fix e and h cartesian calculations

Author: scottprahl

CHANGELOG.rst

@@ -1,6 +1,11 @@
 Changelog
 =========
 
+3.2.0 (03/06/2026)
+-------------------
+*   fix error in E & H calculations in the near field when y≠0 (thanks @dorianherle)
+*   add regression test
+
 3.1.0 (02/07/2026)
 -------------------
 *   add near-field E and H field APIs, fix boundary continuity/medium handling, and expand validation tests

miepython/__init__.py

@@ -147,7 +147,7 @@ def _missing(*_args, **_kwargs):
     "_D_downwards",
 )
 
-__version__ = "3.1.0"
+__version__ = "3.2.0"
 __author__ = "Scott Prahl"
 __email__ = "scott.prahl@oit.edu"
 __copyright__ = "2017-2026, Scott Prahl"

miepython/field.py

@@ -403,7 +403,7 @@ def _e_near_abcd(abcd, lambda0, d_sphere, m_sphere, n_env, r, theta, phi, includ
             E_the += Ei_the
             E_phi += Ei_phi
 
-    return np.array([E_rad, E_the, -E_phi])
+    return np.array([E_rad, E_the, E_phi])
 
 
 def _h_near_abcd(abcd, lambda0, d_sphere, m_sphere, n_env, r, theta, phi, include_incident):
@@ -460,7 +460,7 @@ def _h_near_abcd(abcd, lambda0, d_sphere, m_sphere, n_env, r, theta, phi, includ
             H_the += Hi_the
             H_phi += Hi_phi
 
-    return np.array([H_rad, H_the, -H_phi])
+    return np.array([H_rad, H_the, H_phi])
 
 
 def _eh_near_abcd(abcd, lambda0, d_sphere, m_sphere, n_env, r, theta, phi, include_incident):
@@ -520,7 +520,7 @@ def _eh_near_abcd(abcd, lambda0, d_sphere, m_sphere, n_env, r, theta, phi, inclu
             h_the += h_i[1]
             h_phi += h_i[2]
 
-    return np.array([e_rad, e_the, -e_phi]), np.array([h_rad, h_the, -h_phi])
+    return np.array([e_rad, e_the, e_phi]), np.array([h_rad, h_the, h_phi])
 
 
 def e_near(lambda0, d_sphere, m_sphere, n_env, r, theta, phi, include_incident=True, n_pole=0, abcd=None):

tests/test_field.py

@@ -291,3 +291,70 @@ def test_cartesian_wrappers_match_spherical_transform(m_sphere, n_env):
     np.testing.assert_allclose(h_xyz, h_ref, rtol=1e-12, atol=1e-12)
     np.testing.assert_allclose(e_xyz2, e_ref, rtol=1e-12, atol=1e-12)
     np.testing.assert_allclose(h_xyz2, h_ref, rtol=1e-12, atol=1e-12)
+
+
+def test_no_contrast_cartesian_fields_match_incident_plane_wave():
+    """No-contrast sphere should reduce to the incident plane wave everywhere."""
+    lambda0 = 1.0
+    n_env = 1.0
+    d_sphere = 0.002
+    m_sphere = 1.0 + 0.0j
+
+    x = np.array([3.0, 0.0, 0.0, 2.0, 2.0])
+    y = np.array([0.0, 0.0, 3.0, 2.0, 2.0])
+    z = np.array([0.0, 3.0, 0.0, 0.0, 0.5])
+
+    k = 2 * np.pi * n_env / lambda0
+    phase = np.exp(1j * k * z)
+    zeros = np.zeros_like(phase)
+    e_expected = np.array([phase, zeros, zeros])
+    h_expected = np.array([zeros, phase, zeros])
+
+    e_xyz = e_near_cartesian(lambda0, d_sphere, m_sphere, n_env, x, y, z, include_incident=True)
+    h_xyz = h_near_cartesian(lambda0, d_sphere, m_sphere, n_env, x, y, z, include_incident=True)
+    e_xyz2, h_xyz2 = eh_near_cartesian(lambda0, d_sphere, m_sphere, n_env, x, y, z, include_incident=True)
+
+    np.testing.assert_allclose(e_xyz, e_expected, rtol=1e-12, atol=1e-12)
+    np.testing.assert_allclose(h_xyz, h_expected, rtol=1e-12, atol=1e-12)
+    np.testing.assert_allclose(e_xyz2, e_expected, rtol=1e-12, atol=1e-12)
+    np.testing.assert_allclose(h_xyz2, h_expected, rtol=1e-12, atol=1e-12)
+
+
+def test_no_contrast_spherical_fields_match_incident_components():
+    """No-contrast spherical fields should follow standard spherical components."""
+    lambda0 = 1.0
+    n_env = 1.0
+    d_sphere = 0.002
+    m_sphere = 1.0 + 0.0j
+    x, y, z = 2.0, 2.0, 0.5
+
+    r = np.sqrt(x**2 + y**2 + z**2)
+    theta = np.arccos(z / r)
+    phi = np.arctan2(y, x)
+
+    k = 2 * np.pi * n_env / lambda0
+    phase = np.exp(1j * k * z)
+
+    e_expected = np.array(
+        [
+            phase * np.sin(theta) * np.cos(phi),
+            phase * np.cos(theta) * np.cos(phi),
+            -phase * np.sin(phi),
+        ]
+    )
+    h_expected = np.array(
+        [
+            phase * np.sin(theta) * np.sin(phi),
+            phase * np.cos(theta) * np.sin(phi),
+            phase * np.cos(phi),
+        ]
+    )
+
+    e_sph = e_near(lambda0, d_sphere, m_sphere, n_env, r, theta, phi, include_incident=True)
+    h_sph = h_near(lambda0, d_sphere, m_sphere, n_env, r, theta, phi, include_incident=True)
+    e_sph2, h_sph2 = eh_near(lambda0, d_sphere, m_sphere, n_env, r, theta, phi, include_incident=True)
+
+    np.testing.assert_allclose(e_sph, e_expected, rtol=1e-12, atol=1e-12)
+    np.testing.assert_allclose(h_sph, h_expected, rtol=1e-12, atol=1e-12)
+    np.testing.assert_allclose(e_sph2, e_expected, rtol=1e-12, atol=1e-12)
+    np.testing.assert_allclose(h_sph2, h_expected, rtol=1e-12, atol=1e-12)