Modular RF for Embedded System

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
• Cordless telephone
• Baby monitors
• OEMs
• Bluetooth-enabled
• 802.11-enabled

5
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)

6
Linx LC Series - Transmitter

• 2.7V5.2 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 http//www.procyonenginee
ring.com/hardware/linxrf.html)
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

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