JP2611528B2 - Space antenna system - Google Patents

Abstract

A multiple beam space antenna system for facilitating communications between a satellite switch (100) and a plurality of earth-based stations (1,a,b,) is shown. The antenna is deployed after the satellite is in orbit by inflation of a raft-type supporting structure which contains a number of antenna horns (80). These antenna horns are oriented in substantially concentric circular groups (A-D) about a centrally located antenna horn (80). Each of the antenna beams projects an area on the earth. Each of the areas (a,b) of the beams are contiguous. As a result, one large area is subdivided into many smaller areas to facilitate communications. In addition, a lens (FIG. 7C and 7D) may be employed to focus the beams of the horn antennas.

Description

Description: FIELD OF THE INVENTION The present invention relates to an antenna system for a spacecraft, and more particularly to a deployable projecting multiple beam pattern such that each beam covers a discontinuous area. Related to simple antenna array systems.

BACKGROUND OF THE INVENTION Generally, spacecraft communicate (ie, "uplink" and "downlink") with earth base stations by projecting a spot beam onto an area. Such systems include, but are not limited to, ground base stations, waterborne base stations located on board ships, and base stations on aircraft or other spacecraft. , A relatively narrow or divergent beam.
It is easy to focus on known earth base sources. In the case of communications where many sources are located randomly with respect to parts of the earth, the entire area of the earth must be covered by this antenna system.

(Problems to be Solved by the Invention) In the case of communication using a satellite having many earth base stations, there is a limit on the communication frequency, that is, the number of channels. Spatial diversity (diversity) exists between the beams of the satellite antenna.
ity) is required. Thus, satellite communications with multiple earth stations are limited by the number of antenna beams (or cells) projected by the antenna system. As the number of cells increases, spatial diversity becomes more difficult to maintain.

Also, it is difficult to launch many satellite antennas into space. Furthermore, once the launch vehicle is in the correct orbit, it is difficult to locate and place many antennas in space.

Accordingly, it is an object of the present invention to provide a uniform size spot for communication between a satellite and a plurality of earth base stations.
Is to provide a beam.

In realizing the object of the present invention, a space antenna system capable of deploying a novel multiple beam is shown.

SUMMARY OF THE INVENTION A multiple beam space antenna system communicates between a satellite and a plurality of earth stations. The multi-beam space antenna system has a plurality of spherically arranged antennas. Each of the plurality of antennas is arranged such that each antenna communicates with a substantially different region of the earth.

Each of the antennas receives a plurality of communications from the earth station. Each of the antennas also transmits multiple communications from the satellite to the earth station. Each of the antennas is connected to a satellite processor, which allows the processor to receive and transmit messages from multiple earth stations.

The above and other objects, features and advantages of the present invention are:
A better understanding may be had from the following detailed description, taken in conjunction with the accompanying drawings.

(Examples) Japanese Patent Application No. Hei 1-278777 filed by the applicant of the present invention, Patent Application (3) filed on September 5, 1990, Patent Applications (2) and (3) filed on the same date as the present application, and US Patent Application No. 07 The disclosure and teachings of / 414494 are hereby incorporated by reference.

FIG. 1 shows a satellite 100 projecting a multi-beam space antenna array. The satellite 100 has a processing device (not shown) for transmitting and receiving communication. Each hexagonal area as indicated by reference numeral 1 represents an individual cell projected by the antenna beam. This projection indicates that cell 1 is surrounded by three consecutive larger rings of cells of the same shape. Those cells actually projected by the beam of the satellite 100 for communication are elliptical in nature. These cells shown in FIG. 1 are the result of crossing elliptical antenna beams. The six sides of each hexagon are the chords that separate each cut side of the elliptical beam.

In such a configuration, 37 beams would be projected by the satellite 100 antenna system. Each of the 37 antennas is electrically and optically connected to a satellite processor. Since a satellite represents one point in space and the surface of the earth is spherical, each of the cells needs to represent approximately the same area.

Each of the cells represents a plurality of frequencies around a center frequency. This assists in communicating between satellite 100 and multiple users of a particular cell on the earth. Since the satellite is in orbit around the earth, as the satellite moves in orbit, the communication link between the user of one cell and satellite 100 must be handed over to another adjacent cell. This cell frequency assignment is made to use groups of four fundamental frequencies. A particular one of these four fundamental frequency groups is the central cell 1
Selected for the region. Then, two adjacent cells are 4
The assignment is made circular around cell 1 so as not to use the same of the two frequency groups. This provides spatial diversity and allows for frequency reuse between groups.

