U.S. patent application number 09/222419 was filed with the patent office on 2001-10-25 for reconfigurable satellite and antenna coverage communications backup capabilities.
This patent application is currently assigned to THOMPSON, JAMES D.. Invention is credited to DIXON, CYNTHIA A., DUNWOODY, JOHN, FEUERBON, DEBBIE H., GOLDBERG, DAVID R., RAMANUJAM, PARTHASARATHY, SHAH, LOMASH, SICHI, STEPHEN, THOMPSON, JAMES D..
Application Number | 20010034206 09/222419 |
Document ID | / |
Family ID | 22832123 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010034206 |
Kind Code |
A1 |
THOMPSON, JAMES D. ; et
al. |
October 25, 2001 |
RECONFIGURABLE SATELLITE AND ANTENNA COVERAGE COMMUNICATIONS BACKUP
CAPABILITIES
Abstract
A reconfigurable payload for a satellite having a flexible
antenna system, a variable downconverter technology and a filter
technology that all work in combination to allow the payload of a
satellite to be reconfigured in orbit.
Inventors: |
THOMPSON, JAMES D.;
(MANHATTAN BEACH, CA) ; RAMANUJAM, PARTHASARATHY;
(REDONDO BEACH, CA) ; DIXON, CYNTHIA A.; (RANCHO
PALOS VERDES, CA) ; FEUERBON, DEBBIE H.; (CERRITOS,
CA) ; GOLDBERG, DAVID R.; (REDONDO BEACH, CA)
; SICHI, STEPHEN; (LOS ANGELES, CA) ; SHAH,
LOMASH; (REDONDO BEACH, CA) ; DUNWOODY, JOHN;
(LONG BEACH, CA) |
Correspondence
Address: |
JOHN A. ARTZ, ESQ.
ARTZ & ARTZ
28333 TELEGRAPH ROAD
SUITE 250
SOUTHFIELD
MI
48034
US
|
Assignee: |
THOMPSON, JAMES D.
|
Family ID: |
22832123 |
Appl. No.: |
09/222419 |
Filed: |
December 23, 1998 |
Current U.S.
Class: |
455/12.1 ;
455/427 |
Current CPC
Class: |
H04B 7/18519 20130101;
H04B 7/2041 20130101 |
Class at
Publication: |
455/12.1 ;
455/427 |
International
Class: |
H04B 007/185 |
Claims
What is claimed is:
1. A reconfigurable satellite for modifying predetermined
characteristics of a payload, the reconfigurable satellite
comprising: an antenna system having a flexible coverage pattern; a
variable signal converter system for converting a first
predetermined frequency to a second predetermined frequency; and
filter means for isolating selected input and output channels;
whereby the predetermined characteristics of the payload can be
modified by changing the flexible coverage pattern, varying the
first and second predetermined frequencies and filtering the input
and output channels while the satellite is in orbit.
2. The reconfigurable satellite as claimed in claim 1 wherein the
modified predetermined characteristics of the payload mimic
predetermined characteristics of a failed satellite such that the
reconfigurable satellite provides a backup means for the failed
satellite with minimal interruption in satellite service.
3. The reconfigurable satellite as claimed in claim 1 wherein the
antenna system further comprises a dual reflector antenna that is
steerable, rotateable and defocusable.
4. The reconfigurable satellite as claimed in claim 1 wherein the
antenna system further comprises a single reflector antenna that is
steerable, rotateable, and defocusable.
5. The reconfigurable satellite as claimed in claim 1 wherein the
antenna system further comprises a reconfigurable phased array.
6. The reconfigurable satellite as claimed in claim 1 wherein the
variable signal converter further comprises: a plurality of
oscillators each operating at a different predetermined frequency
equal to the difference between a first predetermined frequency and
a second predetermined frequency; a first mixer connected to each
of the plurality of oscillators for mixing the first predetermined
frequency with one of the different predetermined frequencies of
the plurality of oscillators; a switch connected between at the at
least one mixer and each of the plurality of oscillators, the
switch for selecting one of the plurality of oscillators; whereby
the mixer produces an output equal to the second predetermined
frequency.
