Influence of Pulse Power on the Parameters of Film Absorbing Elements

Film absorbing elements are widely used for the construction of waveguide, coaxial, strip and microstrip attenuators and adapter attenuators, as well as for application in hybrid RF and microwave integrated circuits. The current state of their development is characterized by the search for ways to improve their electrical characteristics and a better understanding of the processes occurring in the absorbing elements. The thermal stability of absorbing elements under pulsed action, depending on a number of difficult-to-model structural and technological factors, is of considerable interest. In this work, using the Elcut software package, a simulation of the operating mode of a film absorbing element is carried out, in which all the heat generated by the input pulses is absorbed by the film, taking into account the dependences of its specific surface resistance and specific heat capacity on temperature. The dependences of the heat-generation density, the distribution of the specific surface resistance and the electric-field strength over the surface of the resistive film are investigated for a number of topologies of absorbing elements of large and small attenuations: typical and optimized, with a more uniform distribution of the current density and potential gradients over the film surface. A technique is proposed and dependences of the absorbing element’s input resistance and attenuation on the energy of the input pulse, on the specific heat capacity, and on the temperature coefficient of resistivity, are given taking into account the temperature dependences for typical materials of resistive films. It is demonstrated that changes in the key parameters of absorbing elements can exceed in some cases 40% for attenuation and 80% for the input resistance. The proposed technique can be used to determine the maximum energy of the input pulse signal by the highest instantaneous permissible overheating temperature of a resistive film.