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This paper shows the generation of a local oscillator (LO) signal for cellular transceivers by means of a phase-locked loop and a phase interpolator (PI) digital-to-time converter (DTC). The PI-DTC allows arbitrary frequency shifts over a wide range. We derive a closed-form description of the spurs in the spectrum of the LO signal caused by quantization and nonlinear effects for the PI-DTC. Furthermore, we show the existence of a new class of spurs generated due to noise processes in the PI. Measurement and simulation results are in good agreement with our closed-form solution. [ABSTRACT FROM AUTHOR]

In this paper, a new control structure based on the dual quantization technique is presented for an electromechanical sigma–delta modulator (EM- \Sigma \Delta \textM ) applied to a microelectromechanical system (MEMS) accelerometer. The modulator adopts a 2-0 multistage noise shaping structure (MASH2-0), taking the advantage of the intrinsic linearity of single-bit quantization and the reduced quantization error of multibit quantization in a single modulator. The sensor system is studied by the system-level modeling and the hardware implementation based on the field-programmable gate array technology. The study shows that, MASH2-0 shares the benefits of a MASH2-2 architecture of having an inherent stability, a high overload input level, and a high dynamic range compared with single-loop EM- \Sigma \Delta \textM . However, the MASH2-0 architecture benefits from a considerably simpler implementation, while achieving a higher dynamic range and a higher signal-to-noise ratio compared with a MASH2-2 and a fourth-order single-loop \Sigma \Delta \textM architecture. A capacitive MEMS accelerometer was designed and employed with this control system. Within a bandwidth of 1 kHz, the sensor achieved a noise floor level of −130 dB and a bias instability as low as 20~\mu \textg at an integration time of 40 s. Simulation estimated a full scale of ±20 g acceleration. The investigation confirms the concept of the MASH2-0 structure and shows its potential as a closed-loop interface for high-performance capacitive MEMS accelerometers. [2015-0071] [ABSTRACT FROM PUBLISHER]

Time domain analysis is used to determine whether A/D converters that employ higher order sigma-delta modulators, widely used in digital acoustic systems, have superior performance over classical synchronous A/D converters with modulators of first order when taking into account their important metrological property which is the magnitude of the quantization error. It is shown that the quantization errors of delta-sigma A/D converters with higher order modulators are exactly on the same level as for converters with a first order modulator. [ABSTRACT FROM AUTHOR]

The processing capabilities that are included into the acquisition block of the real-time digital oscilloscopes largely contribute to determine the overall performance of the instrument. Their remarkable improvement has made it possible to enhance the performance in terms of increased measurement rate, automation, and reduced measurement uncertainty related to quantization and noise. This paper presents the implementation of a preprocessing circuit for a novel acquisition mode of bandpass signals, which is characterized by an increased vertical resolution. Although the theoretical foundations were recently presented with simulative results, here, the circuital implementation of such an acquisition mode is presented. The focus is on mid or low cost digital oscilloscopes that can improve their vertical resolution at a negligible additional cost. First, a preliminary field programmable gate array implementation is considered to evaluate the achievable performance both from a theoretical point of view and throughout experimental tests. Then, a custom application specific integrated circuit implementation, in 28-nm complementary metal–oxide–semiconductor technology is analyzed. Along with the parameter optimization, the work experimentally tests the acquisition mode and evaluates the effects of nonideal characteristics such as finite word length and nonideal filtering. The increase in the effective number of bit (ENoB) is up to 2.5 bit, whereas the ENoB degradation because of word length and nonideal filtering is quantified as \sim1.1 and 0.5 bit. The design highlights that there is substantial margin for parallel implementation that is the base to candidate the proposed solution as a remarkable option for the next generation oscilloscopes. [ABSTRACT FROM AUTHOR]

Multiresolution quantization (MQ) is used in modern equipment designed for wideband spectrum measurements with high dynamic range. Such time-domain measurement systems significantly reduce measurement time. Only basic theoretical analyses of the possible influences of MQ on the fidelity of the measured spectrum have been performed until today. Therefore, the real contribution of the method to the quality of measurement should be clarified. In this paper, a new model of quantization noise is proposed for MQ. It was derived from a model of power spectral density previously used for uniform quantization. A system with two different quantization steps used for the quantization of harmonic input signal is considered. The model suitability for such conditions is proved by simulation and confronted with experimental results. Multiresolution measurements were acquired using a dual-channel data acquisition card and personal-computer postprocessing. [ABSTRACT FROM PUBLISHER]

The paper presents a pre-processing scheme to enhance the resolution of data acquisition systems (DASs) in the presence of band-pass input signals. The proposed solution permits to acquire a seamless data stream with improved resolution and is designed to be efficient in terms of hardware requirements and processing time. In the paper, details on the designed architecture are given, along with an analytical comparison of the resolution improvement achievable with respect to existing techniques. The performance of the solution is assessed through a number of simulative and experimental tests on band-pass signals. [ABSTRACT FROM PUBLISHER]

