Microstrip patch antenna for wimax applications

DESIGN OF MICROSTRIP PATCH
ANTENNA FOR IEEE 802.16-2004
APPLICATIONS
EHAB ESAM DAWOOD
Department Of Electronic
Faculty of Electronics Engineering
University of Mosul
Contact me:
aburaneem3@gmail.com

 The IEEE 802 LAN/MAN Standards Committee develops
Local Area Network standards and Metropolitan Area
Network standards.
 The most widely used standards are for the Ethernet
family, Token Ring, Wireless LAN, Wireless PAN, Wireless
MAN, Bridging and Virtual Bridged LANs. An individual
Working Group provides the focus for each area.
 The number 802 was simply the next free number IEEE
could assign, though “802” is sometimes associated with
the date the first meeting was held in February 1980.
IEEE 802

 wireless communication means to transfer information over
long or short distance without using any wires
 An antenna is defined a usually metallic device (as a rod
or wire) for radiating or receiving radio waves.
 the antenna is the transitional structure between free-
space and a guiding device
 it is used to transport electromagnetic energy from the
transmitting source to the antenna or from the antenna to
the receiver, the antenna can be in a form of microstrip.
INTRODUCTION

 Microstrip: is a type of electrical transmission line which can be
fabricated using printed circuit board used to convey microwave
frequency signals.
 Microstrip Patch Antennas (MPA): These antenna comprises of
planar layers including a radiating element, an intermediate dielectric
laye r, and a ground plane layer.
Microstrip
antenna
INTRODUCTION
6

 The radiating element may be square, rectangular,
triangular, or circular and is separated from the
ground plane layer
Representative shapes of microstrip patch elements
INTRODUCTION

 Surface waves are guided waves captured within the
substrate and partially radiated and reflected back at the
substrate edges.
 The ground plane of a printed antenna is always is finite in
size, surface waves propagates until they reach an edge or
corner.
 The diffracted waves take up apart of energy of the signal
thus decreasing the desired signal amplitude and contributing
to deterioration in the antenna efficiency as well as increasing
both side lobe and cross polarization
Surface Waves

 The material of Printed Circuit Board (PCB) used in my
design is FR4 utilize as substrate.
 where "FR" means Flame Retardant, and Type "4" indicates
woven glass reinforced epoxy resin.
 Dielectric constant typically in the range (4.3-5.2),
depends on glass resin ratio.
 popular material and cost effective compared with other
PCB material that make this PCB is preferred.
FR4 Substrate
Material

 The main drawback of microstrip patch antenna is suffer from narrow BandWidth.
Antenna BandWidth (BW) can be improved by increasing the substrate thickness.
The thickness of substrate increases surface waves, surface waves pass through
the substrate and scattered at bends of the radiating patch which caused degrade
the antenna performance.
 To overcome this problem, the technique of air-gap that represents substrate
layer which has the dielectric constant is 1, by using air substrate, the surface
waves is not excited easily.
Problem Statements:
surface waves
0

 To increase the efficiency of the microstrip patch antenna
by decreasing the loss of the reflection, it is executed by
using air-gap as a substrate in microstrip patch antenna.
 To reduce the cost in the fabrication of the antenna by
using the cheap and popular FR4 material. The resonant
frequency can adjusted without requiring new design by just
varying the height of the air-gap also as well as the FR4
material this made the fabrications very cost effective.
Project Objectives:
1

 To improve the BandWidth (BW) by increasing the
thickness of dielectric substrate and dielectric constant with
lower value.
 To reduce the energy loss due to surface wave, the
surface waves consume apart of energy of the signal thus
decreasing the desired signal amplitude and contributing to
deterioration in the antenna efficiency that weaken the
microstrip antenna’s performance.
Project Objectives:
2

 Use the resonant frequency 3.5 GHz for WiMax application, the
resonant frequency is chosen from IEEE 802.16-2004 span of 2-
11GHz.
 Choose the air as dielectric substrates that have the value of dielectric
constant 1 in order to reduce the surface wave excisions.
 Use the transmission Line model for calculation of patch Dimension. It’s
the simplest of all and gives good physical insight.
 Simulate and Verify antenna design performance by applying Computer
Simulation Technology Software (CST) to design MPA.
 Use AutoCAD software to open the DXF file that exported from CST
software simulation.
Project Scopes:

 Microstrip Line Feed : A conducting strip directly connected to the patch which
is smaller in dimension as compare to patch. It is very easy to fabricate, very
simple in modeling and match with characteristic impedance 50Ω or 75Ω. This
type of feeding was not successful when using with air-gap substrate.
 Coaxial Feed: Feed the inner conductor of coaxial extends through the
dielectric and is soldered to the radiating patch, while the outer conductor is
connected to ground plane, it is easy to fabricate and match. It has low spurious
radiation, and it has narrow bandwidth.
Coaxial FeedMicrostrip Line Feed
Feeding method:

