JPH1079696A - Static communication satellite system having reconstructable service area - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reconstruct at low cost and lightweight antenna coverage in a specific area on ground by connecting a receiving switch matrix to a beam former connected to a receiving element array and selecting a beam port by a switch controller connected to the switch matrix. SOLUTION: A communication payload 22 in a static satellite system 20 receives an active beam signal to be sent to a transmitting switch matrix 24 and selects a beam command to be outputted to a switch controller 23. The controller 23 receives the beam command and selects plural beam ports for orthogonal beam formers 26, 27. The matrix 24 receives active beam signals from the former 26 and a transmitting phase adjusting array 28 for transmitting a radio frequency(RF) signal. A receiving matrix 25 receives a signal from the former 27 and transmits plural active beam signals to the payload 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to satellite communication systems and, more particularly, to a multi-beam phasing array capable of reconstructing a service area.
ed array) related to a geostationary communication satellite system having an antenna.

[0002]

2. Description of the Related Art Geosynchronous Earth Orbit (GSO)
All satellites on earth orbit) share two important characteristics. First, the satellite remains almost stationary with respect to the earth's surface, and second, the satellite has the entire hemisphere in the radio field of view. The first of these features, "stationary"
Is the origin of the GSO name, and has been used extensively since the first satellite was put on the GSO. However, the use of a hemispherical field of view has been hindered by the degree achievable by practical antenna systems.

[0003] Conventional satellite communication systems utilize antennas that form each antenna beam in a dedicated feed structure. These feeds utilize passive microwave circuit technology (generally waveguides) and are therefore quite large and heavy, at least on a satellite basis where size and weight are at a premium. Traditionally, GSO satellites were created to form a small number of beams to take advantage of their large field of view. Each beam covered a very large land area, often with one beam covering almost the entire continent. Because, by definition, large beams have low antenna gain (ie, diversity), these large beams required high power transmitters on satellites and very large antennas on fixed base stations. Earth terminal antenna is 4-5 for Ka band
Meters, and up to tens of meters at lower frequencies.

[0004] The trend in satellite communications is that of a very small satellite earth terminal (VSAT).
) And microsatellite earth terminal (USAT: ultra small)
satellite earth terminal). These terminals are small and therefore utilize relatively low gain antennas. For practical reasons (eg, cost, security, uplink / downlink balance), most of the lost earth terminal gain cannot be compensated for by higher power transmitters. The satellite must compensate for the lost earth terminal gain by increasing the gain of the satellite antenna, which of course reduces the area covered by each beam.

[0005]

Conventional antenna technology is limited by available size and weight to a maximum of about 100 beams, although fewer beams are preferred.
This is due to the size, weight and power of the transmitter power amplifier as well as the size and weight of the antenna and feed structure. In conventional antenna systems, each beam has a dedicated power amplifier, and these amplifiers are operated at relatively high power to minimize the number of beams required. Traveling-wave tube amplifier (TWTA: traveling-
Wave-tube amplifiers are commonly used as such amplifiers, despite their higher weight and lower reliability than solid state amplifiers.

The Ka band (ie, 20 GHz downlink / 30 GHz uplink) covers the entire field of view from a GSO satellite when the beam is dimensioned to operate on a low power earth terminal utilizing an antenna of one meter or less. Requires about 500-1000 beams. A practical conventional satellite antenna system is about 100
Because the beam can be formed, it covers only about 10% of the field of view. Thus, the market area to be covered must be predetermined and the satellite antenna must be custom designed for a particular combination of orbital position ("slot") and service area. This method has at least four disadvantages. First, in a liquid and uncertain market, there is a risk that service locations will be selected incorrectly, resulting in poor financial performance. Second, even if the area is initially correct, there is a risk that the market in service demand will move away from the selected area before the market has evolved and the useful life of the satellite has expired. Third, a reserve must be built for every orbital position and antenna combination (which is extremely expensive), or the reserve cannot be completed until a failure occurs (resulting in an extended outage). Finally, because each satellite must be customized for a particular orbital slot / coverage area, design costs increase and economies of scale decrease.

