenna array method tends to stop at the optimal theory of the arrangement of single antennas (see, for example, Non-Patent Document 2). Therefore, there are many partial reports of optimization enabling beamforming in an extremely ultra-wideband.
[0003] Examples of such situations include array antenna systems in radar and communication. As the bandwidth increases, the antenna dimensions required for operation on the low-frequency side become dominant, and when an antenna array is used, the density of the antenna array on the high-frequency side is insufficient, the antenna element spacing increases, causing grating lobes. A grating lobe means that when the element spacing of an antenna is set to one wavelength, the equiphase surfaces are aligned even in the lateral direction, and a beam with the same intensity as the front direction is emitted. In the case of an antenna array adapted to the high-frequency side, it inevitably becomes an over-dense antenna array for the low-frequency side, the coupling between antennas becomes significant, and the antenna element size is also insufficient, which becomes a factor for performance degradation. In addition, the aperture length on the low-frequency side is relatively insufficient, resulting in an increase in directivity spread (see, for example, Non-Patent Document 3).
[0004] In response to such problems, the broadband characteristics required for radar and communication that have been used so far are often in a frequency range of only several times to about an order of magnitude (for example, see Non-Patent Document 4). Alternatively, beamforming in the ultra-wideband often has a range where frequency dependence can be ignored. In addition, discussions have only been held on methods for reducing grating lobes at high frequencies within a range where antenna coupling does not occur in a coarse and dense antenna array (for example, see Non-Patent Document 5). In the extremely ultra-wideband, conventionally, it has been addressed by having a plurality of antenna systems with sufficient directivity for each required frequency band (for example, see Non-Patent Document 6).
Prior Art Documents
Non-Patent Documents
[0005]
Non-Patent Document 1
Non-Patent Document 2
Non-Patent Document 3
[0006] In recent years, in ultra-wideband radio wave observations spanning several orders of magnitude, there are high hopes for beamforming that can deliver good performance within the limited on-board resources of satellite receivers. However, in the case of extremely ultra-wideband radio wave observations that span several digits, the difference in beamforming performance for each frequency becomes significant, and there are problems that cannot be ignored in specifying the detailed signal source position and ensuring the required signal-to-noise ratio. In addition, the method of dividing the antenna system for each band also has a problem that the applicable conditions are limited in order to secure a plurality of antenna structures.
[0007] The present invention has been made in consideration of the above circumstances, and one of the objectives is to provide an array antenna and an antenna system that can provide homogeneous digital beamforming capabilities for each frequency in an array antenna capable of supporting an extremely ultra-wideband.
Means for Solving the Problems
[0008] The present invention has been made to solve the above problems, and as means, it has the following configuration. (1) The array antenna according to one embodiment of the present invention is concentrically arranged such that a plurality of annular antenna arrays having different radii have the same center, and a plurality of antenna elements are arranged at positions surrounding the center of each annular antenna array in each annular antenna array. The radius of each annular antenna array, the number of elements in the antenna element group of each annular antenna array, the shape resulting from the required effective length of the antenna element, and the antenna element arrangement of the annular antenna array have different annular antenna arrays according to the divided operating frequencies, and the whole of all the antenna elements has a fractal structure so as to have a similarity relationship, thereby having a uniform beamforming ability in an extremely ultra-wideband.
Effects of the Invention
[0009] According to one aspect of the present invention, it is possible to provide an array antenna that enables homogeneous digital beamforming at all frequencies and can minimize the number of elements in an adaptive array antenna compatible with an extremely ultra-wideband.
Brief Description of the Drawings
[0010]
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Embodiments for Carrying Out the Invention
[0011] "First Embodiment of Array Antenna" Hereinafter, regarding the array antenna according to the first embodiment of the present invention, a detailed description will be given with an example, but the present invention is not limited to the embodiments described below. FIG. 1(a) is a configuration diagram of an array antenna 1 according to the first embodiment. As shown in FIG. 1(a), the array antenna 1 includes, for example, at least two or more types (M≧2) of antenna elements ANTa, ANTb,... with different operating frequencies, and at least two or more types (M≧2) of circular ring antenna arrays Aa, Ab,.... In this case, for example, as the antenna elements, the antenna systems of ANTa and ANTb may be the same or different. FIG. 1(a) shows the antenna elements ANTa and ANTb when M = 2, and shows the circular ring antenna arrays Aa and Ab when M = 2. M can take any integer value of 2 or more, for example. The antenna elements ANTa and ANTb divide the entire frequency band Wf spanning the target three-digit or more extremely ultra-wideband into respective frequency bands Wfa and Wfb and operate in each, and have the necessary antenna lengths La and Lb and circular ring radii Ra and Rb depending on the operating frequency. The circular ring antenna array Aa is configured by providing a plurality of antenna elements along a virtual circle R1 with a circular ring radius Ra. The circular ring antenna array Ab is configured by providing a plurality of antenna elements along a virtual circle R2 with a circular ring radius Rb. The circular ring antenna arrays Aa and Ab are each configured by providing a necessary number of antenna elements along the concentrically arranged virtual circles R1 and R2. The circular ring radii Ra and Rb have necessary values determined by the operating frequency as will be described later. The necessary circular ring radii Ra and Rb and the antenna lengths (necessary effective lengths) La and Lb are set in a similar relationship as will be described later. The array antenna 1 has the number of antennas Na and Nb with intervals Da and Db between the antenna elements on the virtual circle R1 and on the virtual circle R2. In the form of FIG. 1, it is shown as an example where the number of antennas Na = 5 and Nb = 5.
[0012] Since FIG. 1(a) shows an example where the number of antennas Na = 5, antenna elements ANTa1, ANTa2, ANTa3, ANTa4, and ANTa5 are provided as antenna elements. Also, since it is an example where the number of antennas Nb = 5, antenna elements ANTb1, ANTb2, ANTb3, ANTb4, and ANTb5 are provided as antenna elements.
[0013] Antenna elements ANTa1 to ANTa5 are arranged at equal intervals Da around the virtual circle R1 along the virtual circle R1 with an antenna length La and an annular radius Ra, which are obtained from the operating frequency. Similarly, antenna elements ANTb1 to ANTb5 are arranged at equal intervals Db around the virtual circle R2 along the virtual circle R2 with an antenna length Lb and an annular radius Rb, which are obtained from the operating frequency. In the circular ring antenna arrays Aa and Ab, in order to obtain the required directivity, they have an annular radius (circular ring antenna array diameter: the radius caused by the required effective length) Ra such that the aperture lengths of antenna elements ANTa1 to ANTa5 can be obtained. Similarly, in order to obtain the same directivity, they have an annular radius (circular ring antenna array diameter) Rb such that the aperture lengths of antenna elements ANTb1 to ANTb5 can be obtained. For the antenna array formed by the virtual circle R1 and the array antenna 1 formed by the virtual circle R2, all parameters are in a similar relationship for the operating frequency and uniform directivity in the ultra-wideband. The intervals Da and Db between the antenna elements do not necessarily have to be equal intervals. When it is desired to enhance the performance or simplify it in a specific direction, non-equal intervals or some elements being thinned out may be used. Even in that case, as long as the ratio of each annular radius is the same ratio and the overall similarity is maintained and it has a fractal structure, it will have uniform beam characteristics in the extremely ultra-wideband. Here, the extremely ultra-wideband means, for example, a frequency band of three digits or more, and as an example, a band such as 100 MHz to 100 GHz.
