nnec- Array geometries are designed SO that necessary angular tion have been also considered [LPEO02]. Frequency information can be obtained. To satisfy the sampling division multiplexing of the reference signal and the theorem, the element spacing should normally be sounding signal is an alternative technique [MATB02]. designed as less than half wavelength. Otherwise, there To obtain the single-directional information, an array may appear grating lobes causing estimation errors of antenna is deployed at the receiver side. Time domain directions of arrival/departure. multiplexing using a high speed RF switch and a single RF Azimuth-only measurements can deploy either a uni- front end is the most popular architecture. Alternatively, form linear array [MATB02], [VLSK03], [SLRT03], parallel receivers can be deployed [SFIH02]. This is [RaSa04], [Herd04], or a Uniform Circular Array (UCA) advantageous for the measurement of large Doppler [SFIH02], [Rich05], [RaSa04]. With the same number shifts due to the shorter measurement time. A multiport of elements, the former has higher resolution in the network analyser can also be considered as a parallel re- broadside and is suitable as the BS antenna, while the ceiver [MGPCBRJL04]. Yet alternatively, a synthetic resolution of the latter is insensitive to the direction and array approach can be used [MATB02], [VLSK03], is suitable as the mobile station antenna. The linear array [HaTa03b]. Here the measurement must be performed has another disadvantage that it suffers from cone am- in a static environment due to the time consuming biguity and the elevated direction of arrival results in an physical motion of the antenna elements. However, the error of the azimuth angle estimate. To reduce the an- SISO sounder hardware can be used without modifica- gular dependency of the resolution, use of a cross array tion, and no array antenna calibration is necessary. antenna is also considered [VeLC03a]. For the double-directional measurements, array an- For joint azimuth and elevation m