Analysis and Design of Base Station Antennas for Mobile Communications
Sammanfattning: The thesis deals with base station antennas and the environment they work in. Polarization diversity, dual band operation, and adaptive antenna systems are discussed with emphasis on how antennas for these applications should be designed.We compare the polarization diversity performance of different types of dual polarized antenna elements. The scalar product of the far-field of the diversity channels is seen to be the key property of such antennas. Aperture coupled patches are seen to be superior to crossed dipoles because they provide more similar vertical and horizontal polarization patterns. Measurements of radio propagation using a dual band base station antenna are presented. We show that a dual band antenna may provide similar coverage for 900 MHz and 1800 MHz, but with a fixed offset. This indicates that the same cell planning may be used for the two frequency bands. The spatio-temporal properties of a suburban and an urban radio channel are investigated using a dual polarized antenna array and a measurement bandwidth of 150 MHz. We use the measurement data to simulate adaptive up- and down-link beamforming. Antenna element designs for dual polarization and dual band operation are presented. We also present dual polarized array designs for adaptive and multibeam applications. The array for adaptive antenna applications is evaluated by considering the error in direction-of-arrival estimation caused by its non-ideal characteristics. We analyze an infinite planar array of rectangular patches in an arbitrarily composed multilayer media. A two-dimensional moment method is used together with a genetic algorithm to optimize the cross-section of dual polarized base station antennas with respect to the radiation pattern. Finally, we calculate mutual coupling in dual polarized aperture coupled patch elements on cylindrical structures. We compare our results with measurements and find good agreement.
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