Session c 3 Tutorial

7/29/2019 Session c 3 Tutorial

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Communications:

Applications

Warren Stutzman and Bill Davisrg n a ec n enna roup

June 2, 2011

an enna.ece.v .e u


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1. Introduction Stutzman

2. Antenna Fundamentals Davis3. Antenna Elements Davis

4. Array Antennas Stutzman

break. ys em ons era ons Davis

6. Wireless Applications Both

.


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.

Self Introductions of Class

History of Communications

The S ectrum

Antenna Performance Parameters


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Fellow of the IEEE

& Prop. Society

Distinguished alumnus of Uo no s

Founder of Virginia Tech

Served as ECE Dept Headtwice


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years Director of Vir inia Tech

Antenna Group

Past Commission Chair

Incoming CommissionChair International URSICommission A

URSI Meetings Coordinator

Vice Chair 2005 IEEE

APS/URSI Symposium


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Wireless versus Wireline Fields of Application

Sensing and Imaging Active Radar

Industrial

Control Ex.: garage door opener .

Heating, cooking, drying, ...

Communications

Antennas must be used for: Mobile communications

Very long distances

pace

Remote terrestrial locations


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Antennas are preferred for Broadcast and point-to-multipoint comm.

Long distance communications

Thin routes

Portable and personal communications

. Loss in wireline is

Loss in wireless is

References

W. Stutzman and G. Thiele, Antenna Theory and Design, 2e, Wiley, 1998.

. , ,Prentice-Hall, 1996.

K. Siwiak, Radiowave Propagation and Antennas for Personal

Communications, Sec. Ed., Artech House, 1998.


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Pre-modern civilization

O tical communications: Smoke si nals, fla s, ....

Acoustical communications: Drums

[note all are forms of wireless ndigital communications]

1844

Telegraph (Morse) digital wireline comm.

1864

Maxwells equations principles of radio waves

Telephone (Bell) analog wireline comm.

1887

1897

First radio systems (Marconi, Popov)


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1901

1907Lee de Forest invented triode tube

1920KDKA, 1st modern radio station (Pittsburgh)

World War IIDevelopment of radar & Magnetron

Fiber optics

1980sWireless reinvented

Wireless Radio Wireless 1900 2000


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Antenna Performance Parameters

Radiation pattern F(,)The angular variation of radiation around an antenna

Pattern types:Directive (narrow main

beam)

Omnidirectional

Shaped beam

Low side lobe

Directivity DRatio of power density in the direction of pattern maximum to the

i.e. how much more focused the power is than if isotropically

distributed.

Directivity reduced by losses on the antenna


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.

Connecting to the antenna

Impedance

Pattern

Fundamental Limits


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Wire: Approximate sinusoid/traveling wave

current

)()()cos(),( yxzIzrJ =r

r


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1 rr

rrr

)( rrjHrE ==


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Far FieldLinear E-field Decibel E-field


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Current ~

r

r

Vector Potential

z

rj

ze

A =

r

Magnetic Field

r4

sinz

rj

Ie

jH =

r

Electric Field

sinz

rj

Ie

jE =

r

Poynting Vector

sin

16

2

1

2

1 222

22

2* z

r

IrHES

==

rrr

12

2 zI

P

=


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R i i n R i nShort Dipole

EQUATE Input Power &

Radiation Power

2 2

280

1 3

ra z zradR

I

=

L , For ractical di ole

2


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-


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Example: Approximate /4dipole

=

L = 0.5m

a. = . m


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22

== 22 ),()(),( dFFAverageD

,

)],(max[ DD =D =

4

A

An leSolidBeam2 == dF,


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Directivitd = sin ddd Fi ure 1-17

sin d Element of solid angle d.

UmUm

Figure 1-18Antenna beam solid angle A.

(a) Actual pattern (b)


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sinj r

eE I

= r

4 r

* ( , ) sinzh = r


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Linear, Circular, Elliptical

)cos(cos 21 ++= tEytExE


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/ *p h E h E=

r r r r

p=1 for matched wave and antennap= for CP ant. and LP wave

= .


