A paper review of Dual Band wide angle scanning palanar array

1. Review :Dual-Band Wide-Angle Scanning Planar
Phased Array in X/Ku-Bands
Shenario Ezhil Valavan, Dinh Tran, Alexander G.
Yarovoy, Senior Member, IEEE, and Antoine G.
Roederer, Life Fellow, IEEE
Submitted By: Muhammad Nauman Danish
Electrical and
Computer Engineering Department
Air Univeristy
E-9 Islamabad
Email:https://naumandanish311@gmail.com
Submitted To : Dr. Saleem Shahid
Electrical and
Computer Engineering Department
Air Univeristy
E-9 Islamabad
Email:https://saleem.shahid@mail.au.edu.pk
Abstract—The rapid development of communication
system increases the dependency on multi-band operations.
The development of dual-band antenna seems inevitable
for integration of multi-band concept in one device and
to reduce the development cost effectively. The mentioned
paper discussed the design, development and experimental
results for novel planar dual band phased array. The array
operates in X and Ku band and have the capability of
wide angle scanning up to 60 and 50 degree at low and
high frequency respectively. Single layer crossed L-bar
micro-strip is designed and developed to exhibit the said
operation properties with flexible resonance capability due
to plate through hole and field matching ring arrangement.
The 7x7 dual band array demonstration exhibits low-
profile architecture (0.33 x 0.33) and satisfactory correla-
tion with full wave simulations. The dual band operation
supports large frequency ratio of 1.8:1 with good sub-band
bandwidths.
I. BACKGROUND OF THE DEVELOPMENT
The proposed invention is related to the design
and development of multi-function radars in terms
of dual-band phased array antennas, low profile
architecture, flexible resonance tuning capabilities
and wide angle scanning feature with reasonable
grating lobes.
A phased array antenna consists of multiple radiat-
ing elements in linear or planar arrangement with
embedded phase shifter. The desired beam pattern
is formed by shifting the phase of signal provided
to these radiating elements. The constructive and
destructive interference for travelling waves steers
the beam in desired direction. The direction of the
main beam is determined by the direction of increas-
ing phase shift and it can be electronically adjusted
if electronic phase shifters are used. However the
extension of scanning beam width is limited to 120
degree (60 degree left and 60 degree right). The
increase in operating bands (broadband) of radiating
elements is limited because of grating lobes which
are referred to secondary maxima that are generated
with the main beam of phased array. The grating
lobes directly affect the performance of phased array
as they divide the transmitted and received power
in false and main beam of the antenna. The said
property of grating lobes generates the ambiguity
in directional information received from main beam.
So in reality the efficiency of broadband radiation
elements is directly related to size of single element
which in turn yields lager phased array that is
too large for many applications. Moreover the said
reason is also dictated by the wide spacing between
the elements within a phase array that results in
generation of grating lobes at the high end of
bandwidth.

