<?php
/**
* @ASCOOS-NAME : Ascoos OS
* @ASCOOS-VERSION : 1.0.0
* @ASCOOS-SUPPORT : support@ascoos.com
* @ASCOOS-BUGS : https://issues.ascoos.com
*
* @CASE-STUDY : digital_circuit_dsp.php
* @fileNo : ASCOOS-OS-CASESTUDY-SEC02786
*
* @desc <English>
* Simulates a digital signal processing pipeline: generates a clean 440 Hz sine + noisy version (uniform or Gaussian),
* applies FIR & IIR low-pass filters, performs Hann-windowed FFT, estimates SNR improvement, THD, SINAD, ENOB and latency,
* exports results to JSON/CSV ? for IoT/embedded DSP prototyping.
* @desc <Greek>
* ???????????? ????? ???????? ???????????? ???????: ?????????? ?????? ???????????? 440 Hz + ????????? ???? (?????????? ? Gaussian),
* ????????? FIR & IIR low-pass ??????, ??????? FFT ?? ???????? Hann, ?????????? ???????? SNR, THD, SINAD, ENOB ??? ???????????,
* ?????? ???????????? ?? JSON/CSV ? ??? ????????? IoT/embedded DSP.
*
* @since PHP 8.3.0+
*/
declare(strict_types=1);
use ASCOOS\OS\Kernel\Science\Electronics\TDigitalCircuitHandler;
$properties = [
'logs' => [
'useLogger' => true,
'dir' => $AOS_LOGS_PATH,
'file' => 'dsp_simulation_improved.log'
]
];
try {
$dHandler = new TDigitalCircuitHandler([], $properties);
// ????????????????????????????????????????????????
// 1. <English> Test signal generation (clean + noisy)
// <Greek> ?????????? ???????????? ??????? (?????? + ?????????)
// ????????????????????????????????????????????????
$fs = 8000.0; // Sampling frequency (Hz)
$N = 1024; // Number of samples (power-of-2 for FFT)
$cleanSignal = []; // Pure 440 Hz sine
$noisySignal = []; // Sine + noise
$timeVector = []; // Time axis
$noiseScale = 0.03; // ~30 dB below main tone (for uniform)
$noiseStdDev = 0.03; // ~30 dB below main tone (for Gaussian)
$noiseType = 'gaussian'; // 'uniform' or 'gaussian'
for ($i = 0; $i < $N; $i++) {
$t = $i / $fs;
$s = sin(2 * M_PI * 440.0 * $t); // 440 Hz sine
if ($noiseType === 'gaussian') {
// Gaussian noise with stdDev = $noiseStdDev
$noise = $dHandler->gaussianNoise($noiseStdDev);
} else {
// Uniform noise in [-1, 1) then scaled
$noise = $noiseScale * ((mt_rand() / mt_getrandmax() - 0.5) * 2.0);
}
$timeVector[] = $t;
$cleanSignal[] = $s;
$noisySignal[] = $s + $noise;
}
// ????????????????????????????????????????????????
// 2. <English> FIR low-pass filtering (3-tap moving average)
// <Greek> FIR low-pass ??????????? (3-tap ?????????? ?????)
// ????????????????????????????????????????????????
$firCoeffs = [0.25, 0.5, 0.25]; // Simple triangular FIR
$firFiltered = $dHandler->applyFIRFilter($firCoeffs, $noisySignal);
// Group delay ~ (M-1)/2 samples
$firDelaySamples = (count($firCoeffs) - 1) / 2.0;
$firDelaySeconds = $firDelaySamples / $fs;
// ????????????????????????????????????????????????
// 3. <English> IIR biquad low-pass Butterworth (2nd order @ 1800 Hz)
// <Greek> IIR biquad low-pass Butterworth (2?? ????? @ 1800 Hz)
// ????????????????????????????????????????????????
$fc = 1800.0; // Cutoff frequency
$Q = 1 / sqrt(2); // ?0.7071 ? Butterworth
$biquadCoeffs = $dHandler->biquadLowpassCoefficients($fc, $Q, $fs);
$iirFiltered = $dHandler->applyBiquadFilter($biquadCoeffs, $noisySignal);
// Approximate latency: 1 sample (implementation-dependent)
$iirDelaySamples = 1.0;
$iirDelaySeconds = $iirDelaySamples / $fs;
// ????????????????????????????????????????????????
// 4. <English> Hann-windowed FFT analysis (reducing spectral leakage)
// <Greek> ??????? FFT ?? ???????? Hann (?????? spectral leakage)
// ????????????????????????????????????????????????
