1.Stripline: · Web view2019-07-21 · In recent years, the demand for antennas with multiband operations has been increased rapidly since such antennas play a major role in combining

Reconfigurable Antenna with Frequency Switching Capability for C-Band Application

CHAPTER-1

INTRODUCTION

1.1 Introduction

In recent years, the demand for antennas with multiband operations has been increased rapidly since such antennas play a major role in combining multiple communications standards in a single compact wireless system. An antenna is a device that is used to convert guided electromagnetic waves into electrical signals and vice versa (i.e. either in transmitting mode or in receiving mode of operation). Antennas are frequency dependent devices. Each antenna is designed for a certain frequency band and outside of this band, antenna rejects the signal. Therefore we can say antenna is a band pass filter and transducer. Antennas are essential part in communication systems therefore understanding their basics are important. With the advances in telecommunication, the requirement for compact antenna has increased significantly. In mobile communication, the requirement for smaller antennas is quite large, so significant developments are carried out to design compact, minimal weight, low profile antennas for both academic and industrial communities of telecommunication. The technologist focused into the design of microstrip patch antennas. Many varieties in designing are possible with microstrip antenna. The first chapter provides an introduction to microstrip patch antennas with their advantages and disadvantages. Then the feeding techniques, analysis method and different parameters of microstrip patch antenna are presented.

1.2 Literature SurveyAn antenna is a structure or device used to collect or radiate electromagnetic(EM) waves. In some sense the first antenna dates from 1887, when Heinrich Hertz designed a brilliant set of wireless experiments to test James Clerk Maxwell’s hypothesis. Hertz used a flat dipole for transmitting antenna and a single turn loop for a receiving antenna. For the next fifty years antenna technology 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 deforests [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 array culminated in the work of Hidetsu Yagi and ShintaroUda in 1926.S.Nikolaouet.al[80], demonstrated an antenna use of pin diodes to reconfigure 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.Bernhard J.T. [5-6] gave a commemoration of Deschamps’ and Sichak’s “Microstrip Microwave Antennas” a survey of 50 years development in this field. Deschamps invent microstrip antenna in 1953, in USA. During the period of 1955, radiation from discontinues in strip lines is studied. Lewin was introduced new techniques for microstrip antenna rectangular and cylindrical array designed and measured for different application. The main characteristics of an antenna i.e. side lobe level, coupling effect and radiation mechanism of an open-circuit microstrip termination as slot radiators has been analyzed and discussed. Howell J.Q. and Byron E.V. [37, 12] designed a flush- mounted antenna for phased array. Practically, is was a low profile MSA with very small height and coaxial feeding technique. Nowicki T.E. [72] presented antenna designing Parameters like height of dielectric substrate, Electronics And Communication Engineering Page1


Ɛr are very important for desired output. Traut G.R. gave a high dielectric constant material such as ceramic-fillers properties and Copper-clad sheet or backed laminates based on composites of poly-Tetra-Fluoro- ethylene PTFE, fluorocarbon polymer used for antenna designing. Lo Y. T. et al [53, 54] described the thin cavity model between the ground plane and microstrip patch which is bounded by magnetic field and electric field and a technique to calculate feeding point for different design of MSA. Chandra Prakash and Gangwar RPS [20] presented a “Spiral multilayered MSA for Med-Radio Band. Derneryd A.G. and Karlson I. [23] constructed the broadband microstrip antenna. The low dielectric constant of substrate is used; patch is design on thin glass fiber supported by low density foam over ground plane. Lu Jui-Han and Wong Kin Lu [59] proposed a design of equilateral triangular printed antenna to obtained dual frequency. Foroughipour S.M. and Esselle K.P. [36] presented analysis of coupling between inclined MSA using FDTD techniques. The mutual coupling effect has been investigated by using transmission line matrix method for microstrip patch. Simulation process in time domain for the excitation a modified Gaussian function. Rao J. Chandrasekhar has been designed in this paper with a probe feeding, the impedance bandwidth of 103.6% (2.0-6.3 GHz) at center frequency of 4.2 GHz has been obtained with a return loss of -30 dB and a VSWR of less than 1.07. Schaubert D.H. and Farrar F.G. droved that the bandwidth of antenna can be improved by use of parasitic elements with improved bandwidth around 2.5%. Wood al introduced a technique in which he uses two capacitance used to excite the parasitic element placed parallel to the radiating edges. Ghalibafan J. and Attari A. R.[38] presented a broadband U shape slot electromagnetic coupling probe feeding technique. Poddar D.R. et al [76] presented increased Bandwidth of 28% on a wedge shape and 25% on stepped substrate whereas rectangular resonator gives only 13% bandwidth. Ansari J.A. P. et al [4] developed a U- slot loaded patch with H-shaped parasitic elements and a bandwidth 3.66% (lower frequency) and 10.25% (higher frequency) and a resonance frequency(both) rely upon inversely on slot length and directly on slot width. Roy Aster A. et al [88] discussed a U, E and H shape patch antenna over the substrate. Bandwidth as compare to a conventional rectangular patch antenna (4.81%) is increased 28.71% .Chair Ricky et al [14] presented a half U-slot patch antenna with shorting pin attaining a bandwidth of 20 18 % and from the half E-shape patch antenna attaining a bandwidth of 25.2 %. SoniAbha et al [95] introduced two antennas; one is a simple Rectangular E shaped MSA whose bandwidth is 44.16 MHz (14.28 %) at 2.43 GHz. Lee Kai Fong et al [50] presented a comprehensive detail on the evolving of U slot antenna. It gives dual band operation at 2.0 GHz and 4.8 GHz with bandwidth is 3.5 % and 18.2% respectively. Deshmukh Amit A. and Ray K. P. [24] examined the U shape slot and half U shape slot cut in the patches with impedance bandwidth is 146 MHz.Khidre Ahmed et al [46] proposed the patch antenna operating at the TM02 fundamental mode in place of TM01 mode. Ojaroudi M. et al presented paper on stepped square radiating patch with two U-shaped slots, a notched ground with a T-shape sleeve and can also control bandwidth and band-notch frequency and the bandwidth is 140 % for 5.02 GHz-5.97 GHz. Patnaik A et al [73] constructed an omni-directional compact dual band antenna. Biswas Diptiman, Ramachandra V. [9] introduced a wraparound antenna placed on cylindrical shape surface and then it provide radial omni pattern with nulls at axis. Kumar Vipin and ShramaVipul [49] discussed GPS antenna for low loss dielectric material for wide band application .this antenna producing omnidirectional radiation pattern, which made good agreement. Aziz Masud A. et al [5] investigated a measurements and simulation for a folded slot conformal antenna array using two elements with coplanar waveguide. Wang Dian [25] proposed a novel technique for the miniaturization of a microstrip antenna by incorporating a irregular ground that provides inductive and capacitive loading ground and miniaturized area by 75.6%. Gitin, M. M., et al [34] presented the multi-resonant behavior of

Electronics And Communication Engineering Page2


a patch on a ferrite substrate yields a broad BW of about three octaves by changing the magnetic field.

1.3 Motivation of the ProjectFrequency reconfigurable antennas gain interest especially in future wireless communication systems due to flexibility in many applications. For that it is proposed to reconfigure an antenna with frequency switching capability for C-Band applications.

1.4 Aim of the Project

The aim of the project is to reconfigure a microstrip patch antenna that can be switched among seven different frequencies with a very good input match at all the resonant frequencies.

1.5 Objectives of the AntennaThe main objective of the project is to design a rectangular micro strip patch antenna with reconfigurable capability which operates at 5.8GHz frequency using HFSS simulation software. The proposed antenna is more useful for C-Band applications.

1.6 Organization of the thesis

This thesis is divided into 5 chapters and organized as follows:

Chapter 2 deals with the Introduction of project along with block diagram and explanation about each part.

Chapter 3 proposes the geometry of Reconfigurable Antenna with frequency switching capability for C-Band applications and its design analysis.

Chapter 4 deals with the obtained results of project.

Chapter 5 ends with the conclusion and references.



