Dielectric properties 1 Dielectrics property 1 Dust 1 Engines 1 Finite element method 1 Gasoline 1 Gasoline particulate filter 1 Mass determination 1 Microwave cavity perturbations 1 Mixing rules 1 Particulate filters 1 Perturbation techniques 1 Radiofrequencies 1 Radio‐frequency 1 Soot 1 Soot mass determination 1 Substrates 1 dielectric properties 1 finite element method (FEM) 1 gasoline particulate filter (GPF) 1 microwave cavity perturbation 1 mixing rule 1 radio‐frequency (RF) soot mass determination 1