feat(highcharts): implement smith-chart-basic (#3874)

## Implementation: `smith-chart-basic` - highcharts

Implements the **highcharts** version of `smith-chart-basic`.

**File:** `plots/smith-chart-basic/implementations/highcharts.py`

**Parent Issue:** #3792

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/21047489104)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/smith-chart-basic/implementations/highcharts.py

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+""" pyplots.ai
+smith-chart-basic: Smith Chart for RF/Impedance
+Library: highcharts unknown | Python 3.13.11
+Quality: 91/100 | Created: 2026-01-15
+"""
+
+import tempfile
+import time
+import urllib.request
+from pathlib import Path
+
+import numpy as np
+from highcharts_core.chart import Chart
+from highcharts_core.options import HighchartsOptions
+from highcharts_core.options.series.scatter import ScatterSeries
+from selenium import webdriver
+from selenium.webdriver.chrome.options import Options
+
+
+# Reference impedance
+Z0 = 50.0
+
+# Generate example impedance data: antenna impedance sweep 1-6 GHz
+np.random.seed(42)
+n_points = 50
+frequencies = np.linspace(1e9, 6e9, n_points)  # 1-6 GHz
+
+# Simulate a resonant antenna with varying impedance
+# Near resonance around 3.5 GHz, impedance passes through Z0
+f_res = 3.5e9
+Q = 5.0
+f_norm = (frequencies - f_res) / (f_res / Q)
+z_real = Z0 * (1 + 0.3 * np.exp(-(f_norm**2)))
+z_imag = Z0 * 0.8 * np.tanh(f_norm) * (1 + 0.2 * np.sin(2 * np.pi * frequencies / 1e9))
+
+# Normalize impedance and convert to reflection coefficient (gamma)
+z_normalized = (z_real + 1j * z_imag) / Z0
+gamma = (z_normalized - 1) / (z_normalized + 1)
+
+# Convert gamma to Cartesian coordinates for plotting
+gamma_x = gamma.real
+gamma_y = gamma.imag
+
+
+def resistance_circle(r, n_points=200):
+    """Generate points for a constant resistance circle on Smith chart."""
+    center_x = r / (r + 1)
+    radius = 1 / (r + 1)
+    theta = np.linspace(0, 2 * np.pi, n_points)
+    x = center_x + radius * np.cos(theta)
+    y = radius * np.sin(theta)
+    # Clip to unit circle
+    valid = x**2 + y**2 <= 1.001
+    x[~valid] = np.nan
+    y[~valid] = np.nan
+    return x, y
+
+
+def reactance_arc(x_val, n_points=200):
+    """Generate points for a constant reactance arc on Smith chart."""
+    if abs(x_val) < 0.001:
+        return np.array([-1, 1]), np.array([0, 0])
+    # Center at (1, 1/x), radius |1/x|
+    center_y = 1.0 / x_val
+    radius = abs(1.0 / x_val)
+    # Full circle parametrization
+    theta = np.linspace(0, 2 * np.pi, n_points)
+    x = 1.0 + radius * np.cos(theta)
+    y = center_y + radius * np.sin(theta)
+    # Clip to unit circle
+    valid = x**2 + y**2 <= 1.001
+    x[~valid] = np.nan
+    y[~valid] = np.nan
+    return x, y
+
+
+# Create chart
+chart = Chart(container="container")
+chart.options = HighchartsOptions()
+
+# Chart configuration for square 1:1 aspect ratio Smith chart
+chart.options.chart = {
+    "width": 3600,
+    "height": 3600,
+    "backgroundColor": "#ffffff",
+    "spacingTop": 100,
+    "spacingBottom": 200,
+    "spacingLeft": 100,
+    "spacingRight": 100,
+}
+
+# Title
+chart.options.title = {
+    "text": "smith-chart-basic · highcharts · pyplots.ai",
+    "style": {"fontSize": "48px", "fontWeight": "bold"},
+}
+
+chart.options.subtitle = {"text": "Antenna Impedance Sweep 1-6 GHz (Z₀ = 50Ω)", "style": {"fontSize": "32px"}}
+
+# Axes with 1:1 aspect ratio for circular chart
+chart.options.x_axis = {
