Patent Publication Number: US-11646505-B2

Title: Communication apparatus and antenna having elements disposed on curved surface of base having dome shape

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of priority of provisional application 62/880,393 filed on Jul. 30, 2019, the contents all of which are incorporated herein by reference, and the benefit of foreign priority of Japanese patent application 2020-072291 filed on Apr. 14, 2020, the contents all of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to communication apparatuses and antennas. 
     2. Background Art 
     Unexamined Japanese Patent Publication No. 2002-158525 discloses a satellite tracking antenna control device capable of accurately tracking a satellite for a long time by controlling an antenna. In the satellite tracking antenna control device disclosed in Unexamined Japanese Patent Publication No. 2002-158525, an attitude of the satellite tracking antenna is mechanically moved to track the satellite. 
     SUMMARY 
     Non-limiting exemplary embodiments of the present disclosure contribute to providing a communication apparatus that can appropriately communicate with a plurality of satellites. 
     A communication apparatus according to one exemplary embodiment of the present disclosure includes: an antenna including a base having a dome shape, a first antenna element disposed in a first region including a zenith of the base, and one or more second antenna elements disposed in a second region of the base; and beam forming circuitry that controls, based on position information of a target satellite to communicate with, a beam formation of the first antenna element and the one or more second antenna elements. 
     An antenna according to one exemplary embodiment of the present disclosure has a base having a dome shape, a first antenna element disposed in a first region including a zenith of the base, and one or more second antenna elements disposed in a second region of the base. 
     Note that these comprehensive or specific aspects may be achieved by a system, a device, a method, an integrated circuit, a computer program, or a recording medium, or may be achieved by any combination of the system, the device, the method, he integrated circuit, the computer program, and the recording medium. 
     One exemplary embodiment of the present disclosure enables appropriate communication with a plurality of satellites. 
     Further advantages and effects of one exemplary embodiment of the present disclosure will be apparent from the specification and the drawings. Such advantages and/or effects are provided by characteristics described in several exemplary embodiments, the specification, and the drawings, but all the advantages and/or effects do not need to be provided to obtain one or more of the same characteristics. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram showing one example of functional blocks of a communication apparatus; 
         FIG.  2    is a perspective view showing one example of an antenna device included in the communication apparatus of  FIG.  1   ; 
         FIG.  3    is a diagram showing one example of functional blocks of a communication apparatus according to a first exemplary embodiment; 
         FIG.  4    is a perspective view showing one example of an antenna of the communication apparatus of  FIG.  3   ; 
         FIG.  5    is a diagram showing an example of a polar coordinate (θ k , φ k ) of the k-th element of a conformal array antenna; 
         FIG.  6    is a perspective view showing one example of an antenna according to a second exemplary embodiment; 
         FIG.  7    is a perspective view showing one example of an antenna according to a third exemplary embodiment; and 
         FIG.  8    is a perspective view showing one example of an antenna according to a fourth exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Before describing exemplary embodiments of the present disclosure, problems in a conventional technique will be briefly described. A satellite tracking antenna control device of Unexamined Japanese Patent Publication No. 2002-158525, when communicating with a plurality of satellites, changes an attitude of a satellite tracking antenna with respect to each of the plurality of satellites, which may make appropriate communication difficult. 
     Hereinafter, the exemplary embodiments of the present disclosure will be described in detail with reference to the drawings as necessary. However, an unnecessarily detailed description may be omitted. For example, a detailed description of a well-known item or a redundant description of a substantially identical configuration may be omitted. This is to prevent the following description from being unnecessarily redundant and to facilitate understanding by those skilled in the art. 
     Note that the attached drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter as described in the appended claims. 
     As an antenna device mounted on an aircraft and communicating with a geostationary satellite above the equator, there is known an antenna device that mechanically moves an orientation of a high gain antenna by following positions of the aircraft and the satellite. 