7. The reconfigurable satellite as claimed in claim 1 wherein the
variable signal converter further comprises: the first
predetermined frequency being one of a plurality of frequencies; a
first synthesizer for generating an output to be mixed with the
plurality of first predetermined frequencies; a first mixer
connected between the plurality of first predetermined frequencies
and the first synthesizer for mixing the plurality of first
predetermined frequencies with the output of the first synthesizer
to produce an intermediate frequency; a second synthesizer for
generating an output to be mixed with the intermediate frequency; a
second mixer for mixing the intermediate frequency and the output
of the second synthesizer to produce a plurality of second
predetermined frequencies.
8. The reconfigurable satellite as claimed in claim 1 wherein the
filter means further comprises: a network of switches for routing a
signal through the input channels; a plurality of input multiplexer
filters selected by the network of switches for channelizing the
input channels; a network of switches for routing the signal from
the input multiplexer filters to a plurality of output multiplexer
filters; a network of switches that accepts an output signal from
the plurality of output multiplexer filters and reconfigures the
payload.
9. The reconfigurable satellite as claimed in claim 3 wherein the
dual reflector antenna is a standalone antenna.
10. The reconfigurable satellite as claimed in claim 3 wherein the
dual reflector antenna is used in a farm of antennas.
11. The reconfigurable satellite as claimed in claim 4 wherein the
single reflector antenna is a standalone antenna.
12. The reconfigurable satellite as claimed in claim 4 wherein the
single reflector antenna is used in a farm of antennas.
13. The reconfigurable satellite as claimed in claim 5 wherein the
reconfigurable phased array is a direct radiating antenna
system.
14. The reconfigurable satellite as claimed in claim 5 wherein the
reconfigurable phased array is reflecting off a dual antenna
system.
15. The reconfigurable satellite as claimed in claim 5 wherein the
reconfigurable phased array is reflecting off a single antenna
system.
16. The reconfigurable satellite as claimed in claim 6 wherein the
variable signal converter further comprises: an oscillator
operating at a different predetermined frequency to be mixed with
the first predetermined frequency; a second mixer connected to the
oscillator for mixing the first predetermined frequency and the
different predetermined frequency and output an intermediate
frequency; whereby the intermediate frequency is mixed with one of
the frequencies of the plurality of oscillators to produce the
second predetermined frequency.
17. The reconfigurable satellite as claimed in claim 16 wherein the
variable signal converter further comprises: a plurality of
oscillators each operating at a different predetermined frequency
to be mixed at the second mixer with the first predetermined
frequency; a switch connected to each of the plurality of
oscillators and the second mixer for selecting one of the plurality
of oscillators; whereby the second mixer produces an output equal
to the intermediate frequency.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to co-pending U.S. patent
application Ser. No. ______, entitled "A Rotatable Scannable
Reconfigurable Shaped Reflector With a Movable Feed System" filed
simultaneously with the present application, the subject matter of
such co-pending application being incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present invention relates to space and communications
satellites, and more particularly, to a reconfigurable payload for
a satellite so that it may mimic many payloads to provide backup
services for many different satellites or to be used as a flexible
stand alone satellite.
BACKGROUND ART
[0003] Satellite fleet operators depend on continuity of service
for a satellite in order to maintain continuous service to
satellite users. In the event of a satellite failure, a backup
service is needed to avoid extended inconvenience to users, or to
avoid the risk of users being lost to a competitor before a backup
satellite can be ordered, built and launched.
[0004] In many applications, a satellite's frequency plan and
coverage is unique. In some cases, the satellite customer does not
have prior knowledge of his customers. Therefore, a reconfigurable
satellite provides in-orbit flexibility. If a customer base changes
while the satellite is in orbit, it can be reconfigured to provide
service. In the situation of providing backup services, a unique
spare satellite would be required for each satellite in a fleet of
satellites.
[0005] A backup satellite having the capability to be reconfigured
would avoid the expensive option of a unique spare. A satellite
having a communication payload that can be reconfigured in space so
that it mimics various payloads with various frequency plans and
antenna coverages would allow a single satellite to provide backup
services to many different satellites. In addition, a
reconfigurable payload would allow a satellite fleet operator to
provide a replacement satellite relatively quickly in the event of
a satellite failure.
