feature: include applet for nyquist
This commit is contained in:
Matthias Jung
@@ -0,0 +1,447 @@
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<html>
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<style>
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/* ---- Applet Card ---- */
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.applet-card {
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overflow: hidden;
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}
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.applet-header {
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background: #f5f5f5;
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padding: 12px 20px;
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font-size: 14px;
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font-weight: 500;
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border-bottom: 1px solid var(--border);
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display: flex;
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align-items: center;
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}
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.applet-header .material-icons { font-size: 18px; color: var(--primary); }
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.applet-body { padding: 20px; }
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/* ---- Canvas panels ---- */
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.panel {
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margin-bottom: 16px;
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}
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.panel-label {
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margin-bottom: 6px;
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display: flex;
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align-items: center;
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gap: 6px;
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}
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.panel-label .dot {
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width: 10px; height: 10px; border-radius: 50%;
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display: inline-block;
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}
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canvas {
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display: block;
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width: 100%;
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border: 1px solid var(--border);
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border-radius: 4px;
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background: var(--canvas-bg);
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}
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/* ---- Controls ---- */
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.controls {
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background: #f9f9f9;
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border: 1px solid var(--border);
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border-radius: 6px;
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padding: 16px 20px;
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margin-bottom: 16px;
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}
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.control-row {
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display: flex;
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align-items: center;
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gap: 16px;
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flex-wrap: wrap;
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}
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.control-value {
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text-align: right;
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}
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.status-row {
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display: flex;
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align-items: center;
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gap: 12px;
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flex-wrap: wrap;
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margin-top: 12px;
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}
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.nyquist-info {
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font-size: 13px;
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color: var(--text-secondary);
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}
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/* ---- Info box ---- */
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.info-box {
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margin-top: 20px;
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padding: 14px 18px;
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background: "#DAEEFA";
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border-left: 4px solid var(--primary);
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border-radius: 0 4px 4px 0;
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}
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.info-box strong { font-weight: 700; }
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/* ---- Legend ---- */
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.legend {
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display: flex;
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gap: 20px;
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flex-wrap: wrap;
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margin-bottom: 16px;
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font-size: 13px;
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}
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.legend-item {
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display: flex;
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align-items: center;
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gap: 6px;
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}
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.legend-line {
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width: 24px; height: 3px; border-radius: 2px;
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}
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.legend-circle {
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width: 10px; height: 10px; border-radius: 50%;
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}
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/* ---- Formula ---- */
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.formula-box {
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margin-top: 20px;
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background: #263238;
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color: #eceff1;
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border-radius: 6px;
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padding: 14px 18px;
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font-size: 13px;
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line-height: 1.8;
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}
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.formula-box .comment { color: #78909c; }
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.formula-box .keyword { color: #80cbc4; }
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.formula-box .func { color: #ffcc02; }
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@media (max-width: 600px) {
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.control-row { flex-direction: column; align-items: flex-start; }
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.control-value { text-align: left; }
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}
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</style>
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<div class="applet-card">
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<div class="applet-body">
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<!-- Controls -->
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<div class="controls">
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<div class="control-row">
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<span class="control-label">Abtastrate $f_\text{s}$:</span>
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<input type="range" id="sliderFs" min="1.0" max="8.0" step="0.025" value="3.0">
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<span class="control-value" id="labelFs">3.0 kHz</span>
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</div>
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</div>
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<!-- Panel 1: Original signal -->
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<div class="panel">
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<div class="panel-label">
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<span class="dot" style="background:var(--signal-color)"></span>
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Originalsignal — Sinus mit 1kHz
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</div>
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<canvas id="canvasOriginal" height="300"></canvas>
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</div>
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<!-- Panel 2: Sampled signal -->
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<div class="panel">
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<div class="panel-label">
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<span class="dot" style="background:var(--sample-color)"></span>
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Abgetastetes Signal
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</div>
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<canvas id="canvasSampled" height="300"></canvas>
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</div>
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<!-- Panel 3: Reconstructed signal -->
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<div class="panel">
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<div class="panel-label">
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<span class="dot" style="background:var(--recon-color)"></span>
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Rekonstruiertes Signal
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</div>
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<canvas id="canvasRecon" height="300"></canvas>
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</div>
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<!-- Info box -->
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<div class="info-box" id="infoBox">
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<strong>✓ Nyquist-Bedingung erfüllt:</strong>
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f<sub>s</sub> = 3.0 kHz ≥ 2 · 1 kHz. Das rekonstruierte Signal stimmt mit dem Original überein.
