feat(bokeh): implement smith-chart-basic (#3870)

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

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

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

**Parent Issue:** #3792

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/21047489015)*

---------

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/bokeh.py

@@ -0,0 +1,184 @@
+""" pyplots.ai
+smith-chart-basic: Smith Chart for RF/Impedance
+Library: bokeh 3.8.2 | Python 3.13.11
+Quality: 91/100 | Created: 2026-01-15
+"""
+
+import numpy as np
+from bokeh.io import export_png, output_file, save
+from bokeh.models import ColumnDataSource, Label
+from bokeh.plotting import figure
+
+
+# Reference impedance
+Z0 = 50  # ohms
+
+# Create figure (square for Smith chart)
+p = figure(
+    width=3600,
+    height=3600,
+    title="smith-chart-basic · bokeh · pyplots.ai",
+    x_axis_label="Real(Γ)",
+    y_axis_label="Imag(Γ)",
+    x_range=(-1.35, 1.35),
+    y_range=(-1.35, 1.35),
+    match_aspect=True,
+)
+
+# Style settings
+p.title.text_font_size = "32pt"
+p.xaxis.axis_label_text_font_size = "24pt"
+p.yaxis.axis_label_text_font_size = "24pt"
+p.xaxis.major_label_text_font_size = "18pt"
+p.yaxis.major_label_text_font_size = "18pt"
+
+# Smith chart grid colors
+GRID_COLOR = "#808080"
+GRID_ALPHA = 0.4
+BOUNDARY_COLOR = "#306998"
+
+# Draw unit circle (outer boundary - |Γ| = 1)
+theta_circle = np.linspace(0, 2 * np.pi, 500)
+unit_x = np.cos(theta_circle)
+unit_y = np.sin(theta_circle)
+p.line(unit_x, unit_y, line_width=3, line_color=BOUNDARY_COLOR, alpha=0.9)
+
+# Constant resistance circles: r = 0, 0.2, 0.5, 1, 2, 5
+r_values = [0, 0.2, 0.5, 1, 2, 5]
+for r in r_values:
+    if r == 0:
+        # r=0 is the unit circle (already drawn)
+        continue
+    # Circle center at (r/(1+r), 0) with radius 1/(1+r)
+    center = r / (1 + r)
+    radius = 1 / (1 + r)
+    theta = np.linspace(0, 2 * np.pi, 300)
+    cx = center + radius * np.cos(theta)
+    cy = radius * np.sin(theta)
+    # Only keep points inside unit circle
+    mask = cx**2 + cy**2 <= 1.001
+    cx, cy = cx[mask], cy[mask]
+    if len(cx) > 0:
+        p.line(cx, cy, line_width=1.5, line_color=GRID_COLOR, alpha=GRID_ALPHA)
+
+# Constant reactance arcs: x = ±0.2, ±0.5, ±1, ±2, ±5
+x_values = [0.2, 0.5, 1, 2, 5]
+for x in x_values:
+    # Positive reactance arc: center at (1, 1/x) with radius |1/x|
+    center_y = 1.0 / x
+    radius = 1.0 / x
+    # Generate arc points
+    theta = np.linspace(-np.pi, np.pi, 500)
+    ax = 1.0 + radius * np.cos(theta)
+    ay = center_y + radius * np.sin(theta)
+    # Keep only points inside unit circle
+    mask = (ax**2 + ay**2 <= 1.001) & (ax >= -0.001)
+    ax, ay = ax[mask], ay[mask]
+    if len(ax) > 1:
+        # Sort by angle from center for smooth arc
+        angles = np.arctan2(ay - center_y, ax - 1.0)
+        order = np.argsort(angles)
+        p.line(ax[order], ay[order], line_width=1.5, line_color=GRID_COLOR, alpha=GRID_ALPHA)
+
+    # Negative reactance arc: center at (1, -1/x)
+    center_y = -1.0 / x
+    radius = 1.0 / x
+    theta = np.linspace(-np.pi, np.pi, 500)
+    ax = 1.0 + radius * np.cos(theta)
+    ay = center_y + radius * np.sin(theta)
+    mask = (ax**2 + ay**2 <= 1.001) & (ax >= -0.001)
+    ax, ay = ax[mask], ay[mask]
+    if len(ax) > 1:
+        angles = np.arctan2(ay - center_y, ax - 1.0)