[0014] As an example, for the circular antenna array Ab, the centers of the antenna elements ANTb1 to ANTb5 are located on the circumference of a virtual circle R2 having a circular radius Rb centered on the center O shown in FIG. 1. In the example of FIG. 1(a), the centers of the antenna elements ANTb1 to ANTb5 are arranged at equal intervals Db obtained by dividing the circumferential direction of the virtual circle R2 into five equal parts. Therefore, the five centers of the antenna elements ANTb1 to ANTb5 are arranged on the virtual circle R2 at intervals of 72° along the circumferential direction. When the positions occupied by the five centers of the antenna elements ANTb1 to ANTb5 on the virtual circle R2 are connected by line segments, a regular pentagon is drawn within the virtual circle R2. In other words, the center positions of the antenna elements ANTb1 to ANTb5 adjacent to each other around the circumference of the virtual circle R2 are arranged along the virtual circle R2 so as to be at equal intervals. Similarly, the antenna elements ANTa1 to ANTa5 are arranged with respect to the virtual circle R1. For this reason, when the positions occupied by the five centers of the antenna elements ANTa1 to ANTa5 on the virtual circle R1 are connected by line segments, a regular pentagon is drawn within the virtual circle R1.
[0015] In the present embodiment, the interval between the antenna element ANTa1 and the antenna element ANTa2 adjacent to each other around the virtual circle R1 is defined as Da. Similarly, the interval between the antenna element ANTa2 and the antenna element ANTa3 is defined as Da. Similarly, the interval between the antenna element ANTa3 and the antenna element ANTa4 is defined as Da. Similarly, the interval between the antenna element ANTa4 and the antenna element ANTa5 is defined as Da. Similarly, the interval between the antenna element ANTa5 and the antenna element ANTa1 is defined as Da. All of these intervals are equal. In the present embodiment, since the interval Da means the length of one side of the above-described regular pentagon, it means the straight-line distance between the centers of adjacent antenna elements along the virtual circle R1.
[0016] In this embodiment, the distance between the antenna element ANTb1 and the antenna element ANTb2 adjacent to each other circumferentially along the virtual circle R2 is defined as Db. Similarly, the distance between the antenna element ANTb2 and the antenna element ANTb3 is defined as Db. Similarly, the distance between the antenna element ANTb3 and the antenna element ANTb4 is defined as Db. Similarly, the distance between the antenna element ANTb4 and the antenna element ANTb5 is defined as Db. Similarly, the distance between the antenna element ANTb5 and the antenna element ANTb1 is defined as Db. All of these distances are equal. In this embodiment, since the distance Db means the length of one side of the regular pentagon, it means the linear distance between the centers of adjacent antenna elements along the virtual circle R2.
[0017] In the array antenna 1 shown in FIG. 1(a), the entire frequency band Wf is divided into two equal parts, and each antenna element operates in each of the frequency bands Wfa and Wfb. The relationship between the target overall frequency band Wf and its divided frequencies is shown in FIG. 1(b). The array antenna 1 is concentrically arranged such that a plurality of circular ring antenna arrays Aa and Ab having different radii have the same center. Also, a plurality of antenna elements ANTa..., ANTb... are arranged at positions surrounding the centers of the respective circular ring antenna arrays Aa and Ab in the respective circular ring antenna arrays Aa and Ab. The radii of the circular ring antenna arrays Aa and Ab, the number of elements in the antenna element group for each circular ring antenna array, and the shape and dimensions of the antenna elements all have a similar relationship according to the operating wavelength, so that the entire set of all the antenna elements ANTa..., ANTb... has a fractal structure. For this reason, the intervals of the circular ring antenna arrays are made equal for each operating wavelength. Therefore, even when beamforming is performed in an extremely ultra-wideband, a uniform beamforming ability can be exhibited in the extremely ultra-wideband.
[0018] Here, the fractal structure means a structure in which the same shape as the whole is reproduced when the whole of a specific figure is decomposed into several parts. Briefly, it can be said that it is a structure in which a certain part has a shape similar to the whole. In the structure of Fig. 1(a), it can be explained that the array antenna having the antenna elements ANTb1 to ANTb5 arranged at the vertex positions of the regular pentagon along the virtual circle R2 and the arrangement shape has the same fractal structure as the array antenna having the antenna elements ANTa1 to ANTa5 arranged at the vertex positions of the regular pentagon along the virtual circle R1 and the arrangement shape. For example, the antenna elements ANTb1 to ANTb5 and the circular ring antenna arrays Aa and Ab have a fractal structure with regularity such that the number of antennas in each circular ring antenna array is the same and the antenna intervals are relatively the same with respect to the operating frequency, and the shapes of the antenna elements ANTb1 to ANTb5 and the radii of the circular ring antenna arrays Aa and Ab are set accordingly. Also, the intervals between the antenna elements ANTb1 to ANTb5 may be non-uniform within the circular ring antenna arrays Aa and Ab or the configuration may be non-uniform due to some of the antenna elements being deleted, and the non-uniformity may have a fractal structure by having the same regularity in each of the circular ring antenna arrays Aa and Ab. When there is non-uniformity in the intervals between the antenna elements, it is possible to relax the specifications of the required beamforming for a specific direction, and thus the configuration is such that the degrees of freedom in some directions in the antenna arrays Aa and Ab are reduced.
[0019] "Second Embodiment of Array Antenna" In the example shown in Fig. 1(a), the antenna elements ANTa and ANTb when M = 2 and the circular ring antenna arrays Aa and Ab when M = 2 are shown. On the other hand, as shown in Fig. 2(a), as a second embodiment, the arrangement of the antenna elements ANTa, ANTb, ANTc, and ANTd in the array antenna 2 when M = 4 and the arrangement configuration of the circular ring antenna arrays Aa, Ab, Ac, and Ad when M = 4 are shown.
[0020] Since Fig. 2(a) shows an example where the number of antennas Na = 5, antenna elements ANTa1, ANTa2, ANTa3, ANTa4, and ANTa5 are provided as antenna elements. Also, since it is an example where the number of antennas Nb = 5, antenna elements ANTb1, ANTb2, ANTb3, ANTb4, and ANTb5 are provided as antenna elements. Also, since it is an example where the number of antennas Nc = 5, antenna elements ANTc1, ANTc2, ANTc3, ANTc4, and ANTc5 are provided as antenna elements. Also, since it is an example where the number of antennas Nd = 5, antenna elements ANTd1, ANTd2, ANTd3, ANTd4, and ANTd5 are provided as antenna elements.
