Underwater detection system for determining carrier frequencies of signals arriving from a wide area

An underwater detection system comprising:

• a carrier frequency measuring circuit including ultrasonic receiving means for receiving ultrasonic signals arriving from a wide searching area while rotating a first ultrasonic receiving beam and a second ultrasonic receiving beam, wherein the second ultrasonic receiving beam is delayed by a fixed angular displacement .theta. relative to the first ultrasonic receiving beam and the first ultrasonic receiving beam precedes the second ultrasonic receiving beam by a time period .tau. due to the angular displacement .theta.;
• detector means for detecting individual signals picked up by the two ultrasonic receiving beam produced by said ultrasonic receiving means;
• delay means for delaying the signal picked up by the first ultrasonic receiving beam by the time period .tau. at an output stage or one of said ultrasonic receiving means and said detector means;
• phase difference calculating means for determining the phase difference .DELTA..psi. between the two signals detected by said detector means;
• and calculating means for calculating carrier frequency f of the received ultrasonic signals from the phase difference determined by said phase difference calculating means in accordance with the equation f=.DELTA..psi./2.pi..tau.;
• a variance calculating circuit for deriving variance data indicating the degree of variations in carrier frequency f fed from said carrier frequency measuring circuit;
• a variance/color conversion circuit for reading out specific color data depending on individual values of variance data;
• and
• a display unit for presenting the color data.

An underwater detection system comprising:

• a carrier frequency measuring circuit including ultrasonic receiving means for receiving ultrasonic signals arriving from a wide searching area while rotating a first ultrasonic receiving beam accompanied by a second ultrasonic receiving beam, wherein the second ultrasonic receiving beam is delayed by a fixed angular displacement .theta. relative to the first ultrasonic receiving beam and the first ultrasonic receiving beam precedes the second ultrasonic receiving beam by a time period .tau. due to the angular displacement .theta.;
• detector means for detecting individual signals picked up by the two ultrasonic receiving beam produced by said ultrasonic receiving means;
• delay means for delaying the signal picked up by the first ultrasonic receiving beam by the time period .tau. at an output stage of one of said ultrasonic receiving means and said detector means;
• phase difference calculating means for determining the phase difference .DELTA..psi. between the two signals detected by said detector means;
• and calculating means for calculating carrier frequency f of the received ultrasonic signals from the phase difference determined by said phase difference calculating means in accordance with the equation f=.DELTA..psi./(2.pi..tau.);
• a filter-amplitude/color conversion circuit for selecting from amplitude data derived from the signals detected by said detector means only such amplitude data that lie within a desired frequency range and then reading out specific color data depending on individual values of the selected amplitude data;
• and
• a display unit for presenting the color data.

An underwater detection system comprising:

• a carrier frequency measuring circuit including ultrasonic receiving means for receiving ultrasonic signals arriving from a wide searching area while rotating a first ultrasonic receiving beam and a second ultrasonic receiving beam, wherein the second ultrasonic receiving beam is delayed by a fixed angular displacement .theta. relative to the first ultrasonic receiving beam and the first ultrasonic receiving beam precedes the second ultrasonic receiving beam by a time period .tau. due to the angular displacement .theta.;
• detector means for detecting individual signals picked up by the two ultrasonic receiving beam produced by said ultrasonic receiving means;
• delay means for delaying the signal picked up by the first ultrasonic receiving beam by the time period .tau. at an output stage or said ultrasonic receiving means or said detector means;
• phase difference calculating means for determining the phase difference .DELTA..psi. between the two signals detected by said detector means;
• and calculating means for calculating carrier frequency f of the received ultrasonic signals from the phase difference determined by said phase difference calculating means in accordance with the equation f=.DELTA..psi./2.pi..tau.;
• and
• an over-the-ground ship velocity compensation circuit for calculating carrier frequency fe representative of the over-the-ground velocity of a target itself by subtracting frequency f1 attributed to the over-the-ground ship velocity from each carrier frequency f fed from said carrier frequency measuring circuit.

