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).