[0021] The center of each of the antenna elements ANTa1 to ANTa5 of the circular ring antenna array Aa is located on the circumference of a virtual circle R1 having a circular ring radius Ra centered on the center O shown in Fig. 2(a). In the example of Fig. 2(a), the antenna elements ANTa1 to ANTa5 are arranged at equal intervals divided into five equal parts in the circumferential direction of the virtual circle R1. Therefore, the five centers of the antenna elements ANTa1 to ANTa5 are arranged at intervals of 72° along the virtual circle R1. When the positions occupied by the five centers of the antenna elements ANTa1 to ANTa5 on the virtual circle R1 are connected by line segments, a regular pentagon is drawn. The center of each of the antenna elements ANTb1 to ANTb5 of the circular ring antenna array Ab is located on the circumference of a virtual circle R2 having a circular ring radius Rb centered on the center O shown in Fig. 2(a). In the example of Fig. 2(a), the centers of the antenna elements ANTb1 to ANTb5 are arranged at equal intervals divided into five equal parts in the circumferential direction of the virtual circle R2. Therefore, the five centers of the antenna elements ANTb1 to ANTb5 are arranged at intervals of 72° along the virtual circle R2. When the positions occupied by the five centers of the antenna elements ANTb1 to ANTb5 on the virtual circle R2 are connected by line segments, a regular pentagon is drawn.
[0022] The annular antenna array Ac has antenna elements ANTc1 to ANTc5 located on the circumference of a virtual circle R3 having an annular radius (annular antenna array diameter) Rc centered on the center O shown in Fig. 2(a). In the example of Fig. 2(a), the centers of the antenna elements ANTc1 to ANTc5 are arranged at equal intervals obtained by dividing the circumferential direction of the virtual circle R3 into five equal parts. Therefore, the five centers of the antenna elements ANTc1 to ANTc5 are arranged at intervals of 72° along the virtual circle R3, and when the positions occupied by the five centers of the antenna elements ANTc1 to ANTc5 on the virtual circle R3 are connected by line segments, a regular pentagon is drawn. The annular antenna array Ad has antenna elements ANTd1 to ANTd5 located on the circumference of a virtual circle R4 having an annular radius (annular antenna array diameter) Rd centered on the center O shown in Fig. 2(a). In the example of Fig. 2(a), the antenna elements ANTd1 to ANTd5 are arranged at equal intervals obtained by dividing the circumferential direction of the virtual circle R4 into five equal parts. Therefore, the five centers of the antenna elements ANTd1 to ANTd5 are arranged at intervals of 72° along the virtual circle R4, and when the positions occupied by the five centers of the antenna elements ANTd1 to ANTd5 on the virtual circle R4 are connected by line segments, a regular pentagon is drawn. The installation positions and intervals of the antenna elements ANTc1 to ANTc5 in the annular antenna array Ac are in the same relationship as the antenna elements described in the configuration of Fig. 1(a), and the interval Dc between the antenna elements is defined. The installation positions and intervals of the antenna elements ANTd1 to ANTd5 in the annular antenna array Ad are in the same relationship as the antenna elements described in the configuration of Fig. 1(a), and the interval Dd between the antenna elements is defined.
[0023] In the array antenna 2 shown in Fig. 2(a), the overall frequency band Wf is divided into four parts, and each antenna element operates in each frequency band Wfa, Wfb, Wfc, and Wfd. The relationship between the target overall frequency band Wf and its divided frequencies is shown in Fig. 2(b). In the array antenna 2 shown in Fig. 2, in the sense that it is easy to realize uniform beamforming in the extremely ultra-wideband, the same operational effects as those of the first embodiment described above can be obtained.
[0024] The array antenna 2 is concentrically arranged such that a plurality of circular ring antenna arrays Aa, Ab, Ac, and Ad having different radii have the same center. Further, a plurality of antenna elements ANTa…, ANTb…, ANTc…, ANTd… are arranged at positions surrounding the centers of the respective circular ring antenna arrays Aa, Ab, Ac, and Ad in the respective circular ring antenna arrays Aa, Ab, Ac, and Ad. The radii of the circular ring antenna arrays Aa, Ab, Ac, and Ad, the number of elements in the antenna element group for each circular ring antenna array, and the shape of the antenna elements all have a similar relationship according to the operating wavelength, and the intervals between the circular ring antenna arrays Aa, Ab, Ac, and Ad are made equal for each operating wavelength so that the entire set of all antenna elements ANTa…, ANTb…, ANTc…, ANTd… has a fractal structure. For this reason, even when beamforming is performed in an extremely ultra-wideband, a uniform beamforming ability can be exhibited in the extremely ultra-wideband.
[0025] In the examples shown in FIGS. 1(b) and 2(b), when the entire frequency band Wf is divided and operated in each frequency band, an example in which the entire frequency band Wf is divided at equal intervals in terms of the ratio bandwidth has been described. However, when dividing the entire frequency band Wf, it may be divided at non-uniform intervals without dividing at equal intervals. Also, when dividing the entire frequency band Wf, a slope may be provided at a constant interval in terms of the ratio bandwidth, or an indefinite interval slope may be provided for each ratio bandwidth. Also, for example, as a usage method of uniform beamforming in the ultra-wideband according to the present invention, in the circular ring antenna array formed in each ratio bandwidth, a chirp signal may further be used within the band. "Third Embodiment of Array Antenna" FIG. 3(a) shows an array antenna 3 of a third embodiment in which, when dividing the entire frequency band Wf, it is divided at non-uniform intervals without dividing at equal intervals. In the array antenna 3 shown in Fig. 3(a), the antenna elements ANTa to ANTd have the same antenna arrangement positions as the antenna elements ANTa to ANTd shown in Fig. 2(a). However, when the entire frequency band is divided and each antenna element operates in each frequency band Wfa, Wfb, Wfc, and Wfd, the frequency bands Wfa, Wfb, Wfc, and Wfd are divided into four different bandwidths instead of all having the same bandwidth.
[0026] The third embodiment shown in Fig. 3(a) shows an array antenna 3 in which when the overall frequency Wf is divided into frequency bands Wfa, Wfb, Wfc, and Wfd, the relationship of the frequency bands is Wfa < Wfb < Wfc < Wfd. An example of the relationship Wfa < Wfb < Wfc < Wfd when dividing the overall frequency band Wf is shown in Fig. 3(b). As shown in Fig. 3(b), dividing the bandwidth means corresponding to the operating frequencies obtained by dividing the overall frequency band (extremely ultra-wideband) Wf into a plurality of bandwidths with a certain slope ratio. Also in the third embodiment shown in Figs. 3(a) and 3(b), in the sense that it is easy to realize uniform beamforming in the extremely ultra-wideband, the same operational effects as the configurations shown in Figs. 1(a) and 2(a) can be obtained.