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wt j( t + ) = E + E = E e + E e

x y 1 2E x y x y

2E

2 - -

Counter- Clockwise

1

E1

c oc w se1

2

-180 -135 -90 -45 0 +45 +90 +135 +180

Figure 2-37 Polarization ellipses as a function of the ratio E2/E1 and phase angle .

left-handed polarization (IEEE definition) while counterclockwise corresponds

to right-handed polarization.


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e= Realized GainR

== RR


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ththv trOC = )(rr


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-,

Balanced vs Unbalanced

Feed Network (Arrays)

True Time-Delay

Circuit & loading


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Im edance Treat as a circuit

element

= Induced EMF Z

mcv

= dJEJZ )(2rrr


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XmitRcv FF =


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Pattern Reciprocity


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A bit of Controversy

)1(

122233 ++

= aaa

Q

aaQ

1133 +=

102

Antenna Fundamental Limit

Inverted F

Dual Inverted F

Patch

101

iationQ

Dipole

Goubau

Planar Inverted F

Foursquare

100

Ra

Wideband, Compact, Planar Inverted F

McLean

0 0.5 1 1.5 2 2.510

-1

ka

GrimesChu


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.

Electrically Small Antennas

Broadband Antennas

Fre uenc Inde endent Ultra Wideband

Aperture Antennas


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The Four Antenna Types

Electrically Small Antennas

Examples

Short dipole Small loop

Properties

Low input resistanceLow efficiency and gain


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Resonant Antennas

Examples

Properties

Low to moderate gain

Real input impedance

Low efficiency and gain


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Broadband Antennas

Examples (Frequency Independent)

Spiral Log Periodic Dipole Array

,

frequency independent performance and ones that preserve

signal properties in the time domain (UWB)

PropertiesLow to moderate gain

Real in ut im edance

Low efficiency and gain


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Aperture Antennas

Examples

Low to moderate gainReal input impedance


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.

A. Array Basics

B. Arra s of Isotro ic Elements

C. Inclusion of Element Effects

. u ua oup ng

E. Phased Arrays


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Two element arrays of isotropic elements of various spacings


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y g

and phasings

0 45 90 135 180

d 18

d 14

d 38

d

I1

I 1

d 12

d 58

rom raus

d 1

General uniformly excited, equally spaced linear array (UE,ESLA)


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y , q y p y ( , )

r

zd d

0 1 2

Figure 3-7 Equally spaced linear array of isotropic point sources.

Nj d j d j nd

I I e I e I e = + + + =

1cos 2 cos cos

0 1 2 nAF L (3-14)n=0

jna

n nA e

Now consider the array to be transmitting. If the current has a linear phase progression

(i.e., relative phase between adjacent elements is the same), we can separate the phase

explicitly as(3-15)

where the n + 1th element leads the nth element in phase by a. Then (3-14) becomes

Define

( )N n d an

n

A e +

=1 cos0AF = (3-16)

ThenN

jn

n

n

A e

=1

0

AF =

(3-18)

Universal

array factor


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Universal arra factors for N = 3, 5, 10

1.0 ( )f 1.0 ( )f N= 5

N= 3

(b)0

0

0.4 0.8 1.2 1.6 2(a)

0

0

223

43

-

1.0 ( )f N= 10

spaced, uniformly excited linear array

for a few array numbers. (a) Three

elements. (b) Five elements. (c) Ten

elements.

(c)0

0

21.6 1.81.41.20.2 0.4 0.6 0.8


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Nonuniformly excited, ESLA


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y ,

-

jnn

n=0

AF A e d cos = +1.0

An

Uniform

1.0

0.5

00 2 z1/2 3/2An

(a)1: 1 : 1 : 1 : 1

Trian ular

1.0

0 2 z1/2 3/2An

(b) 1 : 2 : 3 : 2 : 1

Figure 3-24 Current distributions

1.0

0.5

0 2 z1/2 3/2An

(c) 1 : 4 : 6 : 4 : 1

Fig. 3-23. The current phases are

zero ( = 0). Currents are normal-ized to unity at the array center.

