Test environments impose two conflicting requirements on microwave cables that run between the instrumentation and the device under test (DUT). Flexible cables must withstand repeated twisting, bending, and general mishandling while also delivering exceptionally stable amplitude and phase performance even with repeated flexing. To produce cables that can withstand this hostile environment, manufacturers of microwave test cables employ various design techniques and materials that make the cables forgiving over not only hundreds of thousands of flexures (and abuses). The ULTIMATE UTiFLEX family of microwave cables from MICRO-COAX (Pottstown, PA) support measurements from DC to 65 GHz, but without the fragility offer associated with millimeter-wave components.

With more than 15 years experience in manufacturing precision microwave cables, the designers at MICRO-COAX discovered that total flexibility is not necessary an ideal characteristic for a test cable. In order to use cables with excessive flexibility, test engineers have often resorted to supporting the cables in one or more locations between an analyzer and a DUT, resulting in complex test setups and expensive fixturing. To remedy this deficiency, MICRO-COAX gave the ULTIMATE UTiFLEX cables what it calls its Enhanced Test Bench feature, which results in a cable assembly that is flexible but self-supportive (see figure). The cable can be set up once and will remain in position for the next test until repositioned. This reduces the amount of flexing the cables undergo, which in turn improves measurement repeatability and extends calibration intervals. Of equal importance, the Enhanced Test Bench Feature reduces the stress caused by the weight of test cables hanging from a DUT.

ULTIMATE UTiFLEX cables are based on the company's standard flexible microporous test cable. This cable is enclosed in a proprietary flexible armor that provides a high degree of protection from kinking, denting, torquing, pulling, and crimping. The cables have crush resistance of 1000 lb./linear inch, good torsional resistance, and can withstand a static tensile load of 100 lb. The shielding effectiveness is typically better than 100 dB at 1 GHz while insertion loss is less than 1 dB/ft through 40 GHz.

The center conductor, dielectric, and outer conductor (shield) of the cable are isolated within the assembly to ensure that the cable can be dropped, bent, and otherwise abused while maintaining the repeatability of all electrical parameters, the most important being amplitude and phase stability. The connectors used on ULTIMATE UTiFLEX are manufactured by the company specifically for this cable, and are optimized for VSWR performance and connector attachment to the armor. A ruggedized strain relief and anti-roll ring complete the package.

ULTIMATE UTiFLEX test cables, typically supplied in pairs, are available in 18-, 24-, and 36-in. lengths. Their mode-free frequency range is 40 GHz when equipped with 2.92-mm connectors and 65 GHz with 1.85-mm connectors (see table). Each set of cables is tested for phase and amplitude stability, insertion loss, and return loss, and is supplied in a wooden storage case complete with test data and an owner's guide. MICRO-COAX, Inc., 206 Jones Blvd., Pottstown, PA 19464-3465; (610) 495-0110, Internet: www.micro-coax.com.