project review final

8/8/2019 Project Review Final

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A REVIEW REPORT ON THE RECONFIGURABLE

ANTENNA ARRAY.

(Subject Code:-ECE 1052)

Submitted by

BIPUL GOSWAMI

ROLL NO:-10/ECE/420

A first Semester

Student

of

MASTER OF TECHNOLOGY

In TELECOMMUNICATIONENGINEERING

NATIONAL INSTITUTE OF TECHNOLOGY, DURGAPUR.


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MAHATMA GANDHI AVENUE, DURGAPUR-713209,

ddd INDIA.

Table of Contents

LIST OF FIGURES .............................................................................................3

1. ABSTRACT.................................................................................................... 4

2. INTRODUCTION............................................................................................5

3. MOTIVATION OF ANTENNA RECONFIGURABLITY .......................... 5

4. APPLICATIONS ........................................................................................... 6

5. HOW TO ACHIEVE RICONFIGURABLITY IN ANTENNA ARRAY....... 6

6.COMPARISON BETWEEN SEMICONDUCTOR AND

MICROELECTROMECHANICAL SYSTEM (MEMS) SWITCHES FOR

RECONFIGURABLE ARRAY ANTENNA................................................................ 8

7. HOW DOES MIMO WORK?..........................................................................9

8.PHASED ARRAY ANTENNA......................................................................12

9. FUTERE PERSPECTIVES ..........................................................................15

10. CONCLUSIONS .........................................................................................16

11. ACKNOWLEDGEMENT ..........................................................................16


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12. REFERENCES ......................................................................................... 16

List of Figures

1. Diagram of a reconfigurable antenna system using MEMS switching......7

2. Diagram of MIMO system block...............................................................9

3. Schematic of the proposed Reconfigurable Antenna Array. L=50mm,

d=24mm....................................................................................................11

4. S Parameter S11 for the antenna of figure2........................................... .12

5. S Parameter S11 for the antenna of figure2..............................................12

6. left: two antenna elements, fed with the same phase, right: two antenna

elements, fed with different phase shift...................................................13

7. Schematic of reconfigurable leaky-wave/patch-aperture array...........15


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Abstract:

A reconfigurable antenna capable of dynamic reconfigurability of several antenna

parameters. Specifically, the present invention is an antenna comprising a plurality of surface

PIN devices arranged in a grid like array. Each of the SPIN devices can be individually

activated or deactivated. When a SPIN device is activated, the surface of the device is

injected with carriers such that a plasma is produced within the intrinsic region of the device.

Various SPIN devices can be activated to electronically paint a conductive pattern upon the

substrate supporting the PIN devices. Through selective activation of the SPIN devices

various surface antenna patterns can be produced upon the substrate including dipoles, cross

dipoles, loop antennas, Yagi-Uda type antennas, log periodic antennas, and the like.

Reconfigurable antenna arrays may also comprising multilayer planar radiators that

are switched using a network of MEMS switches. Due to the multi-scale nature of these

structures, their numerical modelling poses serious computational challenges. The advantages

and dis-advantages of using PIN diode switch and MEMS switch are also discussed in this

review report.

With the increase in traffic on the internet, there is a greater demand for wirelessmobile. These applications need antennas that are not only broadband, but can also work in

different frequency spectrums. Even though there is a greater demand for such applications, it

is still imperative to conserve power. Thus, there is a need to design multi-broadband

antennas that do not use a lot of power. Reconfigurable antennas can work in different

frequency spectrums as well as conserve power. The novel reconfigurable antenna designs

can be extended to Multiple Input Multiple Output (MIMO) environments and military

applications.


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Introduction:

Reconfigurable antennas is a broad term, grouping many applications, depending on

the nature of the reconfigurable property. For instance, reconfigurable antennas can modify

their radiation patterns [1], their frequency [1], or provide multiple-element antenna

functionality [1].However reconfigurable antennas have special virtues, such as the ability to

comply with future standards through updates. Moreover, the use of reconfigurable antennas

can simplify the process of designing multiple band antennas. Secondly, for a radio requiring

wide band tuning but moderate instantaneous band width such as mobile TV (DVB-H, DMB-

T, etc.), reconfigurability could mean better performance and size reduction. Finally it is well

known that a very small wideband antenna has reduced performance with respect to a narrow

band one, due to the trade off between size and band width.