 Aperture Coupled Feed: is more complex and more difficult to fabricate
as compare to others, High dielectric material is used for bottom substrate and
thick and low dielectric constant material for the top substrate .
 Proximity coupled Feed: Its fabrication is not easy as compare to other
feed techniques, the advantage is eliminates spurious radiation and provides high
bandwidth (as high as 13%), due to overall increase in the thickness of the
microstrip patch antenna.
Proximity coupled FeedAperture Coupled Feed
Feeding method:

MICROSTRIP
PATCH ANTENNA
DESIGN

 Resonant frequency: The Resonant frequency was used in MPA for
IEEE802.16-2004 is 3.5 GHz, and take the span (3 - 4) GHz used in
reflection loss and BW calculations.
 Dielectric Substrate: FR4 PCB material is used as a substrate.
Reflection loss and BW are calculated when using singleFR4 PCB.
Subsequently, air is used as the substrate between two PCB FR4
substrates that improves the BW as well as reduce the loss of the
reflection. These are compared with the data when using singleFR4
PCB.
 Thickness of Substrate: The thickness of Air substrate was
designed and fabricated by using 2mm spacer, the thickness of the
FR4 substrate is 1.6mm.
Many factors were determined before begin the design

 FR4 Substrate Dimension:
 λ » λ = 85.71 mm,
 The width and the length of substrate is λ/2,
FR4 substrate
dimensions:
SIDE VIEW
TOP VIEW

 The effective dielectric constant is a function of a frequency.
 Effective Patch Width (W)
 Frings factor (ΔL)
Transmission line model formula:

 Effective length (Leff):
 Length:
 The patch is actually a bit larger electrically than its physical
dimensions due to the fringing fields and the difference between
electrical and physical size is mainly dependent on the PC board
thickness and dielectric constant of the substrate.
Transmission line model formula(continued) :

The design and fabrication
process
included two case
SECOND CASE
Air-gap TECHNIQUE
First Case
SINGLE FR4 Board
1 2

First Case
SINGLE FR4 Board
Using As Substrate
Material

Effective Dielectric Constant (εreff) is
W=26.33 mm
= 3.90
First Case (Single PCB-FR4 Only) as Substrate Material:
Calculations for Patch Antenna Dimension:
Width of the Patch (W) is
resonant frequency f° =3.5 GHz, dielectric constant for FR4 substrate is
εr= 4.3, height of substrate for Fr4 PCB is h=1.6 is the principle
parameters must be decided.

ΔL = 0.74 mm
L = 20.22 mm
Length of the patch is:
Fringing Field Length Extension (ΔL) is:
Length of the patch is:

(13.16, 3.41) mm
Location of the feed
Design location of the coax line feed
x

 By using the same formula for case 1, and substitute f° =3.5 GHz, εr = 1,
Air h= 2mm Will get
W=42 mm
ΔL = 1.41mm L =40 mm
Second Case (Air-gap with two PCB-FR4) as Substrate
Material
W=42 mm
ΔL = 1.41mm
Edge Impedance = 120.11
Position of the feed (21, 8.93)
Second Case (Air-gap with two PCB-FR4) as Substrate
Material

Design structure
&
Simulation Result
with
Single patch antenna
Using
CST Software

 The ground plane is made of copper have thickness 0.07 for the patch
Structure of Design single patch antenna
Design, Simulation, Fabrication and Measurement Result
61

Structure design simulation of single FR4 board
Structure design of Single patch antenna using CST software

(Operating frequency and S11) Simulation of single patch antenna
S11 for single Patch Antenna Without
air-gap
1D Results:

 At resonant frequency 3.5 GHz is exhibit S11 equal (-10.38 dB)
simulated by CST, the BandWidth (BW), the simulated BW is exhibit
36 MHz that become clear when using FR4 only without Air-gap have
narrow BW.
Bandwidth Simulation of single patch antenna
Bandwidth Simulation of Single Patch Antenna without air-gap

The plot displays some important properties of the coaxial
mode such as TEM mode type, line impedance.
Input impedance simulation with single patch antenna
2D Results:

Design structure
&
Simulation Result
with
Air-gap Technique
Using
CST Software

 The ground plane is made of copper have thickness 0.07 for the patch
Structure Design with Air-gap technique
2

Structure design simulation with air-gap technique
Structure design of Single patch antenna
using CST software

(Operating frequency and S11) Simulation with air-gap technique
2D Results:
Simulation Result for Patch Antenna
with Air-gap

 At resonant frequency 3.499 GHz is display S11 equal (-42.87 dB)
simulated by CST, The BW that getting by using Air-gap that have value
is 96 MHz
Bandwidth Simulation with air-gap technique
Bandwidth Simulation with air-gap technique

Input Impedance simulation with air-gap technique
2D Results:
Design, Fabrication, Measurement and Result

