1. Antenna Design for Zigbee System
Chapter 1
Part One- Introduction to Antenna
Part Two- Antenna Operation
Notes for the Instructor
Please ask each workshop participant to run the Chapter 1 Shockwave Movie (duration 17.5 minutes) without interruption
Follow the movie by this presentation explaining each slide as mentioned in footnote

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Contents
In this Chapter 1 (Part 1) we will see
What is an antenna?
3D space and principal planes in spherical co-ordinates
Role of antenna as matching element and directional element
Field regions around an antenna
Types of antenna- wire antenna, aperture antenna & microstrip antenna
Antenna arrays
Notes for the Instructor
a) These are the topics covered in the presentation
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What is an Antenna?
Figure 1: Antenna
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4. 3D space and Principal PlanesX Y Z r O
spherical co-ordinate system
Angle with XZ
Angle with Z-axis
Radial plane
Azimuth plane
Elevation plane
Notes for the Instructor
a) Help participants visualize the spherical co-ordinate system
b) Explain theta, phi and radius.
c) Show the Azimuth, Elevation and Radial Plane
d) Explain the incremental area on each of the principal planes
Figure 2: 3D Space and Principal Planes in Spherical Co-Ordinate System
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Role of Antenna Vg Xg Rg
Signal Source Xa R L
Antenna
With conjugately matched signal source
Vg /(4Rg) 2
Vg /(8Rg)
Vg /(8Rg) x R
/(R +R )
Figure 3: Thevenin Equivalent Circuit
Conduction-dielectric efficiency
Dissipation Factor
Notes for the Instructor
Show the Thevenin Equivalent Circuit of the signal source and the antenna
Explain antenna as a matching element between the radio and the free space
Explain each resistance and reactance
Explain Maximum Power Transfer condition for the circuit
Mark the Conduction Dielectric Efficiency and the Dissipation factor
Explain antenna as a spatially directional device
Define Radiation Pattern of an antenna
Antenna also acts as spatially directional device for radiating & receiving radio waves
Radiation Pattern or Antenna Pattern is a measure or a graphical representation of antenna's
radiation property as a function of space co-ordinates
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6. Field Regions in Free Space
Where is the antenna’s radiation property investigated in space?
Field Regions of an antenna in space
D is maximum dimension of the antenna
is radiation wavelength
There are three field regions
Reactive Near Field R 1
=0.62 D / 3
For D<< ,R 1
= /2
Radiating Near Field (Fresnel Zone) R 2
= 2D /
, R 1
< r < R R 1 R 2
Radiating Far Field ( Fraunhofer
Zone) R 2
< r <
Thin wire half-wavelength long dipole
Figure 4: Field Regions
Notes for the instructor
Mark Reactive Near Field Zone, Fresnel Zone and Fraunhofer Zone around an antenna
Define various zones
Mention that all the radiation patterns are investigated in Radiating Far- Field Zone
Reactive Near Field Region is the immediate surrounding region of the antenna where reactive field predominates. Energy is
Stored in pockets of electric and magnetic fields.
Radiating Near Field Region also known as Fresnel Zone exists when the maximum dimension of the antenna is comparable to the
wavelength. In this zone, radiating field predominates. The angular distribution of radiation property is dependent on the distance
from the antenna.
Radiating Far Field Region also known as Fraunhofer Zone, is the region beyond R where angular distribution of the radiation
property is independent of the radial distance from the antenna 2
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Types of Antenna
Wire Antenna
Dipole Antenna
Monopole Antenna
Loop Antenna
Helical Antenna
Figure 5: Wire Antenna
Aperture Antenna
Microstrip Antenna
Notes for the Instructor
a) Explain (wire antennas) what is a dipole, a monopole, a loop antenna, and a helical antenna, where are they used and briefly their salient feature
b) Show the Aperture of the Aperture Antenna and explain their relation to waveguides.
c) Show the patch antenna and point to its important parts namely- Coaxial to microstrip transition, step transform matching, the feed point and the rectangular patch.
Mobile Phone Antenna
Rectangular
Patch Antenna
Conical Horn
Pyramidal Horn
Sectoral Horn
Figure 6: Aperture Antenna
Figure 7: Microstrip Antenna
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Antenna Array
Antenna Array is an array of two or more antennas placed in certain calculated geometry, sized appropriately and
fed in certain fashion to result in the desired radiation performance and size.
Notes for the Instructor
Explain what is an antenna array?
Show the feed and the reflector part of the parabolic dish
Show Cassegrain Feed
Show the folded dipole in Yagi-Uda Antenna and various reflectors & directors.
Parabolic Dish
Parabolic Dish with
Cassegrain Feed
Log Periodic Antenna
Yagi-Uda Antenna
Figure 8: Antenna Array
In many such arrays Reflectors and Directors are used to improve directivity of the antenna
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Session Summary
In this session
We defined antenna as a metal structure that transmits radio waves & captures them.
We defined θ as an angle with z-axis, Φ as an angle with x-axis in xy-plane, and r as radial distance from the origin.
