Estimation of parameters of a sum of sinusoids sampled below the Nyquist rate with frequencies away from the grid

We are witnessing a growing interest in processing signals sampled below the Nyquist rate. The main limitation of current approaches considering estimation of multicomponent sinusoids parameters is the assumption of frequencies on the frequency grid. The sinusoids away from the frequency grid are considered in this paper. The proposed procedure has three stages. In the first two, a rough estimation of signal components is performed while in the third refinement in estimation is achieved in a component-by-component manner. We have tested the developed technique on an extended set of simulation examples showing excellent accuracy. Three scenarios are considered in experiments: missing samples, noisy environment, and non-uniform sampling below the Nyquist rate.

Adaptive Sparse Cyclic Coordinate Descent for Sparse Frequency Estimation

The frequency estimation of multiple complex sinusoids in the presence of noise is important for many signal processing applications. As already discussed in the literature, this problem can be reformulated as a sparse representation problem. In this letter, such a formulation is derived and an algorithm based on sparse cyclic coordinate descent (SCCD) for estimating the frequency parameters is proposed. The algorithm adaptively reduces the size of the used frequency grid, which eases the computational burden. Simulation results revealed that the proposed algorithm achieves similar performance to the original formulation and the Root-multiple signal classification (MUSIC) algorithm in terms of the mean square error (MSE), with significantly less complexity.

Elastic Optical Networks

In WDM networks using a fixed frequency grid, transmission rates can vary for different connections, leading to inefficient bandwidth utilization in optical fibers with lower-rate connections using wide frequency slots. In elastic optical networks (EONs), the frequency grid is made flexible, thereby improving the effective network capacity. A flexible frequency grid consists of smaller frequency slots, and a transmitting node can use multiple slots using suitable modulation techniques, such as optical OFDM, Nyquist-WDM and optical arbitrary waveform generation (OAWG). However, this requires bandwidth-variable transceivers (BVTs) and other devices to set up variable-rate connections. First we discuss the design challenges in EONs and describe the evolving technologies for the network elements. Then we present some offline (LP-based and heuristic) design methodologies for EONs to carry out routing and spectral allocation (RSA) for the required connections. Finally, we present some online fragmentation-aware RSA schemes for the operational EONs. (146 words)

Distribution Grid Stability—Influence of Inertia Moment of Synchronous Machines

This paper shows the influence of grid frequency oscillations on synchronous machines coupled to masses with large moments of inertia and solves the maximum permissible value of a moment of inertia on the shaft of a synchronous machine in respect to the oscillation of grid frequency. Grid frequency variation causes a load angle to swing on the synchronous machines connected to the grid. This effect is particularly significant in microgrids. This article does not consider the effects of other components of the system, such as the effects of frequency, voltage, and power regulators.

Effects of local oscillator on the performance of DP-QPSK WDM system with channel spacing of 37.5 GHz

Dual-polarization quadrature phase shift keying (DP-QPSK) modulation format is emerging as a main contender for 37.5 GHz frequency grid of WDM systems. However, the optical add drop multiplexers (OADMs) affect the performance of the system because of narrow channel spacing. The local oscillator (LO) is an important component of the digital coherent receiver. This paper analyzes the effects of LO parameter on the performance of the considered system. It is exhibited that optimum range of optical power and laser linewidth of the LO helps in improving the performance of the considered system.

Control and Application of Single-phase PWM Rectifier in Aircraft Electric Systems

This work studies the use of single-phase high power factor PWM rectifiers in aircrafts with variable frequency (360 to 800 Hz) power generation. It also presents design guidelines for input and output filters, and discusses the modeling and design of the voltage and current controllers. A 1 kW system is simulated considering a variable frequency grid, verifying the compliance with the aircraft power quality standards. Experimental results from a prototype allows to verify the design procedures.