Measurement of the Primary Beam of the Tianlai Cylindrical Antenna Using an Unmanned Aerial Vehicle

TL;DR

This paper introduces a UAV-based method to measure the primary beam profiles of the Tianlai cylindrical antenna array in both N-S and E-W directions, providing a novel approach for large-scale antenna calibration.

Contribution

The study presents a new UAV-based technique for measuring the beam profiles of large cylindrical antennas, overcoming limitations of traditional ground-based methods.

Findings

UAV method accurately measures beam profiles in 700-800 MHz range.

Results agree with astronomical source transits and simulations.

Method improves calibration accuracy for large-scale radio telescopes.

Abstract

The Tianlai Cylinder Pathfinder Array consists of three adjacent cylindrical reflectors fixed on the ground, each 40 meters long and 15 meters wide, with the cylinder axis oriented along the North-South (N-S)direction. Dual linear polarisation feeds are distributed along the focus line, parallel to the cylinder axis. Measurement of the primary beam profile of these cylindrical reflectors is difficult, as they are too large to be placed in an anechoic chamber. While the beam profile along the East-West (E-W) direction can be measured with the transit observations of bright astronomical radio sources, the beam profile along the N-S direction remains very uncertain. We present a preliminary measurement of the beam profile of the Tianlai cylindrical antenna along both the N-S direction and E-W direction in the frequency range of 700-800 MHz, using a calibrator source carried by an unmanned aerial vehicle (UAV) flying in the far field. The beam profile of the Tianlai cylindrical antenna is determined from the analysis of the auto-correlation signals from the the cylinder array correlator, taking into account the emitter antenna beam profile, itself measured with a dipole antenna on the ground. The accuracy of the UAV-based determination of the cylinder beam profiles is validated by comparing the results with the one derived from bright astronomical source transits, and with simulated beams.