CHAPTER-2

OVERVIEW

2.1 INTRODUCTION

This Chapter deals with the Importance of the antenna and Introduction of project along with block diagram and explanation about each part.

2.2 ANTENNA:

An antenna is a type of transducer which converts electrical energy into radio waves (electromagnetic energy) and vice versa. An antenna is used with a radio transmitter or radio receiver. During transmission, transmitter supplies a current which is oscillating at radio frequency towards the terminals of antenna and the radiation of energy from the current in the form of electromagnetic waves is done by antenna. During reception, the antenna seizes some power of the electromagnetic wave and produces small amount of voltage at its terminals, which is further applied to the receiver for amplification.

Fig .2.1 Antenna

2.2.1 ROLE OF AN ANTENNA:

The main use of radio transmitters and radio receivers is to carry signals or data towards the systems which includes Wi-Fi, remote controlled instruments and point to point transmission links. All systems would require an antenna that is non-bulky and occupies less space. One such antenna is Microstrip Patch Antenna.

2.2.2 TYPES OF ANTENNA:

Classification of antennas can be based on:

1. Frequency and size: Antennas used for HF are different from the ones used for VHF, which in turn are different from antennas for microwave. The wavelength is different at different frequencies, so the antennas must be different in size to radiate signals at the correct wavelength.



2. Directivity: Antennas can be omnidirectional, sectorial or directive. Omnidirectional antennas radiate the same pattern all around the antenna in a complete 360 degrees. The most popular types of omnidirectional antennas are the Dipole-Type and the Ground Plane. Sectorial antennas radiate primarily in a specific area. The beam can be as wide as 180 degrees, or as narrow as 60 degrees. Directive antennas are antennas in which the beamwidth is much narrower than in sectorial antennas. They have the highest gain and are therefore used for long distance links. Types of directive antennas are:

● Yagi

● Biquad

● Horn

● patch antenna

● Parabolic Dish 3. Physical construction: Antennas can be constructed in many different ways, ranging

from simple wires to parabolic dishes, up to coffee cans.

2.3 ANTENNA PARAMETERS:

● Input impedance :For an efficient transfer of energy, the impedance of the radio, of the antenna

and of the transmission cable connecting them must be the same. Transceivers and their transmission lines are typically designed for 50Ω impedance. If the antenna has impedance different from 50Ω, then there is a mismatch and an impedance matching circuit is required.

Fig.2.2 impedances in an antenna

The input impedance of an antenna is given by



● Return loss :The return loss is another way of expressing mismatch. It is a logarithmic ratio

measured in dB that compares the power reflected by the antenna to the power that is fed into the antenna from the transmission line.

The return loss of an antenna is given by

Where VSWR stands for stands for Voltage Standing Wave Ratio.

● Bandwidth :The bandwidth of an antenna refers to the range of frequencies over which the

antenna can operate correctly. The antenna's bandwidth is the number of Hz for which the antenna will exhibit an SWR less than 2:1.Different types of antennas have different bandwidth limitations.

Antenna 3dB Beam width is the angle between the half-power of an antenna pattern or beam over which the relative power is at or above 50% of the peak power. Antenna beam width is also known as the half-power.

Formula:

Beamwidth = 70λ / D

where,

λ = Wavelength

D = Diameter

λ = 0.3 / frequency



Fig 2.3 BANDWIDTH OF ANTENNA

● Directivity and Gain :Directivity is the ability of an antenna to focus energy in a particular direction when

transmitting, or to receive energy better from a particular direction when receiving.

Fig 2.4 DIRECTIVITY OF VARIOUS ANTENNAS

The gain of an antenna in a given direction is the amount of energy radiated in that direction compared to the energy an isotropic antenna would radiate in the same direction when driven with the same input power.

An antenna normalized radiation pattern as a function of spherical coordinates is given as:

The directivity of an antenna is given as:



Fig 2.5 GAIN OF ANTENNA

● Radiation pattern :The radiation or antenna pattern describes the relative strength of the radiated field in

various directions from the antenna, at a constant distance. The radiation pattern is three-dimensional, but usually the measured radiation patterns are a two dimensional slice of the three-dimensional pattern, in the horizontal or vertical planes.