       FIG.  1    is a diagram showing one example of functional blocks of communication apparatus  1 .  FIG.  2    is a perspective view showing one example of antenna device  2  included in communication apparatus  1  of  FIG.  1   . Communication apparatus  1  shown in  FIG.  1    is mounted on, for example, an aircraft. 
     As shown in  FIG.  1   , communication apparatus  1  includes antenna device  2  and transmission and reception unit  3 . Transmission and reception unit  3  communicates with a satellite via antenna device  2 . Further, transmission and reception unit  3  is connected to an external network via interface  4  to acquire position information of the aircraft and the satellite. 
     As shown in  FIGS.  1  and  2   , antenna device  2  has high gain antenna  2   a  and attitude controller  2   b . High gain antenna  2   a  outputs a narrow-beam electromagnetic wave toward a satellite to communicate with. Further, high gain antenna  2   a  receives an electromagnetic wave output from the satellite to communicate with. 
     Attitude controller  2   b  mechanically controls (changes) an attitude (orientation) of high gain antenna  2   a . Attitude controller  2   b , following the positions of the aircraft and the satellite, directs high gain antenna  2   a  in a direction of the satellite to communicate with. The position of the aircraft may include an attitude of the aircraft. 
     Examples of satellites for relaying between an aircraft and an earth station include a satellite that orbits in a geostationary orbit (GEO), a satellite that orbits in a medium earth orbit (MEO), and a satellite that orbits in a low earth orbit (LEO). Further, examples of satellites for relaying between an aircraft and an earth station include satellites having different altitudes and/or moving speeds, such as a high-altitude pseudo satellite. Communication apparatus  1  can provide an appropriate network service by communicating with the earth station via a satellite suitable for the route and area of the aircraft. 
     For example, in order to avoid interference with the adjacent geostationary satellite closely disposed at an interval of a viewing angle of about 1 degree, antenna device  2  mechanically controls an attitude of high gain antenna  2   a  at a speed that follows a moving speed of the aircraft (relatively lower speed than a moving speed in the LEO or the like in the sky). 
     However, in communication with a satellite in the LEO or the like that relatively moves at a higher speed, antenna device  2  is required to control the attitude at a higher satellite tracking speed. High gain antenna  2   a  of antenna device  2  has a large mass in order to obtain a high gain, and has difficulty in controlling the attitude at high speed. Thus, communication apparatus  1  including antenna device  2  may have difficulty in communicating with satellites having different altitudes. Further, communication apparatus  1  including antenna device  2  may have difficulty in communicating with satellites having relative speeds different from a speed of the aircraft (communication apparatus  1 ). 
     First Exemplary Embodiment 
     A communication apparatus described below can appropriately communicate with a plurality of satellites having different altitudes. Further, the communication apparatus can appropriately communicate with a plurality of satellites having different relative speeds. 
       FIG.  3    is a diagram showing one example of functional blocks of communication apparatus  10  according to a first exemplary embodiment.  FIG.  4    is a perspective view showing one example of antenna  11  of communication apparatus  10  of  FIG.  3   . 
     As shown in  FIG.  3   , communication apparatus  10  includes antenna  11 , transmission and reception unit  12 , and beam forming unit (beam forming circuitry)  13 . 
     As shown in  FIGS.  3  and  4   , antenna  11  has conformal array antenna  21  and zenith array antenna  22 . For example, a part outside dotted frame A 1  of antenna  11  shown in  FIG.  4    indicates conformal array antenna  21 . A part within dotted frame A 1  indicates zenith array antenna  22 . Conformal array antenna  21  has a plurality of antenna elements  21   a . Zenith array antenna  22  has a plurality of antenna elements  22   a.    
     As shown in  FIG.  4   , antenna  11  has base  31  having a dome shape. For example, antenna  11  has base  31  having a hemispherical shape. 
     Base  31  may be provided, for example, on a body surface in a plan view of the aircraft. In other words, base  31  may be provided on the body surface of the upper part of the aircraft. Base  31  may be a part of a body of the aircraft and antenna elements  21   a ,  22   a  may be disposed on the body surface of the aircraft. 
