1622 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 53, NO. 5, MAY 2005
L-Shape 2-Dimensional Arrival Angle Estimation
With Propagator Method
Nizar Tayem and Hyuck M. Kwon, Senior Member, IEEE
Abstract—It is known that computational loads of the propa-
gator method (PM) can be significantly smaller, e.g., one or two
order, than those of MUSIC and ESPRIT because the PM does not
require any eigenvalue decomposition (EVD) of the cross-correla-
tion matrix and singular value decomposition (SVD) of the received
data. However, the PM of the parallel shape array has nonnegli-
gible drawbacks such as 1) requirement of pair matching between
the 2-D azimuth and elevation angle estimation which is an exhaus-
tive search and 2) estimation failure problems when elevation an-
gles are between 70
and 90 . The purpose of this paper is to show
a way to remove these problems in the PM without additional com-
putational loads. This paper will employ one or two L-shape arrays
because the parallel shape used in the PM may cause the aforesaid
problems. Simulation results verify that the PM with one or two
L-shape configurations can remove these problems and improve
the performance of the PM significantly, e.g., almost 5 dB in signal
to noise ratio for the parameters used in this paper.
Index Terms—Antenna array, direction-of-arrival angle (DOA)
estimation, propagator method (PM), Smart antenna.
I. INTRODUCTION
E
STIMATION of two-dimensional (2-D) direction-of-ar-
rival angles (DOA) has received a significant amount of
attention over the last several decades. It has also played an
important role in array signal processing areas such as radar,
sonar, radio astronomy, and mobile communication systems.
The most popular techniques for DOA estimations are the
classical subspace methods such as the MUSIC [1]–[4] and
ESPRIT [5]–[8] algorithms. But these algorithms employ either
the eigenvalue decomposition (EVD) of cross spectral matrix
(CSM) or singular value decomposition (SVD) of the received
data matrix (RMD). Using these techniques, the computational
complexity is costly and high especially when the number of
sources and antenna elements are large. The computational
complexity of ESPRIT can be in the order of
multiplication in calculating the eigen decomposition for a
covariance matrix with an
-element array and snapshots.
Marcos and co-workers [9]–[12] have suggested the so-called
“propagator” method (PM) for array signal processing without
any eigen decomposition. The computational load of the PM is
in
, where is the number of incident sources.
Manuscript received June 10, 2004; revised October 20, 2004. This work was
supported by the U.S. Army Research Laboratory and the U.S. Army Research
Office under the Grant DAAD19-01-10537.
The authors are with the Department of Electrical and Computer Engineering,
Wichita State University, Wichita, KS 67260-0044 USA (e-mail: natayem@wi-
chita.edu; hyuck.kwon@wichita.edu).
Digital Object Identifier 10.1109/TAP.2005.846804
However, the PM of the parallel-shape array in [13] requires
pair matching between the 2-D azimuth and elevation angle esti-
mation
and can have an estimation failure
1
problem when
elevation angles are between 70
and 90 . The elevation angle
in typical mobile communications is in the range of 70
and
90
. Thus, the application of the PM of the parallel-shape array
to mobile communications should be reconsidered. The parallel
shape array used in the PM [13] may cause the aforesaid prob-
lems.
The idea of using L-shaped arrays is not new, e.g., [14]. But,
the L-shape array in our paper is different from that in [14]. In
our paper, the elements are placed on the
or axes
whereas the elements in [14] are on the
axis. In addition,
the L-shape in [[14], (10)] uses the same DOA estimation equa-
tions as the ones in [13, eq. (14)] and [15, (18)]. Therefore, the
L-shape in [14] has the same pair matching and failure problems
as the ones in [13] and [15].
The purpose of this paper is to show how to remove these
problems in the PM without additional computational loads.
This paper will employ a configuration of one or two L-shape
arrays, which allow no pair matching between the azimuth angle
estimate
for source and the elevation angle estimate for
source
. In addition, using an L-shape array shows no elevation
angle estimation failure even if the elevation angle is between
70
and 90 . Furthermore, the one L-shape array in the
plane shows several other advantages over the parallel-shape
array but has a failure problem similar to the one in [13] when
the azimuth angle is between 0
and 20 . However, with the pro-
posed two L-shape arrays in the
and planes, we can
completely remove the failure problem and reduce the RMSE
significantly.
Section II presents the system model and a proposed algo-
rithm, i.e., the PM with the one L-shape array configuration in
the
plane. Section III presents another proposed algorithm,
i.e., the PM with two L-shape arrays in the
and planes.
Section IV shows simulation results. And Section V concludes
the paper.
II. P
ROPOSED PM W
ITH O
NE L-SHAPE ARRAY
Fig. 1(a) shows the one L-shape array configuration which
uses the
plane instead of the plane used in [14]. Each
linear array consists of
elements. The element placed at
the origin is common for referencing purpose. Let
and be
the two sub-arrays of the linear array in the
axis, and let and
be the two sub-arrays of the linear array in the axis. Each
1
The definition of estimation failure is the event that the estimated angle is in
a complex form instead of a real. This happens when the absolute argument of
the arc-sine or arc-cosine function is greater than 1.
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