OFDM Diversity Receiver based on Reactance-domain Signal Processing

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Although OFDM(Orthogonal Frequency Division Multiplex) is an efficient technique capable of reducing the performance degradation due to delay spreading in multipath environment and employed as a transmission technique for terrestrial digital television broadcasting and wireless LAN(local area network), it is not capable of improving the degradation due to fading. In order to overcome the fading problem, we have to use space diversity. However, it requires huge amount of computational cost. Especially, in case of post DFT(discrete Fourier transformation) combining diversity, it requires the same number of RF(radio frequency) front-end blocks and DFT processors as of diversity branches.In order to achieve the space diversity receiver without huge hardware, this research project has proposed the reactance-domain signal processing, where the parasitic antenna close to the main antenna element is terminated with the variable reactance. By controlling the variable reactance, we can get the diversity effect with only one RF front-end followed by one OFDM receiver.In this project, we have confirmed that the proposed diversity based on reactance-domain signal processing is performed as a diversity antenna by carrying out the evaluation test. According to the result, we have optimized the shape of antennas where the limitation in size of handheld terminal is taken into account. In order to design the more specific receiver with reactance-domain signal processing, we have developed the simulator for mobile reception of terrestrial digital television broadcasting. We have shown that the proposed reactance domain signal processing receiver is capable of obtaining diversity effect even in case of miniaturized antenna installed onto handheld terminals.