An underwater detection system comprising:

• a carrier frequency measuring circuit including ultrasonic receiving means for receiving ultrasonic signals arriving from a wide searching area while rotating a first ultrasonic receiving beam and a second ultrasonic receiving beam, wherein the second ultrasonic receiving beam is delayed by a fixed angular displacement .theta. relative to the first ultrasonic receiving beam and the first ultrasonic receiving beam precedes the second ultrasonic receiving beam by a time period .tau. due to the angular displacement .theta.;
• detector means for detecting individual signals picked up by the two ultrasonic receiving beam produced by said ultrasonic receiving means;
• delay means for delaying the signal picked up by the first ultrasonic receiving beam by the time period .tau. at an output stage or said ultrasonic receiving means or said detector means;
• phase difference calculating means for determining the phase difference .DELTA..psi. between the two signals detected by said detector means;
• and calculating means for calculating carrier frequency f of the received ultrasonic signals from the phase difference determined by said phase difference calculating means in accordance with the equation f=.DELTA..psi./2.pi..tau.;
• and
• a through-the-water ship velocity compensation circuit for calculating carrier frequency few representative of the through-the-water velocity of a target itself by subtracting frequency f2 attributed to the through-the water ship velocity from each carrier frequency f fed from said carrier frequency measuring circuit.

An underwater detection system comprising:

• a carrier frequency measuring circuit including ultrasonic receiving means for receiving ultrasonic signals arriving from a wide searching area while rotating a first ultrasonic receiving beam accompanied by a second ultrasonic receiving beam, wherein the second ultrasonic receiving beam is delayed by a fixed angular displacement .theta. relative to the first ultrasonic receiving beam and the first ultrasonic receiving beam precedes the second ultrasonic receiving beam by a time period .tau. due to the angular displacement .theta.;
• detector means for detecting individual signals picked up by the two ultrasonic receiving beams produced by said ultrasonic receiving means;
• delay means for delaying the signal picked up by the first ultrasonic receiving beam by the time period .tau. at an output stage of said ultrasonic receiving means or said detector means;
• phase difference calculating means for determining the phase difference .DELTA..psi. between the two signals detected by said detector means;
• and calculating means for determining the phase difference between the two signals detected by said detector means;
• and calculating means for calculating carrier frequency f of the received ultrasonic signals from the phase difference determined by said phase difference calculating means in accordance with the equation f=.DELTA..psi./(2.pi..tau.);
• measuring means for measuring a Doppler frequency shift contained in the carrier frequency determined by said carrier frequency measuring circuit;
• and a velocity vector generating circuit for providing a velocity vector wherein, when a target at point P(x, y, z) in a rectangular coordinate system of which origin O is taken at the point of observation is moving at a velocity V.sub.0 (X.sub.0, Y.sub.0, Z.sub.0) relative to the origin O, said velocity vector generating circuit determines the velocity component V of said target at distance r in the direction of line OP based on the Doppler frequency shift determined by said measuring means, converts coordinates (x, y, z) of the point P and components (X.sub.0, Y.sub.0, Z.sub.0) of the velocity V.sub.0 into polar coordinate parameters (r, .alpha., .beta.) and (V.sub.0, A.sub.0, B.sub.0), respectively, produces an equation v=f (r, .alpha., .beta., V.sub.0, A.sub.0, B.sub.0), further produces similar equations for other targets moving at the same velocity V.sub.0 with said target, and estimates target velocity parameters V.sub.0, A.sub.0 and B.sub.0 at the point P from these equations using the least squares method.

An underwater detection system comprising:

• transmitting means for transmitting an ultrasonic signal into a wide area;
• receiving means for receiving ultrasonic echo signals arriving from all directions on the wide area;
• measuring means for measuring Doppler frequency shifts contained in the ultrasonic echo signals;
• and
• a velocity vector generating circuit for providing a velocity vector wherein, when a target at point P(x, y, z) in a rectangular coordinate system of which origin O is taken at the point of observation is moving at a velocity V.sub.0 (X.sub.0, Y.sub.0, Z.sub.0) relative to the origin O, said velocity vector generating circuit;
• determines the velocity component v of said target at distance r in the direction of line OP connecting the origin 0 and the P point based on the Doppler frequency shift determined by said measuring means,
• produces an equation v=f(OP, V.sub.0),
• produces similar equations for other targets moving at the same velocity V.sub.0 with said target, and
• estimates the target velocity V.sub.0 at the point P from these equations using the lease squares method.

