A compact method for measuring antenna impedance using near-field backscatter data

In this paper, a compact measurement method is proposed for deriving the input impedance from the near‐field scattering characteristics of an antenna under test. The relationship between the backscatter data including the near field and the input impedance of the antenna is derived. It is shown that scattered waves can be in the near field if electrical coupling of transmitting and receiving antennas with the antenna to be measured is small. When orthogonally placed transmitting and receiving dipoles are used as a model for the measurement system, practically valid results can be obtained if these antennas are more than a half‐wavelength apart from the antenna under test. Experiments are carried out to validate the method by impedance measurement of balanced and unbalanced dipoles. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(9): 1–8, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20220