Fig 2.6 RADIATION PATTERN

Radiation pattern measurements are presented in either a rectangular or a polar format. Polar coordinate systems may be divided generally in two classes:

1. LINEAR2. LOGARITHMIC

● Linear coordinate system: In the linear coordinate system, the concentric circles are equally spaced, referenced

to 0 dB at the outer edge of the plot.



Fig 2.7 LINEAR COORDINATE SYSTEM

● Logarithmic polar coordinate system :

In the logarithmic polar coordinate system the concentric grid lines are spaced

periodically according to the logarithm of the voltage in the signal. Generally the 0 dB

reference for the outer edge of the chart is used.

Fig 2.8 POLAR COORDINATE SYSTEM

There are two kinds of radiation pattern: absolute and relative. Absolute radiation patterns are presented in absolute units of field strength or power. Relative radiation patterns are referenced in relative units of field strength or power.



● Beam width

An antenna's beamwidth is usually understood to mean the half-power beamwidth. The peak radiation intensity is found and then the points on either side of the peak which represent half the power of the peak intensity are located. The angular distance between the half power points is defined as the beamwidth. Half the power expressed in decibels is 3dB, so the half power beamwidth is sometimes referred to as the 3dB beamwidth.

Fig 2.9 BEAMWIDTH OF ANTENNA

● Side lobes :No antenna is able to radiate all the energy in one preferred direction. Some is

inevitably radiated in other directions. The peaks are referred to as side lobes, commonly specified in dB down from the main lobe.

● POLARIZATIONPolarization is defined as the orientation of the electric field of an electromagnetic

wave. Polarization is in general described by an ellipse. Two special cases of elliptical polarization are linear polarization and circular polarization.

In order to transfer maximum power between a transmit and a receive antenna, both antennas must have the same spatial orientation, the same polarization sense and the same axial ratio.

Fig 2.10 TYPES OF POLARIZATION



● Front-to-Back ratio :The front-to-back ratio that is the ratio of the maximum directivity of an antenna in forward direction to its directivity in the rearward direction. The front-to-back ratio is the difference in dB between the level of the maximum radiation, and the level of radiation in a direction180 degrees.

Fig 2.11 FRONT TO BACK RATIO

2.4 MICROSTRIP PATCH ANTENNA:

Nowadays, in mobile communication systems, the requirement of small sized antenna for miniaturisation purpose of mobile units has been increased. Hence, reduced size and enhanced bandwidth are the major considerations in micro strip antennas for practical applications. Therefore, study regarding small size and enhanced bandwidth of micro strip antenna has been greatly increased. In the past few years, great progress in the design of small sized micro strip antenna with dual and circular polarization, dual frequency, broadband and gain enhanced performance has been reported .

FIG 2.12 PATCH ANTENNA

Howell and Munson developed the first antenna which was practical antenna. Munson showed that the microstrip antenna was a practical antenna to be used in various antenna system problems by using it in missiles and rockets as a flush mounted low profile antenna. Microstrip antenna consists of a conducting patch on upper side of dielectric substrate and a ground plane on the lower side of dielectric substrate. The material of patch is copper or gold and the patch can have any shape such as rectangular and circular etc. On the dielectric substrate the feed line and the patch are photo etched.



Wireless technology provides less expensive alternative and a flexible way for communication. Antenna is one of the important elements of the wireless communications systems. According to the IEEE Standard Definitions, the antenna or aerial is defined as “a means of radiating or receiving radio waves". In other words, antennas act as an interface for electromagnetic energy, propagating between free space and guided medium.

Microstrip patch antennas are widely used in the microwave frequency region because of their simplicity and compatibility with printed-circuit technology, making them easy to manufacture either as stand-alone elements or as elements of arrays. The advantages of microstrip antennas make them suitable for various applications like, vehicle based satellite link antennas, global positioning systems (GPS), radar for missiles and telemetry and mobile handheld radios or communication devices. In its simplest form a microstrip patch antenna consists of a patch of metal, generally rectangular or circular (though other shapes are sometimes used) on top of a grounded substrate.

