Compact single-aperture antenna and direction-finding navigation system
First Claim
1. A single-aperture direction-finding antenna comprising:
- a. at least one conductive driven element located above a conductive ground surface;
b. a plurality of feed ports driving said at least one conductive driven element, wherein the feed ports and the driven element are rotationally-symmetric about a common center above said conductive ground surface and support 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 distance from said common center and extending away from the ground surface toward said at least one conductive driven element while leaving a gap between said at least one conductive driven element 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 small multimode direction-finding antenna and a direction-finding receiver 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 attitude measurements with a compact multimode direction-finding 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) which provides simultaneous protection against jammers. The multimode spiral may be treated as an array of rotationally-symmetric antenna elements. The GPS receiver architecture also may be modified for direction-finding and thereby 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.
85 Citations
42 Claims
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1. A single-aperture direction-finding antenna comprising:
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a. at least one conductive driven element located above a conductive ground surface; b. a plurality of feed ports driving said at least one conductive driven element, wherein the feed ports and the driven element are rotationally-symmetric about a common center above said conductive ground surface and support 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 distance from said common center and extending away from the ground surface toward said at least one conductive driven element while leaving a gap between said at least one conductive driven element 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 the system position, velocity, attitude and time, said system comprising:
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a. a radio-frequency-to-digital front-end configured to accept at least two feed signals from an antenna capable of direction-finding and to convert the feed signals to digital signals; and b. a receiver module configured to process said digital signals wherein said receiver module is configured to; (1) combine the digital signals to form at least two direction-finding signals corresponding to substantially rotationally symmetric direction-finding modes supported by the direction-finding antenna; (2) combine the digital signals or the direction-finding signals to create at least one navigation signal such that said selected radio-frequency signals are enhanced and/or the effects of interference signals, if any, are reduced; (3) determine the system position, velocity, and time from said at least one navigation signal and/or the direction-finding signals; and (4) determine the angles of arrival of said selected radio-frequency signals and thereby the system attitude from the direction-finding signals via simultaneous lobe comparison techniques. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. 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 feed ports for at least one rotationally-symmetric conductive driven element emanating from a common center above a conductive ground surface, wherein said at least one conductive driven element and the feed ports 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 said at least one conductive driven element while leaving a gap between said at least one conductive driven element 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 (23, 24, 25, 26)
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27. A method for determining a radio signal receiver'"'"'s position, velocity, attitude and time, said method comprising:
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a. converting at least two feed signals to digital signals wherein said feed signals are provided by an antenna capable of direction-finding and receiving selected radio-frequency signals of a known origin and waveform; b. combining the digital signals to form at least two direction-finding signals corresponding to substantially rotationally symmetric direction-finding modes supported by the direction-finding antenna; c. combining the digital signals or the direction-finding signals to create at least one navigation signal such that said selected radio-frequency signals are enhanced and/or the effects of interference signals, if any, are reduced; d. determining the receiver'"'"'s position, velocity, and time from said at least one navigation signal and/or the direction-finding signals; and e. determining the angles of arrival of said selected radio-frequency signals and thereby the receiver'"'"'s attitude from the direction-finding signals via simultaneous lobe comparison techniques. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification