Decompressor

摘要

A non-linear digital filtering process is provided whereby slew rate limitation-like phenomena in analog circuitry are compensated. Particularly, a reduction of the signal amplitude with respect to the theoretical size of the signal if linearity had held is avoided. A correct phase is re-established. Customized linear filtering, up-sampling, and down-sampling before and after the non-linear digital processing minimizes the creation of harmonics. The inventive system and method for non-linear processing has few parameters and it is not limited to a polynomial series. A dedicated calibration method is also provided to adapt the value of the parameter for a precise compensation of the right amount of slew rate limitation or other similar compression. Furthermore, a calibration method is shown to adjust existing DSP filtering to accomplish a precise desired filtering even when non-linear corrections may be arbitrarily large.

主权项

1. A system for compression compensation in a test and measurement apparatus, comprising:
an acquisition element of the test and measurement apparatus for acquiring a waveform having an original sample rate; an optical pre-shaping filter directing a decompression frequency of the acquired waveform to a specific frequency band to generate a shaped signal; an interpolator and a low-pass filter for upsampling the shaped signal to a predefined higher sample rate; a raw decompressor providing a raw decompressor output of the upsampled shaped signal, the raw decompressor performing the steps of:
calculating a derivative of the acquired waveform by applying a digital filter;combining the derivative with a time scale parameter to obtain a scaled change function;applying a transcendental function to the scaled change function to produce a corrected scaled change function;combining the corrected scaled change function and the input waveform samples to correct the samples;and providing a corrected waveform in accordance with the corrected samples; a down sampler for down sampling the raw decompressed output back to the original sample rate; a linear raw decompressor compensator for compensating for the effect of the raw decompressor in a linear limit of small signals by applying an infinite response filter; and a post shaping filter for performing an inverse filtering of the optical pre-shaping filter.