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Phase matched cable
Phase matched cable
Phase matching is a term generally used to describe two or more cable assemblies with the same phase length. A more precise term is electrical length matching since phase measurements are from 0° to 360° of phase, with repeating cycles of 360° phase. The mechanical lengths of phase matched cables may not always be equal due to slight variations in the cable velocity of propagation.
There are two distinctly different versions of phase matching: 1) absolute phase matched cables are matched to a predetermined phase value, and 2) relative phase matched cables are matched to each other. In either case, the tolerance of phase matching is frequency dependent although cable length and type may affect the matching capabilities.
Our supplier Huber + Suhner guarantees phase matching ex-factory. The relevant measurement logs are included in the supply. It is essential during installation and service to ensure that all assemblies of a phase-matched set are exposed to the identical thermal and mechanical stresses.
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Availability
All SUCOFLEX 101P, 118, 126, and other microwave cable assemblies are available as phase-matched sets. Their outstanding thermal and mechanical phase stability makes them the ideal choice for applications requiring high stability. Any required matching values are available on request, although they are limited. The reproducibility of the electrical characteristics of the connectors in addition to thermal and mechanical influences limit the matching range attainable in practice to ± 0.2° per GHz/m, equivalent to a mechanical length of ± 0.13 mm. In long assemblies, the thermal and mechanical influencing factors have a greater impact, resulting in a rise of the lower limit of matchability as the length increases (see graph). In day-to-day practice, we find that it is better to speak of a specification window than of tolerance. As such, a statement such as “within 0.4° per Ghz/m” makes more sense than “± 0.2° per GHz/m”. This applies in particular to assembly sets consisting of more than two individual assemblies.
Reference cable
Usually, a reference cable is produced for each phase-matched assembly set when an initial production run takes place. The absolute electrical length measured is internally saved. The reference cables are stores during 10 to 20 years under controlled conditions (temperature, humidity) together with the order data to allow individual assemblies to be replace whenever the need arises.