$hannWindow = [];
for ($i = 0; $i < $N; $i++) {
$hannWindow[] = 0.5 * (1.0 - cos(2.0 * M_PI * $i / ($N - 1)));
}
$windowedSignal = [];
for ($i = 0; $i < $N; $i++) {
$windowedSignal[] = $noisySignal[$i] * $hannWindow[$i];
}
$fftComplex = $dHandler->fft($windowedSignal, true); // Normalized FFT
$fftMagnitude = array_map([$dHandler, 'complexMagnitude'], $fftComplex);
// Keep only positive spectrum [0, fs/2]
$halfLength = (int)($N / 2) + 1;
$fftMags = array_slice($fftMagnitude, 0, $halfLength);
$fftFreqs = [];
$df = $fs / $N;
for ($i = 0; $i < $halfLength; $i++) {
$fftFreqs[] = $i * $df;
}
// Peak frequency detection
$maxMag = max($fftMags);
$peakIdx = array_search($maxMag, $fftMags, true);
$peakFreq = $fftFreqs[$peakIdx] ?? 0.0;
// ????????????????????????????????????????????????
// 5. <English> SNR estimation (input vs FIR vs IIR)
// <Greek> ???????? SNR (??????? vs FIR vs IIR)
// ????????????????????????????????????????????????
$snrInput = $dHandler->SNRdB($cleanSignal, $noisySignal); // SNR before filtering
$snrFIR = $dHandler->SNRdB($cleanSignal, $firFiltered); // SNR after FIR
$snrIIR = $dHandler->SNRdB($cleanSignal, $iirFiltered); // SNR after IIR
$snrFirGain = $snrFIR - $snrInput;
$snrIirGain = $snrIIR - $snrInput;
// ????????????????????????????????????????????????
// 5b. <English> THD, SINAD, ENOB estimation (from FFT)
// <Greek> ???????? THD, SINAD, ENOB ??? FFT
// ????????????????????????????????????????????????
$dspMetrics = $dHandler->estimateThdSinadEnob($fftFreqs, $fftMags, 440.0, 5, 1.5);
$thdDb = $dspMetrics['thd_db'];
$sinadDb = $dspMetrics['sinad_db'];
$enob = $dspMetrics['enob_bits'];
// ????????????????????????????????????????????????
// 6. <English> Console summary of key results
// <Greek> ???????? ??????? ????????????? ???? ???????
// ????????????????????????????????????????????????
echo "DSP Simulation Results / ???????????? DSP\n";
echo "??????????????????????????????????????????\n";
echo "Signal length : $N samples\n";
echo "Sampling rate : {$fs} Hz\n";
echo "Noise type : {$noiseType}\n";
echo "Peak frequency (FFT) : " . round($peakFreq, 1) . " Hz\n";
echo "Max FFT magnitude : " . round($maxMag, 4) . "\n\n";
echo "SNR (input noisy) : " . ($snrInput === INF ? "INF" : round($snrInput, 2)) . " dB\n";
echo "SNR (after FIR) : " . ($snrFIR === INF ? "INF" : round($snrFIR, 2)) . " dB\n";
echo "SNR (after IIR) : " . ($snrIIR === INF ? "INF" : round($snrIIR, 2)) . " dB\n\n";
echo "SNR gain (FIR) : " . (is_nan($snrFirGain) ? "NaN" : round($snrFirGain, 2)) . " dB\n";
echo "SNR gain (IIR) : " . (is_nan($snrIirGain) ? "NaN" : round($snrIirGain, 2)) . " dB\n\n";
echo "THD (approx) : " . (is_nan($thdDb) ? "NaN" : round($thdDb, 2)) . " dB\n";
echo "SINAD (approx) : " . (is_nan($sinadDb) ? "NaN" : round($sinadDb, 2)) . " dB\n";
echo "ENOB (approx) : " . (is_nan($enob) ? "NaN" : round($enob, 3)) . " bits\n\n";
echo "FIR delay : " . round($firDelaySamples, 2) . " samples (" . round($firDelaySeconds * 1e3, 3) . " ms)\n";
echo "IIR delay (approx) : " . round($iirDelaySamples, 2) . " samples (" . round($iirDelaySeconds * 1e3, 3) . " ms)\n\n";
echo "FIR first 5 samples : " . json_encode(array_slice($firFiltered, 0, 5), JSON_NUMERIC_CHECK) . "\n";
echo "IIR biquad coeffs : " . json_encode($biquadCoeffs, JSON_NUMERIC_CHECK) . "\n\n";
// ????????????????????????????????????????????????
// 7. <English> Export full data to JSON
// <Greek> ??????? ?????? ????????? ?? JSON
// ????????????????????????????????????????????????
