CAPSTONE PROJECT (PART –I) REPORT

(Project Term August-December, 2012)

PHASED ARRAY RADAR SIMULATION USING ANSYSTM HFSS

(COMMUNICATION)

Submitted by

MANISHA PODDAR Registration Number: 10906591

ANSHUMAN DWIVEDI Registration Number: 10906299

NAVDEEP KALSOTRA Registration Number: 10900096

BHAVANA MAHAVAR Registration Number: 10904626

MANJU KUMARI Registration Number: 10908339

Project Group Number 6

Under the Guidance of

Mr. B. ARUN KUMAR

(Asst. Professor)

Discipline of Electronics and Communication Engineering

Lovely Professional University, Phagwara

August to December, 2012

DECLARATION

We hereby declare that the project work entitled PHASED ARRAY RADAR SIMULATION

USING ANSYSTM

HFSS is an authentic record of our own work carried out as requirements

of Capstone Project (Part-I) for the award of degree of B.Tech in Electronics and

Communication Engineering from Lovely Professional University, Phagwara, under the

guidance of Mr. B. ARUN KUMAR, during August to December, 2012).

Project Group Number: 6

Name of the student 1: MANISHA PODDAR

Registration Number: 10906591

Name of the student 2: ANSHUMAN DWIVEDI

Registration Number: 10906299

Name of the student 3: NAVDEEP KALSOTRA

Registration Number: 10900096

Name of the student 4: BHAVANA MAHAVAR

RegistrationNumber: 10904626

Name of the student 5: MANJU KUMARI

Registration Number: 10908339

(Signature of Student 1)

(Signature of Student 2)

(Signature of Student 3)

(Signature of Student 4)

(Signature of Student 5)

CERTIFICATE

This is to certify that the declaration statement made by this group of students is correct

to the best of my knowledge and belief. The Capstone Project Proposal based on the

technology / tool learnt is fit for the submission and partial fulfillment of the conditions for

the award of B.Tech in Electronics and Communication Engineering from Lovely

Professional University, Phagwara.

Name : B. Arun Kumar

U.ID : 16518

Designation :Asst. Proffesor

Signature of Faculty Mentor

CONTENTS

1) ACKNOWLEDGEMENT

2) CHAPTER 1

(1) INTRODUCTION

3) CHAPTER 2

(1) REVIEW OF LITERATURE

(2) SCOPE OF THE STUDY

4) CHAPTER 3

(1) OBJECTIVES OF THE STUDY

(2) RESEARCH METHODOLOGY

5) CHAPTER 4

(1) COMPLETE WORK PLAN WITH TIMELINES

(2) EXPERIMENTAL WORK DONE

(3) SUMMARY

(4) REFERENCES

(5) APPROVED PROJECT TOPIC FORMAT

ACKNOWLEDGEMENT

We are sincerely thankful to the Department of Electronics & Communication

Engineering, Lovely Professional University, Punjab, for having provided us with this

opportunity, as a part of the degree course, to come face to face with live projects.

We would like to extend our deepest gratitude to, my project guide and mentor, Mr. B.

Arun Kumar, Asst. Professor, Dept. of ECE, Lovely Professional University for his

guidance and encouragement in carrying out our project work on Phased Array Radar

Simulation Using AnsysTM HFSS.

We are highly thankful to the officials and technical staff of the Dept. of ECE, Lovely

Professional University for providing us with the vital and valuable information about the

different facets of a live project and various other fields.

Name of the student 1: MANISHA PODDAR

Registration Number: 10906591

Name of the student 2: ANSHUMAN DWIVEDI

Registration Number: 10906299

Name of the student 3: NAVDEEP KALSOTRA

Registration Number: 10900096

Name of the student 4: BHAVANA MAHAVAR

RegistrationNumber: 10904626

Name of the student 5: MANJU KUMARI

Registration Number: 10908339

Chapter 1

INTRODUCTION

ANSYSTM HFSS

ANSYSTM HFSS software is the industry-standard simulation tool for 3-D full-wave

electromagnetic field simulation and is essential for the design of high-frequency and

high-speed component design. HFSS offers multiple state-of the-art solver technologies

based on either the proven finite element method or the well-established integral

equation method. One can select the appropriate solver for the type of simulation one is

performing.