     Conformal array antenna  21  is configured by arranging the plurality of antenna elements  21   a  in a region surrounding a region including a zenith of base  31 . For example, zenith array antenna  22  is configured by arranging the plurality of antenna elements  21   a  in a region outside dotted frame A 1  in  FIG.  4   . Conformal array antenna  21  may be regarded as an antenna including a plurality of antenna elements  21   a  arranged on a curved surface. 
     Zenith array antenna  22  is configured by arranging a plurality of antenna elements  21   a  in the region including the zenith of base  31 . For example, zenith array antenna  22  is configured by arranging the plurality of antenna elements  21   a  in a region within dotted frame A 1  in  FIG.  4   . Zenith array antenna  22  may have the plurality of antenna elements  22   a  arranged on a curved surface or the plurality of antenna elements  21   a  arranged on a flat surface. In other words, the part within dotted frame A 1  of base  31  may be a curved surface (part of a hemispherical surface) or a flat surface. 
     Antenna elements  21   a  of conformal array antenna  21  are spirally arranged on a surface of base  31  having a hemispherical shape. For example, where a number of elements is N, antenna elements  21   a  are disposed at a position where a polar coordinate (θ k , φ k ) of the k-th element is calculated by a generalized spiral series. Specifically, antenna elements  21   a  are disposed on the curved surface of base  31  in accordance with the following generalized spiral series formula. 
     
       
         
           
             
               
                 
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       FIG.  5    is a diagram showing an example of a polar coordinate (θ k , φ k ) of the k-th element of conformal array antenna  21 . Antenna elements  21   a  of conformal array antenna  21  are disposed such that element intervals are uniform on the curved surface in accordance with the above generalized spiral series formula. Antenna elements  22   a  of zenith array antenna  22  are disposed in the region including the zenith of antenna  11  (base  31 ), and are disposed at element intervals equivalent to element intervals of conformal array antenna  21 . 
     As described above, antenna elements  21   a  of conformal array antenna  21  are disposed in the region surrounding the region including zenith of base  31  having a hemispherical shape. That is, antenna elements  21   a  of conformal array antenna  21  are disposed over 360 degrees (0°≤θ k ≤360°) around base  31  in a horizontal direction. This allows antenna  11  to emit a beam in any direction around base  31 . 
     On the other hand, antenna elements  22   a  of zenith array antenna  22  are disposed in the region including the zenith of base  31  having a hemispherical shape. The zenith of base  31  having a hemispherical shape has a better peripheral view than other parts of base  31 . As a result, zenith array antenna  22  of antenna  11  is suitable for forming a broad beam. 
       FIGS.  3  and  4    will be referred again. Transmission and reception unit  12  shown in  FIG.  3    converts a digital signal output from beam forming unit  13  into an analog high frequency signal. Transmission and reception unit  12  amplifies the converted analog high frequency signal to a predetermined power level and outputs the signal to antenna elements  21   a ,  22   a.    
     For example, transmission and reception unit  12  converts the digital signal output from beam forming unit  13  into a band-limited analog intermediate frequency (IF) signal with a digital-to-analog converter (DAC). Transmission and reception unit  12  converts the analog IF signal into a band-limited signal in a transmission frequency band with an up converter. Transmission and reception unit  12  amplifies the power of the frequency-converted signal with a power amplifier (PA). Transmission and reception unit  12  outputs the power-amplified signal to antenna elements  21   a ,  22   a  via a duplexer (DPX). The duplexer is a device for sharing antenna elements  21   a ,  22   a  between transmission and reception. 
     Transmission and reception unit  12  converts reception signals received by antenna elements  21   a ,  22   a  into low noise digital signals. 
