Design of rectangular patch antenna array using advanced design methodology

International Journal of Electrical and Computing Engineering
Vol. 1, Issue. 1, July – 2014 ISSN (Online): 2349-8218
13
DESIGN OF RECTANGULAR PATCH ANTENNA ARRAY USING
ADVANCED DESIGN METHODOLOGY
1
Abishek S, 2
Kaushik Ram S
Department of Electronics and Communication,
PSNA College of Engineering and Technology, Dindigul, INDIA
Abstract
Array antennas are used extensively in remote sensing
applications, where a highly directive beam is needed to
scan a particular area of interest on the surface of the
earth. The study focuses on the design of two different
microstrip patch antenna arrays to be used in
environmental sensing applications in the ISM
frequency bands. Arrays of microstrip patches are easily
printed on substrates using photolithography techniques
and can be mass produced at cheap costs. In this project
we have implemented two types of array model using
rectangular patch. Specifically, 1X2 and 2X2. This study
includes design of feedback network, impedance
matching, and return loss calculation. The substrate
used is FR4 with dielectric constant of 4.6 and thickness
about 1.6mm. The feed network is designed and
optimized using ADS 2013 and then integrated with the
array.
Keywords: Feedback network, Quarter wave
Transformer, Radiation Pattern, Return loss.
1. Introduction
A microstrip or patch antenna is a low- profile antenna
that has a number of advantages over other antenna. It is
lightweight, inexpensive, and easy to integrate with
accompanying electronics. There are different kind of shapes
to construct a single patch antenna. Among them, the shape
which adopt the needs can be separable. We choose
rectangular patch model. In order to build an array structure,
single element is designed with at most care. The application
software Advanced Design system has sufficient required
simulation techniques to check the antenna parameters. The
same result can be compared with the testing equipment,
vector network analyzer of Agilent.
2. Single element design issues
A microstrip antenna element can be used alone or in
combination with other like elements as part of an array.
In either case, the designer should have a step-by-step
element design procedure. Usually, the overall goal of a
design is to achieve specific performance at a stipulated
operating frequency. If a microstrip antenna
configuration can achieve these overall goals,
then the first decision is to select suitable
antenna geometry.
3. Single patch dimension
Selecting an appropriate substrate of thickness
(h) and dielectric constant (εr) for the design of the
patch antenna. In present case, we shall use
following Dielectric for design: Height: 1.6 mm.
Metal Thickness: 1.4 mil (Copper i.e. 35um), Er:
4.6, TanD: 0.001, Conductivity: 5.8E7 S/m.
Calculating the physical parameters of the patch
antenna as shown in the geometry in Figure 1
using the given formula.
Figure 1. Geometry of the Square patch antenna
The width and length of the radiation surface is
given by, W=L=(c/ (2f√εr)) = 29.2mm. Where,
velocity of light, c = 3*10^8 m/s, frequency f =2.4
GHz, relative permittivity, εr = 4.6.
The depth of the feed line in to the patch is
given by, H = 0.822*L/2 = 12mm. Other
dimensions are, Y =W/5 = 5.8mm, X = Z =
2W/5 = 11.7mm
3.1. Antenna simulation
Connect a pin at the feed point of the
antenna at the required point and go to the EM
setup window and click on Substrate then, click
on New to accept the 25 mil Alumina template.

14
Define the substrate as below, modify the default
substrate height, Er, TanD and conductor height and
define it as Copper (Select it from Add from Database
list). Changing name of the dielectric is optional as it has
no bearing on the simulation [2].
Click on Cond and check as intrude into the substrate.
Set the Simulation Frequency range as 2.1GHz – 2.7GHz
(adaptive sweep) and Add a new Single Point of 2.4GHz.
Click on Simulate and observe the simulation results
which has a S11 depth at single point frequency.
4. Design of an array antenna
This part includes the basic step necessary for the
design of an array antenna in ADS simulation software.
Place Patch Antenna feed point at (0, 0) coordinate to
make job easier for creation of our patch array. Place a
Pin for simulation at the centre of feed line [2,3]. This
step will ensure that all copied instances will also have
simulation pins else we will need to keep it manually.
Copy/Paste antenna element using Insert->Coordinate
Entry and enter required coordinates. Click Apply
between every coordinate entry. Press Esc button to
cancel the command. Select this entire row and then select
Insert->Coordinate Entry and enter coordinates.
For Patch Array design, separation between elements are
usually kept as 0.7*lamda – 0.8*lamda. In our case 93.75mm
is 0.75*lamda at 2.4 GHz on 1.6mm FR4 substrate.
Controversy, In case of calculation characteristic impedance
for the feedback networks (not for the matching transformer)
the length of the transmission line doesn’t depend on the
impedance. The only factor depends on the impedance is
width of the transmission line.
5. Important parameters
5.1 Return loss
S-parameters describe the input-output relationship
between ports (or terminals) in an electrical system. In
practice, the most commonly quoted parameter in regards
to antennas is S11. S11 represents how much power is
reflected from the antenna, and hence is known as the
reflection coefficient. If S11=0 dB, then all the power is
reflected from the antenna and nothing is radiated. If
S11= -10 dB, this implies that if 3 dB of power is
delivered to the antenna, -7 dB is the reflected power. The
remainder of the power was "accepted by" or delivered to
the antenna. This accepted power is either radiated or
absorbed as losses within the antenna. Since antennas are
typically designed to be low loss, ideally the majority of
the power delivered to the antenna is radiated.
5.2 VSWR
When a transmission line (a feeder cable, for example) is
connected to a load (say an antenna) a reflection may occur if
both impedances are not matched. The superposition of waves
traveling forward and backward on the same cable forms a
standing wave.
The reflection coefficient ρ which represent the
amplitude of the reflection. The return loss (RL)
which represent the reflection coefficient converted
in dB. The voltage standing wave ratio (VSWR)
which represents the ratio between the maximum and
minimum amplitude of the standing wave.
5.3 Impedance matching
The impedance matching, or Smith
*
chart
was created to enable graphical solutions of
transmission line problems. It maps complex
load impedances into the plane of complex
reflection coefficients.
The quarter-wave transformer is simply a
transmission line with characteristic impedance
Zo and length l =λ/4 (i.e., a quarter wave line). It
is often written as λ/4 impedance transformer, is
a component used in electrical engineering
consisting of a length of transmission line or
waveguide exactly one-quarter of a wavelength
(λ) long and terminated in some known
impedance. The device presents at its input the
dual of the impedance with which it is
terminated.
It is a similar concept to a stub, whereas a
stub is terminated in a short (or open) circuit
and the length designed to produce the required
impedance, the λ/4 transformer is the other way
around. It is a predetermined length and the
termination is designed to produce the required
impedance. The relationship between the
characteristic impedance, Z0, input Impedance,
Zin and load impedance, Zout is given by
Z0 = √( Zin Zout)
6. Linear 1x4 array
In order to make fair comparison, the
same substrate used in single element (Er= 4.6
and thickness h=1.6 mm), is used in the 1x2
array. The configuration of 1x2 linear
rectangular patch antenna array. To obtain 50
Ohms input impedance, feeding line with width
W1=4.85 mm is used. This line is split into two
100 Ohms lines, with width Wo =1.41 mm. The
configuration of 1x2 linear rectangular patch
antenna array is shown below
Figure 2. Configuration of 2x1 linear
rectangular patch antenna array

