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Transcript of Learning Attitude “ A fool thinks himself to be wise, but a wise man knows himself to be a...
Learning Attitude
“A fool thinks himself to be wise, but a wise man knows himself to be a fool”.
-William Shakespeare
Antenna Selection
An Antenna is one of the most critical junctions in any RF communication system. It’s performance determines the quality and the continuity of your data flow in both directions.
Common understanding between the system designer, system integrator, the user and the antenna supplier regarding antenna performance.
Top Ten Antenna Questions
What is the operating frequency range of the system? How much gain is required? What kind of radiation pattern is desired? What is the maximum allowable VSWR? What polarization is required? What type of connector interface is required? How much power will the antenna have to handle? Where will the antenna be mounted? Is a radome required? What is the lifetime of the antenna?
What is the operating frequency range of the system?
Before you can specify an antenna, you must know the approximate center frequency and the bandwidth over which it must operate.
Frequency is dictated by the application and the allocations available.
How much gain is required? Antenna performance is primarily established
by its gain . Most commercial antenna suppliers specify gain in
dBd (gain over a half wave dipole). Another reference at microwave frequencies is
dBi (gain over isotropic radiator) a theoretical antenna that radiates equally well in all directions.
e.g Waveguide without Horn
Common communicationantenna types
Type Typical Gain ranges(dBd)
Dipole Omni
Gain Omni Mobile Whips
Corner ReflectorLog Periodic
HornHelix
Microstrip- patchYagi
PanelParabolic Dish
00
3 to 12-0.6 to +5.5
4 to 103 to 8
5 to 125 to15 3 to 153 to 20 5 to 2010 to 30
What kind of radiation pattern is desired? Define the regions for distribution of power. Omni-pattern but higher gain with sector
antennas. What is the maximum allowable VSWR? VSWR represents the degree with which an
antenna is “matched” to the system impedance. What polarization is required? Many systems are challenged because
interfere with adjoining systems.
What type of connector interface is required? How much power will the antenna have to handle?
Type “N”,TNC and BNC connectors are preferred at higher frequencies because they maintain a good VSWR.
If small size and low power operation from 1-10GHz is anticipated, the SMA connector may be preferred.
Inform the antenna supplier the peak power level and comparison of energy levels.
Where will the antenna be mounted? Is a radome required?
The real impact comes when assessing the total environment and whether the antenna will perform and survive once installed.
What is the lifetime of the antenna? The quality of the antenna will match the
quality of the relationship between you and the one who pays the bills.
Microstrip patch antenna designCreate Substrate
Select the menu item Draw > Box
• enter the box position
– X: -7.0, Y: -4.5, Z: 0.0,
• enter the opposite corner of the box
– dX: 12.0, dY: 9.0, dZ: 0.32
Create the FeedSelect the menu item Draw > Rectangle
• enter the rectangle position
– X: -5.0, Y: -0.2475, Z: 0.0
• enter the opposite corner of the rectangle:
– dX: 7.0, dY: 0.495, dZ: 0.0
Dipole design
Pole 1 Dimensions
Center position : 0 ,0 ,0.5
Start position : 0 ,-1 ,0.5
Height=30
Pole2 Dimensions
Center position : 0 ,0 ,-0.5
Start position : 0 ,1 ,-0.5
Height= -30
References
www.astronwireless.com/topic-archives-selecting-antennas.asp
HFSS user manual www.antenna.be/art4.html