Dependence on Aperture Angle of Array Gain against Flow Noise for Cylindrical and Spherical Arrays of Directional Elements
Abstract
When receiving arrays are placed on air backed structures in water, the effect of the structure or baffle is to alter the response of the hydrophones from their free field characteristics. The exact response characteristics are complicated and frequency dependent. Typically the response is reduced near grazing incidence. When a beam is formed for maximum response in a selected direction, increasing the aperture to include elements for which the selected beam is near grazing, is inefficient in increasing array signal gain and may actually lead to a loss in signal-to-noise ratio. The array gain dependence upon aperture angle for cylindrical and spherical arrays has been presented for parametric families of effective element directivities. Both uniform and optimum shadings have been considered. Results have been presented in the form of parametric curves which can be used in system design tradeoffs. For the spherical array increasing aperture angle has about twice the payoff as for the cylindrical array since both azimuthal and vertical resolution depend on aperture angle. In practice, since the sphere may be used over a wide range of azimuths and must have elements for those azimuths, it may be desirable to take advantage of those elements by increasing the aperture in the horizontal dimension without adding elements near the top and bottom.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1983
- Accession Number
- ADA131144
Entities
People
- H. Cox
- J. M. Steele
Organizations
- BBN Technologies