ELCT564
Spring 2012
4/13/2015
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Introduction to Microwave Engineering
RF and microwave engineering covers frequency from 100 MHz to 1000GHz
VHF
RF frequencies: 30-300 MHz
RF frequencies: 300-3000 MHz UHF
Microwave frequencies: 3-300 GHz
mmwave frequencies: 30-300 GHz
THz frequencies: >300 GHz
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Why study them separately?
Region of EM spectrum where neither standard circuit theory (Kirchoff) nor
geometrical (ray) optics can be directly applied.
Because of short wavelength, lumped element approximation cannot be used.
Need to treat components as distributed elements: phase of V or I changes
significantly over the physical length of a device
For optical engineering λ << component dimensions
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Approach
Solve Maxwell’s equations and apply boundary conditions for the specific
geometry. Hard to do for every device!!!!
Analytical solutions exist only for some basic geometries and often must use
numerical techniques
In a lot of cases we can find V, I, P, Zo by using transmission line theory (use
equivalent ckts)
Not a lot of info on EM fields but sufficient for microwave and RF circuits
As f increases need to use full-wave tools
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Why study microwaves?
More bandwidth or information can be realized at higher frequencies –
essential for telecommunications
Microwave/mm-wave travel by line-of-sight and are not bent by the ionosphere
(such as AM signals)
Most of them not affected by atmospheric attenuation (space com. or secure
terrestrial com.)
Higher resolution radars are possible at higher frequencies
Various atomic & molecular resonances occur mwave/mm-wave/THz
frequencies which are important for remote sensing, radio astronomy,
spectroscopy, medical diagnostics, sensing of chemical.biological agents
Can get a very good salary as an RF/mmwave engineer.
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Applications
Patriot Defense System
Surface Radar
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Applications
Global Communication
Systems for the Army
Air Traffic Control
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Applications
Global Positioning System
Personal Communication Systems
Wireless LANs
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Applications
Monolithic Microwave/mm-wave
Integrated Circuits
MRI
Remote Sensing
Earth and Space Observations
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Applications
Cable and Satellite TV
Aircraft and Automobile
Anti-Collision Radar
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Application
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Frequency
AM broadcast
535-1605 KHz
Shortwave radio
3-30 MHz
VHF TV (2-4)
54-72 MHz
VHF TV (5-6)
76-88 MHz
FM broadcast
88-108 MHz
VHF TV (7-13)
174-216 MHz
UHF TV (14-83)
470-810 MHz
Cell phones (US)
824-849, 869-894 MHz
GPS
1227, 1575 MHz
PCS (US)
1850-1990 MHz
Microwave Ovens
2.45 GHz
Bluetooth
2.4 GHz
802.11a (wireless LAN)
5.8 GHz
Direct Broadcast Satellite 12.2-12.7 GHz
Services
ELCT564
Collision avoidance radar
77 GHz
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Emerging High Frequency
Applications
94 GHz
Personal Communications
High speed microprocessor
Satellite
60-G Wireless
HDMI
Point-to-point/Multi-point links
Mobile Computing/WLAN
Adaptive cruise control
radar for automobiles
DVD player
Automotive Radar
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Home Networks of the Future
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Wireless Market Segmentation
Access to PSTN
Connected to
Wireless Service
Providers
Home Office
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Global
Enables Video
Deployment
Applications
Access to
Access to
Corporate Networks
Internet Service
Providers
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Wireless Engine
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RF/Wireless Education: Multi-Disciplinary
System Integration
Basic Electromagnetics
 Integration
Device/Circuit Design
Concepts

Advance CAD Techniques

Current Technologies and Design Rules

Modern Experimental Analysis for Circuits and Subsystems
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Transmission Lines
“Heart” of any RF/Wireless System
Coaxial Cable
Parallel-Plates
Twisted-Pair
Rectangular Waveguide
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Transmission Lines
Microstrip
Coplanar Waveguide
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Substrate Materials
• Semiconductors
• Organic
• Ceramics
• Glass
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Silicon
11.8
GaAs
13
FR-4
4.7-4.9
Polyimide
3.5
Alumina
9.4-10
Quartz
3.5
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Advanced Printed Wiring
Board Technology
Transmission Line
Equivalent Circuit
i(z,t)
L Dz
R Dz
i(z+Dz,t)
+
+
u(z,t)
u(z+Dz,t)
C Dz
G Dz
-
Dz
Microwave Bands
Name
Frequency
L
1.12-1.7 GHz
S
2.6-3.95 GHz
C
5.85-8.2 GHz
X
8.2-12.4 GHz
Ku
12.4-18 GHz
K
18-26.5 GHz
Ka
26.5-40 GHz
U
40-60 GHz
V
50-75 GHz
W
75-110 GHz
EM Theory Review
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Maxwell’s Equations
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Fields in Media
Loss tangent
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Fields at General Material Interface
Dn2
Et2
Ht2
Dn1
Et1
Bn2
.....
Ht1
Bn1
Dn2
Medium 2
.....
h
Medium 1
Dn1
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Fields at General Material Interface
h
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Et2
Medium 2
Et1
Medium 1
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Fields at a Dielectric Interface
Fields at the Interface with a Perfect Conductor
Fields at the Interface with a Magnetic Wall
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The Helmholtz Equation
Source-free, linear, isotropic, homogeneous
Wave Equation/The Helmholtz Equation
Propagation constant/phase constant/wave number
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Plane Waves in a Lossless Medium
Assuming electric filed only have x component and uniform in x and y directions
What is the speed of light?
Phase velocity
Wavelength
Intrinsic
Impedance
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Plane Waves in a General Lossy Medium
Complex propagation constant:
Attenuation constant and phase
constant
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Plane Waves in a General Lossy Medium
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Plane Waves in a Good Conductor
The amplitude of the fields in the conductor decays
by an amount 1/e (36.8%) after traveling a distance
of one skin depth
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8.14×10-7m
6.60×10-7m
7.86×10-7m
6.40×10-7m
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Summary of Results for Plane Wave
Propagation in Various Media
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General Plane Wave Solutions
i=x,y,z
Separation of variables
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Circularly Polarized Waves
Polarization of a plane wave refers to the orientation of the electric field vector: fixed
direction or change with time.
The plane waves which have their electric filed vector pointing in a fixed direction are
called linearly polarized waves.
Electric field polarization for (a) Right Hand Circularly Polarized (RHCP) and (b) Left Hand
Circularly Polarized plane waves.
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Energy and Power
A source of electromagnetic energy sets up fields that store electric and
magnetic energy and carry power that may be transmitted or dissipated as loss.
The time-average stored electric energy in a volume V
The time-average stored magnetic energy in a volume V
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Energy and Power
Poynting Vector (P0): power flow
out of the closed surface S.
Power Ps delivered by the sources
Power dissipated in the volume
due to conductivity, dielectric and
magnetic losses (Pl)
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Plane Wave Reflection from A Media
Interface
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Example
Consider a plane wave normally incident on a half-space of copper. If f=1GHz,
compute the propagation constant, intrinsic impedance, and skin depth for the
conductor. Also compute the reflection and transmission coefficients (Copper’s
conductivity is 5.813×107S/m).
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