Reconfigurable radio direction finder system and method
The reconfigurable radio direction finder system and method uses a reconfigurable antenna to electronically cycle through a plurality of different antenna configurations to determine a signal direction. Specifically, the reconfigurable antenna is cycled through N different antenna configurations, where N is an integer greater than one, where each antenna configuration has a pointing direction associated therewith defined by an elevation angle θ n of an n-th antenna configuration, where n is an integer between 1 and N, and an azimuthal angle φ n of the n-th antenna configuration. A received signal strength of the radio signal is measured for each of the antenna configurations as a power output of the n-th antenna configuration, P n . A spherical weighted directional mean vector (X DF , Y DF , Z DF ) is then estimated for the radio signal as X DF = 1 N ∑ n = 1 N P n cos ( ϕ n ) sin ( θ n ) , Y DF = 1 N ∑ n = 1 N P n sin ( ϕ n ) sin ( θ n ) and Z DF = 1 N ∑ n = 1 N P n sin ( θ n ) .
1. A reconfigurable radio direction finder system, comprising:
a substrate;
a planar array of patch antennae mounted on the substrate, wherein the planar array of patch antennae are arrayed in a rectangular grid having horizontal rows and vertical columns; and
a plurality of switches connecting each of the patch antennae to horizontally and vertically adjacent ones of the patch antennae to form a reconfigurable antenna, wherein individual ones of said plurality of switches are selectively opened and closed to form a corresponding antenna configuration of the reconfigurable antenna,
wherein the reconfigurable antenna is electronically cycled through N different antenna configurations, where N is an integer greater than one, wherein each said antenna configuration has a pointing direction associated therewith defined by an elevation angle θ n of an n-th antenna, where n is an integer between 1 and N, and by an azimuthal angle φ n of the n-th antenna, configuration, a set of received signal strength measurements and associated pointing directions being measured and saved such that an estimate of a spherical weighted directional mean vector for a radio signal, (X DF , Y DF , Z DF ) for first and second operational modes, is estimated as
X
DF
=
1
N
∑
n
=
1
N
P
n
cos
(
ϕ
n
)
sin
(
θ
n
)
,
Y
DF
=
1
N
∑
n
=
1
N
P
n
sin
(
ϕ
n
)
sin
(
θ
n
)
and
Z
DF
=
1
N
∑
n
=
1
N
P
n
sin
(
θ
n
)
,
where P n is a power output corresponding to a measured, received signal strength of the radio for the n-th antenna configuration.
2. The reconfigurable radio direction finder system as recited in claim 1 , wherein each of the switches is a micro-electromechanical switch.
3. The reconfigurable radio direction finder system as recited in claim 1 , wherein each of the switches is a radio frequency field effect transistor switch.
4. The reconfigurable radio direction finder system as recited in claim 1 , wherein an estimated elevation angle Ξ DF and an estimated azimuthal angle Φ DF of the radio signal are respectively determined as
Ξ
DF
=
cos
-
1
(
z
DF
(
X
DF
)
2
+
(
Y
DF
)
2
+
(
Z
DF
)
2
)
and
Φ
DF
=
tan
-
1
(
Y
DF
X
DF
)
.