Design consideration of closely spaced polarization-and pattern-diversity antenna pair

Design consideration of a closely spaced antenna pair with polarization and pattern diversity is presented in this paper. Mutual coupling between the antennas causes pattern distortion and increases cross polarization, and thus it degrades the pattern and polarization diversity and increases the envelope correlation. Two configurations of antenna pair are proposed to examine their mutual coupling and envelope correlation. Each configuration is composed of two perpendicular electrical and magnetic dipoles because, theoretically, it should have higher polarization and pattern diversity. Using two noted formulas of envelope correlation for both configurations, it is found that the values calculated by the two formulas for the same configuration may differ significantly when the antenna pair has larger mutual coupling and cross polarization. Although the calculation of envelope correlation via S-parameters is more time-saving, it is necessary to check the other formula via pattern integration when noticeable amount of mutual coupling exists in a closely spaced antenna pair.