Accurate closed form expressions for characteristic impedance of coupled line with sliced coaxial cable

Based on a rigorous analysis of finite element and curve fitting techniques, a set of accurate closed-form formulas are presented for the even and odd mode characteristic impedances of the coupled-lines made of two sliced coaxial cables. Compared with the rigorous solutions of the impedances, the values from the general expressions give an accuracy of >1% for a wide-range of cut depths and are suitable for all coupled lines with cables whose outer-inner conductor diameter ratio is between 1.4 and 10. These formulas can be applied to industrial applications of coupled lines