[0027] Also in the third embodiment, for the array antenna 3 formed by each antenna element of the virtual circles R1 to R3, all parameters are in a similar relationship due to the operating frequency and uniform directivity in the ultra-wideband. Also, the intervals between the antenna elements do not necessarily have to be equal. When it is desired to enhance the performance or simplify in a specific direction, non-uniform intervals may be used, and some may be thinned out (deleted). Even in that case, if the overall similarity is maintained and it has a fractal structure, it will have uniform beam characteristics in the extremely ultra-wideband.
[0028] "Fourth Embodiment of the Array Antenna" The fourth embodiment shown in Fig. 4(a) shows an array antenna 4 in which when the overall frequency Wf is divided into frequency bands Wfa, Wfb, Wfc, and Wfd, the relationship of each frequency band is Wfa > Wfb > Wfc > Wfd. An example with the relationship of Wfa > Wfb > Wfc > Wfd when dividing the overall frequency band Wf is shown in Fig. 4(b). Also in the fourth embodiment shown in Figs. 4(a) and 4(b), in the sense that uniform beamforming can be realized in an extremely ultra-wideband, the same operational effects as the configuration shown in Fig. 3(a) can be obtained.
[0029] The antenna elements ANTa to ANTd provided in Figs. 1(a) and 2(b) may be of the same type of antenna method corresponding to the respective operating frequency bands Wfa, Wfb, or Wfa, Wfb, Wfc, Wfd, or different antenna methods. For example, they may be unified with self-relative antennas such as spiral antennas of different sizes to ensure each broadband property, and may be partially replaced with patch antennas or the like as long as the band performance can be ensured.
[0030] "The Fifth Embodiment of the Array Antenna" Fig. 5 shows an array antenna 5 according to the fifth embodiment of the present invention, and this array antenna 5 has the same antenna arrangement relationship as the array antenna 2 shown as the second embodiment based on Fig. 2(a). That is, it shows the arrangement of the antenna elements ANTa, ANTb, ANTc, and ANTd in the array antenna 2 when M = 4, and the arrangement of the annular antenna arrays Aa, Ab, Ac, and Ad when M = 4. In the fifth embodiment shown in Fig. 5, as an example, the antenna elements ANTd1 to ANTd5 are composed of spiral antennas, and at least one or more of the antenna elements ANTa1 to ANTa5, ANTb1 to ANTb5, and ANTc1 to ANTc5 are composed of patch antennas.
[0031] FIG. 5 can be described as an example in which a patch antenna that is narrowband on the central side and operates at a high frequency is arranged, and spiral antennas (ANTd1 to ANTd5) that are broadband on the outside and operate at a low frequency are arranged. Conversely, as the structure of FIG. 5, a structure may be adopted in which a patch antenna that is narrowband on the outside and operates at a high frequency is arranged, and a spiral antenna that is broadband on the outside and operates at a low frequency is arranged. Also in the fifth embodiment shown in FIGS. 5(a) and 5(b), the same operational effects as those of the configuration of the previously shown embodiment can be obtained in the sense that uniform beamforming can be realized in an extremely ultra-wideband.
[0032] In each embodiment according to the present invention, the antenna intervals Da and Db may be selected according to the antenna numbers Na and Nb in accordance with an acceptable grating lobe level. Also, the positions of the antenna elements ANTa and ANTb on the circular ring antenna arrays Aa and Ab may be the same position or different positions. For example, in the second to fifth embodiments shown in FIGS. 2 to 5, with respect to the concentric virtual circles R1 to R4, the antenna elements ANTa1, ANTb1, ANTc1, and ANTd1 are arranged on the same radius. Similarly, the antenna elements ANTa2, ANTb2, ANTc2, and ANTd2 are arranged on the same radius, the antenna elements ANTa3, ANTb3, ANTc3, and ANTd3 are arranged on the same radius, and the antenna elements ANTa4, ANTb4, ANTc4, and ANTd3 are arranged on the same radius. However, as shown in the array antenna 6 of the sixth embodiment shown below, they may be provided at positions that are not at the same radius position.
[0033] "Sixth Embodiment of Array Antenna" FIG. 6 shows an array antenna 6 according to the sixth embodiment of the present invention. This array antenna 6 has antenna elements ANTa1 to ANTa5, ANTb1 to ANTb5, ANTc1 to ANTc5, and ANTd1 to ANTd5, similar to the previous embodiments, but their arrangements are different. The circular antenna array Aa has antenna elements ANTa1 to ANTa5, the circular antenna array Ab has antenna elements ANTb1 to ANTb5, the circular antenna array Ac has antenna elements ANTc1 to ANTc5, and the circular antenna array Ad has antenna elements ANTd1 to ANTd5, which is the same as the previous embodiment.
[0034] As shown in the sixth embodiment shown in FIG. 6, for the concentric virtual circles R1 to R4, the antenna elements ANTa1, ANTc1, ANTb3, and ANTd3 are arranged on the same radius. Similarly, the antenna elements ANTb1, ANTd1, ANTa4, and ANTc4 are arranged on the same radius. Similarly, for the concentric virtual circles R1 to R4, the antenna elements ANTa2, ANTc2, ANTb4, and ANTd4 are located on the same radius, and the antenna elements ANTb2, ANTd2, ANTa5, and ANTc5 are located on the same radius. Similarly, the antenna elements ANTa3, ANTc3, ANTb5, and ANTd5 are located on the same radius. Similarly, the antenna elements ANTa3, ANTc3, ANTb5, and ANTd5 are located on the same radius. In the sixth embodiment, in the antenna lengths La of the antenna elements ANTa1 to ANTa5, the antenna lengths Lb of ANTb1 to ANTb5, the antenna lengths Lc of the antenna elements ANTc1 to ANTc5, and the antenna lengths Ld of the antenna elements ANTd1 to ANTd5, the relationship of La < Lb < Lc < Ld is established.
[0035] As shown in the sixth embodiment shown in FIG. 6, the antenna elements ANTa1 to ANTd5 arranged along the virtual circles R1 to R4 may have a different positional phase relationship of the antenna elements on each ring of the virtual circles R1 to R4 as shown in FIG. 6. In FIG. 6, as an example, the antenna elements are arranged with a half-phase shift for each ring of the virtual circles R1 to R4, and the antenna elements are arranged at a high density. Also in the array antenna 6, the radii of the annular antenna arrays Aa, Ab, Ac, and Ad, the number of elements in the antenna element group for each annular antenna array, and the shapes of the antenna elements all have a similar relationship according to the operating wavelength. The intervals between the annular antenna arrays are equal for each operating wavelength so that the entire set of all antenna elements ANTa..., ANTb..., ANTc..., ANTd... has a fractal structure. For this reason, even when beamforming is performed in an extremely ultra-wideband, a relatively high uniformity beamforming ability can be exhibited in the extremely ultra-wideband.
