Automatic underwater null steering

In an underwater sound transmission system, the improvement comprising:

• a pair of dipole hydrophones, said hydrophones being positioned so that their sensitivity patterns are orthogonal with respect to each other, each of said hydrophones being adapted to receive sound energy approaching at an angle .phi. to develop a hydrophone output signal V,
• said system developing an output signal V.sub.o in response to said hydrophone output signals V,
• computing means connected to receive said hydrophone output signals V,
• said computing means being adapted to derive functions of an angle .phi..sub.o from said signals V,
• a pair of multiplying means for multiplying each hydrophone output signal V by a respective function of .phi..sub.o to generate a pair of product signals V.sub.1 sin .phi..sub.o and V.sub.2 cos .phi..sub.o,
• combining means connected to said multiplying means to combine said product signals into the system output signal V.sub.o, the angle .phi..sub.o being such that interference noise in said output signal V.sub.o is automatically minimized,
• said combining means including inverting means for inverting a product signal V f (.phi..sub.o),
• said combining means including summing means for summing said product signals V f (.phi..sub.o),
• said summing means including,
• a first summing circuit for summing one of said product signals V.sub.2 cos .phi..sub.o and an inverted product signal -V.sub.1 sin .phi..sub.o to derive a first system output signal V.sub.01, and
• a second summing circuit for summing two of said product signals V.sub.2 cos .phi..sub.o and V.sub.1 sin .phi..sub.2 to produce a second system output signal V.sub.02.