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The coupled microstrips and coupled stripline devices are characterized by their strip width, strip spacing and substrate properties. The Coupled Microstrips Calculator and Coupled Striplines Calculator find the even and odd mode impedances for the given strip width and strip spacing. They also calculate the even and odd mode effective permittivities, which are typically different. The system characteristic impedance of the coupled line is calculated from the formula: Z :<sub>0s</submath> Z_0 = &radic;( Z_{\sqrt{ Z_{0e} } . Z<sub>Z_{0o} } </submath> ).  To calculate the guide wavelength, the average of the two effective permittivities is used. In addition, the coupling coefficient of the coupled line is calculated in dB from the formula:  :<math> C = ( Z_{\frac{ Z_{0e} } - Z_{Z_{0o} ) / ( Z_{} }{ Z_{0e} } + Z<sub>Z_{0o} } </submath> ).  The Coupled Microstrips Designer and Coupled Striplines Designer, on the other hand, find the values of the strip width and strip spacing for given values of the even and odd mode characteristic impedances.