     For example, transmission and reception unit  12  band-limits the reception signals received by antenna elements  21   a ,  22   a  with the duplexer, and then amplifies the signals with a low noise amplifier (LNA). Transmission and reception unit  12  frequency-converts the amplified reception signals into band-limited analog IF signals with a down converter. Transmission and reception unit  12  converts the analog IF signals into digital signals with an analog-to-digital converter (ADC). 
     Beam forming unit  13  acquires position information such as coordinates of the aircraft and the satellite from an external network connected via interface  14 . The position information of the aircraft may be acquired by using, for example, a global positioning system (GPS). The coordinate of the satellite and other information may be acquired in advance from, for example, a service company that provides the position information of the satellite. The position information of the aircraft may include an attitude of the aircraft. 
     Beam forming unit  13  forms a beam for the satellite to communicate with. For example, beam forming unit  13 , using the acquired position information, calculates a weight having a suitable tracking characteristics for the satellite to communicate with. Beam forming unit  13  gives (multiplies) the calculated weight to a transmission signal transmitted to the satellite and a reception signal received from the satellite. 
     More specifically, beam forming unit  13  generates a digital signal by giving a weight w_Txk for the k-th antenna element to a transmission baseband signal Tx. Further, beam forming unit  13  gives a weight w_Rxk to the digital signal of the signal received from the satellite, which is output from transmission and reception unit  12 , and synthesizes the digital signal to generate a reception baseband signal Rx. 
     Beam forming unit  13  forms a narrow beam using conformal array antenna  21  for a geostationary satellite, for example. Alternatively, beam forming unit  13  forms a narrow beam for the geostationary satellite, for example, using conformal array antenna  21  and zenith array antenna  22 . 
     Beam forming unit  13  forms a broad beam using zenith array antenna  22  for a satellite in the LEO or the like having a high relative speed. For example, beam forming unit  13  forms a beam having a wider beam width than a narrow beam for the geostationary satellite with respect to a satellite that orbits at a relative speed equal to or higher than a predetermined value. The relative speed may be calculated from the positions of the aircraft and satellite. 
     Beam forming unit  13  forms a broad beam using zenith array antenna  22  for a satellite having a low altitude, for example. For example, beam forming unit  13  forms a broad beam using zenith array antenna  22  for a satellite having a lower altitude than an altitude of the geostationary satellite. 
     Beam forming unit  13  may calculate the weight of conformal array antenna  21  that spreads the beam of zenith array antenna  22 . For example, beam forming unit  13  may form a broad beam by calculating the weight of conformal array antenna  21  that disperses transmission power of antenna element  22   a.    
     The following formula shows an example of calculation of the weight w_Txk when signals are transmitted from antenna elements  21   a ,  22   a  of the k-th element for directivity D (θ_0,φ_0) for the satellite to communicate with.
 
 w   Txk   ∝∫∫D (θ 0 ,ϕ 0 )exp( jk   0   v   k ( · {circumflex over (R)} (θ 0 ,ϕ 0 ))) dθ   0   dϕ   0  
 
     As described above, antenna  11  of communication apparatus  10  has base  31  having a dome shape, antenna elements  22   a  (first antenna elements) disposed in a first region including the zenith of base  31  (for example, the area within dotted frame A 1  in  FIG.  4   ), and the plurality of antenna elements  21   a  (second antenna elements) disposed in a second region surrounding the first region (for example, the region outside dotted frame A 1  in  FIG.  4   , a region excluding the first region). Beam forming unit  13  of communication apparatus  10  calculates a weight based on the position information of the satellite to communicate with, and multiplies the signals transmitted and received by the antenna elements  21   a  and  22   a  by the weight. 
     Note that the multiplication of the weight also includes setting one of the first antenna elements or the second antenna elements to 0. 
     Further, although an example has been described in the present exemplary embodiment where control is done separately for the first region and the second region, control may be done separately for more regions (regions of N). 
     This allows communication apparatus  10  to appropriately communicate with a plurality of satellites. For example, communication apparatus  10  forms a narrow beam corresponding to the position and attitude of the aircraft for the geostationary satellite and a wide beam for the satellite orbiting in the LEO or the like without moving the antenna to appropriately communicate with the satellites. 
