Convergence of a complex adaptive equalizer used in digital communications is substantially improved by updating all coefficients of the equalizer during each filter clock cycle. Complex signal data is passed through a plurality of successive delay stages to provide N sets of delayed complex signal data. The product of each set and a complex error signal is obtained. Each product is concurrently updated with previous product data for the set to provide N sets of updated complex coefficients for selective input to equalizer filters. In an illustrated embodiment, the updated coefficients are truncated and their gain is adjusted prior to input to the filters. The updated coefficients can be multiplexed to provide a clocked stream of coefficient sets for input to the equalizer filters. A VLSI implementation of the equalizer is also disclosed.

Method and apparatus for updating coefficients in a complex adaptive equalizer

Apparatus and method of even harmonic distortion compensation are provided for digital data detection in a disk file. The disk file includes a magneto-resistive (MR) head or other magnetic transducer head and an analog-to-digital converter (ADC) for providing a sampled readback signal. An even harmonic filter is coupled to the ADC for providing a filtered readback signal having only even harmonic components. An adder subtracts the filtered readback signal from the sampled readback signal for providing a compensated output signal. The compensated output signal is applied to a digital channel of the disk file.

Even harmonic distortion compensation for digital data detection

A filter and method of adapting a digital filter provides a single fixed finite impulse response (FIR) filter adaptively from measured data, in a manner whereby the filter's frequency and time resolution can be controlled. The resulting filter exhibits properties which allow it to be efficiently implemented in various multi-rate configurations. Specifically, the system and method produce an FIR filter with high resolution at low frequencies by having a large number of coefficients, but reduces resolution at higher frequencies by allowing only a fraction of the coefficients to adapt to the high frequency part of the signal. This is accomplished by using a multi-rate, segmented adaptation procedure, such that resolution and bandwidth are controlled independently at each state. If desired, the resulting filter can be made to approximate constant Q resolution. In addition, by adapting only a short part of the filter at a time, misadjustment is minimized.

System and method of producing adaptive FIR digital filter with non-linear frequency resolution

An equalizer circuit (11) and a method for adjusting tap weights in the equalizer circuit (11) to provide an equalized signal. The equalizer circuit (11) includes an adaptation circuit (16) coupled to an FIR filter (17) and to an error sign generating circuit (18). The FIR filter (17) provides the signs of a plurality of delay signals to the tap weight adaptation circuit (16). Likewise, the error sign generating circuit (18) provides a sign of the error of an output signal of the FIR filter (17) to the tap weight adaptation circuit (16). The tap weight adaptation circuit (16) uses the signs of the delay signals and the sign of the error signal to generate the tap weights which are passed to the FIR filter (17) for adjusting the tap weights of the FIR filter (17).

Equalizer circuit and a method for equalizing a continuous signal

A communication system includes a transmitter, a communication channel, and a receiver. The transmitter includes a pre-emphasis module, a summing module, a line driver, and a decision feedback pre-emphasis (DFP) module to produce a pre-emphasized serial stream of data based on a communications channel response and an inter-symbol interference level. The receiver includes a linear equalizer, a summing module, a decision module, and a decision feedback equalization (DFE) module. The linear equalizer produces an equalized serial stream of data. The summing module sums at least one data element of the equalized serial stream of data with DFE data elements to produce equalized data elements. The decision module interprets the equalized data elements to produce interpreted data elements to DFE module, which produces the DFE data elements from the interpreted data elements.

Combined decision feedback equalization and linear equalization

A digital automatic line equalizer for compensating distortion of a digital signal transmitted through a transmission line comprises a transversal filter having a set of tap gains for producing an equalized signal as a filter output from the digital signal incoming thereto. A first multiplier squares a current one of the filter output to produce a squared signal and other multipliers multiply the current and the previous ones of the filter outputs to produce product signals. In a calculator, the product signals are weighted and are, thereafter, summed together with the squared signal to produce summed signals which are averaged for a predetermined time duration into a mean value. A controller has a plurality of sets of values for the set of tap gains, compares the mean value with a reference value to produce an error signal and determines one set of the plurality of sets of values in response to the error signal to make the set of tap gains equal to the set of values thereby to maintain the mean value to the reference value so that the transversal filter produces the equalized signal.

Masaru C

Papers

Digital automatic line equalizer with means for controlling tap gains of transversal filter based on mean power of output from the filter