1. 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

2. © 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

3. 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

4. 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

5. 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

6. © 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

7. 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

8. TEM Wave between parallel platesy 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

9. TM Wave between parallel platesy 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

10. TE Wave between parallel platesy 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

11. © 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