The accuracy, capacity, and performance of HFSS is reliable to design high-speed

components including on-chip embedded passives, IC packages, PCB interconnects

and high-frequency components such as antennas, RF/microwave components and

biomedical devices. With HFSS, engineers can extract scattering matrix parameters (S,

Y, Z parameters), visualize 3-D electromagnetic fields (near- and far-field) and generate

ANSYS Full-Wave SPICE models that link to circuit simulations. Signal integrity

engineers use HFSS within established EDA design flows to evaluate signal quality,

including transmission path losses, reflection loss due to impedance mismatches,

parasitic coupling and radiation.

Electric field distribution with a far field radiation pattern simulated by the new finite

antenna array capability in HFSS

Each HFSS solver is based on a powerful, automated solution process where you are

only required to specify geometry, material properties and the desired output. From

there HFSS will automatically generate an appropriate, efficient and accurate mesh for

solving the problem using the selected solution technology. With HFSS the physics

defines the mesh; the mesh does not define the physics. HFSS is a commercial finite

element method solver for electromagnetic structures from Ansys Corporation. The

acronym originally stood for high frequency structural simulator. It is one of several

commercial tools used for antenna design, and the design of complex RF electronic

circuit elements including filters, transmission lines, and packaging. It was originally

developed by Professor Zoltan Cendes and his students at Carnegie Mellon University.

Prof. Cendes and his brother Nicholas Csendes founded Ansoft and sold HFSS stand-

alone under a 1989 marketing relationship with Hewlett-Packard, and bundled into

Ansoft products. After various business relationships over the period 1996-2006, H-P

(which became Agilent EEsof EDA division) and Ansoft went their separate ways :

Agilent with the critically acclaimed [3] FEM Element and Ansoft with their HFSS

products, respectively. Ansoft was later acquired by AnsysTM

PHASED ARRAY RADAR

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.

In the figure 1 (left) both radiating elements are fed with the same phase. The signal is

amplified by constructive interference in the main direction. The beam sharpness is

improved by the destructive interference.

In the figure above the signal is emitted by the lower radiating element with a phase

shift of 22 degrees earlier than of the upper radiating element. Because of this the main

direction of the emitted sum-signal is moved upwards.

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 shifter giving 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). With the sine

theorem the necessary phase moving can be calculated.

The following figure graphically shows the matrix of radiating elements. Arbitrary

antenna constructions can be used as a spotlight in an antenna field. For a phased

array antenna is decisive that the single radiating elements are steered for with a

regular phase moving and the main direction of the beam therefore is changed. E.g. the

antenna of the RRP 117 consists of 1584 radiating elements arranged in an analogue

beamforming architecture. More sophisticated radar sets use the benefits of a Digital

Beamforming architecture.

Advantages:

High gain 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 controlarbitrarily modes of

surveillance and tracking

Free eligible Dwell Time

Multifunction operation by emitting several beams simultaneously

Fault of single components reduces the capability and beam sharpness, but the

system remains operational

Disadvantages:

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

MATLAB®

MATLAB® is a high-level language and interactive environment for numerical

computation, visualization, and programming. Using MATLAB, you can analyze data,

develop algorithms, and create models and applications. The language, tools, and built-

in math functions enable you to explore multiple approaches and reach a solution faster

than with spreadsheets or traditional programming languages, such as C/C++ or Java™.

One can use MATLAB for a range of applications, including signal processing and

communications, image and video processing, control systems, test and measurement,

computational finance, and computational biology. More than a million engineers and

scientists in industry and academia use MATLAB, the language of technical computing.

