Most VNA measurements require the use of extension cables as part of the test set-up. Measurement accuracy can be severely degraded if these cables are not stable over time and flexure. Thus, the choice of measurement cables is as important as the instrument itself. The MegaPhase® VN series are test port extension cables optimized for vector network analyzer equipment, scalar analyzers and probe stations operating at frequencies up to 65 GHz. In addition to their optimized electrical and mechanical performance they are typically priced at a fraction of OEM test cables.
In most precision test applications, cables are constantly moved with repetitive flexures. Traditional coaxial cables use braid/foil outer conductors. Repetitive flexure causes the braid and foil strands to deform, thereby changing the impedance and compromising the phase stability of the cable. In contrast, MegaPhase GrooveTube® VN technology maintains its geometry over the full life of the cable, which permits consistent measurement accuracy from out-of-the-box through 100,000+ flexures. GrooveTube cables feature a corrugated copper outer conductor, manufactured by helically wrapping the copper tape directly over the PTFE dielectric core instead of the traditional braid/foil outer conductor. This results in better accuracy with fewer recalibrations. This improved electrical and mechanical stability over time combined with its lower initial cost results in the Lowest Cost Per Measurement.™ The VN test cables are housed inside of a crush-, torque- and pull-resistant armor that further enhances the cable’s useful life.
The electrical and mechanical data for the VN series are shown in Table 1. The nominal impedance is 50Ω with a time delay of 1.47 ns/ft. The 0.625" diameter cable has a minimum bend radius of 1.5". The attenuation, connector loss and VSWR for seven different part numbers are shown in Table 2 for frequency ranges from 500 MHz to 65 GHz. The phase and amplitude stability versus flexure for a 360° turn around 4" mandrel is shown in Table 3 for 18 to 65 GHz, while the phase change during movement and recovery from DC to 40 GHz is illustrated in Figure 1. Figure 2 is a similar plot of amplitude change.
Ruggedized port connectors that connect directly to the VNA port are available in 1.85 mm, 2.4 mm, 2.92 mm and 3.5 mm. Other available connector types are N, SMA, TNC and 7 mm, as well as custom designs. All the VN cable assemblies are manufactured to order with a standard two-week lead-time, including odd combinations such as 2.4 mm to Type SC. Because of the modular mechanical design, the VN series cables are repairable. All MegaPhase VN cables are backed by a six-month unconditional warranty.
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