Improvement of DOA estimation accuracy of UWB signal by equi-frequency ratio division

High resolution method for direction of arrival (DOA) estimation using array antenna is studied actively. The estimation accuracy for ultra wideband (UWB) signal is decreased because of distortion of antenna patterns. For the problem, the authors have already proposed a sub-band signal processing technique to decrease the effect of antenna pattern distortion. In this paper, a novel division method of frequency band for sub-band signal processing is proposed. In the proposed method, UWB signal is divided with equi-frequency ratio (EFR). Through computer simulation, it is clarified that the estimation error is greatly reduced by combination of spectrum averaging method and EFR method even if the relative bandwidth is very wide. It is also shown that the estimation accuracy is improved by EFR method when the frequency ratio is large and number of sub-band is small. Therefore, we can say that the proposed EFR method is effective for wideband signals with small sub-band number system.