Time Domain Models

The Time Domain models consider propagation of broadband signals in the time domain, allowing for one model to be run and then evaluated at a range of frequncies. This approach allows for time domain channel models to be created, or numerous frequency domain antenna patterns to be produced by sampling the time domain response at different frequencies using fourier transforms. At present only the general scattering case is implemented, but farfield patterns can still be calculated this way by defining a spherical shell of sinks.

As a mesh approach is used to generate the source coordinates, the mesh resolution for these points should be defined based upon the highest frequency of interest.

lyceanem.models.time_domain.calculate_scattering(aperture_coords, sink_coords, excitation_function, antenna_solid, desired_E_axis, scatter_points=None, wavelength=1.0, scattering=0, elements=False, sampling_freq=1000000000.0, los=False, num_samples=10000, mesh_resolution=0.5, antenna_axes=array([[1., 0., 0.], [0., 1., 0.], [0., 0., 1.]]), project_vectors=True)[source]

Based upon the parameters given, calculate the time domain scattering for the apertures and sinks. The defaults for sampling time are based upon a sampling rate of 1GHz, and a sample time of 1ms.

Parameters:

  • aperture_coords (open3d.geometry.TriangleMesh) – source coordinates

  • sink_coords (open3d.geometry.TriangleMesh) – sink coordinates

  • antenna_solid (lyceanem.base_classes.structures) – the class should contain all the environment for scattering, providing the blocking for the rays

  • desired_E_axis (1D numpy array of floats) – the desired excitation vector, can be a 1*3 array or a n*3 array if multiple different exciations are desired in one lauch

  • scatter_points (open3d.geometry.TriangleMesh) – the scattering points in the environment. Defaults to [None], in which case scattering points will be generated from the antenna_solid. If no scattering should be considered then set scattering to [0].

  • wavelength (float) – the wavelength of interest in metres

  • scattering (int) – the number of reflections to be considered, defaults to [0], but up to 2 can be considered. The higher this number to greater to computational effort, and for most situations 1 should be ample.

  • elements (boolean) – whether the sources and sinks should be considered as elements of a phased array, or a fixed phase aperture like a horn or reflector

  • sampling_freq (float) – the desired sampling frequency, should be twice the highest frequency of interest to avoid undersampling artifacts

  • num_samples (int) – the length of the desired sampling, can be calculated from the desired model time

  • mesh_resolution (float) – the desired mesh resolution in terms of wavelengths if scattering points are not provided. A scattering mesh is generated on the surfaces of all provided trianglemesh structures.

Returns:

  • Ex (numpy array of float) – the x directed voltage at the sink coordinates in the time domain, if elements=True, then it will be an array of num_sinks * num_samples, otherwise it will be a 1D array

  • Ey (numpy array of float) – the y directed voltage at the sink coordinates in the time domain, if elements=True, then it will be an array of num_sinks * num_samples, otherwise it will be a 1D array

  • Ez (numpy array of float) – the z directed voltage at the sink coordinates in the time domain, if elements=True, then it will be an array of num_sinks * num_samples, otherwise it will be a 1D array

  • Waketimes (numpy array of float) – the shortest time required for a ray to reach any sink from any source, as long as elements=False. If elements=True, then this is not implemented in the same way, and will return the shortest time required for the final source.