A method to determine an electrical parameter of form-in-place shielding material with two other parameters known by calculation and simulation

These years, the form-in-place electromagnetic interference (EMI) shielding materials are more widely used in manufacture of radio base stations for its excellent performance in forming and automatic fabricating. These materials contain different particles in silicone elastomer which bring a challenge to construct model for evaluating its shielding effectiveness when simulating. Three electrical parameters, however, should be already known for accurate modeling. This paper provides a method to determine the third parameter with identified two other parameters. Firstly, a fixture with cavity to cavity has been used to measure the scattering parameter, which is also been modeled in the electromagnetic simulation software with or without shielding material. Then, the relationship between three electrical parameters (conductivity, permeability, permittivity) and shielding effectiveness has been modeled. The shielding effectiveness of the materials can be derived by the difference of scattering parameters S21 measured or simulated with and without shielding materials. Subsequently, the third electrical parameter can be calculated by the relationship established. Eventually, three electrical parameters are used to simulate in the software and result demonstrates that simulation and test maintain good consistency.