Accession Number : ADD013175

Title :   Constant Beamwidth Frequency Independent Acoustic Antenna.

Descriptive Note : Patent, Filed 11 Apr 83, patented 30 Oct 84,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC

Personal Author(s) : Sternberg,Robert L

Report Date : 30 Oct 1984

Pagination or Media Count : 6

Abstract : A frequency independent periodic acoustic device is utilized for the transmission or reception of underwater sound. A key element of the device is a particularly shaped plate or diaphragm, called a filter plate, made of stainless steel or other material having suitable acoustic properties. The filter plate on being placed in front of any plane wave receiving or transmitting transducer acts automatically to make the beamwidth of the diffraction pattern of the combined device constant, regardless of frequency. This is achieved by automatically making the effective aperture diameter of the filter plate-transducer combination a constant multiple of the acoustic wavelength of the sound in the underwater medium. When used in conjunction with a scannable transducer such as an acoustic lens and the retina device the filter plate produces a directional, scannable, substantially constant beamwidth diffraction pattern for radiation or reception of underwater acoustic signals. The thickness of the plate at both its center and outer operative diameter are determined by the wavelengths of the respective highest and lowest frequencies to be utilized.

Descriptors :   *PATENTS, *SONAR PROJECTORS, *TRANSDUCERS, *APERTURES, *DIFFRACTION, ACOUSTIC WAVES, UNDERWATER ACOUSTICS, PLANE WAVES, ACOUSTIC WAVES, ACOUSTIC PROPERTIES, UNDERWATER SOUND, ACOUSTIC SIGNALS, CONSTANTS, TRANSMITTING, PATTERNS, RECEPTION

Subject Categories : Acoustic Detection and Detectors
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE