Abstract: A receiver that easily receives signals from transmission channels having long cable lengths is presented. The receiver includes an analog pre-filter that removes distortions and intersymbol interference from a predetermined transmission channel. The analog pre-filter is coupled with a digital receiver that provides digital equalization. The combination of analog equalization with digital equalization allows for simplified digital equalization while retaining the versatility of digital signal processing.

Abstract: A receiver that easily receives signals from transmission channels having long cable lengths is presented. The receiver includes an analog pre-filter that removes distortions and intersymbol interference from a predetermined transmission channel. The analog pre-filter is coupled with a digital receiver that provides digital equalization. The combination of analog equalization with digital equalization allows for simplified digital equalization while retaining the versatility of digital signal processing.

Abstract: An analog equalizer (613 and 614) adaptively equalizes an input analog signal affected with intersymbol interference (“ISI”), or an intermediate analog signal generated therefrom, to produce a filtered partially equalized analog signal with reduced ISI. An analog-to-digital converter (210) converts the filtered analog signal, or an intermediate analog signal generated therefrom, into an initial digital signal. A digital equalizer (212) adaptively equalizes the initial digital signal, or an intermediate digital signal generated therefrom, to produce an equalized digital signal as a stream of equalized digital values with further reduced ISI. An output decoder (605) decodes the equalized digital values, or intermediate digital values generated therefrom, into a stream of symbols.

Abstract: Analog echo-cancelling circuitry (611 and 627) operates on an input analog signal that includes an echo of an output signal, or on an analog signal generated from the input signal, to produce an analog signal with reduced echo. An analog-to-digital converter (210) converts the echo-reduced analog signal, or an analog signal generated therefrom, into a digital signal. Digital echo-cancelling circuitry (615 and 621) operates on the digital signal, or on a digital signal generated therefrom, to produce a digital signal with further reduced echo. An output decoder (605) decodes the echo-reduced digital signal, or a digital signal generated therefrom, into a stream of symbols. The echo-filtering characteristics of both echo-cancelling circuitries are typically adaptively adjusted during generation of the symbol stream. The analog echo-filtering characteristics may be adapted in response to information provided by operating on the echo-reduced digital signal or on a digital signal generated therefrom.

Abstract: A receiver system contains an analog pre-filter (207 or 619), an analog-to-digital converter (210), a digital equalizer (212), and a decoder (605) arranged sequentially for processing an input analog signal (yk). The pre-filter produces a filtered analog signal (Zs) with reduced intersymbol interference. The converter provides analog-to-digital signal conversion. Digital equalization circuitry in the equalizer operates according to a transfer frmnction c - 1 ? z + c 0 + ? M i = 1 ? c i ? z - i to produce an equalized digital signal (a'k) as a stream of equalized digital values. Coefficients c?1 and c0 are fixed. Each other coefficient ci is adaptively chosen. The decoder converts the equalized digital values, or intermediate values generated therefrom, into a stream of symbols.

Abstract: An analog equalizer (613 and 614) adaptively equalizes an input analog signal affected with intersymbol interference (“ISI”), or an intermediate analog signal generated therefrom, to produce a filtered partially equalized analog signal with reduced ISI. An analog-to-digital converter (210) converts the filtered analog signal, or an intermediate analog signal generated therefrom, into an initial digital signal. A digital equalizer (212) adaptively equalizes the initial digital signal, or an intermediate digital signal generated therefrom, to produce an equalized digital signal as a stream of equalized digital values with further reduced ISI. An output decoder (605) decodes the equalized digital values, or intermediate digital values generated therefrom, into a stream of symbols.

Abstract: There is disclosed an echo canceller circuit for use in a full duplex transceiver of the type comprising a line driver capable of sending analog transmit signals through a cable and comprising a line receiver capable of receiving analog receive signals from the cable. An echo canceller impedance model circuit is coupled to an output of the line driver and is coupled to an input of the line receiver. The echo canceller impedance model circuit generates an echo canceller current that is equal in magnitude and opposite in phase to a current that represents signal echoes that are present in the analog receive signals. The echo canceller impedance model circuit has a variable impedance for generating the echo canceller current. The variable impedance has at least one variable resistor and at least one variable capacitor.