15
In an attempt to design 4x1 array, for both
rectangular and triangular, quarter wave transformer is
used to feed the elements. Figure 3 shows the
configuration of 4x1 rectangular patch antenna array. The
dimensions of quarter wave transformer are based on
Transmission line calculation in the ADS software [1]. It
can be seen the design resonate approximately at 2.4
GHz.
Figure 3. Design of 1x4 rectangular patch array
7. Linear 2x2 array
The design of 2x2 array antenna will follow after the
design of single patch antenna. To design an array we
need a feed network which will connect all the four
elements [2]. In order to have a matched impedance feed
network, we need to start from the input impedance of the
patch. The single element is fed by a 100Ω. So the
starting point of the feed will be 100 Ω. The scheme of
the feed network is as shown in the figure 4.
100 Ω 100 Ω
Ω7.70Ω100
50 Ω
100Ω
Ω7.7
0
100 Ω 100 Ω
Figure 4. Block diagram for 2x2
8. Simulated Results
The Return loss graph and Smith chart at the depth of
the frequency about 2.4GHz is shown below for 1x4 and
2x2 array antennas. In all the simulated outputs, the S11
value lies at the negative deep at the operating frequency,
while the impedance of the antenna at operating
frequency stays near to the midpoint for the exact
matching to radiate efficient.
Figure 5. Return loss of 1x4 array
Figure 6. Smith chart for 1x2 array
Figure 7. Return loss for 2x2 array
Figure 8. Smith chart for 2x2 array

International Journal of Electrical and
Computing Engineering
Vol. 1, Issue. 1, July – 2014
ISSN (Online): 2349-8218
16
Radiation pattern is one of the important
characteristic of an antenna as tells the spatial relative
distribution of the electromagnetic wave generated by the
antenna. Since the radiation pattern is supposed to provide
relative distribution of the fields, the absolute size of the
3-D surface does not have any significance. In practice
therefore the maximum amplitude is normalized to unity.
Figure 9. Side view of radiation pattern for 2x2
9. Conclusion
In the present work, arrays of Microstrip patch
antenna with different types are modelled using finite
element method and simulated in ADS 2013.
The results are compared with conventional
rectangular patch array for 1x4 and 2x2. By analysing the
results we inferred that the HPBW and BWFN decrease
as spacing between the array elements increases. The gain
and directivity increases with the increase in spacing. The
beam gets narrow if the number of the elements in an
array increases.
Considering the area of the element, Rectangular
shaped patch gave better gain and directivity at different
array models. The proposed antenna array is suitable in
designing the environmental scanning antenna and Phased
array Antenna. The simulation work carried out by us can
be made use for the design of any shapes of Microstrip
patch antenna.
10. References
[1] Ana Maria Yepes, “Multilayer Antenna Array for
Environmental Sensing Application”, 2010.
[2] Yahya S. H. Khraisat, Melad M. Olaimat & Sharief N.
AbdelRazeq, Comparison between Rectangular and
Triangular Patch Antennas Array, 2011.
[3] P.C. Dhanawade, L.S. Admuthe, Mrs. P.P.
Dhanawade, Simulation of Rectangular Patch Antenna
with Jeans Substrate.
[4] Amlesh Kumar Singh, Hem Prasad Ghanta, R.K.
Samminga and Dr.Anil Kumar Singh, “Design of an Inset
Fed Microstrip Patch Antenna Array with Integrated
Feed Network”, 2012

Design of rectangular patch antenna array using advanced design methodology

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Design of rectangular patch antenna array using advanced design methodology