[0007]

Accordingly, there is a need for a more cost effective and lighter geostationary satellite system for communicating from geosynchronous orbit. In addition, there is a need for multiple beam antennas that provide the ability to build and reconstruct antenna coverage in orbit for a particular area on the ground.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention is advantageous in that the geostationary satellite system avoids the above disadvantages by combining phased array technology with on-board switching and control. A satellite system comprises three components: a plurality of beamformers.
Active transmit and receive phased array antennas with (eg, Butler matrices); beam select switch matrices (one transmit, one receive); and beam select controllers (instructed from the ground). Consisting of a unique combination of One skilled in the art will recognize that multiple beam beamformers are, for example,
Butler matrix beamformer (described herein) and Rotman lens beamformer
It is understood that any beamformer that forms multiple orthogonal beams, including (Rotman lens beamformer), may be used. In addition, satellites include communication payloads and conventional satellite buses. The communication payload is dynamic, so that capacity can be transferred from one beam to another.
Includes channel assignment function. This further enhances the satellite system's ability to rebuild the resources applied to the service area.

FIG. 1 shows a satellite antenna beam 12 that covers a portion of the earth 10 within the satellite's field of view. Antenna beam 12 is selectable while the satellite is in orbit for active communication with terminals on earth. The Earth's disk 10 as seen from geosynchronous orbit is approximately +/- 8.7 degrees. Thus, in order to completely cover the Earth's disk as viewed from a geostationary satellite, about 500 beams, each having a beamwidth of 0.7 degrees, are required. The geostationary satellite is 35
A satellite that orbits the earth at a distance of 860 kilometers and stays just above its assigned point on the earth's equator.

FIG. 2 shows a block diagram of components 22-29 of geostationary satellite system 20 according to a preferred embodiment of the present invention. Components 22-29 are just a few of the many components that make up a satellite. For example, there are navigation components for positioning the satellite, and power components for generating and maintaining the power of the electronic components of the satellite 20. As shown in FIG. 2, the satellite system 20 includes a communication payload 22, a switch controller 23, a transmission switch matrix 24, a reception switch matrix 25, butler matrix beamformers 26 and 27, a transmission phase adjustment array 28, and a reception It is constituted by a phase adjustment array 29. The communication payload 22 is responsible for receiving the L active beam signals to the transmit switch matrix 24 and selecting a beam command to the switch controller 23. Switch controller 2
3 transmits the selected beam command to the communication payload 2
2 and selects N beam ports for orthogonal (eg, butler matrix) beamformers 26,27. The transmit switch matrix 24 is a quadrature (eg, butler matrix) beamformer 26 and N beam ports from the transmit phasing array 28 (selected by the switch controller 23).
Receive L active beam signals. The receive matrix 25 receives signals from N beam ports (selected by the switch controller 23) from a quadrature beamformer 27 (e.g., a Butler matrix), and transmits L active beam signals to the communication payload. 22.

Each of the transmission phase adjustment array 28 and the reception phase adjustment array 29 is constituted by an array of a number of elements. The transmit phasing array 28 is responsible for transmitting radio frequency (RF) signals, and the receive phasing array 29 is responsible for receiving RF signals from the earth. The RF signal may be a data or voice signal. The transmit multi-beam phasing array 28 comprises an array of multiple active transmit elements. The receiving multi-beam phase adjustment array 29 is constituted by an array of a number of active receiving elements.

FIG. 3 shows the individual antenna elements in a square grid 30. In the case of the transmission phase adjustment array 28,
A separate transmit antenna element 32 is used. In the case of the receiving phase adjustment array 29, individual receiving elements are used. Transmission phase adjustment array 28 or reception phase adjustment array 29
Can be located in a square grid 30 shown in FIG. 3 or in an array aperture in a triangular grid 40 as shown in FIG.