Abstract: A receiver system suitable for a local area network contains an analog pre-filter (207 or 619), an analog-to-digital converter (210), a digital equalizer (212), and a decoder (605). A symbol-information-carrying input analog signal (yk), or a first intermediate analog signal generated from the input analog signal, is filtered by filtering circuitry in the pre-filter to produce a filtered analog signal (Zs) with reduced intersymbol interference. The filtering circuitry operates according to a transfer function such as (b1s+1)/(a2s2+a1s+1) or (1?Vc)+VcPF(s) where Vc is adaptively varied. The analog-to-digital converter provides analog-to-digital signal conversion. The equalizer provides digital signal equalization to produce an equalized digital signal (a?k) as a stream of equalized digital values. The decoder converts the equalized digital values, or intermediate digital values generated from the equalized digital values, into a stream of symbols.

Abstract: There is disclosed an echo canceller circuit for use in a full duplex transceiver of the type comprising a line driver capable of sending analog transmit signals through a cable and comprising a line receiver capable of receiving analog receive signals from the cable. An echo canceller impedance model circuit is coupled to an output of the line driver and is coupled to an input of the line receiver. The echo canceller impedance model circuit generates an echo canceller current that is equal in magnitude and opposite in phase to a current that represents signal echoes that are present in the analog receive signals. The echo canceller impedance model circuit has a variable impedance for generating the echo canceller current. The variable impedance has at least one variable resistor and at least one variable capacitor.

Abstract: There is disclosed a transceiver for use in a high speed Ethernet local area network (LAN). The transceiver comprises: 1) front-end analog signal processing circuitry comprising: a) a line driver for transmitting an outgoing analog signal to an external cable; b) a DC offset correction circuit for reducing a DC component in an incoming analog signal; c) an echo canceller; d) an automatic gain control (AGC) circuit; and e) an adaptive analog equalization filter. The transceiver also comprises: 2) an analog-to-digital converter (ADC) for converting the analog filter incoming signal to a first incoming digital signal; and 3) digital signal processing circuitry comprising: a) a digital finite impulse response (FIR) filter; b) a digital echo cancellation circuit to produce a reduced-echo incoming digital signal; c) a digital automatic gain control (AGC) circuit; and d) a digital base line wander circuit.

Abstract: In accordance with the presently claimed invention, compensation for reducing ISI products within an electrical data signal corresponding to a detected data signal received via a signal transmission medium introduces distinct compensation effects for individual ISI products within the electrical data signal. Distinct data signal components within the detected data signal and corresponding to such ISI products can be selectively and individually compensated, thereby producing a compensated data signal in which each selected one of such individual data signal components is substantially removed. Individual data signal components or selected combinations of data signal components can be compensated as desired.

Abstract: A decision feedback equalizer with dynamic feedback control for use in an adaptive signal equalizer. Timing within the decision feedback loop is dynamically controlled to optimize recovery of the data signal by the output signal slicer. The dynamic timing is controlled by a signal formed as a combination of feedback and feedforward signals. The feedback signal is an error signal related to a difference between pre-slicer and post-slicer signals. The feedforward signal is formed by differentiating and delaying the incoming data signal.

Abstract: A compensation circuit for reducing intersymbol interference (ISI) products within an electrical data signal corresponding to a detected data signal received via a signal transmission medium provides for selective application of compensation to individual, discrete data signal components. According to one embodiment, one circuit branch processes the electrical data signal to substantially remove one distinct signal component representing an ISI product of some portion of the data symbol sequence. A second circuit branch approximately duplicates an ISI product of another portion of the data symbol sequence for removal by subtraction within a signal combiner from the compensated signal provided by the first circuit branch. A third circuit branch approximately duplicates an ISI product of still another portion of the data symbol sequence also for removal by subtraction within the signal combiner from the compensated signal provided by the first circuit branch.

