Introduction

Mini-Circuits FLC Series test cables are specifically designed and manufactured for use in stringent test lab environments where cables often undergo bending during normal use. This can result in a change of performance vs. flexure. To demonstrate performance change vs. flexure, Mini-Circuits has developed a controlled method of test and evaluated our FLC3FT-SMSM+ model by applying various bend radii to a 3ft cable and measuring the change in insertion loss, insertion phase, and VSWR versus flexure normalized to the reference position.

Qualification Testing – Electrical Performance vs. Flexure Test

Cable Flexure Test Fixture

Fixture (B85-L26000-00) used in the setup is designed and built by MCT specifically for the performance vs. flexure test. The fixture as shown in Figure 1 below has two adjustable arms to support the connector ends when connected to Agilent PNA-X network analyzer at ports 1 & 2. A 3ft flexible cable is wrapped around a 4-inch mandrel which slides along the scaled bar creating the specified bend radius.

Figure 1: Cable flexure test cable (MCL P/N: B85-L26000-00).

Cable Flexure Test Fixture Setup

Figures 2 to 5 below show the flexure test setup used in assessing the electrical performance vs. flexure. This flexure test fixture applies a symmetric bend radius to apply a stress on the cable.

Figure 2: 3ft. flexible test cable attached to the cable flexure test fixture at its reference start position.
Figure 3: 3ft flexible test cable with a bend radius of 10″.
Figure 4: 3ft flexible test cable with a bend radius of 3.25″.
Figure 5: 3ft flexible test cable with a bend radius of 2.40″.

Performance Change vs. Flexure Data

Figure 5 below shows the typical absolute values normalized to the reference position 0, for each electrical performance from DC 26 GHz measured using a 3ft cable.

Figure 6

Note: Cable flexure test fixture specifically designed to take measurements using Agilent PNA-X network analyzer at port-1 & port-2.

Figure 7: Change in insertion loss with flexure in reference to start position.
Figure 8: Change in insertion phase with flexure in reference to start position.
Figure 9: Change in VSWR with flexure in reference to start position.

Conclusion

Max change in insertion loss at the most extreme case bend radius of 2.40-inches is 0.05 dB, which is found at the frequency range of 18-26 GHz. Max change in insertion phase is 2.9 degrees with a 3.25-inches bend radius flexure, which is seen at the higher frequencies. Max change in VSWR at the most extreme case bend radius of 2.40-inches is 0.11 and is also found at higher frequencies. In conclusion, change in performance change versus flexure is minimal and suitable for lab use.

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