A real-time adaptive line enhancer hardware implementation designed for a plasma estimation application†

Abstract

A real-time adaptive line enhancer hardware system has been implemented for noise cancellation in a nuclear fusion instrumentation project. The noise cancellation circuitry, realized with a standard digital signal processor (DSP) chip, uses a direct form adaptive filter and adapts using the least-mean-squares (LMS) algorithm. The noise cancellation circuitry adapts the noise filter weights to the line noise prior to an experiment. Upon initiation of the experiment, the adaption is stopped for the duration of the experiment. Experimental data with noise cancelling may be recorded during the experiment. After the experiment, noise filter weights may be read out to be included with the experimental record for possible later evaluation. The use of these hardware systems could significantly reduce the presently enormous requirements for off-line signal processing to extract plasma information. In this paper, real-time capabilities of the line enhancer circuitry for noise cancellation are demonstrated for simple examples and for the nonstationary fusion experiment data. Performance trade-offs in terms of sampling rate and filter complexity are given.