Directional antenna array for channel measurement syste

Future wireless systems will require significantly higher data rates and reduced costs per transmitted bit than offered at present systems. In wireless systems, multipath fading, signal delays and interference results from many mechanisms, such as reflection and diffraction. In future communication systems it will become an important to be able to resolve multipath signals (in delay, angle and Doppler). One possible solution to the meet these requirements and combat multipath interference is to use smart antenna technologies. Smart antenna solutions have been presented in different areas of core technology, such as active antennas, fixed beamforming and adaptive beamforming, to improve spectral efficiency and to deliver higher network coverage, quality of service and capacity. In this thesis systems for spatial channel measurements are developed in order to study the radio propagation characteristics of wideband mobile channels. Directional channel characterisation is required for building channel models for new systems capable of exploiting the spatial characteristics of channels. The study also provides insights into the dominant propagation mechanisms in complex radio environments such as urban and indoor locations. The measurement systems employ multiple reception channels which were used to support real-time Single-Input Multiple-Output (SIMO) measurements at practical mobile speeds in the UMTS FDD bands. Three vertically polarized antenna arrays were designed and constructed for the 2 GHz band, having suitable properties for characterising the spatial radio charmel in the azimuth plane at one or both ends of a mobile communications link. These were the quasi-Yagi antennas, strip-dipole antennas and U-slot microstrip patch antennas. Their design, implementation and an analysis for their performance are described, including the measurement system used for recording the complex beam patterns of four antenna arrays. A distance transducer that provides 2 cm accuracy is also designed and constructed. A super-resolution algorithm based on a SAGE-type method was used to extract the directions of arrival of multipath components impinging on the antenna array. Small scale measurements in Manchester city centre and around Durham University were taken for a measurement bandwidth of 60 MHz. Direction of arrival measurements for two scenarios are considered using SAGE and beamforming techniques. The functionality and effectiveness of the developed measurement system is demonstrated by performing channel measurements and analysing the experimental data. The time domain information of the channel at the receiver side is analysed, as well as the spatial channel information. It is shown from sample results that spatial domain channel measurements can be used to gain greater knowledge about the dominant propagation mechanisms. The results presented in this study will be very useful in the design of smart wireless communication systems that optimise performance, complexity and cost for given situations.