THE PROJECT

Phased array antennas are common in communications and radar and offer the benefit

of far-field beam shaping and steering for specific, agile operational conditions. They

are especially useful in modern adaptive radar systems where there is a trend toward

active phased arrays and more advanced space-time adaptive signal processing.

The MathWorks provides simulation tools that are used broadly in the communications

industry for mathematical algorithm development, digital signal processing (DSP),

communication system analysis, and antenna design. ANSYSTM provides simulation

tools that provide full-wave 3D electromagnetic field simulation coupled to linear and

non-linear circuit simulation. The combination provides very broad coverage of

applications needed for modern communications and radar.

In this project, we discuss how Matlab from The MathWorks and AnsysTM HFSS can be

used together to simulate phased array antennas. A new Phased Array Toolbox for

Matlab enables engineers and scientists to simulate essential applications for phased

array antenna systems. Details of electromagnetic coupling at the physics level is

simulated in HFSS and circuit tools to capture effects of mutual coupling and nonlinear

behavior of power amplifiers and other circuit components

Chapter 2

REVIEW OF LITERATURE

ANTENNA THEORY

TYPES OF ANTENNA

Microstrip antenna

In telecommunication, there are several types of microstrip antennas (also known as

printed antennas) the most common of which is the microstrip patch antenna or patch

antenna.

Patch antenna

A patch antenna is a narrowband, wide-beam antenna fabricated by etching the

antenna element pattern in metal trace bonded to an insulating dielectric substrate,

such as a printed circuit board, with a continuous metal layer bonded to the opposite

side of the substrate which forms a ground plane. Common microstrip antenna shapes

are square, rectangular, circular and elliptical, but any continuous shape is possible.

Some patch antennas do not use a dielectric substrate and instead made of a metal

patch mounted above a ground plane using dielectric spacers; the resulting structure is

less rugged but has a wider bandwidth. Because such antennas have a very low profile,

are mechanically rugged and can be shaped to conform to the curving skin of a vehicle,

they are often mounted on the exterior of aircraft and spacecraft, or are incorporated

into mobile radio communications devices.

All of the parameters in a rectangular patch antenna design (L, W, h, permittivity) control

the properties of the antenna. As such, this page gives a general idea of how the

parameters affect performance, in order to understand the design process.

First, the length of the patch L controls the resonant frequency as seen here. This is

true in general, even for more complicated microstrip antennas that weave around - the

length of the longest path on the microstrip controls the lowest frequency of operation.

Equation (1) below gives the relationship between the resonant frequency and the patch

length:

(1)

Second, the width W controls the input impedance and the radiation pattern (see the

radiation equations here). The wider the patch becomes the lower the input impedance

is.

The permittivity of the substrate controls the fringing fields - lower permittivities have

wider fringes and therefore better radiation. Decreasing the permittivity also increases

the antenna's bandwidth. The efficiency is also increased with a lower value for the

permittivity. The impedance of the antenna increases with higher permittivities.

Higher values of permittivity allow a "shrinking" of the patch antenna. Particularly in cell

phones, the designers are given very little space and want the antenna to be a half-

wavelength long. One technique is to use a substrate with a very high permittivity.

Equation (1) above can be solved for L to illustrate this:

Hence, if the permittivity is increased by a factor of 4, the length required decreases by

a factor of 2. Using higher values for permittivity is frequently exploited in antenna

miniaturization.

The height of the substrate h also controls the bandwidth - increasing the height

increases the bandwidth. The fact that increasing the height of a patch antenna

increases its bandwidth can be understood by recalling the general rule that "an

antenna occupying more space in a spherical volume will have a wider bandwidth". This

is the same principle that applies when noting that increasing the thickness of a dipole

antenna increases its bandwidth. Increasing the height also increases the efficiency of

the antenna. Increasing the height does induce surface waves that travel within the

substrate (which is undesired radiation and may couple to other components).

