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Chapter 2
Literature Survey of
Reconfigurable Antenna
2.1 Background
The reconfigurable antennas have the advantage of being able to produce good ra-
diation patterns with better bandwidth, compared to patch antennas. In addition
antennas with desired reconfigurability can be produced by using a combination
of strip conductors and slots arranged along the sides of a microstrip feed and
probe feed. The basic element of the spiral slot is presented at first, and the is-
sues evolved from the probe feeding are presented. Based on the concepts already
discussed about the microstrip and probe fed rectangular slot, the probe fed spi-
ral slot and the loaded spiral slots are introduced. In the second section, the
work done by other researchers on multi band and reconfigurable slot antennas
is noted. Finally some information about varactor diodes and pin diodes which
implement the switches for the reconfigurable antenna is provided.
In designing a small antenna there is always a compromise between size, band-
width, and efficiency. Reconfigurable antenna architecture makes very efficient
use of limited area by taking advantage of combined multiple functions in one
single antenna. This result in significant reduction in the area occupied by the
multiple antenna elements with enhanced functionality and performances. The
28
exhaustive literature survey starting from 1983-2013 in brief is presented in this
chapter.
2.2 Literature survey
An antenna is a structure or device used to collect or radiate electromagnetic
(EM) waves. In some sense the first antenna dates from 1887, when Hein-
rich Hertz designed a brilliant set of wireless experiments to test James Clerk
Maxwell’s hypothesis. Hertz used a flat dipole for a transmitting antenna and a
single turn loop for a receiving antenna. For the next fifty years antenna tech-
nology was based on radiating elements configured out of wires and generally
supported by wooden poles. These “wire” antennas were the mainstay of the
radio pioneers, including: Guglielo Marconi, Edwin Howard Armstrong, Lee de-
forests [Lewis, 1991] [40]-[44]. Each of these “engineers” has been called the
Father of the Radio [Lewis, 1991]. Dr. deforest was conducted an experiment on
long-distance wireless broadcasts one hundred years ago from the Illinois Institute
of Technology. The first generation antennas were narrow band and were often
arrayed to increase directivity. Development of the arrayculminated in the work
of Hidetsu Yagi and Shintaro Uda in 1926.
Daniel H. Schaubert et al [45], University of Massachusetts, was a frequency
reconfigurable antenna pioneer who experimented with frequency agile, polar-
ization diverse microstrip antennas and frequency scanned arrays to achieve
frequency-agility without changing the physical dimensions of the antenna el-
ements. A typical thin microstrip antenna will only operate over a frequency
range of two or three percent. These types of antennas that have the capability
of radiating energy over a wide range of frequencies with the frequency changes
being made very rapidly. Since the instantaneous bandwidth of the microstrip
antenna is small, i.e., approximately 2-3 percent, the capability of switching fre-
quencies over a wide range would provide a considerable immunity to interfering
signals.
In 2001, [46]-[47] the first reconfigurable antenna project in China was sup-
29
ported by the high-technology research program.This project, electromagnetic
theory and key techniques of reconfigurable antenna, has been carried out by
researchers in Computational Electromagnetic Laboratory (CEMLAB) at Uni-
versity of Electronic Science and Technology of China (UESTC).
Z. D. Liu et al [48], reported on a new dual-frequency planar inverted-F an-
tenna (PIFA) is developed for GSM 900 and DCS 1800. A U-shaped slot and a
rectangle shaped slot are cut in the antenna radiation patch, which obtains dual
operating frequencies. It has been demonstrated by simulation and measured
that the presented antenna can cover the operating frequencies of GSM 900 and
DCS 1800.
Huff G. H. et.al [49], reported in 1998 on a novel pattern and frequency recon-
figurable microstrip antenna that uses switched connections. The basic antenna
operates with linear polarization around 3.7 GHz. He discussed about two types
of antenna. One set of connections provides a re-directed radiation pattern while
maintaining a common operating impedance bandwidth with the baseline config-
uration. The second set of connections results in operation at a higher frequency
band at 6 GHz with broadside patterns.
Kolsrud A. T. et.al [50], discussed about CPW-fed coplanar strip (CPS) dipole
antenna for dual frequencies.. The CPS dipole antenna was found to have two
distinct operating frequencies of 2.065 GHz and 3.955 GHz, respectively. In
this antenna varactor junction capacitance is varied when the bias voltage was
changed from 0 to -30 V, the tuning range for the lower frequency was measured
to be 14.5% or 300 MHz upwards (from 2.065 GHz to 2.365 GHz), and the higher
operating frequency was tuned 11.5% or 450 MHz downwards (from 3.955 GHz
to 3.505 GHz).
Jung-Chih Chiao et.al [51], demonstrated a new architecture for microelec-
tromechanical system (MEMS) reconfigurable Vee-antennas. This Vee-antenna
designed for 17.5 GHz and predicts an optimal angle of 82.50 will give a maxi-
mum directivity of 5.6. The antenna directivity using 3 dB beamwidths is 37.9.
30
Y.Qian et.al [52], in 1999 reported on reconfigurable aperture where different
types of antennas and arrays with multiband coverage and multiple functions
share a common planar physical aperture. The measured bandwidths (VSWR ¡
2) of the reconfigured and reference antennas are 18% and 16% respectively. The
gains of these two antennas were also measured and were found to be at the same
level of 12 dB at 8.5 GHz.
Shun-Shi Zhong and Jun-Hai Cui [53], reported compact dual frequency mi-
crostrip antenna. This compact and broadband, patches with single slot on its
non radiating edges have been cut to yield a 2:1 VSWR bandwidth in the range
of 10-20%. This antenna operating for two resonant frequencies at 1.04 GHz and
2.49 GHz. Bandwidths determined from the -10 dB rectum loss are 5.77% for 1.04
GHz band and 8.03% for 2.49 GHz band. The ratio of these two frequencies is 2.4.
Hattan F Abutarboush et.al [54], studied and presented a reconfigurable wide-
band and multiband C-Slot patch antenna with dual-patch elements. This an-
tenna operates in two dual-band modes and a wideband mode from 5 to 7.5
GHz, corresponding impedance bandwidth of 4.2% and 2.4% is obtained. In the
ON-ON state, both patch elements are radiating. A wide bandwidth of 33.52%,
covering the frequency range from 4.99 to 7 GHz is obtained.
M. Ali and G. Hayes [55], demonstrated an integrated planar inverted-F an-
tenna (PIFA). This antenna presents input impedance data around 2.45 GHz.
By varying the size of F-slot the antenna resonant resistance is also varies as 31
l2 Ω and 43.7 Ω.
Vinoy K J and Varada V K [56], in 2001 reported on the devices and systems
that use RF microelectromechanical systems (RF MEMS) switching elements
which typically use one switch topology. This technique gives the deferent reso-
nant frequencies for deferent iterations. For first iteration it gives 360, 980, and
1440 MHz, and for next iteration: 270, 720, 1000 and 1370 MHz. This shows a
reduction in the resonant frequency (in this case by 25%) with an increase in the
31
fractal iteration.
Dimitrios Peroulis et.al [57], presented a novel electronically tunable slot an-
tenna. This design is based on a resonant slot structure loaded with a series of
PIN diode switches. These sources of radiation also affected the E-plane pattern
measurements and they caused a difference of 3-4 dB between the minimum and
maximum measured value. The design relies on changing the effective length of
a resonant slot structure by controlling combinations of electronic RF switches
and achieves an effective bandwidth of 1.7: l. The fabricated antenna is capable
of resonating at four different frequencies ranging from 550 to 900 MHz.
