When　the　radiated　CM　current　flows　on　the　isolated　power　converters　with　long　input-output　cables,　radiation　will　be　formed　in　space.　The　coupling　between　the　input　and　output　cables　creates　the　antenna　effect.　Based　on　the　existing　radiation　noise　model,　accurate　extraction　of　antenna　impedance　is　very　important　to　calculate　the　radiated　CM　current　and　predict　radiation　noise.　This　paper　proposes　a　new　antenna　impedance　extraction　method,　which　comprehensively　considers　the　coupling　between　the　antenna　and　coaxial　cables　when　measuring　antenna　impedance　with　a　two-port　network　analyzer.　The　coupling　is　reduced　to　ground　impedance　by　\pi-Type　model,　thus　improving　the　accuracy.　To　verify　the　correctness　of　the　proposed　method,　Ansys　HFSS　is　used　for　simulation　comparison,　and　the　final　simulation　results　are　in　good　agreement　with　the　measured　results.　©　2022　IEEE.