Microstrip dispersion

Microstrip transmission lines used in microwave integrated circuits are dispersive. The dispersion of the lines is fully characterized by the frequency-dependent normalized phase velocity VP which is equal to the ratio of guide wavelength λ
g
to free-space wavelength λ
0
. An approximate equation is given for the normalized phase velocity VP and for the frequency-dependent line impedance Z for standard microstrip transmission lines. Comparison with available experimental data and computed data shows that the error of the approximation is less than 3 percent for microstrip transmission lines commonly used in engineering applications.