THE RIGHT CABLE & CONNECTOR

Microwave cable assemblies are often the last component to be designed in a system, often treated as ideal or near-ideal components, assuming not much difference among cables. The common thinking is cables simply link one critical system to another. However, a microwave cable assembly is a critical system itself, capable of causing unintended results that may degrade the performance of the system. It is rarely considered how poor design or construction can degrade a cable assembly’s performance with improper handling, damage inflicted during installation or time.

System designers and program managers should consider the following when selecting microwave cable assemblies for their systems:

  • What environmental conditions will the cable assembly be exposed to (i.e., temperature, pressure, humidity)?
  • Will the cable assembly be exposed to vibration or excessive flexing, either by hand or mechanized?
  • What phase and loss stability over temperature is needed?
  • What shielding effectiveness is required and at what frequency?
  • What is the expected average power that the connector-cable combination will carry under the prevailing use conditions?
  • What is the loss budget for the cable run? What is the VSWR budget?
  • Will the cable assembly be subjected to rough handling, either during its service life or installation? If so, consider a ruggedized design.
  • Will the cable assembly be housed in the unpressurized portion of an aircraft? If so, consider a sealed assembly to ensure stable phase and loss performance with altitude (i.e., pressure).
  • Will the cable assembly be exposed to extreme temperature and moisture? If so, consider a sealed assembly.
  • Will the cable assembly be exposed to oil, fuel and chemicals? If so, consider a sealed, ruggedized assembly resistant to chemicals.
  • Non-ruggedized or general-purpose cable assemblies will cost less, yet they are vulnerable to damage. Carefully evaluate the risks versus the cost savings when selecting a general-purpose assembly rather than ruggedized.

Consider the connectors selected for the cable assembly, as this drives a myriad of performance aspects inherent to the assembly. As the connector type influences a cable assembly’s shielding effectiveness, overall RF performance and mechanical durability, system designers should consider the following when selecting a connector type during the initial design process, then performing thorough testing to ensure the entire interconnect will perform reliably in the intended application.

  • Size of the internal components.
  • Number of connectors in the entire link.
  • Distance between connectors.
  • Ease and consistency of termination.
  • Noise margin availability.
  • Electrical performance of the connector with the selected cable assembly.

Choosing the right microwave cable assembly and connector type that will perform consistently after installation, during use and over time, is well worth the effort and any additional expense, which will pay dividends in system reliability and performance.