One of the happiest accidents in all math is the ease of transforming a function to and taking derivatives in the Fourier frequency domain. But in order to exploit this extraordinary fact without serious artefacting, and in order to be able to use a computer, we need quite a bit of extra knowledge and care. This document sets out the math behind the spectral-derivatives Python package. I touch on fundamental signal processing and calculus concepts as necessary and build upwards.
This paper presents a method for estimating the characteristics of a diffuse source from interferometric measurements in the context of SAR tomography. The proposed method is based on the use of central moments of the reflectivity density and does not use any a priori model. The method's performance is discussed as a function of antenna array parameters (resolution and ambiguity).
This material introduces the D-Subspace algorithm derived on the basis of the centralized algorithm [1], which originally addresses parameter estimation problems under a subspace constraint.
The study of 5G base station antenna array performance for self-interference reduction is derived. The line of sight signal channel model and Rayleigh channel model are developed. The relevant calculations for channel capacities are shown. This is the pre-material for this study. More results and conclusions will be presented soon.
Rebar cages are the skeletons of reinforced concrete structures. These temporary structures consist of longitudinal and transverse reinforcing bars connected by tie-wires. Given the relatively low strength of tie-wire connections, replacing tie-wires with mechanical connectors such as U-bolts can improve the stability and strength of rebar cages. This paper aims to understand the behavior of large prefabricated rebar cages reinforced with mechanical U-bolt connectors through experimental and analytical investigations. Twenty-six full-scale experimental tests are performed on five different underground pile-shaft rebar cages with tie-wire and U-bolt connectors to determine their behavior during different site handling conditions. The data obtained from the experiments are used to develop and calibrate detailed finite element models that can predict the complex response behavior of rebar cages reinforced with U-bolt connectors. The results show that U-bolt connectors can effectively ensure rebar cage integrity even under extreme loading conditions. Additionally, it is concluded that the presence of U-bolt connectors allows for the elimination of internal stiffening elements, which are common for large rebar cages, adding to the simplicity and efficiency of the construction process. The results of this study can be used as a basis for establishing analysis, design, fabrication, and handling guidelines for rebar cages.
In response to the high uncertainty of large-scale new energy output in the electrical energy system (EES) and the weak controllability of energy output at multiple time scales, this paper proposes a weak grid identification model for transient energy balance in EESs based on grid partitioning, which has an increasingly complex impact on the weak areas of transient energy balance in the sending-end network. First, the accumulation of port energy during transient faults and the propagation mechanism of port energy in the sending-end system were studied, and an EES transient energy propagation mechanism model was established. Then, considering the energy balance support requirements of nodes, an EES grid partitioning model was established. Afterward, based on the characteristics of transient energy propagation and a grid partitioning model, an identification model for weak areas of transient energy balance in EESs was constructed. Finally, based on actual operating data, numerical simulations were conducted, and the results showed that the proposed weak grid identification model for transient energy balance can meet the requirements for transient stability analysis and transient energy balance characteristic analysis during actual operation of power grids.
Henrique Buglia, Eric Sillekens, Lidia Galdino
et al.
A semi-analytical, real-time nonlinear-interference model including ASE noise in hybrid-amplified links is introduced. Combined with particle-swarm optimisation, the capacity of a hybrid-amplified 10.5 THz 117x57 km link was maximised, increasing throughput by 12% versus an EDFAs-only configuration.
This paper introduces likelihood-based and feature-based modulation recognition methods. In the feature-based modulation simulation part, instantaneous feature, cyclic spectrum, high-order cumulants, and wavelet transform features are used as the entry point, and six digital signals including 2ASK, 4ASK, BPSK, QPSK, 2FSK and 4FSK are simulated, showing the difference of signals in multiple dimensions
The wavelet transform and related techniques are used to analyze singular and fractal signals. The normalized wavelet scalogram is introduced to detect singularities including jumps, cusps and other sharply changing points. The wavelet auto-covariance is applied to estimate the self-similarity exponent for statistical self-affine signals.
We proposed and demonstrated a hybrid blind source separation system which can switch between multiple-input and multi-output mode and free space optical communication mode depends on different situation to get best condition for separation.
In this paper we consider the problem of defining transforms for signals on directed graphs, with a specific focus on defective graphs where the corresponding graph operator cannot be diagonalized. Our proposed method is based on the Schur decomposition and leads to a series of embedded invariant subspaces for which orthogonal basis are available. As compared to diffusion wavelets, our method is more flexible in the generation of subspaces, but these subspaces can only be approximately orthogonal.
We propose a method of data quantization of finite discrete-time signals which optimizes the error estimate of low frequency Haar coefficients. We also discuss the error/noise bounds of this quantization in the Fourier space. Our result shows one can quantize any discrete-time analog signal with high precision at low frequencies. Our method is deterministic, and it employs no statistical arguments, nor any probabilistic assumptions.
Multi input multi output (MIMO) systems\' capability of using seperate signals brings many advantages to radar signal processing and time frequency analysis. In this paper, a variety of properties of MIMO ambiguity functions related with representations of Heisenberg group are given. Some of the existing results for SIMO ambiguity functions are generalized to MIMO case. Combined effect of seperate signals is investigated.
We use the concept of coupled quantum harmonic oscillators to model the propagation environment in which a quantum link carrying either classical or quantum information operates. Using the analogy between the paraxial optical wave equation and the stationary Schrodinger equation and applying the Caldirola-Kanai Hamiltonian for solving the time-dependent Schrodinger equation; we calculate the propagation field strength and the corresponding average received signal energy.
Joint communications and sensing (JCS) can improve the efficiency of power, bandwidth and hardware usage. The conflict between communications and sensing is analyzed in terms of bandwidth and power. It is found that the bandwidth is approximately partitioned between communication and sensing, thus making an almost zero-sum game, while the conflict in the power is marginal. The same conclusion holds when the receiver and target are separated. The feasible region and tradeoff boundary of JCS are obtaine.
Basile de Loynes, Fabien Navarro, Baptiste Olivier
We present a short tutorial on to the use of the R gasper package. Gasper is a package dedicated to signal processing on graphs. It also provides an interface to the SuiteSparse Matrix Collection.
The recent advances in modelling nonlinear interference of systems operating beyond the C-band are discussed. Estimation accuracy as well as computational complexity of current approaches are compared and addressed.
This paper introduces a communication method that can use one information symbol to provide two sets of the independent bits to two receivers in spatial perpendicular directions. The new communication scheme is realized by switching one signal source among a linear array antenna elements, which are used to emulating a moving transmitter. The theoretical derivations are presented in the paper.
Enhanced Gaussian noise models are used to demonstrate that the per-block SNR after fibre transmission varies significantly due to the variable-composition nature of modern probabilistic shaping schemes. We propose a nonlinearity-optimised distribution matcher that improves the average and worst-case SNR by 0.14 and 0.22 dB, respectively.
In this paper the equation for the waveform of single phase PWM voltages is transformed from its Fourier series form to a variation in which the voltage in each submission band is represented as a single frequency modulated voltage.