Array Steering in a Layered Waveguide.
Abstract
The usual way to determine the direction of a radiating source using an array is to steer the array for maximum output. The steering can be done by time delays or by mechanically turning the array. The output of the array can be expressed as the sum of the time average of the products of the pressure (P(m)P(n)) observed at detectors m and n. The value of (P(m)(T(m))P(n)(T(n)) can be maximized by a proper choice of time delays T(m), T(n). This procedure is straightforward in an infinite homogeneous medium. If the medium is a layered waveguide, there are many more possibilities for submaxima of the P(m)P(n) terms. The normal-mode solution of the radiation field of a band limited noise point source in a layered waveguide was given by the author in J. Acoust. Soc. Am. 31, 1473-1479 (1959). The value of (P(m)(T(m) P(n)(T(n)) as a function of time delay is compared with the value of P(n)P(m) obtained with mechanical steering. For these calculations the noise source is assumed to have a bandwidth of 1/15 of the center frequency, and the depth of the water is assumed to be about 2 lamba over a thick layer of unconsolidated sediment. The number of maxima of the (P(m)(T(m) P(n)(T(n)) is related to the number of modes propagating in the waveguide if the steering is done with time delays.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 03, 1960
- Accession Number
- ADA068783
Entities
People
- C. S. Clay
Organizations
- Columbia University