Communications – electrical: acoustic wave systems and devices – Echo systems – Distance or direction finding
Reexamination Certificate
1999-03-24
2001-01-23
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Echo systems
Distance or direction finding
Reexamination Certificate
active
06178140
ABSTRACT:
BACKGROUND OF THE INVENTION
According to the earlier patent application two groups of transducers are provided side by side looking to the target whose location is sought. Each group of transducers generates a complex output signal
L
and
R
, respectively. A magnitude summation signal R
BSum
=|
L
|+|
R
| is derived from the absolute values |
L
| and |
R
| of the transducer group output signals. Furthermore, a complex differential signal
D
=
L
−
R
is derived from said transducer group output signals. The absolute value or magnitude R
D
=|
D
| of the differential signal is then determined. Finally, a resulting output signal R
HYP
is calculated by either dividing said magnitude summation signal R
BSum
by the magnitude |
D
| of the differential signal, or by subtracting said magnitude |
D
| of said differential signal from the magnitude summation signal R
BSum
. Other embodiments of said earlier patent application calculate said resulting output signal R
BSum
by either dividing the double magnitude 2|
L
| or 2|
R
| by said magnitude |
D
| of the differential signal, or by subtracting said magnitude R
D
the differential signal from said double magnitude 2|
L
| or 2|
R
| of the complex output signal
L
or
R
or one of said groups of transducers. Due to this type of signal processing all side lobes of the magnitude summation signal R
BSum
or the double magnitude signal 2|
L
| (or 2|
R
|) of said transducer group output signal, and in particular the otherwise specifically disturbing first sided lobes, are located at the same angular positions as the side lobes of said differential signal. Therewith, those side lobe signals cancel out each other when forming a signal quotient (ratio) or forming a signal difference, as described above. This method therefore results in improved side lobe suppression and enhanced beam focussing. The content of said earlier patent application is herewith included by reference into the disclosure of the present invention.
OBJECT OF THE INVENTION
It is an object of the present invention to improve the three-dimensional or spatial focussing of the beam in all planes which contain the main beam direction, and to achieve a better side lobe suppression around the beam in all three dimensions.
SUMMARY OF THE INVENTION
These and other objects of the invention are achieved with 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 &phgr; between said first and second axis is choosen &phgr;≠0, preferably &phgr;=90°, 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
and
R
of the first pair of transducer groups according to equation
R
Bsum(xz)
=a·|
L
|+b·|
R
|, with
a+b=
2; (7a)
d) calculating a second summation signal R
Bsum(yz)
from the absolute values |
V
| and |
H
| of the complex output signals
V
and
H
of the second pair of transducer groups according to equation
R
Bsum(yz)
=a′·|
V
|+b′·|
H
|, with
a′+b′=
2; (7b)
e) calculating a first differential signal
D(xz)
=
L
−
R
from said complex output signals of the first pair of transducer groups, and deriving the absolute value R
D(xz)
=|
L
−
R
| thereof;
f) calculating a second differential signal
D(yz)
=
V
−
H
from said complex output signals of the second pair of transducer groups, and deriving the absolute value R
D(yz)
=|
V
−
H
| thereof;
g) calculating a first plane (xz) output signal according to equation
R
HYP(xz)
(
n
)=[(
R
Bsum(xz)
)
n
−(
R
D(xz)
)
n
]
1
, with 0
<n<
2; (9a)
h) calculating a second plane (yz) output signal according to equation
R
HYP(yz)
(
m
)=[(
R
Bsum(yz)
)
m
−(
R
D(yz)
)
m
]
1/m
, with 0
<m<
2; (9b)
i) calculating a 3D(xyz) combined output signal according to equation
R
HYP
(
xyz
)
(
n
,
m
)
=
[
c
(
R
HYPxz
(
n
)
)
1
/
q
+
d
(
R
HYPyz
(
m
)
)
1
/
q
2
]
q
(
10
)
with 0<q<∞, 0≦c≦2, 0≦d≦2, and c+d=2.
Preferably, a=b=1 or a=0, or b=0, and 1≦q≦10, and c=d=1.
The invention also is 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 &phgr; between said first and second axis is choosen &phgr;≠0, preferably &phgr;=90°, said method comprising the following steps performed by a signal processing unit;
c) evaluating a first summation signal R
Bsum(xz)
from the absolute values |
L
| and |
R
| of the complex output signals
L
and
R
of the first pair of transducer groups according to equation
R
Bsum(xz)
a·|
L
|+b·|
R
|, with
a+b=
2; (7a)
d) calculating a second summation signal R
Bsum(yz)
from the absolute values |
V
| and |
H
| of the complex output signals
V
and
H
of the second pair of transducer groups according to equation
R
Bsum(yz)
a′·|
V
|+b′·|
H
|, with
a′+b′=
2; (7b)
e) calculating a first differential signal
D(xz)
=
L
−
R
from said complex output signals of the first pair of transducer groups, and deriving the absolute value R
D(xz)
=|
L
−|
R
| thereof;
f) calculating a second differential signal
D(yz)
=
V
−
H
from said complex output signals of the second pair of transducer groups, and deriving the absolute value R
D(yz)
=|
V
−
H
| thereof;
g) calculating a first plane (xz) output signal according to equation
R
HYP(xz)
(
n
)=[(
R
Bsum(xz)
)
n
−(
R
D(xz)
)
n
]
1
, with 0
<n<
2; (9a)
h) calculating a second plane (yz) output signal according to equation
R
HYP(yz)
(
m
)=[(
R
Bsum(yz)
)
m
−(
R
D(yz)
)
m
]
1/m
, with 0
<m<
2; (9b)
i) calculating a 3D(xyz) combined output signal according to equation
R
HYPxyz
(
n,m
)=[(
R
HYPxz
(
n
)·
R
HYPyz
(
m
))
½
(11)
In another aspect, the invention comprises 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 &phgr; between said first and second axis is choosen &phgr;≠0, preferably &phgr;=90°, said method comprising the following steps performed by a signal processing;
c) calculating a first summation signal R
Bsum(xz)
from the absolute values |
L
| and
Dubno Herbert
L-3 Communications Elac Nautik GmbH
Pihulic Daniel T.
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