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

Abstract

In time-interleaved analog-to-digital converters (TIADCs), the timing mismatches between the channels result in a periodically nonuniformly sampled sequence at the output. Such nonuniformly sampled output limits the achievable resolution of the TI-ADC. In order to correct the errors due to timing mismatches, the output of the TI-ADC is passed through a digital time-varying finite-length impulse response (FIR) reconstructor. Such reconstructors convert the nonuniformly sampled output sequence to a uniformly spaced output. Since the reconstructor runs at the output rate of the TI-ADC, it is beneficial to reduce the number of coefficient multipliers in the reconstructor. Also, it is advantageous to have as few coefficient updates as possible when the timing errors change. Reconstructors that reduce the number of multipliers to be updated online do so at a cost of increased number of multiplications per corrected output sample. This paper proposes a technique which can be used to reduce the number of reconstructor coefficients that need to be updated online without increasing the number of multiplications per corrected output sample.Keywords Finite-length impulse response (FIR) filters · least-squares design · two-rate approach · periodically nonuniform sampling · time-interleaved analog-to-digital converters (TI-ADCs) · reconstruction filters.

Time-skew error correction in two-channel time-interleaved ADCs based on a two-rate approach and polynomial impulse responses

“…Even if the regular reconstructor in [5] has fewer multipliers among all the cases, it should be noted that all these multipliers are variable multipliers and need online redesign if the time-skew error varies. The number of fixed and variable multipliers in the proposed method is comparable to that obtained using [7]. However, the reconstructor in [7] requires online redesign when the time-skew error varies.…”

“…5(b), the latter structure helps to reduce the total number of multipliers. Table I shows the total number of multiplier operations at half the input rate if the reconstructor is implemented using the design approach in this paper as well as those mentioned in [5], [6], and [7]. Although the order of the reconstructor designed using the proposed method is somewhat higher than that obtained using [6], the former needs fewer multipliers.…”

“…Reconstructors designed with [6] use very few variable multipliers but need significantly larger number of fixed multipliers. A two-rate based approach was suggested in [7] which resulted in a reconstructor that needed fewer fixed multipliers compared to [6] and fewer variable coefficient multipliers that require online redesign compared to [5]. In this paper, we extend the two-rate approach in [7] to obtain a structure that doesn't require online redesign.…”

“…Section IV outlines the steps to design a two-rate based polynomial impulse response reconstructor. In Section V, with the help of a design example, the complexity of the reconstructor designed using the proposed method is compared with that obtained using [5], [6], and [7]. Section VI concludes the paper.…”

Signal Reconstruction Algorithms for Time-Interleaved ADCs

“…Brief summaries of the papers included in this dissertation are as follows: [88,89]. This paper deals with time-varying finite-length impulse response (FIR) filters used for reconstruction of two-periodic nonuniformly sampled signals.…”