Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Reexamination Certificate
2001-08-30
2003-11-04
Issing, Gregory C. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
C342S379000, C455S013300
Reexamination Certificate
active
06642883
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to antenna systems and more specifically to multi-beam antenna communication systems.
Pre-distortion networks are known in the art to improve the self-interference or carrier to interference (C/I) ratio of amplifiers. Multi-beam antenna (MBA) arrays also are well known in the art. The power in the sidelobes of beams in a multi-beam antenna array which are operating at the same frequency as an intended signal interfere with the intended signal. This interference limits the proximity of co-frequency beams. There is also interference which is attributable to adjacent frequency channels, albeit typically at a lower intensity, and it is referred to therefore as adjacent channel interference. Interference from adjacent channels limits the proximity of beams on channels operating at adjacent frequencies. Utilization studies show that in typical applications, the C/I ratio caused by the sidelobes is the largest source of self-interference.
In the transmit mode, the signal received by any particular remote user is the sum of the intended signal for that remote user, which is contained in a beam pointing towards that remote user, and the signals intended for other remote users, which interfere with the intended signal. These interfering signals reach the remote user through the sidelobes of beams pointing towards other remote users. In the receive mode, each beam of the receive antenna collects a signal from at least one remote user and the sidelobes of each beam collect signals from other remote users which act as interference to the intended signal in the beam.
What is needed is an interference cancellation network for a multi-beam antenna to permit more capacity to be focussed into high user density regions.
SUMMARY OF THE INVENTION
In the present invention, a network is disclosed for increasing the beam traffic capacity of a multi-beam antenna system. The multi-beam antenna system comprises a plurality of signals at any frequency transmitted when the multi-beam antenna is used as a transmit antenna, and signals at any frequency received when the multi-beam antenna is used as a receive antenna, the multi-beam antenna of the multi-beam antenna system transmitting in the transmit mode and receiving in the receive mode a plurality of beams having at least one sidelobe causing interference with at least one of the plurality of signals. The plurality of beams having at least one sidelobe cause interference with at least one of the plurality of signals therein defining at least one antenna sidelobe. The multi-beam antenna system comprises an interference cancellation means for canceling the interference with at least one signal caused by the at least one antenna sidelobe.
In particular, the network increases the beam traffic capacity in a region around any remote user, the size of the region being on the order of 3 to 5 beam widths in any direction from the remote user.
When the multi-beam antenna is used as a transmit antenna, and at least one of the plurality of beams transmitted by the multi-beam antenna is pointed towards at least one remote user, the interference cancellation means has an input port for each of the plurality of signals, the interference cancellation means creates a plurality of composite signals, and the interference cancellation means has an output port for each of the composite signals. The transmit antenna has an input port connected to each output port of the interference cancellation means such that the composite signals become the input signals to the transmit multi-beam antenna, and the composite signals emerging from the interference cancellation means optimize the signal to interference ratio at the at least one remote user.
When the multi-beam antenna is used as a receive antenna, each beam of the receive antenna collects a signal, referred to as the intended signal, from at least one remote user, the sidelobe of at least one beam collecting at least one signal from at least one other remote user, and the signal from the at least one other remote user causes interference to the intended signal in the beam. The receive antenna has for each beam an output port which is connected to an input port of the interference cancellation means such that both the intended signal and the interference emerging from each output port of the receive multi-beam antenna are injected into the interference cancellation means at the input port.
The interference cancellation means creates a plurality of composite signals. The interference cancellation means has an output port for each of the composite signals, and the composite signals emerging from the output port of the interference cancellation means optimize the signal to interference ratio of the at least one intended signal collected from the at least one remote user.
Specifically, when the interference cancellation means is a network in a transmit multi-beam antenna system, the interference cancellation means comprises a plurality of power dividers and a plurality of power combiners. Each power divider has an input port connected to the transmit signal intended to be transmitted by the transmit multi-beam antenna system, and each power divider divides the signal connected to the input port into one reference fractional signal and at least one non-reference fractional signal, therein defining the power divider as a source power divider to the one reference fractional signal and to the at least one non-reference fractional signal. The source power divider has a plurality of output ports, and an output port of the source power divider containing the reference fractional signal is connected to an input port of one of the power combiners, therein defining the power combiner as a companion power combiner to the source power divider. Each output port of the source power divider containing a non-reference fractional signal is connected to an input port of another one of the power combiners, therein defining the another one of the power combiners as an associated power combiner to the source power divider. Each companion power combiner receives the at least one non-reference fractional signal through a path connecting from the source power divider of the at least one non-reference fractional signal, therein defining the source power divider of the at least one non-reference fractional signal as an associated power divider to the companion power combiner. Each of the companion power combiners combine the reference fractional signal emerging from the companion source power divider with the at least one non-reference fractional signal from an associated power divider into a composite output signal, wherein an output port of each of the power combiners is connected to an input port of the transmit multi-beam antenna such that the composite signals emerging from the interference cancellation means at the output ports of each of the power combiners become the signals transmitted at any frequency when the multi-beam antenna is used as a transmit antenna.
Again specifically, when the interference cancellation means is a network in a receive multi-beam antenna system, the interference cancellation means comprises a plurality of power dividers and a plurality of power combiners. Each power divider has an input port connected to an output port of the receive multi-beam antenna, such that the signals at any frequency received when the multi-beam antenna is used as a receive antenna become the input signals to the interference cancellation network. Each of the power dividers divide the signal connected to the input port into one reference fractional signal and at least one non-reference fractional signal, therein defining the power divider as a source power divider to the one reference fractional signal and to the at least one non-reference fractional signal. The source power divider has a plurality of output ports, and an output port of the source power divider containing the reference fractional signal is connected to an input port of one of the power combiners, therein defining the pow
Jacomb-Hood Anthony Wykeham
Lier Erik
Volman Vladimir
Issing Gregory C.
Lockheed Martin Corporation
Scully Scott Murphy & Presser
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