Starting directly from the wave equation

the paper analyses the field structures of the TM mode wave propagating within the symmetrical strip line. Expressions for the equivalent capacitance per unit length and the characteristic impedance are derived from the longitudinal electric field component. Measurements for the mentioned parameters have been made at 60 MHz and 850 MHz hands

and the experimental results agree well with the theoretical ones. Comparison of the results here obtained with those obtained by the static TEM mode method has also been made. All expressions given in this paper appear to be more convenient for practical applications.