     Further, communication apparatus  10  can flexibly cope with communication with satellites having different altitudes and relative speeds by controlling beams suitable for satellites to communicate with and adapting to different tracking characteristics for each satellite. For example, communication apparatus  10  can flexibly cope with communication with geostationary satellites and communication with satellites in the LEO, MEO, GEO, and the like. 
     Further, communication apparatus  10  can simultaneously communicate with a plurality of satellites. For example, communication apparatus  10  can simultaneously communicate with a plurality of satellites by using different beams. 
     In the above, an example has been shown in which antenna elements  21   a  of conformal array antenna  21  are disposed in the polar coordinate of the generalized spiral series formula. However, an offset corresponding to, for example, a position where antenna  11  is installed may be added to the polar coordinate. 
     Electromagnetic waves transmitted and received by antenna  11  may be either linearly polarized waves or circularly polarized waves. Antenna  11  sharing two orthogonal polarized waves can improve communication performance. 
     Further, in the above description, the number of antenna elements  22   a  of zenith array antenna  22  is plural, but the number is not limited thereto. The number of antenna elements  22   a  of zenith array antenna  22  may be one. Communication apparatus  10  may be paraphrased as an antenna device. 
     Further, although the hemispherical shape is illustrated as one example of the shape of base  31 , the shape is not limited thereto. Base  31  may have a vertically long semi-elliptical shape. Base  31  may have a horizontally long semi-elliptical shape. That is, the dome shape of base  31  may include a shape having a zenith and a curved surface such as a hemispherical shape, a vertically long semi-elliptical shape, and a horizontally long semi-elliptical shape. 
     Second Exemplary Embodiment 
     The conformal array antenna may have antenna elements on a cylindrical side surface. 
       FIG.  6    is a perspective view showing one example of antenna  41  according to a second exemplary embodiment. In  FIG.  6   , identical reference numerals designate identical components to components in  FIG.  4   . 
     As shown in  FIG.  6   , a lower part of base  31  has a cylindrical shape. For example, base  31  below dotted line A 11  in  FIG.  6    has a columnar shape. That is, base  31  has a cylindrical shape, and has a hemispherical shape at one end of the cylindrical shape. 
     Antenna elements  21   a  of conformal array antenna  21  are also disposed in the cylindrical part of base  31 . The cylindrical part of conformal array antenna  21  (part below dotted line A 11  in  FIG.  6   ) may be referred to as a cylinder array antenna. 
     Antenna elements  21   a  in cylinder array antenna  42  shown in  FIG.  6    are disposed so as to be continuous with antenna elements  21   a  disposed in the hemispherical part of base  31 . For example, antenna elements  21   a  on cylinder array antenna  42  are disposed based on the above generalized spiral series formula. Antenna elements  21   a  in cylinder array antenna  42  may be disposed at equal intervals in a cylindrical coordinate system. 
     As described above, conformal array antenna  21  (antenna  41 ) may partially include cylinder array antenna  42 . This also allows communication apparatus  10  to properly communicate with a plurality of satellites. 
     For example, communication apparatus  10  compensates a decrease in an opening of antenna  41  even when the geostationary satellite is located in a direction at low elevation angle during a high-altitude travel of the aircraft because antenna  41  has cylinder array antenna  42 . 
     Third Exemplary Embodiment 
     The antenna elements may be bullseye antenna elements having a concentric antenna structure. 
       FIG.  7    is a perspective view showing one example of antenna  51  according to a third exemplary embodiment. In  FIG.  7   , identical reference numerals designate identical components to components in  FIG.  4   . 
     As shown in  FIG.  7   , conformal array antenna  21  of antenna  51  has a plurality of bullseye antenna elements  52 . Bullseye antenna elements  52  may be disposed based on the above generalized spiral series formula. 
