Adaptive equalization employing pattern recognition
In described embodiments, an adaptive equalizer employed by a receiver in a communication channel, such as Fibre Channel, employs pattern recognition. When a repeating pattern, such as an IDLE or ARBFF pattern, is employed by a standard to, for example, maintain a communication link, an equalizer of the receiver might adaptively set its equalizer parameters based on characteristics of the signal energy of the repeating pattern rather than adaptively set its equalizer parameters based on characteristics of the signal energy of generally random user data carried on the link. Pattern recognition by the receiver allows for maintaining adaptive equalizer parameters at settings preferred for data detection of the typical random data, improving data detection performance of the receiver when the channel transitions from a preset or synchronization repeating pattern to a user random data pattern.
1. Apparatus for signal equalization, the apparatus comprising:
an equalizer applying equalization to an input signal, the equalization characterized by an eye profile;
a threshold checking module (TCM) adapted to i) monitor the eye profile of the equalized input signal for the presence or absence of a predetermined signal pattern, and ii) detect the presence or absence of the predetermined signal pattern from the eye profile; wherein
the equalizer is further adapted to modify the equalization applied to the input signal based upon the detected presence or absence of the predetermined signal pattern, and the equalizer comprises:
an analog equalizer adapted to apply analog equalization to the input signal based on analog equalizer parameters from an adaptive equalizer to provide an analog equalized signal; and
a decision feedback equalizer (DFE) configured to apply decision feedback equalization to the analog equalized signal, where the decision feedback equalization is based on associated DFE parameters from the adaptive equalizer and on previous decisions for data in the input signal.
2. Apparatus for signal equalization, the apparatus comprising:
an equalizer applying equalization to an input signal, the equalization characterized by an eye profile;
a threshold checking module (TCM) adapted to i) monitor the eye profile of the equalized input signal for the presence or absence of a predetermined signal pattern, and ii) detect the presence or absence of the predetermined signal pattern from the eye profile; wherein
the equalizer is further adapted to modify the equalization applied to the input signal based upon the detected presence or absence of the predetermined signal pattern, and wherein the equalizer comprises an adaptive equalizer configured to modify the equalization based on the detected presence or absence of the predetermined pattern by setting at least one of a vertical threshold and a horizontal threshold of a upper latch associated with an upper eye of the eye profile and setting at least one of a vertical threshold and a horizontal threshold of a lower latch associated with a lower eye of the eye profile.
3. Apparatus for signal equalization, the apparatus comprising:
an equalizer applying equalization to an input signal, the equalization characterized by an eye profile;
a threshold checking module (TCM) adapted to i) monitor the eye profile of the equalized input signal for the presence or absence of a predetermined signal pattern, and ii) detect the presence or absence of the predetermined signal pattern from the eye profile; wherein
the equalizer is further adapted to i) modify the equalization applied to the input signal based upon the detected presence or absence of the predetermined signal pattern, and ii) delay modification of the equalization over several detected instances of the predetermined pattern in the input signal.
4. A method of signal equalization, the method comprising the steps of:
a) applying equalization to an input signal, the equalization characterized by an eye profile, further comprising:
a1) applying analog equalization to the input signal based on analog equalizer parameters from an adaptive equalizer to provide an analog equalized signal;
a2) applying decision feedback equalization (DFE) to the analog equalized signal, where the DFE is based on DFE parameters from the adaptive equalizer and based on previous decisions for data in the input signal;
b) monitoring the eye profile of the equalized input signal for the presence or absence of a predetermined signal pattern;
c) detecting the presence or absence of the predetermined signal pattern from the eye profile; and
d) modifying the equalization applied to the input signal based upon the detected presence of the predetermined signal pattern.
5. A method of signal equalization, the method comprising the steps of:
a) applying equalization to an input signal, the equalization characterized by an eye profile;
b) monitoring the eye profile of the equalized input signal for the presence or absence of a predetermined signal pattern;
c) detecting the presence or absence of the predetermined signal pattern from the eye profile; and
d) modifying the equalization applied to the input signal based upon the detected presence of the predetermined signal pattern by setting at least one of a vertical threshold and a horizontal threshold of a upper latch associated with an upper eye of the eye profile and setting at least one of a vertical threshold and a horizontal threshold of a lower latch associated with a lower eye of the eye profile.
6. A method of signal equalization, the method comprising the steps of:
a) applying equalization to an input signal, the equalization characterized by an eye profile;
b) monitoring the eye profile of the equalized input signal for the presence or absence of a predetermined signal pattern;
c) detecting the presence or absence of the predetermined signal pattern from the eye profile;
d) modifying the equalization applied to the input signal based upon the detected presence of the predetermined signal pattern; and
e) delaying modification of the equalization over several detected instances of the predetermined pattern in the input signal.