Microstrip Antenna and Android theory

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Related work and current working system

Microwave technology at Solid State Electronic Division Uppsala University utilizes split Ring Resonator Antenna as a probe to analyze the osseointegration of skull implants which helps to diagnose the bone implant reunion in children suffering from intracranial pressure [21].
The SRR (Split Ring Resonator) Antenna is attached to a miniVNA (Vector Network Analysers). The system is connected with computer though USB cable or integrated through Bluetooth module. The measurement data is saved from user interface in different file formats however Prof. Robin Augustine’s group keep data in s1p file format, as shown in Figure 4.
a) Free space measurement of SRR Antenna.
b) SRR antenna is placed on the patient’s healthy bone area for reference.
c) SRR antenna is placed on the patient’s fracture bone in different area.
Measurement results are kept in s1p format file and then used for future analyzing.

Band Width

Band width can be defined as the range of frequencies where the antenna can operate correctly. For broadband antennas the band width is expressed in ratio and narrowband antennas band width is express in percentage [31]. For example, a 10:1 band width indicated that the upper to lower frequency is 10 times greater than the lower [31], [33]. 𝐵𝑊 = 100 × 𝐹𝐻−𝐹𝐿 𝐹𝐶 (2.8).
Where 𝐹𝐻 and 𝐹𝐿are the higher and lower frequency bounds. 𝐹𝐶 is the center frequency of the operating frequency band.

Return Loss

Return loss indicates matching of antenna with the transmission. When all the input energy is radiated from the antenna without any reflection, it is called ideal case but it is possible in the theory. In practice the antenna reflects some power back to transmission line which can be expressed in terms of return loss [34] . Return loss can be expressed in dB (decibels) unit. The input impedance is measured with respect to the transmission line. When the two antennas are not same, a voltage wave is reflected [22], [31], [34], [35] 𝜌 = 𝑍𝐴−𝑍0 𝑍𝐴+𝑍0 (2.9). 𝜌 is the voltage reflection coefficient, 𝑍𝐴 is the antenna impedance and 𝑍0 is the measurement characteristic impedance. 𝑟𝑒𝑡𝑢𝑟𝑛 𝑙𝑜𝑠𝑠 = −20log |𝜌| (2.10).

Microstrip Antenna

EM spectrum is divided into different frequencies range. The microstrip antenna is working on microwave frequencies, which ranges from 3 GHz to 300 GHz. The concept was proposed by Deschamps in 1953 but its patent was issued in France on 1955 in the names of Gutoon and Baissinot. However, 20 years later the first practical antenna was developed by Howell and Munson. The demands of microstrip antennas is increasing rapidly, this type of antenna became so popular for the mobile communication, the aircrafts, the space crafts , missiles and also as biosensor [31], [35], [36].
The microstrip antenna is consists of four elements (Radiating patch, ground plane, dielectric substrate and feeding) all those elements are kept in three basic layers [31], [35], [36] , as shown in Figure 7.
a) First layer consists of patch which is also called radiating patch.
b) Second layer consists of dielectric substrate and the feed lines are usually photoetched on the dielectric substrate.
c) Third layer consists of ground plane.

Types of Microstrip Antennas

Microstrip antennas can be designed into different geometrical shapes: circular, square, dipole and rectangular. Microstrip antennas are widely used for different applications. Researcher can also design some other patch shapes for special application [31] [36], as shown in Figure 8.

Feeding Methods

Various types of techniques have been developed to feed the microstrip antennas. Selection of the feeding techniques is depended on the application.
There are four popular techniques [31], [36].
a) Microstrip line.
b) Coaxial probe.
c) Aperture coupling.
d) Proximity coupling.

Microstrip line antenna used in the project

The microstrip feed is connected from edge to the microstrip patch as shown in Figure 9. This technique is popular in microstrip antenna because simple to model, easy fabrication, simple to match by controlling the inset position. The bandwidth is limited because of substrate thickness [31].

