Modeling lossy substrates with direct boundary element method

It is important to model coupling effects of lossy substrates for the designs of RF or mixed-signal circuits. A direct boundary element method using the complex permittivity concept is presented for accurate modeling the lossy couplings. Only the free-space Green's function is used in this method, and then the method is versatile for substrates with arbitrary doping profiles. Numerical experiments illustrate that our method gives accurate results, and it can easily model a more complex than stratified substrate.