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Transcript
Modular RF for Embedded System
EE 281
November 25, 2002
Ying-zong Huang
Special Embedded Needs




Portable
Self-contained
Small
Real-time remote
operation
Wireless data transfer
(also portable power…)
RF: Not Trivial
Modular RF

Faster TTM for systems with a radio
component
–
–

Cordless telephone
Baby monitors
OEM’s
–
–
Bluetooth-enabled
802.11-enabled
Modular RF


No (or very very few) external components
Linx Technologies:
–
–

http://www.linxtechnologies.com
Module + Antenna = Wireless
RF modules (miniboards)
–
–
–
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




2.7V–5.2 VDC
Direct Serial
Interface
(Digital) data rates
up to 5 Kbps
Up to 300 feet
Linx LC Series - Receiver

Similar features as Transmitter
Linx LC Series - Modulation





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



Short wire or matched
transmission line to antenna
Antenna mounting
Antenna (nominal) length
–

Quarter wave: L [inches] =
234 / F [MHz]
Antenna Styles:
–
–
–
–
–
Whip
Helical
Loop
Stub
Just a wire
Linx LC Series - Other Issues

VSWR – voltage standing
wave ratio, ideal form:

Rho is the reflection coefficient
(RC) going into the antenna:
Modular RF - Other Issues

More radiation, more reliable link
–
–

But maybe not too much
–
♦
Ground plane
Clean power supply
Note EMI/FCC issues