ELCT564 Spring 2012
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Transcript of ELCT564 Spring 2012
ELCT564 Spring 2012
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Introduction to Microwave Engineering
RF and microwave engineering covers frequency from 100 MHz to 1000GHz
RF frequencies: 30-300 MHz VHFRF frequencies: 300-3000 MHz UHFMicrowave frequencies: 3-300 GHz
mmwave frequencies: 30-300 GHzTHz 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.
Patriot Defense System
Surface Radar
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Applications
Global CommunicationSystems 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
Applications
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Cable and Satellite TV
Aircraft and Automobile Anti-Collision Radar
Applications
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Application 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 Services
12.2-12.7 GHz
Collision avoidance radar 77 GHz04/21/23 11ELCT564
Emerging High Frequency Applications
Satellite
High speed microprocessor
Personal Communications
Mobile Computing/WLAN
Automotive Radar
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DVD player
60-G WirelessHDMI
Adaptive cruise control radar for automobiles
94 GHz
Point-to-point/Multi-point links
Home Networks of the Future
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Connected toConnected to
Home OfficeHome Office
Access to Access to
Corporate NetworksCorporate Networks
Wireless Market Segmentation
Access toAccess to
Internet Service Internet Service Providers Providers
Enables VideoEnables Video
ApplicationsApplications
Wireless Service Wireless Service ProvidersProviders
Access to PSTNAccess to PSTN
Global Global
DeploymentDeployment
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Wireless Engine
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RF/Wireless Education: Multi-Disciplinary
Device/Circuit DesignBasic Electromagnetics
System Integration
Integration 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
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
L z R z
C z
G z
+
-
u(z,t) u(z+z,t)
+
-
z
i(z,t) i(z+z,t)
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
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Loss tangent
Fields at General Material Interface
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Bn2
Bn1
Ht2
Ht1
Et2
Et1
Dn2
Dn1
.....
Medium 1
Medium 2
Dn2
Dn1
h .....
Fields at General Material Interface
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Et2
Et1
hMedium 2
Medium 1
Msn
Fields at a Dielectric Interface
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Fields at the Interface with a Perfect Conductor
Fields at the Interface with a Magnetic Wall
The Helmholtz Equation
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Source-free, linear, isotropic, homogeneous
Wave Equation/The Helmholtz Equation
Propagation constant/phase constant/wave number
Plane Waves in a Lossless Medium
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Assuming electric filed only have x component and uniform in x and y directions
Phase velocity
Wavelength
What is the speed of light?
Intrinsic Impedance
Plane Waves in a General Lossy Medium
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Complex propagation constant:
Attenuation constant and phase constant
Plane Waves in a General Lossy Medium
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Plane Waves in a Good Conductor
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8.14×10-7m6.60×10-7m7.86×10-7m6.40×10-7m
The amplitude of the fields in the conductor decays by an amount 1/e (36.8%) after traveling a distance of one skin depth
Summary of Results for Plane Wave Propagation in Various Media
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General Plane Wave Solutions
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i=x,y,z
Separation of variables
Circularly Polarized Waves
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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.
Energy and Power
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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
Energy and Power
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Power Ps delivered by the sources
Poynting Vector (P0): power flow out of the closed surface S.
Power dissipated in the volume due to conductivity, dielectric and magnetic losses (Pl)
Plane Wave Reflection from A Media Interface
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Example
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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).