The estimation of the spectrum usage from the point of view of number of users and modulation types is addressed in this paper. The techniques used here are based on Support Vector Machines (SVM). SVMs are machine learning strategies which use a robust cost function alternative to the widely used Least Squares function and that apply a regularization which provides control of the complexity of the resulting estimators. As a result, estimators are robust against interferences and nongaussian noise and present excellent generalization properties where the number of data available for the estimation is small. The structure pre sented here has a feature extraction part that, instead of using an FFT approach, uses the SVM criterion for spectrum estimation, feature extraction and modulation classification .

It has been previously demonstrated that it is possible to perform remote vibrometry using synthetic aperture radar (SAR) in conjunction with the discrete fractional Fourier transform (DFrFT). Specifically, the DFrFT estimates the chirp parameters (related to the instantaneous acceleration of a vibrating object) of a slow-time signal associated with the SAR image. However, ground clutter surrounding a vibrating object introduces uncertainties in the estimate of the chirp parameter retrieved via the DFrFT method. To overcome this shortcoming, various techniques based on subspace decomposition of the SAR slow-time signal have been developed. Nonetheless, the effectiveness of these techniques is limited to values of signal-to-clutter ratio ≥5 dB. In this paper, a new vibrometry technique based on displaced-phase-center antenna (DPCA) SAR is proposed. The main characteristic of a DPCA-SAR is that the clutter signal can be canceled, ideally, while retaining information on the instantaneous position and velocity of a target. In this paper, a novel method based on the extended Kalman filter (EKF) is introduced for performing vibrometry using the slow-time signal of a DPCA-SAR. The DPCA-SAR signal model for a vibrating target, the mathematical characterization of the EKF technique, and vibration estimation results for various types of vibration dynamics are presented.

No abstract

No abstract