The 37 cells of FIG. 1 can be represented in plan view as shown in FIG. The innermost ring A of the "target" (multiple concentric circles of multiple rings) of FIG. 2 represents the central cell 1 of FIG. Next, the ring outside the central cell A is ring B. Ring B surrounds central cell 1
With two cells. The ring adjacent to ring B is ring C. Ring C has twelve cells surrounding ring B. The last ring surrounding ring C is ring D. Ring D has 18 cells surrounding ring C.
As a result, a total of 37 satellite projections separate the cells, providing an area covering the communication uplink and communication downlink to the satellite.

Each cell represents 1/37 of the total area of the entire cell pattern projected by a particular satellite. FIG. 3 represents the entire area from the satellite to the earth's surface. FIG. 3 is a side view showing the elevations of the various rings shown in FIG. That is, region 4 corresponds to ring A, region 3 corresponds to ring B, region 2 corresponds to ring C, and region 1 corresponds to ring D.
Corresponding to The total area of the satellite projection is the formula, area = 2π
It can be calculated by rh, where r is the radius, h is the height of the sphere's arc, and π is about 3.14159.

The area of each ring is shown in FIGS. 2 and 3, and the total area can be calculated by the following equation:

Total area = 2πrh Area 1 = 2πr (h−h ₁ ) Area 2 = 2πr (h ₁ −h ₂ ) Area 3 = 2πr (h ₂ −h ₃ ) Area 4 = 2πrh ₃ FIG. Shows the geometry of a particular satellite in orbit over 413 nautical miles. When viewed from the satellite, the second
Assume that the outer end of ring D shown cuts the earth at an angle of 10 degrees. This 10 degree angle 40 is called a "mask angle".
Satellite 45 is shown at about 413 sea stars above the Earth's surface. As shown in FIG. 2, the distance from the satellite 45 to the outer end of the ring D
46 is about 1,243 sea stars, as shown in FIG. The angle between the earth's surface and the line from the end of the outer ring D to the satellite 45 is angle 40. This angle is a mask angle of 10 degrees.

Angle 41 is about 100 degrees. Angle 41 comprises a mask angle of 10 degrees and a tangent angle of 90 degrees. This 90 degree tangent angle (angle 41
The angle 40) is constituted by the line segment 46 from the center of the earth to the earth's surface and the tangent of the earth's surface at that point (not shown). The angle 43 is an angle constituted by a line segment 48 between a line segment 47 from the satellite to the center of the earth and a point of the outermost ring D from the center of the earth. This angle is about 18.45 degrees. The distance from the center of the earth to the earth's surface is about 3,443 sea stars, as shown by segment 47 in FIG.

The angle 42 is an angle between the line segment 46 and the line segment 47. line segment
46 is a line segment of 1,243 sea stars between the satellite 45 and the outer end of the cell projection ring D. Line segment 47 is a line that terminates at the center of the earth at right angles to the earth's surface from satellite 45. 4th
In the case of the present configuration shown in the figure, the angle 42 is about 61.55 degrees.

Referring again to FIGS. 1 and 2, the center of each of the six cells in ring B is equidistant from the center of the central cell 1 (ring). The same does not hold for the distance between the center of each cell and the center of the center cell 1 with respect to the rings C and D.

Referring to FIG. 1, cell "a" is closer to the center of cell 1 than cell "b". Both cells a and bh are located in cell ring C. This C-ring contains 12 cells. The cells “a” and “b” are alternately changed around the ring C. That is, ring C has "a" cells and "b" cells alternately.

Similarly, ring D composed of 18 cells is
It has "A" cells and "B" cells. Each of cells A is equidistant from the center of cell 1. Each of the cells B is also equidistant from the center of the associated cell 1. However, cell A is closer to the center of cell 1 than cell B. Regarding the ring D of the cell shown in FIG. 1, the patterns of the “A” cell and the “B” cell are different from the “a” cell and the “b” cell of the ring C. Ring D
Has a pattern of one cell B followed by two cells A. This pattern is continuous around the ring D.

In positioning each antenna of the satellite antenna system, the angular difference between the satellite "a" and "b" cells or the "A" and "B" cells must be considered. For the purpose of further discussion, the ab and AB deviations discussed above are not considered. But,
The positioning indications obtained here must be slightly modified to account for these deviations from a particular altitude point of the satellite in orbit.