2. The suggestions and investigation for multi-band
antennas for modern wireless and radar applications
is one of trending area for last couple of years. The
research on multifunction radars with reconfigurable
features seems to yield the next generation radar
systems. Antenna phased array is one of the main
pillars for the anticipated system. In the history,
a number of ultra-wide band antenna arrays have
been proposed to fulfill the mentioned requirements.
However in order to be more resistant to electro-
magnetic interference multiband antenna arrays with
well separated operational sub bands provide more
fruitful results. The capability of these array anten-
nas to operate in two or more band enables these
radar systems to perform multi-operational tasks in
different bands using the same aperture. Antennas
using reflector technology such as parabolic reflec-
tors are difficult to implement in multi- bands oper-
ations and their limitation with respect to scanning
rates due to slow mechanical beam steering makes
difficult to track low earth orbit communication
satellites. Lens antennas are difficult to implement
in multi-band technology as they require different
focal points for different bands. Previously the
said idea was implemented using passive interlaced
arrays with features of multi-band operations and
wide angle scanning capabilities. These arrays are
formulated by assembling or interlacing two antenna
arrays operating on different band to reduce the
overall size. However the interlaced array shows
their limitations in implementation of three or four
band operations.
It has been observed, that dual or multiband anten-
nas array performance is limited due to four major
constraints which in combination proved to be the
restraining elements for the successful developments
of dual or multiband arrays i.e. insufficient fre-
quency ratios for the operational bands, large electri-
cal dimensions, irregular and unpredictable radiation
patterns and improper wide angle impedance match-
ing. Usually the design concepts for the mentioned
arrays include the switching frequency capability,
integration of multi-band ability with tunable filter
and array architectures. Concluding the mentioned
discussion, it is desirable to construct a low profile
phase array antenna with wide angle scanning capa-
bility along with the multi-band operations without
undesirable grating lobes.
II. SUMMARY OF THE DEVELOPMENT
A dual band X/Ku wide angle scanning planar
phased array design and development procedure has
been disclosed. The array capable novel crossed L-
bar antenna with single layer geometry has been
developed. The array shows dual band impedance
matching characteristics having low-profile feature
with electrical dimensions of (0.33 x 0.33) at low
frequency band of operation. 49 radiating elements
arranged in a planar format as 7x7 matrix are
optimized to produce frequency ratio of 1.8:1 in
both X and Ku band with center frequency at 9.8
GHz and 17 GHz respectively resulting in wide
angle scanning of 60 and 50 degree for low and high
frequency band respectively. The characteristics of
developed microstrip antenna corresponds to low
profile array capable electrical dimensions, large
frequency ratios, consistent radiation patterns and
wide angle scanning capability.
The concept of off-centered feed for rectangular
strip of radiating element along with square unit
cell arrangement along E and H plane concept has
been used to design and develop the required planar
array. The mentioned arrangement results in two
operational modes for antenna yielding dual band
operation and similar levels of scanning along the
principal planes respectively. However dual mode
operation requires larger patch length ultimately
increasing the electrical dimensions especially for
higher frequency bands. To avoid mentioned prob-
lem the strip like patch is modified into crossed
L-bar arrangements which is analogous to use of
meander line printed antenna geometries. This ul-
timately reduces the electrical dimensions of an-
tenna by increasing the electrical size for radiating
aperture providing resonance at frequencies lower
than the ones obtained using single L-bar geometry.
The single radiating cell geometry consists of SMA
connector with plate through hole (PTH) cylinder,
field matching ring (FMR) and a dielectric substrate
layer. The diameter of SMA feed pin dictates the
inner diameter of both PTH and FMR. The polarized
waves along the diagonal plane of the radiator
are achieved using L-bars alongside with cavity
that result in orthogonal polarization of E and H
plane at = 135 and = 45 respectively. The said
cavity architecture also reduces the mutual coupling

