From 023c20016f56e1f74291aaf1b0eda2ff8ac73b26 Mon Sep 17 00:00:00 2001
From: Brendan Haines <brendan.haines@gmail.com>
Date: Sun, 23 Mar 2025 01:44:12 -0600
Subject: [PATCH] I'm steering to the wrong place but have a somewhat working
 steering animation

---
 plots/09_beamforming.py | 96 +++++++++++++++++++++++++++++++++++------
 plots/utils.py          | 25 +++++++++++
 2 files changed, 109 insertions(+), 12 deletions(-)

diff --git a/plots/09_beamforming.py b/plots/09_beamforming.py
index a1ec528..c0f8c7d 100644
--- a/plots/09_beamforming.py
+++ b/plots/09_beamforming.py
@@ -1,6 +1,6 @@
 # %% imports
 import numpy as np
-from utils import AnimatedPlot, dir_assets
+from utils import AnimatedPlot, db10, db20, dir_assets, wrap_phase
 
 
 # %%
@@ -17,7 +17,6 @@ class PcolorPlot(AnimatedPlot):
         self.element_x = np.linspace(-x_range / 2, x_range / 2, elements)
         self.element_y = np.zeros(elements)
         self.angle = np.deg2rad(angle_deg)
-        self.element_phase = np.zeros(elements)
         self.element_phase = (
             np.dot(np.array([self.element_x, self.element_y]).T, [np.sin(self.angle), np.cos(self.angle)]) * 2 * np.pi
         )
@@ -104,18 +103,91 @@ class PcolorMagPlot(PcolorPlot):
         )
 
 
+class Steer(AnimatedPlot):
+    def __init__(self, elements: int, spacing_lambda: float = 0.5, **kwargs):
+        super().__init__(**kwargs)
+
+        self.ax.remove()
+        self.axs = [
+            self.fig.add_subplot(3, 1, 1),
+            self.fig.add_subplot(3, 1, 2),
+            self.fig.add_subplot(3, 1, 3),
+        ]
+
+        self.spacing_lambda = spacing_lambda
+        self.elements = elements
+
+    def update(self, t: float):
+        for ax in self.axs:
+            ax.clear()
+
+        # rewind, don't reset
+        if t > 0.5:
+            t = 1 - t
+        t *= 2
+
+        angle = np.deg2rad((t * 2 - 1) * 90)  # steering angle
+
+        def get_phase(position):
+            return wrap_phase(np.sin(angle) * position * 2 * np.pi, deg=False)
+
+        ideal_position = self.spacing_lambda * np.linspace(-(self.elements - 1) / 2, (self.elements - 1) / 2, 1001)
+        ideal_phase = get_phase(ideal_position)
+
+        element_position = self.spacing_lambda * np.linspace(
+            -(self.elements - 1) / 2, (self.elements - 1) / 2, self.elements
+        )
+        element_phase = get_phase(element_position)
+        element_taper = np.ones(self.elements)
+        element_excitation = element_taper * np.exp(1j * element_phase)
+
+        theta = np.linspace(-90, 90, 361)
+        fft_points = 128
+        fft_period = 90 / self.spacing_lambda
+        theta_fft = np.linspace(0, fft_period, fft_points, endpoint=False)
+        ff_pattern = np.interp(
+            theta,
+            theta_fft,
+            np.fft.fft(np.concat([element_excitation, np.zeros(fft_points - self.elements)]), norm="backward")
+            / self.elements,
+            period=fft_period,
+        )
+
+        self.fig.suptitle(f"{np.rad2deg(angle):+5.1f}° Steer")
+
+        rolloff = np.cos(np.deg2rad(theta))
+        self.axs[0].set_ylabel("Farfield Magnitude [dB]")
+        self.axs[0].plot(theta, db20(rolloff), color="gray")
+        self.axs[0].plot(theta, db20(ff_pattern * rolloff))
+        self.axs[0].set_xlim(-90, 90)
+        self.axs[0].set_ylim(-30, 5)
+        self.axs[0].set_xlabel("Theta [°]")
+        self.axs[0].grid(True)
+        self.axs[0].axvline(np.rad2deg(angle))
+
+        self.axs[1].set_ylabel("Excitation Phase")
+        self.axs[1].stem(element_position, np.rad2deg(element_phase))
+        self.axs[1].plot(ideal_position, np.rad2deg(ideal_phase), linestyle="--")
+        self.axs[1].set_ylim(-200, 200)
+
+        self.axs[2].set_ylabel("Excitation Magnitude")
+        self.axs[2].stem(element_position, element_taper)
+        # self.axs[2].set_xlabel("Element")
+
+
 # %%
 def generate():
-    for elements in [
-        1,
-        2,
-        4,
-        10,
-    ]:
-        PcolorPhasePlot(elements=elements, angle_deg=45).save(dir_assets / "beamforming" / f"phase_xz_{elements}el.gif")
-        PcolorMagPlot(elements=elements, angle_deg=45).save(
-            dir_assets / "beamforming" / f"magnitude_xz_{elements}el.gif"
-        )
+    # for elements in [
+    #     1,
+    #     2,
+    #     4,
+    #     10,
+    # ]:
+    #     PcolorPhasePlot(elements=elements, angle_deg=45).save(dir_assets / "beamforming" / f"phase_xz_{elements}el.gif")
+    #     PcolorMagPlot(elements=elements, angle_deg=45).save(
+    #         dir_assets / "beamforming" / f"magnitude_xz_{elements}el.gif"
+    #     )
+    Steer(elements=16, spacing_lambda=0.5, frames=200).save(dir_assets / "beamforming" / "steering.gif", framerate=15)
 
 
 # %%
diff --git a/plots/utils.py b/plots/utils.py
index 5677ca0..95a3ba3 100644
--- a/plots/utils.py
+++ b/plots/utils.py
@@ -67,3 +67,28 @@ class AnimatedPlot(ABC):
             [0, 1]
         """
         pass
+
+
+def db20(v):
+    return 20 * np.log10(np.abs(v))
+
+
+def db10(v):
+    return 10 * np.log10(np.abs(v))
+
+
+def db2v(db):
+    return 10 ** (db / 20)
+
+
+def db2w(db):
+    return 10 ** (db / 10)
+
+
+def wrap_phase(phase, deg: bool):
+    if deg:
+        maxval = 180
+    else:
+        maxval = np.pi
+
+    return (phase + maxval) % (2 * maxval) - maxval