[0006] A satellite having a communication payload that can be
reconfigured in space so that it mimics various payloads with
various frequency plans and antenna coverages would allow a single
satellite to provide services to many different customers over the
lifetime of the satellite. A reconfigurable payload would allow a
satellite fleet operator to have flexibility in-orbit. This allow
the operator to procure and build a reconfigurable satellite while
marketing satellites to various customers. The result is a
satellite that is ready for orbit quicker, and ready to provide
services sooner.
SUMMARY OF THE INVENTION
[0007] The present invention is a communication payload that can be
reconfigured in space such that it mimics many payloads with
various frequency plans and antenna coverages. The combination of a
flexible antenna system and an agile repeater capable of handling
various uplink and downlink frequency plans makes a reconfigurable
payload possible.
[0008] Three technologies are combined to make a reconfigurable
payload for a satellite; a flexible coverage pattern, a variable
downconverter technology, and sufficiently filtered channels across
the downlink bandwidth. There are several variations to each of
these three technologies, each combinable with the others.
[0009] A flexible coverage pattern can be provided by any one of
the following methods: a dual reflector antenna configuration that
is steerable, rotateable, and/or defocusable used as a standalone
antenna or as part of a farm of antennas, a single reflector
antenna configuration that is steerable, rotateable and/or
defocusable used as a stand alone or in a farm of antennas, or a
reconfigurable phased array either direct radiating or reflecting
off either a dual or a single antenna system.
[0010] The variable downconverter technology can be provided by any
means. It is possible to use downconverters that have either local
or external oscillators. The frequency is generated either by a
frequency synthesizer or switching between multiple fixed
oscillators of various frequencies. Another frequency selecting
alternative is groups of switchable downconverters using fixed
oscillators.
[0011] Channels across the downlink bandwidth can be sufficiently
filtered using a sufficient number of input multiplex (IMUX)
filters to channelize every channel of the potential receive
spectrum. Additionally, a sufficient number of output multiplex
(OMUX) filters to channelize every channel of the potential
transmit spectrum is also used. A sufficient number of switches are
used to access IMUX and OMUX filters, along with a method of
routing channels between IMUX filters, OMUX filters, switches and
high power amplifiers.
[0012] It is an object of the present invention to improve the
backup capabilities of satellite systems.
[0013] It is another object of the present invention to provide a
satellite payload that can be reconfigured to mimic the payload of
many different satellites, thereby improving backup capabilities
without the cost prohibitive option of individual backup
satellites.
[0014] It is still another object of the present invention to
provide a flexible antenna configuration, a selectable uplink and
downlink frequency plan, and a channelized filter system to have
reconfigurable payload capabilities for a satellite.
[0015] Other objects and features of the present invention will
become apparent when viewed in light of the detailed description of
the preferred embodiment when taken in conjunction with the
attached drawings and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1A is an example of a coverage pattern for four Ku-band
antennas on a reconfigurable satellite of the present
invention;
[0017] FIG. 1B is an example of a different coverage pattern for
four Ku-band antennas on the reconfigurable satellite of the
present invention;
[0018] FIG. 1C is an example of another coverage pattern for four
Ku-band antennas on the reconfigurable satellite of the present
invention;
[0019] FIG. 2 is a block diagram of a single conversion mixer with
a fixed oscillator;
[0020] FIG. 3 is a block diagram of multiple downconverters for
selectable downconversion frequencies;
[0021] FIG. 4 is a block diagram for selectable downconversion
frequency using multiple switched oscillators;
[0022] FIG. 5 is a block diagram of multiple fixed oscillators in a
dual conversion configuration;
[0023] FIG. 6 is a block diagram of multiple oscillators to handle
variable up and down conversion frequencies with a common IF;
[0024] FIG. 7 is a block diagram of a dual conversion synthesizer
topology with a common IF; and
[0025] FIG. 8 is a block diagram of a reconfigurable payload.
