As radio frequency (RF) systems advance, they operate at higher and higher frequency levels, for numerous reasons: to increase the overall throughput in satellites, for example, or to reach greater particle energies in particle accelerators, or increase power in high power microwave sources. The electromagnetic (EM) field densities in these and other components are steadily increasing, which means that there is a higher risk of RF breakdown inside these devices.
RF breakdown encompasses two main phenomena. Multipactor involves breakdown in a vacuum, where electrons are accelerated by the EM field and impact on the device walls. Secondary electrons are then released, and discharge develops. Ionization breakdown involves breakdown in a gas. Electrons are accelerated by the EM field and impact on the gas molecules; the molecules are then ionized, electrons are released and discharge develops.
When this happens, the consequences can be harmful. They include increase of signal reflection and signal noise; generation of non-linearities in harmonics and intermodulation products; outgassing caused by the particle impact on the device walls; and temperature increase, which can result in the destruction of the device.
Some applications where RF breakdown can occur include satellite operation and launching; particle accelerators; high power microwave sources; deep space networks; and radar systems. Well-established theories exist for RF breakdown, but they are based on simplified, mainly analytical assumptions which do not always represent the complexity of the component. This results in a very conservative breakdown power level determination, as well as an inability to carry out representative analysis.
Impacts include component oversizing; a need to perform tests that could have been avoided; higher risk of test failure; and worse, a higher risk of failure during operation. These all result in a significant time and cost penalty.
Full numerical analysis can avoid these consequences and provide a more realistic breakdown calculation while keeping safe margins. It enables breakdown analysis of complex components while supporting the engineer in the component design process, avoiding unnecessary high power tests and increasing the reliability of high power components.
SIMULIA products CST Studio Suite and Spark3D offer several workflows that facilitate this type of analysis. These workflows include a frequency domain solver; an Eigenmode solver; ionization breakdown true/false analysis; DC E/B magnetic field; multicarrier analysis; and modulated signals.
The determination of the breakdown power level is key in certain high power applications. CST Studio Suite Frequency Domain Solver combined with Spark3D or Particle-in-Cell (PIC) can perform the calculations necessary to determine this power level, revealing the maximum amount of power a device can handle.
More information about Spark3D and CST Studio Suite and their ability to predict and prevent RF breakdown is available in the eSeminar “RF Breakdown Analysis with CST Studio Suite and Spark3D.” It can be accessed here.
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