01. Antennas

Microwave and Antenna Lab.

1. Antennas

Second Semester, 2004Dept. of Electrical and Electronic Engineering,

Yonsei University Prof. Young Joong Yoon


1. Introduction

Etymology of Antenna

Antemna (Latin) ⇒ Antenna ; the pole of the triangular sail

Antennae : a pair of feeler, the sense of touch of an insect

Antennas :

Energy transitional structure between free-space and a guiding device

Etymology of Aerial

Aereum (Latin) : aer (air) : in the air/ occurs in the air ( 空中線 )


1. Introduction

Definition

A usually metallic device (as a rod or wire) for radiating or

receiving radio waves (Webster’s Dictionary)

A means for radiating or receiving radio waves (IEEE Std

145-1983)

The transitional structure between free-space and a

guiding deviceGenerator Transmitter Receiver

antennas


2. History

James Clerk Maxwell (1831~1879, Scotland)

The mathematical model of electromagnetics (“Dynamical Theory of the Electromagnetic Field”, 1864)

Maxwell equations implicitly required the existence of electromagnetic waves traveling at the speed of light.

Heinrich Rudolph Hertz (1857~1894, Germany)

In 1886, he assembled a complete radio system

with an end-loaded dipole as the transmitting

antenna and a square-loop antenna as receiver.

He also experimented with a parabolic reflector

antenna.


2. History

Guglielmo Marconi(1874~1937, Italy)Father of RadioIn 1901, he used his system for transmitting the first wireless signals across the Atlantic between Poldhu, Cornwall, and St. John's, Newfoundland, a distance of 2100 miles.

Receiving antenna: a huge antenna, a length of 200 meters long, sustained with wires and big kites.

Transmitting antenna: it consists of 50 wires sustained with poles, a height of 60 meters.

In 1896, he did a transmitting experiment in Bologna, his homeland.He used the word of “Antenna” for the first time at Royal Academy of Science in Dec.11,1909 when he received the Nobel Prize.

Alexander Popov(1859~1906, 러시아 )In 1963, the USA navy reported that he was the first scientist who did a wireless communication experiment for the first time over the world.In 1895, he did an experiment about transmitting and receiving of telegraph between Kronstadt center in Russia and a cruiser named Africa, a distance of 600 yards.Russian navy has securely kept his experiment regarded as one of the top secrets.


2. History

Transmitting antenna of

Marconi


2. History

Korean first radio communication (Kwangjeho)

· In 1904, It was produced from the Kawasaki shipyard in Japan · It had two vessel radio communication doublet antennas


2. History

Wolmido lighthouse wireless station

· A distant view of Wolmido lighthouse wireless station (left) · A complete view of Wolmido lighthouse wireless station (center) · In 1910, establishment of the microwave antenna (right)


2. History

Before the World War ( ~ 1940)In 1934, the advent of commercial wireless telephone system : Strait of Dover (1.8 GHz)Taking advantage of communication system until UHF band because there was limitation of Signal Generator technology.

The second World War ( ~1945)The invention of microwave sources (such as the klystron and magnetron) with frequencies of 1GHz and above.The invention of various antennas and circuit technologies such as Waveguide Aperture, Horn, Reflector, Lens antenna, et cetra, and the present antenna theory was established.

Antenna analysis methods development (1960~1980)IE (Integral Equation) method development based on computer technologies : MM (Moment Method), FDTD (Finite Difference Time Domain), FEM (Finite Element Method), etc.GTD (Geometrical Theory of Diffraction), etc.Combining method of IE and GTD

Semiconductor technologies development(1980~2000)It was utilized in various fields such as satellite, mobile and wireless communication technologies, medical, and exploration. Connection with MIC technologies


3. Types of Antennas



Wire Antennas

Dipole, monopole, loop, helical etc.

The most common antenna

It was utilized in various fields such as broadcasting, automobiles, mobile communication, ships, aircraft, etc.

