Sphere-TEM mode in rectangular top horn offset coaxial transmission line

We analyze electromagnetic characteristics of the sphere-TEM mode (S-TEM) in a rectangular top horn offset coaxial transmission line (RTHOCT) by spherical wave and independent mode propagation theory. In our analysis, the boundary integral equation technique and multi-local expansion method (MILEM) are applied. The computational practice shows that MILEM can accelerate the convergence of the computational procedure to the EM problems with complex boundaries and multi-singular points. The error of the normalized electric potential along the boundary of RTHOCT is less than 10^-3 in most parts and 10^-2 in the other parts. The numerical results of the electric fields demonstrate a volume with an uniform electric field in RTHOCT. The volume is changeable through careful optimum design. The existence of the volume is a basic factor in using RTHOCT to manufacture a GTEM cell