     Zenith array antenna  22  of antenna  51  has bullseye antenna element  53 . In the example of  FIG.  7   , zenith array antenna  22  has one bullseye antenna element  53 , but may have a plurality of bullseye antenna elements. 
     As described above, conformal array antenna  21  may have bullseye antenna elements  52 . Zenith array antenna  22  may include bullseye antenna element  53 . Bullseye antenna elements  52 ,  53  have higher directivity gain than patch antenna elements, and therefore communication apparatus  10  can form a beam with a smaller number of elements. 
     The bullseye antenna element may be applied to antenna  41  having cylinder array antenna  42  described in the second exemplary embodiment. 
     Fourth Exemplary Embodiment 
     The antenna may have soft boundaries. 
       FIG.  8    is a perspective view showing one example of antenna  61  according to a fourth exemplary embodiment. In  FIG.  8   , identical reference numerals designate identical components to components in  FIG.  7   . 
     As shown in  FIG.  8   , antenna  61  has soft boundaries  62 . Soft boundaries  62  are formed between bullseye antenna elements  52 ,  53  formed on the surface of base  31 . 
     Soft boundaries  62  are configured by, for example, a corrugated structure including a plurality of grooves. A depth of the grooves of the corrugated structure is, for example, ¼ of a wavelength of an electromagnetic wave of the transmission signal or the reception signal. 
     As described above, antenna  61  may have the soft boundaries between bullseye antenna elements  52 ,  53 . This suppresses interference between bullseye antenna elements  52 ,  53 , and communication apparatus  10  can improve accuracy of beam formation. 
     Soft boundaries  62  are not limited to the corrugated structure. Soft boundaries  62  may have a structure having a function of adjusting a boundary impedance of antenna  61  with respect to the surface wave, for example. For example, soft boundary  62  may be formed on the surface of base  31  by a structure having a function of adjusting the boundary impedance such as a frequency selective boundary or a metamaterial. 
     Soft boundary  62  may be applied to antenna  11  described in the first exemplary embodiment and antenna  41  described in the second exemplary embodiment. 
     In the above exemplary embodiments, the notation “unit” used for each component may be replaced with another notation such as “circuit (circuitry)”, “device”, “unit”, or “module”. 
     Although the exemplary embodiments have been described with reference to the drawings, the present disclosure is not limited to the examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims. It is understood that such changes or modifications also belong to the technical scope of the present disclosure. Further, the components in the exemplary embodiments may be arbitrarily combined without departing from the gist of the present disclosure. 
     The present disclosure can be achieved by software, hardware, or software linked with hardware. The functional blocks used for describing the exemplary embodiments are partially or wholly achieved as a large-scale integration (LSI) as an integrated circuit. Each process described in the exemplary embodiments may be partially or wholly controlled by one LSI or a combination of LSIs. The LSI may be configured by individual chips, or may be configured by one chip so as to include some or all of the functional blocks. The LSI may include data input and output. The LSI may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on an integration degree. 
     A method of circuit integration is not limited to the LSI, and may be achieved by a dedicated circuit, a general-purpose processor, or a dedicated processor. A field programmable gate array (FPGA) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure connection and setting of circuit cells inside the LSI may be used. The present disclosure may be implemented as digital processing or analog processing. 
     Further, if integrated circuit technology emerges to replace LSIs as a result of advancement of semiconductor technology or another derivative technology, the functional blocks may well be integrated using such a technology. An application of biotechnology or the like is possible. 
     The communication apparatus according to the present disclosure is not limited to being mounted on an aircraft, but can be applied to any flying body such as an unmanned aerial vehicle or a drone. Further, as long as the communication apparatus communicates with a satellite, the communication apparatus can be applied to a mobile body on the ground. 
     The communication apparatus according to the present disclosure has flexible tracking performance that corresponds to one or both of the altitude and the relative speed of a satellite, and is useful as a communication apparatus that provides, for example, an internet connection service in an aircraft. Further, the communication apparatus of the present disclosure can be applied to communication with a ground earth station.