The following equation roughly describes how the bandwidth scales with these

parameters:

Advantages

Microstrip antennas are relatively inexpensive to manufacture and design because of

the simple 2-dimensional physical geometry. They are usually employed at UHF and

higher frequencies because the size of the antenna is directly tied to the wavelength at

the resonant frequency. A single patch antenna provides a maximum directive gain of

around 6-9 dBi. It is relatively easy to print an array of patches on a single (large)

substrate using lithographic techniques. Patch arrays can provide much higher gains

than a single patch at little additional cost; matching and phase adjustment can be

performed with printed microstrip feed structures, again in the same operations that

form the radiating patches. The ability to create high gain arrays in a low-profile antenna

is one reason that patch arrays are common on airplanes and in other military

applications.

Such an array of patch antennas is an easy way to make a phased array of antennas

with dynamic beam forming ability which is our motive in this project.

An advantage inherent to patch antennas is the ability to have polarization diversity.

Patch antennas can easily be designed to have vertical, horizontal, right hand circular

(RHCP) or left hand circular (LHCP) polarizations, using multiple feed points, or a single

feedpoint with asymmetric patch structures. This unique property allows patch antennas

to be used in many types of communications links that may have varied requirements.

Rectangular patch

The most commonly employed microstrip antenna is a rectangular patch. The

rectangular patch antenna is approximately a one-half wavelength long section of

rectangular microstrip transmission line. When air is the antenna substrate, the length of

the rectangular microstrip antenna is approximately one-half of a free-space

wavelength. Since the antenna is loaded with a dielectric as its substrate, the length of

the antenna decreases as the relative dielectric constant of the substrate increases. The

resonant length of the antenna is slightly shorter because of the extended electric

"fringing fields" which increase the electrical length of the antenna slightly. An early

model of the microstrip antenna is a section of microstrip transmission line with

equivalent loads on either end to represent the radiation loss.

Specifications

The dielectric loading of a microstrip antenna affects both its radiation pattern and

impedance bandwidth. As the dielectric constant of the substrate increases, the antenna

bandwidth decreases which increases the Q factor of the antenna and therefore

decreases the impedance bandwidth. This relationship did not immediately follow when

using the transmission line model of the antenna, but is apparent when using the cavity

model which was introduced in the late 1970s by Lo et al.[3] The radiation from a

rectangular microstrip antenna may be understood as a pair of equivalent slots. These

slots act as an array and have the highest directivity when the antenna has an air

dielectric and decreases as the antenna is loaded by material with increasing relative

dielectric constant.

The half-wave rectangular microstrip antenna has a virtual shorting plane along its

center. This may be replaced with a physical shorting plane to create a quarter-

wavelength microstrip antenna. This is sometimes called a half-patch. The antenna only

has a single radiation edge (equivalent slot) which lowers the directivity/gain of the

antenna. The impedance bandwidth is slightly lower than a half-wavelength full patch as

the coupling between radiating edges has been eliminated.

Other types

Another type of patch antenna is the Planar Inverted F Antenna (PIFA) common in

cellular phones with built-in antennas.(The Planar Inverted-F antenna (PIFA) is

increasingly used in the mobile phone market. The antenna is resonant at a quarter-

wavelength (thus reducing the required space needed on the phone), and also typically

has good SAR properties. This antenna resembles an inverted F, which explains the

PIFA name. The Planar Inverted-F Antenna is popular because it has a low profile and

an omnidirectional pattern. The PIFA is shown from a side view in Figure 4.) [4] These

antennas are derived from a quarter-wave half-patch antenna. The shorting plane of the

half-patch is reduced in length which decreases the resonance frequency. Often PIFA

antennas have multiple branches to resonate at the various cellular bands. On some

phones, grounded parasitic elements are used to enhance the radiation bandwidth

characteristics.

The Folded Inverted Conformal Antenna (FICA) has some advantages with respect to

the PIFA, because it allows a better volume reuse.

WHAT IS RADAR?

