Experimental evaluation of polarimetric beamformers for an L-band phased array feed

Abstract

A novel method to form multiple high-sensitivity beams with a reflector based radio telescope is to use a phased array feed (PAF). To accurately reconstruct the polarization state of the incident radio waves, the beam patterns of the PAF are of crucial importance. The co-and cross-polar element patterns of an oversampled L-band PAF prototype system have been measured in an interferometric setup. It is demonstrated that, although the antenna elements sampling the two orthogonal polarizations of the focal field are not co-located, dual polarized beams can be formed by combining the element responses in a beamformer. The capability of the PAF to optimize its beams in terms of sensitivity, sidelobes and polarization characteristics is demonstrated.

Improving the Calibration Efficiency of an Array Fed Reflector Antenna Through Constrained Beamforming

“…Here all elements in the array (both polarizations) are employed to produce patterns on the sky for each nominal polarization (as opposed to a bi-scalar beamfomer wherein only elements of one polarization are used, cf. [24]). Results presented here are for only one nominal polarization, as the results for either polarization are very similar.…”

Optimization of Electric Ethylene Production: Exploring the Role of Cracker Flexibility, Batteries, and Renewable Energy Integration

“…In addition to the electricity price, we use the time-dependent CO 2 intensity of the grid for the emission minimization case study. The average CO 2 intensity of the Dutch electricity grid in 2019 was 0.369 kg CO 2 /kWh, with projections of a decrease to 0.208 and 0.094 kg CO 2 /kWh in 2025 and 2030, respectively . The hourly CO 2 intensity profile was derived based on the hourly production of natural gas, coal, nuclear, solar, and wind in 2019 and incorporating the corresponding CO 2 emission factors from van Cappellen et al The resulting CO 2 profile has an average value of 0.372 kg CO 2 /kWh, which aligns well with the value reported in van Cappellen et al To estimate the average CO 2 intensity of 2030, we increased renewable electricity generation, set coal-fired electricity generation to zero, and decreased gas-fired electricity generation at times of high renewable availability.…”

“…The average CO 2 intensity of the Dutch electricity grid in 2019 was 0.369 kg CO 2 /kWh, with projections of a decrease to 0.208 and 0.094 kg CO 2 /kWh in 2025 and 2030, respectively . The hourly CO 2 intensity profile was derived based on the hourly production of natural gas, coal, nuclear, solar, and wind in 2019 and incorporating the corresponding CO 2 emission factors from van Cappellen et al The resulting CO 2 profile has an average value of 0.372 kg CO 2 /kWh, which aligns well with the value reported in van Cappellen et al To estimate the average CO 2 intensity of 2030, we increased renewable electricity generation, set coal-fired electricity generation to zero, and decreased gas-fired electricity generation at times of high renewable availability. This results in a CO 2 intensity profile with an average value of 0.091 kg CO 2 /kWh and a renewable electricity share of 76.3%, which is consistent with the projection of van Cappellen et al The summary of the emission factors, the total annual generation for the 2019 and 2030 profiles, and a more elaborate explanation on the method used to obtain the profiles can be found in the Supporting Information and in Table S1.…”

Polarimetric calibration results of an APERTIF phased array feed

“…The PAF system consists of 121 Vivaldi elements in a dense rectangular grid [5]. The elements are mechanically oriented in two orthogonal directions, 61 and 60 in the X-and Y-direction respectively, to sample the incoming radio waves in two polarizations.…”

“…These measurements show that the central compound beam produced by a bi-scalar beamforming scheme has a peak cross-pol level below -20 dB. In the bi-scalar beamforming scheme, the receptors associated with each polarization are beamformed separately assuming that their polarimetric responses are perfectly orthogonal [5]. This cross-pol performance should allow to do proper polarimetric observations, which we demonstrate by measuring the Faraday rotation along the line-of-sight towards the astronomical source BL Lac over the frequency range from 1190 to 1390 MHz.…”