FIG. 3 shows a small square grid portion 30 of the face of the array, where the arrangement of the individual radiating elements is a column.
In the (column) and row rectangular grids, each element 32 occupies a square portion 34 of the entire array area. FIG.
Shows a small triangular grid portion 40 of the transmitting face of the array. Here, the arrangement of the individual radiating elements is in a triangular grid of columns and rows, each element occupying a hexagonal portion of the entire array area. (In FIGS. 3 and 4, only 64 sub-arrays of the total N-element array 22 are shown.) The choice of the element grid depends on the packaging, thermal management and angular field of view. It is well understood by those skilled in the art that it depends on the conditions.

Either array configuration 30 (FIG. 3) or 4
0 (FIG. 4), the directivity of the array aperture is defined as N times the directivity of one array element 32 or 42, where N is the number of elements 32 or 42 and the directivity of one element. The property is 4πA _e / λ ² . Here, the area A _e of the element 34 or 44 is the area of one individual square 34 in FIG. 3 or the area of one individual hexagon in FIG. Lambda λ is the wavelength of the carrier frequency at which the array is designed (eg, 20
GHz, and 30 GHz for the receiving array).

For a generally circular array aperture, the angular width at the -4 dB edge of each beam formed by the array is about λ / D degrees, and the continuous beam is 57 λ / D
Spaced on the center of D degrees. Since transmit and receive are at different frequencies or wavelengths, the transmit and receive arrays must be of different diameters for the transmit / receive beam pairs to have the same coverage.

FIG. 5 shows one of the individual transmission elements 50 of the transmission phase adjustment array 28, which is constituted by a radiating element 51 and an active transmission module 54. The radiating element 51 is located on an active transmitting module 54 that provides the ability to reconstruct the beam polarization in orbit,
It comprises a passive radiator 52 coupled to a computer controlled polarization network 53. Radiating element 51 and polarization network 53 are commercially available from various manufacturers and are well known to those skilled in the art.

The transmitting module 54 includes a computer-controlled polarization switching network 53, an isolator 5
6, a monolithic microwave integrated circuit (MMIC) linear power amplifier 57, a computer controlled phase shifter 58, and a computer controlled attenuator 59. FIG.
As shown in FIG.
6, the isolator 56 is coupled to a solid state power amplifier 57. Amplifier 57 is coupled to active phase shifter 58, which is coupled to active attenuator 59. Attenuator 59 is coupled to the RF input. Phase shifter 58 and attenuator 59 (also MM
ICs) are included to provide phase and amplitude control for compensation and calibration of each RF path through the multiple beam phased array antenna. Computers located elsewhere on the geostationary satellite are connected to the network 5
3. Send commands to the driver circuits in the components of phase shifter 58 and attenuator 59 to cause a change in polarization, phase or attenuation as deemed necessary by the on-board monitoring device. The components of the active transmission module 54 include:
It is commercially available from Raytheon, Texas Instruments, etc., and is well known to those skilled in the art.

FIG. 6 shows one of the individual receiving elements 60 of the receiving phase adjustment array 29, comprising a receiving element 61 and an active receiving module 64. The receiving element 61 includes a passive radiator 62 coupled to a computer controlled polarization network 63 located in an active receiving module 64 that performs on-orbit beam polarization reconstruction. Receiving element 61 is commercially available from various manufacturers and is well known to those skilled in the art.

The receiving module 64 comprises a computer controlled polarization switching network 63, a limiter / protector circuit 66 for protecting against high interference signals, an MMIC low noise receiving amplifier 67, a computer controlled phase shifter 68 and a computer controlled attenuator 69. Is done. As shown in FIG. 6, the polarization network 63 is coupled to a limiter / protector circuit 66, which is coupled to a low noise solid state receive amplifier 67. Amplifier 67 is coupled to active phase shifter 68, which is coupled to active attenuator 69. Attenuator 69 is coupled to the RF output. Phase shifter 68
An attenuator 69 (also MMIC) is included to provide phase and amplitude control for compensation and calibration of each RF path through the multiple beam phased array antenna. A computer located elsewhere on the geostationary satellite sends commands to the driver circuits in the components of the network 63, the phase shifter 68 and the attenuator 69 to determine the polarization, Causes a change in phase or attenuation. The components of the active receiving module 64 are Raytheon, Texas In
It is commercially available from companies such as instruments and is well known to those skilled in the art.

