US 6,154,501 A · Method and apparatus for combining transponders on multiple satellites into virtual channels

Abstract

A satellite communications system provides an information channel between remotely located transmitters and receivers. A virtual satellite system provides the same service, but divides the signal either in power or in data content into subchannels such that any particular signal is conducted to the intended receiver via a plurality of traditional satellite channels. The receiving terminal accepts the plurality of signals simultaneously from a possible plurality of satellites, combining the subchannels comprising the virtual channel into the original signal content as if conducted via a single channel. The receiving antenna system receives satellite subchannel signals from a plurality of directions using multiple antennas or a single antenna with multi-direction capability. Prior to signal combining, the receiver necessarily time-synchronizes the plurality of subchannels by introducing time delay in some channels before combining the subsignals into the original composite. A timing signal present in the virtual satellite system assists the receiver in determining the amount of delay to apply to each incoming signal. The timing signal is either a separate carrier or an additional modulation on the existing information-bearing carrier.

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Claims34

Dependent claims

A satellite communications system which provides an enhanced digital communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing an original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel uplink system comprising:
a subchannel divider for transforming the original digital signal into a plurality of digital subchannels such that each digital subchannel signal contains at least some information unique to that subchannel and also such that the bit rate of each digital subchannel signal is lower than the bit rate of the original digital signal;
a timing generator creating said common timing signal;
signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;
upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;
amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal;
and
antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel;
and
a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising:
a multiple beam antenna simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;
a plurality of tuners, each coupled to a corresponding multiple beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;
a plurality of demodulators, each coupled to a corresponding tuner output for demodulating tuner output and creating a bit stream corresponding to the information content of the associated subchannel;
a plurality of delay means, each coupled to a corresponding demodulator output for delaying first-arriving subchannel signals such that outputs of the plurality of delay means are synchronized in time;
a digital combiner coupled to the output of the plurality of delay means for combining the information in each of the subchannels into a delayed reconstruction of the original digital signal;
a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;
a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected;
and
a controller coupled to the multiple beam antenna, the plurality of tuners, the plurality of delay means, the timing signal correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to the multiple beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

16 more elements

A satellite communications system which provides an enhanced digital communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing an original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel uplink system comprising:
a subchannel divider for transforming the original digital signal into a plurality of digital subchannels such that each digital subchannel signal contains at least some information unique to that subchannel and also such that the bit rate of each digital subchannel signal is lower than the bit rate of the original digital signal;
a timing generator creating said common timing signal;
signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;
upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;
amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal;
and
antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel;
and
a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising:
a plurality of independent single beam antennas simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;
a plurality of tuners, each coupled to a corresponding independent single beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;
a plurality of demodulators, each coupled to a corresponding tuner output for demodulating tuner output and creating a bit stream corresponding to the information content of the associated subchannel;
a plurality of delay means, each coupled to a corresponding demodulator output for delaying first-arriving subchannel signals such that outputs of the plurality of delay means are synchronized in time;
a digital combiner coupled to the output of the plurality of delay means for combining the information in each of the subchannels into a delayed reconstruction of the original digital signal;
a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;
a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected;
and
a controller coupled to the plurality of independent single beam antennas, the plurality of tuners, the plurality of delay means, the timing signal correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to each independent single beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

16 more elements

A satellite communications system which provides an enhanced digital communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing an original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel uplink system comprising:
a subchannel divider for transforming the original digital signal into a plurality of digital subchannels such that each digital subchannel signal carries identical information at the same bit rate as the original digital signal;
a timing generator creating said common timing signal;
signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;
upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;
amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal;
and
antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel;
and
a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising:
a multiple beam antenna simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;
a plurality of tuners, each coupled to a corresponding multiple beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;
a plurality of demodulators, each coupled to a corresponding tuner output for demodulating tuner output and creating a stream of soft decisions in the form of digitized decision-confidence-values corresponding to the associated subchannel;
a plurality of delay means, each coupled to a corresponding demodulator output for delaying first-arriving subchannel signals such that soft decision outputs of the plurality of delay means are synchronized in time;
a digital combiner coupled to the output of the plurality of delay means for combining soft decision from all subchannels received into said delayed reconstruction of the original digital signal;
a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;
a digital correlator coupled to the delay means outputs for providing an additional measure of the relative delay between channels;
a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected;
and
a controller coupled to the multiple beam antenna, the plurality of tuners, the plurality of delay means, the timing signal correlator, the digital correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to the multiple beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

