Distributed microwave breakdown for shielding of sensitive electronics against frontdoor overloads

Summary form only given. Destruction of low noise preamplifiers may happen due to the coupling of High Intensity Radiated Fields (HIRF) through receiving antennas. Breakdown in a low pressure gas valve has been used for years in fast Transmit/Receive waveguide switches protecting a radar receiver not only from the high power microwave pulses from the transmitter, but also from external potentially destructive overloads. Nowadays the front-end of microwave sensors makes use of semiconductor modules connected to an array of radiating elements through printed transmission lines. Solid-state diodes or even ferrite limiters could be suitable technologies to protect the sensitive electronics, if low insertion loss, short rise time and robustness to energetic pulses wouldn't be conflicting requirements, in addition to the cost constraints. Favoring breakdown in front of the receive antenna for protecting the sensitive electronics behind is the solution we investigate in this presentation, combining a frequency selective surface with a low pressure rare gas enclosure. The frequency selective surface is an array of thin metal resonators tuned to the receiver's bandwidth on a dielectric sheet; it reflects back the out-of-band incident waves, whereas in-band waves produce resonance amplified E-field at the tip of the resonators. Above a threshold, this E-field is able to trigger breakdown in the neighboring low pressure gas, with the resulting plasma short-circuiting the frequency selective surface, thus achieving efficient shielding of the antenna elements and electronics behind. A proof-of-concept of such a distributed microwave breakdown shield will be demonstrated through simulations in both steady-state (i.e. before and after breakdown) and in transient conditions. Modeling of transient conditions has been performed through an efficient Finite Differences in Time Domain code combining electromagnetism and particle motion equations. In addition, experimental validation is currently in progress; its results are expected to be available for presentation.