FIG. 7 shows a multiple beam beamformer (mul
2 shows a portion of one embodiment of a ti-beam beamformer 26 or 27 (FIG. 2). As shown in FIG. 7, each beamformer 26 or 27 is a butler matrix (which is well known to those skilled in the art) feed, with eight radiating elements forming eight beams. The inputs to the network 70 shown in FIG. 7 are all outputs from the transmit or receive elements in one column of the transmit or receive phase adjust array 28 or 29 (FIG. 2). Each output beam
The beam available at the port is a fan beam, the dimensions of which are reduced in relation to the length of the column of elements, and which are large in relation to the width of one element. Network 7
FIG. 8 shows details of an example of 8 inputs of 0. As shown in FIG.
Each buttra matrix beamformer 26 or 27
Has a number of hybrid couplers 82 and fixed phase shifters 8
4. The configuration of the butler matrix 70 shown in FIG. 8 is well known to those skilled in the art.

When the network 70 of FIG. 7 is connected to each column of the elements of the transmit phase adjust array 28 or receive phase adjust array 29, and a similar network is connected to each row of column beam ports, beam
(pencil beams) are formed. The pencil beams are continuous and touch each other at about -4 dB points, and if the transmit phase adjustment array 28 or the receive phase adjustment array 29 is pointed at the earth, the pencil beam will To cover.

A network 90 for synthesizing an array of 64 elements of 8 columns and 8 rows is shown in FIG. This network forms the 8 × 8 set of beams shown in FIG. As an alternative to the beamforming scheme of forming all the beams needed to cover the earth and selecting M of these beams to activate, only M beams are formed, Some systems are individually steerable anywhere on the ground. An alternative to the beamforming network described in FIGS. 7, 8 and 9 is partially shown in FIG. Here, the transmission phase adjustment array 2
8 or the active module of each element of the receive phase adjustment array 29 (FIGS. 5 and 6), followed by a 1-to-M distributor /
Combiner (1-to-M spliter / combiner) network 100
Where M is the number of beams to configure. Each of the M outputs of the distributor / combiner network has:
There is a computer controlled phase shifter 102. One of the M phase shifters 102 from each of the N array elements,
Connected to an N-to-1 combiner / distributor to form a separate steerable beam. Therefore, this method requires M × N phase shifters.

Regardless of the type of beamforming network, microwave circuits are low power and can be manufactured using VLSI technology to minimize weight and cost. The overall cost of a solid state multiple beam phased array communication antenna with low power transmit power amplifiers dispersed in terms of antennas is lower than conventional horn-fed reflector and high power TWTA transmitter schemes.
Furthermore, the above-mentioned invention has a low weight and enables beam reconstruction on orbit.

One of the keys of the satellite system 20 is the phase adjustment arrays 28,29 and the butler matrices 26,27.
Is to form an array of potential antenna beams covering the entire hemispherical field of view of the satellite 20. Switch matrices 24 and 25 select which beams to activate at a particular time. In this way, one satellite design can be used for all orbital slot / cover area locations, avoiding all of the above disadvantages.

Each time the satellite service area needs to be changed, the beams are switched and channels are reassigned between the beams. This is for the following reasons: (1) initial construction in orbit; (2) changing the area served by a particular satellite in a slot, for example to serve a new market; (3) Scheduled daily changes to track peak market demand, mainly changes in channel assignments, but depending on the system (educational programming etc.) a complete beam change can be made; ( 4) Reserve construction when assigned to replace a failed satellite (note that
Note that reserves can be put into orbit without knowing which slots will eventually be needed);
(5) To exchange coverage from a failed satellite,
This can be done for temporarily rebuilding the service area of the satellite; and (6) moving the satellite from one slot to another to change the service area.

It should be appreciated by those skilled in the art that the present invention provides a more cost effective means of communicating for geosynchronous satellite applications. The phased array on satellite 20 is more flexible than a horn-fed dish antenna system.