17 more elements

A satellite communications system which provides an enhanced digital communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing an original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel unlink system comprising:
a subchannel divider for transforming the original digital signal into a plurality of digital subchannels such that each digital subchannel signal carries identical information at the same bit rate as the original digital signal;
a timing generator creating said common timing signal;
signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;
upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;
amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal;
and
antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel;
and
a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising:
a plurality of independent single beam antennas simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;
a plurality of tuners, each coupled to a corresponding independent single beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;
a plurality of demodulators, each coupled to a corresponding tuner output for demodulating tuner output and creating a stream of soft decisions in the form of digitized decision-confidence-values corresponding to the associated subchannel;
a plurality of delay means, each coupled to a corresponding demodulator output for delaying first-arriving subchannel signals such that soft decision outputs of the plurality of delay means are synchronized in time;
a digital combiner coupled to the output of the plurality of delay means for combining soft decision from all subchannels received into said delayed reconstruction of the original digital signal;
a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;
a digital correlator coupled to the delay means outputs for providing an additional measure of the relative delay between channels;
a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected;
and
a controller coupled to the plurality of independent single beam antennas, the plurality of tuners, the plurality of delay means, the timing signal correlator, the digital correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to each independent single beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

17 more elements

A satellite communications system which provides an enhanced analog communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing an original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel uplink system comprising:
a subchannel divider for transforming the original analog signal into a plurality of analog subchannels such that each subchannel signal contains at least some information unique to that subchannel;
a timing generator creating said common timing signal;
signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;
upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;
amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal;
and
antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel;
and
a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising:
a multiple beam antenna simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;
a plurality of tuners, each coupled to a corresponding multiple beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;
a plurality of demodulators, each coupled to a corresponding tuner output for demodulating tuner output and creating an analog signal corresponding to the information content of the associated subchannel;
a plurality of delay means, each coupled to a corresponding demodulator output for delaying first-arriving subchannel signals such that outputs of the plurality of delay means are synchronized in time;
an analog combiner coupled to the output of the plurality of delay means for combining the information in each of the subchannels into said delayed reconstruction of the original analog signal;
a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;
a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected;
and
a controller coupled to the multiple beam antenna, the plurality of tuners, the plurality of delay means, the timing signal correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to the multiple beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

16 more elements

A satellite communications system which provides an enhanced analog communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing an original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel uplink system comprising:
a subchannel divider for transforming the original analog signal into a plurality of analog subchannels such that each subchannel signal contains at least some information unique to that subchannel;
a timing generator creating said common timing signal;
signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;
upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;
amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal;
and
antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel;
and
a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising:
a plurality of independent single beam antennas simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;
a plurality of tuners, each coupled to a corresponding independent single beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;
a plurality of demodulators, each coupled to a corresponding tuner output for demodulating tuner output and creating an analog signal corresponding to the information content of the associated subchannel;
a plurality of delay means, each coupled to a corresponding demodulator output for delaying first-arriving subchannel signals such that outputs of the plurality of delay means are synchronized in time;
an analog combiner coupled to the output of the plurality of delay means for combining the information in each of the subchannels into said delayed reconstruction of the original analog signal;
a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;
a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected;
and
a controller coupled to the plurality of independent single beam antennas, the plurality of tuners, the plurality of delay means, the timing signal correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to each independent single beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

16 more elements

Dependencies are inferred from the claim text.

