Cancellation system for frequency reuse in microwave communications
First Claim
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1. A free-space electromagnetic wave communications system for canceling co-channel interference and transmit signal leakage, said communications system transmitting a plurality of signals from at least one transmit location to at least one receive location, said communications system utilizing spatial gain distribution processing of the transmitted signals for providing frequency-reuse of the transmitted signals, utilizing distributed frequency compensation for compensating for frequency dependent variations of transmitted and received antenna beam patterns, utilizing interferometric beam-shaping for controlling beamwidth of antenna beam patterns, and utilizing interference cancellation for reducing transmit signal leakage in received signals, said communications system comprising:
- a signal transmitter located at the transmit location for transmitting a plurality of transmission signals, each of said transmission signals having a predetermined spatial gain distribution at the receive location,an antenna array comprising a plurality of spatially-separated antenna elements located at the receive location, each of said antenna elements being responsive to at least one of said transmission signals for generating a desired receive communications signal and being responsive to one or more said transmission signals for generating a noise signal,a cancellation circuit coupled to each of said plurality of antenna elements for receiving said desired communications signals and said noise signals, said cancellation circuit providing weights to said desired communications signals and said noise signals wherein said weights are determined from said spatial gain distribution of said transmission signals, said cancellation circuit combining said weighted noise and desired communications signals for canceling said noise signals, thereby separating said communications signals from said noise signals,an excitation means coupled to said antenna elements for generating a predetermined distribution of excitation signals to electrically excite said antenna elements for producing a predetermined beam pattern, the excitation signals having distributed frequency characteristics,a transmit beam-shaping processor coupled to said excitation means for providing a frequency-dependent weight distribution to the excitation signals with respect to signal frequency such that a plurality of frequency-dependent beam patterns is generated by said array, each of the beam patterns corresponding to one of a plurality of different excitation signal frequencies, the beam patterns being substantially equal within a predetermined spatial region,a receiver coupled to said antenna elements for providing a predetermined weight distribution to the receive signals, the weighted receive signals being summed to provide a beam pattern that indicates responsiveness to the incident radiation with respect to an angle of incidence of the incident radiation,a receive beam-shaping processor coupled to said antenna elements for providing a frequency-dependent weight distribution to the receive signals with respect to receive signal frequency to produce a plurality of frequency-dependent beam patterns, each of the beam patterns corresponding to one of a plurality of different receive signal frequencies, the beam patterns being substantially equal within a predetermined spatial region,an interferometric receive beam-shaping processor coupled to said receiver for providing a plurality of weight distributions to the receive signals for providing a plurality of interfering receive beam patterns, the receive beam patterns being combined to produce a combined interferometric receive beam pattern, the combined interferometric receive beam pattern providing a predetermined receiver response in at least one direction,an interferometric transmit beam-shaping processor coupled to said excitation means for providing a plurality of weight distributions to the excitation signals for providing a plurality of interfering transmit beam patterns, the transmit beam patterns being combined to produce a combined interferometric transmit beam pattern, the combined interferometric transmit beam pattern providing a predetermined transmit signal profile in at least one direction, andan isolator circuit coupled between said excitation means, said antenna array, and said receiver, for electrically isolating said receiver from said excitation means, said isolator circuit comprising;
an active branch, said active branch comprising an active reference branch coupled to a splitting circuit for receiving a reference signal, and a transmit branch, said transmit branch comprising a transmit input port for receiving an input transmit signal, a splitting circuit coupled to the input port for splitting the input transmit signal into an output transmit signal and a reference signal, and an output transmit port coupled to an antenna for conducting the output transmit signal to the antenna,a reference sensing element coupled to said active reference branch, said reference sensing element being responsive to the reference signal in said active reference branch,a transmit sensing element coupled to said transmit branch, said transmit sensing element being responsive to the output transmit signal and a receive signal generated by said antenna in response to incident electromagnetic radiation,a combining circuit coupled to said reference sensing element and said transmit sensing element for combining the responses of said reference sensing element and said transmit sensing element for canceling the reference sensing element response to the reference signal and the transmit sensing element response to the output transmit signal, said combining circuit having an output port for coupling the response of said transmit sensing element to the receive signal to a receiver,a passive reference branch coupled to said splitting circuit for receiving the second reference signal, said passive reference branch comprising a reference splitting circuit coupled to a dummy reference branch and a dummy antenna branch, said reference splitting circuit splitting the second reference signal into a dummy reference branch signal and a dummy transmit signal, the dummy reference branch signal being coupled into said dummy reference branch, said dummy reference branch having a complex impedance that is proportional to the complex impedance of said active reference branch, and the dummy transmit signal being coupled into said dummy antenna branch, said dummy antenna branch comprising a variable impedance element, said dummy antenna branch having an impedance that is proportional to the impedance of said transmit branch,an injection circuit coupled between said combining circuit and said dummy antenna branch for injecting the receive signal at the output port of said combining circuit into said second reference branch,a control-signal generator coupled to said active signal branch and said passive reference branch, said control-signal generator being responsive to electrical signals in said active signal branch and said passive reference branch for generating a difference signal therefrom, the difference signal representing differences in the proportion of the complex impedance of said active signal branch to the complex impedance of said passive reference branch, andan impedance controller coupled between said control-signal generator and said variable impedance element for receiving the difference signal and adjusting the impedance of said variable impedance element in order to minimize the difference signal.
