Controlling the directivity of a circular array of acoustic sensors
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorDavid A. Smith
Life of this patent
Estimating the term…
Abstract
Forming and directive control of the beam in a circular sonar array without ime delay or phase shift networks. Predetermined weighting coefficients are used to scale sensor outputs that are summed in an add-only processor to provide a weighted sum output characteristic of target position relative to the main receiving axis of the array.
Claims5
A method for controlling the directivity of a circular array of acoustic sensors so as to be characterized by a formed beam along a main receiving axis, said method comprising the steps of:
- providing a circular array of radius R including sensors 1 through N disposed on one side of a xeroth sensor on said main receiving axis and -1 through -N disposed on the other side of said zeroth sensor, said sensors being equally spaced aximuthally from one another;
- imposing a set of weighting coefficients A(n) on the outputs of said sensors, said coefficients A(n) each comprising a product of a signal replica factor A.sub.1 (n)=cos [2.pi.R(1-cos .alpha..sub.n)], a sensor density correction factor A.sub.2 (n)=cos .alpha..sub.n, and an aperture illumination factor A.sub.3 (n)=cos .alpha..sub.n, where .alpha..sub.n is the angle of the nth sensor from said main receiving axis, so as to provide weighted sensor outputs;
- and adding said weighted sensor outputs such that the weighted sum output ##EQU3## results in formation of a beam .vertline.E*(.theta.,t).vertline., where the bars indicate the magnitude of the sum and e.sub.n *(.theta.,t) is the complex voltage output of the nth sensor when a target is at an angle .theta. from the main receiving axis.
A sonar system characterized by a formed beam along a main receiving axis, said system comprising:
- a circular transducer array including a predetermined number of electroacoustic transducer elements, said elements being equally spaced from one another along an arc having a predetermined radius R and extending N elements to both sides of said main receiving axis;
- a plurality of signal scaler means, each responsive to the output of an individual one of said elements, for providing a corresponding plurality of weighted output signals scaled in accordance with predetermined weighting coefficients A(n), each of which is the product of a signal replica factor A.sub.1 (n), a density correction factor A.sub.2 (n), and an aperture illumination factor A.sub.3 (n), where
- A.sub.1 (n)=cos [2.pi.R(1-cos .alpha..sub.n)],
- A.sub.2 (n)=cos .alpha..sub.n,
- A.sub.3 (n)=cos .alpha..sub.n,
- and
- .alpha..sub.n is the angle of the nth sensor from said main receiving axis;
- and
- summing means, responsive to said weighted output signals for providing a weighted sum output signal ##EQU4## where .theta. is the angle of incidence of acoustic energy relative to said main receiving axis and e.sub.n *(.theta.,t) is the complex voltage output of the nth sensor when a target is at said angle .theta..
Dependencies are inferred from the claim text.