BEST MODES FOR CARRYING OUT THE INVENTION
[0026] Three separate technologies are utilized in one spacecraft
to allow a communications payload of a satellite to be reconfigured
in space such that it may mimic many payloads with various
frequency plans and antenna coverages for providing backup services
for failed satellites. Flexible antenna coverage, variable
downconverter technology and channels sufficiently filtered across
the downlink bandwidth are all necessary, in combination, to
achieve reconfiguration of the satellite in space.
[0027] A typical, non-reconfigurable spacecraft has "shaped"
antenna coverage. To generate the strongest received signal on the
ground, a shaped coverage pattern transmits the maximum amount of
the available power to the intended coverage area and the minimum
amount of power to undesired areas. For example, an English
language direct-to-home satellite system might broadcast to the
United States and Canada while it would not transmit to adjacent
ocean regions and Mexico.
[0028] The shape of the desired coverage pattern varies from
satellite to satellite. A beam covering the United States varies
significantly from a beam covering Japan or Europe. Even two
satellites covering the same areas may require different shaped
beams if they are located at two different orbital locations.
[0029] For a reconfigurable satellite to be flexible and to mimic a
variety of satellites, the satellite must be able to change its
coverage pattern in orbit. A broadband flexible antenna coverage is
necessary in a reconfigurable spacecraft design. The broadband
nature of the antenna is required so that the same antennas may
receive or transmit any of the desired uplink and downlink
frequencies. To the extent that the antennas are not sufficiently
broadband, additional antennas will be required, (i.e. separate
transmit and receive antennas). However, there is a significant
increase in weight and therefore, cost associated with additional
antennas.
[0030] There are several technologies available to accomplish this
goal. For example, pointable, rotateable, defocusable antennas
mounted to the nadir, or earth-facing, side of the spacecraft can
be rotated, pointed and defocused to provide coverage for any
desired area.
[0031] FIGS. 1A through 1C are examples of three such coverage
patterns for four Ku-band antennas. It should be noted that while
Ku-band antenna coverage is shown, it is for example purposes and
the present invention can be applied to C-band and Ka-band
operation as well. FIG. 1A is the Atlantic Ocean Region (AOR)
including the United States, Mexico, Northern South America,
Southern South America and Europe. FIG. 1B is the Indian Ocean
Region (IOR) including Europe and the Middle East, India, Asia, and
South Africa. FIG. 1C is the Pacific Ocean Region (POR) including
Northeast Asia, Southeast Asia, Australia and the United States.
These are examples of the different shaped antenna patterns in a
satellite fleet.
[0032] Other technologies may be used to accomplish the same
effect. For example, reconfigurable phased array antennas or
steerable spot beam antennas, or a combination are well known
antenna technologies that can change their coverage patterns in
orbit. In the preferred embodiment, there are six (6) antennas in
the system. Two operate at C-band and four operate at Ku-band. All
of the antennas are Gregorian dual-reflector antennas with a
rotateable main reflector. The four Ku-band antennas also use feed
defocusing which facilitates beam shape variation in orbit. The
function of the antenna system is to generate beams covering the
many different areas covered by existing satellites in a fleet of
satellites, for example, the three ocean regions shown in FIGS. 1A
through 1C.
[0033] A reconfigurable payload can be realized by combining a type
of flexible antenna coverage technology with variable uplink and
downlink frequency technologies and sufficient filtering
technologies.
[0034] Variable downconverter technology is the next piece of the
present invention. The frequency at which a signal is transmitted
to a satellite is known as the uplink frequency. The frequency at
which the signal is broadcast back down to the ground is referred
to as the downlink frequency. The uplink and downlink frequencies
must be different from each other to avoid interference with each
other. The process of changing a signal from the uplink frequency
to the corresponding downlink frequency is known as downconversion.
This is because the uplink frequency is generally higher than the
downlink frequency. And, for obvious reasons, in cases where the
uplink frequency is lower than the downlink frequency, the process
is called upconversion.
