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The plasma absorption probe (PAP) has been proposed for measuring electron density distribution in processing plasmas by using the characteristic of the surface wave [Jpn.J.Appl.Phys.Part 1 38, 5262 (1999)].It consists of a semirigid coaxial cable which protrudes the inner conductor as an antenna and is enclosed in a dielectric tube inserted in the plasma.A frequency-swept electromagnetic wave signal is feeded to the antenna and the frequency dependence of the power absorption is obtained.Then the electron density can be determined from the power absorption spectrum.The surface wave analysis was limited to the dispersion equations in the models of the air-core region and the coaxial cable region.In this article, the wave analysis of the third region, the antenna region which is between the air-core region and the coaxial cable region, is presented experimentally and theoretically.The results show that the power absorption spectrum has a decisive relation with the geometry of the antenna region and the antenna region can not be neglected in the wave analysis of the PAP.