In compressive sensing (CS), the goal is to recover signals at reduced sample rate compared to the classic Shannon–Nyquist rate. However, the classic CS theory assumes the measurements to be real-valued and have infinite bit precision. The quantization of CS measurements has been studied recently and it has been shown that accurate and stable signal acquisition is possible even when each measurement is quantized to only one single bit. There are many algorithms proposed for 1-bit compressive sensing and they work well when there is no noise in the measurements, e.g., there are no sign flips, while the performance is worsened when there are a lot of sign flips in the measurements. In this paper, we propose a robust method for recovering signals from 1-bit measurements using adaptive outlier pursuit. This method will detect the positions where sign flips happen and recover the signals using “correct” measurements. Numerical experiments show the accuracy of sign flips detection and high performance of signal recovery for our algorithms compared with other algorithms. [ABSTRACT FROM PUBLISHER]

This paper is concerned with the distributed finite-horizon filtering problem for a class of time-varying systems over lossy sensor networks. The time-varying system (target plant) is subject to randomly varying nonlinearities (RVNs) caused by environmental circumstances. The lossy sensor network suffers from quantization errors and successive packet dropouts that are described in a unified framework. Two mutually independent sets of Bernoulli distributed white sequences are introduced to govern the random occurrences of the RVNs and successive packet dropouts. Through available output measurements from not only the individual sensor but also its neighboring sensors according to the given topology, a sufficient condition is established for the desired distributed finite-horizon filter to ensure that the prescribed average filtering performance constraint is satisfied. The solution of the distributed filter gains is characterized by solving a set of recursive linear matrix inequalities. A simulation example is provided to show the effectiveness of the proposed filtering scheme. [ABSTRACT FROM AUTHOR]

An algebraic integer (AI)-based time-multiplexed row-parallel architecture and two final reconstruction step (FRS) algorithms are proposed for the implementation of bivariate AI-encoded 2-D discrete cosine transform (DCT). The architecture directly realizes an error-free 2-D DCT without using FRSs between row–column transforms, leading to an 8\,\times\,8 2-D DCT that is entirely free of quantization errors in AI basis. As a result, the user-selectable accuracy for each of the coefficients in the FRS facilitates each of the 64 coefficients to have its precision set independently of others, avoiding the leakage of quantization noise between channels as is the case for published DCT designs. The proposed FRS uses two approaches based on: 1) optimized Dempster–Macleod multipliers, and 2) expansion factor scaling. This architecture enables low-noise high-dynamic range applications in digital video processing that requires full control of the finite-precision computation of the 2-D DCT. The proposed architectures and FRS techniques are experimentally verified and validated using hardware implementations that are physically realized and verified on field-programmable gate array (FPGA) chip. Six designs, for 4-bit and 8-bit input word sizes, using the two proposed FRS schemes, have been designed, simulated, physically implemented, and measured. The maximum clock rate and block rate achieved among 8-bit input designs are 307.787 MHz and 38.47 MHz, respectively, implying a pixel rate of 8\times 307.787\approx 2.462∼GHz if eventually embedded in a real-time video-processing system. The equivalent frame rate is about 1187.35 Hz for the image size of 1920\,\times\,1080. All implementations are functional on a Xilinx Virtex-6 XC6VLX240T FPGA device. [ABSTRACT FROM AUTHOR]

Sparsity in the eigenvectors of signal covariance matrices is exploited in this paper for compression and denoising. Dimensionality reduction (DR) and quantization modules present in many practical compression schemes such as transform codecs, are designed to capitalize on this form of sparsity and achieve improved reconstruction performance compared to existing sparsity-agnostic codecs. Using training data that may be noisy a novel sparsity-aware linear DR scheme is developed to fully exploit sparsity in the covariance eigenvectors and form noise-resilient estimates of the principal covariance eigenbasis. Sparsity is effected via norm-one regularization, and the associated minimization problems are solved using computationally efficient coordinate descent iterations. The resulting eigenspace estimator is shown capable of identifying a subset of the unknown support of the eigenspace basis vectors even when the observation noise covariance matrix is unknown, as long as the noise power is sufficiently low. It is proved that the sparsity-aware estimator is asymptotically normal, and the probability to correctly identify the signal subspace basis support approaches one, as the number of training data grows large. Simulations using synthetic data and images, corroborate that the proposed algorithms achieve improved reconstruction quality relative to alternatives. [ABSTRACT FROM AUTHOR]

This paper presents a detection system for high-accuracy amplitude and phase measurements on RF signals. It is typically used to set up the low-level RF system for particle accelerators. The proposed detector employs the principle of a heterodyne receiver and uses the digital IF architecture with a high oversampling rate to increase the SNR. A discrete Fourier transform-based quadrature demodulator is used to suppress the analog-to-digital converter (ADC) quantization noise and IF harmonics. The system has been evaluated at an IF of 1 MHz and in an RF range of 500–3000 MHz. A graphical user interface is developed to display and record the measured values. The detection accuracy achieved on 500-MHz signals in a 250-kHz bandwidth is better than \pm0.0051% for the amplitude and better than \pm 0.0032^ \circ for the phase. Experimental results at different frequencies prove that the detection system can meet the demands of state-of-the-art RF control systems for modern particle accelerators. [ABSTRACT FROM PUBLISHER]