A joint antenna and post-DFT combining diversity scheme in OFDM receiver

This paper proposes a joint antenna and post-DFT combining diversity scheme for the reception of OFDM signals. The conventional OFDM diversity receiver employs post-DFT combining scheme, which combines signals from a several diversity branches after DFT decomposition. However, post-DFT combining diversity requires the same number of LNAs, IF amplifiers, AD converters, and FFT processors as of diversity branches. In order to solve this problem, the authors has proposed an antenna combining diversity scheme based on electromagnetic coupled array antenna. The proposed diversity scheme requires only one set of LNA, IFA, ADC and FFT processor and gives comparable performance with the maximal ratio combining diversity in case of two-branch diversity. However, the proposed diversity has limitation in the number of diversity branches. The performance of the proposed diversity is much worse than that of the post-DFT one when the diversity branches are more than two. In order to solve this problem, joint use of antenna combining and post-DFT combining is proposed. The proposed scheme is composed of two two-branch antenna combining diversity followed by the post-DFT combining diversity OFDM receiver. The proposed diversity receiver gives the same bit error rate performance as the conventional post-DFT combining four-branch diversity scheme while it only requires two sets of OFDM receiver components.