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</div><br>
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</div>
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</div>
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</main>
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<script>
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// ============================================================
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// Signal- und Darstellungsparameter
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// ============================================================
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const F_SIG = 1.0; // Signalfrequenz (normiert auf 1)
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const T_SHOW = 3.0; // Angezeigte Zeitdauer in Perioden
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const N_DRAW = 1000; // Stützpunkte für analoge Kurve
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// Sinc-Funktion (normierte Version: sinc(u) = sin(πu)/(πu))
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function sinc(u) {
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if (Math.abs(u) < 1e-10) return 1.0;
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return Math.sin(Math.PI * u) / (Math.PI * u);
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}
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// Originalsignal
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function signal(t) {
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return Math.sin(2 * Math.PI * F_SIG * t);
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}
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// Whittaker-Shannon-Rekonstruktion
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function reconstruct(t, samples, fs) {
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let sum = 0;
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for (let n = 0; n < samples.length; n++) {
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sum += samples[n].y * sinc(fs * t - n);
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}
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return sum;
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}
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// ============================================================
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// Canvas-Hilfsklasse
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// ============================================================
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class Plot {
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constructor(canvas, yMin=-1.3, yMax=1.3) {
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this.canvas = canvas;
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this.yMin = yMin;
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this.yMax = yMax;
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this.resize();
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}
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resize() {
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const dpr = window.devicePixelRatio || 1;
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const rect = this.canvas.getBoundingClientRect();
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this.canvas.width = rect.width * dpr;
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this.canvas.height = this.canvas.offsetHeight * dpr;
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this.ctx = this.canvas.getContext('2d');
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this.ctx.scale(dpr, dpr);
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this.W = rect.width;
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this.H = this.canvas.offsetHeight;
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this.padL = 44; this.padR = 12;
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this.padT = 10; this.padB = 22;
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this.plotW = this.W - this.padL - this.padR;
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this.plotH = this.H - this.padT - this.padB;
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}
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// map t∈[0,T_SHOW] to pixel x
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tx(t) { return this.padL + (t / T_SHOW) * this.plotW; }
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// map y∈[yMin,yMax] to pixel y
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ty(y) { return this.padT + (1 - (y - this.yMin) / (this.yMax - this.yMin)) * this.plotH; }
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clear() {
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const ctx = this.ctx;
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ctx.clearRect(0, 0, this.W, this.H);
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// background
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ctx.fillStyle = '#fafafa';
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ctx.fillRect(this.padL, this.padT, this.plotW, this.plotH);
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// grid lines
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ctx.strokeStyle = '#e8e8e8';
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ctx.lineWidth = 1;
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for (let v of [-1, -0.5, 0, 0.5, 1]) {
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const py = this.ty(v);
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ctx.beginPath(); ctx.moveTo(this.padL, py); ctx.lineTo(this.padL + this.plotW, py);
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ctx.stroke();
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}
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// time grid
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for (let k = 0; k <= T_SHOW; k++) {
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const px = this.tx(k);
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ctx.beginPath(); ctx.moveTo(px, this.padT); ctx.lineTo(px, this.padT + this.plotH);
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ctx.stroke();
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}
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// axes
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ctx.strokeStyle = '#aaa';
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ctx.lineWidth = 1;
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ctx.strokeRect(this.padL, this.padT, this.plotW, this.plotH);
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// zero line
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ctx.strokeStyle = '#bbb';
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ctx.lineWidth = 1.5;
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const y0 = this.ty(0);
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ctx.beginPath(); ctx.moveTo(this.padL, y0); ctx.lineTo(this.padL + this.plotW, y0);
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ctx.stroke();
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// y-axis labels
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ctx.fillStyle = '#888';
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ctx.textAlign = 'right';
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for (let v of [-1, 0, 1]) {
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ctx.fillText(v.toFixed(0), this.padL - 4, this.ty(v) + 3.5);
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}
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// x-axis labels
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ctx.textAlign = 'center';
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ctx.fillStyle = '#888';
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for (let k = 0; k <= T_SHOW; k++) {
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ctx.fillText(k + 'T', this.tx(k), this.padT + this.plotH + 14);
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}
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}
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drawLine(points, color='#47ABE8', lw=2) {
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const ctx = this.ctx;
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ctx.strokeStyle = color;
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ctx.lineWidth = lw;
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ctx.lineJoin = 'round';
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ctx.beginPath();
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for (let i = 0; i < points.length; i++) {
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const px = this.tx(points[i].t);
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const py = this.ty(points[i].y);
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if (i === 0) ctx.moveTo(px, py); else ctx.lineTo(px, py);
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}
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ctx.stroke();
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}
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drawStems(samples, color='#FE756C') {
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const ctx = this.ctx;
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const y0 = this.ty(0);
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// Draw vertical stem lines
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ctx.strokeStyle = color;
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ctx.lineWidth = 1.5;
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for (const s of samples) {
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if (s.t < 0 || s.t > T_SHOW) continue;
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const px = this.tx(s.t);
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const py = this.ty(s.y);
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ctx.beginPath(); ctx.moveTo(px, y0); ctx.lineTo(px, py); ctx.stroke();
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}
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// Draw sample dots on top