+        order = np.argsort(angles)
+        p.line(ax[order], ay[order], line_width=1.5, line_color=GRID_COLOR, alpha=GRID_ALPHA)
+
+# Draw horizontal axis (pure resistance line, x = 0)
+p.line([-1, 1], [0, 0], line_width=2, line_color="#444444", alpha=0.6)
+
+# Generate example impedance data (antenna S11 sweep from 1-6 GHz)
+np.random.seed(42)
+n_points = 50
+freq = np.linspace(1e9, 6e9, n_points)  # 1-6 GHz
+
+# Simulate realistic antenna impedance: resonance around 3.5 GHz
+f_res = 3.5e9
+Q = 5
+
+# Series RLC model: Z = R + jX
+# Resistance peaks near resonance, reactance crosses zero at resonance
+R = 45 + 10 * np.exp(-((freq - f_res) ** 2) / (0.5e9) ** 2)
+X = Z0 * Q * (freq / f_res - f_res / freq) + 5 * np.sin(2 * np.pi * freq / 2e9)
+
+# Normalize impedance and convert to reflection coefficient Γ
+z_norm = (R + 1j * X) / Z0
+gamma = (z_norm - 1) / (z_norm + 1)
+gamma_real = np.real(gamma)
+gamma_imag = np.imag(gamma)
+
+# Create data source for impedance locus
+source = ColumnDataSource(data={"gamma_real": gamma_real, "gamma_imag": gamma_imag, "freq_ghz": freq / 1e9})
+
+# Plot impedance locus curve
+p.line("gamma_real", "gamma_imag", source=source, line_width=5, line_color="#FFD43B", alpha=0.9)
+p.scatter(
+    "gamma_real",
+    "gamma_imag",
+    source=source,
+    size=14,
+    fill_color="#FFD43B",
+    line_color="#306998",
+    line_width=2,
+    alpha=0.85,
+)
+
+# Add frequency labels at key points along the locus
+label_indices = [0, n_points // 4, n_points // 2, 3 * n_points // 4, n_points - 1]
+for idx in label_indices:
+    # Offset label position to avoid overlap with data points
+    offset_y = 0.08 if gamma_imag[idx] >= 0 else -0.12
+    freq_label = Label(
+        x=gamma_real[idx],
+        y=gamma_imag[idx] + offset_y,
+        text=f"{freq[idx] / 1e9:.1f} GHz",
+        text_font_size="18pt",
+        text_color="#306998",
+        text_font_style="bold",
+    )
+    p.add_layout(freq_label)
+
+# Mark the matched condition (center point: Z = Z0, Γ = 0)
+p.scatter([0], [0], size=22, fill_color="#306998", line_color="white", line_width=3, alpha=0.95)
+center_label = Label(x=0.06, y=0.06, text="Z=Z₀", text_font_size="20pt", text_color="#306998", text_font_style="bold")
+p.add_layout(center_label)
+
+# Add resistance value labels on horizontal axis
+for r in [0.2, 0.5, 1, 2]:
+    gamma_r = r / (1 + r)
+    r_label = Label(x=gamma_r, y=-0.1, text=f"r={r}", text_font_size="16pt", text_color="#666666", text_align="center")
+    p.add_layout(r_label)
+
+# Add reactance labels at chart boundary
+for x in [0.5, 1, 2]:
+    # Calculate position on unit circle for positive x
+    # Intersection of x-arc with unit circle
+    angle = 2 * np.arctan(1 / x)
+    lx = np.cos(angle)
+    ly = np.sin(angle)
+    x_label = Label(x=lx + 0.05, y=ly + 0.02, text=f"x={x}", text_font_size="14pt", text_color="#666666")
+    p.add_layout(x_label)
+    # Negative x
+    x_label_neg = Label(x=lx + 0.05, y=-ly - 0.06, text=f"x=-{x}", text_font_size="14pt", text_color="#666666")
+    p.add_layout(x_label_neg)
+
+# Grid and background styling
+p.grid.visible = False
+p.background_fill_color = "#fafafa"
+p.border_fill_color = "#fafafa"
+
+# Save PNG
+export_png(p, filename="plot.png")
+
+# Save HTML for interactive viewing
+output_file("plot.html", title="Smith Chart - bokeh - pyplots.ai")
+save(p)