File: digital_circuit_dsp.md

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digital_circuit_dsp.md

File:	`digital_circuit_dsp.md`
Role:	Documentation
Content type:	`text/markdown`
Description:	Documentation
Class:	Ascoos OS Digital Circuit DSP Simulate a digital signal processing circuit
Author:	By Christos Drogidis
Last change:	Digital Signal Processing Pipeline
Date:	2 months ago
Size:	`8,617 bytes`

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Digital Signal Processing Pipeline ? DSP Case Study

> Case Study Code: ASCOOS-OS-CASESTUDY-SEC02786

This case study demonstrates how Ascoos OS and the TDigitalCircuitHandler class implement a complete digital signal processing (DSP) pipeline in pure PHP, without external libraries.

The pipeline includes:

generation of clean and noisy signals
Gaussian or Uniform noise injection
FIR & IIR low?pass filtering
Hann?windowed FFT
SNR, THD, SINAD, ENOB estimation
latency estimation
JSON & CSV export
logging and debugging

The result is a complete, educational, and production?ready DSP implementation suitable for IoT, embedded simulation, audio pipelines, and academic use.

Purpose

Generate a clean 440 Hz sine wave
Add noise (Gaussian or Uniform)
Apply FIR & IIR low?pass filters
Perform FFT using a Hann window
Detect peak frequency
Compute: - SNR (input, FIR, IIR) - SNR improvement (gain) - THD (Total Harmonic Distortion) - SINAD (Signal?to?Noise And Distortion) - ENOB (Effective Number Of Bits)
Export results to JSON & CSV
Log all metrics for analysis

Core Ascoos OS Classes

DSP Core

TDigitalCircuitHandler Main DSP class: filters, FFT, SNR, Gaussian noise, THD/SINAD/ENOB.

DSP Utilities

gaussianNoise() Generates Gaussian noise using Box?Muller with caching
findClosestBin() Finds the nearest FFT bin within tolerance
estimateThdSinadEnob() Computes THD, SINAD, and ENOB from FFT data

Export & Logging

toJSONFile() Exports the full DSP pipeline to JSON
toCSVFile() Exports FFT spectrum & time?domain signals
Logger Records all metrics and file paths

File Structure

The implementation is located in:

digital_circuit_dsp.php

This file includes:

signal generation
noise injection (Gaussian/Uniform)
FIR/IIR filtering
Hann?windowed FFT
SNR, THD, SINAD, ENOB
latency estimation
JSON/CSV export
logging

Architecture Diagram

????????????????????????????????????????????????????????????????????????????????
?                              ASCOOS OS KERNEL                                ?
?                     (Electronics ? DSP ? Math Engine)                        ?
????????????????????????????????????????????????????????????????????????????????
                                      ?
                                      ?
                    ????????????????????????????????????????
                    ?      TDigitalCircuitHandler          ?
                    ?  (Filters ? FFT ? Noise ? Metrics)   ?
                    ????????????????????????????????????????
                                      ?
                                      ?
         ????????????????????????????????????????????????????????????????????
         ?                         DSP Pipeline                             ?
         ????????????????????????????????????????????????????????????????????
                                      ?
                                      ?
         ????????????????????????????????????????????????????????????????????
         ? 1. Signal Generation (Clean + Noise)                             ?
         ? 2. FIR Filtering                                                 ?
         ? 3. IIR Filtering                                                 ?
         ? 4. Hann Window                                                   ?
         ? 5. FFT (Magnitude Spectrum)                                      ?
         ? 6. SNR / THD / SINAD / ENOB                                      ?
         ? 7. Latency Estimation                                            ?
         ? 8. JSON / CSV Export                                             ?
         ? 9. Logging                                                       ?
         ????????????????????????????????????????????????????????????????????
                                      ?
                                      ?
????????????????????????????????????????????????????????????????????????????????
?                           Unified DSP Output Renderer                        ?
?      (Console Summary ? JSON Data ? CSV Files ? Logs)                        ?
????????????????????????????????????????????????????????????????????????????????

Requirements

PHP ? 8.3
Installed Ascoos OS or AWES 26 Pro
Enabled classes `TDigitalCircuitHandler`, `TCircuitHandler`, and `TElectronicsHandler` via the Extras Classes Manager
Access to: - `$AOS_TMP_DATA_PATH` - `$AOS_LOGS_PATH`

Execution Flow

Initialize the DSP Handler Loads `TDigitalCircuitHandler` with logging enabled.
Generate clean signal 440 Hz sine wave, 1024 samples.
Inject noise - Gaussian (Box?Muller) - or Uniform
Apply FIR filter 3?tap moving average.
Apply IIR biquad Butterworth filter 2nd?order, cutoff 1800 Hz.
Apply Hann window Reduces spectral leakage.
Perform FFT Computes magnitude spectrum.
Detect peak frequency Finds the dominant spectral component.
Compute SNR Input, FIR, IIR + SNR gain.
Compute THD, SINAD, ENOB Using tolerance to handle leakage.
Export JSON Full dataset + metadata.
Export CSV FFT spectrum + time?domain signals.
Logging Records all metrics and file paths.

Code Example

$dsp = new TDigitalCircuitHandler([], $properties);

$noise = $dsp->gaussianNoise(0.03);
$fir   = $dsp->applyFIRFilter($firCoeffs, $noisySignal);
$iir   = $dsp->applyBiquadFilter($biquadCoeffs, $noisySignal);

$fft   = $dsp->fft($windowed, true);
$mag   = array_map([$dsp, 'complexMagnitude'], $fft);

$metrics = $dsp->estimateThdSinadEnob($fftFreqs, $fftMags, 440.0);

Expected Output

=== DSP Simulation Results ===

Peak frequency (FFT): 440.0 Hz
Max FFT magnitude   : 0.9981

SNR (input noisy)   : 29.52 dB
SNR (after FIR)     : 33.87 dB
SNR (after IIR)     : 35.12 dB

THD (approx)        : -42.1 dB
SINAD (approx)      : 33.5 dB
ENOB (approx)       : 5.27 bits

JSON exported to: /tmp/signal_dsp_demo.json
FFT CSV exported to: /tmp/signal_dsp_fft_spectrum.csv
Time CSV exported to: /tmp/signal_dsp_time_signals.csv