Antenna Design for Zigbee System Chapter 4 Introduction to Patch Antenna Notes for the Instructor Please ask each workshop participant to run the Chapter 4 Shockwave Movie (duration 20 minutes) without interruption Follow the movie by this presentation explaining each slide as mentioned in footnote

© Copyright 2007 Agilent Technologies Contents In this chapter we will see Most common Microstrip Patch Structures Various methods to feed a patch antenna Transverse Electromagnetic (TEM) Waves in free space Transverse Electric (TE) Waves in free space Transverse Magnetic (TM) Waves in free space Solution for TEM Wave between parallel plates Solution for TM Wave between parallel plates Solution for TE Wave between parallel plates Notes for the Instructor a) These are the topics covered in the presentation © Copyright 2007 Agilent Technologies

Microstrip Patch Structures metal ground plane Dielectric Substrate Rectangular Metal Patch Figure 1: Basic Structure of a Microstrip Patch Antenna Rectangular Metal Patch Circular Metal Patch Circular Ring Ring Sector Disk Sector Notes for the Instructor Show the ground plane, the dielectric and the patch in the basic structure of a patch antenna Show various shapes that a patch antenna can take Figure 2: Various shapes of Microstrip Patch Antenna © Copyright 2007 Agilent Technologies

Microstrip Antenna Feed Types Microstrip Patch Feed It is the transition between the transmission line supplying power to the patch and the patch structure. Role of the feed is to transfer power to the patch in a matched fashion without interfering with the antenna radiation pattern. Microstrip Feed Types metal ground plane Dielectric Substrate Coax SMA Connector Dielectric Substrate metal ground plane Coaxial Feed Notes for the Instructor Mark the microstrip feed Explain the cut section of a coaxial feed- the SMA Connector and the slot in the ground plane for inserting the feed a) Microstrip Feed b) Coaxial Feed Figure 3: Types of Feed (a) Microstrip Feed (b) Cut section of Coaxial Feed © Copyright 2007 Agilent Technologies

Microstrip Antenna Feed Types Microstrip Feed Types Dielectric Substrate metal ground plane Second Dielectric Layer Aperture (Slot) Coupled Feed Slot in ground Feed Dielectric Substrate metal ground plane Second Dielectric Layer Proximity Coupled Feed c) Aperture (Slot) Coupled Feed Notes for the Instructor In the Aperture Feed mention about the slot in the ground plane- The advantage of such a feeding structure is that the antenna pattern is least distorted. In the proximity feed show the feed line and the ground plane d) Proximity Coupled Feed Figure 4: Types of Feed (c) Aperture Coupled Feed (d) Proximity Coupled Feed © Copyright 2007 Agilent Technologies

© Copyright 2007 Agilent Technologies TEM Wave in free space Transverse Electromagnetic (TEM) Waves TEM Waves have no electric and magnetic field vectors in the direction of propagation but normal to it and to each other. Amplitude variation of these vectors is along the direction of propagation and have time harmonic relationship. Solution in free space In a source free, lossless region X H = jωЄE & X E = - jωμH Considering propagation only along z-axis z x E y H - j 2 = X ( ) and j By definition of TEM Waves Ez=0 Hz=0 βx=0 βy=0 βz=ω μЄ Notes for the Instructor Explain that for propagation along z-axis only, all the transverse fields are not zero but the relation is of zero/zero form Mention about Helmholtz Equation as a second order equation obtained by combining two curl equations Mark the fields and mention the characteristic impedance of the medium Solving Helmholtz Equation - E Y0 e Z - j .Z x + E X0 y H = E = E X0 e Z - j .Z x + y Y0 & Characteristic Impedance in free space Z TEM = E x H y = - © Copyright 2007 Agilent Technologies

TM & TE Waves in free space Transverse Magnetic (TM) Waves TM Waves have no magnetic field vector in the direction of propagation but has electric field vector in the direction of propagation. Solution in free space In a source free, lossless region X H = jωЄE & X E = - jωμH Considering propagation only along z-axis z x E - j 2 = X ( ) y j and H Z = 0 & H = 0 Transverse Magnetic (TE) Waves TE Waves have no electric field vector in the direction of propagation but has magnetic field vector in the direction of propagation. Notes for the Instructor Explain that above equations are reduction of the equations from the previous slide Considering propagation only along z-axis z y H - j 2 = E X ( ) x j and Z = 0 & H = 0 © Copyright 2007 Agilent Technologies

TEM Wave between parallel plates y x z Ground Plane in yz-plane, x=0 W d Rectangular Metal Patch in yz-plane, x=d TEM Wave along z-axis e(x,y) = - (V / d) x E(x,y,z) = = - (V / d) e e(x,y) e -j H(x,y,z) = - j 1 X E(x,y,z) = = = E(x,y,z) / H(x,y,z) = V p = 1 Line Impedance of Parallel Plate Structure for TEM Wave V = - E(x,y,z). dx = (V / d) e dx = V e x=0 x=d I = H . dy = (V W/ d) e y=0 y=W Z = V / I = d / W Attenuation Constant ( ) due to dielectric loss (tan ) - = ( tan ) / 2 Figure 5: Parallel Plate Structure (continuous to infinity along z-axis) Notes for the Instructor Point at various parameters of TEM Wave between parallel plates extending to infinity along z-axis. Mention that propagation is only along z-axis Differentiate between characteristic impedance in the medium and characteristic impedance of the line © Copyright 2007 Agilent Technologies

TM Wave between parallel plates y x z Ground Plane in yz-plane, x=0 W d Rectangular Metal Patch in yz-plane, x=d TM Wave along z-axis TM Mode 0 0 n E = 0 H = A Cos n x d e ( ) - j Z z_n 2 -j Ez = e e =A Sin n x d e Propagation Constant n ( ) Mode Cut-off Frequency cut-off 1 Phase Velocity p_n V Wave Impedance of TM Mode TM 00 n Z Power Transmitted (given by Poynting Vector) P W A For n=0 4 For n>0 Attenuation Constant( ) d_n tan( ) Notes for the Instructor a) Explain various parameters © Copyright 2007 Agilent Technologies

TE Wave between parallel plates y x z Ground Plane in yz-plane, x=0 W d Rectangular Metal Patch in yz-plane, x=d TE Wave along z-axis = 0 E X H n = 1,2,3... TE Mode 0 0 n Sin n x /d e ( ) -j Z z_n = - jB 2 x_n j B = B Cos n x /d e Propagation Constant n ( ) Mode Cut-off Frequency cut-off 1 Phase Velocity p_n V Wave Impedance of TE Mode TE 00 n Z Power Transmitted P WB 4 For n>0 Attenuation Constant ( ) d_n tan( ) Notes for the Instructor a) Explain various parameters © Copyright 2007 Agilent Technologies

© Copyright 2007 Agilent Technologies Session Summary In this session We showed the basic structure of a microstrip patch and various shapes of a patch antenna We showed various methods to feed a rectangular patch antenna We looked at the nature of TEM, TM and TE waves in free space and between parallel plates Notes for the Instructor a) Conclude by summarizing these points © Copyright 2007 Agilent Technologies