| A convenient model of the compact complete polarization diversity antenna that consists of two collocated orthogonal doubly loaded thin wire loops is discussed. The antenna is capable of simultaneously sensing vectors of electric and magnetic fields. The responses of the electric and magnetic field for each loop are calculated by using classical theory of thin wire loops.; The coupling between two identical loops with arbitrary center locations and orientations is analyzed. Three special cases are discussed. (A) In coupling between two orthogonal loops, it is found that strong coupling can exist for first and higher loop current harmonics. For this reason, electrical size of the antennas plays an important role in the discussion of coupling. It is also found that coupling for orthogonal collocated antennas depends on the relative locations of the antenna terminals on the loops. (B) In the case of coupling between two loops that are slightly titled from their orthogonal orientation, the coupling current is the result of case A plus an additional term, which is proportional to the title angle. (C) In coupling between two orthogonal loops with centers slightly apart, the total coupling current is the result of case A plus the linear combination of three mutual coupling currents that are proportional to the related shifting distance.; The received power, the electric and magnetic antenna factors are analyzed as functions of the antenna load and size. The loads that maximize the received power are shown to be, in general, different from those that are needed to equalize electric and magnetic responses. The consequences of this for the estimation of the direction of arrival are discussed. A statistical model is created to estimate the MSAE of the direction of arrival (DOA). Cramér-Rao bound on the direction of arrival estimation error is derived in terms of the antenna parameters. |