[0035] Upconverters and downconverters use an analog technology
known as a mixer. A mixer takes the input of two voltage signals
and outputs their product. To downconvert (or upconvert) a signal,
the mixer is fed by the uplink signal and an oscillator operating
at a frequency equal to the difference between the uplink and
downlink frequencies. The mixer outputs the product of the
frequencies equal to the desired downlink frequency.
[0036] An example of a single conversion mixer with a fixed
oscillator is shown in FIG. 2. The uplink signal has a frequency,
f1. The downlink signal has a frequency, f2. An oscillator operates
at a frequency that, when mixed with the uplink signal, produces a
downlink signal f2. A wide range of oscillator frequencies are used
by satellites to perform up and down conversions. Therefore, a
satellite attempting to mimic the operating of existing or future
satellites must be able to mimic the frequencies of the oscillators
on board any one of many satellites.
[0037] Typically, on a satellite, the device containing the mixer
is inside a box known as either a downconverter, or if a low noise
amplifier is also inside the box, it is known as a receiver. In
both cases, the oscillator may be either internal or external to
the box. When the oscillator is internal to the box, it is called a
local oscillator. Local oscillators are typically generated by the
use of crystals operating at precise predetermined frequencies
[0038] There are a several technologies available that generate a
variety of frequencies. One way is to switch between a variety of
up and down converters, each with its own local oscillator, or to
use an up (or down) converter fed by a variety of switchable
oscillators each operating at a different frequency. An example of
this arrangement is shown in FIG. 3.
[0039] There is shown in FIG. 3 an uplink signal having a frequency
f1, a switch S1 selects between a first mixer, M1 and a second
mixer, M2. A second switch S2 selects between the mixers M1 and M2
and outputs the desired downlink frequency. Each of the mixers M1
and M2 is connected to an independent oscillator 10 and 12 having
fixed frequencies. The first oscillator 10 is connected to the
mixer M1 and operates at a frequency of f2-f1. The second
oscillator 12 is connected to the second mixer, M2 and operates at
a frequency f3-f1.
[0040] Depending on which switch path is selected, the downlink
frequency can be selected as either f2 or f3. When switch S1 is
selected, the output of the mixer is the downlink frequency f2 and
when switch S2 is selected the output of the mixer is the downlink
frequency f3. Obviously, the complexity of the switching system
depends on the number of switches, mixers and oscillators and can
be modified as necessary.
[0041] An alternative method is to use a down (or up) converter fed
by a variety of switchable oscillators each operating at a
different frequency. An example of this arrangement is shown in
FIG. 4. The uplink signal is operating at frequency f1 and is fed
into a mixer M1 that produces the downlink signal. A switch, S1,
allows desired frequencies to be selected from multiple
oscillators. In the FIG. 4 example, two independent oscillators are
shown 12 and 14, each operating at a different frequency.
Oscillator 12 operates at a frequency f2-f1 and oscillator 14
operates at a frequency of f3-f1. Therefore, depending on which
oscillator is selected by switch S1 and mixed with uplink frequency
f1 in mixer M1, the downlink frequency will be f2 or f3. It is to
be understood that any number of oscillators may be employed.
[0042] In the configuration shown in FIG. 4, there is the potential
for in-band spurious signals to degrade the quality of the
communication signal. A spurious signal, also called a spur, is an
undesired tone generated by the non-linear properties inherent to
mixers. The severity of a spur is a function of the signal and
local oscillator frequencies. There is an alternative method to
downconvert, without the drawback of spurs. A dual conversion
design eliminates spurs by first downconverting the signal to an
intermediate frequency (IF) and then performing a second conversion
to the desired downlink frequency.
[0043] The output of the mixer is a product of frequencies, which
also includes a product of harmonics of those frequencies. These
harmonics, or spurs, may be close in frequency to the desired
signal making it difficult to filter out the undesired frequencies.
Carefully selecting an intermediate frequency will avoid
interference from potential harmonics the sums and differences of
the receive and local oscillator signals that are near the desired
downlink signal.
[0044] FIG. 5 is a block diagram of a downconverter having multiple
fixed oscillators in a dual conversion configuration to select
different downlink frequencies from the same downconverter without
the potential for spurs by using an intermediate frequency (IF).
