A reed relay designed to carry high frequencies will generally use a coaxial design approach. With this in mind the formula to calculate the characteristic impedance is the following: Z = 60/(√(e)) ln((D)/A) where Z is the characteristic impedance, √(e) is the square root of the dielectric constant, ln – is the natural logarithm, D is the diameter of the shield, and A is the cross sectional of the reed blade.