(a) Uniform. (b) Triangular.

1.0

0.5

0

0 2 z1/2 3/2An

(d)

-

for a side lobe level of -20dB

1 : 1.61 : 1.94 : 1.61 : 1

c nom a . d o p -

Chebyshev (SLL = -20 dB).(e) Dolph-Chebyshev.

0.5

0

0 2 z1/2 3/2(e)Dolph-Chebyshev

for a side lobe level of -30dB

1 : 2.41 : 3.14 : 2.41 : 1


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D 5HP 20.5

SLL 12 dB

== = .

HP 26.0

SLL 19.1 dB

== = D 3.66

HP 30.3

SLL dB

== =

180 1801800 0 0

1.00 1.00 1.00

0.75 0.75 0.750.250.250.25

0.500.500.50

(a) Uniform currents, 1 : 1 : 1 : 1 : 1. (b) Triangular current amplitude

distribution, 1 : 2 : 3 : 2 : 1.

(c) Binomial current amplitude

distribution, 1 : 4 : 6 : 4 : 1.

Figure 3-23 Patterns of several uniform phase (o = 90), equally spaced (d = /2)linear arrays with various amplitude distributions. The currents are plotted in Fig. 3-24.

D 4.22


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= D 4.68 .SLL 30 dB

== HP 23.6

SLL 20 dB-= =

1.000.75180 0

1.00

0.750.50

0.25

180 00.25

.

-

Current amplitude distribution, 1 : 1.61 : 1.94 : 1.61 : 1for a side lobe level of -20 dB.

(e) Dolph-Chebyshev

Current amplitude distribution,

1 : 2.41 : 3.14 : 2.41 : 1, with a side

lobe level of -30 dB.

Fig. 3-23 (continued)


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antennas in general:

As amplitude taper increases:

Directivity decreases (as a consequence of beamwidth increasing)

Sidelobes decrease

Current envelope:

Directivity of nonuniformly excited, isotropic element arrays


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Directivity of nonuniformly excited, isotropic element arrays

General case of unequally spacings and nonuniform phasings

N

Ak

2

1

-

( ) ( )( )m p

N Nm pj

m pm p m p

Dsin z z

A A ez z

=

=

1 1

=0 =0

Equal spacings and broadside operation

-

N

k

k

A

= = = 21

=0

S acin s a multi le of a half-wavelen th and broadside

( )( )

n nN N

m p

m p

m p dA A

m p d

1 1=0 =0 sin

(3-93), . . .

N

n

n

N

A

D d ,

= =

21

=0

1 ( )nn

A=0


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Collinear elements


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Example: Two collinear short dipoles

| |

x

I Io = =11 1 z(a) The array.

Element Array Total

pattern factor pattern

z

Figure 3-18 A linear array of parallel line

sources.

(b) The pattern.

sin

cos cos2

sin cos cos2

Figure 3-17 Array of two half-wavelength spaced, equal

amplitude, equal phase, collinear short dipoles (Example 3-8).


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Prob 3 3 2


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Prob. 3.3-2

2

1 1

From (2-7) ( ) =

a

cos cos2

g

sin

From (3-13) ( ) ( )f cos cosSo

( ) ( )( ) ( ) ( ) ( )

= =a

cos cos2

F g f cos cossin

ga x f F

zz

=

(Fig. 2-5b) (Fig. 3-6c)

Method used in practice to produce a single endfire beam


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x y

z

Ground plane

4

-

x y yz-plane (array

factor)

-1 -11 1

d =

2

d =

2

xz-plane (including/2 dipole effect)

Problem 3.7-7 uses array theory to find the patterns


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Base Station Collinear Arrays


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.

