Compact single-aperture antenna and navigation system
First Claim
1. A single-aperture direction-finding antenna comprising:
- a. a conductive ground surface;
b. a plurality of rotationally-symmetric conductive driven elements emanating from a common center above said conductive ground surface and supporting at least two direction-finding antenna modes while sharing a single radiating aperture; and
c. at least one rotationally-symmetric conductive member electrically connected to said conductive ground surface at a predetermined radius distance from said common center and extending away from the ground surface toward the driven elements while leaving a gap between said conductive driven elements and said conductive member,whereby azimuthal phase and magnitude variations of said antenna modes are reduced resulting in improved angle-of-arrival accuracy and direction-finding performance over a hemisphere above said conductive ground surface.
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Accused Products
Abstract
An exemplary radio-based navigation system uses a single-aperture multimode direction-finding antenna capable of determining platform position, velocity, attitude, and time while simultaneously providing protection against narrowband and broadband sources of interference. Global Navigation Satellite System (GNSS)-signals such as those from the Global Positioning System (GPS) provide protection against jammers while simultaneously providing attitude measurements with a compact single-aperture multimode antenna (e.g., a small two-arm spiral with improved angle-of-arrival performance over the entire hemisphere enhanced through the use of a conductive vertical extension of the antenna ground plane about the antenna perimeter and/or conductive posts placed evenly around the antenna perimeter). The multimode spiral may be treated as an array of cylindrically symmetric antenna elements. GPS receiver correlation architecture also may be modified for attitude determination by increasing the requisite number of input signals from one to at least two while minimizing the required number of correlators and mixers.
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Citations
34 Claims
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1. A single-aperture direction-finding antenna comprising:
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a. a conductive ground surface; b. a plurality of rotationally-symmetric conductive driven elements emanating from a common center above said conductive ground surface and supporting at least two direction-finding antenna modes while sharing a single radiating aperture; and c. at least one rotationally-symmetric conductive member electrically connected to said conductive ground surface at a predetermined radius distance from said common center and extending away from the ground surface toward the driven elements while leaving a gap between said conductive driven elements and said conductive member, whereby azimuthal phase and magnitude variations of said antenna modes are reduced resulting in improved angle-of-arrival accuracy and direction-finding performance over a hemisphere above said conductive ground surface. - View Dependent Claims (2, 3, 4, 5)
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6. A radio-based navigation system for receiving selected radio-frequency signals of a known origin and a known waveform, and for determining a the system position, velocity, attitude and time with simultaneous interference rejection, said system comprising.
a. at least one single-aperture direction-finding antenna with at least two feed ports and at least two direction-finding antenna modes; -
b. a radio-frequency-to-digital receiver front-end connected to said at least two feed ports wherein said radio-frequency-to-digital receiver front-end at least down-converts each radio-frequency feed signal obtained from said at least two feed ports to respectively corresponding baseband signals; and c. a digital electronics receiver module for at least computing the single-aperture antenna position, velocity, attitude, and time, and reducing the effects of interference, wherein said digital electronics receiver module; (1) combines the baseband signals to form at least two antenna mode signals; (2) combines the baseband signals or the antenna mode signals to create a primary navigation signal such that said selected radio-frequency signals are enhanced and/or the effects of external broadband interference signals, if any, are reduced; (3) generates a replica waveform for each one of said select radio-frequency signals and produces a selected number of in-phase and quadrature-phase signals for said primary navigation signal and for each one of said antenna mode signals; (4) determines the position, velocity, and time of the single-aperture antenna from at least the in-phase and the quadrature-phase signals corresponding to said primary navigation signal; and (5) determines the attitude of the single-aperture antenna from at least the in-phase and the quadrature-phase signals corresponding to said antenna mode signals. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 27, 29, 31, 33)
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14. A method for determining angle of arrival of received radio-frequency signals at a receiving single-aperture direction-finding antenna, said method comprising:
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a. receiving radio-frequency signals via a plurality of rotationally-symmetric conductive driven elements emanating from a common center above a conductive ground surface, which elements support at least two direction-finding antenna modes while sharing a single radiating aperture; b. providing at least one rotationally-symmetric conductive member electrically connected to said conductive ground surface at a predetermined distance from said common center and extending away from the ground surface toward the driven elements while leaving a gap between said conductive driven elements and said conductive member, and c. determining angle-of-arrival of the received radio-frequency signals over a hemisphere above said conductive ground surface. - View Dependent Claims (15, 16, 17, 18)
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19. A method for determining a radio signal receiver'"'"'s position, velocity, attitude and time with simultaneous interference rejection, said method comprising:
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a. receiving selected radio-frequency signals of a known origin and waveform via at least one single-aperture direction-finding antenna with at least two feed ports and at least two direction-finding antenna modes; b. connecting a radio-frequency-to-digital receiver front-end to said at least two feed ports wherein said radio-frequency-to-digital receiver front-end at least down-converts each radio-frequency feed signal obtained from said at least two feed ports to respectively corresponding baseband signals; and c. computing the single-aperture antenna position, velocity, attitude, and time, and reducing the effects of interference, using a digital electronics receiver module which; (1) combines the baseband signals to form at least two antenna mode signals; (2) combines the baseband signals or the antenna mode signals to create a primary navigation signal such that said selected radio-frequency signals are enhanced and/or the effects of external broadband interference signals, if any, are reduced; (3) generates a replica waveform for each one of said select radio-frequency signals and produces a selected number of in-phase and quadrature-phase signals for said primary navigation signal and for each one of said antenna mode signals; (4) determines the position, velocity, and time of the single-aperture antenna from at least the in-phase and the quadrature-phase signals corresponding to said primary navigation signal; and (5) determines the attitude of the single-aperture antenna from at least the in-phase and the quadrature-phase signals corresponding to said antenna mode signals. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 28, 30, 32, 34)
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Specification