The arrangement is similar to the one shown in FIG. 4. However,
there is an additional mixer M2 and an oscillator 16 operating at a
frequency that, when mixed with the uplink frequency f1 will output
a predetermined intermediate frequency (IF). The intermediate
frequency (IF) is mixed with the signal from either oscillator 12
having a frequency of f2-IF or oscillator 14 having a frequency of
f3-If to output the downlink frequency either f2 or f3.
[0045] In some applications it is necessary to handle different
uplink and downlink frequencies on the same downconverter. The dual
conversion arrangement can be modified such that the oscillator
that mixes with the uplink signal can also vary. FIG. 6 is an
example of multiple oscillators to handle variable up and down
conversion frequencies with a common intermediate frequency. The
uplink signal has a variable frequency, f1 or f2. The uplink signal
is mixed, by mixer M1, with an intermediate frequency (IF), fed by
one of two oscillators 18 or 20 and a switch S1 to select between
the oscillators 18 and 20. The uplink signal is then converted to
the intermediate frequency (IF). Another mixer M2 mixes the
intermediate frequency (IF) with a signal from one of a plurality
of oscillators 22 and 24, selectable by switch S2. In the example
shown in FIG. 6, the oscillators 22 and 24 operate at frequencies
f3-IF and f4-IF respectively. The result is a variable down link
signal, in the example shown either f3 or f4. While only four
oscillators are shown in the present example, it is to be
understood that any number of oscillators is possible, resulting in
any number of possible output frequencies.
[0046] Multiple oscillators are one way to generate multiple
downconversion frequencies. An alternative to multiple oscillators
is the use of synthesizers. Synthesizers generate an arbitrary
frequency within a specified range of frequencies and fixed step
size. Therefore, a single synthesizer can replace a single, or many
oscillators. FIG. 7 is a block diagram of this arrangement.
[0047] The system has an uplink signal having a frequency u1, u2,
u3, etc. A synthesizer 26 produces a signal u1-IF, u2-IF, u3-IF,
etc and is mixed with the uplink signal by mixer M1. The uplink
signal is now converted to the intermediate frequency IF. The
intermediate frequency IF is mixed in mixer M2 with a signal from
another synthesizer 28 that is capable of generating a signal
d1-IF, d2-IF, d3-IF, etc. The output of mixer M2 is the downlink
signal d1, d2, d3, etc. In FIGS. 4 through 7 the intermediate
frequency was assumed to be lower than the receive frequency for
the purpose of illustration. In practice, the intermediate
frequency (IF) may be higher or lower than the receive frequency as
long as the resulting intermediate frequency (IF) yields a spur
free region to translate to the final desired output frequency.
Either approach may be used.
[0048] The last piece of the present invention lies in proper
filter technologies. In order to accommodate operation in a wide
portion of the allocated spacecraft transmit spectrum, input and
output channel filters are required for each possible broadcast
channel. It is possible to select filters that cover the entire
bandwidth contiguously. This provides the most efficient scenario.
FIG. 8 is a block diagram of a repeater for a reconfigurable
satellite of the present invention, and can be used to explain the
filtering technology.
[0049] The input channel filters 40, or IMUX, separate the wideband
uplink signal into multiple channels. The signals are low power,
and losses are not a major concern at low power levels. Therefore,
these filters are easily selectable. In operation the signal is
passed through each channel where a passband of the filter selects
and routes the proper signal. All other signals are reflected back
into a circulator and passed onto the next channel filter.
[0050] The output channel filters 48, or OMUX, combine amplified
signals and route the signal to the antenna. The output channel
filters are high power. The number of channels should be limited to
approximately twenty (20) adjacent channels for practical purposes.
Theoretically, there is no limit to the number of contiguous OMUX
filters, but for practical design considerations, the number should
be limited until current the current state of the art is enhanced
enough to make more channels cost effective. OMUX filters deal with
signals that are at very high power levels. High power results in
the generation of heat and the must be dissipated. Additionally,
operating at high power means that losses become more critical.