Aperture Antennas

Pyramidal Horn, Conical Horn,

rectangular waveguide etc.

Antenna of this type are very

useful for aircraft and spacecraft

applications.



Microstrip AntennasMicrostrip antenna became very popular in the 1970s primarily for spaceborne applications.

Rectangular patch, Circular patch, etc.

The microstrip antennas are low-profile, simple and inexpensive to fabricate using modern printed-circuit technology.

Compatible with MMIC designs

Array Antennas

A configuration of multiple radiating elements is r

eferred to as an array antenna.

Yagi-Uda array, aperture array, microstrip patch a

rray, slotted-waveguide array, etc.

It was utilized in various fields such as satellite c

ommunication, mobile communication, etc.


3. Types of AntennasReflector Antenna

Parabolic, Cassegrain, Corner Reflector, etc.

High directivity and high gain

Radio telescope, satellite communication, Radar, etc.

Lens Antenna

Lens antennas are classified according to the material or

their geometrical shape.

Convex, Concave, etc.

They can be used in most of the same applications as ar

e the parabolic reflectors.


4. Radiation Mechanism

The core of antenna operation

1. Generation of Time-varying current

density J

2. Generation of Time-varying

magnetic field H

3. Generation of Time-varying electric

field E

4. Generation of Time-varying

magnetic field H

t

B

Et

DJH

Forming electromagnetic

wave that propagates in free

space.

The origin of electromagnetic

wave



ZlZ vqI

Single wire

To create radiation, there must be a time-varying current or an

acceleration (or deceleration) of charge.

zZ

lz qa

dt

dvq

dt

dI

zZ

lz lqa

dt

dvlq

dt

dIl



Two wires

Electric Field Line

Positive Charge->Negative Charge

Magnetic Field Line

Closed Loop

When Electric Field Line leaves the

transmission line, it is connected like

those dotted lines.

P propagates at the speed of light : P

propagates a half wavelength during the half

period.

The motion of electric charge makes

electromagnetic field, similar to wave of a

pond, and the electromagnetic field,

leaving an antenna, spreads continually

after the electric charge disappears.


0t

Tt8

1

Tt4

1

Tt8

3

Tt2

1

Propagation of an Electric Field Line and

its Detachment (Radiation) from the Dipole


Dipole


Tt8

10t

E field Lines of a Half-Wave

Dipole



Tt4

1 Tt

8

3


E field Lines of a Half-Wave

Dipole


Infinite line source in free space

FD-TDFinite-Difference Time-Domain (FDTD) is a popular electromagnetic modeling techniques. The FDTD method belongs in the general class of differential time domain numerical modeling methods.

Six-layer PML ABCcell size: 3 mmFD-TD cell: 50 x 506 cells for PML0.4ns Gaussian PulseTime step: 5 psMovie: 185 ps

nsc

xt 5

1032

103

2 8

3


Infinite line source in PEC wall

PEC Wall

cell size: 3 mm

FD-TD cell: 50 x 50

0.4ns Gaussian

Pulse

Time step: 5 ps

Movie: 185 ps


E-plane Horn in free space

8 layer PML ABC

9.84 Ghz CW

Space: 25.4 x 25.4 cm

cell size: 2.54 mm

FD-TD cell: 100 x 100

Time step: 4.23 ps

Movie: 296 ps


5. Current distribution on a thin wire antenna

(a) Two wire transmission

line

(b) Flared transmission line

(c) Linear dipole



Current distribution on linear

dipoles



Current distribution on a λ/2 wire antenna for different times


6. Research area

Improvement of the present antenna including all of satellite, mobile and wireless comm

unication, Radar, broadcasting system, medical applications, and using radio system.

UWB(Ultra Wide Band), RFID, DMB, wireless LAN, Bluetooth, and endoscope

Multi-Band antenna

Cellular, IMT-2000, WLAN, GPS, etc.

RF Integrated antenna

MMIC phased array antenna

Smart Antenna : maximization of SINR

01. Antennas

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