In accordance with a first aspect of the present disclosure, a channel equalizer is provided for use in a near field communication (NFC) device, the channel equalizer comprising: a filter configured to receive an input signal and to generate a filtered output signal; an estimator configured to determine filter coefficients to be used by said filter; a synchronizer configured to determine when to enable the channel equalizer and to provide one or more corresponding control signals to the estimator. In accordance with a second aspect of the present disclosure, a corresponding method of operating a channel equalizer for use in a near field communication (NFC) device is conceived.

A blind channel equalizer device for a radiofrequency receiver suitable for modulating the constant envelope signal of the transmission includes: an adjustable linear digital filter, defined at a point in time by the coefficients) thereof, able to filter an input signal in order to produce an output signal; an estimator able to estimate a power of the input signal; an adapter able to adapt the filter by calculating the coefficients of the filter at a point in time by subtracting, from the filter coefficients at a preceding point in time, the gradient of a cost function assigned with a correction coefficient. The cost function includes a first distance criterion between the square of the output signal and the power, wherein the correction coefficient is a product including a constant convergence coefficient and a scaling coefficient inversely proportional to the square of the power. Also disclosed is a related Radiofrequency receiver.

In accordance with a first aspect of the present disclosure, a channel equalizer is provided for use in a near field communication (NFC) device, the channel equalizer comprising: a filter configured to receive an input signal and to generate a filtered output signal; an estimator configured to determine filter coefficients to be used by said filter; a synchronizer configured to determine when to enable the channel equalizer and to provide one or more corresponding control signals to the estimator. In accordance with a second aspect of the present disclosure, a corresponding method of operating a channel equalizer for use in a near field communication (NFC) device is conceived.

Apparatus and methods may provide improved equalizer performance, e.g., for optical-fiber-based communication systems. A least-mean-square (LMS) equalizer may include a decision feedback path containing feedback carrier recovery (FBCR), which may have low latency, and which may thus enable high-speed tap updating in the equalizer. Feed-forward carrier recovery (FFCR) may be applied, in parallel with the FBCR, to provide equalizer output by compensating, e.g., for phase noise, with improved carrier recovery/compensation, versus using FBCR to generate the output.

A blind channel equalizer device for a radiofrequency receiver suitable for modulating the constant envelope signal of the transmission includes: an adjustable linear digital filter, defined at a point in time by the coefficients) thereof, able to filter an input signal in order to produce an output signal; an estimator able to estimate a power of the input signal; an adapter able to adapt the filter by calculating the coefficients of the filter at a point in time by subtracting, from the filter coefficients at a preceding point in time, the gradient of a cost function assigned with a correction coefficient. The cost function includes a first distance criterion between the square of the output signal and the power, wherein the correction coefficient is a product including a constant convergence coefficient and a scaling coefficient inversely proportional to the square of the power. Also disclosed is a related Radiofrequency receiver.

Apparatus and methods may provide improved equalizer performance, e.g., for optical-fiber-based communication systems. A least-mean-square (LMS) equalizer may include a decision feedback path containing feedback carrier recovery (FBCR), which may have low latency, and which may thus enable high-speed tap updating in the equalizer. Feed-forward carrier recovery (FFCR) may be applied, in parallel with the FBCR, to provide equalizer output by compensating, e.g., for phase noise, with improved carrier recovery/compensation, versus using FBCR to generate the output.

In part, the disclosure relates to a method of equalizer performance monitoring. The method includes receiving a signal at a receiver; adjusting step size of an adaptive equalizer in response to changes in state of polarization (SOP) of the received signal, wherein adaptive equalizer is in communication with one or more digital signal processing DSP components, wherein the one or more DSP components are in communication with the receiver; and increasing or decreasing step size of adaptive equalizer in response to updates to one or more filter coefficients.