Impedance Calculation of High Frequency Shielded Cables with the Aid of Conformal Mappings

摘要

This paper presents a new method for the calculation of the impedance of high frequency channels and in particular that of shielded twisted pair cables. Its main advantage is that it uses a more realistic shield geometry instead of the ideal cylindrical case, which most of the related literature is based on. It uses conformal mapping for the conductor-to-conductor capacitance and effective permittivity calculations for extra accuracy. Lastly, characteristic impedance equations are derived. Comparison with measurements is made to show the improvement; practical considerations of the new method are also addressed.