The reconfigurablity of an antenna array has the capacity to change an individual

radiators fundamental operating characteristics through electrical, mechanical, or other

means.

Traditional phasing of signals between elements in an array to achieve beam

forming and beam steering does not make the antenna reconfigurable.

Ideally, reconfigurable antennas should be able to alter their operating

frequencies, impedance bandwidths, polarizations, and radiation patterns

independently to accommodate changing operating requirements.


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Motivation for Antenna Reconfigurability:

1. Using too many antennas for multiple systems are very confusing and difficult to

control. The reconfigurable antennas reduce number of antennas on the platforms.

2. In integrated multifunctional systems the reconfigurable antennas increase antenna

functionality in small packages.

3. Expand antenna functionality past traditional capabilities. We can develop new

antennas that meet new needs

Applications:

The reconfigurable antenna is a revolutionary new type of antenna that controls the

radiation pattern by dynamically adjusting its aperture. It provides a unique way to cover

different frequency bands and in an array, provides beam steering capability. There is

therefore a great demand for reconfigurable antennas in the field of wireless communications,

satellite communications, radar etc.Potential applications of reconfigurable antenna array isin Cognitive Radio, SDR, MIMO, and Reconfigurable Sensing Systems. The reconfigurable

antennas have attracted much attention in wireless communication systems such as cellular-

radio system, airplane radar, smart weapons protection and point-to-point communication.

How to Achieve Reconfigurablity in Antenna Array:

When considering on adding new features to existing antennas, question arises

about the benefits and applications of doing so. Reconfigurable antenna will be an attractive


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feature in the modern wireless communication system because it enables to provide a single

antenna to use for multiple systems. In the reconfigurable antenna, the structure of the

antenna can be changed by integrated with switches such as PIN diode switches [9], the field-

effect transistor (FET)[2], the photo conductor switches [10] or by electromechanical system

(MEMS) switch [7], which were proposed a few years ago. By controlling the states of the

switches, on/off, several approaches are proposed for implementing the reconfigurable

antenna. Most of these approaches were able to alter the fundamental characteristics such as

operating frequency, bandwidth, polarization characteristics and radiation pattern. One of the

applications of the reconfigurable antenna is that, it can desirably steer the beam pattern into

many directions, [5, and [6]. In [7], the authors presented reconfigurable antennas, which

were radiated at different beam patterns by adjusting the apertures and maintaining their

operating frequencies. The antenna presented in [8], describes a dual band dipole antenna

integrated with series MEMS switches. However, this method typically uses a dual operating

frequency to reconfigure a beam pattern.

Reconfigurable antennas with the antenna aperture controlled using PIN junctions

[1,2] or using photonically controlled devices [3] have been reported. Many researchers have

incorporated microelectromechanical (MEMS) switches in their antenna designs to attain

reconfigurability with microstrip patch antennas [4-6]. If a reconfigurable antenna consists ofan array of individual antennas where each individual antenna is connected to its neighbours

with a switch (e.g. MEMS switch, FET switch), and the resonant frequency, beam direction

etc of the overall antenna can be varied by turning on various switches.


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Figure 1: Diagram of a reconfigurable antenna system using MEMS switching.

A method and apparatus for reconfiguring an antenna array by optical control of MEMS

switches is shown in the figure-1. A light source is provided to direct light to individual

optically sensitive elements which control delivery of actuating bias voltage to the MEMS

switches. The light source is preferably separated from the antenna array by a structure which

conducts the controlling illumination but provides a high impedance electromagnetically

reflective surface which reflects electromagnetic radiation over the antenna operating

frequency range with small phase shift, and which is disposed very close to the antenna array.

Optically sensitive elements preferably include photoresistive elements, which are best

formed in the substrate upon which the MEM switches are formed, and may include

photovoltaic elements.


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Comparison between Semiconductor and micro-electromechanical system

(MEMS) Switches for Reconfigurable Array Antenna:

Conventional PIN diode and FET switches suffer from narrow bandwidth, poor

isolation and high insertion loss, high power consumption and significant inter-modulation

products due to their non-linear characteristics. RF-MEMS switches, on the other hand

exhibits excellent switching characteristics over extremely wide frequencies. Furthermore

RF-MEMS switches can be on almost any substrate. One popular application of RF-MEMS

switch would be to reconfigurable phased array antenna for wide band application. A MEMS-

based switched multiband antenna can be reconfigured within micro-seconds (s) to serve

different applications at discrete frequency bands. These systems can be used for tracking

Air-bone or land mobile targets, making them very useful to military. Their applications can

also be extended for commercial purposes such as mobile terrestrial and satellite

communications at l- and s-bands, satellite navigation at l-bands and anti collision radars for

automotive v-band.

Though RF-MEMS switches are very promising candidate for reconfigurable

antenna, yet they suffer from several disadvantages such as slow switching speed in the order

of s, comparatively high actuation voltage(10-50V) and hot switching in high power

application. RF-MEMS devices also exhibits striction phenomenon where parts of the

device can be bonded together upon physical contact, and RF-induced switching when high

rms voltage closes the switch by itself without the assistance from the DC bias. However the

advantages are far outweigh than the limitations. The MEMS technology is very promising

field; it is only a matter of time that all the limitations can be overcome.

How does MIMO work?


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Figure 2: Diagram ofMIMO system block

Wireless communications use air as the media of transmission for the information.

Therefore, the transmitted signals in such a scenario are affected by reflections from many

scatters located close to the transmitter, receiver and between both. These scatters are, for

instance, buildings, but also cars, which are in movement. As the receiver is moving as well,it is logical to think that, as the set of scatters changes in each instant of time, the scenario

will change as well. As a consequence, and as it is well known in mobile communications,

the signals are affected by what it is called fading. The received signal falls in a dip due to the

fact that the sum of all the contributions is destructive. Fading is a consequence of the

multipath propagation and it is a random phenomenon. We deal with the so called short-term

fading or fast fading. This kind of fading has a statistical distribution which can fall within

the Rice, Rayleigh and Nakagami distributions. Rician fading occurs when there is Line Of

Sight (LOS) and as consequence there is one or more dominant contributions to the received

signal.

In the year June 2007 Akbar M. Sayeed and an Indian scientist Vasanthan Raghavan

published a paper titled Maximizing MIMO Capacity in Sparse Multipath With

Reconfigurable Antenna Arrays [2]. In this paper, they presented a theoretical

framework for studying the impact of reconfigurable antenna arrays on the capacity of

MIMO wireless communication systems. They showed that the sparsity of multipath can be


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exploited for dramatically increasing MIMO capacity at low SNRs by matching the array

configurations (antenna spacing) to the level of sparsity. We focus on uniform linear arrays

(ULAs) of antennas and provide a systematic characterization of the impact of antenna

spacing on capacity.

In the year March 2008 Daniele Piazza, and his followers worked on Design

and Evaluation of a Reconfigurable Antenna Array for MIMO Systems [3]. In this

paper, the antenna system under study consists of an array of two reconfigurable microstrip

dipoles; the two active elements of the array can be reconfigured in length using PIN diode

switches. The setting of the different switches results in different geometries of the antenna

and, as a result, different levels of inter-element mutual coupling and array far-field radiation

patterns. The goal of such a system is to choose the configuration of switches in a

environment/channel adaptive fashion to decrease MIMO spatial channel correlation and

subsequently maximize channel capacity.

In December,2009,Prof. Zhengwei Li and his followers worked on Compact

reconfigurable Antenna array for adaptive MIMO systems[5]. In this research they

proposed a four-element antenna array operating in the UMTS band (19202170 MHz). The

array has eight PIN-diodes embedded in the feeding network to select any sub-set of

elements. For evaluation, an adaptive MIMO system was set up and a measurement campaign

was taken in an indoor multi-path environment. The measurements were performed over a

300 MHz bandwidth centered at 2.05 GHz, covering the UMTS band. The results show that

different channel conditions prefer different antenna array configurations. Therefore, in

varying channel conditions the antenna array can support antenna selection algorithms to

select the best sub-set of elements to increase channel capacity .

Reconfigurable antennas for MIMO systems have been researched in some paper

recently [2]-[4]. Some concentrate on pattern diversity [3], while some realize polarization

reconfiguration [4]. However, in most cases, it is difficult to integrate multiple reconfigurable

antennas into a MIMO wireless device, due to their large size.

The proposed antenna array [6] is designed on a planar FR4 substrate, with a

thickness of 0.8mm and a relative dielectric constant of 4.4. The ground plane and the two

antennas are on the same layer. Fig.1 shows the schematic of the reconfigurable antenna

array, composed of two microstrip antennas located at upper-left and upper-right corners of

the substrate. The substrate has a size of 50mm50mm, and the two antennas are symmetric


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with respect to the center line of the substrate. And each antenna element includes two PIN

diodes and respective bias network, so each antenna can be controlled individually. Each

microstrip antenna has a line width of 1mm, and the two antenna elements are separated by a

distance of 24mm. The antennas are directly fed by coaxial cables. By changing the states of

the PIN diodes, each antenna element can have different operation modes. For each antenna

element, there are two valid modes defined as U and D.

Figure 3. Schematic of the proposed antenna array. L=50mm, d=24mm

Mode U denotes that the upper PIN diode is forwardly biased while the lower one is

reversely biased. At this mode, as the upper horizontal strip is shorten to the ground, the

current flow is mainly distribute on the vertical strip, so the antenna shows vertical

polarization. Mode D denotes that the lower PIN diode is forwardly biased while the upper

one is reversely biased. And at this mode, the antenna shows horizontal polarization, for the

similar reason. So this two elements array can define a total of four configurations, UU, UD,

DD and DU, with two orthogonal polarizations. In practical applications, the operation modes

can be switched depending on real-time channel responses in order to maximize the channel

capacity and enhance the robustness of MIMO communications.


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As can be seen, the two modes have different frequency responses, which indicate that

frequency reconfiguration can be realized in the antenna. Mode D only works at the band of

2.4GHz, while mode U covers both 2.4GHz and 5.15GHz. And the bandwidth is 400MHz

and 600MHz respectively. Even the distance between the two antenna elements is less than

/4 , the S21 is still below -10dB, which indicates that the two elements have a good

isolation.

Reconfigurable Phased Array Antenna:

A phased array antenna is composed of lots of radiating elements each with a phase shifter.

Beams are formed by shifting the phase of the signal emitted from each radiating element, to

provide constructive/destructive interference so as to steer the beams in the desired direction.
http://www.radartutorial.eu/06.antennas/an16.en.htmlhttp://www.radartutorial.eu/06.antennas/an16.en.htmlhttp://www.radartutorial.eu/18.explanations/ex31.en.htmlhttp://www.radartutorial.eu/18.explanations/ex31.en.htmlhttp://www.radartutorial.eu/06.antennas/an16.en.html


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Figure 6: left: two antenna elements, fed with the same phase, right: two antenna elements,

fed with different phase shift

In the figure 6 (left) both radiating elements are fed with the same phase. The signal is

amplified by constructive interference in the main direction.

In the figure 6 (right), the signal is emitted by the lower radiating element with a phase shift

of 10 degrees earlier than of the upper radiating element. Because of this the main direction

of the emitted sum-signal is moved upwards.

(Note: Radiating elements have been used without reflector in the figure. Therefore the back

lobe of the shown antenna diagrams is just as large as the main lobe.)

The main beam always points in the direction of the increasing phase shift. Well, if

the signal to be radiated is delivered through an electronic phase shiftergiving a continuous

phase shift now, the beam direction will be electronically adjustable. However, this cannot be

extended unlimitedly. The highest value, which can be achieved for the Field of View (FOV)

of a phased array antenna is 120 (60 left and 60 right).

Advantages & Disadvantages of the traditional Phased Array Antenna is given in the table.
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Advantages Disadvantages

highgain width los side lobes

Ability to permit the beam to jump from one

target to the next in a few microseconds

Ability to provide an agile beam under

computer control

arbitrarily modes of surveillance and

tracking

multifunction operation by emitting several

beams simultaneously

Fault of single components reduces the

capability and beam sharpness, but the

system remains operational

the coverage is limited to a 120

degree sector in azimuth and

elevation

deformation of the beam while

the deflection

low frequency agility

very complex structure

(processor, phase shifters)

still high costs

In the year August 2002 James Sor, Chin-Chang Chang, Yongki Qian, and Tatsuo

Itoh,fellow,IEEE published a paper titled A Reconfigurable Leaky-Wave/Patch

Microstrip Aperture for Phased-Array Applications [11].The antenna structure is shown

in the following figure.

