Sonar system for current meter and doppler log

A sonar system for current meter and doppler log, comprising:

• a set of transducers situated on a base in a base plane;
• a feed device for feeding said set of transducers with signals exhibiting a first and second frequency at distinct phases to obtain in at least a first emission plane perpendicular to said base plane, a first emission lobe at the first frequency forming an angle .alpha. with a perpendicular to said base plane and a second emission lobe at the second frequency forming an angle -.alpha. with said perpendicular;
• and
• a summation device for performing summation of signals received by the transducers to obtain a first reception signal comprising signals at said first and second frequencies in said first emission plane;
• wherein:
• said set of transducers are aligned in rows and spaced apart by a predetermined distance,
• said rows are grouped into pairs of rows,
• each pair of rows has transducers of a common polarity;
• and
• adjacent of said pairs of rows of transducers have inverted polarities;
• and
• said feed device delivers signals A and B at a first frequency and 90.degree. out of phase in a first sequence A, B, A, B . . . to alternating rows of transducers such that a row being fed signal A to each transducer of that row has at least one adjacent row being fed signal B to each transducer of said at least one adjacent row, and subsequently delivers signals A' and B' at a second frequency and 90.degree. out of phase in a second sequence A', -B', A', -B' . . . to alternating rows of transducers such that a row being fed signal A' to each transducer thereof has adjacent rows being fed signal -B' to each transducer thereof, thereby determining said first and second emission lobes.