Yang F. and Y. Rahmat Samii [58], reported a novel design of a microstrip
patch antenna with switchable slots (PASS) is proposed to achieve circular polar-
ization diversity. By turning the diodes on or off, this antenna can radiate with
either right hand circular polarization (RHCP) or left hand circular polarization
(LHCP) using the same feeding probe. By using this, best axial ratio at boresight
is achieved at 4.64 GHz with 3% CP bandwidth An acceptable axial ratio (AR¡3
dB) is obtained in a broad angular range from -70 to 70 degrees from boresight
direction.
F. Yang and Yahya Rahmat-Samii [59], described reconfigurable antennas are
becoming popular in antenna engineering because of their capability in frequency
agility, bandwidth enhancement, and polarization diversity. The best axial ratio
at boresight is achieved at 4.64 GHz with 3% CP bandwidth for both RHCP and
LHCP patterns compared to normal designs, when the switch is ON, a 2.9 dB
axial ratio is achieved at 4.0 GHz. When the switch is OFF, a 1.6 dB axial ratio
is obtained at 4.37 GHz.
C. Y. Huang et.al [60], have discussed a technique for obtaining a single-
layer single-feed dual-band microstrip antenna loaded with narrow slots and chip
capacitors. The range of the frequency ratio (FR) is extended to 1.25 by using
chip capacitor loading across the narrow slots to produce further capacitive loads.
32
Matthias K. Fries [61], presented reconfigurable slot antenna architecture al-
lowing polarization switching. This designed antenna shape consists of a slot-ring
with perturbations which are switched on and off using pin-diodes. It shows the
axial ratio bandwidth (ARB) of 4.2% and the minimum axial ratio is 0.9 dB.
Also the antenna gives ARB’s of 4.3% and 3.4% for the LHCP and the RHCP,
respectively.
J. T. Bernhard et.al [62], presented reconfigurable portable antenna systems
for high-speed wireless communication (2-100 Mb/sec). Wireless data communi-
cation whether it is for land or satellite based-faces two challenges: (1) high error
rates caused by interference and unpredictable environments, and (2) limited sig-
nal processing capability and battery life at the portable unit. ‘Intelligent’ or
’smart’ antenna systems can help meet these challenges. Current ’smart’ systems
reside mainly at base stations and rely largely on signal processing to achieve their
goals. Second, the bandwidth of the antenna (currently at around 1%) needs to
be increased to at least 3.5% for it to be broadly useful in 802.11 networks.
N. T. Herscovici and C. Christodoulou [63], analyzed and demonstrated new
technologies in communications electronics, such as software-defined radio (SDR)
and RF switches implemented using micro-electromechanical systems (MEMS).
The antenna is designed which ability to realize electrically small antennas is
for both efficient and broadband. As a result covering several frequency bands
concurrently with a single antenna having enough efficiency and bandwidth is a
major challenge. One possible solution to this problem is to use reconfigurable
antennas that tune to different frequency bands. Such an antenna would not
cover all bands simultaneously, but provides narrower instantaneous bandwidths
that are dynamically selectable at higher efficiency than conventional antennas.
J. Costantine et.al [64], presented a new reconfigurable multiband microstrip
antenna. The patch has the shape of six armed star printed on a hexagonal sub-
strate. When the different switches are activated multi frequencies are generated
around 3 GHz and 4.5 GHz. The antenna also presented wide band operation,
from 3.5 GHz to 3.8 GHz and from 4.3 GHz to 4.7 GHz.
33
James T. Aberle et al [65], proposed and demonstrated reconfigurable anten-
nas for wireless communication. In his work, pin diodes and shorting patches are
used for achieving the high Qs factor of 150 and obtain a 12 MHz to 15 MHz
antenna bandwidth, which could cover each of GSM bands in three to four steps
with radiation efficiencies of 20% to 30%.
Lon N. Pringle et.al [66], have described a reconfigurable aperture (RECAP)
antenna in which a planar array of electrically small, metallic patches are inter-
connected by switches. The antenna can be reconfigured to meet different per-
formance goals by changing the switches that are open and closed. This switch
configuration gives deferent frequency ranges of 0.85 GHz - 1.25 GHz, a band-
width of 38 % and for frequency range is 1.10 GHz-1.45 GHz bandwidth of 27%.
Shynu S. V. et.al [67], reported a compact electronically reconfigurable dual
frequency microstrip antenna for L-band applications. The frequency ratio of the
antenna varies in the wide range of 1.2 to 1.4 with a good bandwidth of 2.82%
and 2.42% for the two resonant modes. This antenna has achieved size reduction
of 72.21% and 46.81%for the two resonating frequencies.
B.A.Cetiner et.al [68], demonstrated multi functional reconfigurable MEMS
integrated antenna for multi-input multi-output systems. This antenna provides
ten different reconfigurable modes of operation corresponding to the combina-
tion of two operating frequencies of 4.1 GHz and 6.5 GHz and five reconfigurable
polarizations of the radiated field of linear X, linear Y , dual linear, right hand
circular, and left hand circular. Frequency reconfigurability is also achieved by
simply changing the size of the antenna and it operates with dual frequency
bands. The upper frequency is 6.4 GHz and lower frequency is 4.1 GHz obtained
by using MEMS.
Joshua S. Petko and Douglas H. Werner [69], introduced a design method-
ology for miniature multiband as well as reconfigurable (i.e., tunable) antennas
that exploits the self-similar branching structure of three-dimensional (3-D) frac-
tal trees. The resulting antenna can be reconfigurable from 770 to 1570 MHz with
34
a bandwidth of 800 MHz with a VSWR under 3:1.The another fractal shape is
reconfigurable from 970 to 1570 MHz for a bandwidth of 560 MHz with a VSWR
below 2:1 is obtained.
B.A. Cetiner et.al [70], presented a reconfigurable spiral antenna for use in
adaptive MIMO systems. By using RF-MEMS actuators in the antenna average
half power beam width (HPBW) is approximately 105 is obtained. The antenna
radiates almost entirely circularly polarized wave with axial ratio value of 0.9
dB. The gain of the antenna is 5.3 dB. The circular polarization bandwidth over
which the axial ratio is less than 3 dB is approximately 11%. Gain of the antenna
with average value of 4.9 dB shows small variation over this bandwidth.
D. Peroulis et.al [71], have designed and presented a compact, efficient and
electronically tunable antenna. A single-fed resonant slot loaded with a series of
PIN diode switches constitutes the fundamental structure of the antenna. Four
PIN switches are used in order to tune the antenna over a range of 540 - 950
MHz and calculated return loss where a matching level of better than has been
achieved is 20 dB for all the operating frequencies. The measured gain is -1.1
dBi, which corresponds to an antenna efficiency of 47%.
Shynu S.V et.al [72], presented a novel reconfigurable, single feed, dual fre-
quency, dual polarized operation of a hexagonal slot-loaded square microstrip
antenna. A pin diode incorporated in the slot. When the diode is switched OFF,
the antenna resonates at 1.48 GHz and 1.99 GHz with a frequency ratio of 1.34
and antenna provides a size reduction of 61% and 26% for the two resonating fre-
quencies. This design also gives considerable bandwidth up to 3.3% and 4.27%,
for the two frequencies with a low operating frequency ratio. Once the diode is
turned ON, the first resonant frequency shifts to 105 MHz and second resonant
frequency to 60 MHz, thus giving excitation at 1.585 GHz and 2.05 GHz respec-
tively.
