Vol. 119 (2011)
ACTA PHYSICA POLONICA A
Physical Aspects of Microwave and Radar Applications
Antenna Beam Broadening in Multifunction
Phased Array Radar
R. Fatemi Mofrad∗and R.A. Sadeghzadeh
Electrical & Computer Engineering Department, K.N. Toosi University of Technology, Tehran, Iran
A phased array antenna is designed for multifunction phased array radar simulation test bed.
element pattern, mutual coupling between elements, phase quantization, amplitude and phase error and elements
failure rates on array pattern are discussed.Target angle measurement and side lobe cancelling, in order to
reduce jamming power through side lobes, is illustrated in this antenna. Also antenna beam width is broadened
with different methods and compared with narrow beam characteristics.
ening factors, beam broadening may lead to a better coverage and power efficiency relative to narrow beam antenna.
It is shown that, for special broad-
PACS: 84.40.Ba, 84.40.Xb, 84.40.Ua
Phased array antennas have matured rapidly in recent
years and this technology is set to become the norm in
complex and advanced radar systems.
steer the radar beam electronically allows a combination
of functions, such as tracking, surveillance and weapon
guidance, which were traditionally performed by dedi-
cated individual radars. This new type of radar is called
multifunction array radar (MFAR). In these radars, ef-
fect of different antenna beam characteristics (e.g. beam
width) or tracking algorithms on the overall radar per-
formance need to be done based on realistic simulations,
because these sophisticated radars cannot be tested com-
pletely in real world. These realistic simulations should
have two main properties: first to include different as-
pects of real operational scenarios facing MFAR as much
and accurate as possible. The second is that these sim-
ulations should provide the facility to model different
part of a MFAR in order to evaluate the performance
of each section in the radar as a whole system (to con-
sider the interaction between subsystems). MFAR simu-
lation test bed is a software tool for MFAR designers to
design and evaluate the performance of such kind of so-
phisticated radars . In the MFAR simulation test bed,
active phased array radar, with specification in Table I,
is considered as a pilot for different radar resource man-
agement, target tracking and beam forming algorithms
comparison and development. In this simulation test bed,
transmitting and receiving chain, antenna structure and
signal processing algorithms are fixed. User may write his
or her own radar resource management, target tracking
and beam forming algorithms and after defining appro-
priate operational scenarios, assess results of the designed
algorithms. The most important part of this simulation
test bed is a phased array antenna. That is an active
The ability to
∗corresponding author; e-mail: email@example.com
phased array with about 5000 elements. It is assumed
that digital beam forming is possible at element level and
so designer may design appropriate beam forming algo-
rithms and evaluate the results on radar performances.
angle tracking accuracy
antenna scanning range in az. and el.
antenna tilt angle
sum pattern side lobe level
difference pattern side lobe level
number of T/R modules
In this paper, a narrow pencil beam with capability to
measure azimuth and elevation angles of target and side
lobe cancelling in the presence of jamming is designed
for this simulation test bed. Effect of element pattern,
phase quantization, amplitude and phase error, elements
failure rates on array pattern and mutual coupling be-
tween elements, are presented. The narrow beam width
is usually designed to meet tracking requirements of a
MFAR (resolution and accuracy). Search of a large area
by this narrow beam becomes too time consuming. In
these occasions antenna beam broadening is useful.
In this paper antenna beam width is broadened and
compared with narrow beam characteristics. It is shown
that, for special broadening factors, beam broadening
may lead to a better coverage and power efficiency rela-
tive to narrow beam antenna.
R. Fatemi Mofrad, R.A. Sadeghzadeh
Fig. 14. Beam power efficiency vs. broadening factor.
Fig. 15.Coverage area of different patterns.
Beam broadening is also possible with amplitude and
amplitude–phase tapering methods.
ods yield better side lobe levels and lower error between
required and achieved patterns.
before, amplitude tapering would lead to power losses.
Among these two methods, amplitude–phase tapering
yields better side lobe levels and lower dynamic range
between elements amplitudes. Lower dynamic range be-
tween element amplitudes leads to lower mutual coupling.
A comparison of three tapering methods in antenna beam
broadening is shown in Table II. Pattern error in Table II
is difference between required and achieved patterns.
These two meth-
However as was said
In this paper, design of antenna section of multifunc-
tion phased array radar simulation test bed was illus-
trated. Effect of element pattern, phase quantization,
Comparison between three beam broadening methods.
relative directivity [dB]
rms of beam error
beam ripple [dB]
side lobe level [dB]
amplitude and phase error and elements failure rate on
array pattern was presented. Antenna beam broadening
was illustrated and compared with three different taper-
ing methods. It was shown that phase only tapering is
appropriate for MFAR transmit beam broadening. Beam
broadening increases the space coverage and power trans-
mission in the antenna main lobe. These will lead to
better search performance of MFAR. Effect of different
antenna parameters can easily be evaluated by a little
change in multifunction phased array radar simulation
test bed program. In this way, design of the antenna
(e.g. required side lobe level in the electronic warfare
scenarios or SLC performance and angle measurement
accuracy) may be finalized in real scenario simulations.
Future works includes search function performance com-
parison between MFARs with narrow and wide antenna
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