For further discussion, consider that rings C and D have each cell equidistant from the center of cell 1. For a satellite at an altitude of 413 nautical miles (N. Miles) on Earth, Table 1 summarizes the resulting antenna angles for the 37 cells of FIG. The central cell is a single cell, cell 1
Is a ring A of a cell constituted by The size of this cell is a circle about 41.5 degrees to the satellite. This antenna produces a gain of about 13.8dB. Generally, the maximum theoretical gain represented by an antenna with a gain of x radians (vertical) and y radians (horizontal) is calculated. The formula for this gain is given as:

Gain (dB) = 10 × log (4π ÷ xy) The loss r ² is a loss due to the distance of the satellite from the earth.
This loss increases in proportion to the square of the distance. Finally,
The mask angle represents the value of the distance from the ground to the line of sight from a satellite in a cell of a particular ring. Ring A has only one cell.

The first actual ring of cells in Table 1 is ring B, as shown in FIG. The second and third rings in Table 1 correspond to rings C and D, respectively, in FIG.

Table 2 shows the first for satellites at 490 sea stars above Earth.
FIG. 3 shows similar parameters for each of the cells shown in FIG. 2 and FIG. Note that these parameters when the satellite altitude increases are not substantially different from the examples given in Table 1.

Referring to Table 1, the antenna in the third ring, Ring D, requires a 7.9 degree projection. As a result, an opening of about 4 meters is required. A small satellite or spacecraft is typically a cylinder 2 meters high and about 1.5 meters in diameter. This antenna array system has a diameter of about 1
It can be transported by satellite with a canister 0.3 meters high by 0.3 meters.

FIG. 5 is a cross-sectional view of the antenna array of the present invention. FIG. 5 shows horn antennas 50-56. These horn antennas represent the antennas of each of the four rings AE described in FIG. The horn antenna 50 represents the central cell 1 shown in FIGS. Horn antennas 51 and 52 represent the two antennas in ring B shown in FIG. Horn antennas 53 and 54
2 represents two of the twelve antennas in ring G of the system. Finally, horn antennas 55 and 56 represent two of the eighteen antennas in ring D of the antenna system.

First, note that these antenna horns are arranged in a spherical configuration by the antenna horn 50, which is in the center of the sphere portion and becomes the central cell. Second, note that the length of this horn antenna increases as we move from the central antenna 50 to the ring B antennas 51,52. Similarly, the dimensions of the ring C horn antennas 53 and 54 are the same as those of the ring B horn antennas 51 and 54.
Increase to 52 or more. Similarly, the ring B horn antennas 55, 56 are longer than the ring C horn antennas 53, 54.

From the sectional view in FIG. 5, these antenna horns are:
It can also be seen that the cell projection shown in FIG. The longest horn is the ring D horn. As exemplified by horns 55 and 56,
The horn of ring D requires an opening approximately 4 meters long. The structure of these horns themselves is a metal-coated mylar. This antenna horn can be implemented as a mylar structure molded into a sphere. This structure can be folded into a canister before placement in space. The antenna system can be arranged in a manner similar to that of an inflatable rubber raft. That is, when the satellite is in place in space, this antenna is deployed by propulsive expansion to make the antenna system spherical in shape as a horn antenna.

FIG. 6 is a two-dimensional view of the horn antenna structure when arranged. FIG. 6 shows the horn antennas 50-56 of FIG. 5 when looking directly up from the bottom of the satellite.
FIG. 6 shows that the field of view from the satellite to the earth is the same in either direction. Horn antenna 50 looks like a circle. The antennas 51 to 56 appear elliptical because they are inclined at an angle.

FIG. 7A shows the canister described above, which has a horn antenna structure folded inside. When the horn antenna expands, it has the appearance shown in FIG. 7B. From this figure, as in Figure 5, the length of the central horn antennas is the shortest, and the length of these horns increases as they move away from the central horn antenna of the structure. I understand. The diameter of the entire antenna system, ie, the outer diameter of ring D, is about 2 feet.

Since the transmissions by the antennas propagate far and these transmissions also generate side lobes, a lens configuration can be employed to suppress the side lobes and limit signal spreading. FIG. 7C shows the bootlace lens in a folded position that can be used to suppress sidelobes and limit diffusion. This boot race (boot
lace) The lens is a flat lens. The bootlace lens is placed in front of the horn antenna structure so that signals transmitted from or received by the antenna must pass through the flat lens. Figure 7D shows the appearance of this bootlace lens. This bootlace lens cannot be placed in a manner similar to the basic horn antenna structure. That is, the lens cannot be expanded. This boot race lens requires mechanical tuning. As a result, the boot race lens can be made of a rigid material that is placed on a flat portion similar to the solar array of a satellite.

