nnas. The antenna element of the synthetic array may also be an omnidirectional antenna due to its original non-di- 4.7.4.3 Parameter estimation rectional use. Slot antennas can be used as horizontally polarised omnidirectional antennas [Rich05]. As explained in the previous sections, the design of Patch antennas are often used as directional antennas adaptive arrays or smart antennas brings several technical deployed in the base station side, or as elements of challenges. It is clear that the knowledge of the DoA conformal arrays to avoid the influence of the support parameters is very important. High resolution techniques structure of the array. Patch antennas are also advanta- can resolve these parameters very accurately, which is geous for polarimetric measurements, as the dual polar- a prerequisite for the design of antennas. In this sub- ised element can be easily realised by using two section, promising methods for determining the full CHAPTER 4.7 Propagation modelling and channel characterisation double-directional and polarimetric parameters of the uniform rectangular array. With the described measure- mobile channel are given. ment set-up, the multipath characteristics of non-specular The high resolution parameter estimation techniques wave scattering from three-dimensional building surface are divided in three different types. Conventional roughness can be determined, showing that multiple paths methods are based on classical beamforming techniques can be detected at many scatterers. Here the delay, directly and require a large number of antenna elements estimated by using ESPRIT, yields close agreement with to achieve high resolution. The second class of the delay of the propagation path determined by using methods are the subspace methods and are high resolu- DoA estimated by ESPRIT and free space velocity. tion sub-optimal techniques, which exploit the eigen- In [SeKa01], two-dimensional fading forecast of time- structure of the input data matrix. The MUSIC variant channels is explained. Because of 