Considerations for millimeter wave interconnection(1)

The overall trend of radio and sensing applications is shifting to higher frequencies, aimed at avoiding interference caused by the increased use of radio frequency and microwave spectrum, or taking advantage of the increasing availability of millimeter wave hardware. Suitable for similar applications such as consumer, industrial, military, aerospace and satellite communications applications. Regardless of the reason for this trend, it will ultimately promote the growth of millimeter wave interconnection (including coaxial cable assemblies, rf connectors and rf adapters) and waveguide interconnection demand. In addition, compared with radio frequency and even microwave hardware, the size of millimeter wave hardware is relatively small, which means that in general, more compact interconnection solutions, such as probes and planar transmission lines (microstrip, strip Line, coplanar waveguide, slot line, etc.).

Unlike low frequencies, there are some phenomena in millimeter waves that are often overlooked or less noticeable. Some of these include skin effects, unexpected transmission modes, and high radio frequency losses from dielectrics/conductors. Transmission lines and interconnects are usually geometrically proportional to their operating frequencies, making these issues more complicated. For example, the maximum cut-off frequency of large coaxial connectors is a function of the spacing and size of the inner and outer conductors. The cut-off frequency does not necessarily mean that the coaxial connectors do not transmit higher frequency signal energy, but only that they no longer operate according to the specification (higher frequency signal components produce other transmission modes).

Other considerations include power capacity and breakdown voltage. Because millimeter-wave interconnects have higher RF losses and generally smaller conductors and geometries, the power capacity and breakdown voltage of these interconnects are generally lower than those designed for low frequencies. This can be a very complicated issue, because high RF losses mean less power can be injected into the system and more power is lost over the length of the interconnect, resulting in a proportional reduction in the effective maximum transmission range.

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1. Considerations for millimeter wave interconnection(2)