Calibration method for receive only phased array radar antenna
First Claim
1. A method for determining calibration constants for calibrating a receive only phased array antenna comprising the steps of:
- providing a pair of transmit signals with unknown polarization;
identifying known parameters including a location ({right arrow over (x)}n) of an antenna element (n) of said phased array antenna, an orientation Δ
{right arrow over (x)}n of said antenna element (n) polarization of element (n) relative to the orientation of element (n), and a location of a transmitter {right arrow over (x)}1;
identifying unknown parameters including weights (wn) of the elements (n), and vertical magnitude (Ev) and horizontal magnitude (EH) of each of said transmit signals;
determining a receive signal at each of said antenna elements based on said transmit signals;
defining six simultaneous equations with seven unknowns using one antenna element as a standard (p), a second antenna element (m, where m≠
p) and a third antenna element (n, where n≠
p and n≠
m);
solving said six simultaneous equations for weights for every possible set of three antenna elements to find a vector of calibration weight (w) for each antenna element; and
averaging said calibration weights (w) for each antenna element.
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Abstract
A method of calibrating a receive only, phased array antenna in its operating environment. Two transmit signals of different but unknown polarizations are used to calibrate the receive only antenna array, and the receive element locations and polarizations are accurately known. The method determines the complex weights on the antenna elements and the magnitude of the vertical and horizontal components of the calibration signal in the presence of multi-path signals as well as standard noise. Two different methods for calibrating are provided. A first method uses combinations of three elements to determine the calibration constants using small matrices and then averaging all the possible results for each element, and a second method solves for the calibration constants for all elements at one time using a singular value decomposition, but requires the manipulation of large, sparse matrices.
30 Citations
8 Claims
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1. A method for determining calibration constants for calibrating a receive only phased array antenna comprising the steps of:
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providing a pair of transmit signals with unknown polarization; identifying known parameters including a location ({right arrow over (x)}n) of an antenna element (n) of said phased array antenna, an orientation Δ
{right arrow over (x)}n of said antenna element (n) polarization of element (n) relative to the orientation of element (n), and a location of a transmitter {right arrow over (x)}1;identifying unknown parameters including weights (wn) of the elements (n), and vertical magnitude (Ev) and horizontal magnitude (EH) of each of said transmit signals; determining a receive signal at each of said antenna elements based on said transmit signals; defining six simultaneous equations with seven unknowns using one antenna element as a standard (p), a second antenna element (m, where m≠
p) and a third antenna element (n, where n≠
p and n≠
m);solving said six simultaneous equations for weights for every possible set of three antenna elements to find a vector of calibration weight (w) for each antenna element; and averaging said calibration weights (w) for each antenna element. - View Dependent Claims (2, 3, 4)
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5. A method for determining calibration constants for calibrating a receive only phased array antenna comprising the steps of:
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providing a pair of transmit signals with unknown polarization; selecting antenna element “
p” and
setting weight wp=1;determining full matrix equation (A) of size NP×
2P+N using all antenna elements and said pair of transmit signals with unknown polarization;performing a singular value decomposition on said matrix equation (A), wherein A=U*S*VT; multiplying matrix equation (A) by U−
1 and solving resulting equation for B=0 according to the relationship;
U−
1USVTw=U−
1B or SVTw=0;truncating matrix S to a square matrix of (2P+N×
2P+N);multiplying S and VT to yield a square matrix Ψ and
Ψ
w=0;reducing said square matrix Ψ
order by 1 by setting a last unknown, W(2P+N)=1, wherein said equation becomes Ξ
w=C;performing a matrix inversion to solve for reduced matrix and the set of unknown complex weights and a steering vector, wherein w=Ξ
−
1C and w=(w1, w2, . . . w2P+N−
1,
1); andrepeating the above steps until said calibration constants of all antenna elements p are determined.
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6. An apparatus comprising:
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a first transmitter and a second transmitter, each of said first transmitter and said second transmitter transmitting signals of different polarizations; a receive only phased array antenna system having a phased array antenna with linearly polarized antenna elements for receiving said transmitted signals of different polarizations from said first transmitter and said second said transmitter; and a processor coupled to outputs of said antenna elements for determining calibration constants for each of said antenna elements of said phased array antenna for calibrating said phased array antenna. - View Dependent Claims (7, 8)
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Specification