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Accused Products
Abstract
Substantial improvements in frequency reuse in microwave communications systems is achieved by canceling co-channel interference and transmitter leakage. Interferometric beam-narrowing reduces beamwidth without reducing peak magnitude of the beam pattern. Frequency-dependent beam-shaping compensates for frequency-dependent distortions of the beam pattern thereby improving bandwidth. A spatial demultiplexing technique utilizes spatial gain distributions of received signals to separate signals, even from co-located transmit sources, and uses microwave lensing to enhance received spatial gain distributions. Predetermined cross-polarization interference is used to separate differently-polarized receive signals. A reference branch provides a cancellation signal to a receiver to cancel transmitter leakage signals. An error signal controls an impedance-compensation circuit that is responsive to changes in antenna impedance but not to receive signals. A dc bias magnetic field applied to a magnetic permeable material adjusts non-linear distortion in a cancellation circuit for canceling distortion in a transmitter leakage signal. Discreet impedance elements approximate a circuit having distributed impedance.
133 Citations
14 Claims
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1. A free-space electromagnetic wave communications system for canceling co-channel interference and transmit signal leakage, said communications system transmitting a plurality of signals from at least one transmit location to at least one receive location, said communications system utilizing spatial gain distribution processing of the transmitted signals for providing frequency-reuse of the transmitted signals, utilizing distributed frequency compensation for compensating for frequency dependent variations of transmitted and received antenna beam patterns, utilizing interferometric beam-shaping for controlling beamwidth of antenna beam patterns, and utilizing interference cancellation for reducing transmit signal leakage in received signals, said communications system comprising:
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a signal transmitter located at the transmit location for transmitting a plurality of transmission signals, each of said transmission signals having a predetermined spatial gain distribution at the receive location, an antenna array comprising a plurality of spatially-separated antenna elements located at the receive location, each of said antenna elements being responsive to at least one of said transmission signals for generating a desired receive communications signal and being responsive to one or more said transmission signals for generating a noise signal, a cancellation circuit coupled to each of said plurality of antenna elements for receiving said desired communications signals and said noise signals, said cancellation circuit providing weights to said desired communications signals and said noise signals wherein said weights are determined from said spatial gain distribution of said transmission signals, said cancellation circuit combining said weighted noise and desired communications signals for canceling said noise signals, thereby separating said communications signals from said noise signals, an excitation means coupled to said antenna elements for generating a predetermined distribution of excitation signals to electrically excite said antenna elements for producing a predetermined beam pattern, the excitation signals having distributed frequency characteristics, a transmit beam-shaping processor coupled to said excitation means for providing a frequency-dependent weight distribution to the excitation signals with respect to signal frequency such that a plurality of frequency-dependent beam patterns is generated by said array, each of the beam patterns corresponding to one of a plurality of different excitation signal frequencies, the beam patterns being substantially equal within a predetermined spatial region, a receiver coupled to said antenna elements for providing a predetermined weight distribution to the receive signals, the weighted receive signals being summed to provide a beam pattern that indicates responsiveness to the incident radiation with respect to an angle of incidence of the incident radiation, a receive beam-shaping processor coupled to said antenna elements for providing a frequency-dependent weight distribution to the receive signals with respect to receive signal frequency to produce a plurality of frequency-dependent beam patterns, each of the beam patterns corresponding to one of a plurality of different receive signal frequencies, the beam patterns being substantially equal within a predetermined spatial region, an interferometric receive beam-shaping processor coupled to said receiver for providing a plurality of weight distributions to the receive signals for providing a plurality of interfering receive beam patterns, the receive beam patterns being combined to produce a combined interferometric receive beam pattern, the combined interferometric receive beam pattern providing a predetermined receiver response in at least one direction, an interferometric transmit beam-shaping processor coupled to said excitation means for providing a plurality of weight distributions to the excitation signals for providing a plurality of interfering transmit beam patterns, the transmit beam patterns being combined to produce a combined interferometric transmit beam pattern, the combined interferometric transmit beam pattern providing a predetermined transmit signal profile in at least one direction, and an isolator circuit coupled between said excitation means, said antenna array, and said receiver, for electrically isolating said receiver from said excitation means, said isolator circuit comprising; an active branch, said active branch comprising an active reference branch coupled to a splitting circuit for receiving a reference signal, and a transmit branch, said transmit branch comprising a transmit input port for receiving an input transmit signal, a splitting circuit coupled to the input port for splitting the input transmit signal into an output transmit signal and a reference signal, and an output transmit port coupled to an antenna for conducting the output transmit signal to the antenna, a reference sensing element coupled to said active reference branch, said reference sensing element being responsive to the reference signal in said active reference branch, a transmit sensing element coupled to said transmit branch, said transmit sensing element being responsive to the output transmit signal and a receive signal generated by said antenna in response to incident electromagnetic radiation, a combining circuit coupled to said reference sensing element and said transmit sensing element for combining the responses of said reference sensing element and said transmit sensing element for canceling the reference sensing element response to the reference signal and the transmit sensing element response to the output transmit signal, said combining circuit having an output port for coupling the response of said transmit sensing element to the receive signal to a receiver, a passive reference branch coupled to said splitting circuit for receiving the second reference signal, said passive reference branch comprising a reference splitting circuit coupled to a dummy reference branch and a dummy antenna branch, said reference splitting circuit splitting the second reference signal into a dummy reference branch signal and a dummy transmit signal, the dummy reference branch signal being coupled into said dummy reference branch, said dummy reference branch having a complex impedance that is proportional to the complex impedance of said active reference branch, and the dummy transmit signal being coupled into said dummy antenna branch, said dummy antenna branch comprising a variable impedance element, said dummy antenna branch having an impedance that is proportional to the impedance of said transmit branch, an injection circuit coupled between said combining circuit and said dummy antenna branch for injecting the receive signal at the output port of said combining circuit into said second reference branch, a control-signal generator coupled to said active signal branch and said passive reference branch, said control-signal generator being responsive to electrical signals in said active signal branch and said passive reference branch for generating a difference signal therefrom, the difference signal representing differences in the proportion of the complex impedance of said active signal branch to the complex impedance of said passive reference branch, and an impedance controller coupled between said control-signal generator and said variable impedance element for receiving the difference signal and adjusting the impedance of said variable impedance element in order to minimize the difference signal.
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2. A free-space electromagnetic wave communications system for transmitting a plurality of signals from at least one transmit location to at least one receive location utilizing spatial gain distribution processing of the transmitted signals for providing frequency-reuse of the transmitted signals, said communications system including
a signal transmitter located at the transmit location for transmitting a plurality of transmission signals, each of said transmission signals having a predetermined spatial gain distribution at the receive location, a receiving antenna including a plurality of spatially-separated receiving elements located at the receive location, each of said receiving elements being responsive to at least one of the transmission signals for generating a desired receive communications signal and being responsive to one or more of the transmission signals for generating a noise signal, and a cancellation circuit coupled to each of said plurality of receiving elements for receiving the desired communications signals and the noise signals, said cancellation circuit providing weights to the desired communications signals and the noise signals wherein the weights are determined from the spatial gain distribution of the transmission signals, said cancellation circuit combining the weighted noise and desired communications signals for canceling the noise signals, thereby separating the communications signals from the noise signals.
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11. A free-space electromagnetic wave communications system for transmitting a plurality of signals from at least one transmit location to at least one receive location utilizing cross-polarization processing of the transmitted signals for providing frequency-reuse of the transmitted signals, said communications system including
a signal transmitter located at the transmit location for transmitting a plurality of transmission signals, each of said transmission signals having a predetermined cross-polarization at the receive location, a receiving antenna including a plurality of spatially-separated receiving elements located at the receive location, each of said receiving elements being responsive to at least one of the transmission signals for generating a desired receive communications signal and being responsive to one or more of the transmission signals for generating a noise signal, and a cancellation circuit coupled to each of said plurality of receiving elements for receiving the desired communications signals and the noise signals, said cancellation circuit providing weights to the desired communications signals and the noise signals wherein the weights are determined from the cross-polarization of the transmission signals, said cancellation circuit combining the weighted noise and desired communications signals for canceling the noise signals, thereby separating the communications signals from the noise signals.
