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

© Copyright 2009 Agilent Technologies 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 © Copyright 2009 Agilent Technologies

© Copyright 2009 Agilent Technologies What is an Antenna? Figure 1: Antenna © Copyright 2009 Agilent Technologies

3D space and Principal Planes X 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 © Copyright 2009 Agilent Technologies

© Copyright 2009 Agilent Technologies 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 © Copyright 2009 Agilent Technologies

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 © Copyright 2009 Agilent Technologies

© Copyright 2009 Agilent Technologies 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 © Copyright 2009 Agilent Technologies

© Copyright 2009 Agilent Technologies 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 © Copyright 2009 Agilent Technologies

© Copyright 2009 Agilent Technologies 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 © Copyright 2009 Agilent Technologies

© Copyright 2009 Agilent Technologies 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 © Copyright 2009 Agilent Technologies

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 © Copyright 2009 Agilent Technologies

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 © Copyright 2009 Agilent Technologies

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 © Copyright 2009 Agilent Technologies

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 © Copyright 2009 Agilent Technologies

© Copyright 2009 Agilent Technologies 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 © Copyright 2009 Agilent Technologies

© 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 © Copyright 2009 Agilent Technologies