In addition to the advantages described above, the reconfigurable nature of system 20 provides the unique ability to dynamically allocate peak capacity from the GSO, utilizing multiple coverage of service areas from different slots. In this operation configuration, one satellite covers region "A" and a second satellite covers region "B" from the same or a different slot. The third satellite covers the busy portion of region "A" and the busy portion of region "B" from a different slot than the first two satellites. This "peaking" satellite,
As other satellites perform basic coverage, they can be reconfigured very dynamically to take over the peak area.

GSO phased array satellite system 20
Has at least two additional advantages. First,
In addition, the phase adjustment array has a "soft failure"
Due to its function, it is inherently more reliable than the TWTA method. Second, the phased array scheme allows for a smaller beam and requires less transmit power. This power savings compensates for the low efficiency of the phased array,
It is also used to allow larger payloads and / or more beams to be incorporated into the design as needed. Small beams also allow the earth terminal to utilize smaller antennas and lower transmit power, which increases the market potential of the system.

It is therefore intended that the appended claims cover any such modifications of the invention as fall within the true spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 shows a satellite antenna beam covering a portion of the earth in the satellite's field of view.

FIG. 2 is a block diagram illustrating components of a satellite according to a preferred embodiment of the present invention.

FIG. 3 shows a small square grid portion of the emitting surface of the array.

FIG. 4 shows a small triangular grid portion of the emitting surface of the array.

FIG. 5 is a diagram showing components of each active element of the transmission array.

FIG. 6 is a diagram showing components of each active element of the receiving array.

FIG. 7 illustrates a portion of an embodiment of a multiple beam beamformer.

FIG. 8 shows eight 8-element column beamformers and 8
FIG. 3 shows a network of two eight-element row beamformers.

FIG. 9 shows a network of eight eight-element column couplers and eight eight-element row couplers.

FIG. 10 illustrates an 8 × 8 set of continuous beams formed by a network.

FIG. 11 is a diagram showing a part of a second embodiment of the multiple beam / beamformer.

[Explanation of symbols]

 Reference Signs List 10 earth 12 antenna beam 20 geostationary satellite system 22 communication payload 23 switch controller 24 transmission switch matrix 25 reception switch matrix 26, 27 butler matrix beamformer 28 transmission phase adjustment array 29 reception phase adjustment array 50 transmission element 51 Radiating element 52 passive radiator 53 computer controlled polarization network 54 transmitting module 56 isolator 57 MMIC linear power amplifier 58 computer controlled phase shifter 59 computer controlled attenuator 60 receiving element 61 receiving element 62 passive radiator 63 computer controlled polarization network 64 Active receiving module 66 Limiter / protector circuit 67 MMIC low noise receiving amplifier 68 Computer controlled phase shifter 69 Computer controlled Attenuator 70 Network (Batra matrix) 82 Hybrid combiner 84 Fixed phase shifter 90 Network 100 One-to-M splitter / combiner network 102 Computer controlled phase shifter

 ────────────────────────────────────────────────── ─── Continuing the front page (72) John Wesley Rock, East Alameda Drive, Tempe, Arizona, USA 2103 Drive 200 (72) Inventor Keith Andrew Olds West Pampa 548, Mesa, Arizona, United States of America 548 (72) Inventor Jeffrey Sea Upton Augustin Road 8, Groton, Mass., USA

Claims (2)

[Claims] 1. A geostationary communication satellite system having a reconfigurable service area: an array of elements, each element capable of receiving a signal at the satellite system in geosynchronous orbit; A beamformer coupled to the array of elements; a receiving switch matrix coupled to the beamformer via a plurality of beam ports; and a number of the beam ports coupled to the receiving switch matrix. A geostationary communication satellite system, comprising: a selectable switch controller; 2. A satellite, comprising: a transmission phase adjustment array of transmission elements, each transmission element being capable of transmitting signals from said satellite in geosynchronous orbit; a transmission phase adjustment array of reception elements. Receiving phase adjustment array, wherein each receiving element is capable of receiving signals at the satellite in geosynchronous orbit; and coupled to the transmission phase adjustment array and the reception phase adjustment array, some of the transmission elements and the reception element A switch controller capable of selecting one of the following.