The characteristic impedance calculation method of microstrip line and application in embroidered microstrip line

Presently, it is difficult to measure the characteristic impedance of embroidered microstrip line for its conductive anisotropy directly. The published work had proposed to use S-parameters to estimate the port impedance of a balanced dipole antenna, and it cannot be used to calculate the characteristic impedance of microstrip lines with one arm. Thus, it is still a problem on measuring and obtaining 50 Ω characteristic impedance of embroidered microstrip line. Therefore, taking the reflection coefficient as an intermediate variable, this work proposes to use return loss [Formula: see text] to derive the expression of the characteristic impedance of microstrip line. Combined theoretical calculation with experimental testing on characteristic impedance of the fabric-based microstrip line, the expression of the characteristic impedance was verified. Then, the expression of the characteristic impedance of microstrip line was used to calculate the characteristic impedance of embroidered microstrip line and determine its equivalent substrates. The results show that the fabric embroidered with a single-layer conductive strip is a part of its equivalent substrate, and the fabric embroidered with a double-layer conductive strip is not a part of its equivalent substrate.