mwa_jaxbeam

mwa_jaxbeam is a pure JAX implementation of the Murchison Widefield Array (MWA) Average Embedded Element (AEE) beam model.

The package reproduces the 137 MHz AEE model distributed with pyuvdata while providing a differentiable implementation suitable for optimization and inference problems. It is designed for applications such as satellite-based beam calibration, where the beam model must be evaluated millions of times and differentiated with respect to instrument parameters.

[!WARNING] This is experimental software. At present, only the 137 MHz MWA AEE beam model with zenith pointing is implemented.

Features

• Pure JAX implementation with automatic differentiation.
• Numerically validated against the MWA AEE implementation in pyuvdata.
• Fast evaluation of the full complex tile Jones matrix.
• Support for arbitrary real or complex dipole excitations.
• Efficient JIT compilation for large sky grids.

Installation

pip install mwa-jaxbeam

or

git clone https://github.com/amanchokshi/mwa_jaxbeam.git
cd mwa_jaxbeam

uv sync

or

pip install -e .

Example

import jax.numpy as jnp

from mwa_jaxbeam.aee_137mhz import jones

az_rad = jnp.deg2rad(jnp.linspace(0.0, 360.0, 361))

za_rad = jnp.deg2rad(jnp.linspace(0.0, 90.0, 91))

az_grid, za_grid = jnp.meshgrid(
    az_rad,
    za_rad,
)

beam = jones(
    az_rad=az_grid,
    za_rad=za_grid,
)

The returned Jones matrix has shape

(2, 2, *broadcast_shape)

where the first axis contains the sky-vector components (φ, θ) and the second axis contains the tile feeds (X, Y).

Validation

The implementation has been validated against the MWA AEE model distributed with pyuvdata by independently reproducing each stage of the calculation

Performance

On an Apple M4 Pro, evaluation of the full tile Jones matrix for a typical satellite beam-calibration workload (6144 sky directions) takes approximately

• 0.5 ms per forward evaluation (~2000 evaluations/s),
• 0.86 ms for a forward evaluation plus reverse-mode gradient (~1160 evaluations/s).

Performance scales approximately linearly with the number of sky directions after JIT compilation.

Status

The current implementation supports

• the 137 MHz MWA Average Embedded Element beam model,
• arbitrary complex dipole excitations,
• automatic differentiation through the complete beam calculation.

Future work includes interpolation across frequency and support for arbitrary beamformer delay settings.

Citation

If you use this package in published work, please cite the relevant MWA beam-model and pyuvdata publications, together with this repository.