DESIGN, CONSTRUCTION AND PERFORMANCE ANALYSIS OF YAGI-UDA ANTENNA IN ULTRA HIGH FREQUENCY REGION

Presentation on DESIGN, CONSTRUCTION AND PERFORMANCE ANALYSIS OF YAGI-UDA ANTENNA IN ULTRA HIGH FREQUENCY REGION

INTRODUCTION

1. An antenna is a transducer designed to transmit or receive electromagnetic waves.
2. Transmission-transmits electromagnetic energy into space.
3. Receiption-receives electromagnetic energy from space.

Radiation through antenna

1. Eletromagnetic wave results due to acceleration of charges.
2. This time varying electric field has associated time varying magnetic field.
3. They comprise electromagnetic field.

OBJECTIVES

1. To become familiar with different types of antenna and antenna parameters.
2. To observe the performance of different types of antenna in terms of radiation pattern.
3. To design & implement two Yagi-Uda as transmitting & receiving antenna with three and five directors.
4. To compare the directivity between these two antennas.
5. To compare the designed antenna with the lab antenna using radiation pattern & MATLAB.
6. To observe the performance of designed antenna using mobile.

METHODOLOGY

Reasons of selecting Yagi-Uda antenna in Ultra High Frequency region

1. Yagi-Uda is a directive antenna.
2. The size of antenna decreases with increasing the frequency.
3. We can test the antenna in lab.
4. We can compare our designed antenna with lab antenna in terms of radiation pattern.

Different antenna parameters

1. Radiation pattern-The graph that describes the field strength versus direction at a fixed distance .Radiation patterns are taken at one frequency, one polarization.
2. Directivity-is the ratio of radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions.
3. Bandwidth-The bandwidth of an antenna is the range of frequencies over which it is effective, usually centered on resonant frequency.
4. Polarization-is the orientation of the electric field of radio wave with respect to the earth’s surface and is determined by the physical structure of antenna.
5. Main lobe-The direction of maximum radiation
6. Side lobe-The direction of minimum radiation.
7. Input impedance

Za-Antenna
Impedance
Za=Ra+jXa
Ra=Rr+Rl
Generator impedance
Zg=Rg+jXg

Elements of Yagi-Uda antenna

1. The Yagi antenna's overall basic design consists of a “resonant” fed dipole with one or more parasitic elements. These parasitic elements are called the “reflector” and the “director”.
2. The driven element of a Yagi is the feed point where the feed line is attached from the transmitter to the Yagi to perform the transfer of power from the transmitter to the antenna.
3. The directors are the shortest of the parasitic elements and are used to provide the antenna with directional pattern.
4. The reflector is the element that is placed behind of the driven element; its length is approximately 5% longer than the driven element. It's length will vary depending on the spacing.

Design of a Yagi-Uda antenna

While designing the antenna we consider some criterions

1. The length of the driven element
2. The length of the directors
3. The length of reflector
4. Spacing between directors
5. Spacing between reflector & driven element
6. Spacing between driven element & director
7. The type of driven element used

Range of length of different elements
Length of reflector=0.47 λ - 0.52 λ
Length of driven element=0.45λ - 0.49λ
Length of directors=0.4λ - 0.45λ
Range of spacing between different elements
Spacing between reflector & driven element=0.16λ - 0.35λ
Spacing between driven element & nearest
Director=0.2 λ -0.3λ
Spacing between directors=0.2λ - 0.3 λ
Range of diameter of elements=0.001λ - 0.003λ
Directivity Calculation

1. Directivity of N element Yagi-Uda antenna = 10log N + 2.2 dBd
2. For N=5, Directivity = 10log 5+ 2.2=9.2dBd
3. For N=7, Directivity = 10log 7 + 2.2=10.7dBd

Our designed antenna

1. Operating frequency =900MHz
2. We know, V=f λ
   Where v= velocity of light
   λ =3e8/900e6
   λ=0.33m
3. Length of the reflector=0.482λ=00.482*0.33=15.9cm
4. Length of the driven element=0.450λ=0.450*0.33=14.8cm
5. Length of the director 1=0.428λ=0.428*0.33=14.1cm
6. Length of the director 2=0.428λ=0.428*0.33=14.1cm
7. Length of the director 3=0.428λ=0.428*0.33=14.1cm

Our designed antenna

1. Diameter of all elements=0.01λ=0.01*0.33=0.33cm
2. Spacing between reflector & driven element=0.16λ=0.16*0.33=5.28cm
3. Spacing between driven element & the nearest director=0.2λ=0.2*0.33=6.6cm
4. Spacing between all directors=0.2λ=0.2*0.33=6.6cm

Our designed transmitter (3 and 5 directors)

Our designed receiver (3 and 5 directors)

Radiation pattern analysis
Lab transmitter and lab receiver


Our designed transmitter and receiver with 3 directors


Our designed transmitter with 5 directors and lab receiver


Our designed transmitter with 3 directors and receiver with 5 directors


MATLAB analysis
Lab and our transmitter with 3 directors



Our designed transmitter with 5 directors


Lab receiver and our designed receiver with 3 directors



Our designed receiver with 5 directors


Submitted BY KAZI SAMIRA SHAMSI HUQ and NEHLIN NURAIYAH NICKY