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In a passive radar system, the bearing of the target is difficult to measure for the signal-to-noise ratio of the target's echo signal is generally very low in practise. A novel method to estimate the echo signal's angle is proposed. The cross-ambiguity function of directpath signal and each antenna's receiving signal is calculated to form a virtual array signal, in which the desired echo signal can be enhanced at a certain time delay and Doppler shift, so it is able to estimate its angle. We make the theoretical analysis about how the desired echo signal is enhanced. Some experimental results of an amplitude modulation (AM) radio-based passive radar are presented to verify the effectiveness of the proposed method.

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A nuclear magnetic resonance (NMR) experiment for measurement of time-dependent magnetic fields was introduced. To improve the signal-to-interference-plus-noise ratio (SINR) of NMR data, a new method for interference cancellation and noise reduction (ICNR) based on singular value decomposition (SVD) was proposed. The singular values corresponding to the radio frequency interference (RFI) signal were identified in terms of the correlation between the FID data and the reference data, and then the RFI and noise were suppressed by setting the corresponding singular values to zero. The validity of the algorithm was verified by processing the measured NMR data. The results indicated that, this method has a significantly suppression of RFI and random noise, and can well preserve the FID signal. At present, the major limitation of the proposed SVD-based ICNR technique is that the threshold value for interference cancellation needs to be manually selected. Finally, the inversion waveform of the applied alternating magnetic field was given by fitting the processed experimental data.