We defined Azimuth Plane for which θ is constant, Elevation Plane for which Φ is constant and radial plane for which r is constant. We saw incremental area on each of the principal planes.
We represented a signal source and an antenna by their Thevenin Equivalent circuit and applied the condition of Maximum Power Transfer to compute reactive, dissipated, and radiated power. We represented conduction dielectric efficiency and dissipation factor in terms of equivalent resistances.
We defined the region of Reactive Near Field, Fresnel and Fraunhofer Zones.
We mentioned few examples of Wire Antenna, Aperture Antenna and Microstrip Antenna. We also saw some examples of antenna arrays namely Parabolic Dish with and without Cassegrain Feed, Log-periodic Antenna and Yagi-Uda Antenna
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Contents
In this Chapter 1 (Part 2) we will see
Static charges as a source of static Electric Field
Time harmonic of fixed charges as a source of Electromagnetic Waves
Time harmonic of current as a source of Electromagnetic Waves
Standing wave pattern in a λ /2 dipole and its time harmonic nature
Voltage and Current standing waves on a λ /2 dipole as a source of EM Waves
Notes for the Instructor
a) These are the topics covered in the presentation
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11. Source of Electric Field
Types of Electric Field in Space
Static Electric Field- Electric Field that does not change with time
Dynamic Electric Field- Electric Field that changes with time
Static Charges as a Source of Static Electric Field
Governing Maxwell’s Equation Δ
.D = ρ V
Source of Electric Field is electric charges. Electric
Lines of Force initiate at positive charges and terminate at negative charges
Relation of Electric Field to Potential
Figure 9: Static Field from Static Charges
E = - V Δ
Notes for the Instructor
a) Show the source of Static Electric Field and the governing Gauss Divergence Theorem.
b) Explain the relation between the Electric Field and the Scalar Potential
Such an arrangement of static charges has no mechanism to generate magnetic field and hence incapable of setting up Electromagnetic Waves. For Electromagnetic waves to exist, there must be time varying Electric and Magnetic Fields
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12. Time Varying Electric Field
Time Varying Electric Field (or Electric Current) as a Source of Loops of Magnetic Field + _
time E H
Source of Loops of Magnetic Field is time varying Electric Field or Electric Current Density
Governing Maxwell’s Equation Δ
X H = Js + D / t ρ
EM Waves
In the present set-up of fixed charges in space, there is time harmonic to the charges, capable of setting of time varying Electric Field which sets up Magnetic field. The electric current density is zero. This is equivalent to voltage standing waves on a resonant length wire.
Figure 10: Time harmonic of charges set up TEM Waves
Notes for the Instructor
Explain the Maxwell’s Curl Equation
Show the generation of TEM Waves
EM Waves
EM Waves
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13. Time Varying Magnetic Field
Time Varying Magnetic Field (or Magnetic Current) as a Source of Loops of Electric Field E H
time L I
open end
Source of Loops of Electric Field is time varying Magnetic Field or Magnetic Current Density
Governing Maxwell’s Equation Δ
X E = - Ms - B / t ρ
In the present set-up of standing wave current on a wire, there is time harmonic of current, capable of setting of time varying Magnetic Field which sets up Electric Field. The magnetic current density is zero. E H
time L I
open end E H
time L I
open end
Notes for the Instructor
Explain the Maxwell’s Curl Equation
Show the generation of TEM Waves
Figure 11: Time harmonic of standing wave Electric Current sets up TEM Waves
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14. Standing Waves on a Open-ended Wire Pair
V (t)
λ/2 L
V (t)
Lets cut the wire here + _ V- I+ I-
λ/4 V+
V (t) V- I- I+ V+
Peak Impedance
Min. Impedance
The standing wave patterns on the dipole result in Transverse Electromagnetic Waves. The impedance variation along the length of the dipole is used to determine the feed placement later
Notes for the Instructor
Show the voltage and current standing waves
Explain the impedance variation along the dipole length
Figure 12: Standing waves on λ/2 long dipole
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Half-Wave Dipole t
V (t)
I (t) + _ I V- I- I+ V+ L V H E
Standing wave pattern on a half-wave dipole acts as a source of Transverse Electromagnetic Waves.
Figure 13: TEM Waves from Half-Wave Dipole t
V (t)
I (t) + _ I V- I- I+ V+ L V H E t
V (t)
I (t) + _ I V- I- I+ V+ L V H E
Notes for the Instructor
Show the source of TEM Waves from standing wave voltage and current waves on a dipole
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16. © Copyright 2009 Agilent Technologies
Session Summary
In this session
We learned about the source of static electric field. Gauss Divergence Theorem is the governing relation.
We learned about time-varying electric and magnetic fields that result in loops of magnetic and electric fields respectively. Maxwell Curl equations are the governing relations.
We learned about voltage and current standing waves on a wire pair. We learned about half-wave dipole and mechanisms of TEM - wave radiation from it.
Notes for the Instructor
a) Conclude by summarizing these points
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