Shynu S.V. et.al [73], reported in 2005, a novel design of a varactor controlled
electronically reconfigurable dual frequency microstrip antenna. Varactor diodes
35
integrated with the slot arms are used to tune the operating frequencies consid-
erably, by applying reverse bias voltage. Tuning ranges of 21% and 12.9% are
realized for the two resonant frequencies respectively, when the bias voltage is
varied from 0 to -30 V. This design has an added advantage of size reduction
up to 80% and 70.18% for the two resonant frequencies compared to standard
rectangular patch. A maximum bandwidth of 6.2176% and 10.4255% for the
two frequencies with an operating frequency ratio varying in the range 1.0645 to
1.2180 is observed.
M. A. Saed [74], investigated a novel reconfigurable two-layer microstrip an-
tenna fed using a coplanar waveguide through a slot/loop combination. The
slot/loop combination allows for easy reconfigurability of the frequency band of
operation by incorporating switches in the feed network. By this impedance
bandwidths of about 23% were obtained for two selectable frequency bands using
two switches. The two frequency bands 8.73 GHz - 10.95 GHz and 7.68-9.73 GHz
are obtained.
Sunan Liu et.al [75], have demonstrated a microstrip antenna with integrated
RF mircoelectromechanical system (MEMS) switches to operate at dual frequen-
cies with circular polarization. The switches are incorporated into the diagonally-
fed square patch for controlling the operating frequency and a rectangular stub
attached to the edge of the patch acts as the perturbation to produce the cir-
cular polarization at 6.69 GHz and 7.06 GHz giving rise to frequency ratio of 1.05.
Zhang Y et.al [76], presented a novel fractal microstrip patch antenna, which
has the feature of linearly polarized reconfigurable radiation patterns. By con-
trolling RF MEMS switches on/off, two sets of connection states can be obtained
at 10 GHz and the return losses are less than -20 dB and radiation patterns can
be reconfigured in the upper half-space is also observed.
Kyungho Chung et.al [77], presented a novel reconfigurable microstrip patch
antenna with frequency and polarization diversities. A U-slot is incorporated into
a square patch and a PIN diode is utilized to switch the slot on and off, which
36
obtained the frequency diversity characteristic. By using PIN diodes on U-slot
the obtained 3 dB CP bandwidths are about 35 MHz and 40 MHz.
Carla Mederia and Carlos Fernandes [78], presented an evaluation of frequency
reconfigurable patch antennas for multi-standard personal communication sys-
tems, using PIN diodes as switches This antenna resonates at f1 = 1.89 GHz and
f2 = 2.37 GHz, with an impedance bandwidth of 0.48% and 2.45% respectively.
The experimental results shift 0.89% towards lower values for the first operating
frequency and 2.39% for the second one, when compared to the simulated oper-
ating frequencies, f1 = 1.93 GHz and f2 = 2.43 GHz; is observed.
In 2006 S. V. Shynu et.al [79], reported a design of compact, single feed, dual
frequency dual polarized and electronically reconfigurable microstrip antenna. A
square patch loaded with a hexagonal slot having extended slot arms constitutes
the fundamental structure of the antenna. The tuning of the two resonant fre-
quencies is realized by varying the effective electrical length of the slot arms by
embedding varactor diodes across the slots. A high tuning range of 34.43% (1.037
GHz - 1.394 GHz) and 9.27% (1.359 GHz - 1.485 GHz) is achieved for the two
operating frequencies respectively, when the bias voltage is varied from 0 to - 30
V. The antenna has size reduction up to 80.11% and 65.69% for the two operating
frequencies are achieved.
S. Nikolaou et.al [80], demonstrated an antenna use of pin diodes to recon-
figure the impedance match and modify the radiation pattern of an annular slot
antenna (ASA). Matching stubs are used to match the antenna to three different
frequencies, 5.2, 5.8 and 6.4 GHz. PIN diodes are used to connect or disconnect
the stubs creating a reconfigurable matching network.
N. Behdad and K. Sarabandi [81], introduced a new technique for designing
dual-band reconfigurable slot antennas. This technique is based on loading a slot
antenna with a lumped capacitor (or varactor) at a certain location along the
slot. Based on this technique, an electronically tunable dual-band antenna with
a frequency ratio in the range of 1.2 - 1.65 is designed and tested using a single
37
varactor with a capacitance range of 0.5 - 2.2 pF. Frequency of the first resonance
is increased from 1.8 GHz to 1.95 GHz and the second band increases from 2.15
GHz to 3.22 GHz. The antenna has similar radiation patterns with low cross-
polarization levels at both bands and across the entire tunable frequency range.
Lower efficiency of 70% and 85% for the first and second bands are calculated.
Cesar Lugo and John Papapolymerou [82], demonstrated a six-state reconfig-
urable band-pass filter intended to add frequency tunability to antenna systems.
The present topology produces filter responses with center frequencies of f0 =
9, 10, and 11 GHz and achieves independent bandwidth control with an average
tunable passband ratio of 1.73:1 between the wideband configurations ranging
from 13.4% and 14.7% and the narrowband configurations ranging from 7.7%
and 8.5%. PIN diodes are implemented as switching elements and the distinct
states are discretely accomplished by the connection and isolation of strategically
placed transmission line sections. The insertion loss of the filter ranges between
1.74 and 1.92 dB. The measured gain is greater than 48 dBm for tones separated
by 1 MHz around the center frequencies.
Nader Behdad and Kamal Sarabandi [83], presented a new technique for
designing dual-band reconfigurable slot antennas. Dual-frequency operation is
achieved by loading a slot antenna with two lumped variable capacitors (varac-
tors) placed in proper locations along the slot. The antenna efficiency values are
calculated from the measured gain and calculated directivity values at broadside.
When V1 = 0 V and V2 = 1 V for and the directivity of the antenna at the first
band 1.3 GHz and second band is 2.67 GHz are, 1.76 and 1.96 dBi respectively
which corresponds to an efficiency of 58% and 59% for the first and second bands,
respectively. As the bias voltages increase, so do these efficiency values. When
V1 = V2 = 30 V, the directivity of the antenna at the first and second bands are
1.82 and 2.16 dBi, respectively. This corresponds to efficiency values of 87% and
92% at the first and second bands respectively.
Dimitrios E. Anagnostou and Guizhen Zheng [84], reported reconfigurability
in an antenna system is a desired characteristic that has been the focus of much re-
38
search in recent years. In his work, ohmic contact cantilever RF-MEMS switches
are integrated with self-similar planar antennas to provide a reconfigurable an-
tenna system that radiates similar patterns over a wide range of frequencies. In
this antenna when the probes are placed away from the pads, a resonance at 16.5
GHz (with a 14.2 GHz - 17.5 GHz bandwidth) is measured. The weak resonance
at 21 GHz can also be noticed. Next, when the dc probes come down and touch
the biasing pads, but no voltage is applied on them, the antenna resonates at 15
GHz, with a bandwidth from 12.75 GHz up to 17.5 GHz and covers the desired
band at 14 GHz.
Greg H. Huff and Jennifer T. Bernhard [85], described about the integration of
commercially available packaged radio frequency microelectromechanical system
(RF MEMS) switches with radiation pattern reconfigurable microstrip antennas.
The overall shared 2:1 VSWR (impedance) bandwidth is 80.0 MHz The (VSWR)
shows that the center frequency of the shared broadside and endfire impedance
bandwidths is shifted down by 400 MHz from fc = 6.88 GHz.
Malcolm Ng Mou Kehn et.al [86], presented a compact reconfigurable multi-
band microstrip antenna. The multiplicity of bands is achieved by the use of
concentric external metallic semirings around a central internal semicircular mi-
crostrip patch antenna. A 56% effective bandwidth and demonstrated that the
operating frequencies can be increased up to 75%.