FIG. 8 shows one typical horn 80 of the multi-horn antenna array shown in FIG. 7B. Horn antenna
80 has an inflatable frustoconical mylar structure 81. The inner surface of mylar cone 81 is metallized with a conductive layer 82.
This conductive layer or film can be formed of a metal such as gold or aluminum. Mounted on the Myra cone is a valve 83. The valve 83 provides for proper positioning of the conical structure 80 by inflation. Other valves (not shown) are provided to inflate the aforementioned support rubber raft structure. Valve 83 is connected to a source of gas (not shown) that is used to inflate the mylar structure when the antenna system is deployed in space. Propellants such as nitrogen or foam can be used for expansion.

An elongated platelet for the waveguide transition 87 is connected to the dielectric substrate 85 via an opening 88 at the bottom of the cone. The dielectric substrate 85 is used to electrically isolate the input signal and the output signal and to provide the MMIC circuit 84
It is provided for mounting. The elongated platelets for the waveguide transition 87 are provided for receiving and transmitting signals from a radio, telephone or similar device located on the earth. The input signal is transmitted from the waveguide structure 87 to the MMIC circuit.
Sent to 84. An MMIC circuit 84 receives and transmits signals, and a satellite processor (not shown) via optical fiber 86.
An optical signal is generated at its output for transmission to or from the. It is also possible to use a coaxial cable instead of the optical fiber 86.

FIG. 9 shows a block diagram of the MMIC 84 (microwave monolithic integrated circuit) of FIG. Optical fiber 90 is connected to low noise level amplifier 91. Amplifier 91 is connected to power amplifier 92. Amplifier 92 is connected to circulator 93. The circulator 93 is connected to the microstrip of the waveguide transition 87. Microstrip waveguide
88 is connected to the horn antenna. The input signal is transmitted to the microstrip 87. These signals are then transmitted via circulator 93 to diplexer 94. The circulator 93 is also connected to a diplexer 94. The diplexer 94 is an LNA (Low Noise Amplifier).
plifier) 95. LNA 95 is connected to filter 96. The filter 96 is connected to the amplitude modulation LED 97. An optical fiber 98 electrically connects the optical device 97 to the satellite processor.

The optical signal is transmitted to the FET amplifier 91 via the optical fiber 90. The FET amplifier 91 converts the optical signal into an electric signal, and transmits the electric signal to the MMIC power amplifier 92. Amplifier 92 generates an amplified signal, which is transmitted via circulator 93 to microstrip 87. The circulator 93 can also be constituted by a waveguide having a magnet. The circulator 93 transmits a signal from the input connection point to the output connection point in a clockwise direction. In the counterclockwise direction, signals from the input connection are blocked. These signals are then transmitted to the earth base station via the horn.

The input signal is a microstrip 87 and a distributor 93.
Is transmitted to the diplexer 94 via Diplexer 94
Acts as a filter and removes transmission frequencies or other unwanted frequencies. LNA95 amplifies this signal. This incoming signal is then filtered by filter 96. The filtered signal is transmitted electrically to an amplitude-modulating LED 97, which amplifies the signal and then modulates the amplitude by superimposing it on the bias line of a diode laser, light emitting diode or other similar device. Is done. This electrical signal is converted to an optical signal and transmitted over fiber 98 by a satellite processor. This FET amplifier 91 can be realized by a gallium arsenide FET. When photons of this light enter this type of device,
Modulation occurs in the gate voltage of the FET. MMIC amplifier 92 can be implemented by a gallium arsenide MMIC amplifier.

While the preferred embodiment of the invention has been illustrated and described in detail, it will be readily apparent to those skilled in the art that various modifications may be made without departing from the spirit of the invention or the scope of the appended claims. to understand.

[Brief description of the drawings]