+    "title": {"text": "Real(Γ)", "style": {"fontSize": "28px"}},
+    "labels": {"style": {"fontSize": "22px"}},
+    "min": -1.2,
+    "max": 1.2,
+    "tickInterval": 0.5,
+    "gridLineWidth": 0,
+    "lineWidth": 0,
+}
+
+chart.options.y_axis = {
+    "title": {"text": "Imag(Γ)", "style": {"fontSize": "28px"}},
+    "labels": {"style": {"fontSize": "22px"}},
+    "min": -1.2,
+    "max": 1.2,
+    "tickInterval": 0.5,
+    "gridLineWidth": 0,
+    "lineWidth": 0,
+}
+
+# Legend configuration
+chart.options.legend = {
+    "enabled": True,
+    "itemStyle": {"fontSize": "24px"},
+    "verticalAlign": "bottom",
+    "layout": "horizontal",
+    "align": "center",
+    "y": 60,
+}
+
+# Unit circle (|Γ| = 1) - the boundary
+theta = np.linspace(0, 2 * np.pi, 300)
+unit_x = np.cos(theta)
+unit_y = np.sin(theta)
+unit_circle = ScatterSeries()
+unit_circle.data = [[float(x), float(y)] for x, y in zip(unit_x, unit_y, strict=True)]
+unit_circle.name = "Unit Circle"
+unit_circle.marker = {"enabled": False}
+unit_circle.line_width = 3
+unit_circle.color = "#333333"
+unit_circle.enable_mouse_tracking = False
+unit_circle.show_in_legend = False
+chart.add_series(unit_circle)
+
+# Resistance circles (R = 0, 0.2, 0.5, 1, 2, 5)
+resistance_values = [0, 0.2, 0.5, 1, 2, 5]
+for r in resistance_values:
+    rx, ry = resistance_circle(r, 300)
+    # Remove NaN values and split into valid segments
+    valid_mask = ~np.isnan(rx) & ~np.isnan(ry)
+    rx_valid = rx[valid_mask]
+    ry_valid = ry[valid_mask]
+    if len(rx_valid) > 1:
+        r_series = ScatterSeries()
+        r_series.data = [[float(x), float(y)] for x, y in zip(rx_valid, ry_valid, strict=True)]
+        r_series.name = f"R={r}"
+        r_series.marker = {"enabled": False}
+        r_series.line_width = 1.5
+        r_series.color = "#306998"
+        r_series.dash_style = "Dot"
+        r_series.enable_mouse_tracking = False
+        r_series.show_in_legend = False
+        chart.add_series(r_series)
+
+# Reactance arcs (X = ±0.2, ±0.5, ±1, ±2)
+reactance_values = [0.2, 0.5, 1, 2, -0.2, -0.5, -1, -2]
+for x_val in reactance_values:
+    xa, ya = reactance_arc(x_val, 300)
+    valid_mask = ~np.isnan(xa) & ~np.isnan(ya)
+    xa_valid = xa[valid_mask]
+    ya_valid = ya[valid_mask]
+    if len(xa_valid) > 1:
+        x_series = ScatterSeries()
+        x_series.data = [[float(x), float(y)] for x, y in zip(xa_valid, ya_valid, strict=True)]
+        x_series.name = f"X={x_val}"
+        x_series.marker = {"enabled": False}
+        x_series.line_width = 1.5
+        x_series.color = "#B8860B"
+        x_series.dash_style = "Dot"
+        x_series.enable_mouse_tracking = False
+        x_series.show_in_legend = False
+        chart.add_series(x_series)
+
+# Horizontal axis (X = 0)
+h_axis = ScatterSeries()
+h_axis.data = [[-1.0, 0.0], [1.0, 0.0]]
+h_axis.name = "Real Axis"
+h_axis.marker = {"enabled": False}
+h_axis.line_width = 2
+h_axis.color = "#333333"
+h_axis.enable_mouse_tracking = False
+h_axis.show_in_legend = False
+chart.add_series(h_axis)
+
+# VSWR circles (constant |Γ|)
+vswr_values = [1.5, 2.0, 3.0]
+vswr_colors = ["#9467BD", "#17BECF", "#8C564B"]
+for i, vswr in enumerate(vswr_values):
+    gamma_mag = (vswr - 1) / (vswr + 1)
+    v_theta = np.linspace(0, 2 * np.pi, 150)
+    vx = gamma_mag * np.cos(v_theta)
+    vy = gamma_mag * np.sin(v_theta)
+    vswr_series = ScatterSeries()
+    vswr_series.data = [[float(x), float(y)] for x, y in zip(vx, vy, strict=True)]
+    vswr_series.name = f"VSWR={vswr:.1f}"
