Multi-pixel Ka-band radiometer for the QUIJOTE experiment (Phase II)

Abstract

This paper presents the configuration of the Ka-band radiometer developed for the Phase II of the QUIJOTE radio astronomy experiment, as well as the design of the different subsystems involved in the instrument. The new configuration, consisting of around 30 modified receivers working in the 26-36 GHz band, avoids the need of a rotating polar modulator at cryogenic temperatures, which is a source of mechanical and thermal difficulties. Moreover, the larger number of receivers will increase the instrument sensitivity. These two aspects are a clear advantage over the receiver developed for the experiment Phase I. The present paper also gives detailed information of some designed subsystems such as the feedhorn, the polarizer, the orthomode transducer, the cryogenic low-noise amplifiers and the back-end module.

Polarimetric receiver in the forty gigahertz band: new instrument for the Q-U-I joint Tenerife experiment

“…The feed subsystems are waveguide components, such as the feedhorn antenna, the polarizer and the OMT, which are tested at room temperature, since only a reduction on their losses are expected when they operate under cryogenic conditions. The feedhorn antenna is based on a corrugated design (Cano et al 2011) using a circular waveguide input. The cross-polarization of the antenna is a significant issue, and it is defined by the throat of the antenna.…”

The thirty gigahertz instrument receiver for the Q-U-I Joint Tenerife experiment: Concept and experimental results

“…Therefore, the previous analysis is focused on a linear polarization as input signal to the polarimeter. The translation from linear polarization signal to circular polarized wave is performed with the square quad-ridge waveguide polarizer 13 combined with the OMT, 13 which splits left-hand and right-hand circular components. The reference plane of the polarizer is rotated 45 • regarding the reference system of the input signal and the OMT in order to accomplish the behavior of a septum polarizer.…”

The Thirty Gigahertz Instrument Receiver for the QUIJOTE Experiment: Preliminary Polarization Measurements and Systematic-Error Analysis

“…Two other instruments are under development: the Thirty-GHz Instrument (TGI), and the Forty-GHz Instrument (FGI), working in the 26–36 GHz and 35–47 GHz frequency bands respectively [15]. These experiments will undertake two surveys: a wide survey covering 20,000 deg 2 reaching a sensitivity of ~15 µK/beam with the MFI, and a deeper survey of 3000 deg 2 with a sensitivity of ~4 µK/beam with the MFI and better than 1 µK/beam with the TGI and the FGI.…”

“…The parameter V is assumed to be zero since the CMB is considered not to be circularly polarized [16] and is not measured. Therefore, assuming the incoming signal at the receiver to be linearly polarized , a translation to a circularly polarized wave is performed with the square quad-ridge waveguide polarizer [15] combined with the OMT, which splits the left- and right-hand circular components to accomplish the behavior of a septum polarizer [17] with the benefit of avoiding its usual bandwidth limitation.…”