The following figure shows the operating principle of a primary radar set. The radar

antenna illuminates the target with a microwave signal, which is then reflected and

picked up by a receiving device. The electrical signal picked up by the receiving

antenna is called echo or return. The radar signal is generated by a powerful transmitter

and received by a highly sensitive receiver.

PROBLEM STATEMENT

To develop a design for phased array radar on HFSS and MATLAB.

Chapter 3

OBJECTIVE

To obtain radiation patterns and polar plots and graphs for a phased array antenna from

its lumped port after simulating it on HFSS with proper calculations.

RESEARCH METHODOLOGY

The inset-fed microstrip antenna provides a method of impedance control with a planar

feed configuration. For a probe-fed rectangular microstrip antenna, the relationship

between the resonant input resistance and feed position has been theoretically and

experimentally shown to follow a cos2 variation. For an inset-fed patch, a higher-order

cosine function fit the experimental data better. A more recent study proposed a

modified shifted sin2 form that well characterizes probe-fed patches with a notch. The

goal of this paper is to study the dependence of resonant input resistance of the inset-

fed patch on the notch and feed-line geometry.

Patch Geometries

Figure 1 shows the geometry of an inset-fed rectangular patch. The normalized inset-

dimension is defined as xn = xf / (L / 2). The thickness of the substrate h is 1.27 mm. The

input impedance is that obtained by de-embedding along the line to the point where the

feed line contacts the patch. Resonance is defined where the input resistance is at its

maximum (Rin).

Three patch geometries with different substrate εr (as shown in Figure 1) are simulated

using both AnsysTM HFSS and Designer. AnsysTM HFSS is a full-wave finite element

simulator, and AnsysTM Designer features a planar method-of moments simulator.

Figure below shows the input resistance Rin versus normalized inset-depth xn,

comparing between simulated results and measurements. The simulation results show

good agreement with the measurements.

INSET-FED PATCHES WITH DIFFERENT FEED LINES AND NOTCH WIDTHS

A proposed CAD formula for the resonant input resistance (de-embedded along the

microstrip line to the contact point) is:

Where A and B are constants that can be obtained by a least-square method, matching

to simulated data. Different feed lines were first used to determine whether Wf affects

the resonant input resistance. Figure 3(a) plots Rin versus xn for the patch on an air

substrate. The notch width S was 1.854 cm (3×Wf for a 50 Ω line), and two feed lines

with 50 Ω and 100 Ω impedances were used to feed the patch. It may be noticed that

different line widths do not significantly affect the results. It may also be observed that

the results from (1) (solid line in the figure) agree quite well with the simulations, using

the A and B values shown (obtained from a least-squares solution).

Patches with εr = 10.2 and S = 0.62 cm (5×Wf for a 50 Ω line) were investigated next. A

50 Ω and a 25 Ω microstrip line were used to confirm that once again Wf does not

significantly affect the results.

TRANSMISSION LINE MODEL

An equivalent circuit model for the proposed antenna is developed. This model is

capable of predicting the slot radiation conductance and the antenna input impedance

near resonance. This approach provides very helpful insight as to how this antenna and

its feed network operate. This model is also needed to find a proper matching network

for the antenna.

The model consists of breaking up the antenna into three areas a, b and c. Let us

consider each part as being an antenna which finishes on the level of its ends by a

length L due to the slot radiation and a resistance in series representing the value of this

resistance in the antenna extremity. The improved model consist of neglecting the

radiations slots between the feed line and the areas b and c and replace the resistances

in series by their true values due only to the areas b and c. Therefore resistances will be

Rinb and Rinc instead of only one resistance Rin. The various values of the model are

given as follows:

The input resistance is given by:

Where G1 and B1 are given by

The conductance of a single slot can also be obtained by using the expression field

derivative from model cavity. In general, the conductance is defined by:

Radiated power using electric field:

Self-conductance:

Integral I1 :

Slot lengths:

Resonant frequencies:

Chapter 4

WORK PLAN

WORK DONE and TIMELINE

September

• 20th Sept.: Allotment of project .

