CW Power or Average Power Handling is limited by the overheating of the internal material due to power dissipation. The temperature distribution in the coaxial components is not uniform in the radial direction. The highest temperature is in the region closest to the center conductor where the field distribution is highly concentrated. In this area, the dielectric component can reach the point of thermal breakdown leading to failure.
Peak Power is defined by the arc path or radial difference between the center conductor and outer conductor in the critical region.
In a simplified and conclusive manner, we can state that CW Power relates to materials where Peak Power relates to structure.
Multipaction Breakdown defines peak power in spaceflight applications where high vacuum conditions exist, typically greater than 10-5 torr. Multipaction can be calculated by a few different methods. Two of the most common methods use the R. Woo Chart through frequency-distant products and the ESA/ESTEC Multipactor Tool® using internal coax diameter dimensions. Multipaction can be neglected if the frequency is less than 5 MHz or if the signal is less than 5 V (Standard Handbook for Radio Frequency (RF) Breakdown Prevention in Spacecraft Components, page 12).
Ionization Breakdown is an event which occurs during electron resonant collisions between free electrons and gas. This phenomenon is initiated at the gaps within coaxial structures. Ionization as well as multipaction are calculated using the R. Woo Chart through frequency-distant products where one can observe the worst case corona withstanding conditions: P (torr) ≅ f (GHz). This means that the critical pressure point is at a lower altitude if the frequency is higher. Furthermore, if a system is working from ground level to high altitude, > 70,000 ft., then the critical pressure point is unavoidable.
Simple Rules of Thumb
Key Questions to Ask
The intent of the above content is not to become an expert in the subject, but to familiarize you with some conditions and terminology used when dealing with high power applications in ground and space applications.