design techniques for high power rf coaxial cable...

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Design Techniques for High Power RF Coaxial Cable Assemblies

Tony Martiniello

Chief Technology Officer

TRU Corporation © 2012. All rights reserved.

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Primary Considerations

Primary

Considerations

Application

Prioritizing-Trade-offs

Performance

Electrical-Mechanical-Environmental

Cable-Connector-Attachment

Component Design


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Typical High Power RF Applications

Semiconductor

Wafer Fabrication Equipment

Broadcast

Industrial Equipment

Medical Imaging

EMI / RFI Testing

Aerospace


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Application Consequences

Dielectric material

Center conductor

Dielectric


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Performance Assessment / Analysis

ELECTRICAL MECHANICAL ENVIROMENTAL

Frequency Flexibility Temperature

Attenuation Bend Radius Moisture

RF Power Size Altitude

Shielding Weight Radiation

Phase Stability Crush/Pull Strength Fluid Resistance


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RF Coaxial Cable Design

Typical Coaxial Cable Constructions Single shield, extruded (PE) dielectric Double shield, extruded (PE or PTFE) dielectric VP = 66% VP = 66% to 70%

Expanded PTFE dielectric, strip & round shields Corrugated Coaxial Cable VP = 76 to 82 VP = 80 to 85


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Cable Constructions and Power

Typical Center Conductor Constructions

Solid Stranded (7) Stranded (19)

Attenuation Lowest Moderate Highest

Power Highest Moderate Lowest

Flexibility Lowest Moderate Highest

Torque Highest Moderate Lowest

Cost Lowest Moderate Highest

Typical Dielectric Construction

Typical Jacket Constructions

PE PE PTFE PTFE

Solid Foamed Solid Expanded

Attenuation Best Moderate Low Best

VP Lowest Highest Low High

Flexibility Lowest Low Moderate Best

Temp Low Low Moderate Best

Crush Best Low High Moderate

Weight High Low Moderate Low

Cost Low Low Moderate Highest

PVCPoly-

F/G Braid FEP Corrugatedurethane

Flexibility Good Good Best Good Low

Temp Low Low High High High

Moisture Good Good Poor Good Good

Chemicals Low Low Low High Low

Flame Good Low Moderate Good Good

Cracking Worst Low N/A Good Low

Cost Low Low Highest Moderate Moderate


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RF Coaxial Cable Reference Guide


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Cable Power Capabilities


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Selecting a Connector Interface


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RF Connector Design

• Material Selection

– Common Dielectric - Teflon®

– High Power Options – Fluoroloy, BN

• Construction

– Mechanical Captivation vs. Epoxy

– Swept vs. Miter Angles

• Geometry

– Line Size Match - Connector & Cable

– Telescope / Overlap Insulators


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RF Connector Power Handling


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Cable / Connector Attachment Design

• Electrical

– Matched line size of cable/connector

– Voltage arc protection

• Mechanical

– Pull / torque strength (belt & suspenders)

– Clamp attachment, TRUtie™ method

• Environmental

– Weather

– Altitude


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Summary

• Application Review

– Understand as much as possible of actual operating environment

or proceed at your own risk

• Performance Assessment

– You can’t have it all – prioritize the “must have” & “nice to have”

• Design Considerations

– Holistic Design Approach: Cable – Connector - Attachment


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High Power RF Coax Assemblies

Conclusion:

Proper design considerations can result in a flexible RF cable

assembly solution for high power application as high as 50 – 100 kW.


design techniques for high power rf coaxial cable...

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