• 28th Sept.: Commencement of project. Collection of data

• 30th Sept.: Begun to study about Antennas and Radar.

• 30th Sept.: Study about Phased array radar.

October

• 12th Oct.: Introduction to Ansys HFSS.

• 16th Oct.: Basic tutorials on HFSS.

• 18th Oct.: Designing of antennas using hfss

• 25th Oct.: Formulation of codes begins

November

• 1st Nov.: Calculations for the Phased Array Radar.

• 3rd Nov.: Compilation of matlab codes.

• 15th Nov.: Completion of Simulation and Codes.

• 16th Nov.: Comencement of report making.

EXPERIMENTAL WORK

HFSS DESIGN

SUMMARY

ANSYSTM HFSS software is the industry-standard simulation tool for 3-D full-wave

electromagnetic field simulation and is essential for the design of high-frequency and

high-speed component design. HFSS offers multiple state-of the-art solver technologies

based on either the proven finite element method or the well-established integral

equation method. One can select the appropriate solver for the type of simulation one is

performing.

In telecommunication, there are several types of microstrip antennas (also known as

printed antennas) the most common of which is the microstrip patch antenna or patch

antenna.

Using an array of phased array antennas a radar is simulated on HFSS and using

MATLAB.

The expected plots define its behavior.

The design can be further implemented in real life strategically, weather forecast,

security purpose, traffic control etc.

REFERENCES AND BIBLIOGRAPHY

[1] Microstrip Antennas: The Analysis and Design of Microstrip Antennas and

Arrays, David M. Pozar and Daniel H. Schaubert, Editors, Wiley/IEEE Press,

1995.

[2] Constantine A. Balanis; Antenna Theory, Analysis and Design, John Wiley &

Sons Inc. 2ndedition. 1997.

[3] Comparative Analysis of Exponentially Shaped Microstrip-Fed Planar Monopole

Antenna With and Without Notch M. Venkata Narayana, I.Govadhani, K.P.Sai

Kumar, K. Pushpa Rupavathi.

[4] A Matin, M.P Saha, H. M. Hasan “Design of Broadband Patch Antenna for

WiMAX and WLAN” ICMMT 2010 Proceedings, pp. 1-3

[5] F. Yang, X. X. Zhang, X. Ye, and Y. Rahmat-Samii, “Wide-band Eshaped patch

antennas for wireless communications,” IEEE Trans. Antennas Propag., vol. 49,

no. 7, pp. 1094–1100, Jul. 2001.

[6] M. Sanad, “Double C-patch antennas having different aperture shapes,” in Proc.

IEEE AP-S Symp., Newport Beach, CA, Jun. 1995, pp. 2116–2119.

[7] Shackelford, A.K., Lee, K.F., and Luk, K.M.: ‘Design of small-size widebandwidth

microstrip-patch antennas’, IEEE Antennas Propag. Mag., 2003, AP-45

[8] H. F. AbuTarboush, H. S. Al-Raweshidy, and R. Nilavalan, “Triple band double

U-slots patch antenna for WiMAx mobile applications,” in Proc. Of APCC, Tokyo,

Feb. 2008, pp. 1-3.

[9] Waterhouse, R.B.: ‘Broadband stacked shorted patch’, Electron. Lett. 1999, 35,

(2), pp. 98–100

[10] Guo, Y.X., Luk, K.M., and Lee, K.F.: ‘L-probe proximity-fed shortcircuited

patch antennas’, Electron.Lett., 1999, 35, (24), pp. 2069–2070

[11] K.L. Lau and K.M. Luk ” Wideband folded L-slot shorted-patch Antenna”

ELECTRONICS LETTERS 29th September 2005 Vol. 41 No. 20

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4244-2802-1/09/$25.00 ©2009 IEEE, pp.2722-2725

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[14] IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5,

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[15] http://www.microwavejournal.com/articles/12494-phased-array-antenna-

design-using-matlab-and-hfss