Transcript Modular RF for Embedded Sys.

Modular RF for Embedded System
EE 281
November 25, 2002
Ying-zong Huang
Special Embedded Needs
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Portable
Self-contained
Small
Real-time remote
operation
Wireless data transfer
(also portable power…)
RF: Not Trivial
Modular RF
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Faster TTM for systems with a radio
component
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Cordless telephone
Baby monitors
OEM’s
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Bluetooth-enabled
802.11-enabled
Modular RF
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No (or very very few) external components
Linx Technologies:
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http://www.linxtechnologies.com
Module + Antenna = Wireless
RF modules (miniboards)
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LC Series (SAW, 315, 418, 433 MHz)
KH Series (with Encoder/Decoder)
HP-2 Series (FM/FSK, Multi-channel, 900 MHz)
Linx LC Series - Transmitter
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2.7V–5.2 VDC
Direct Serial
Interface
(Digital) data rates
up to 5 Kbps
Up to 300 feet
Linx LC Series - Receiver
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Similar features as Transmitter
Linx LC Series - Modulation
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Carrier Present/Carrier
Absent modulation
Saves power when
sending ‘0’
Takes advantage of FCC
rules
Easy to understand
Encoding not provided by
LC Series: Add your own
protocol
(By way of Pascal Stang: http://www.procyonengineering.com/hardware/linxrf.html)
Linx LC Series - Radiation
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Short wire or matched
transmission line to antenna
Antenna mounting
Antenna (nominal) length
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Quarter wave: L [inches] =
234 / F [MHz]
Antenna Styles:
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Whip
Helical
Loop
Stub
Just a wire
Linx LC Series - Other Issues
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VSWR – voltage standing
wave ratio, ideal form:
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Rho is the reflection coefficient
(RC) going into the antenna:
Modular RF - Other Issues
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More radiation, more reliable link
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But maybe not too much
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♦
Ground plane
Clean power supply
Note EMI/FCC issues