System and method for digital compensation of timing skew mismatch in time interleaved analog to digital converters

1 . A digital timing skew compensator, comprising:

a first polyphase adaptive filter bank having a first input and a first output;

a first input matrix coupled to the first input of the first polyphase adaptive filter bank;

a first subtractor coupled to the first output of the first polyphase adaptive filter bank, wherein the first subtractor removes a first signal generated by the first polyphase adaptive filter bank from digital outputs of sub analog-to-digital converters (ADCs) of a time-interleaved ADC to create a desired signal, wherein the desired signal is coupled to the first input matrix;

a modulation matrix that modulates the digital outputs of the sub-ADCs to create a modulated signal vector;

a second polyphase adaptive filter bank having a second input and a second output;

a second input matrix coupled to the second input of the second polyphase adaptive filter bank; and

a second subtractor coupled to the second output of the second polyphase adaptive filter bank, wherein the second subtractor removes a second signal generated by the second polyphase adaptive filter bank from the modulated signal vector to create an error signal, wherein the error signal is coupled to the second input matrix.

2 . The digital timing skew compensator of claim 1 , wherein the modulation matrix processes complex signals by complex frequency shift operations.

3 . The digital timing skew compensator of claim 1 , wherein the modulation matrix comprises a Hadamard transform.

4 . The digital timing skew compensator of claim 1 , wherein each of the first polyphase adaptive filter bank and the second polyphase adaptive filter bank comprise a first number of adaptive finite impulse response filters, wherein the first number equals a second number of sub-ADCs in the time-interleaved ADC.

5 . The digital timing skew compensator of claim 4 , wherein each adaptive finite impulse response filter of the first polyphase adaptive filter bank receives all polyphase components that are generated from a third output of the first input matrix and each adaptive finite impulse response filter of the second polyphase adaptive filter bank receives all polyphase components that are generated from a fourth output of the second input matrix.

6 . The digital timing skew compensator of claim 5 , wherein an ordering is different for each of the polyphase components in each adaptive finite impulse response filter.

7 . The digital timing skew compensator of claim 5 , further comprising a first least-mean squared circuit for tuning first coefficients of the first polyphase adaptive filter bank and a second least-mean squared circuit for tuning second coefficients of the second polyphase adaptive filter bank.

8 . The digital timing skew compensator of claim 7 , wherein the first least-mean squared circuit and the second least-mean squared circuit reduce energy signals of each of the polyphase components.

9 . The digital timing skew compensator of claim 8 , wherein the first least-mean squared circuit and the second least-mean squared circuit each comprise a parameter to stabilize the first polyphase adaptive filter bank and the second polyphase adaptive filter bank, respectively.

10 . The digital timing skew compensator of claim 1 , wherein the digital timing skew compensator is implemented in a field-programmable gate array.

11 . The digital timing skew compensator of claim 1 , wherein the digital timing skew compensator is implemented in an application specific integrated circuit.

12 . A digital timing skew compensator, comprising:

an adaptive filter bank having a first input and a first output;

a first subtractor coupled to the first output of the adaptive filter bank, wherein the first subtractor removes a reconstructed error component generated by the adaptive filter bank from a digital output of a time-interleaved analog-to-digital converter (ADC) to create a compensated signal; and

a modulator that modulates the compensated signal to create a modulated signal vector, wherein the modulated signal vector is coupled to the first input of the adaptive filter bank.

13 . The digital timing skew compensator of claim 12 , wherein the modulator processes complex signals by complex frequency shift operations.

14 . The digital timing skew compensator of claim 12 , wherein the modulator comprises a Hadamard transform.

15 . The digital timing skew compensator of claim 12 , wherein the adaptive filter bank comprises a first number of adaptive finite impulse response filters, wherein the first number is one less than a second number of sub-ADCs in the time-interleaved ADC.

16 . The digital timing skew compensator of claim 15 , further comprising a least-mean squared circuit that adjusts weights of each of the adaptive finite impulse response filters to minimize energy signals of each component of the compensated signal.

17 . The digital timing skew compensator of claim 16 , wherein the least-mean squared circuit comprises a parameter to stabilize the adaptive finite impulse response filters.

18 . The digital timing skew compensator of claim 12 , wherein the adaptive filter bank comprises polyphase adaptive filters, wherein each polyphase adaptive filter comprises a bank of impulse response filters.

19 . A digital timing skew compensator, comprising:

an input to receive a digital signal from either a time-interleaved analog-to-digital converter (ADC) or a plurality of sub-ADCs, wherein the time-interleaved ADC comprises the plurality of sub-ADCs;

a first output to provide a compensated digital signal;

a feedback path between the first output and the input having an adaptive filter bank disposed in the feedback path; and

a subtractor that removes a second output of the adaptive filter bank from the input to generate the compensated digital signal.

20 . The digital timing skew compensator of claim 19 , further comprising a modulator disposed in the feedback path that receives the compensated digital signal from the first output and provides a modulated signal to the adaptive filter bank.