Colloquium Abstract - Elder - 2025Sep19

September 19, 2025

11:00am Mountain

Katherine Elder (NRAO)

 

Investigating and modeling mutual coupling in radio interferometers

 

Abstract

Measurement of the power spectrum of high redshift 21 cm emission from neutral hydrogen probes the `formation of the first luminous objects and the ionization of intergalactic medium by the first stars. However, the 21 cm signal at these redshifts is orders of magnitude fainter than astrophysical foregrounds, making it challenging to measure. Power spectrum techniques may be able to avoid these foregrounds by extracting foreground-free Fourier modes, but this is exacerbated by instrumental systematics that can add spectral structure to the data, leaking foreground power to the foreground-free Fourier modes. It is therefore imperative that any instrumental systematic effects are properly understood and mitigated. A known concern for densely packed radio interferometers is mutual coupling, which causes excess coupling with neighboring antennas. To study this phenomenon, a numerical electromagnetic software simulation of the Murchison Widefield Array (MWA) has been built in FEKO to estimate the amplitude of mutual coupling for multiple antennas in the MWA. These numerical models are compared to a coupling coefficient predicted by an analytic re-radiation model to validate the analytic model. The numerical model of the MWA predicts an amplitude which exceeds the 21 cm requirement to avoid spreading the foreground, while the analytic model predicts a lower amplitude. Future and ongoing work is to build numerical models for other radio interferometers to further validate the analytic model for use in visibility models and calibration schemes..


Local Host: Paul Demorest

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