[0036] "Seventh Embodiment of Array Antenna" FIG. 7 shows an array antenna 7 according to the seventh embodiment of the present invention. This array antenna 7 has antenna elements ANTa1 to ANTa5, ANTb1 to ANTb5, ANTc1 to ANTc5, and ANTd1 to ANTd5 arranged in the same manner as in the previous sixth embodiment, but their radii are different. The annular antenna array Aa has antenna elements ANTa1 to ANTa5, the annular antenna array Ab has antenna elements ANTb1 to ANTb5, the annular antenna array Ac has antenna elements ANTc1 to ANTc5, and the annular antenna array Ad has antenna elements ANTd1 to ANTd5, which is the same as in the previous embodiment.
[0037] In the seventh embodiment shown in FIG. 7, the antenna lengths La of each of the antenna elements ANTa1 to ANTa5 and the antenna length Lb of the antenna elements ANTb1 to ANTb5 are made equal, and the antenna length Lc of the antenna elements ANTc1 to ANTc5 and the antenna length Ld of the antenna elements ANTd1 to ANTd5 are made equal. As shown in the seventh embodiment shown in FIG. 7, the antenna elements ANTa1 to ANTd5 arranged along the virtual circles R1 to R4, as shown in FIG. 7, have a plurality of annuli for one operating frequency, and the arrangement relationship and size may be such that they are in a similar relationship at each operating frequency. Thereby, the generated beam at each operating frequency can be made more high-performance.
[0038] With this structure, all the antenna elements ANTa1 to ANTa5 and ANTb1 to ANTb5 with antenna length La can have the same operating frequency, and all the antenna elements ANTc1 to ANTc5 and ANTd1 to ANTd5 with antenna length Lb can have the same operating frequency. The array antenna 7 shown in FIG. 7 can be described as a fractal structure having a regularity that the annular antenna arrays Aa, Ab or Ac, Ad provided for each divided operating frequency are a plurality of consecutive annular antenna arrays counted from the central annular antenna array among the plurality of concentrically arranged annular antenna arrays.
[0039] "Eighth Embodiment of Array Antenna" FIG. 8 shows an array antenna 8 according to the eighth embodiment of the present invention. This array antenna 8 has antenna elements ANTa1 to ANTa5, ANTb1 to ANTb5, ANTc1 to ANTc5, ANTd1 to ANTd5, and ANTe1 to ANTe5. The annular antenna array Aa has the antenna elements ANTa1 to ANTa5, the annular antenna array Ab has the antenna elements ANTb1 to ANTb5, the annular antenna array Ac has the antenna elements ANTc1 to ANTc5, and the annular antenna array Ad has the antenna elements ANTd1 to ANTd5, which is the same as the previous embodiment. In this embodiment, the antenna elements ANTe1 to ANTe5 are further provided in the annular antenna array Ae.
[0040] As shown in the eighth embodiment shown in FIG. 8, for the virtual circles R1 to R5 arranged concentrically, the antenna elements ANTa1, ANTb1, ANTd1, ANTc3, and ANTe3 are arranged on the same radius. Similarly, the antenna elements ANTc1, ANTe1, ANTa4, ANTb4, and ANTd4 are arranged on the same radius.
[0041] Similarly, for the virtual circles R1 to R5 arranged concentrically, the antenna elements ANTa2, ANTb2, ANTd2, ANTc4, and ANTe4 are arranged on the same radius. Similarly, the antenna elements ANTc2, ANTe2, ANTa5, ANTb5, and ANTd5 are located on the same radius. Similarly, the antenna elements ANTa3, ANTb3, ANTd3, ANTc5, and ANTe5 are located on the same radius.
[0042] In the eighth embodiment, the antenna lengths La of the antenna elements ANTa1 to ANTa5, the antenna lengths Lb of the antenna elements ANTb1 to ANTb5, the antenna lengths Lc of the antenna elements ANTc1 to ANTc5, the antenna lengths Ld of the antenna elements ANTd1 to ANTd5, and the antenna lengths Le of the antenna elements ANTe1 to ANTe5 have the following relationships. La = Lc < Lb = Le < Ld
[0043] As shown in the eighth embodiment shown in FIG. 8, the antenna elements ANTa1 to ANTe5 arranged along the virtual circles R1 to R5 may have a non-consecutive circular array arrangement relationship when each operating frequency has a plurality of circular arrays as shown in FIG. 8. Thereby, the antenna array at each operating frequency can improve the ability of the two-dimensional array and enable higher-performance beamforming. Also in the array antenna 8, the radii of the circular antenna arrays Aa, Ab, Ac, Ad, and Ae, the number of elements in the antenna element group for each circular antenna array, and the shape of the antenna elements all have a similar relationship according to the operating wavelength. The intervals between the circular antenna arrays are made equal for each operating wavelength so that the entire set of all antenna elements ANTa..., ANTb..., ANTc..., ANTd..., ANTe... has a fractal structure. For this reason, even when beamforming is performed in an extremely ultra-wideband, a uniform beamforming ability can be exhibited in the extremely ultra-wideband.
[0044] With the structure of the array antenna 8, all of the antenna elements ANTa1 to ANTa5 and ANTc1 to ANTc5 having the same antenna lengths La and Lc can have the same operating frequency, and all of the antenna elements ANTb1 to ANTb5 and ANTe1 to ANTe5 having the antenna length Lb can have the same operating frequency. The array antenna 8 can be described as a fractal structure in which a plurality of circular ring antenna arrays Aa, Ac or circular ring antenna arrays Ab, Ae corresponding to divided operating frequencies are arranged in a discontinuous manner among the plurality of concentrically arranged circular ring antenna arrays Aa, Ab, Ac, Ad, Ae counting from the center.
[0045] "The Ninth Embodiment of the Array Antenna" FIG. 9 shows the array antenna 9 according to the ninth embodiment of the present invention. This array antenna 9 has antenna elements ANTa1 to ANTa5, ANTb1 to ANTb10, and ANTc1 to ANTc10. In this embodiment, the configuration in which the circular ring antenna array Aa has the antenna elements ANTa1 to ANTa5 is the same as that of the previous embodiment. In this embodiment, the antenna elements ANTb1 to ANTb10 are provided on the circular ring antenna array Ab, and the antenna elements ANTc1 to ANTc10 are provided on the circular ring antenna array Ac.
[0046] As shown in the ninth embodiment shown in FIG. 9, for the concentric virtual circles R1 to R3, the antenna elements ANTa1, ANTb1, ANTc1, ANTb6, and ANTc6 are arranged on the same radius. Similarly, the antenna elements ANTb2, ANTc2, ANTa4, ANTb7, and ANTc7 are arranged on the same radius. For the concentric virtual circles R1 to R3, the antenna elements ANTa2, ANTb3, ANTc3, ANTb8, and ANTc8 are arranged on the same radius. Similarly, the antenna elements ANTb4, ANTc4, ANTa5, ANTb9, and ANTc9 are arranged on the same radius. For the concentric virtual circles R1 to R3, the antenna elements ANTa3, ANTb5, ANTc5, ANTb10, and ANTc10 are arranged on the same radius.
