Emission¶

Emission computes the pressure field radiated by a transducer. One callable covers four modes, selected by constructor flags; __call__ always returns (pressure, coords).

from esdiva.emission import Emission

sim = Emission(tx, monochromatic=True)          # CW amplitude at fc  → (Nx, Ny, Nz)
sim = Emission(tx)                              # pulsed transient (raw SIR) → (Nt, …)
sim = Emission(tx, fs=200e6, excitation=exc)     # global excitation (L,)
sim = Emission(tx, fs=200e6, excitation=exc_LE)  # per-element excitation (L, E)

p, coords = sim(field_points, method="auto")

Algorithmic flow¶

flowchart LR
    T[Transducer<br/>delays · apodization] --> E[Emission<br/>c · rho · fs · alpha0]
    E -->|monochromatic=True| CW[CW: DFT of SIR at fc]
    E -->|excitation=None| IMP["Transient: raw SIR h(t)"]
    E -->|excitation L or L×E| EXC[Transient: SIR ⊛ excitation]
    CW --> C["__call__(field_points, method)"]
    IMP --> C
    EXC --> C
    C -->|method=auto/FST/sdi| K[SDI SIR kernel<br/>Numba-parallel CPU]
    K --> O[pressure, coords]

Modes at a glance¶

Constructor	Output shape	`coords`	Page
`monochromatic=True`	`(Nx, Ny, Nz)`	`x, y, z`	Monochromatic
default (`excitation=None`)	`(Nt, Nx, Ny, Nz)`	`+ t0, dt`	Transient Impulse
`excitation=(L,)` or `(L, E)`	`(Nt, Nx, Ny, Nz)`	`+ t0, dt`	Transient + Excitation
`alpha0=…`	as above	as above	Attenuation

Raw (N, 3) input drops the spatial axes: (N_points,) / (Nt, N_points).

Continuous-wave field¶

Fast steady-state amplitude at the centre frequency — ideal for beam patterns and focal-spot characterisation.

Monochromatic pressure — linear array (XZ)

Monochromatic pressure — matrix array 3-D

Transient field¶

Convolve the SIR with an excitation pulse for the full time-domain wavefront — diverging waves, steered plane waves, propagation snapshots.

Diverging-wave transient — linear array

Key parameters¶

Parameter	Role
`monochromatic`	CW amplitude vs transient waveform
`excitation`	`None` (raw SIR), `(L,)` global, or `(L, E)` per-element
`fs`	Time sampling for transient / attenuation
`alpha0`, `freq_power`	Power-law attenuation (see Attenuation)
`method`	`"auto"` / `"FST"` / `"sdi"` on the SIR kernel

Full signature and every parameter: API → Emission.