An underwater detection system comprising:

• transmitting means for transmitting an ultrasonic signal into a wide area;
• receiving means for receiving ultrasonic echo signals arriving from all directions of the wide area;
• frequency measuring means for determining carrier frequencies of the received ultrasonic echo signals;
• frequency conversion means for converting the carrier frequencies into Doppler frequency shifts;
• variance calculating means for deriving variance data indicating the degree of variations in Doppler frequency shifts fed from said frequency conversion means;
• variance/color conversion means for generating specific color data depending on individual values of variance data;
• and
• a display unit for presenting the color data.

An underwater detection system comprising:

• transmitting means for transmitting an ultrasonic signal into a wide area;
• receiving means for receiving ultrasonic echo signals arriving from all directions of the wide area;
• frequency measuring means for determining carrier frequencies of the received ultrasonic echo signals;
• variance calculating means for deriving variance data indicating the degree of variations in carrier frequencies fed from said frequency measuring means;
• variance/color conversion means for generating specific color data depending on individual values of variance data;
• and
• a display unit for presenting the color data.

An underwater detection system comprising:

• transmitting means for transmitting an ultrasonic signal into a wide area;
• receiving means for receiving ultrasonic echo signals arriving from all directions of the wide area while rotating a first ultrasonic receiving beam and a second ultrasonic receiving beam;
• frequency measuring means for determining carrier frequencies of the received ultrasonic echo signals
• frequency conversion means for converting the carrier frequencies into Doppler frequency shifts;
• detector means for detecting the received ultrasonic echo signals;
• selection means for selecting from amplitude data derived from the detected signals fed from said detector means only such amplitude data that are associated with Doppler frequency shifts falling within a desired frequency range;
• amplitude/color conversion means for generating specific color-coded signals depending on individual values of the amplitude data selected by said selection means;
• and
• a display unit for presenting the color-coded signals.

An underwater detection system comprising:

• transmitting means for transmitting an ultrasonic signal into a wide area;
• receiving means for receiving ultrasonic echo signals arriving from all directions of the wide area;
• frequency measuring means for determining carrier frequencies of the received ultrasonic echo signals;
• detector means for detecting the received ultrasonic echo signals;
• selection means for selecting from amplitude data derived from the detected signals fed from said detector means only such amplitude data that are associated with carrier frequencies falling within a desired frequency range;
• amplitude/color conversion means for generating specific color-coded signals depending on individual values of the amplitude data selected by said selection means;
• and
• a display unit for presenting the color-coded signals.

An underwater detection system comprising:

• transmitting means for transmitting an ultrasonic signal into a wide area;
• receiving means for receiving ultrasonic echo signals arriving from all directions of the wide area;
• carrier frequency measuring means for determining carrier frequencies f of the received ultrasonic echo signals;
• storage means for storing individual carrier frequencies f fed from said carrier frequency measuring means;
• a display unit;
• designating means for specifying a desired area on said display unit;
• data readout means for reading out data on carrier frequencies f from such memory locations of said storage means that correspond to the area specified by said designating means;
• a frequency histogram generator for generating a histogram upon determining the distribution of carrier frequencies f based on the data read out by said data readout means;
• and
• display means for presenting the histogram on said display unit.

An underwater detection system comprising:

• transmitting means for transmitting an ultrasonic signal into a wide area;
• receiving means for receiving ultrasonic echo signals arriving from all directions of the wide area;
• carrier frequency measuring means for determining carrier frequencies f of the received ultrasonic echo signals;
• over-the-ground ship velocity compensation means for calculating carrier frequency fe representative of the over-the-ground velocity of a target itself by subtracting frequency f1 attributed to the over-the-ground ship velocity from each carrier frequency f fed from said carrier frequency measuring means.

An underwater detection system comprising:

• transmitting means for transmitting an ultrasonic signal into a wide area;
• receiving means for receiving ultrasonic echo signals arriving from all directions of the wide area;
• carrier frequency measuring means for determining carrier frequencies f of the received ultrasonic echo signals;
• through-the-water ship velocity compensation means for calculating carrier frequency fw representative of the through-the-water velocity of a target itself by subtracting frequency f2 attributed to the through-the-water ship velocity from each carrier frequency f fed from said carrier frequency measuring means.