High-frequency scattering by a narrow gap on a microstrip line

The high-frequency scattering parameters and equivalent circuit for a gap on a microstrip line are found by analyzing the problem with an accurate semi-analytical method in the spectral domain, using an even/odd mode analysis. The analysis accounts for radiation into space as well as into surface waves, both of which become more pronounced at higher frequencies. The analysis allows for an examination of these two separate powers in order to examine the power loss mechanism at the gap. The results remain accurate even at high frequencies where the characteristic impedance of the microstrip line becomes non-unique. The only assumption is that the length of the gap is fairly small compared to a wavelength.