The commonly available shapes of patch antenna are rectangular, circular, dipole, triangular, square and elliptical with rectangular and circular shapes the most common

2.5 PLANAR TRANSMISSION LINES

Planar transmission lines are transmission lines with conductors, or in some cases dielectric strips, that are flat, ribbon-shaped lines. They are used to interconnect components on printed circuits and integrated circuits working at microwave frequencies because the planar format fits in well with the manufacturing methods for these components. Transmission lines are more than simple interconnections. With normal interconnections the propagation of the electromagnetic wave along the wire is fast enough to be considered instantaneous, and the voltage at each end of the wire can be considered identical.

Different formats that are present in the planar transmission lines are

1.Stripline:Stripline is a strip conductor embedded in a dielectric between two ground planes. It

is usually constructed as two sheets of dielectric clamped together with the stripline pattern on one side of one sheet. The main advantage of stripline over its principal rival, microstrip, is that transmission is purely in the TEM mode and is free of dispersion, at least, over the distances encountered in stripline applications. Stripline is capable of supporting TE and TM modes but these are not generally used. The main disadvantage is that it is not as easy as microstrip to incorporate discretecomponents. For any that are incorporated, cutouts have to be provided in the dielectric and they are not accessible once assembled.



FIG.2.13 STRIPLINE

2. Microstrip:Microstrip consists of a strip conductor on the top surface of a dielectric layer and a

ground plane on the bottom surface of the dielectric. The electromagnetic wavetravels partly in the dielectric and partly in the air above the conductor resulting in quasi-TEM transmission. Despite the drawbacks of the quasi-TEM mode, microstrip is often favoured for its easy compatibility with printed circuits. In any case, these effects are not so severe in a miniaturised circuit

Fig.2.14 Microstrip 3. Co Planar Waveguide(CPW):

Coplanar waveguide (CPW) has the return conductors on top of the substrate in the same plane as the main line, unlike stripline and microstrip where the return conductors are ground planes above or below the substrate. The return conductors are placed either side of the main line and made wide enough that they can be considered to extend to infinity. Like microstrip, CPW has quasi-TEM propagation.



FIG:2.15 CO PALANAR WAVEGUIDE

4. Slotline:A slotline is a slot cut in the metallisation on top of the substrate. It is the dual of

stripline, a dielectric line surrounded by conductor instead of a conducting line surrounded by dielectric.The dominant propagation mode is hybrid, quasi-TE with a small longitudinal component of electric field.

FIG.2.15 SLOTLINE

2.5.1 COAXIAL PROBE FEEDING:The Coaxial feed or probe feed is a very common technique used for feeding Microstrip patchantennas. The inner conductor of the coaxial connector extends through the dielectric and is soldered to the radiating patch, while the outer conductor is connected to the ground plane.

FIG.2.16 COAXIAL PROBE FEEDING

The coaxial feed or probe feed is a very commonly used to feed the patch located at the top surface of designed antenna. The configuration of a coaxial feed is shown in Figure. 2.16.



The inner conductor of the coaxial connector extends through the dielectric and is soldered to the radiating patch, while the outer conductor is connected to the ground plane.

❖ Advantages of Coaxial Probe Feed❖ Easy of fabrication

❖ Easy to match

❖ Low spurious radiation

❖ Disadvantages of Coaxial Probe Feed❖ Narrow bandwidth❖ Difficult to model specially for thick substrate❖ Possess inherent asymmetries which generate higher order modes which produce

cross-polarization radiation.

2.6 BLOCK DIAGRAM OF THE PROJECT

FIG 2.17. BLOCK DIAGRAM OF PROPOSED ANTENNA

The block diagram of reconfigurable patch antenna with frequency switching capability for C-Band application is shown in fig.2.17.