3. between the radiating elements.
The dual band characteristics of antenna array gen-
erate two different surface current distributions. In
low frequency mode the radiation spots occur at
stem of L-bars and in high frequency mode the
distribution is concentrated along the base of L-bars
elements. In order to optimize the performance pa-
rameters of antenna array the ratio of length (l1/l2)
and ratio of width (w1/w2) for each L-bar radiating
element is used with additional tuning parameter
known as matching rings outer diameter with value
of 1.9mm. The resonant bands position is controlled
by varying width ratios and impedance matching
has been achieved by tuning length ratios. However
varying the said parameters does not affect the
orthogonal polarization property of antenna array
due to maintaining of symmetric structure along the
diagonal plane resulting in unaffected polarization
of radiating waves. The discussed concept of design
and development for the antenna structure can also
be extended to circular antennas easily with appli-
cation to stand alone crossed L-bar antenna only.
III. TECHNICAL ANALYSIS OF THE
DEVELOPMENT
The evaluation and optimization of designed an-
tenna is carried out CST- Microwave Studio (CST-
MWS) using model for infinite array. At length
of 10.4mm x 10.4mm resonance is achieved for
both X and Ku bands (8-18 GHz) with evaluation
of variations in dual band, sub band bandwidth
and scanning angle parameter. The reduced mutual
coupling due to cavity architecture of the antenna
also helps in maintaining 60 along both planes. The
scan blindness effects are nullified by maintaining
bandwidth for dual bands up to 60 along principal
planes.
The low profile and wide angle impedance matching
proves useful in many array applications. In order
to achieve the low-profile electrical dimensions,
the dimension of antenna cell is further reduced
to 10 x 10 mm which improves the wide-angle
scanning at high frequency band. The above said
change in dimensions of antenna cells are obtained
by marginally tuning length and width ratios with
fixed diameter 1.9mmm and standard thickness for
substrate. The radiation unit shows 0.33l x 0.33l
and 0.58h x 0.58h dimensions for low and high
frequency resulting in grating-lobe free scanning up
to 60 and 50 respectively by using relation explained
in experimental analysis section. The analysis of
reflection coefficient of center element (25) depicts
that frequency ratio 1.8:1 is achieved with 310 MHz
and 1.2 GHz bandwidth for low and high frequency
respectively. The consistent radiation pattern of -15
dB is achieved at both ends.
The metal cavity is introduced in order to confine
the field distribution for the unit cell. The results are
obtained for center element (no:25) by terminating
other elements at matched loads. It is observed that
field is successfully contained within the center unit
cell in both operational bands having low coupling
level of -30 dB after the second adjacent element in
low frequency mode. Moreover for the successive
radiating pair (i.e.25 and 26) the maximum coupling
level observed is below -19.1 dB and -21.5 dB for
E and H plane respectively. The observed behavior
is significant for small inter element spacing at low
frequency operations. The above mentioned features
guarantee wide angle grating-lobe free scanning
capability by avoiding scan blindness effects.
IV. EXPERIMENTAL, GRAPHICAL AND
MATHEMATICAL ANALYSIS
A. Experimental Framework
The fabricated array constitutes of 49 elements
in a plane of 7x7 matrix yielding low profile
dimensions of array as length of 70 x 70 mm
with 1.58mm (0.05l) thickness. The mounting of
individual element with ground plane is supported
by conductive adhesive. In order to carry out the
experimental test to obtain radiation patterns the
complete structure is than installed on electronically
rotated pedestal of turn table in DUCAT anechoic
chamber
B. Graphical Description Analysis
The concept of rectangular strip implementation
along with L-bar geometry for vertical and hori-
zontal polarization has been showed in figure 1 for
each unit cell. Figure 2 deals with the proposed dual
band cross L-bar antenna geometry depicting the
polarization along with plate-through-hole cylinder