Hakim Aissat et.al [87], reported the design of a compact microstrip patch
antenna with polarization reconfigurable features (right-handed circular polariza-
tion (CP)/left-handed CP). The basic antenna is a circular coplanar-waveguide
CPW-fed microstrip antenna excited by a diagonal slot and the CPW open end.
The reconfigurable antenna is used as a transmitter antenna and fed by a power
generator, of which output power level ranges from 16 to 26 dBm. The gain is
6.02 dB increased with low power level 16 dBm as well as axial ratio is 2.06.
Zhen Zhou and Kathleen.Melde [88], demonstrated the frequency agility that
can be achieved when a broadband antenna is integrated with a reconfigurable
39
RF tuner as a impedance matching circuit. The reconfigurable tuner uses a
microstrip loaded line structure with four stubs that are each terminated by a
varactor diode. In this case, the frequency sub bands are 0.88 GHz to 0.98 GHz
and 1.24 GHz to 1.34 GHz. Two of the diodes were allowed to have capacitances
that are slightly higher than 5 pF. The antenna results for 0.9 GHz and 1.3 GHz
nearly 10% of the incident power is reflected due to mismatch.
Mohammod Ali et.al [89], presented a reconfigurable stacked microstrip patch
antenna. The antenna operates at an upper frequency fu with a broadside pat-
tern, 7.5 dBi right-hand circularly polarized gain and achieved 15.8% bandwidth.
At a lower frequency fl, the antenna operates as a planar inverted-F antenna
(7.3% bandwidth and 3.9 dBi peak gain) with the main beam directed close to
the horizon.
Mathieu Riel and Jean-Jacques Laurin [90], presented a C-band electronically
beam scanning reflectarray antenna. The reconfigurable reflectarray element con-
sists of a microstrip patch, printed on a flexible membrane substrate, aperture-
coupled to a transmission line loaded with two varactor diodes. The designed
element allows continuous tuning of the reflected signal’s phase over a 360 range
with a maximum loss of 2.4 dB at 5.4 GHz.
Nickolas Kingsle et.al [91], reported devices and systems that use RF mi-
croelectromecha nical systems (RF-MEMS) switching elements typically use one
switch topology. In this paper, three sets of RF MEMS switches with differ-
ent actuation voltages are used to sequentially activate and deactivate parts of
a multiband Sierpinski fractal antenna. This reconfigurable antenna operates at
several different frequencies between 2.4 and 18 GHz and it gives 0% error for
these operating frequencies.
Seung-Bok Byun et.al [92], presented a reconfigurable ground slotted patch
antenna using a PIN diode connection in slots to achieve dual-frequency opera-
tion. Slots on the ground plane increase the electrical length and thereby reduce
antenna size by 53%. With the diodes in the off-state, near 1.85 GHz for K-PCS,
40
the measured bandwidth of -10 dB return loss is approximately 60 MHz. Mea-
sured gains of 2 and -3 dBi were achieved.
B. Z. Wang et.al [93], designed and reported on reconfigurable patch antenna
with a wide operational bandwidth for wireless communication and radar systems.
The reconfigurable patch possesses an E-shaped structure and its operation fre-
quency can be changed by integrated switches. The operational frequency of the
antenna can cover an octave frequency range by utilizing only two switch states.
In state 1, the antenna operates from 9.2 GHz to 15.0 GHz and in state 2, from
7.5 GHz to 10.7 GHz. Relative bandwidths of 48% and 35% are obtained in the
two states respectively.
In 2007, Yildirim B et.al [94], designed and tested reconfigurable penta-band
(GSM900, GPS 1575, GSM1800, PCS 1900, UMTS2100) planar inverted-F an-
tenna (PIFA) having microelectromechanical switches (MEMS). A number of RF
MEMS actuators within the geometrical structure of the antenna are constructed
as part of the design. In this design, PIFA operates for both lower and higher
bands. In low-band, the antenna is matched -6 dB from 748 MHz - 912 MHz.
This represents a fractional bandwidth of 19.9%. Another identical antenna with
MEMS having slightly different capacitance values achieved 765 MHz - 950 MHz
(fractionally, 22%) without any matching, showing that a wide bandwidth reso-
nance is obtained. The higher bands with matching -6 dB bandwidths are 1840-
2151 MHz, 1849 MHz - 2156 MHz and 1901 MHz - 2185 MHz for the UTRA
bands III, II and I respectively (fractionally, approximately 15%) are obtained.
W.B.Wei et.al [95], proposed and presented a novel reconfigurable microstrip
antenna with switchable polarization technique. Using PIN diodes independently
biased on the patch, it can produce linear polarization, left- or right-hand circular
polarization according to bias voltages. Two antennas are having same geometry;
their return losses are extremely uniform. Both resonant frequencies of them are
1.5175 GHz. The measured gains are 5.12 dB and 5.26 dB respectively.
Angus C. K et.al [96], proposed a new design for compact reconfigurable an-
41
tennas are introduced for mobile communication devices. The uniqueness of the
antenna designs are that they allow various groups of their operating frequency
bands to be selected electronically. From this, it clears that both modes to-
gether can cover GSM850, GSM900, DCS, PCS, and UMTS bands with 50% or
greater efficiency. When the active switches are implemented in the design the
first mode excites one lower frequency around 900 MHz and the high-frequency
band at around 1.8 GHz. The second mode excites two resonating frequencies
that are around 900 MHz and 2 GHz.
Giuseppe Ruvio et.al [97], reported a novel technique to reconfigure the fre-
quency range of a planar monopole antenna. The proposed antenna is capable
of covering the frequencies in the range from 2.9 to 15 GHz, depending on the
degree of spiral tightness. The behavior of the gain and the total efficiency is for
the four configurations investigated and at three frequencies: 3, 5 and 7 GHz.
The maximum gain was found to be between 7.5 and 8.5 dBi in the broadside
direction for between 10.0 and 11.0 mm. The patterns are broad beamwidth.
The antenna yields a high-efficiency across the full operating bandwidth.
Alireza Pourghorban et.al [98], presented a novel reconfigurable slot antenna
with three switchable frequencies. The uniqueness of this design is that it al-
lows various groups of its frequency resonances to be selected electronically using
three switches. The antenna resonance frequencies are maximized at the third
resonance, where it is 140 MHz (2.4% shift). Finally, the measured resonances of
the antenna that can support the mentioned frequency bands are 2.46, 3.59 and
5.69 GHz. The measured maximum gain values of the antenna in boresight at
2.46, 3.59 and 5.69 GHz are 2.33, 3.14 and 2.89 dBi respectively.
D. Piazza et.al [99], presented an evaluation of frequency reconfigurable patch
antennas for multi-standard personal communication systems using PIN diodes
as switches. Two different configurations are studied with dual-band behavior: a
patch antenna with two switchable slots and a rectangular patch with a switch-
able parasitic element. On average, the novel antenna solution achieved a 10%
improvement in capacity (with a peak of 28%) for a SNR of 10 dB and 8% (with
42
a peak of 16%) for a SNR of 20 dB with respect to a system with a fixed antenna
configuration.
Shing-Lung Steven Yang et.al [100], presented a frequency reconfigurable mi-
crostrip patch antenna. It is found that by incorporation of a U-slot in the patch
can provide a flat input resistance and a linear input reactance across a wider
bandwidth than the conventional patch antenna. By placing a variable capacitor
and an inductor at the antenna input, the impedance matching frequency of the
antenna is varied. The fabricated prototype antenna attains a tunable frequency
range from 2.6 to 3.35 GHz. It is observed that the antenna attains a tunable
range from 2.6 to 3.35 GHz (return loss is less than -10 dB) in the full-scale range
of the trimmer.