2.7 EXPLANATION ABOUT EACH PART

A reference rectangular microstrip patch antenna is designed at a resonant frequency of 5.8 GHz. The width (W) and length (L) of the patch at a resonant frequency is calculated from standard equations given in Balanis [6] and values are 20.39 mm and 17.98 mm, respectively. The relative dielectric constant and height of the used substrate is 2.2, 0.508 mm, respectively. Loss tangent of the substrate is 0.0009. The complete size of the ground plane is 50 × 50mm2. Simple bias circuit is designed to bias the PIN diodes. When we connect a stub to a reference patch, frequency may increase or decrease, it depends on the



parameters such as length and width of the stub and position of the switches. Parametric study is performed to get good impedance match at all the resonances. To reconfigure the frequencies, an additional patch with width same as patch and length 3 mm is connected by three PIN diodes as shown in Fig. 2.17.The equivalent circuit of PIN diodes is as shown inFig.2.18.

Fig 2.18. Equivalent Circuit of PIN DiodeDC block capacitor is connected in between reference patch and D1 to bias the diode independently. For the designing of frequency reconfigurable antenna, we start with conventional microstrip patch antenna and calculate the length and width of the patch and lambda/4 transformer using standard rectangular microstrip antenna design equations. To get other resonance, we connect an additional patch of same width as reference antenna but different length. In this paper, frequency tuning is discrete by turning PIN diodes ON or OFF.

2.8. CONCLUSIONSThe importance and role of antenna and the introduction to the project along with block diagram has been explained in this chapter.The design analysis of the proposed antenna is described in the next chapter.



CHAPTER 3

DESIGN ANALYSIS

3.1 INTRODUCTION TO HFSS:

The name HFSS stands for High Frequency Structural Simulator. HFSS is a high-performance full-wave electromagnetic (EM) field simulator for arbitrary 3D volumetric passive device modelling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates simulation, visualization, solid modelling, and automation in an easy-to-learn environment where solutions to 3D EM problems are quickly and accurately obtained. ANSYS HFSS employs the Finite Element Method(FEM), adaptive meshing, and brilliant graphics to give unparalleled performance and insight to all of 3D EM problems.

HFSS is an interactive simulation system whose basic mesh element is a tetrahedron. This allows to solve any arbitrary 3D geometry, especially those with complex curves and shapes, in a fraction of the time it would take using other techniques. Ansoft pioneered the use of the Finite Element Method (FEM) for EM simulation by developing/implementing technologies such as tangential vector finite elements, adaptive meshing, and Adaptive Lanczos-Pade Sweep.

The ANSYS HFSS Desktop provides an intuitive, easy-to-use interface for developing passive RF device models. Creating designs, involves the following:

1. Parametric Model Generation – creating the geometry, Parametric Model Generation boundaries and excitations

2. Analysis Setup – defining solution setup and frequency sweep Analysis Setup

3. Results – creating 2D reports and field plots Results

4. Solve Loop - the solution process is fully automated Solve Loop.

3.1.1APPLICATION OF HFSS:

Today, HFSS continues to lead the industry with innovations such as Modes-to-Nodes and Full-Wave Spice. ANSYS HFSS has evolved over a period of years with input from many users and industries. In industry, ANSYS HFSS is the tool of choice for high-productivity research, development, and virtual prototyping. HFSS finds applications in wide range of areas. ANSYS HFSS can be used to calculate parameters such as S-Parameters, Resonant Frequency, and Fields.

Some of applications of HFSS are :

1. Package Modelling–BGA, QFP, Flip-Chip2. PCB Board Modelling– Power/Ground planes, Mesh Grid Grounds, Backplanes

Silicon/GaAs-Spiral Inductors, Transformers3. EMC/EMI –Shield Enclosures, Coupling, Near-or Far-Field Radiation



4. Antennas/Mobile Communications–Patches, Dipoles, Horns, Conformal Cell Phone Antennas, Quadrafilar Helix, Specific Absorption Rate(SAR), Infinite Arrays, Radar Cross Section(RCS),Frequency Selective Surfaces(FSS)

5. Connectors–Coax, SFP/XFP, Backplane, Transitions 6. Waveguide–Filters, Resonators, Transitions, Couplers 7. Filters–Cavity Filters, Microstrip, Dielectric.8. Microwave transitions9. Waveguide components10. Three-dimensional discontinuities11. Passive circuit elements

