Method for three-dimensional beam forming in direction finding systems

• US 6,178,140 B1
• Filed: 03/24/1999
• Issued: 01/23/2001
• Est. Priority Date: 05/19/1998
• Status: Expired due to Term

• Current Assignee: Wärtsilä ELAC Nautik GmbH (Cohort Plc)
• Original Assignee: Wärtsilä ELAC Nautik GmbH (Cohort Plc)
• Inventors: Schlieter, Heiko
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US09/275,650
• Time in Patent Office: 671 Days
• Field of Search: 367/103, 367/119, 367/138, 342/195, 342/152, 342/149
• US Class Current: 367/103
• CPC Class Codes: G01S 3/06 Means for increasing effective directivity, e.g. by combining signals having differently oriented directivity characteristics or by sharpening the envelope waveform of the signal derived from a rotating or oscillating beam antenna comparing amplitude of signals having differently oriented directivity characteristics to determine direction G01S3/16, G01S3/28
• CPC Class Codes: G01S 3/32 derived from different combinations of signals from separate antennas, e.g. comparing sum with difference
• CPC Class Codes: G01S 3/8034 wherein the signals are derived simultaneously
• CPC Class Codes: H01Q 21/245 provided with means for varying the polarisation polarising devices H01Q15/24; tracking by comparing linear polarisation compounds G01S3/146; reducing depolarisation effects H04B7/00; polarisation diversity H04B7/10
• CPC Class Codes: H01Q 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes precedence

Abstract

For improving 3D focussing and side lobe suppression in a direction finding system identical groups of transducers are provided at each side of a first and a second axis, which are inclined by an angle 0°≠ψ<180°, preferable ψ=90°. A first magnitude summation signal is derived from the first pair of transducer groups associated with the first axis and a second magnitude summation signal is derived from the second pair of transducer groups associated with the second axis. Furthermore, a differential signal is derived between the complex output signal of each pair of transducers. For each axis the absolute value of said differential signal is subtracted from the associated magnitude summation signal. The resulting two output signals, associated with said two axis, are then combined to finally obtain a three-dimensionally focussed beam pattern.

Claims

1. A method of beam forming in direction finding systems having at least three identical groups of transducers, with each group comprising at least one transducer, wherein

a) a first pair of identical groups of transducers has one group each located at both sides of a first axis (y);

b) a second pair of identical groups of transducers has one group each located at both sides of a second axis (x), wherein the angle ψ

between said first and second axis is choosen ψ

≠

0, said method comprising the following steps performed by a signal processing unit;

c) calculating a first summation signal R_BSum(xz) from the absolute values |_L| and |_R| of the complex output signals _L, _R of the first pair of transducer groups according to equation

2. The method of claim 1, wherein a=b=1.

3. The method of claim 1, wherein a=0 or b=0.

4. The method of claim 1, wherein 1≦

q≦

10.

5. The method of claim 4, wherein c=d=1.

11. The method of claim 1 wherein ψ

=90°

.

6. A method of beam forming in direction finding systems having at least three identical groups of transducers, with each group comprising at least one transducer, wherein

a) a first pair of identical groups of transducers has one group each located at both sides of a first axis (y);

b) a second pair of identical groups of transducers has one group each located at both sides of a second axis (x), wherein the angle ψ

between said first and second axis is choosen ψ

≠

0, said method comprising the following steps performed by a signal processing unit;

c) calculating a first summation signal R_Bsum(xz) from the absolute values |_L| and |_R| of the complex output signals _L, _R of the first pair of transducer groups according to equation

9. The method of claim 6 wherein ψ

=90°

.

7. A method of beam forming in direction finding systems having at least three identical groups of transducers, with each group comprising at least one transducer, wherein

a) a first pair of identical groups of transducer has one group each located at both sides of a first axis (y);

b) a second pair of identical groups of transducers has one group each located at both sides of a second axis (x), wherein the angle ψ

between said first and second axis is choosen ψ

≠

0, said method comprising the following steps performed by a signal processing unit;

c) calculating a first summation signal R_Bsum(xz) from the absolute values |_L| and |_R| of the complex output signals _L, _R of the first pair of transducer groups according to equation

10. The method of claim 7 wherein ψ

=90°

.

8. A method of beam forming in sonar direction finding systems having two identical groups of transducers, with each group comprising at least one transducer, and with one group each mounted aboard of a ship at both sides of a vertical plane which includes the travelling direction of the ship, said method comprising the following steps performed by a signal processing unit:

a) deriving a complex left-side synthetic aperture sonar signal _Lsas from the output signals of the transducers of the transducer group provided at the left side of said vertical plane;

b) deriving a complex right side synthetic aperture sonar signal _Rsas from the output signals of the transducers of the transducer group provided at the right side of said vertical plane;

c) calculating a 3D(xyz) combined output signal according to equation