Radiation & Scattering

Radiation & Scattering#

`tidy3d.rf.DirectivityMonitor`	`Monitor` that records the radiation characteristics of antennas in the frequency domain at specified observation angles.
`tidy3d.rf.DirectivityMonitorSpec`	Specification for automatically generating a `DirectivityMonitor`.
`tidy3d.rf.RectangularAntennaArrayCalculator`	This class provides methods to calculate the array factor and far-field radiation patterns for rectangular phased antenna arrays.
`tidy3d.rf.LobeMeasurer`	Tool for detecting and analyzing lobes in antenna radiation patterns, along with their characteristics such as direction and beamwidth.

When modeling antennas or scattering problems, it is vital to analyze the radiated far-field. For such applications, the DirectivityMonitor should be used.

# Define angular coordinates
# Theta is the elevation angle relative to global +z axis
# Phi is the azimuthal angle relative to global +x axis
my_theta = np.linspace(0, np.pi, 91)
my_phi = np.linspace(0, 2*np.pi, 181)

# Define directivity monitor
my_directivity_monitor = DirectivityMonitor(
    center=(0,0,0),
    size=(100, 100, 100),
    freqs=my_frequencies,
    phi=my_phi,
    theta=my_theta,
    name='My radiation monitor',
)

The DirectivityMonitor should completely surround the structure of interest.

Alternatively, a DirectivityMonitorSpec can be used to create a specification for automatic generation of a DirectivityMonitor in the TerminalComponentModeler.

# Define directivity monitor spec
my_directivity_monitor_spec = DirectivityMonitorSpec()

Once the monitor or monitor spec is defined, it should be added to the radiation_monitors option of the TerminalComponentModeler.

# Add directivity monitor to simulation
my_tcm = TerminalComponentModeler(
    ...,
    radiation_monitors=[my_directivity_monitor, my_directivity_monitor_spec],
)

Once the simulation is completed, the get_antenna_metrics_data() method of the TerminalComponentModelerData object is used to obtain the radiation metrics.

# Get radiation metrics
my_antenna_metrics = my_tcm_data.get_antenna_metrics_data()

# Get individual metrics
my_directivity = my_antenna_metrics.directivity
my_gain = my_antenna_metrics.gain
my_radiation_efficiency = my_antenna_metrics.radiation_efficiency
my_reflection_efficiency = my_antenna_metrics.reflection_efficiency
my_realized_gain = my_antenna_metrics.realized_gain
my_supplied_power = my_antenna_metrics.supplied_power
my_radiated_power = my_antenna_metrics.radiated_power
my_radiation_intensity = my_antenna_metrics.radiation_intensity
my_axial_ratio = my_antenna_metrics.axial_ratio
my_left_pol = my_antenna_metrics.left_polarization
my_right_pol = my_antenna_metrics.right_polarization

Each metric is in the form of an xarray.DataArray object that can be used for plotting, export, and further analysis. For examples of how these datasets can be manipulated, please refer to the notebooks in the “See also” section below.

The LobeMeasurer utility class can be used to analyze radiation pattern lobes.

# Define lobe measurer
my_lobes = LobeMeasurer(
    angle=phi,   # Angular axis of interest
    radiation_pattern=my_gain,   # Radiation pattern to measure
)

# Get lobe characteristics
my_lobe_measures = my_lobes.lobe_measures
my_main_lobe = my_lobes.main_lobe
my_side_lobes = my_lobes.side_lobe

Lobe characteristics such as direction, magnitude, and -3 dB beamwidth can be obtained for the main and side lobes. Additionally, the LobeMeasurer.plot() utility function adds main lobe beam direction and width markers to polar radiation plots.