3.1.2 HFSS FEATURES:

HFSS has many significant features which attracts the user. Some of the features of HFSS are:

1. Computes s-parameters and full-wave fields for arbitrarily-shaped 3D passive structures.

2. Powerful drawing capabilities to simplify design entry.

3. Field solving engine with accuracy-driven adaptive solutions.

4. Powerful post-processor for unprecedented insight into electrical performance.

5. Advanced materials.

6. Model Library-including spiral inductors.

7. Model half, quarter, or octet symmetry.

8. Calculate far-field patterns.

9. Wideband fast frequency sweep .

10. Create parameterized cross section models- 2D models .

3.2 DESIGN OF PROPOSED ANTENNA

3.2.1 THEORETICAL ANALYSIS



Fig 3.1 Geometrical layout of the proposed antennaThe geometrical layout of the proposed Reconfigurable antenna is shown in Fig.3.1.By properly selecting the antenna’s geometric parameters numerically and experimentally, reduction of antenna size is also obtained. 3.3 SIMULATION OF THE PROPOSED ANTENNA

• Launching Ansoft HFSS

– To access Ansoft HFSS, click the MicrosoftStartbutton, selectPrograms, and select theAnsoft, HFSS 17.0 programgroup. Click HFSS 17.0.

From the Project Manager window. Right-Click the project file and select Save As from the sub menu.



3- Working with geometries

To begin working with geometries.

- you must insert an HFSS design. Right-Click the project file and select Insert>Insert HFSS Design from the menu.

- Or click on the toolbars.

• Opening a New Project

– In HFSS Desktop, clickon the Standard toolbar, orselect the

Menu item File > New.



– From the Project menu, selectInsert HFSS Design.

Fig 3.2 Opening a new project

• Set Solution Type

– Select the menu itemHFSS > Solution Type

• Choose Driven Modal

• Click the OK button



• Set Model Units

– Select the menu itemModeler > Units

• Select Units: mm• Click the OK button

4- Drawing the Substrate:

We will start to by creating the substrate using the Draw Rectangle button from the toolbar.



By default the properties dialog will appear after you have finished drawing an object.

The position and size of objects can be modified from the dialog.

Now, design the antenna with respect to the calculated lengths to obtain the appropriate shape.



• Validation check

Fig.3.3 Validation check

CHAPTER 4

SIMULATION RESULTS AND DISCUSSIONS

4.1 INTRODUCTION

This chapter deals with the simulated results of the proposed antenna using HFSS ANSYS Tool and the obtained results are tabulated.

4.2 RESULTS

A. RETURN LOSSThe simulated return loss coefficients for the substrate thickness t=0.508mm and εr=2.2 is

shown in Fig below. The graph in Fig 4.1 shows the simulated reflection coefficient values of the monopole antenna. The simulated results shows impedance bandwidth ranges 3.09 – 3.29



GHz and 6.41 – 6.77 GHz centered at 3.18GHz and 6.6 GHz respectively with return loss of -38.88dB and -40.40dB respectively.

FIG 4.1 RETURN LOSS

FIG 4.2 RETURN LOSS

B. RADIATION PATTERN WITH ELEVATION AND AZIMUTH ANGLES

The far-field radiation patterns at the operating frequency for the constructed prototype of the proposed antenna are also examined.



FIG 4.3. 2D AZIMUTHAL PATTERN FOR DIODES OFF

FIG 4.4. 2D AZIMUTHAL PATTERN FOR DIODES OFF



FIG 4.5. 2D ELEVATION PATTERN FOR DIODES OFF

FIG 4.6. 2D ELEVATION PATTERN FOR DIODES ON

C. SMITH CHART

The Fig 3.7 shows the Smith chart for the antenna. It is clear from the figure that at resonance almost proper impedance matching occurs. At resonance the impedance of the proposed antenna is 47Ω which is close to ideal value 50 Ω.



FIG 4.7 SMITH CHART OF THE PROPOSED ANTENNA

FIG 4.8 SMITH CHART OF THE PROPOSED ANTENNA

D. AXIAL RATIOThe Fig 4.9,4.10 and 4.11,4.12 shows simulated axial ratio v/s frequency for the cases when all the diodes are ON and when all the diodes are OFF provided azimuth angle and elevation angle respectively.