MPA with air-gap technique
MPA With air-gap
Technique
81

S11 Measurement
Reflection Loss of
Fabrication 7

 Resonant frequency 3.5 GHz is exhibit reflection loss (-27.650 dB)
measured by VNA. The BW for MPA with Air-gap fabrication is (158
MHz), calculation is achieved by subtract the value 3.589 GHz of M3
from M2 that have value 3.431GHz.
measured microstrip patch antenna with air-gap results
Measurement
Parameter Measured MPA Results
Resonant Frequency (fo GHz) 3.5 GHz
Reflection loss (S11 dB) -27.650 dB
Input Impedance, (Zin ohm) 54.270 ohm
BandWidth (BW MHz) 158 MHz

Smith Chart display the resonant frequency 3.5 GHz and it exhibit
impedance matching is 54.270 ohm which is actually closer to the
50ohm.
The Smith Chart Parameter
Smith chart parameter
The parameter
measurement
Resonant Frequency
(M 1)
Frequency measured 3.5 GHz
Input Impedance measured 54.27 ohm

Compare between Measurement and Simulations with Air-gap and without air-gap
Analysis Result
1 3
Exel

Comparison between the Simulated Result of the MPA without Air-gap
and simulated as well as measured results of MPA with Air-gap
Comparison Table of Simulated and Measured Results:
Parameter
Microstrip Patch
Antenna without
Air-gap
Microstrip Patch Antenna with
Air-gap
Simulated Simulated Measured
Resonant Frequency (fo GHz) 3.5 3.5 3.5
Reflection loss (S11 dB) -10.38 -42.87 -27.650
Input Impedance (Zin ohm) 46.16 45.63 54.270
BandWidth (BW MHz)
36
(1.02 %)
96
(2.74 %)
158
(4.51 %)
3

Fabrications process
Flow chart for fabrication process

Fabrications process
Dry film printed
Fixing dry film
on PCB
1
2

UV exposure process
3
4
The FR4
PCB after
exposed
to UV light
5
UV exposure
machine
Removing
the
transparent
layer

Developing process
7
6
Developing
machine
FR4 after
developing
process

Etching process
8
9 10
Etching
machine

Etching process
11
Ground
Front Face

Stripping process
12
13
Stripping
machine
The FR4
board
after
stripping
process

Dry Process
14
15
The FR4
board
after
stripping
and Dry
process
Dry
machine

PCB Cutter Machine
16
17
PCB Cutter
machine
18
The FR4
board after
stripping and
dry process

Drilling Machine
19
20
PCB Cutter
machine
21
Make
hole for
location
of probe

 The spacer between two FR4 boards is cylinder wood material; the
diameter for the standing is 6mm.
Spacer between the Substrate
Layers
Spacer

FR4 Substrate Material:
 The joining between the Fr4 substrate layers with spacing is doing by
SUPA GLUE implement at 10 seconds.
Supa Glue
Stick

 Technique design with air-gap, use two FR4 PCB substrate each
layer have thickness is 1.6mm, the first board is consist of FR4
substrate have radiating patch but it strip from ground plane, the
second board is consist of radiating patch and ground plane separated
by FR4 substrate, the separation between two layers is air-gap.
FR4 Substrate with Air gap Separation
MPA with Air-gap technique

CST Microwave Studio:
 Computer Simulation Technology (CST) develops and markets
software tools for the numerical simulation of electromagnetic fields.
CST was founded in 1992 in Darmstadt, Germany.
Select Template
 Create a new CST microwave studio project after open CST design
environment.
CST Microwave Studio

 Antenna Template

 Draw the Substrate Brick
Creation Brick

 continue with the same thing by drawing the air-gap and second layer for
substrate-2, but only change the material in air-gap substrate to air from
material library list
The Air-gap with Two
Layers Substrate

 Draw the ground plane, this perform by choose the pick face and clicking
to the surface of substrate FR4-2 and pick to the surface of substrate

 By using extrude tool to create the ground plane for the second layer of
FR4 substrate.
Ground Plane
Extrude
Face
Ground Plane
Extrude
Face

 Construct the dual patch first is stacked patch antenna and the second
is the probe fed patch,
stacked patch antenna probe fed patch antenna

 Model the Coaxial Feed
Outer Inner
Feed Feed
,

 Common Solver Setting: Define Waveguide Port
 Wave guide port consist of add the excitation port
Solve →Waveguide Ports
Waveguide Port Excite Port

 Define the Frequency Range and Boundary
Conditions
+
Frequency Range Boundary Conditions

 Define Farfield Monitor
Farfield Monitor

 The VNA device is divided into two parts, the first is
screen and the second is control button. The screen
is used for display the graph, this graph represent
the S11and BW that will be measured and analysed.
The control button consists of seven sections
arranged from top to bottom and from left to right is
(TRACE, NAVIGATION, CHANNEL, SUPPORT,
DISPLAY, DATA ENTRY, SYSTEM). The start of
the frequency range and the stop span on VNA
device, its accomplished by selecting CHANNEL
section from control button. Then, checking the
resonant frequency and it was 3.5 GHz, and the
span 1 GHz.
Network analyzer
4

MPA with Air-gap Measurement 7

Improvement of bandwidth 2
Single patch antenna simulation Air–gap technique simulation

Coax line feed
Coax line feed location
x

Microstrip patch antenna for wimax applications

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