Wireless Network Design and Antenna Optimization

The assignment discusses wireless networks and antennas, focusing on two research papers that design and implement different types of slot antennas for various applications. The first paper uses a double slot antenna for microwave ablation therapy to treat liver cancer, while the second paper designs a dual band slot antenna for WLAN applications. The papers employ different methodologies, including finite element method (FEM) and Micro strip feed line technique. The advantages and disadvantages of each approach are discussed, highlighting their strengths in specific applications.

WIRELESS NETWORKS
INTRODUCTION
In this, paper we will discuss wireless networks and antenna. Further, we will discuss about the
methodologies given in two research papers, compare their results, finds advantages and disadvantages
of each and also suggest for a future change. Wireless networks are the types of networks in which all
the nodes or systems are not connected by any type of wired medium for data connection. This type of
networks considerably saves cost or provides a less costly process while introducing cables to a building.
Generally these are implemented as radio communication and implemented in OSI layer. There are
several examples of wireless networks like satellite communication, WLANs or wireless local area
network, sensors or networks are generally wireless etc. Antenna is an essential component of a
wireless network as it sends and receives radio signals over different frequencies.
INTRODUCTION TO PAPERS
For this we have chosen two research papers, “microwave ablation therapy for the treatment of
hepatocellular carcinoma using double slot interstitial antenna” by Simran Kaur and Surita Maini [1] and
“Design of dual band slot antenna for LAN Application” by Ashish Patel [2]. In paper [1], author defines
ablation therapy as a procedure is used to combat Hepatocellular carcinoma, a type of primary liver
cancer. This is done with the help of microwaves that are focussed to send energy to abnormal tissues.
This method kills only the damaged targeted cells by sending direct radiations with the help of an
antenna. In the paper [2], the author explains various types of antennas along with major focus on
designing of slot antenna. The major advantage of a slot antenna is found to be its property that it can
be cut out of any type of surface, on which they need to be mounted on. Slot antenna typically operates
on frequencies that lies between the range 300 Mhz and 24Ghz. A slot antenna can be easily
constructed by using Micro strip feed line technique, which is majorly used for WLAN systems.
THE METHODOLOGIES
The method of antenna design for ablation therapy is explained in paper [1] is known as FEM (Finite
Element Method) which uses maxwell’s equation or fundamental electromagnetic equations to solve
the problem numerically. The information about tissue that will be targeted, EM properties and all the
proper initial and boundary conditions are considered. Penne’s bioheat equation –
ρC ∂T/∂t=k∇ 2T- ρρbCbF(T-Tb)+ ρSAR
It is used to get the temperature profile when electromagnetic waves propagate through the tissues.T
=temperature (C), t =time (s), ρ=tissue density (kg/m3 ), c = specific heat capacity (J/kg K),k is the
thermal conductivity (W/m K), ρb is the density of the blood (kg/m3), Cb is the specific heat capacity of
the blood (J/kg K), Tb is the temperature of the blood ( C), F is the blood flow rate (m /kg s).
The field in the tissues results into biological effects, is measured by specific absorption rate SAR
(W/m3),shown as:

SAR= σ/ ρ E² W/kg (2)
Where σ =conductivity of the tissue (S/m), ρ = density of the tissue (kg/m), and E =electric field (rms)
(V/m). The antenna used in this process has a micro coaxial cable. This antenna is used in treating cancer
of liver by passing microwave power into liver tissue
The method described in paper [2] includes determination of frequency range (Hz), input impedance,
gain and return loss (dB). The frequency range is specific for the application using antenna. Power
transfer between the antenna and transmission line will take place only when the input impedances of
antenna and transmission line are same. The overall efficiency of an antenna is referred as gain of the
antenna. Directivity of an antenna with 100% efficiency will be equal to its gain. Material losses,
impedance matching, other random losses etc are few factors that affect the efficiency of an antenna. In
dB, return loss is referred to as the negative of magnitude of reflection coefficient. Lastly, for antenna
design, parameters of antenna are finalised frequency, height, loss tangent, dielectric properties. Thus, a
lot of factors are to be considered in order to achieve acceptable gain performance for an antenna.
COMPARISON OF RESULTS
In both the papers, slot antennas are used but in [1] double slot antenna and in [2] dual band slot
antenna is designed. In paper [1], the geometrical models were used to assign material properties and
boundary condition values and thus, the generation of a finite element mesh is done. And the antenna
used has a power reflection coefficient of -21.015dB at 2.45Ghz. In paper [2], H-shaped slot antenna is
designed having return loss of -21dB at 5.6 Ghz in S-parameters and -36dB at 4.85Ghz
ADVANTAGE/ DISADVANTAGE
Both the papers are superior in their own ways as in [1], the antenna designed are used for curing
common type of liver cancer (i.e hepatocellular carcinoma), which is a very crucial and specific
application of double slot antenna. While on the other hand in [2], the antenna designed is dual band
which is very famous in WLANs these days. WLANs being an important aspect of day to day
communication, is also an important application of antenna.
CONCLUSION
In this research study, we studied two research papers that implemented and designing of antenna
models. These papers explained two different procedures to develop a slot antenna, which are used for
two different purposes. In paper [1], the designed antenna was used to pass energy in form of
microwaves to liver tissues by analysing electromagnetic wave propagation nature. In paper [2], we
studied how to develop a slot antenna using Micro strip feed line technique to cover WLAN bands. The
WLAN bands covered in this paper (2.4-2.485, 5.15-5.35, 5.725-5.825 GHz). The reflection coefficient of
antenna in paper [1] was found to be excellent and equal to -21.01 dB. In paper [2], return loss was -21
dB at 5.6 GHz and -36 dB at 4.85 GHz.

REFERENCES
[1] Maini, Surita & Marwaha, Anupma. (2013). Modeling and simulation of novel antenna for the
treatment of hepatocellular carcinoma using finite element method. Electromagnetic biology and
medicine. 32. 10.3109/15368378.2012.721849.
[2] Ashish Patel .Design of dual band slot antenna for LAN Application by, Department of Master of E.C
Engineering, LJIET, Gujarat Technological University-Ahmedabad