FIG. 1 shows the projection of the antenna beam of the satellite constituting the present invention. FIG. 2 is a plan view of the projection of the antenna beam onto the earth. FIG. 3 is a side view of the antenna beam projection shown in FIG. FIG. 4 shows the intercept angle formed by the satellite antenna beam. FIG. 5 shows the antenna horn part of the present invention. FIG. 6 is a two-dimensional representation of the antenna horn system of the present invention. 7A to 7D show a horn structure and a lens structure in which the present invention is arranged. FIG. 8 is a diagram of one particular horn of the antenna system of the present invention. FIG. 9 is a block diagram of the monolithic microwave integrated circuit (MMIC) shown in FIG. 40 ... mask angle, 50, 51, 52, 53, 54, 55, 56 ... horn antenna, 80 ... horn array, 81 ... inflatable frustoconical mylar structure, 82 ... conductive Layer, 83 …… Valve, 84 …… MM
IC circuit, 85 ... dielectric substrate, 86, 90, 98 ... optical fiber,
87: Waveguide transition, 88: Opening, 91: Low noise
Level amplifier, 92: Power amplifier, 93: Circulator, 94: Diplexer, 95: Low noise amplifier, 96:
Filter, 97: Amplitude modulation LED, 45, 100: Satellite.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication H01Q 25/00 H01Q 25/00 (72) Inventor Kenice Maynard Peterson Uni, Tempe, Arizona, United States of America To A, South Lakeshore Drive 6508 (56) References JP-A-63-193702 (JP, A) JP-A-62-16631 (JP, A) JP-A-62-219726 (JP, A) ) JP-A-63-95703 (JP, A)

Claims (10)

(57) [Claims] 1. A multi-beam space antenna system for communicating between a satellite and a plurality of earth stations, the multi-beam space antenna system comprising: a plurality of antennas arranged hemispherically around the satellite surface. Means, wherein each antenna means comprises a plurality of antenna means arranged to communicate with substantially different regions of the earth, said plurality of antenna means comprising: a plurality of circularly arranged first A plurality of second antenna means arranged in a circle around the plurality of first antenna means; and a plurality of third antenna means arranged in a circle around the plurality of second antenna means. Wherein each of said antenna means receives a plurality of communication signals from an earth station in a communication area, and transmits a plurality of communication signals to an earth station in said communication area. And wherein each antenna means, connected to said processing unit in the satellite, said processing unit, multiple beam space antenna system characterized in that to enable reception and transmission of messages from a number of earth stations. 2. The multi-beam space antenna according to claim 1, wherein said plurality of first antenna means include antenna means disposed centrally with respect to said plurality of first, second, and third antenna means. system. 3. The antenna means and each of the plurality of first, second and third antenna means radiates a beam to a communication area, so that the antenna means, the plurality of first antenna means, Beams emitted by the plurality of second antenna means and the plurality of third antenna means are continuous beams over a wide range, and receive and transmit a plurality of signals between an earth station and the satellite. A multi-beam space antenna system according to claim 2. 4. The antenna unit, the plurality of first antenna units, the plurality of second antenna units, and the plurality of third antenna units, for performing communication between the satellite and the plurality of earth stations. 4. The multi-beam space antenna system according to claim 3, wherein the multi-beam space antenna has a substantially concentric circular area. 5. The antenna means comprises horn antenna means; the plurality of first antenna means comprises a plurality of first horn antenna means; the plurality of second antenna means comprises a plurality of horn antenna means; 5. The multiple beam space antenna system according to claim 4, comprising: a second horn antenna means; wherein the plurality of third antenna means comprise a plurality of third horn antenna means. 6. An inflating means for supporting each of said horn antenna means, wherein said supporting inflating means and each of said horn means expand to make said plurality of horn antenna means hemispherical. 6. An arrangement according to claim 5, wherein
A multiple beam space antenna system as described. 7. A plurality of horn antenna means, further comprising lens means disposed between said plurality of horn antenna means and a surface of said beam irradiating said communication area, said lens means comprising: 7. The multi-beam space antenna system according to claim 6, wherein the focus of said beam is adjusted. 8. Each of the horn antenna means includes: a frusto-conical means having a truncated portion for projecting the beam into the area to be communicated; a covering means provided on the inner surface of the frusto-conical means; Waveguide means positioned at the center of the truncated portion of the frusto-conical means for converting an electrical signal to an RF signal and for converting an RF signal to an electrical signal; Circuit means for interfacing signals between the processing device and the waveguide means; and coupled between the circuit means and the processing device in the satellite, between the circuit means and the processing device. 8. The multi-beam space antenna system according to claim 7, further comprising: connection means for transmitting a signal by: 9. The circuit means comprises: low level amplifier means coupled to the processing device for converting an optical signal to an electrical signal; power amplifier means coupled to the low level amplifier means; Circulator means having three input / output ports for transmitting a signal from an input port to an output port only in a clockwise direction; and wherein said waveguide means is coupled to said circulator means. 9. The multi-beam space antenna system of claim 8. 10. The circuit means includes: a diplexer means coupled to the circulator means for passing only received signals; a low noise amplifier coupled to the diplexer means; a filter means coupled to the low noise amplifier; 10. The multi-beam space antenna system according to claim 9, further comprising: amplitude modulation means coupled between the filter means and the processing unit of the satellite.