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Phase matching

Phase matching of RF cable assemblies, a critical aspect of many RF Microwave systems, is often misunderstood but essential for optimal system performance. At Winchester, we specialize in phase matching, ensuring that your phased matched RF cable assemblies meet the exacting standards of performance and reliability.

Phase matching explained

Consider a four piece band; the band could be an 80s rock cover band, a new age swing band or a set of classical musicians. Regardless of their genre and instrument type, one way their music would sound exceptional is to finish playing at exactly the same time. The more well synchronized the group, the better they sound. You can imagine a band leader or an orchestra conductor waving their fist overhead sharply, all in an attempt to get the music to stop simultaneously.

Just as musicians coordinate to end on the same beat, phase matching requires RF energy transmitted through cables must arrive at the same point of the signal wave to work at peak efficiency. Phase matching ensures this synchronization, which can be measured in degrees or nanoseconds, much like musicians striving for perfect timing.

Back to our quartet, imagine the difficulty the group would have playing harmoniously if one member had a brand new instrument in perfect working order while the other three had poorly cared for instruments that were mismatched, improperly sized and out of tune.

Crafting phase matched assemblies demands attention to detail akin to tuning instruments in an orchestra. Each component must harmonize seamlessly, from cable design and manufacturing to connector assembly, ensuring cohesive and consistent performance. Each component must function in concert with a precisely executed process and exceptional operator skill  to achieve properly phase matched cables.

Categories of phase matching

Phase matched cables are often defined in terms of “+/- x degrees” to either a standard or within a set.  

Back to our musicians, most typically they are working to match each other; to finish their song at the exact same moment. Any changes they experience together, such as playing conditions, will affect their performance similarly.  

In this sense, phase matched rf cable assemblies might be defined as “+/- x degrees within the set of 4” and their performance is only measured relative to each other.  While best practice dictates the general performance guidelines, that the set is matched within itself is most critical.

Musicians might practice against a digital master, working tirelessly to play precisely in time with the recording. The second technique of defining a phase matched cable assembly could be “+/- x degrees against a standard.”  Theoretically the standard does not change and therefore performance of cables across various lots, repairs and replacement cables could be integrated without impacting system performance.

There are advantages to both techniques, which we will explore later. Selecting which phase matching category is dependent on the application, mechanical and environmental requirements.

Applications for phase matching

Much like music transcends genres, phase matched cable assemblies find their place across diverse industries. 

5 common applications which require the use of phased matched cable assemblies:

  • Radar systems:  Whether in space, in the air or on the ground, modern radar systems used timed elements to accurately track very high numbers of targets.  Phased matched cables ensure advanced radar systems can precisely track and image their targets.  
  • Test and measurement systems:  High frequency test systems need to measure and monitor test subjects across a variety of channels for accurate measurement of performance.
  • Medical devices:  MRI machines and CT scanners all use high frequency elements, phased matched coaxial cable assemblies help ensure high resolution images.
  • Telecommunications:  Telecommunication satellites and cellular towers use phase matched coaxial cable assemblies to ensure synchronized communication between the base station and system reliability
  • Aerospace and Defense:  Phase matched cable assemblies are used in applications such as electronic warfare.  These systems require precise timing and  signal integrity to achieve optimal performance.

Getting matched

Again there are two techniques often used to achieve phase matching. The most typical is applying a tight tolerance to the cable length. RF energy will travel through the coaxial cable at a predictable rate, the more well made the cable, whether flexible or semi-rigid, and the more consistent it’s construction the more likely a physical tolerance on the cable will adequately achieve the performance requirements.  

There are instances where setting the physical length is not sufficient for achieving performance objectives. These cases, such as when the semi rigid cable is bent extensively or when the tolerance is very challenging to meet, a technique known as “trimming to length” is used.  RF cable assemblies are partially completed, phase is measured and then cable is meticulously and repeatedly trimmed until performance falls into the desired range. Just as musicians fine-tune their instruments during a concert, trimming ensures precision performance, even in challenging conditions. Though significantly more time intensive than holding a tight mechanical tolerance, “trimming to the proper phase length” can often achieve tighter phase matching tolerances than the alternative.   

In a future post we’ll dig into phase stability and why it affects RF performance.

If you’re seeking harmony in your connections or have questions about phase matching, Winchester Interconnect is here to help conduct the symphony of your applications.

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