L2

= ( )From code

D 7.75 dBi d 0.72

5.6 dBd

A roximate directivit

= =

=

e i

D D D 1.64(5.4) 8.9, using Fig. 3-20

9.5 dB 7.3 dBd=

= ==

The tower enhances the gain by makingpattern more directive


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Base station with elements in

opposing pairs and clocked

90 degrees around the tower

to produce nearly an

omnidirectional pattern


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The input impedance of the mth element in an array with all elements active

an mu ua coup ng nc u e s


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an mu ua coup ng nc u e s

m 1 2 Nm m1 m2 mN

m m m m

V I I 1Z Z Z Z

I I I 1= + + + (3-103)

mV

mZ

mI

g

mZ

g

mVThis is often called active impedance or driving point impedance.

Note that active impedance depends on mutual impedances between elements

as well as the excitations of all elements. This dependence includes the

current phases and thus scan angle in phased arrays.

The effects of mutual coupling include:

The impedance of an element in an array differs from its free space value and depends

on that array scan angle (element phases) and the element location.

The pattern of an element is changed from its isolated pattern and depends on array

position.

Polarization characteristics deteriorate.


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E. Phased Arrays


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o= 900.75

1.00

o= 75

0.500.75

1.00

180 00.25.

z 180 0.

(a) o= 90 (b) o= 90 (c) o= 75o= 30

90 o= 090

180 00.250.50

0.75 1.0

180 00.250.50 0.75

1.0

z

(d) o = 30 (bifurcated pattern) (e) Endfire (o = 0)(f) Endfire (o = 90)

Figure 3-32 Example of phase-scanned patterns for a five-element linear array along

the z-axis with elements equally spaced at d = 0.4 and with uniform currentmagnitudes for various main beam pointing angles o.


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Phased array example: AWACS (Airborne Warning and Control System)

oun e on op o a rcra suc as - , - or aer a surve -


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p ,

lance and detection of bombers and low flying fighters coming in

over north pole

First operational radar antenna with very low sidelobes: -40 dB

o e wavegu e array w s o s

Scanned in vertical plane using ferrite phase shifters

Rotated for azimuth coverageNext generation: phased array conforming to the aircraft

-

Beam switched scanning


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1 x 4 Switch

(a)43 2

1

o e s

sP

Rotman

Lens or

ERP = PTGT = GePso

G

eP oGs

e

PP

4=se PP

4=

10 Log N

=1 x 4 Switch

Butler Matrix

1 2 3 4 T T o o

ERP P G NG NP=

== s s4G P

(b) (c)

Switched antenna system vs linear array configurations: (a) switched antennas;

(b) multiple-beam array; (c) steered-beam array.

sPs

P

[Microwave Journal, January 1987]


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Scanning arrays of wideband elements[Stutzman and Buxton, Microwave Journal, Feb. 2000.]


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0.9 6.4

0

d/)

1

. .

0.7

0.8

25.4

14.5

Ang

le

ntSp

acing(

0.4

0.5

0.6

90

41.8

ximumSca

alizedElem

0.2

0.3 MNor

1 1.5 2 2.5 30

.

Bandwidth (f/f )


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Basic Single Path

2

Xmit T RRcv P G G p=

Multipath link

( )( , ) ( , ; ,Rcv R R R R R R T TP G p C = 2

*

T R

G d d P

4


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wo ma n ac ors a ec ng s gna a

receiver Distance (or delay) Path attenuation

Multipath Phase differences

Green signal travels 1/2 farther than Yellowto reach receiver, who sees Red. For 2.4

GHz, (wavelength) =12.5cm.

Ref: UCLA, CSCI 694, 24 September 1999, Lewis Girod


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Free Space Loss

Atmospheric Absorption

Indoor

Doors

Walls

Waveguide effects (maybe use ducting)


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ti rrBasic Single Path

tcRv trOC

=4

( )R i t srr r

Multipath link

, ,

T R

OC r R R T T t R T c t


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Higher signal vs

Higher noise

g er requency Smaller Antenna

LowerQ for same size

Higher Gain for same size


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.