$jsonExportPath = $AOS_TMP_DATA_PATH . '/signal_dsp_demo.json';
$dHandler->toJSONFile($jsonExportPath, [
'fs' => $fs,
'N' => $N,
'time' => $timeVector,
'signals' => [
'clean' => $cleanSignal,
'noisy' => $noisySignal,
'fir' => $firFiltered,
'iir' => $iirFiltered,
],
'fft' => [
'freq' => $fftFreqs,
'mag' => $fftMags,
'window' => 'Hann',
],
'snr_db' => [
'input_noisy' => $snrInput,
'fir' => $snrFIR,
'iir' => $snrIIR,
],
'snr_improvement' => [
'fir_gain_db' => $snrFirGain,
'iir_gain_db' => $snrIirGain,
],
'latency' => [
'fir' => [
'samples' => $firDelaySamples,
'seconds' => $firDelaySeconds,
],
'iir' => [
'samples' => $iirDelaySamples,
'seconds' => $iirDelaySeconds,
],
],
'dsp_metrics' => [
'thd_db' => $thdDb,
'sinad_db' => $sinadDb,
'enob_bits' => $enob,
],
'metadata' => [
'peak_frequency_hz' => $peakFreq,
'generated_at' => date('c'),
'description_en' => 'DSP demo: 440 Hz sine, noise ('
. $noiseType . '), FIR/IIR low-pass, Hann FFT, SNR, THD, SINAD, ENOB & latency estimation.',
'description_gr' => 'Demo DSP: ???????????? 440 Hz, ??????? ('
. $noiseType . '), FIR/IIR low-pass, FFT Hann, ???????? SNR, THD, SINAD, ENOB & ????????????.',
'filters' => [
'fir_coeffs' => $firCoeffs,
'iir_cutoff_hz'=> $fc,
'iir_Q' => $Q,
'iir_coeffs' => $biquadCoeffs,
],
'plot_suggestions' => [
'time-domain: clean vs noisy vs FIR vs IIR',
'frequency-domain: FFT magnitude with 440 Hz peak',
'SNR evolution: input vs FIR vs IIR',
'DSP metrics: THD / SINAD / ENOB vs configuration',
],
],
]);
echo "JSON results exported to: $jsonExportPath\n";
// ????????????????????????????????????????????????
// 8. <English> Export selected data to CSV (FFT spectrum & time-domain)
// <Greek> ??????? ??????????? ????????? ?? CSV (????? FFT & ??????? ?????)
// ????????????????????????????????????????????????
// 8a. FFT spectrum CSV
$fftCsvPath = $AOS_TMP_DATA_PATH . '/signal_dsp_fft_spectrum.csv';
$fftHeader = [
'freq_hz',
'magnitude',
];
$fftRows = [];
for ($i = 0; $i < $halfLength; $i++) {
$fftRows[] = [
$fftFreqs[$i],
$fftMags[$i],
];
}
$dHandler->toCSVFile($fftCsvPath, $fftRows, $fftHeader, ',');
echo "FFT spectrum exported to: $fftCsvPath\n";
// 8b. Time-domain signals CSV
$timeCsvPath = $AOS_TMP_DATA_PATH . '/signal_dsp_time_signals.csv';
$timeHeader = [
't_seconds',
'clean',
'noisy',
'fir',
'iir',
];
$timeRows = [];
for ($i = 0; $i < $N; $i++) {
$timeRows[] = [
$timeVector[$i],
$cleanSignal[$i],
$noisySignal[$i],
$firFiltered[$i] ?? null,
$iirFiltered[$i] ?? null,
];
}
$dHandler->toCSVFile($timeCsvPath, $timeRows, $timeHeader, ',');
echo "Time-domain signals exported to: $timeCsvPath\n";
// ????????????????????????????????????????????????
// 9. <English> Logging summary
// <Greek> ?????? ??? log
// ????????????????????????????????????????????????
$dHandler->logger?->log(
sprintf(
"DSP simulation completed | N=%d | noise=%s | peak=%.1f Hz | max_mag=%.4f | ". "SNR_in=%.2f dB | SNR_FIR=%.2f dB | SNR_IIR=%.2f dB | ".
"THD=%.2f dB | SINAD=%.2f dB | ENOB=%.3f bits | ".
"JSON=%s | FFT_CSV=%s | TIME_CSV=%s",
$N,
$noiseType,
$peakFreq,
$maxMag,
$snrInput,
$snrFIR,
$snrIIR,
$thdDb,
$sinadDb,
$enob,
$jsonExportPath,
$fftCsvPath,
$timeCsvPath
),
$dHandler::DEBUG_LEVEL_INFO
);
} catch (Throwable $e) {
echo "Error / ??????: " . $e->getMessage() . "\n";
if (isset($dHandler) && $dHandler->logger) {
$dHandler->logger->log(
"DSP simulation failed: " . $e->getMessage(),
$dHandler::DEBUG_LEVEL_ERROR
);
}
} finally {
// ????????????????????????????????????????????????
// 10. <English> Resources Release
// <Greek> ???????????? ?????
// ????????????????????????????????????????????????
if (isset($dHandler)) {
$dHandler->Free();
}
}
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