Analysis of lossy microstrips using two-dimensional equations for planar circuits

The analysis of attenuation and dispersion along transmission lines is important particularly at high frequencies. In the case of microstrip lines the wave attenuation is caused by the conductor loss, the substrate loss, and the radiation loss. The conductor loss is due to the finite conductivity of the strip material and is related to the skin depth of the conductor. Also, the current density near the edges of the microstrip is much higher and this contributes to the wave attenuation. We present a model for lossy microstrip lines based on the quasistationary field theory of the microwave planar structures. The model presented allows the evaluation of both the attenuation and the dispersion of lossy microstrips. A good agreement with experimental data is obtained even at higher frequencies.