System and method for measuring wave directional spectrum and wave height

A Doppler sonar system for measuring the directional spectrum of waves in a fluid medium having a substantially planar surface, comprising:

• a signal generator for generating a transmitted signal;
• a plurality of transmitting transducers operatively connected to the signal generator, the transducers generating acoustic beams based on the transmitted signal and projecting the beams into the fluid medium, the acoustic beams further having an angular relationship to the surface of the fluid medium;
• a plurality of receiving transducers for receiving samples from a plurality of range cells located substantially within each of the acoustic beams, and producing a received signal relating to the samples, wherein at least two of the range cells in one of the acoustic beams are at different horizontal locations relative to a vertical axis;
• a signal processor capable of processing the received signal;
• and
• a computer program, executed at least in part on the signal processor, for calculating the directional spectrum associated with the waves based on the received signal, wherein the computer program further utilizes a sensitivity vector as part of the calculation of the directional spectrum.

A system for measuring the directional spectrum of waves in a fluid medium, comprising;

• a signal generator generating signals associated with one or more acoustic pulses;
• a plurality of transducers transmitting the acoustic pulses into the fluid medium in respective acoustic beams, the transducers further receiving echoes generated by the acoustic pulses from a plurality of range cells located within each of the acoustic beams, wherein at least two of the range cells in one of the acoustic beams are at different horizontal locations relative to a vertical axis;
• and
• a signal processor receiving signals indicative of the received echoes, and calculating a sensitivity vector associated with the first and second transducers.

A method of calculating the directional spectrum of a wave in a fluid medium utilizing a plurality of acoustic transducers, comprising:

• generating a plurality of acoustic beams from the transducers, each of the beams having range cells located at least partly therein, wherein at least two of the range cells in one of the acoustic beams are at different horizontal locations relative to a vertical axis;
• receiving echoes produced within an array consisting of two or more of the range cells;
• processing signals indicative of the received echoes;
• generating a sensitivity vector, the vector being based on the signals and the geometry of the array of range cells;
• and
• estimating the directional spectrum of the wave based on the signals and the sensitivity vector.

A method of measuring the directional spectrum of waves in a fluid medium using a sonar system having an upward or downward looking transducer configuration, comprising:

• generating one or more acoustic beams from the transducer configuration;
• measuring the current velocities within a plurality of range cells in each of the acoustic beams, wherein at least two of the range cells in one of the acoustic beams are at different horizontal locations relative to a vertical axis;
• forming a sensitivity vector related to the transducer configuration using a linear wave model;
• and
• forming a wave directional spectrum matrix using the measured current velocities and the sensitivity vector.

A computer program used with a sonar system for calculating the two-dimensional directional spectrum of a wave in a fluid medium from at least one set of received echoes, comprising:

• a data processor for processing the signals representative of the received echoes from a plurality of range cells, wherein at least two of the range cells in a single beam are at different horizontal locations relative to a vertical axis;
• means for calculating a non-directional wave height spectrum from the signals processed by the data processor;
• means for generating a cross-spectral matrix from the signals;
• a sensitivity vector generator, wherein a sensitivity vector is generated relating to the configuration of the transducers of the sonar system;
• and
• a two-dimensional directional spectrum estimator, the estimator calculating the directional spectrum from the non-directional wave height spectrum, the cross-spectral matrix, and the sensitivity vector.

A method of measuring the directional spectrum of waves in a fluid medium using a sonar system having an upward or downward looking transducer configuration, comprising:

• generating a plurality of acoustic beams from the transducer configuration;
• measuring current velocities within a plurality of range cells in each of the acoustic beams, wherein at least two of the range cells in one of the acoustic beams are at different horizontal locations relative to a vertical axis;
• calculating values of wave frequency and wave number magnitude according to a linear wave dispersion relation;
• forming a wave height spectrum matrix using the measured current velocities
• forming a cross-spectral matrix as a function of wave frequency;
• generating a sensitivity vector related to the transducer configuration of the sonar system;
• using a maximum likelihood method to generate directional spectra for each observed frequency from the cross-spectral matrix and sensitivity vector;
• and
• constructing a complete two-dimensional wave directional spectrum from the directional spectra for each observed frequency.