T. Rozzi et al., ANALYSIS OF THE SUSPENDED STRIP IN ELLIPTIC CROSS-SECTION BY SEPARATION OF VARIABLES, IEEE transactions on microwave theory and techniques, 45(10), 1997, pp. 1778-1784
The coaxial suspended strip configuration in elliptical cross section
is often found in transitions from ordinary coax to planar circuits an
d other geometries. Using elliptical coordinates makes the problem sep
arable, leading to closed-form solutions for the fundamental TEM mode
and the TE/TM higher modes, ft is emphasized that the presence of the
thin strip is dealt with analytically by this approach. Mode patterns
and TEM characteristic impedance are reported, The cutoff frequencies
versus eccentricity are computed for the first eight modes.