Lin Jingran

Broadband Robust Adaptive Beamforming in the Presence of Correlated interferences and DOA uncertainties

A novel method of broadband robust adaptive beamforming is proposed in this paper to deal with the signal cancellation caused by correlated interferences and DOA uncertainties. To achieve this goal, the classic techniques of spectral averaging and diagonal loading are integrated into the beamforming, with the former aiming at decorrelation and the latter at robustness against DOA uncertainties. Moreover, the optimal loading is selected based on worst-case performance optimization and a simple closed-form solution to it is suggested after some approximations. Besides its simplicity and low computational cost, this analytical solution reveals how different factors affect the optimal loading. Compared with many relevant methods, the proposed one achieves better robustness against DOA uncertainties, while suppressing both correlated and uncorrelated interferences effectively. Its excellent performance is confirmed via a number of numerical examples.

The Optimal Loading of Robust Adaptive Beamforming Based on Worst-Case Performance Optimization

In this paper the robust adaptive beamforming (RABF) based on worst-case performance optimization is investigated. This method belongs to the class of diagonal loading approaches and determines the loading level by optimizing the worst-case performance. Other than solving the optimal loading by iteration, as many existing methods in this field did, we derive a simple closed-form solution to the optimal loading after some approximations. In addition to reducing the computational complexity, this simple analytical solution reveals how different factors affect the optimal loading. Numerical examples confirm that the closed-form expression is a very accurate approximation to the actual optimal loading

A fast time acquisition method for PSK-2DSS systems

A fast time acquisition method for PSK-2DSS systems is presented in this paper. By analyzing the structure characteristics of the two dimensional spread spectrum sequence, the redundant operations hidden in traditional time correlation method were found. Then, a novel two-stage acquisition method is proposed, aiming mainly at removing the reduplicate multiply operations in the correlation processing. In this two-stage method, the former stage performs some data rearranging operations, on the basis of the estimate values of the initial phases of the two spreading codes. Then in the latter stage, the rearranged data is time correlated with the local version of the first code, and the result is used to verify whether the estimate is right. The data rearranging breaks through the coherent integration length limit in the serial search acquisition. So the proposed method can achieve much higher acquisition sensitivity than the serial search based and is more suitable for weak signals acquisition. Actually, since the data rearranging only adjusts the computation flow and no information will be lost, the proposed method has the same performance as the traditional time correlation. Benefited from the data rearranging, however, many multiply operations in the correlation processing can be combined. Then the computational complexity is reduced dramatically, and the acquisition can be accomplished very efficiently. At the end of this paper, numerical examples confirm the effectiveness of the proposed method.

Broadband Deterministic Blind Beamforming for Speech Separation Using Microphone Arrays via Rotational Invariance Techniques

In this paper a novel approach for speech separation using microphone arrays is presented. It belongs to the class of deterministic blind beamforming (DBBF) approaches via rotational invariance techniques. Since speech should be considered as broadband sources in microphone array related applications, the conventional narrowband DBBF is extended to broadband cases in this paper. Utilizing the nonstationarity of speech, DBBF is implemented at the frequency bins of interest. In order to cope with the problem of channel swap, a rearranging operation is performed, based on the correlation coefficients between the frequency domain separated sequences of adjacent bins. Moreover, the scale ambiguity, another drawback of the general blind source separation approaches, is also eliminated in this paper. Numerical examples confirm the effectiveness of the proposed approach