Practical Microwave Beam Concepts

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Practical Microwave Beam Concepts

• Jasper Nance

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Outline
1. What is a microwave?
2. How do you make microwaves?
3. How do you send microwaves?
4. How do you recieve microwaves?
5. Can it be done?
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What Are They?
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How do you make em
Historical Tubes
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How do you make em
Operation
Phase 1 Production and acceleration of an
electron beam Phase 2 Velocity-modulation of
the electron beam Phase 3 Forming of a
Space-Charge Wheel Phase 4 Giving up energy
to the ac field
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How do you make em
Operation
Phase 1 Production and acceleration of an
electron beam
Phase 2 Velocity-modulation of the electron beam
No B Field
Small B Field
Too much B Field
Cutoff ( just right!)
HF Electric Field
Electron Paths
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How do you make em
Operation
Phase 4 The Electron takes the DC field energy
and gives it to the AC field
Phase 3 Forming of a Space-Charge Wheel
Electron Bunching and Velocity Modulation in
response to AC field
Resulting Path of the Electron
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How do you make em
Operation
Resonant Cavities
Anode
Cathode
Filament Leads
Strapping
Pickup Loop
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How do you make em
Practical Considerations
Output Waveguide
Output Loop
Possible Plate Construction Patterns
a) slot- type b) vane- type c) rising sun- type
d) hole-and-slot- type
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How do you send em?
Step1 Use waveguide horn to create a spherically
diverging field
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How do you send em?
Step2 Feed it into a parabolic dish to create a
planar field
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Sidenote Beam Dispersion
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How do you receive em?
Step1 Receive with another parabolic dish
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How do you receive em?
Dipole
Helical
Step2 Use dish to concentrate signal onto
receiving element
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How do you receive em?
Step3 Couple Signal to a HF Bridge Diode
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How do you receive em?
Step3 Couple Signal to a HF Bridge Diode
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How do you receive em?
Step4 Feed into a buck (boost?) converter
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Real World Example
Wifi signal powers bike lamp LED!
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Questions?