Abstract: A crosstalk compensation engine for reducing signal crosstalk effects within a data signal. Demultiplexed data signals corresponding to multiplexed data signals received via a signal transmission medium are processed to significantly reduce one or more signal crosstalk products related to one or more interactions among the multiplexed data signals within the signal transmission medium. Such signal crosstalk products include those resulting from dense wavelength-division mutiplexing of the data signals used to provide the multiplexed data signals, four-wave mixing among the multiplexed data signals within the signal transmission medium, and cross-phase modulation among the multiplexed data signals within the signal transmission medium.

Abstract: There is disclosed a mixed mode equalization system for use in a transceiver capable of operating in a high frequency Ethernet local area network (LAN).

Abstract: A decision feedback equalizer with dynamic feedback control for use in an adaptive signal equalizer. Timing within the decision feedback loop is dynamically controlled to optimize recovery of the data signal by the output signal slicer.

Abstract: There is disclosed an automatic gain control circuit (AGC) controller for use in a transceiver for operating in a high frequency Ethernet local area network (LAN). The transceiver comprises front-end analog signal processing circuitry capable of transmitting an outgoing analog signal to an external cable via a: transformer, reducing a DC component in an incoming analog signal, and reducing an echo of the outgoing analog signal in the incoming analog signal. The front-end analog signal processing circuitry also comprises an automatic gain control (AGC) circuit for amplifying the incoming analog signal by an adjustable gain factor. The AGC controller comprises: 1) a first circuit for determining an absolute value of an output signal of the front-end analog signal processing circuitry; and 2) comparison circuitry for comparing the absolute value of the output signal to a pre-determined threshold value and generating a gain control signal in response to the comparison.

Abstract: A method for equalizing a signal in a transceiver includes receiving an analog signal and adaptively equalizing the analog signal in an adaptive equalization filter to produce an analog filtered signal. The method also includes converting the analog filtered signal to a digital signal, digitally adapting the digital signal in a digital finite impulse response (FIR) filter, and modifying at least one digital filter coefficient of the digital FIR filter according to a signal error associated with an output of the digital FIR filter. The method further includes providing the at least one modified digital filter coefficient of the digital FIR filter to an analog equalization controller. In addition, the method includes using the at least one modified digital filter coefficient of the digital FIR filter in the analog equalization controller to adaptively equalize the analog signal in the adaptive equalization filter.

Abstract: A method corrects an input DC offset signal generated in front-end analog signal processing circuitry in a transceiver capable of operating in a high frequency local area network. An output signal from the front-end analog signal processing circuitry of the transceiver is received in a DC offset correction controller. A DC offset signal component in the output signal from the front-end analog signal processing circuitry due to an accrued DC offset is detected. A DC offset correction signal is sent from the DC offset correction controller to an adjustable biasing circuit coupled to a differential amplifier of a receiver line driver of the transceiver to modify the DC offset signal component.

Abstract: There is disclosed a transceiver for use in a high speed Ethernet local area network (LAN). The transceiver comprises: 1) front-end analog signal processing circuitry comprising: a) a line driver for transmitting an outgoing analog signal to an external cable; b) a DC offset correction circuit for reducing a DC component in an incoming analog signal; c) an echo canceller; d) an automatic gain control (AGC) circuit; and e) an adaptive analog equalization filter. The transceiver also comprises: 2) an analog-to-digital converter (ADC) for converting the analog filter incoming signal to a first incoming digital signal; and 3) digital signal processing circuitry comprising: a) a digital finite impulse response (FIR) filter; b) a digital echo cancellation circuit to produce a reduced-echo incoming digital signal; c) a digital automatic gain control (AGC) circuit; and d) a digital base line wander circuit.