Joshua D. Boerman and Jennifer T. Bernhard [101], reported the poten-
tial benefits of using pattern reconfigurable antennas in multiple-input multiple-
output (MIMO) communication systems. In his calculations for the three antenna
configurations, demonstrates that large capacity improvements are possible. At
the points average received SNR = 10, 20 and 30 dB, the percent improvements
of the capacities of the RDDR mode with respect to the DDDD mode are 70%,
40% and 26% respectively, which reports average gains of 10% at SNR = 10 dB
and 8% at SNR = 20 dB, and peak gains of about 28% at SNR = 10 dB and 15%
at SN R= 20 dB using a variable-length dipole reconfigurable array.
Andrew R.Weily et.al [102], proposed a high-gain partially reflective surface
(PRS) antenna with a reconfigurable operating frequency. The operating fre-
quency is electronically tuned by incorporating an array of phase agile reflection
cells on a thin substrate above the ground plane of the resonator antenna, where
the reflection phase of each cell is controlled by the bias voltage applied to a pair
of varactor diodes. The antenna’s operating frequency is defined by the peak
directivity. As increasing the bias voltage from 6.49 to 18.5 V, the operating
frequency increases from 5.2 to 5.95 GHz. The tuning range of the reconfigurable
PRS antenna is 13.5%. When tuned to 5.2 GHz the antenna covers the 5.15-5.25
GHz WLAN band and when tuned to 5.775 GHz the antenna covers the 5.725-
43
5.825 GHz WLAN band Measured gain of the reconfigurable antenna varied from
10 to 16.4 dBi over the tuning range of 5.2 to 5.95 GHz as the bias voltage was
tuned from 6.49 to 18.5 V.
Zhengyi Li et.al [103], studied and reported the properties of reconfigurable
antenna arrays which increase the flexibility of adaptive multiple-input-multiple-
output (MIMO) systems by their reconfigurable configurations and radiation or
polarization. In this work, a compact reconfigurable antenna array operating in
the UMTS band is proposed. The antenna array consists of two hybrid-monopole
and dipole elements.
D. E. Anagnostou and A. Gheethan [104], presented the design of a reconfig-
urable single folded slot antenna. The design of a single folded slot is reconfigured
and resonance frequency is used for WLAN applications. The measured resonant
frequency for the OFF state is 5.14 GHz and the simulated is 5.25 GHz (a 2.1%
shift). The measured resonant frequency for the ON state is 5.75 GHz, which
is very close to the simulated 5.775 GHz resonant frequency (0.43% shift). The
measured maximum gain is approximately 5.2 dBi at 5.25 GHz and 5.6 dBi at
5.775 GHz are observed.
Shing-Hau Chen et.al [105], designed and presented a single-feed reconfig-
urable square-ring patch antenna with pattern diversity. The antenna radiation
patterns of the reconfigurable patch antenna at 2020 MHz are measured which
correspond to the cases of switching ON and OFF the diodes, whose maximum
antenna peak gain including the ohmic loss of the pin diodes is about 2.5 dBi. It
is also observed that the main beam has good broadside radiation patterns with
a peak gain of 6.8 dBi are obtained. Also, the antenna efficiencies are estimated
to be about 60% and 75% when the antenna is operated at the monopolar plate-
patch and theTM11 modes.
Elyas Palanteil et.al [106], presented a patch with folded dipole antenna ele-
ments was found to be an effective reconfigurable antenna. This antenna allows
for three bands operation such as 5 GHz, 10 GHz and 15 GHz as required for
44
WiMax applications. The antenna must be supported by an RF control unit as
an integrated part of the transceiver circuitry to maintain the appropriate direc-
tion and frequency of operation.
Daniele Piazza et.al [107], reported a MIMO system equipped with MEMS
reconfigurable circular patch antennas that allows selecting the antenna config-
uration at the receiver without the need for estimating the wireless channel for
each configuration of the reconfigurable multi element antenna. By using the
MEMS, a gain of 1.8 dB is achieved for a BER of 0.1%.
Julien Sarrazin et.al [108], presented a new single-feed reconfigurable antenna
for pattern diversity. The proposed structure is based on a metallic cubic cavity
which radiates through rectangular slots. The antenna impedance matching is
achieved around 5.2 GHz in the three cases. The -10 dB frequency bandwidths
are from 5.4% for the antenna configuration 2 upto 8.8% for the configuration 1.
By considering the three configurations, a -10 dB shared bandwidth of 285 MHz
is available between 5.025 and 5.31 GHz is observed.
Nazia Hasan et.al [109], designed a dual band reconfigurable antenna with
embeded of RF-MEMS to achieve dual band operation. The switching between
the different frequency bands is achieved by using RF-MEMS switches. The an-
tenna gives frequency of 2.2 GHz and 3.6 GHz.
Bedri A. Cetiner et.al [110], developed a double and single-arm cantilever type
DC-contact RF MEMS actuators has been monolithically integrated with an an-
tenna architecture to develop a frequency reconfigurable antenna. By activat-
ing/deactivating the RF MEMS actuators, which are located within the antenna
geometry and microstrip feed line, the operating frequency band is changed. The
two reconfigurable modes of operation fh = 5.2 GHz and f1 = 2.4 GHz are ob-
served. The VSWR ( =-10 dB reflection coefficient), the corresponding frequency
bandwidths are 100 MHz and 650 MHz for 2.4 GHz and 5.2 GHz respectively cov-
ering the ISM allocated frequency range.
45
Julien Perruisseau Carrier et.al [111], presented a antenna exhibiting a very
wide bandwidth with reconfigurable rejection within the band. The proposed
topology is versatile in terms of the number of available antenna states and lo-
cation of the rejection frequencies and also allows the operation of the antenna
in an ”all-pass” state. The reliable measurement between 2.0 GHz and about
4.25 GHz consists in the slightly lower measured overall efficiency, which however
remains between 50% and 70%. The measured transmitted IP3 levels at 1.8 GHz
and 4.0 GHz are 35.6 dBm and 40 dBm respectively.
Sean Victor Hum and Hui Yuan Xiong [112], reported the design of a fre-
quency agile microstrip patch antenna that is readily interfaced with differential
RF transceivers. By integrating three pairs of varactor diodes with the patch
antenna and tuning them in unison frequency tuning ratios approaching 2 are
possible with the design. Considering tuning capacitances in the 0.1 - 2.0 pF
range a tuning range between 1.859 GHz and 3.672 GHz corresponding to a fre-
quency ratio of 2 can be easily achieved while maintaining a reflection coefficient
magnitude below -10 dB. The upper frequency limit of the tuning is 3.15 GHz
corresponding to an overall tuning factor of 1.75.
Pei-Yuan Qin et.al [113], in 2010 presented a compact U-slot microstrip patch
antenna with reconfigurable polarization is proposed for wireless local area net-
work (WLAN) applications. PIN diodes are appropriately positioned to change
the length of the U-slot arms, which alters the antenna’s polarization state. It is
observed that axial ratio for the CP mode of antenna for the LP and CP modes
are 6.1% and 13.5% respectively, with almost the same center frequency of 5.9
GHz, which can cover the entire 5.725 GHz - 5.85 GHz WLAN band. The mea-
sured 3 dB axial ratio bandwidth at boresight extends from 5.7 GHz - 5.86 GHz.
The antenna uses two PIN diodes to switch between the two circular polarization
and achieved the 3 dB axial ratio bandwidth is greater than 2.8%.