[0047] In the ninth embodiment, the antenna lengths of the antenna elements ANTa1 to ANTa5 are La. The antenna lengths of the antenna elements ANTb2, ANTb4, ANTb6, ANTb8, and ANTb10 are Lb1, and the antenna lengths of the antenna elements ANTb1, ANTb3, ANTb5, ANTb7, and ANTb9 are Lb2. The antenna lengths of the antenna elements ANTc1, ANTc3, ANTc5, ANTc7, and ANTc9 are Lc1, and the antenna lengths of the antenna elements ANTc2, ANTc4, ANTc6, ANTc8, and ANTc10 are Lc2. The antenna lengths La, Lb1, Lb2, Lc1, and Lc2 have the following relationship. Lb1 < La < Lb2 < Lc2 < Lc1
[0048] As shown in the ninth embodiment shown in FIG. 9, the antenna elements ANTa1 to ANTc10 arranged along the virtual circles R1 to R3 may be sized and arranged such that one or more circular arrays for each operating frequency partially share the circular arrays of other operating frequencies. Thereby, the high-frequency array expansion can be efficiently arranged at the positions where there is space on the low-frequency side. In the array antenna 9 of the ninth embodiment, the antenna length Lb2 of the antenna elements ANTb1, ANTb3, ANTb5, ANTb7, and ANTb9 arranged along the virtual circle R2 is different from the antenna length Lb1 of the antenna elements ANTb2, ANTb4, ANTb6, ANTb8, and ANTb10. Also, the antenna length Lc1 of the antenna elements ANTc1, ANTc3, ANTc5, ANTc7, and ANTc9 arranged along the virtual circle R3 is different from the antenna length Lc2 of the antenna elements ANTc2, ANTc4, ANTc6, ANTc8, and ANTc10. In one circular antenna array Ab or one circular antenna array Ac as in this embodiment, a plurality of combinations of antenna elements with different antenna lengths may be provided.
[0049] In the case of the structure of the array antenna 9, the antenna lengths La, Lb1, Lb2, Lc1, and Lc2 are different. All the antenna elements with the same antenna length La can operate at the same frequency, all the antenna elements with the same antenna length Lb1 can operate at the same frequency, all the antenna elements with the same antenna length Lb2 can operate at the same frequency, all the antenna elements with the same antenna length Lc1 can operate at the same frequency, and all the antenna elements with the same antenna length Lc2 can operate at the same frequency.
[0050] In the case of the structure of the array antenna 8, all the antenna elements ANTa1 to ANTa5 can have the same operating frequency. All the antenna elements ANTb1, ANTb3, ANTb5, ANTb7, and ANTb9 can have the same operating frequency, and all the antenna elements ANTb2, ANTb4, ANTb6, ANTb8, and ANTb10 can have the same operating frequency. All the antenna elements ANTc1, ANTc3, ANTc5, ANTc7, and ANTc9 can have the same operating frequency, and all the antenna elements ANTc2, ANTc4, ANTc6, ANTc8, and ANTc10 can have the same operating frequency.
[0051] The array antenna 9 can be described as having a fractal structure in which a plurality of circular-ring antenna arrays corresponding to divided operating frequencies have a regularity shared with a plurality of circular-ring antenna arrays in other bands. That is, the antenna elements ANTb1, ANTb3, ANTb5, ANTb7, and ANTb9 and the antenna elements ANTb2, ANTb4, ANTb6, ANTb8, and ANTb10 are arranged in the array antenna 9 with a shared regularity. Also, the antenna elements ANTc1, ANTc3, ANTc5, ANTc7, and ANTc9 and the antenna elements ANTc2, ANTc4, ANTc6, ANTc8, and ANTc10 are arranged in the array antenna 9 with a shared regularity.
[0052] "First Embodiment of the Antenna System" FIG. 10 shows an antenna system 12 according to the first embodiment, which includes connecting any one of the array antennas 1 to 9 according to each of the embodiments described above as the array antenna 10 to a power combiner / divider G, and connecting a signal processing device 11 equipped with an amplifier and a digital / analog converter to each antenna element. Any one of the array antennas 1 to 9 of the previous embodiments may be applied to the array antenna 10. In FIG. 10, the first embodiment shown in FIG. 1 is applied, and each antenna element is represented using abbreviations such as ANTa and ANTb. The wiring from each antenna element is integrated in the front-end circuit F and connected to a power combiner / divider G provided in the front-end circuit F. As an example, the power combiner / divider G operates in analog, but a multi-beam may be formed by increasing the number of inputs / outputs from the digital part and parallelizing different power supply paths.
[0053] "Second Embodiment of Antenna System" When uniform adaptive beamforming performance is required at each frequency as described above, the antenna system according to the second embodiment shown in FIG. 11 may be adopted. The antenna system 13 shown in FIG. 11 shows an example in which a phase shifter P for correcting a phase shift is incorporated into the wiring of the front-end circuit F between the power combiner / divider G and each antenna element. Other configurations are the same as those of the antenna system 12 shown in FIG. 10. Regarding the amount of phase shift correction in each phase shifter P, a plurality of types of phase shifters P with different correction amounts are prepared so that the adjustment amount can be changed for each antenna element, and they can be individually applied to each antenna element. Thereby, even when a difference in the length of the power supply line occurs in a large-scale array antenna, in-phase power supply to the circular array for each operating frequency becomes possible. The signals from each antenna element are sent to the signal processing device 11 after the phase shift is eliminated by each phase shifter P, and beamforming is performed. With the antenna system 13 having the configuration shown in FIG. 11, uniform beamforming is possible in an extremely ultra-wideband. Of course, the aforementioned phase shift may be corrected in the analog path of the front-end circuit F. In this embodiment, the analog path of the phase shifter P or the front-end circuit F constitutes an analog correction unit for phase difference correction. In the annular antenna array, the antenna elements are displaced and arranged such that they are not at the same position in the circumferential direction of each annular antenna array but are rotated in the circumferential direction, and an analog correction unit or a digital correction unit for phase difference correction between the annular antenna arrays caused by the displacement in the circumferential direction of each annular antenna array can be adopted.
[0054] "Third Embodiment of Antenna System" When uniform adaptive beamforming performance is required at each frequency as described above, the antenna system of the third embodiment shown in FIG. 12 may be adopted. The antenna system 14 shown in FIG. 12 is shown as an example in which all antenna elements are connected to individual signal processing devices 11. With the configuration shown in FIG. 12, since the signals from the individual antenna elements are directly input to the individual signal processing devices 11, digital beamforming can be performed after correcting the phase shift for each antenna element in the individual signal processing devices 11. Therefore, with the antenna system 14 having the configuration shown in FIG. 12, uniform beamforming is possible in the extremely ultra-wideband range. Note that all the signals from the respective antenna elements are input to individual direct signal processing devices 11. Therefore, by providing a digital correction unit in the digital circuit of the signal processing device 11 to cancel the phase difference generated in the signals from the respective antenna elements, the phase difference between the antenna elements can be corrected.
