An Experimental Microwave Data Link

for 10-Megabit Ethernet

Designed and documented by John Miles KE5FX ( ke5fx@qsl.net)

[Note: this page is a snapshot of KE5FX's work to date as of Feb. 1st, 2000.  Please see KE5FX's page for the
latest updates.]

Project Description

 
Updated January 12, 2000: The OrCAD schematics have been updated with the tuning meter and FSK modulator circuit corrections from the Technical Correspondence section.

• Introduction
• System Architecture and Limitations
• Point-to-Point Gunnplexer Communications
• Operation without Ethernet Collision-Handling
• Connectivity with Ethernet Hardware via 10-Mbit/s Attachment Unit Interface (AUI)
• Availability of an Unobstructed Line-of-Sight Path 
• Design and Construction Notes
• Antenna Considerations
• Microwave Transceiver Modules
• IF Strip
• FSK Demodulator
• Output Buffer
• FSK Modulator
• Tuning and AFC Considerations
• Tuning/Fault Meter Circuit
• S-Meter Circuit and Signal Strength Interpretation
• Power Supply, Shielding, and Decoupling Considerations 
• Alignment and Testing
• Gunnplexer Frequency Calibration
• FSK Demodulator Calibration
• FSK Modulator Deviation Adjustment
• Testing and Troubleshooting 
• Component and Data Sources
• RF Safety and Regulatory Issues
• Acknowledgements
• Technical Correspondence

 

Photographs

• Transceiver unit mounted atop a tripod on apartment balcony
• A closer view of the tripod-mounted unit, showing separate chassis for modulator and receiver circuits
• Signal path, approximately 50 meters. Remote unit is located inside office by wooden crate on sidewalk.
• Link control unit with its associated 10BaseT hub
• A closer view of the link control unit, showing signal-strength and tuning indicators
• Inside the link control unit, showing power supply and meter wiring
• Inside the transceiver unit, with subassembly covers in place
• Inside the IF amplifier subassembly, revealing MAR-6 MMICs and filters
• Inside the MC13155-based FSK demodulator subassembly
• A closer view of the MC13155 and its associated components
• Inside the Ethernet AUI interface and Gunn varactor modulator subchassis

 

Waveforms

• Ethernet signal as transmitted from AUI Tx port, before filtering and amplification
• Amplified and filtered Ethernet signal as applied to Gunnplexer varactor diode
• Received Ethernet signal as delivered to AUI Rx port, after demodulation and filtering
• Spectrum analysis of 10.178 GHz output from Gunnplexer, modulated by 10-Mbit/s Ethernet traffic
• Qualitative indication of excessive packet loss in early prototype

 

Schematics

• System block diagram
• IF strip and Gunnplexer assemblies
• FSK modulator / AFC buffer assembly
• FSK demodulator assembly
• Output buffer circuit
• Tuning / S-meter circuits
• Schematics above in OrCAD format

 

PC Boards

• PC board design (untested, courtesy of Luis Yanes EB7GWL -- all comments regarding these boards should be directed to Luis)