H. Li et.al [114], reported on simple and compact slot antenna with a very
wide tuning range. To achieve the tunability, only two lumped elements, namely,
a PIN diode and a varactor diode are used in the structure. A compact slot
46
antenna that can be continuously tuned over a very wide frequency band. With
only two lumped elements (a PIN diode and a varactor diode), a wide tuning
range from 0.42 GHz to 1.48 GHz (with the frequency ratio of 3.52:1) has been
achieved and the measured gain is above -0.4 dB.
L.Jong-Hyuk et.al [115], presented a reconfigurable planar inverted-F antenna
using a switchable PIN-diode and a fine-tuning varactor for mobile communica-
tion applications. Selection of operating modes is achieved by switching the
PIN-diode between radiators and tuning the varactor on an antenna’s shorting
line. The varactor used to achieve frequency fine-tuning does not need a DC
bias circuit and can expand the bandwidth without increasing the physical size.
When the PIN-diode is off, the radiation efficiencies have near 90%. On the other
hand, when the PIN-diode is on, the radiation efficiency abruptly decreases to
63% for the m-WiMAX (3.35-3.69 GHz) band due to the resistance effect of the
PIN-diode but remains 93% for the USPCS (1.85-1.99 GHz) band due to no ra-
diation through the PIN-diode for this band. The measured radiation antenna
peak gains are 2.84 and 2.81 dBi at the USPCS and WCDMA bands respectively.
Jeen-Sheen Row and Ting-Yi Lin [116], described a design for frequency-
reconfigurable antennas with conical-beam radiation. The design is based on the
TM02 mode of a coplanar annular-ring microstrip antenna and several shorting
strips are symmetrically placed along the circumference of the radiating patch to
vary its resonant frequency. To achieve multi frequency operations pin diodes are
used instated of shorting strips, antenna resonates at frequencies between 4.85
GHz to 5.79 GHz.The impedance bandwidth of antenna is between 1.6 to 3.1%(in
GHZ) and mea gain of the antenna is 1.0 to 2.6 dBi is observed.
Xavier Artiga et.al [117], reported in 2010, a Vivaldi antenna having the capa-
bility of dynamically rejecting interferers mainly aiming at multi standard com-
munication with dynamic frequencies allocation. This Vivaldi antenna suitable
for vehicle to vehicle communications operating at 2.5 - 8 GHz with a stopband
whose central frequency can be continuously tuned in the 1.8 - 5.8 GHz range.
The antenna presents good matching from 2.5 to 8 GHz while rejecting a band
47
whose central frequency can be tuned from 1.8 to 6 GHz, thereby covering the
principle standards such as WiFi, WiMAX, Bluetooth, WLAN (802.11a) etc.
Measured absolute gain values are 5 dBi at 2.5 GHz, 7.9 dBi at GHz and 11 dBi
at 8 GHz are obtained.
Shahrzad Jalali Mazlouman et.al [118], demonstrated in 2011, a reconfigurable
structures based on smart materials offer a potential solution to realize adaptive
antennas for emerging communication devices. In his paper, a reconfigurable ax-
ial mode helix antenna is studied. A shape memory alloy spring actuator is used
to adjust the height of a helix antenna. Measurement results for some heights
of the helix antenna (60, 70, 80 mm) as well as the simulation results for the 80
mm for comparison. It can be seen that good impedance matching is attained
around 4 - 4.5 GHz for all sweep points conical helix with a maximum radius of
18 mm and a radius ratio of 0.55, with 6 turns and its height varied between 50
to 90 mm confirm reasonable matching for a wideband around 3 GHz. Similar
to the cylindrical helix, the patterns of the conical helix at 3 GHz (not shown)
demonstrate that by varying the height of the helix from 40 to 95 mm, the gain
ranges from 10 to 11.5 dB and the HPBW from 65 to 50 with the total length of
the helix wire fixed, the pitch spacing and pitch angle are varied as the height is
varied.
Yufeng Yu et.al [119], proposed an electrically small frequency-reconfigurable
antenna with a very wide tuning band. Three varactor diodes are used to achieve
the tunable capacitance. With a modified feeding structure, the measured tuning
range of the fabricated antenna reaches from 457.5 to 894.5 MHz is observed.
When the capacitance of the varactor diodes changes from 0.12 to 4.0 pF, the
tunable frequency with reflection coefficients lower than -10 dB is from 517 to
856 MHz, with a tuning range of about 339 MHz. When the capacitance of the
varactor varies from 4 to 0.12 pF, the operating frequency of the antenna ranges
from 387.5 to 947 MHz. This tuning range (around 560 MHz) is very wide for
electrically small antennas.
Y. Tawk et.al [120], presented a new antenna system designed for cognitive
48
radio applications. The antenna structure consists of a UWB antenna and a fre-
quency reconfigurable antenna system. The UWB antenna scans the channel to
discover “white space” frequency bands while tuning the reconfigurable section
to communicate within these bands. The frequency agility is achieved via a ro-
tational motion of the antenna patch. Antenna designed for cognitive radio that
is able to tune throughout the whole band covered by the antenna is 2 GHz -
10 GHz.The measured gain of the antenna is 6.2, 6.67, 7.4, 7.77 and 8.4 dB for
deferent shapes of antenna.
Peter Ludlow and Vincent Fusco [121], reported on a reconfigurable small-
aperture evanescent wave guide antenna. Tuning and waveguide matching to free
space are simultaneously achieved by placing a printed iris with a shunt varactor
diode connected across the aperture of a below-cutoff waveguide. The maximum
dimension of the antenna is 0.36 at 2.49 GHz and it operates over an operating
frequency range of 2.05 GHz - 2.49 GHz with maximum realized gain of 5 dBi.
The measured results of the antenna as the reverse voltage on the varactor diode
are tuned from 0 V to 30 V. Here the antenna is operating at 2.05 GHz and 2.49
GHz over an operating frequency range of 19.4%.
Hattan F. Abutarboush et.al [122], proposed and presented a reconfigurable
wideband and multiband C-Slot patch antenna with dual-patch elements. It oc-
cupies a compact volume of 50 50 1.57 (3925 mm3) including the ground plane.
The antenna is operating in two dual-band modes and a wideband mode from 5
GHz to 7 GHz. Two parallel C-Slots on the patch elements are employed to per-
turb the surface current paths for excitation of the dual-band and the wideband
modes. By using two PIN diodes the operating frequencies are 5 GHz to 7 GHz
are obtained and impedance bandwidth of 33.52% measured gain of the antenna
is 3.72-4.92 dBi is also achieved.
Yue Li et.al [123], designed and discussed a folded loop-inverted F reconfig-
urable antenna for mobile phone applications. It is shown that loop antenna
mode and an inverted F antenna (IFA) mode are controlled by only one PIN
diodes with simple bias circuit. When the PIN diode is forward biased it works
49
as a series resistance. In the frequency band of 0.5 GHz - 2.5 GHz, the insertion
loss introduced by p-i-n diode is 0.1-0.2 dB at its typical bias current of 10-100
mA. When the PIN diode is reverse biased it is equivalent to series capacitance
approximately 0.45 pF the isolation is better than -15 dB. The Hepta-band is
covered with loop mode line the achieved bands are 790-870 MHz and 1490 MHz
- 2225 MHz covering GSM850, GPS, DCS, PCS and UMTS bands. For the IFA
mode the achieved bands are 845 - 980 MHz and 2240 - 2565 MHz covering
GSM900 and WLAN bands.
Xue Xia Yang et.al [124], presented a reconfigurable microstrip patch antenna
with polarization states being switched among linear polarization (LP), left-hand
(LH) and right-hand (RH) circular polarizations (CP). In his work he measured
10 dB bandwidths of for LHCP and RHCP are about 60 MHz. Good axial ratio
is about 0.5 around 2.438 GHz is obtained. The measured patterns of the recon-
figurable patch for LHCP at 2.439 GHz, RHCP at 2.433 GHz and LP of E-plane
at 2.42 GHz are achieved. For the LP the cross polarization in the broadside
direction is about 30 dB and the measured gain is 5.83 dBi.