[0055] "Fourth Embodiment of Antenna System" When uniform adaptive beamforming performance is required at each frequency as described above, the antenna system of the fourth embodiment shown in FIG. 13 may be adopted. The antenna system 15 shown in Fig. 13 is configured such that a plurality of frequency combiners Ga, Gb, Gc, Gd, Ge are provided in the front-end circuit F connected to each antenna element, and one or more antenna elements are connected to the signal processing device 11 via any of the frequency combiners Ga, Gb, Gc, Gd, Ge.
[0056] In the structure shown in Fig. 13, the antenna elements are arranged on each annular antenna array so as to be at the same position in the circumferential direction of each annular antenna array. Then, the antenna elements arranged at the same position in the circumferential direction of each annular antenna array on each annular antenna array are collectively connected to any one of the frequency combiners Ga to Ge. Further, the signal processing device 11 is connected to each of the frequency combiners Ga, Gb, Gc, Gd, Ge. Also, a phase shifter P is incorporated at a necessary position of the wiring of the front-end circuit F. Therefore, with this structure, it is possible to receive radio waves by dividing the band for each annular antenna array.
[0057] According to the antenna system 15, the signal from each antenna element can be branched and combined as an analog signal by any one of the frequency combiners Ga to Ge after correcting the phase shift by the phase shifter P in the front-end circuit F. For the antenna system 14 having the configuration shown in Fig. 13, uniform beamforming is possible in the extremely ultra-wideband. Also, if the configuration is such that the wirings from a plurality of antenna elements are collectively connected to one signal processing device 11 via one combiner, the number of signal processing devices 11 can be reduced compared to the configuration shown in Fig. 12.
[0058] As described above, the power supply method to each antenna element ANTa and ANTb may be analogously branched and combined by the power combiner / splitter G in the front-end circuit F, or a digital-to-analog converter DAC and an amplifier circuit AMP may be prepared for each antenna element and individually powered. Furthermore, one or a plurality of types of digital-to-analog converters DAC and amplifier circuits AMP may be used to cover the corresponding frequencies, and accordingly, the frequency combiner / splitters Ga to Ge may also be adjusted in terms of type and number of circuits. Alternatively, in order to use the same digital-to-analog converter DAC and amplifier circuit AMP for each divided frequency band Wfa and Wfb, a frequency conversion circuit may be used in accordance with each operating frequency band.
[0059] The array antenna applied to each of the embodiments described above can form a uniform directivity characteristic even in an extremely ultra-wideband, so that even when applied to an adaptive array antenna, it enables the same beamforming in an extremely ultra-wideband. According to the array antenna of each embodiment, as an overall structure, a relationship having a similar configuration is formed in both the antenna element and the antenna array, and by forming a fractal structure as a whole, uniform beamforming is enabled even in an extremely ultra-wideband. As a practical example, when the antenna mounting area and the scale of the electric circuit are limited, such as in space equipment or aircraft equipment, by determining the diameter of the annular antenna array and the number of antenna elements for the lowest frequency on the outside according to the above-described embodiment, the entire inner annular antenna array for high-frequency operation can be optimally designed to achieve uniform beamforming.
[0060] "Tenth Embodiment of Array Antenna" FIG. 14 shows the array antenna 20 according to the tenth embodiment of the present invention and its installation configuration. In FIG. 14, the circle drawn in the center indicates the sun 21, and a plurality (five in FIG. 14) of artificial satellites 22 are arranged along the first circular orbit R20 centered on the sun 21. And the array antenna 20 described below is mounted on each artificial satellite 22.
[0061] The array antenna 20 has a structure in which each antenna element is arranged concentrically so as to have the same fractal structure as that of any one of the array antennas 1 to 9 described above with reference to FIGS. 1 to 9. In FIG. 14, as an example of the array antenna 20, there are circular ring antenna arrays Aa, Ab, Ac, Ad, Ae. The circular ring antenna arrays Aa, Ab, Ac, Ad each have five antenna elements, and the circular ring antenna array Ae has antenna elements ANTe1 to 5 with a large antenna length and antenna elements ANTe6 to 10 with a small antenna length. The array antenna 20 with details drawn up to the antenna elements in FIG. 14 is shown in an enlarged view compared to other array antennas 20 provided along the first circular orbit R20, but the structures of the array antennas 20 provided along the first circular orbit R20 are all the same.
[0062] In FIG. 14, further, a second circular orbit R24 with a larger radius centered on the sun 21 is drawn outside the first circular orbit R20, and five artificial satellites 25 are arranged along this second circular orbit R24 so as to surround the sun 21. Each artificial satellite 25 is also equipped with an array antenna 20 having the same structure as the array antenna 20 described above. The five artificial satellites provided on the first circular orbit R20 are arranged at equal intervals around the first circular orbit R20, and the five artificial satellites provided on the second circular orbit R24 are also arranged at equal intervals around the second circular orbit R24. The positions of the artificial satellites 22 installed on the first circular orbit R20 and the positions of the artificial satellites 25 installed along the second circular orbit R24 are positions having a fractal structure equivalent to the arrangement relationship of each antenna element provided in the circular ring antenna arrays Aa, Ab shown in FIG. 1(a).
[0063] The array antenna 20 can be arranged along concentric first and second circular orbits R20 and R24 with different radii surrounding the sun 21 as shown in FIG. 14. By using the array antenna 20 arranged as shown in FIG. 14, it is possible to receive radio waves flying in outer space and enable digital beamforming in an extremely ultra-wideband. When artificial satellites 22 and 25 are placed in the first circular orbit R20 and the second circular orbit R24, a part of them may be formed on planets or satellites within the solar system, and may also be used on orbits around or in geostationary orbits with respect to the planets or satellites. Each artificial satellite 22 and 25 may be orbited so as to draw an orbit that does not disrupt the arrangement of the fractal structure shown in Fig. 14. When formation is difficult, a part of the fractal configuration may be disrupted according to the required performance. Some of the array configurations may be thinned while maintaining similarity.
[0064] By arranging the array antenna 20 as shown in Fig. 14, digital beamforming capable of handling a large scale and an extremely ultra-low frequency band such as below nanohertz becomes possible. The arrangement of the array antenna 20 shown in Fig. 14 can be applied to any of the following: arrangement on the earth's surface, arrangement on an aircraft on an airway, arrangement on a ship at sea, arrangement on the lunar surface, arrangement on a satellite orbit, on inner and outer planets, or arrangement using artificial satellites on orbits around or in geostationary orbits of planets or satellites. And uniform digital beamforming can be realized even in extremely ultra-wideband beamforming in these various installation environments.
[0065] As described above, when applying the array antenna 20 to equipment mounting resources such as satellite mounting or aircraft mounting where there are limitations, it is preferable to adopt the configuration shown below. In this case, it is desirable to determine the radius of the circular ring antenna array for the lowest frequency from the antenna area that can be mounted on the equipment, determine the number of antenna elements according to the circuit scale that can be mounted on the equipment, and adopt a configuration that results in a uniform beam during beamforming.