+    vswr_series.marker = {"enabled": False}
+    vswr_series.line_width = 2.5
+    vswr_series.color = vswr_colors[i]
+    vswr_series.dash_style = "ShortDash"
+    vswr_series.enable_mouse_tracking = False
+    vswr_series.show_in_legend = True
+    chart.add_series(vswr_series)
+
+# Match center marker (Z = Z0)
+match_series = ScatterSeries()
+match_series.data = [[0.0, 0.0]]
+match_series.name = "Matched (Z=Z₀)"
+match_series.marker = {"enabled": True, "radius": 14, "symbol": "diamond", "fillColor": "#27AE60"}
+match_series.show_in_legend = True
+chart.add_series(match_series)
+
+# Plot impedance locus curve
+impedance_series = ScatterSeries()
+impedance_series.data = [[float(x), float(y)] for x, y in zip(gamma_x, gamma_y, strict=True)]
+impedance_series.name = "Impedance Locus (1-6 GHz)"
+impedance_series.marker = {"enabled": True, "radius": 8, "symbol": "circle"}
+impedance_series.line_width = 4
+impedance_series.color = "#E74C3C"
+impedance_series.show_in_legend = True
+chart.add_series(impedance_series)
+
+# Add frequency labels at key points
+freq_label_indices = [0, n_points // 4, n_points // 2, 3 * n_points // 4, n_points - 1]
+freq_annotations = []
+for idx in freq_label_indices:
+    freq_ghz = frequencies[idx] / 1e9
+    freq_annotations.append(
+        {
+            "point": {"x": float(gamma_x[idx]), "y": float(gamma_y[idx]), "xAxis": 0, "yAxis": 0},
+            "text": f"{freq_ghz:.1f} GHz",
+            "style": {"fontSize": "22px", "fontWeight": "bold"},
+            "backgroundColor": "rgba(255, 255, 255, 0.9)",
+            "borderWidth": 2,
+            "borderColor": "#333333",
+            "padding": 10,
+        }
+    )
+
+chart.options.annotations = [{"labels": freq_annotations, "labelOptions": {"shape": "rect"}}]
+
+# Export to PNG
+highcharts_url = "https://code.highcharts.com/highcharts.js"
+with urllib.request.urlopen(highcharts_url, timeout=30) as response:
+    highcharts_js = response.read().decode("utf-8")
+
+highcharts_more_url = "https://code.highcharts.com/highcharts-more.js"
+with urllib.request.urlopen(highcharts_more_url, timeout=30) as response:
+    highcharts_more_js = response.read().decode("utf-8")
+
+annotations_url = "https://code.highcharts.com/modules/annotations.js"
+with urllib.request.urlopen(annotations_url, timeout=30) as response:
+    annotations_js = response.read().decode("utf-8")
+
+html_str = chart.to_js_literal()
+html_content = f"""<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <script>{highcharts_js}</script>
+    <script>{highcharts_more_js}</script>
+    <script>{annotations_js}</script>
+</head>
+<body style="margin:0;">
+    <div id="container" style="width: 3600px; height: 3600px;"></div>
+    <script>{html_str}</script>
+</body>
+</html>"""
+
+with tempfile.NamedTemporaryFile(mode="w", suffix=".html", delete=False, encoding="utf-8") as f:
+    f.write(html_content)
+    temp_path = f.name
+
+chrome_options = Options()
+chrome_options.add_argument("--headless")
+chrome_options.add_argument("--no-sandbox")
+chrome_options.add_argument("--disable-dev-shm-usage")
+chrome_options.add_argument("--disable-gpu")
+chrome_options.add_argument("--window-size=3600,3600")
+
+driver = webdriver.Chrome(options=chrome_options)
+driver.get(f"file://{temp_path}")
+time.sleep(5)
+driver.save_screenshot("plot.png")
+driver.quit()
+
+Path(temp_path).unlink()
+
+# Save HTML for interactive version
+with open("plot.html", "w", encoding="utf-8") as f:
+    f.write(html_content)