J. Desjardin et.al [125], described the full implementation of a slot fed frequency-
reconfigurable rectangular dielectric resonator antenna (DRA). It uses two con-
ducting walls on opposite vertical faces of the DRA which are switched via con-
ducting tabs to be in contact or not with the ground plane. This antenna is de-
signed to operate between 3-8 GHz. The PIN diode loaded and varactor-loaded
DRAs achieved a tuning range of 91% and 55% respectively.
Chang Won Jung and Franco de Flaviis [126], investigated a double rectan-
gular patch antenna with 4-bridges is for use in IEEE 802.11b/g (2.4 GHz) and
802.11a (5.5 GHz) WLANs. A rectangular patch for the 5.5 GHz frequency band
is printed on the PCB substrate and is connected by 4-bridges to another rectan-
gular patch for the 2.4 GHz band to obtain dual band operation in one antenna
element. The 4-bridges can modify the desired frequency band from its original
frequency by changing their width. The gain of the 2.4 GHz patch is 5 dBi and
of the 5.5 GHz patch is 3.7 dBi at θ = 0..
50
S. V. Shynu Nair and Max J. Ammann [127], proposed and presented a recon-
figurable microstrip antenna for low cost adaptive beam-switching applications.
A small patch slotring structure is used as the radiating element where an asym-
metrical arrangement of PIN diodes is employed to switch the pattern in four
directions. The antenna provides pattern switching of 65 and 45 in its fundamen-
tal mode for the elevation and azimuth planes respectively. The 6 dB impedance
bandwidth commonly available to all modes is 2.6% centered at 2.055 GHz. The
designed antenna is resonating at frequency of 2.1, 2.05, 2.08 and 2.03 GHz, the
measured peak gain is 4.58, 2.71, 1.11 and 3 dBia respectively.
Won-Sang Yoon et.al [128], described a square patch antenna with a switch-
able circular polarization (CP) sense. The proposed antenna has four L-shaped
slots on the ground plane and the CP radiation is generated by current perturba-
tion due to the slotted ground plane. The bandwidths of the proposed antenna
are measured for the impedance bandwidth of the -10 dB RL and CP bandwidth
within a 3 dB AR. The impedance bandwidths of the 10 dB RL for both RHCP
and LHCP are 110 MHz (2.41 - 2.52 GHz) and the CP bandwidths in a 3 dB
AR in the direction are 30 MHz (2.47 - 2.50 GHz) for both LHCP and RHCP.
The minimum ARs in the direction are obtained at 2.49 GHz and the values are
1.90 dB for RHCP and 1.94 dB for LHCP. The peak gains at 2.49 GHz are 2.97
dBi for RHCP and 2.90 dBi for LHCP. For both directions antenna has great loss
tangent and antenna may yield low radiation efficiencies and gains.
Daniel Snchez-Escuderos et.al [129], presented a reconfigurable slot-array an-
tenna with RF-MEMS. By this technique obtained an isolation of 12 dB at max-
imum between two states of the switch. Due to switch effect radiation efficiency
was computed for both states, and it obtained an radiation efficiency of 36% for
the ON state and 93% for the OFF state is observed.
Y. K. Park and Y. Sung [130], presented a reconfigurable antenna for a quad-
band (GSM900/GSM1800/GSM1900/UMTS) mobile handset application. In this
structure a bias network related to PIN diode and it is simple compared with other
51
passive quad-band. When the antenna is operating in the PIFA mode the 7 dB
bandwidth covers the GSM 900 (880 - 60 MHz) band. When operating in the loop
mode the 7 dB bandwidth covers the GSM1800 (1710 - 1880 MHz), GSM1900
(1850 - 1990 MHz) and UMTS (1920 -2170 MHz) band.
Huda A. Majid et.al [131], demonstrated a frequency reconfigurable microstrip
slot antenna. The antenna is capable of frequency switching at six different fre-
quency bands between 2.2 and 4.75 GHz. Five RF PIN diode switches are posi-
tioned in the slot to achieve frequency reconfigurability. The measured resonant
frequency bands are shifted from 4.60 GHz to 2.30 GHz and corresponding band-
width is shifted from 250 MHz to 210 MHz respectively. The resonant frequencies
are shifted with the average of 532 MHz. The average measured gain is 1.9 dBi
and antenna size reduction 33% is achieved.
Gang Chen et.al [132], presented a novel frequency-reconfigurable folded slot
antenna that could operate in two modes. Both modes have two resonant fre-
quencies. The measured resonant frequencies for Mode 1 are 3.29 GHz and 5.2
GHz. For the Mode 2 the measured frequencies are 2.36 and 5.7 GHz. For this
antenna the measured peak gain for Mode 1 is 5.22 dBi at 3.29 GHz and 5.4 dBi
at 5.21 GHz. The measured peak gain of Mode 2 is 4.45 dBi at 2.36 GHz and 4.9
dBi at 5.7 GHz is obtained.
Yong Cai et.al [133], demonstrated reconfigurable Yagi-Uda antenna with 46%
frequency tunability for the UHF band. With a simple and efficient biasing cir-
cuitry a design with multiple directors loaded with varactors was realized which
allows a high gain to be maintained. By changing the dimensions of this antenna
which is generates multiple frequency bands between 478 MHz to 74 MHz is ob-
served and radiation efficiency is above 85% over the entire tuning bandwidth is
achieved.
Changying Wu et.al [134], designed and implemented a reconfigurable patch
antenna using reed switches. The antenna comprises a pair of hexagonal patches
and a reed switch that connects the two patches at their adjacent vertices. En-
52
ergizing a coil that either closes or latches the reed switch will shift the resonant
frequency of the antenna. Because the coil and associated electronics are located
beneath the ground plane they do not materially affect the radiation performance
of the antenna. The reed switches have the potential to be used in full-band and
full-polarization antennas and design concepts are explained.
Parisa Lotfi et.al [135], presented a compact reconfigurable asymmetric copla-
nar strip (ACS)-fed monopole antenna. This reconfigurable performance with
capability to operate in the ultra wideband (UWB) frequency from 3.2 GHz to
11 GHz with two stop bands of 3.3 - 4.2 and 5 - 6 GHz and triple WLAN fre-
quency bands of 2.4 - 2.9, 3.6 - 4.4 and 5-6 GHz. The UWB antenna uses a
simple rectangle patch with folded shape slit and stub as rejecting elements and
the mobile antenna uses an arc-shaped stub and inverted L-shaped stub as res-
onating elements. The performance agility and reconfigurable ability is achieved
via a circular rotational motion of the patch.
A. Zohur et.al [136], presented a frequency reconfigurable electrically small
antenna with a high reconfigurable frequency between two frequency bands (718
and 4960 MHz).The reconfigurability is obtained using a single RF MEMS switch.
The antenna achieves a reasonably wide measured bandwidth of 2.6% at 718 MHz
for electrically small lateral dimensions.
Francesca Venneri et.al [137], described an aperture-coupled reflectarray ele-
ment giving a full phase tuning range with a single varactor diode. The full phase
agility is achieved by a proper optimization of the phase tuning line thus provid-
ing an alternate inductive/capacitive effect able to avoid the use of two varactor
diodes usually adopted in similar existing configurations. Furthermore, an own
synthesis procedure is applied to obtain the proper biasing voltages giving the
prescribed H-plane field. A reconfigurable reflectarray element is tuned by a sin-
gle varactor diode and has been considered for the realization of a reconfigurable
reflectarray prototype.