Description4,880 words

Summary1,766 words

#The invention relates to satellite communications systems generally, and more particularly to satellite communication systems which divide the transmitted signal, either in power or in content, to be synchronized and recombined in the receiving terminal. This concept applies readily to broadcast applications, but it not so limited.

#The satellite industry has experienced a progression of performance enhancements evidenced by increased transmit power capability of satellite transponders, improved low-noise amplifier (LNA) characteristics, and smaller receiving antennas. In satellite systems with a large number of receiving stations, it is particularly important to reduce the cost of each receiving unit and to design a system with a small receiving antenna to meet installation and aesthetic requirements. The need for a small receiving antenna has motivated an increase in transponder power output in order to maintain an acceptable signal-to-noise ratio (SNR) with the smaller antenna. As satellite users move from lower power transponders to higher power transponders, falling demand for the lower power transponders reduces the cost of their use. Receiving a signal from a lower power transponder with the smaller receiving antenna size produces a received power at the LNA too low to maintain SNR requirements. The present invention permits the receiver to combine received signals from a plurality of transponders, possibly located on a plurality of satellites to enable again the use of lower power transponders, but with small receiving terminal antennas.

#A satellite communications system includes a transmitting station that directs information-carrying signals toward an orbiting satellite, which receives the signals and in turn retransmits the signals on a different frequency band toward a plurality of receiving terminals. The satellite contains a transponder which receives signals as a broad band of frequencies and retransmits them on another set of frequencies of equal bandwidth but shifted to another location in the spectrum.

Brief description of the drawings5 figures

#FIG. 1 is a schematic and block diagram illustrating the present invention.

#FIG. 2 is a schematic and circuit block diagram of one embodiment of the present invention.

#FIG. 3 is a schematic and circuit block diagram of another embodiment of the present invention.

Detailed description3,038 words

#Referring now to the drawings in which like reference numerals indicate like or corresponding elements over the several views, FIG. 1 shows an overview of the satellite communications system consisting of subsystems 12, 10, 16. Original signal 22 feeds subchannel divider 24 which separates the signal into a plurality of numbered subsignals. The exemplary system of FIG. 1 shows the number of subsignals to be four, but the present invention is not so limited. Subchannel divider 24 creates the subsignals by dividing original signal 22 employing one of two methods. A first method divides the signal on the basis of power. In this first method all the subchannel signals emerging from subchannel divider 24 are identical. A second method divides the signal on the basis of content. In this second method, each subchannel signal carries at least some information that is not carried by the other subchannels. The information content may be mutually exclusive or may overlap between subchannels, but in any case the subchannel signals under the second divider method are not identical as in the first method. Each subchannel signal feeds an uplink transmitter 26a-26d, each of which uplink transmitters feeds a separate antenna 28a-28d, directing radio frequency energy toward a plurality of orbiting satellites 14a-14d via propagation paths 18a-18d. Uplink transmitters 26a-26d add timing signal 23 to the signal to be transmitted either on a separate frequency allocation or in the bandwidth of the information-bearing carrier.

#FIG. 5 shows additional detail of the uplink system 12. The uplink transmitter 26a includes a signal combiner 262 coupled to the output of the timing generator 231 and the subchannel divider output 24a associated with each subchannel. The signal combiner 262 adds the timing signal 23 to each subchannel information signal 24a within the bandwidth of each subchannel information signal 24a such that no additional bandwidth allocation is required to transmit the timing signal 23.

#Each of the uplink transmitters 26 further includes an upconverter 264 coupled to the output of the signal combiner 262 that is associated with each subchannel. The upconverter 264 translates the frequency of the timing-added subchannel signal 262a to the frequency of the selected satellite transponder 14a.

Method and apparatus for combining transponders on multiple satellites into virtual channels

Life of this patent

Method and apparatus for combining transponders on multiple satellites into virtual channels

Life of this patent

Life of this patent

Abstract

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Claims34

Description4,880 words

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Classification3 codes

Life of this patent

Description4,880 words