Introduction to RF and Microwave Systems

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Introduction to RF and Microwave Systems
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RF and Microwave Frequency Bands

• RF (radio frequency) is used to indicate the
  frequency band from hundreds of MHz to about 3
  GHz
• Microwave frequencies start from 300 MHz and goes
  up to 30 GHz, ( wavelength of 1m to 0.01m)
• The frequency bands above 30 GHz is called
  Millimeter waves, and extend up to 300 GHz. Its
  technology is very similar to microwaves.

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Electromagnetic Spectrum
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Electromagnetic Spectrum (comparable)
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What is different about the RF/Microwave band?

• Circuit theory / transmission lines /
  electromagnetics all needed, because
• The size of the circuit (lets call it d) for
  RF and microwave circuits
• Question what relationship between d and
  exists for (a) low frequency circuits (kHz
  range), and (b) optical circuits (where the
  wavelength is on the order of µm), keeping in
  mind that the circuits themselves are all on the
  order of cm?

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Advantages of the use of higher frequencies

• Larger instantaneous BW for much information,
• Higher resolution for radar, imaging and sensing,
  bigger doppler shift,
• Reduced dimensions for components,
• Less interference from nearby applications
• Higher speed for digital systems, signal
  processing, data transmission
• Less crowded spectrum
• Difficulty in jamming (military)

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Disadvantages of the use of higher frequencies

• More expensive components,
• Higher atmospheric losses,
• Reliance on GaAs instead of Si technology
• Higher components losses, lower output powers
  from active devices,
• Less accurate design tools, less mature
  technologies.

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RF and Microwave Applications

• Wireless Communications (space, cellular phones,
  cordless phones, WLANs, Bluetooth, satellites
  etc.)
• Radar and Navigation (Airborne,vehicle, weather
  radars, GPS, MLS, imaging radar etc.)
• Remote sensing (Meteorology, mining, land
  surface, aviation and marine traffic etc.)
• RF Identification (Security, product tracking,
  animal tracking, toll collection etc.)
• Broadcasting (AM,FM radio, TV etc.)

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RF and Microwave Applications

• Automobiles and Highways (Collision avoidance,
  GPS, adaptive cruise control, traffic control
  etc.)
• Sensors (Temperature, moisture sensors, robotics,
  buried object detection etc.)
• Surveillance and EW (Spy satellites, jamming,
  police radars, signal/radiation monitoring etc.)
• Medical (MRI, Microwave Imaging, patient
  monitoring etc.)
• Radio Astronomy and Space Exploration (radio
  telescopes, deep space probes, space monitoring
  etc.)
• Wireless Power Transmission (Space to space,
  space to ground etc. power transmission)

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Radiated Power and Safety

• Organic tissue absorbs RF and microwave energy
  and converts it to heat (e.g. Microwave oven)
• This is not a good thing when the tissue is you!
• Heating is dangerous to areas such as brain,
  eyes, and stomach organs
• Radiation may cause cataracts, cancer, and
  sterility
• ANSI/IEEE standard sets safety standard for
  exposure limits (e.g. limited to 10 mW/cm2 above
  15 GHz where radiation is absorbed by the skin)
• Handheld cell phones limited to maximum radiated
  power of 0.76 W, while base stations are limited
  to 500 W.

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The main purpose of the course is to provide the
following questions

• At what upper frequency does conventional circuit
  analysis become inappropriate?
• What characteristics make the high-frequency
  behavior of electric components so different from
  low-frequency behavior?
• What new circuit theory has to be employed?
• How is this theory applied to practical design of
  high-frequency analog circuits?

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Sample Tranceiver
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Power Amplifier Circuit
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Power Amplifier PCB layout
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RF Behavior of Passive Components
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Lumped(discrete) or distributed elements
Inductor
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