Equalizer circuit, communication system, and method that is adaptive to varying launch amplitudes for reducing receiver error

Abstract

A transmission line equalizer, communication system, and method are provided for adaptively compensating for changes in transmission path length and transmission path medium. Within the equalizer is a filter that exhibits a high pass characteristic and, more specifically, has an inverse frequency response to that of the transmission path. The inverse filter can include a pair of amplifier stages coupled in parallel, with a mixer chosen to adaptively select portions of one stage over than of the other. The dual stage inverse filter can, therefore, adapt to greater transmission path lengths and/or attenuation. A feedback architecture is used to set the inverse filter response by measuring the amplitude of a communication signal output from the inverse filter during periods of low frequency. A peak detector will capture a peak-to-peak voltage value during those periods, and adjust the output of the slicer to match a launch amplitude of the communication signal. The peak detector within the feedback architecture helps ensure the predicted amplitude matches the launch amplitude to minimize over-compensation or under-compensation even though a different integrator might register no difference in integrated voltage or energy at the output of the inverse filter compared to the output of the slicer.