Digital Bandpass Beamforming with the Discrete Fourier Transform
Abstract
A method is developed to form beam spectral estimates from a set of signals sampled from hydrophone outputs of an acoustic array. The signals must be frequency band limited over an interval (Wo,Wo+W) and sampled over a time interval T. A savings of (Wo/W) + 1 in data storage and computation time is realized over conventional beam forming analysis methods employing sampling rates equal to twice the highest frequency in the signal band. Any set of delays ti may be used and the beamforming error determined as long as ti<T/2. The computed beam spectra can be made arbitrarily close to the actual beam spectra by choosing (a) a large number of points to be analyzed, (b) small input signal amplitudes at the end points of the time interval T, and (c) small actual spectrum amplitudes near f=Wo and f=Wo+W. This procedure would be particularly applicable to future sonar systems employing digital circuitry to beamform and spectrum analyze on-line.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 26, 1972
- Accession Number
- AD0737191
Entities
People
- David T. Deihl
Organizations
- United States Naval Research Laboratory