ZeroSignal.Core 1.0.0

ZeroSignal

ZeroSignal is an advanced Digital Signal Processing (DSP), spectral analysis, and state estimation library for .NET with zero external dependencies. Written in pure C#, it delivers industrial-grade Fast Fourier Transforms (FFT), Short-Time Fourier Transforms (STFT), spectrogram generation, zero-phase IIR/FIR digital filtering (FiltFilt), Kalman filtering (EKF), and wavelet transforms for predictive maintenance and edge telemetry.

🌟 Key Capabilities

• Spectral Analysis (ZeroSignal.Core.Spectral):
  • Radix-2 Cooley-Tukey in-place FFT / IFFT with bit-reversal permutations.
  • STFT (Short-Time Fourier Transform): Windowed time-frequency analysis with configurable hop sizes.
  • 2D Spectrogram Calculation: Power spectral density (PSD) with Hann, Hamming, Blackman, and Bartlett window functions.
• Zero-Phase Digital Filtering (ZeroSignal.Core.Filtering):
  • Butterworth IIR Filters: Lowpass, Highpass, Bandpass, Bandstop designs.
  • Zero-Phase FiltFilt: Forward-backward digital filtering eliminating phase delay distortion.
  • Savitzky-Golay & Median Smoothing: Polynomial moving filter preserving peak heights and edges.
• Sensor Fusion & State Estimation (ZeroSignal.Core.Estimation):
  • Linear Kalman Filter for Gaussian noise suppression.
  • Extended Kalman Filter (EKF): Non-linear dynamic system tracking with numerical central-difference Jacobians and Gauss-Jordan matrix inversion.
• Wavelets & Curve Fitting (ZeroSignal.Core.Wavelets & Optimization):
  • Continuous (CWT) & Discrete (DWT) Wavelet Transforms (Morlet, Ricker, Haar).
  • Levenberg-Marquardt non-linear least squares optimization.
• Zero External Dependencies: Standard .NET runtime only.

📦 Installation

Install via the .NET CLI:

dotnet add package ZeroSignal.Core

🚀 Quick Start

1. In-Place FFT & Power Spectrum

using ZeroSignal.Core.Spectral;

// Sample 1024-point signal with 50Hz and 120Hz tones
int n = 1024;
var real = new double[n];
var imag = new double[n];

for (int i = 0; i < n; i++)
{
    double t = i / 1000.0; // 1kHz sample rate
    real[i] = Math.Sin(2 * Math.PI * 50 * t) + 0.5 * Math.Sin(2 * Math.PI * 120 * t);
}

// Compute FFT
FastFourierTransform.Fft(real, imag);

// Extract magnitude spectrum
var magnitudes = FastFourierTransform.Magnitude(real, imag);
Console.WriteLine($"Peak frequency bin identified: {magnitudes.Length} bins computed.");

2. Zero-Phase Butterworth Lowpass Filtering (FiltFilt)

using ZeroSignal.Core.Filtering;

var noisySignal = new double[] { /* Raw sensor samples */ };

// 4th-order Butterworth lowpass at 20Hz cutoff (sampling rate: 200Hz)
var filter = ButterworthFilter.CreateLowpass(order: 4, sampleRate: 200.0, cutoffFreq: 20.0);

// Filter forward and backward with zero phase distortion
var cleanSignal = filter.FiltFilt(noisySignal);

3. Non-Linear Extended Kalman Filter (EKF)

using ZeroSignal.Core.Estimation;

var ekf = new ExtendedKalmanFilter(
    stateDim: 2,
    measDim: 1,
    stateTransition: (x, dt) => new double[] { x[0] + x[1] * dt, x[1] },
    measurementModel: x => new double[] { Math.Sin(x[0]) }
);

ekf.Predict(dt: 0.01);
ekf.Update(new double[] { 0.52 });

📊 Benchmark & Performance

Tested on Intel Core i7-13700K (Release x64):

📄 License

MIT License © 2026 Phong Võ. Part of the ZeroPlatform project.