FIG 4.9 AXIAL RATIO

FIG 4.10 AXIAL RATIO





The 3D radiation patterns at 5.8GHz are shown in Fig 5.4.

FIG 4.13 3D POLAR PLOT



FIG 4.14 GAIN

Simulated Current distributions for the proposed antenna at 5.8GHz are shown in the Fig 4.15,4.16

FIG 4.15 MAGNITUDE_EFIG 4.16 VECTOR_E

From the Fig 4.15 it is clearly observed that strong surface currents are distributed over the feed line and over the patch surface, as shown in Fig 4.16 strong surface currents are distributed over the feed line and over middle section of strip and lower ground plate. The above figures justify the use of defected ground structure technique.

Simulated VSWR plots is shown in Fig 4.17,4.18.

FIG 4.17 SIMULATED VSWR



FIG 4.18 SIMULATED VSWR

The diode conditions and their respective reconfigured frequencies of the proposed antenna can be summarized as shown in the table below.

Table 4.1.Summary of the results

D1 D2 D3

Frequency Simulated

(GHz)

Frequency Measured

(GHz)

OFF OFF OFF 5.78 7.00

OFF OFF ON 5.85 6.23

ON ON OFF 5.9 3.37

OFF ON ON 6.11 6.24

OFF ON OFF 6.2 2.48

ON OFF ON 6.55 6.6

ON ON ON 7.32 6.6

4.3 CONCLUSIONThe obtained reults of the proposed reconfigurable antenna are verified and the results are discussed and tabulated in this chapter. Next chapter deals with the conclusions of the proposed antenna and references.



CHAPTER 5 CONCLUSION

Proposed reconfigurable antenna is designed, simulated and measured. The designed reconfigurable antenna resonates at seven different frequencies. The measured values of the frequencies are 7.00,6.23, 3.37, 6.24, 2.48, 6.56 and 6.6GHz. A good impedance match (S11 < -10 dB) is obtained at all the frequencies. Radiation pattern is broadside to the antenna and cross-polarization levels in both the planes are less than -18 dB. Proposed antenna has advantages of being simple in design and ease to fabricate can be suitable for c-band applications. PIN diodes can be replaced by varactor to make switching continuous by applying proper bias to the diodes



REFERENCES

[1] Manoj S. Parihar, A. Basu and S. K. Koul, “Novel Tri-state Dual band Frequency Reconfigurable Antenna,” International Symp. on antenna and propag. (ISAP), Taipei, Taiwan, 27-30 Oct. 2008.[2] R. K. Singh, A. Basu, S. K. Koul, “Asymmetric coupled polarization switchable oscillating active integrated antenna,” Asia-Pacific Microwave Conf. (APMC), New Delhi, 2016 pp. 1-4.[3] S. Nikolaou, R. Bairavasubramanian, C. Lugo, I. Carrasquillo, D. C. Thompson, G. E. Ponchak, J. Papapolymerou, and M. M. Tentzeris, “Pattern and frequency reconfigurable annular slot antenna using PIN diodes,” IEEE Trans. Antennas Propag., vol. 54, no. 2, pp. 439–448, Feb. 2006.[4] R. K. Singh, A. Basu and S. K. Koul, "Efficient null broadening and steering using slot antenna array for radar applications," 2016 Asia- Pacific Microwave Conference (APMC), New Delhi, 2016, pp. 1-4.[5] R. K. Singh, A. Basu and S. K. Koul, "Novel high gain polarization switchable rectangular slot antenna for L-band applications," 2017 11th European Conference on Antennas and Propagation (EUCAP), Paris, 2017, pp. 3820-3824.[6] C. A. Balanis, Antenna theory - analysis and design, 3rd ed., NY, USA: Wiley, 2005, ch. 14, pp. 816–823.


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1.Stripline: · Web view2019-07-21 · In recent years, the demand for antennas with multiband operations has been increased rapidly since such antennas play a major role in combining