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ctx.fillStyle = color;
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ctx.strokeStyle = '#fff';
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ctx.lineWidth = 1.5;
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for (const s of samples) {
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if (s.t < 0 || s.t > T_SHOW) continue;
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const px = this.tx(s.t);
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const py = this.ty(s.y);
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ctx.beginPath();
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ctx.arc(px, py, 4.5, 0, 2*Math.PI);
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ctx.fill();
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ctx.stroke();
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}
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}
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}
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// ============================================================
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// Globale Plot-Objekte
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// ============================================================
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let plotOrig, plotSamp, plotRecon;
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function initPlots() {
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plotOrig = new Plot(document.getElementById('canvasOriginal'));
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plotSamp = new Plot(document.getElementById('canvasSampled'));
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plotRecon = new Plot(document.getElementById('canvasRecon'));
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}
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// ============================================================
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// Haupt-Render-Funktion
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// ============================================================
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function render(fs) {
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// --- 1. Abtastwerte erzeugen ---
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const Ts = 1 / fs; // Abtastintervall (in Perioden des Signals)
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const nSamples = Math.floor(T_SHOW * fs) + 2;
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const samples = [];
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for (let n = 0; n < nSamples; n++) {
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const t = n * Ts;
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samples.push({ t, y: signal(t) });
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}
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// --- 2. Analoge Kurve erzeugen ---
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const analogPts = [];
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for (let i = 0; i <= N_DRAW; i++) {
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const t = (i / N_DRAW) * T_SHOW;
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analogPts.push({ t, y: signal(t) });
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}
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// --- 3. Rekonstruktion (Sinc-Interpolation) ---
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const reconPts = [];
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for (let i = 0; i <= N_DRAW; i++) {
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const t = (i / N_DRAW) * T_SHOW;
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reconPts.push({ t, y: reconstruct(t, samples, fs) });
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}
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// --- 4. Panel 1: Original ---
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plotOrig.clear();
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plotOrig.drawLine(analogPts, '#47ABE8', 2.2);
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// --- 5. Panel 2: Samples (analog + stems) ---
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plotSamp.clear();
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plotSamp.drawLine(analogPts, '#47ABE8', 1.5); // leicht gedämpft im Hintergrund
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plotSamp.drawStems(samples, '#FE756C');
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// --- 6. Panel 3: Rekonstruktion ---
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const nyquistOk = fs >= 2 * F_SIG;
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const reconColor = nyquistOk ? '#3BB583' : '#FE756C';
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plotRecon.clear();
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// Original als gestrichelte Referenz
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const ctx = plotRecon.ctx;
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ctx.save();
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ctx.setLineDash([5, 5]);
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plotRecon.drawLine(analogPts, '#47ABE8', 1.2);
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ctx.setLineDash([]);
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ctx.restore();
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// Rekonstruiertes Signal
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plotRecon.drawLine(reconPts, reconColor, 2.2);
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// --- 7. UI-Updates ---
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updateUI(fs, nyquistOk);
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}
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function updateUI(fs, ok) {
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const infoBox = document.getElementById('infoBox');
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const ratio = (fs / F_SIG).toFixed(2);
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const fAlias = Math.abs(fs - F_SIG).toFixed(2); // Aliasing-Frequenz (vereinfacht)
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if (ok) {
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infoBox.style.borderLeftColor = '#1565c0';
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infoBox.style.background = '#DAEEFA';
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infoBox.innerHTML =
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`<strong>✓ Nyquist-Bedingung erfüllt:</strong> ` +
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`f<sub>s</sub> = ${fs.toFixed(2)} kHz ≥ 2 · ${F_SIG} kHz = ${(2*F_SIG).toFixed(2)} kHz. ` +
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`Das rekonstruierte Signal stimmt mit dem Original überein.`;
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} else {
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infoBox.style.borderLeftColor = '#c62828';
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infoBox.style.background = '#FFE3E2';
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infoBox.innerHTML =
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`<strong>⚠ Aliasing:</strong> f<sub>s</sub> = ${fs.toFixed(2)} kHz < 2 · ${F_SIG} kHz. ` +
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`Das rekonstruierte Signal erscheint mit Aliasing-Frequenz ` +
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`f<sub>Alias</sub> = |f<sub>s</sub> − f<sub>Signal</sub>| ≈ ${fAlias} kHz. ` +
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`Erhöhe die Abtastrate über ${(2*F_SIG).toFixed(1)} kHz, um das Signal korrekt darzustellen.`;
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}
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}
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// ============================================================
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// Event-Listener & Init
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// ============================================================
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const slider = document.getElementById('sliderFs');
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const labelFs = document.getElementById('labelFs');
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slider.addEventListener('input', () => {
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const fs = parseFloat(slider.value);
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labelFs.textContent = fs.toFixed(2) + ' kHz';
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render(fs);
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});
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function onResize() {
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if (!plotOrig || !plotSamp || !plotRecon) return;
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plotOrig.resize();
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plotSamp.resize();
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plotRecon.resize();
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render(parseFloat(slider.value));
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}
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window.addEventListener('resize', onResize);
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// Erst nach dem Laden initialisieren, wenn Canvas-Dimensionen bekannt sind
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window.addEventListener('load', () => {
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initPlots();
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const fs = parseFloat(slider.value);
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labelFs.textContent = fs.toFixed(2) + ' kHz';
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render(fs);
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});
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</script>
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</html>
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Reference in New Issue
Block a user