Explanation of symbols
[0066] 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20... array antenna, 11... signal processing device, 12, 13, 14, 15... antenna system, Aa, Ab, Ac, Ad, Ae... circular ring antenna array, ANTa1, ANTa2, ANTa3, ANTa4, ANTa5... antenna element, ANTb1, ANTb2, ANTb3, ANTb4, ANTb5... antenna elements, ANTc1, ANTc2, ANTc3, ANTc4, ANTc5... antenna elements, ANTd1, ANTd2, ANTd3, ANTd4, ANTd5... antenna elements, ANTe1, ANTe2, ANTe3, ANTe4, ANTe5... antenna elements, Da, Db, Dc, Dd... antenna spacing, G... power combiner / splitter, Ga, Gb, Gc, Gd, Ge... frequency combiner / splitter, P... phase shifter (analog correction unit), Ra, Rb, Rc, Rd, Re... circular antenna array diameter (radius of the circular antenna array) R1, R2, R3, R4... virtual circle, Wf... overall frequency band, Wfa, Wfb, Wfc, Wfd... divided frequencies.
Claims
1. A plurality of circular ring antenna arrays having different radii are concentrically arranged so as to have the same center, and a plurality of antenna elements are arranged at positions surrounding the center of each circular ring antenna array. By having the circular ring antenna arrays, where the radius of each circular ring antenna array, the number of elements in the antenna element group of each circular ring antenna array, the shape resulting from the required effective length of the antenna element, and the antenna element arrangement of the circular ring antenna array are different according to the divided operating frequencies, and having a fractal structure such that the entirety of all the antenna elements has a similarity relationship, an array antenna having a uniform beamforming ability in an extremely ultra-wideband is obtained.
2. The antenna element and the circular ring antenna array have a fractal structure with regularity such that they correspond to the operating frequencies obtained by arbitrarily dividing the extremely ultra-wideband, and such that the shape of each antenna element and the radius of each circular ring antenna array are in accordance. The array antenna according to Claim 1.
3. The antenna element and the circular ring antenna array have a fractal structure with regularity such that they correspond to the operating frequencies obtained by equally dividing the extremely ultra-wideband in terms of the bandwidth ratio, and such that the shape of each antenna element and the radius of each circular ring antenna array are in the same ratio. The array antenna according to Claim 2.
4. The antenna element and the circular ring antenna array have a fractal structure with regularity such that they correspond to the operating frequencies obtained by dividing the extremely ultra-wideband into a bandwidth with a certain slope ratio in terms of the bandwidth ratio, and such that the shape of each antenna element and the radius of each circular ring antenna array are in the same ratio. The array antenna according to Claim 2.
5. The antenna element is an antenna element with a different structure corresponding to each corresponding bandwidth among the plurality of circular ring antenna arrays. The array antenna according to Claim 1 or Claim 2.
6. Among the antenna elements with different structures, one type is a patch antenna and the other type is a spiral antenna. The array antenna according to Claim 5.
7. In the plurality of annular antenna arrays, the antenna elements have different structures. Among the plurality of concentrically arranged annular antenna arrays, in terms of the ratio bandwidth, a patch antenna with a narrow bandwidth on the central side and operating at a high frequency is arranged, and a spiral antenna with a wide bandwidth on the outer side and operating at a low frequency is arranged. The array antenna according to claim 5.
8. In the plurality of annular antenna arrays, in a structure in which antenna elements having different structures are provided, among the plurality of concentrically arranged annular antenna arrays, in terms of the ratio bandwidth, a patch antenna with a narrow bandwidth on the outer side and operating at a high frequency is arranged, and a spiral antenna with a wide bandwidth on the central side and operating at a low frequency is arranged. The array antenna according to claim 5.
9. The antenna element and the annular antenna array have a fractal structure with regularity such that the number of antennas in each annular antenna array is the same and the antenna spacing is relatively the same with respect to the operating frequency, in terms of the shape of each antenna element and the radius of each annular antenna array. The array antenna according to claim 1.
10. The spacing between the antenna elements is non-uniform within the annular antenna array or is non-uniform due to a configuration in which some of the antenna elements are deleted, and the non-uniformity has a fractal structure by having the same regularity in each annular antenna array. The array antenna according to claim 1.
11. The non-uniformity of the spacing between the antenna elements is formed by reducing the degree of freedom in some directions in the antenna array because it is possible to relax the specifications of the required beamforming for a specific direction. The array antenna according to claim 10.
12. The antenna element has a fractal structure with regularity such that it is in the same position in the circumferential direction of each annular antenna array in each annular antenna array, and the antenna elements arranged at the same position in the circumferential direction of each annular antenna array on each annular antenna array are band-divided for each annular antenna array by a frequency combiner. The array antenna according to claim 1.
13. In each of the annular antenna arrays, the antenna elements are displaced and arranged such that they are not in the same position in the circumferential direction of each annular antenna array but are rotated in the circumferential direction, and an analog correction unit or a digital correction unit for phase difference correction between the annular antenna arrays caused by the displacement in the circumferential direction of each annular antenna array is provided. The array antenna according to claim 1.
14. The annular antenna array has a plurality of annular antenna arrays provided for each of the divided operating frequencies. The array antenna according to claim 1.
15. The annular antenna arrays provided for each of the divided operating frequencies have a fractal structure having a regularity such that they are a plurality of consecutive annular antenna arrays counted from the annular antenna array on the center side among the plurality of concentrically arranged annular antenna arrays. The array antenna according to claim 14.
16. The plurality of annular antenna arrays corresponding to the divided operating frequencies are arranged in a fractal structure showing a regularity such that they are a plurality of annular antenna arrays arranged discontinuously from the center among the plurality of concentrically arranged annular antenna arrays. The array antenna according to claim 14.
17. The plurality of annular antenna arrays corresponding to the divided operating frequencies have a fractal structure having a regularity shared with the plurality of annular antenna arrays in other bands. The array antenna according to claim 14.
18. A part of the plurality of annular antenna arrays corresponding to the divided operating frequencies is formed around the antenna arrangement in other annular arrays, and has a similar configuration as a whole and is a fractal structure. The array antenna according to claim 14.
19. In the case where there are restrictions on equipment mounting resources such as satellite mounting or aircraft mounting, etc., for the annular antenna array, the radius of the annular antenna array for the lowest frequency is set from the antenna area that can be mounted on the equipment, and the number of the antenna elements is set according to the circuit scale that can be mounted on the equipment, so that the annular antenna array has a uniform beamforming ability. The array antenna according to claim 14.
20. The circular antenna array is a concentrically arranged circular antenna array applied to an artificial satellite located on the earth's surface, air route, sea, lunar surface, satellite orbit, inner and outer planets, or the orbits around planets and satellites or the geostationary orbit, and is capable of corresponding to an extremely ultra-low frequency band below nanohertz. The array antenna according to claim 14.
21. An antenna system comprising the array antenna according to any one of claims 1 to 4 and a signal processing device.
22. An antenna system comprising the array antenna according to any one of claims 9 to 14 and a signal processing device.
23. An antenna system comprising the array antenna according to any one of claims 15 to 18 and a signal processing device.