Design of Transfer Impedance Measurement Fixture of EMI Gaskets Up To 18 GHz

To achieve the transfer impedance measurement of electromagnetic interference (EMI) gaskets, a fixture useful up to 18 GHz is developed based on the SAE ARP1705C standard. The radial size of the coaxial section of the fixture is shaped from the perspective of its characteristic impedance and suppression of higher-order modes. Subsequently, a parametric analysis is performed to examine the sensitivity of critical dimensions, and the study analyzes the key factors affecting the voltage standing wave ratio (VSWR) of the fixture and its 50 $\Omega$ resistor. Based on the preceding analysis, two solutions are proposed to improve the VSWR: reducing the length of the 50 $\Omega$ resistor and modifying the shape of the coaxial outer conductor. The ultimate outcome of the transfer impedance measurement fixture yields a VSWR lower than 2.6:1, up to 18 GHz. The functionality of the fixture is demonstrated through the measurement of two gaskets, showcasing its practical utility in engineering applications.