Adaptive analog equalizer for partial response channels
First Claim
1. An nth order analog low pass and channel response equalization filter within a sampled digital partial response channel including a clocked analog-to-digital converter, wherein n lies in a range between 5 and 12, the filter comprising:
- a plurality of adaptable transconductance stages connected in a feedback arrangement, means for establishing an optimized filter pole location of each stage, and feedback control loop means for adapting a filter zero location of a said stage on the basis of gradients from said stage.
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Abstract
A single analog filter structure within a partial response channel combines an antialias low pass filter and a time domain waveform shaping equalizer upstream of a digital sampler. The filter also improves latencies associated with timing acquisition of a sampler clock generator loop by removing the latency of a separate equalization filter. The filter also provides a method for adapting a combination of internal filter state voltages and currents in real time for optimizing pole locations of the analog filter structure, during both data and timing recovery operations of the channel.
41 Citations
20 Claims
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1. An nth order analog low pass and channel response equalization filter within a sampled digital partial response channel including a clocked analog-to-digital converter, wherein n lies in a range between 5 and 12, the filter comprising:
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a plurality of adaptable transconductance stages connected in a feedback arrangement, means for establishing an optimized filter pole location of each stage, and feedback control loop means for adapting a filter zero location of a said stage on the basis of gradients from said stage. - View Dependent Claims (2, 3, 4, 5, 6)
integrating amplifier means for integrating an incoming signal;
a slave transconductance cell including;
a differential transistor pair Q3-Q4; and
a slave field effect transistor bridging emitter electrodes of the transistor pair Q3-Q4;
a control element of the slave field effect transistor responsive to a control voltage, the slave transconductance cell providing a stage output;
a digital-to-analog converter U1 for converting a digital stage adaptation value into a differential tuning current;
a master transconductance cell including;
a differential transistor pair Q5-Q6 connected to receive the differential timing current; and
a master field effect transistor bridging emitter electrodes of the transistor pair Q5-Q6, a control element of the master field effect transistor responsive to the control voltage; and
a servo amplifier S1 responsive to the differential tuning current for generating the control voltage.
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7. An adaptive analog filter in a partial response channel including a voltage controlled amplifier and a clocked analog to digital converter, the channel further including a digital data bit detector means for detecting data bits from unfiltered digital samples put out by the clocked analog to digital converter, the adaptive analog filter further comprising:
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a plurality of analog transconductance/capacitance stages, at least some of the stages putting out gradient voltages and receiving analog tap control signals for adjusting stage capacitance, a digital error generator connected to generate discrete error values by comparing functions of detected data bits and unfiltered digital samples, a digital least mean squared error generator for generating tap control values from the discrete error values and from digital representations of the gradient voltages, and digital to analog converter means for converting the tap control values to the analog tap control signals. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
integrating amplifier means for integrating an incoming signal;
a slave transconductance cell including;
a differential transistor pair Q3-Q4; and
a slave field effect transistor bridging emitter electrodes of the transistor pair Q3-Q4;
a control element of the slave field effect transistor responsive to a control voltage, the slave transconductance cell providing a stage output;
a digital-to-analog converter U1 for converting a digital stage adaptation value into a differential tuning current;
a master transconductance cell including;
a differential transistor pair Q5-Q6 connected to receive the differential timing current; and
a master field effect transistor bridging emitter electrodes of the transistor pair Q5-Q6, a control element of the master field effect transistor responsive to the control voltage; and
a servo amplifier S1 responsive to the differential tuning current for generating the control voltage.
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20. The filter of claim 19, wherein the at least one stage further comprises a buffer stage B1 between the integrating amplifier means and the slave transconductance cell.
Specification