No abstract

We present a methodology for nonlinearity compensation amenable to a wide variety of analog-to-digital converters (ADCs). To that purpose, a postcompensation scheme for a commercial ADC is presented and two compensator models are considered: 1) the memory polynomial (MP) and 2) the modified generalized MP. Since the proposed method does not use any information about the compensated architecture, it can be applied to different ADC designs. Furthermore, we address the measurement and characterization setup of the device under test by making a study of the quality of the signals involved to verify the improvement obtained. The issue of the training sequences required by the proposed compensation method is also addressed in detail. Despite the common use of a single training signal, we propose to use several sinusoids in the bandwidth of interest. With this, it is possible to show that the generalization properties of the estimated postcompensator are greatly enhanced compared with the case of a single sinusoid training sequence.As verified by the measurements, considerable gain in accuracy can be obtained using the proposed methodology. In particular, a 10-dB increment in spurious free dynamic range is obtained using the proposed postcompensators over the complete Nyquist frequency band.

We present a novel method for the estimation and correction of mismatch errors in time-interleaved analog-todigital converters. The estimation of the mismatch errors requires a training signal, but it is efficient, accurate, and effective while keeping low the complexity of the associated algorithm, when compared with other works in the literature. The compensation strategy uses the estimated parameters for offset and gain mismatch error correction, and implements a low-complexity (similar to that of a finite-impulse response filter) Lagrange interpolation filter to correct errors due to timing mismatch, which depends on the dynamics of the input signal. The proposed compensation strategy achieves almost ideal behavior over a wide bandwidth, i.e., only 12% of oversampling is required for an almost complete cancelation of distortion. The method has been tested under severe mismatch conditions (up to 10% timing mismatch and 5% gain and offset mismatch), showing an improvement of over 6 bits in the effective number of bits and 50 dB in the spurious-free dynamic range. In addition, when compared with the available techniques, no limitation on the number of channel converters is introduced since the compensator effectively cancels the distortion even in the presence of large mismatches.

We present SIMULATeQCD, HotQCD's software for performing lattice QCD calculations on GPUs. Started in late 2017 and intended as a full replacement of the previous single GPU lattice QCD code used by the HotQCD collaboration, our software has been developed into an extensive framework for lattice QCD calculations distributed on multiple GPUs over many compute nodes. The code is built on C++, CUDA, and MPI and leverages modern C++ language features to provide high-level data structures, objects, and algorithms that allow users to express lattice QCD calculations in an intuitive way without sacrificing performance. Implemented algorithms range from gradient flow, correlator measurements, and mixed precision conjugate gradient solvers all the way to full HISQ gauge field configuration generation using RHMC. After successful deployment in large-scale computing projects, we want to share the result of our efforts with the lattice QCD community by making it publicly available. In these proceedings, we will present some of the key features of our code, demonstrate its ease of use, and show benchmarks of performance critical kernels on state-of-the-art supercomputers.