Specific algorithms for elaboration and digital filtering of pulse signals generated in X-ray detectors have been studied and optimized. A signal pulse at the output of a proper analog conditioning circuit is digitized and then the samples undergo a digital filtering procedure.
Jong Kyong Su, a researcher at the General Assay Office, has developed an algorithm for reliable detection of “X-ray informative” pulses partially buried in noise on digital boards which use programmable devices such as DSP or FPGA.
He focused on the application of least mean square (LMS) adaptive filter, which plays an important role in modern digital signal processing (DSP) such as telephone echo cancellation, noise cancellation, equalization of communications channels, biomedical signal enhancement, adaptive control systems, etc. The adaptive filter is a digital filter that can adjust its filter coefficients automatically to adapt input signals via an adaptive algorithm.
He compared two digital processing methods by traditional filters with fixed filter coefficients and a least-mean-squares (LMS) adaptive filter for applications in high resolution X-ray spectroscopy.
The requirements on peak reproducibility and SNR are better met by the LMS filter, thanks to the capability to adapt the parameters to the non-stationary environment of the detectors. The simulation showed that fast settlement of coefficients can be achieved with an algorithm of medium-level complexity, with elaboration time scaling linearly with the filter order.
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