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12. An isolator circuit for electrically isolating a receiver from a transmitter, said isolator circuit comprising:
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a transmit branch comprising a transmit input port for receiving an input transmit signal a splitting circuit coupled to the input port for splitting the input transmit signal into an output transmit signal and a reference signal, the reference signal having less electrical power than the output transmit signal, and an output transmit port coupled to an antenna for conducting the output transmit signal to said antenna, a reference branch coupled to said splitting circuit for receiving the reference signal, a reference sensing element coupled to said reference branch, said reference sensing element being responsive to the reference signal in said reference branch, a transmit sensing element coupled to said transmit branch, said transmit sensing element being responsive to the output transmit signal and a receive signal generated by said antenna in response to incident electromagnetic radiation, and a combining circuit coupled to said reference sensing element and said transmit sensing element for combining the responses of said reference sensing element and said transmit sensing element for canceling the response of said reference sensing element to the reference signal and the transmit sensing element response to the output transmit signal, said combining circuit having an output port for coupling the response of said transmit sensing element to the receive signal to a receiver. - View Dependent Claims (13)
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14. An isolator circuit for electrically isolating a receiver from a transmitter, said isolator circuit comprising:
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an active branch, said active branch comprising an active reference branch coupled to a splitting circuit for receiving a reference signal, and a transmit branch, said transmit branch comprising a transmit input port for receiving an input transmit signal, a splitting circuit coupled to the input port for splitting the input transmit signal into an output transmit signal and a reference signal, and an output transmit port coupled to an antenna for conducting the output transmit signal to the antenna, a reference sensing element coupled to said active reference branch, said reference sensing element being responsive to the reference signal in said active reference branch, a transmit sensing element coupled to said transmit branch, said transmit sensing element being responsive to the output transmit signal and a receive signal generated by said antenna in response to incident electromagnetic radiation, a combining circuit coupled to said reference sensing element and said transmit sensing element for combining the responses of said reference sensing element and said transmit sensing element for canceling the reference sensing element response to the reference signal and the transmit sensing element response to the output transmit signal, said combining circuit having an output port for coupling the response of said transmit sensing element to the receive signal to a receiver, a passive reference branch coupled to said splitting circuit for receiving the second reference signal, said passive reference branch comprising a reference splitting circuit coupled to a dummy reference branch and a dummy antenna branch, said reference splitting circuit splitting the second reference signal into a dummy reference branch signal and a dummy transmit signal, the dummy reference branch signal being coupled into said dummy reference branch, said dummy reference branch having a complex impedance that is proportional to the complex impedance of said active reference branch, and the dummy transmit signal being coupled into said dummy antenna branch, said dummy antenna branch comprising a variable impedance element, said dummy antenna branch having an impedance that is proportional to the impedance of said transmit branch, an injection circuit coupled between said combining circuit and said dummy antenna branch for injecting the receive signal at the output port of said combining circuit into said second reference branch, a control-signal generator coupled to said active signal branch and said passive reference branch, said control-signal generator being responsive to electrical signals in said active signal branch and said passive reference branch for generating a difference signal therefrom, the difference signal representing differences in the proportion of the complex impedance of said active signal branch to the complex impedance of said passive reference branch, and an impedance controller coupled between said control-signal generator and said variable impedance element for receiving the difference signal and adjusting the impedance of said variable impedance element in order to minimize the difference signal.
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Specification
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Current AssigneeArnold Alagar, Hanger Solutions, LLC (IP Investments Group LLC), Steve Shattil
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Original AssigneeGenghisComm LLC
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InventorsShattil, Steve
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Primary Examiner(s)Tarcza, Thomas H.
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Assistant Examiner(s)PHAN, DAO LINDA
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Application NumberUS08/862,859Time in Patent Office949 DaysField of Search342/361, 342/367, 342/368, 342/378, 370/310, 250/551, 359/152, 359/153, 359/154, 379/93.28, 379/412US Class Current342/378CPC Class CodesG01S 3/04 DetailsH01Q 21/06 Arrays of individually ener...H01Q 3/26 varying the relative phase ...H04B 1/525 with means for reducing lea...H04B 7/0613 using simultaneous transmis...H04B 7/086 using weights depending on ...