[0051] In the preferred embodiment, to accommodate more channels
using existing technology and still avoid excessive heat and losses
while maintaining realistic costs, it is necessary to combine
multichannel continuous OMUX filters with diplexed groups of
contiguous OMUX filters. Gaps must be present in the diplexed
frequency region in order for minimum insertion losses. It is also
possible to include tunable filters or high/low pass filters as
alternatives to diplexers. In the future there may be technology
that allows contiguous filters with more channels that will
simplify the present invention.
[0052] It may not always be desirable for the satellite to operate
near the full number of possible channels in a given configuration.
In such cases, there will be more filters than active channels. A
reduced number of active channels permits fewer high power
amplifiers to be implemented in the payload. A switching system 42
and 46 that allows different amplifiers to be switched to and from
different filters depending the desired satellite configuration is
incorporated. High power microwave switches make it possible to use
the same high power amplifier with multiple filters. The routing
from switches- to amplifiers and filters is accomplished with
either coaxial cables or waveguide.
[0053] Referring to FIG. 8 in detail, there is shown a block
diagram of one embodiment of a repeater for the reconfigurable
satellite of the present invention. The example diagram in FIG. 8
is capable of mimicking any one of six satellites in a fleet of
satellites. It should be noted that while this example of backing
up any one of six satellites is shown, the present invention can be
applied to mimic any number of satellites, or can be used as a
stand alone satellite for in-orbit flexibility.
[0054] Section I of FIG. 8 establishes the repeater noise figure,
converts signals from the receive band to the transmit band and
provides a substantial portion of the repeater gain. In the present
example, Section I accepts input signals at eight antenna ports 30.
The signals are routed through low noise amplifiers 32 to a network
34 which combines the received beams in any desired combination for
the flexible antenna coverage discussed above. Downconverters 36
handle various frequencies and can perform any one of six
conversions required by a satellite fleet of six satellites and
provide the variable downconversion discussed above.
[0055] Section II accepts the signal sets from Section I and
divides them into channelized portions using input multiplexer
filters. This is done by a set of switches 38 that route the
various Section I outputs to the appropriate input filters 40.
After filtering, the channelized signals, which can be up to
thirty-six (36) channels, are routed through a traveling wave tube
(TWT) input redundancy ring. Each box in the block diagram
represents six (6) input filters 40. A total of ninety-six (96)
input filters are used to provide the required frequency plan
flexibility. The channelized output signals are routed through
another set of switches 42 to Section III.
[0056] Section III provides the channelized gain control, TWT
linearization, and amplification to the TWT output levels of 140
Watts. An equalization network (not shown) may also be included
with each TWT to equalize its frequency response over the transmit
bandwidth. This permits broadband linearization of the TWT's. Each
box in Section III represents a set of six active TWT's with
linearizers, or high power amplifiers, 44, also known as OMUX
filters.
[0057] Section IV accepts the amplified output signals from the
TWT's and routes them through the output portion of the redundancy
ring to the output multiplexer selection switches 46. These
switches 46 are used to configure the repeater to emulate any of
the six satellites in the fleet. The switches access up to four
multiplexers for each polarization. Each output multiplexer box
represents six (6) output filters 48. A total of one hundred
fifty-six (156) output filters 48 are used in the output
multiplexers to achieve the versatility in the frequency spectrum.
The section IV outputs are connected to transmit antennas 50.
[0058] The combination of the flexible antenna system, the variable
downlink conversion system and the selectable filter technology
allow a single satellite to be reconfigured to mimic any other
satellite in a fleet of satellites. This allows a single satellite
to provide backup for any one satellite that may fail in fleet. The
reconfigurable satellite of the present invention provides backup
coverage without having to interrupt service and force users to use
alternative satellite operators to continue their service. The
backup coverage provided by the reconfigurable satellite of the
present invention is accomplished with minimal interruption of
service and without the impractical expense of having a unique
spare for each satellite of a fleet.
[0059] While particular embodiments of the invention have been
shown and described, numerous variations and alternate embodiments
will occur to those skilled in the art. Accordingly, it is intended
that the invention be limited only in terms of the appended
claims.
* * * * *