Low-complexity two-rate based multivariate impulse response reconstructor for time-skew error correction in m-channel time-interleaved ADCs

Abstract

Abstract-Nonuniform sampling occurs in time-interleaved analog-todigital converters (TI-ADC) due to timing mismatches between the individual channel analog-to-digital converters (ADCs). Such nonuniformly sampled output will degrade the achievable resolution in a TI-ADC. To restore the degraded performance, digital time-varying reconstructors can be used at the output of the TI-ADC, which in principle, converts the nonuniformly sampled output sequence to a uniformly sampled output. As the bandwidth of these reconstructors increases, their complexity also increases rapidly. Also, since the timing errors change occasionally, it is important to have a reconstructor architecture that requires fewer coefficient updates when the value of the timing error changes. Multivariate polynomial impulse response reconstructor is an attractive option for an -channel reconstructor. If the channel timing error varies within a certain limit, these reconstructors do not need any online redesign of their impulse response coefficients. This paper proposes a technique that can be applied to multivariate polynomial impulse response reconstructors in order to further reduce the number of fixed-coefficient multipliers, and thereby reduce the implementation complexity.

Efficient signal reconstruction scheme for M-channel time-interleaved ADCs

“…This specification is the same as that considered in [13], [16], and [17]. Thus, we can compare the complexity of the four reconstructors since all the reconstructors are designed to meet the same specification.…”

“…In addition to an increase in the number of variablecoefficient multipliers, the online redesign block for each channel of the regular reconstructor will require inverting a 15 × 15 matrix whereas the online redesign for each channel of the proposed TRB reconstructor can be implemented with a 7×7 matrix inversion. For the above specification, the TRB-MIR reconstructor [17] requires 40 fixed-coefficient and 5 variable-coefficient multipliers. While the reconstructor in [17] needs no online redesign, it is noted that compared to the proposed method, the design method in [17] is applicable only for relatively smaller time-skew errors.…”

“…For the above specification, the TRB-MIR reconstructor [17] requires 40 fixed-coefficient and 5 variable-coefficient multipliers. While the reconstructor in [17] needs no online redesign, it is noted that compared to the proposed method, the design method in [17] is applicable only for relatively smaller time-skew errors. The DMC reconstructor [16] that meets the specification in this example would require 33 fixed-coefficient multipliers, 3 variable-coefficient multipliers and no online redesign.…”

“…1(b). Several techniques have been proposed to reconstruct such bandlimited nonuniformly sampled signals [5,[10][11][12][13][14][15][16][17][18]. The complexity of such reconstructors are usually measured in terms of the number and the type of multipliers used to implement the reconstructor.…”

“…Compared to the DMC reconstructor, the TRB reconstructors require fewer multiplications per corrected output sample and fewer delay elements. While the TRB reconstructor design methods in [14,19] are applicable only for the two-periodic case, the TRB multivariate impulse response (TRB-MIR) reconstructor in [17] can be used for the reconstruction of any M-periodic nonuniformly sampled sequence. Even though the TRB-MIR reconstructor do not require online redesign and needs fewer delay elements compared to the DMC reconstructor, the structure is attractive only for relatively smaller values of timeskew errors.…”