M. J. Ammann and R. Farrell [138], described a dual-band miniaturized
53
printed monopole for integration in modern wireless systems. The printed monopole
is augmented with two arms, resonant at slightly different frequencies providing
a broadened response for the upper band. The achieved bandwidth for the high
band is 36%. These antennas are proposed for the emerging dual-mode multi-
band WLAN transceivers which operate over a wide range of bands as dictated
by national authorities.
Hamid Boudaghi et.al [139], presented a novel compact frequency-reconfigurable
monopo-le antenna with five switchable states including an ultra wideband (UWB)
state, three narrowband states and a dual-band state. The frequency-reconfigurable
capability of the antenna is achieved by using a switchable slotted structure on
the ground plane. The antenna which supports most applicable frequency bands
above 2 GHz is used in multiradio wireless systems.
Chi-Yuk Chiu et.al [140], studied a new frequency-reconfigurable antenna
structure which we denote as a pixel slot antenna for communication. The an-
tenna makes use of a canonical switched slot element that is concatenated together
to form various radiating structures. The resonant path of the pixel slot antenna
can be a conventional slot or a slot plus a loop so higher degrees of freedom in
generating various resonant frequencies are achieved. The maximum-to-minimum
achievable resonance values of a demonstrated 4-switch single-pixel slot antenna
are 3.30 GHz to 1.56 GHz in which the feed mechanism remains unchanged.
Abubakar Tariq and Hooshang Ghafouri-Shiraz [141], introduced a novel copla-
nar waveguide (CPW) bandpass filter using short-circuit slotlines and varactor
diodes. This bandpass filter is integrated with a CPW wideband antenna it
produces frequency agility with a wideband mode and a continuous narrowband
mode. The design of another CPW filter based on a square ring resonator with
switches is present and applied to a wideband antenna making it reconfigurable.
Jia Fu Tsai and Jeen Sheen Row [142], described a reconfigurable design for a
dual-feed square-ring microstrip patch antenna. The dual feeds are used to excite
two orthogonal modes of the antenna and each feed network is composed of a cou-
54
pling patch, an impedance transformer and a variable capacitor. In addition the
two feeds are connected to a single input port through a T-junction power divider.
The proposed design can perform polarization diversity at different frequencies
by tuning the capacitance values of the two capacitors. A prototype integrating
with a pair of varactor diodes and related dc bias circuits is constructed. Both
of them demonstrate that the prototype can provide one linear polarization and
two circular polarizations at one operating frequency moreover the operating fre-
quency can also be tuned to adjacent frequencies.
Lim J.H et.al [143], presented a frequency reconfigurable planar inverted-F
antenna (PIFA) using real PIN-diodes for mobile worldwide interoperability for
microwave access (m-WiMax) applications. This antenna not only alters the fre-
quency band of the m-WiMax using PIN-diode switching but it also has a small
profile using capacitive load within an FR4 dielectric constant substrate. The
PIFA consists of the following: a main radiator, an additional radiator, a band-
switchable capacitive load, two PIN-diodes and control circuits. Depending upon
whether the diodes are on or off the antenna operates for deferent frequencies
for worldwide m-WiMAX bands. They are also investigating the effect of load
capacitance, a parametric analysis is performed by sweeping the length and width
of the capacitive load is also presented.
Hattan F. Abutarboush and R. Nilavalan [144], proposed and presented a re-
configurable antenna based on E-shaped structure with bandwidth controlled..The
bandwidth of the antenna is increased and controlled from 3.4% to 23% by vary-
ing the capacitance of the varactor diodes. The bandwidth is cover the frequency
range from 1.85 GHz - 2.33 GHz is observed.
Zhouyuan Li et.al [145], reported a new class of multifunctional reconfigurable
antenna array (MRAA). The main goal of enhancing the spectral efficiency of ex-
isting and future wireless networks. The MRAA presented in this paper is formed
by the linear combination of four identical multifunctional reconfigurable antenna
(MRA) elements. MRAA prototypes operating in the frequency range of 5.4 GHz
- 5.6 GHz have been measured. The realized gain values of the MRAA prototypes
55
were found to be 13.5 and 0.2 dB. These gain values are 2-3 dB higher than those
of the standard array compared to patch.
M. S. Nishamol et.al [146], presented a novel compact dual frequency mi-
crostrip antenna with frequency and polarization tunability. The tuning is real-
ized by varying the effective electrical length of slot with an embedded capacitor
at the center of X-slot. The impedance matching by increasing the value of C
from 2.2 pF to 100 pF and increase in C offers tuning to 1.594 GHz from 1.748
GHz is observed. The antenna offers a frequency ratio of 1.66 and 1.09 for first
and second resonances with linearly polarized radiation. The measured antenna
peak gain of 3.39 dBi in the direction of maximum radiation. A high tuning range
of 34.48% and 14.3% is achieved resonant frequencies.
Ahmed Khidre et.al [147], proposed and presented a polarization reconfig-
urable E-shaped patch antenna with wideband performance for wireless com-
municaton.The antenna is capable of switching its polarization from right hand
circular polarization (RHCP) to left hand circular polarization (LHCP) and vice
versa. Its structure is simple and consists of a single layer single feed E-shaped
patch and two RF switches placed at appropriate locations in the slots. The de-
sign targets the WLAN IEEE 802.11 b/g frequency band (2.4 - 2.5 GHz) is used
in various wireless communication systems. The antenna exhibits a 7% effective
bandwidth from 2.4 GHz to 2.57 GHz with an 8.7 dBi is achieved.
2.3 Motivation for Present Work
From the above exhaustive review of the literature it is clear that an enormous
amount of work has been done on few types of reconfigurable antenna geome-
tries with different feeding techniques. Each type of geometry is having its own
merits and demerits in terms of antenna performance. In all the above cases
size reduction and bandwidth are moderate. In order to improve the parameters
further different techniques have been used. Also the work on reconfigurability
property with size reduction has been rarely found in the literature survey. Most
56
of the research work has been considered for higher frequencies and a less work
has been performed on lower frequencies. In view of the above, study has been
made by incorporating new designs of reconfigurable antenna geometry for lower
frequencies which are suitable for wireless applications.
Further from the literature survey it is observed that band width and impedance
of band width has not yet been studied with respect to reconfigurable antenna
designs at lower frequency. So, we implemented proposed geometry with antenna
structure and different feed techniques in order to improve the return loss, band-
width and impedance band width of the antenna.
In view of this a systematic study of reconfigurable microstrip antennas is
carried out in following steps.
• Design and development of reconfigurable microstrip antenna with rectan-
gular spiral slots for Bluetooth, GSM and wireless applications.
• In the next step design and implementation of slotted reconfigurable mi-
crostrip antenna for wireless application has been studied.
• Another configuration is varactor diode loaded double square reconfigurable
microstrip patch antenna for wireless applications has been studied.
• To improve the performance of the microstrip antenna, design of compact
reconfigurable multi frequency microstrip antennas for wireless applications
has been made.
• To improve the size reduction of antenna E-slot reconfigurable microstrip
antenna has been made and studied.
• One more antenna configuration is Design of U and E-shape slots Recon-
figurable Microstrip Antenna (UES -RMSA) for wireless applications has
been studied.
• To improve the compactness of the microstrip antenna, Design of T-slot
reconfigurable microstrip antenna (TS-RMSA) has been made.
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The above extensive study has been made by designing and simulating the var-
ious reconfigurable antenna geometries with different feed technique using IE3D
software and then fabricated to carry out the measurements using vector network
analyzer.
The next chapter deals with the methodology and experimental setup in detail.
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