Fig7.: Schematic of reconfigurable leaky-wave/patch-aperture array.
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In this research they developed topologies and techniques where a number of antennas that

cover different frequency bands and/or serve different functionalities can share a single

physical aperture without sacrificing system performance.

To do this they proposed a reconfigurable leaky-mode/multifunction patch-antenna

array structure, as shown in Fig. 1. In this scheme, long leaky-wave apertures form a linear

array along the x-axis and can be frequency scanned with high gain ( ~12 dB). Using

conventional or microelectromechanical system (MEMS) switches, each of the leaky-wave

apertures can be segmented into several smaller patch-antenna apertures, with the mode of

operation controlled by the state of the switches. The switches act simply as short circuits

when turned on and as open circuits when turned off. This unconventional, but versatile

system presents a number of advantages over traditional phased-array systems. First, the

combination of the patch and leaky-wave apertures provides multiband frequency coverage

with a wide variety of radiation characteristics. For example, the individual resonant patches

can be designed to operate at multiple frequency bands with moderate gain about broadside,

while the high-gain

leaky-wave apertures provide moderate bandwidth about the elevation angle.

Collectively, the radiating apertures provide more flexibility and wider frequency coverage

than traditional phased-array systems. Second, the aperture itself is relatively simple to

implement and construct, utilizing only a moderate number of switches. Systems that rely on

an excessive number of switches will inevitably suffer from poor efficiency and integration

issues. Additionally, the uniplanar nature of the reconfigurable aperture enables the aperture

to be conformably mounted to any flat surface. Finally, both the leaky-wave and patch-

antenna structures to be used in the reconfigurable aperture are unidirectional radiators

exhibiting moderate to high gain [1]. This improves the overall efficiency of the system and

is particularly attractive for target tracking applications.

Future Perspectives:

Reconfigurable antenna arrays increase the flexibility of adaptive MIMO systems. At

present, most designs have adopted antenna arrays with reconfigurable elements. However,

antenna selection is also an effective method, which has not been fully investigated.

How does closing the switches affect the input impedance of the antenna? i.e. if two


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patch antennas have an input impedance of 50 Ohms, and one of the patch antennas is fed,

what is the input impedance of an antenna created by connecting both patch antennas together

by closing a switch?

Future work will concentrate on multiband pattern reconfigurable

antenna to make it appropriate for use in multiband or wide band MIMO

communications. And we will study the system performance with the

reconfigurable antenna array.

Conclusion:

A reconfigurable antenna array can increase the flexibility of adaptive MIMO system

by their reconfigurable configuration and radiation/polarization properties. It is capable ofdynamic reconfigurability of several antenna parameters. Specifically, the present invention

is an antenna comprising a plurality of surface PIN devices arranged in a grid like array.The

use of RF-MEMS switches may provide an improved solution to replace PIN diodes due to

their high Q-property.

Acknowledgement:

I would like to thank Prof. Dr. Rowdra Ghatak and Mr. Sujit Kumar Mandal for their helpful

discussions.

References:

[1] C. A. Balanis, Antenna Theory: Analysis and Design. New York:Wiley, 1997.

[2] B. A. Cetiner, H. Jafarkhani, J. Y. Qian, H. J. Yoo, A. Grau, and F. De Flaviis,

Multifunctional reconfigurable MEMS integrated antennas for adaptive MIMO systems,

IEEE Commun. Mag., vol. 42, no. 12, pp. 6270, 2004.

[3] D. Piazza, N. Kirsch, A. Forenza, R. Heath Jr., and K. Dandekar, Design and evaluation

of a reconfigurable antenna array for MIMO systems,"IEEE Trans. Antennas Propag., vol.

56, no. 3, 2008.

[4] P. Mookiah, D. Piazza, Reconfigurable spiral antenna array for pattern diversity in

wideband MIMO communication systems, IEEE Antennas and Propagation Society

International Symposium, pp.1-4, July 2008


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