4. and matching ring arrangement. The surface current
distribution at 9.8 GHz and 17 GHz has been
displayed using figure 3 showing radiation spots at
stem and base portion of unit cell for low and high
frequency. The reflection coefficient for different
bore-sight angle has been simulated for infinite
array using CST-MWS software and displayed using
figure 4. The 49 element array has been tested
and its reflection coefficient has been recorded for
center element 25 showing resonance at 9.8 GHz
and 17 Ghz approximately and its radiation pattern
is depicted resulting in consistent radiation pattern
and cross polarization level up to -15dB in figure
5 and figure 6 respectively. Figure 7 depicts the
arrangement of metal cavity used to confine the
field distribution within the unit cell at 9.8 GHz and
17 GHz. The complete fabricated dual-band planar
array prototype with connector assembly has been
displayed in figure 8 and complete experimental
setup along with array under test and reference
ridged horn antenna in Anechoic chamber has been
exhibited in figure 9. Figure 10 compare the com-
puted and measured embedded reflection coefficient
for center element of array no.25 and figure 11
shows the measured embedded radiation pattern of
the center element at 9.9 GHz and 17.1 GHz to
be consistent with cross polarization level below -
16 dB over the entire angular range. Grating-lobe
free beam scanning up to 60 and 50 degree has
been indicated by measuring radiation patterns of
the array at low and high frequency in figure 12. The
scanning performance of the array at high frequency
band of operation along E and H plane has been
disclosed in figure 13.
C. Mathematical Analysis
The dimensions of unit cell for the antenna array
is related to the grating lobe free scanning beam
width by under mentioned relations:
de = λop/1 + sin (θmax) (1)
where de refers to the inter element spacing, op rep-
resents operational wavelength and max corresponds
to the maximum possible grating lobe free scanning
angle
V. PLANAR PHASED ARRAY FEATURES
SUMMARY
The graphical results for the 49 element 7 x 7
matrix planar array depicts following points: The
simple one layer architecture of antenna array de-
sign is a notable advantage as it represents as trong
value addition to the domain of dual band phased
arrays.
The tolerances and constraints related to fabrication
of antenna design such as substrate values, element
dimensions and diameter of cavity has positively
aided in achieving the performance conformance.
The low frequency band exhibits variation in op-
erating frequency between 9.81-10.08 GHz for 270
MHz bandwidth and 16.2-17.4 GHz for 1.2 GHz
bandwidth supporting maximum frequency ration of
1.8:1. The mentioned variation is mainly contributed
because of slight transformations in practical value
of effective permittivity due to use of adhesive
layers in fabrication. Adhesive layers in practical
have greater value of permittivity than implemented
substrate.
The principal plane of E and H plane at = 135 and
= 45 shows consistent radiation patterns with cross
polarization level below than -18db over the entire
angular range.
The grating-lobe free scanning up to 60 and 50 are
achieved at low and high frequency with side lobe
level below than -14 dB respectively due to small
electrical dimensions for these bands. At higher
frequencies directivity increases due to large fre-
quency ratios which in turn result in larger electrical
dimension of planar array. The side lobe level can
be decreased further by using amplitude taper if
required.
The compact structure of electrically low profile
unit cell at high frequency band depicts it novel
characteristics and broad embedded radiation pat-
terns enables the array to exhibit mentioned wide
angle scanning capability for dual bands with large
frequency ratio 1.8:1
VI. CONCLUSION
The author in this paper disclosed the design,
development and experiment results for the dual
band novel array which operates fairly in both X and

5. Ku band. The scanning angle achieved by author
for the said array was 60 and 50 degree at low
and high frequency respectively with frequency ratio
of 1.8:1. The side lobe levels are below 14dB. He
developed 49 elements in 7x7 planar arrangements
with low profile architecture of (0.33 x 0.33). It was
experimentally proved that simulated results are in
well coordination with practical results.

6. VII. DIAGRAMS
Fig. 1. Rectanguar and L- Bar Patch Antenna with offcentered feed.
Fig. 2. Schematic for proposed Dual Band Croosed L-Bar Antenna
Fig. 3. Surface Current Distribution at operational bands i.e. 9.8 GHz
and 17 GHz respectively
Fig. 4. Variation Of Active Reflective Coefficient with Sacnning
Angle

7. Fig. 5. Computed Embedded Reflection Coefficient for Center
Element of 7x7 array
Fig. 6. Computed Embedded Radiation Pattern for Center Element
of 7x7 array
Fig. 7. Computed Field Distriubution for Center Element of 7x7
array at operational bands i.e. 9.8 GHz and 17 GHz respectively

8. Fig. 8. Fabricated Dual Band Planar Array Prototype
Fig. 9. Anechoic chamber measurement setup
Fig. 10. Measured and simulated embedded reflection coefficient of
the center element of the planar (7 x 7) array
Fig. 11. Measured embedded radiation patterns of the center element
(no: 25). (a) 9.9 GHz ( ) and (b) 17.1 GHz ( ).

9. Fig. 12. Scanning performance of the array at low frequency band
of operation (9.9 GHz). (a) E-plane and (b) H-plane
Fig. 13. Scanning performance of the array at low frequency band
of operation (17.1 GHz). (a) E-plane and (b) H-plane