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Android Introduction

These days smartphones are gaining more popularity for multitude of applications. Smartphone has lot of hardware components like camera, light sensor, touch screen, and GPS (global positioning system) etc. The application can access that hardware through Android OS (Operating System). It was initial developed for simple mobile but later it was developed for smartphones, tablets, Android TV and Wearables [37].
Android was developed by Android Inc. In 2008 T-Mobile launched first android smartphone, Android 1.0 was the first open source mobile OS. The android framework is distributed under the ASL/Apache2 (Apache Software License). Daily 1.5 million Android devices are being activated and more than billion Android devices are in used [38], [39]. The developer needs a platform to develop mobile application, access mobile hardware for an application according to customer requirement, so Android provides that platform (Android Studio). Android provides advance features such as Cellular network, Media support, peer to peer connection, hardware support, web browsing, storage, multi-tasking and multi-touch screens [39].

Linux Kernel

Kernel is important component of OS. Kernel is running basic services such as process, memory management, networking, power management, security and preemptive multitasking. The kernel is an interface between hardware device and other layers, so software can easily communicated with hardware though the kernel. Android Linux kernel is the modified form of Linux kernel version 3.4 or above which is optimized for smartphone [37], [39], [43].

Libraries

Libraries is divided into two parts, one part have different collection of Libraries which helps to run Android software and second part called Android Runtime , as shown in Figure 10. Android has various C/C++ libraries, which helps to run the different services together such as OpenGL for graphics, SQLite used for Storage, Media Library helps to play audio and video, Free type is used for Font and WebKit library is used for web browser etc [37], [39], [43].

Android Run time

This part consists of core Libraries and DVM (Dalvik Virtual Machine). DVM is same like Java Virtual machine but DVM is more optimized for two reasons:
a) Limited memory.
b) Device can run multiple instances efficiently and instances are not dependent upon each other. If application crashes then other running application will not be affected and the running application will run smoothly.
Java source code of android application is first compiled to Java byte code and the next process JIT (Just In Time) converts Java byte code into Dalvik byte code, as shown in Figure 11. Android application is mostly written in Java, DVM is not Java Virtual Machine so Core libraries provides the Java functionality [37], [39], [43], [44].

Table of contents :

1 Introduction
1.1 Introduction
1.2 Long Bones
1.2.1 Fracture of long bones
1.3 Problem Motivation
1.4 Related work and current working system
1.5 Aim and Scope of Work
1.6 Tool Kit
2 Antenna theory
2.1 Antenna Theory
2.2 Properties of Antenna
2.2.1 Wave length
2.2.2 Input Impedance
2.2.3 Band Width
2.2.4 Return Loss
2.2.5 VSWR and Reflected power
2.2.6 Directivity and Gain
2.3 Type of Antenna
2.3.1 Wire Antennas
2.3.2 Aperture antennas
2.3.3 Microstrip Antennas
2.3.4 Array Antennas
2.3.5 Reflector Antennas
3 Microstrip Antenna and Android theory
3.1 Microstrip Antenna
3.1.1 Types of Microstrip Antennas
3.1.2 Feeding Methods
3.2 Microstrip line antenna used in the project
3.3 Android Introduction
3.3.1 Version of Android
3.4 Android Architecture
3.4.1 Linux Kernel
3.4.2 Libraries
3.4.3 Android Run time
3.4.4 Application Framework
3.4.5 Application Layer
3.5 Why Android for development
4 Designing
4.1 Design Rectangular Microstrip Antenna
4.1.1 Design Steps
4.2 Design analysis of Microstrip antenna
4.2.1 Selection of Material
4.2.2 Selection of Frequency
4.2.3 Selection of feed technique
4.3 Design of Android Application
4.3.1 Requirement Engineering
4.4 Proposed System
5 Development
5.1 Development of Sensor
5.2 Long Bone (Femur, Tibia) Properties
5.3 Antenna as sensor
5.4 Development of Android application
5.4.1 Module 1 Implementation
5.4.2 Module 2 Implementation
5.4.3 Module 3 Implementation
6 Conclusion and Future work
6.1 Conclusion
6.2 Future work
7 Reference
8 Appendix

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