Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
1999-04-15
2001-04-17
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S157000
Reexamination Certificate
active
06218985
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to steered beam antenna arrays. More specifically, but without limitation thereto, the present invention relates to a method for selecting amplitudes and phases of a drive signal input to elements of a multiple element antenna to approximate a radiation pattern having a desired beamwidth, sidelobe level and gain.
Multiple element antennas, or antenna arrays, are used in many commercial and military systems. An example of such an antenna array used on surface ships is a circular array of 64 dipoles, where each dipole is inside a cavity. The power distribution and phase shift of the transmit signal input to each antenna element is typically controlled by phase shifters, switches, and a waveguide. The parameters of beamwidth, sidelobe level and gain are currently improved by increasing the size of the array. The larger array size has the disadvantage of consuming valuable space on the uppermost areas of the ship. Previous methods for optimizing performance of an antenna array calculate the amplitude and phase drive current at each antenna element to generate a desired beam pattern. These methods typically place the largest amplitudes in the center of the array and the smallest amplitudes at the ends of the array. A disadvantage of these methods is that a large array diameter is required to achieve stringent beamwidth, sidelobe level, and gain parameters.
A need therefore continues to exist for a method for meeting goals of beamwidth, sidelobe level, and gain parameters of an antenna array while decreasing the size of the array.
SUMMARY OF THE INVENTION
The method of the present invention is directed to overcoming the problems described above and may provide further related advantages. No embodiment of the present invention described herein shall preclude other embodiments or advantages that may exist or become obvious to those skilled in the art.
The method for steering a beam of an antenna array of the present invention minimizes a least squares approximation of an error function of a desired radiation pattern relative to an antenna array pattern calculated from a known radiation pattern for each antenna element.
An advantage of the method of the present invention is that a higher gain and narrower beamwidth may be obtained with a reduced array aperture.
Another advantage is that beam steering of an antenna array may be conveniently and rapidly implemented.
Yet another advantage is that the beam pattern may be preserved during transmissions of different frequencies by changing amplitude weights and phase shift angles for each antenna element in real time.
The features and advantages summarized above in addition to other aspects of the present invention will become more apparent from the description, presented in conjunction with the following drawings.
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Blum Theodore M.
Fendelman Harvey
Lipovsky Peter A.
The United States of America as represented by the Secretary of
Whitesell Eric James
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