easurements, use of tennas must be introduced at both TX and RX. Time a planar or a solid structure is needed. A UCA can also domain multiplexing can be deployed at the both TX and be used for this purpose [HaTa03b]. Alternatively, RX [KSPH01], [Prop], [RUSK]. The switch timing must a uniform rectangular array may be used [HaTa03b], be synchronised between the TX and RX multiplexers. [Herd04]. To avoid the ambiguity between angles below As the TX multiplexer handles high power, it operates and above the horizontal plane, a solid array structure is slower than the RX multiplexer in general. Therefore, necessary. A spherical array [KSPH01], [KKVV04], the switch timing of the multiplexers is designed SO that a circular cylindrical array [TFBN04], and a rectangular the RX multiplexer scans the array for each TX antenna solid array [TsHT04] have been deployed. element. Some hybrid techniques are also possible so- Array calibration is necessary for the real array antenna, lutions, such as time domain multiplexing at TX and and the array antenna response must be measured in the parallel RXs [RaSa04], and synthetic array at TX and anechoic chamber in advance. A continuous reconstruction time domain multiplexing at RX [Herd04]. A full MIMO technique of the array antenna response from discrete data transceiver is also possible, by using orthogonal signals has been proposed in [LaRT03]. On the contrary, the the- such as code division multiplexing [ZeTS04], [ChSA04] oretical array response can be used for the synthetic array and frequency division multiplexing [SaTA02]. antenna since there is neither mutual coupling between the antenna elements nor variation of properties for individual Antenna architectures elements. When the uniform linear or rectangular array is deployed, ESPRIT algorithm can be applicable. Antenna elements There has been a trial to optimise the array geometry For the non-directional measurements, omnidirectional by using a Genetic Algorithm (GA) [KaKC02]. antennas have been preferred, such as dipole ante