Mathuranathan

Spectrogram Analysis using Python

by

Keywords: Spectrogram, signal processing, time-frequency analysis, speech recognition, music analysis, frequency domain, time domain, python Introduction A spectrogram is a visual representation of the frequency content of a signal over time. Spectrograms are widely used in signal processing applications to analyze and visualize time-varying signals, such as speech and audio signals. In this article, we … Read more

Volterra series formula for RF power amplifiers — kernels, memory, and nonlinearity

by

RF nonlinearity path: Volterra PA model → π/2-BPSK PAPR → EVM → SNR In one sentence: A Volterra series formula extends a Taylor polynomial with memory kernels so the PA output depends on the present input and recent past samples — the regime of wideband 4G/5G waveforms. Matlab/Python simulation: Use this model when you move … Read more

Near-field – far-field : Where is the boundary ?

by

Antenna models — reading order Maxwell’s equations Retarded potentials Near-field / far-field boundary (this article) Far-field retarded potentials Array pattern multiplication Dipole power gain patterns Introduction Antenna fields change character with distance: reactive storage near the element, Fresnel diffraction at intermediate range, and spherical-wave radiation farther out. Link-budget and pattern formulas almost always assume that … Read more

From Maxwell’s equations to antenna array – part 1

by

Antenna models — reading order Maxwell’s equations (this article) Retarded potentials Near-field / far-field boundary Far-field retarded potentials Array pattern multiplication Dipole power gain patterns Introduction Antenna theory is Maxwell’s equations plus boundary conditions and a far-field approximation. Before retarded potentials and array factors, write the four laws carefully—especially Ampère’s law with Maxwell’s displacement current. … Read more

Normalized power gain of dipole antennas

by

Antenna models — reading order Maxwell’s equations Retarded potentials Near-field / far-field boundary Far-field retarded potentials Array pattern multiplication Dipole power gain patterns (this article) Introduction You have almost certainly seen the short-dipole pattern: nulls along the wire, maximum broadside. We will derive the normalised power patterns for the Hertzian dipole, the half-wave dipole, and … Read more