System and method of equalization of high speed signals
In one aspect, the present invention is directed to a technique of, and system for enhancing the performance of high-speed digital communications through a communications channel, for example a backplane. In this aspect of the present invention, a transmitter includes equalization circuitry to compensate for bandwidth limitations and reflections in high-speed digital communication systems. In one embodiment, the equalization circuitry is designed, programmed and/or configured to introduce intersymbol interference in order to improve the signal integrity in high-speed communications and enhance the operation and performance of such systems. In this regard, the equalization circuitry includes temporally overlapping leading and/or trailing taps (relative to the data (symbol) signal) to reduce, minimize, mitigate or effectively eliminate pre-cursor and/or post-cursor intersymbol interference due to, for example, bandwidth limitations and reflections in high-speed digital communication systems. The amount of equalization may be programmed, adjusted or controlled by varying the positioning of the tap(s), varying the coefficients of the tap(s), and/or varying the pulse durations of the tap(s) (that is, the pulse duration of the equalization signal attributed to the tap).
1. A system for equalizing signals, the system comprising:
a first transmitter comprising equalization circuitry having a leading tap and a trailing tap, wherein the leading tap and the trailing tap use programmable pulse durations to introduce inter-symbol interference into a signal to produce an equalized signal, wherein a pulse duration of the equalized signal attributable to a respective tap is variable.
2. The system of claim 1 , wherein the positions of the taps are adjustable.
3. The system of claim 1 , wherein the taps of the equalization circuitry include programmable coefficients.
4. The system of claim 3 , wherein a respective tap coefficient indicates the amplitude of the equalization signal introduced by the tap.
5. The system of claim 3 , wherein the system further includes a back channel for transmitting information which is representative of the tap coefficients of the taps of the equalization circuitry to the first transmitter.
6. The system of claim 5 , further including a first receiver to receive the equalized signal from the first transmitter, and a second transmitter in communication with a second receiver;
wherein the first receiver calculates information which is representative of the coefficients; and
wherein the second transmitter transmits the information which is representative of the coefficients to the second receiver.
7. The system of claim 1 , wherein the first transmitter uses a pulse amplitude modulation (PAM) communication technique.
8. The system of claim 1 , wherein the taps include programmable coefficients and wherein information which is representative of the programmable coefficients is provided to the system using an external interface.