1. Modular RF for Embedded System
EE 281
November 25, 2002
Ying-zong Huang

2. Special Embedded Needs
Portable
Self-contained
Small
Real-time remote operation
Wireless data transfer
(also portable power…)

3. RF: Not Trivial

4. Modular RF Faster TTM for systems with a radio component OEM’s
Cordless telephone
Baby monitors
OEM’s
Bluetooth-enabled
enabled

5. Modular RF No (or very very few) external components
Linx Technologies:
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)
For embedded project using RF only incidentally
Different packages etc.
Transmitter/Receiver in one

6. Linx LC Series - Transmitter
2.7V–5.2 VDC
Direct Serial Interface
(Digital) data rates up to 5 Kbps
Up to 300 feet

7. Linx LC Series - Receiver
Similar features as Transmitter

8. 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:

9. 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

10. Linx LC Series - Other Issues
VSWR – voltage standing wave ratio, ideal form:
Rho is the reflection coefficient (RC) going into the antenna:

11. Modular RF - Other Issues
More radiation, more reliable link
Ground plane
Clean power supply
But maybe not too much
Note EMI/FCC issues ♦