supported by technical benchmarks and industry standards.
- Structural Design and Materials
A. Semi-Rigid Coaxial Cables
Outer Conductor: Made from solid copper, aluminum, or stainless steel tubing, cold-formed into a permanent shape.
Dielectric: Precision-machined PTFE (polytetrafluoroethylene) or extruded FEP (fluorinated ethylene propylene) for stable εᵣ (2.0–2.1).
Inner Conductor: Silver-plated copper-clad steel (SPCCS) or beryllium copper for rigidity and low loss.
Key Feature: Non-flexible once shaped; maintains geometry under vibration and thermal stress.
B. Standard Coaxial Cables
Outer Conductor: Braided copper or aluminum foil + tinned copper braid (e.g., RG-58, RG-213).
Dielectric: Foam polyethylene (PE) or solid PVC for flexibility.
Inner Conductor: Stranded or solid copper.
Key Feature: Highly flexible; tolerates repeated bending and re-routing.
- Electrical Performance Comparison
Parameter Semi-Rigid Cables Standard Cables (e.g., RG-58)
Frequency Range DC–110 GHz DC–3 GHz
Insertion Loss 0.05 dB/cm @ 10 GHz 0.3 dB/cm @ 1 GHz
VSWR <1.15:1 up to 40 GHz <1.5:1 up to 1 GHz Phase Stability ±0.5° over -55°C to +125°C ±5° over -40°C to +85°C Shielding Effectiveness >120 dB @ 10 GHz 60–90 dB @ 1 GHz
Example: 3.0mm semi-rigid vs. RG-58 (5.0mm OD).
- Mechanical and Environmental Properties
A. Semi-Rigid Cables
Bend Radius: Pre-shaped during manufacturing; cannot be re-bent without tools.
Vibration Resistance: Withstands 20 g RMS (MIL-STD-167).
Temperature Range: -65°C to +200°C (PTFE dielectric).
Outgassing: Compliant with NASA TML <1% (critical for vacuum environments).
B. Standard Cables
Bend Radius: Dynamic, 10× OD (e.g., RG-58: 50mm radius).
Vibration Resistance: Limited to 5 g RMS (IEC 61196-1).
Temperature Range: -40°C to +85°C (PVC jacket).
Flammability: UL 94 V-2 (vs. semi-rigid’s UL 94 V-0).
- Key Applications
A. Semi-Rigid Coaxial Cables
Radar/EW Systems: Phase-stable interconnects in AESA (Active Electronically Scanned Array) radars.
Satellite Payloads: Low PIM (<-160 dBc) for high-power transponders.
Medical MRI: Non-magnetic variants (CuNi9Sn2) for 7T imaging systems.
5G mmWave: 1.85mm cables in 28/39 GHz beamforming networks.
B. Standard Coaxial Cables
Consumer Electronics: HDMI, Wi-Fi routers, and TV antennas (RG-6).
Automotive Infotainment: FAKRA connectors for GPS/radio.
Industrial Sensors: Flexible routing in PLCs and robotics.
Low-Cost RF Links: RFID readers, amateur radio (RG-8X).
- Cost and Installation Considerations
Factor Semi-Rigid Cables Standard Cables
Material Cost $10–50/m (Cu/SS tubing) $0.5–5/m (braided)
Installation Tools Mandrel benders, CNC cutters Hand crimpers, strippers
Labor Time High (precision shaping) Low (plug-and-play)
Reusability None (geometry fixed) Fully reusable
- Case Studies
A. Aerospace: Semi-Rigid vs. RG-400 in UAVs
A military UAV required RF links for its 15 GHz SAR (Synthetic Aperture Radar).
Semi-Rigid (0.047″ SS): Achieved 0.1 dB/cm loss and survived 15 g vibration.
RG-400 (PTFE braided): Suffered 0.4 dB/cm loss and shield fraying after 100 flight hours.
Result: Semi-rigid reduced system noise by 40%.
B. Telecom: RG-213 vs. Semi-Rigid in 4G Macro Cells
A tower-mounted 2.6 GHz RRH (Remote Radio Head) required jumper cables.
RG-213: 1.2 dB/m loss led to 15% coverage drop.
Semi-Rigid (4.1mm Cu): 0.3 dB/m loss improved cell edge throughput by 25%.
- Standards and Certifications
Standard Semi-Rigid Cables Standard Cables
MIL-STD-348 RF connector interfaces Not applicable
IEC 61196-1 Flex testing exemption Mandatory flex cycles
RoHS/REACH Lead-free soldering PVC alternatives
ASTM D4566 Shield continuity testing Basic continuity checks
- Future Trends
Hybrid Designs: Semi-flexible cables with localized rigid segments (e.g., Rosenberger’s SFT series).
Additive Manufacturing: 3D-printed semi-rigid cables with graded dielectric constants.
Sustainability: Recyclable FEP jackets replacing PTFE in standard cables.