Antennas for Satellite Communications e c e n ennas

Antennas for Personal Communications

UWB Some Concepts


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Omnidirectional pattern base station


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Pattern is constant in azimuth and narrow in

Usually realized with collinear array of dipolesxamp e: e u ar ase s a on


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Antel Cellular

Base StationAntenna

870-970 MHz

Collinear dipoles

136 in long

10 dBd gain

1.25 deg downtilt

Sector base station

T i lPolarization diversity


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Typical

120 deg sectors, VP

Polarization diversity

120 deg sectors,


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A new wideband base station antenna developed at

:

Minimum number of antennas on tower


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Minimum number of antennas on tower

Dual-polarized for diversity

Multi-functional capability (800 ~ 2200 MHz)

Low profile and compact

Front view Tuning plate on back


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, , , ,

Measured Radiation PatternsMeasured Radiation PatternsE-planeH-plane


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HPBW: 60 ~ 80 Low cross-pol, less than -30 dB


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Vehicular Antennas

Broadcast receptionT diti l 31 (0 003 t AM) f d t hi t


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Traditional 31 (0.003 at AM) fender mount whip antenna.

New cars have mostly on-glass antennas

Example of aFord rear window

glass antenna

Two-way land mobile vehicle antennasVHF and below

Short monopole

Quarter-wave


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monopole

Example quarter-wave

monopole

UHF

Quarter-wave monopole

5/8 over wavelength


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Example 5/8 over

wavelength


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Example: Commercial MD-80 airplane


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VHFShort monopole


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p

Loo s small and/or loaded

Normal mode helix

UHF

Monopole

Normal mode helix

Patch

Inverted-L

anar nver e -Embedded

stubby antenna with an extendable wire antenna


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Nokia Patent

5,612,704


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(%)Wideband Compact PIFA

IFA 2

PIFA 8

po e

WC PIFA 43VT patent 6,795,028


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TEM Horn Ridged Horn BiCone

Tapered Slot (Vivaldi) Impulse Radiating Antenna (IRA)

Half-Disk


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Reflection Transmission Link


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-20

-10

0Return Loss

litude

(dB)

-50

0

Frequency Response s21

1(dB

)

0 2 4 6 8 10 12 14 16 18 20-40

-30

Frequency (GHz)

Am

0 2 4 6 8 10 12 14 16 18 20-100

Frequency (GHz)

s

-200

0

200ase - e ay ase

se(degrees)

1

2 x 10

9 21

plitude(s-1)

0 2 4 6 8 10 12 14 16 18 20

-400

Frequency (GHz)

Pha

0 2 4 6 8 10 12 14 16 18 20

-1

Time (nsec)

Am

At least 10:1 instantaneous Gain Bandwidth with 0.1 Size


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t east 0 Ga a d dt t 0 S e

Relatively-constant Monopole-like Radiation Pattern

Size & Performance Close to Theoretical Limits Light, Aerodynamic, and Inexpensive Design

-5

0

5

10

(dBi)

-35

-30

-25

-20

-15

-10

RealizedGain

0 2 4 6 8 10 12 14 16 18 20-40

Frequency (GHz)

Picture of Prototype Realized Gain v.s. Frequency Comparison to Limit

8

9

10

Measurement

FDTD [CST, 2007]

MoM [FEKO, 2007]0.5

1

ude

Measurement


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itu

2

3

4

5

6

VSWR

-0.5

0

NormalizedApl

2 4 6 8 10 12 14 16 18 201

Frequency (GHz)

4 4.5 5 5.5 6 6.5 7-1

Time (ns)

Measured and Simulated VSWRs Radiated Pulse

Measured Patterns @ Selected Freqs Printed Version: 450 MHz10 GHz


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SAR Specific Absorption Rate

Power per area absorption

HAC Hearing Aid Compatibility

System Interference and Cross-Modulation

Measured Near Field Pattern


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Calculated Far Field Pattern

INSTRUMENTATION

ANTCOM 7+1 axis near field farfield scanner

Agilent 8510, 8511, 8530 Network

Analyzer


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Antennas

Session c 3 Tutorial

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