Kazufumi Hirata

Preprocessing by eigenbeams and Doppler filters to improve performance of detection of signal number

In this paper, a preprocessing by spatial eigenbeamforming and coherent Doppler filtering for improving detection performance of signal number for highly-correlated signals in low SNR condition is proposed for radar system with digital beamformer. The proposed method utilizes that all of highly-correlated target signals exist in one specific Doppler bin with different Doppler frequency. In this method, eigenbeams from target covariance matrix are formed followed by coherent Doppler filtering with DFT for SNR improvement prior to signal number detection such as MDL. Evaluation of proposed preprocessing with MDL by computer simulation showed higher performance compared with conventional MDL. Quantitatively required SNR is reduced by approximately 7 dB compared with conventional MDL when 50% of probability of correct signal number detection is specified for two closely-spaced targets scenario.

A multiple sidelobe canceller using tapped delay line with Gram-Schmidt processing

A multiple sidelobe canceller (MSLC) that can suppress multiple interferences received by a radar needs more auxiliary antennas than the number of interferences. The use of several auxiliary antennas increases the cost of an MSLC. An MSLC using tapped delay line (TDL type MSLC) that has only one auxiliary antenna reduces cost and has an advantage that the convergence time does not depend on incident directions of interferences. In this paper, we show the relation between the convergence time and the product of frequency difference of interferences and time delay, and propose a TDL type MSLC with Gram-Schmidt processing. Simulation results show that the effect of frequency difference and time delay on convergence time is reduced.