Broadband radiometers at 30 and 40 GHz for QUIJOTE radio astronomy experiment are very sensitive receivers to perform scientific sky observations of the Cosmic Microwave Background (CMB). The aim of this experiment is the linear polarization percentage measurement of the received signals. Radiometers have cryogenically cooled Front-End Modules followed by room temperature amplification, correlation and detection modules. Their relative bandwidth is around 30%. There are 30 receivers (pixels) at 30 GHz and 29 receivers at 40 GHz. The radiometer scheme is based on two balanced branches, microwave correlation and direct detection. The manufactured receivers measure Stokes polarization parameters I, Q, and U simultaneously. This paper describes the principle of operation of polarimeter receivers, and present details of manufactured subsystems, integration and test results. Receivers integrate different technologies: waveguides, microstrip, Monolithic Microwave Integrated Circuits (MMIC) and active and passive devices. The receivers are currently under installation in El Teide Observatory, Tenerife (Canary Islands, Spain).
This document describes the analysis, design, and prototype test results of the microwave section of a 10- to 19.5-GHz interferometer, aimed at obtaining polarization data of cosmic microwave background (CMB) radiation from the sky. First, receiver analysis is thoroughly assessed to study the contribution of each subsystem when obtaining the Stokes parameters of an input signal. Then, the receiver design is detailed starting from the front-end module, which works at cryogenic temperature, composed of a set of passive components: feedhorn, orthomode transducer, and polarizer, together with active components, such as very low-noise amplifiers. The back-end module (BEM) is directly connected, working at room temperature for further amplification, phase switching, and correlation of the signals. Moreover, the whole frequency band is split into two sub-bands (10 to 14 GHz and 16 to 20 GHz) using a high selective diplexer in the BEM in order to reject radiofrequency interferences. Phase switches allow phase difference steps of 5.625 deg, which modulate the correlated outputs to reduce systematic effects in the postdetection signal processing. Finally, measurements of all the subsystems comprising the microwave section of the receiver as well as the characterization of the complete microwave receiver are presented. The obtained results demonstrate successful performance of the microwave receiver that, together with an electro-optical correlator and a near-infrared camera, comprises the interferometer. Moreover, synthesized images corresponding to combinations of the Stokes parameters can be obtained with the whole system.
The QUIJOTE Experiment (Q-U-I JOint TEnerife) is a combined operation of two telescopes and three instruments working in the microwave band to measure the polarization of the Cosmic Microwave Background (CMB) from the northern hemisphere, at medium and large angular scales. The experiment is located at the Teide Observatory in Tenerife, one of the seven Canary Islands (Spain). The project is a consortium maintained by several institutions: the Instituto de Astrofísica de Canarias (IAC), the Instituto de Física de Cantabria (IFCA), the Communications Engineering Department (DICOM) at Universidad de Cantabria, and the Universities of Manchester and Cambridge. The consortium is led by the IAC.
The QUIJOTE TGI instrument is currently being assembled and tested at the IAC in Spain. The TGI is a 31 pixel 26-36 GHz polarimeter array designed to be mounted at the focus of the second QUIJOTE telescope. This follows a first telescope and multi-frequency instrument that have now been observing almost 2 years. The polarimeter design is based on the QUIET polarimeter scheme but with the addition of an extra 90º phase switch which allows for quasiinstantaneous complete QUI measurements through each detector. The advantage of this solution is a reduction in the systematics associated with differencing two independent radiometer channels. The polarimeters are split into a cold front end and a warm back end. The back end is a highly integrated design by the engineers at DICOM. It is also sufficiently modular for testing purposes. In this presentation the high quality wide band components used in the optical design (also designed in DICOM) are presented as well as the novel cryogenic modular design. Each polarimeter chain is accessible individually and can be removed from the cryostat and replaced without having to move the remaining pixels. The optical components work over the complete Ka band showing excellent performance. Results from the sub unit measurements are presented and also a description of the novel calibration technique that allows for bandpass measurement and polar alignment. Terrestrial Calibration for this instrument is very important and will be carried out at three points in the commissioning phase: in the laboratory, at the telescope site and finally a reduced set of calibrations will be carried out on the telescope before measurements of extraterrestrial sources begin. The telescope pointing model is known to be more precise than the expected calibration precision so no further significant error will be added through the telescope optics. The integrated back-end components are presented showing the overall arrangement for mounting on the cryostat. Many of the microwave circuits are in-house designs with performances that go beyond commercially available products.
The QUIJOTE-CMB experiment (Q-U-I JOint TEnerife CMB experiment) is an ambitious project to obtain polarization measurements of the sky microwave emission in the 10 to 47 GHz range. With this aim, a pair of 2,5μm telescopes and three instruments are being sited at the Teide Observatory, in Tenerife (Canary Islands, Spain). The first telescope and the first instrument (the MFI: Multi Frequency Instrument) are both already operating in the band from 10 to 20 GHz, since November 2012. The second telescope and the second instrument (TGI: Thirty GHz instrument) is planned to be in
commissioning by the end of summer 2014, covering the range of 26 to 36 GHz. After that, a third instrument named FGI (Forty GHz instrument) will be designed and manufactured to complete the sky survey in the frequency range from 37 to 47 GHz. In this paper we present an overview of the whole project current status, from the technical point of view.
The QUIJOTE-CMB project has been described in previous publications. Here we present the current status of the
QUIJOTE multi-frequency instrument (MFI) with five separate polarimeters (providing 5 independent sky pixels): two
which operate at 10-14 GHz, two which operate at 16-20 GHz, and a central polarimeter at 30 GHz. The optical
arrangement includes 5 conical corrugated feedhorns staring into a dual reflector crossed-draconian system, which
provides optimal cross-polarization properties (designed to be < −35 dB) and symmetric beams. Each horn feeds a novel
cryogenic on-axis rotating polar modulator which can rotate at a speed of up to 1 Hz. The science driver for this first
instrument is the characterization of the galactic emission. The polarimeters use the polar modulator to derive linear
polar parameters Q, U and I and switch out various systematics. The detection system provides optimum sensitivity
through 2 correlated and 2 total power channels. The system is calibrated using bright polarized celestial sources and
through a secondary calibration source and antenna. The acquisition system, telescope control and housekeeping are all
linked through a real-time gigabit Ethernet network. All communication, power and helium gas are passed through a
central rotary joint. The time stamp is synchronized to a GPS time signal. The acquisition software is based on PLCs
written in Beckhoffs TwinCat and ethercat. The user interface is written in LABVIEW. The status of the QUIJOTE MFI
will be presented including pre-commissioning results and laboratory testing.
The QUIJOTE (Q-U-I JOint Tenerife) CMB Experiment will operate at the Teide Observatory with the aim
of characterizing the polarisation of the CMB and other processes of Galactic and extragalactic emission in the
frequency range of 10-40GHz and at large and medium angular scales. The first of the two QUIJOTE telescopes
and the first multi-frequency (10-30GHz) instrument are already built and have been tested in the laboratory.
QUIJOTE-CMB will be a valuable complement at low frequencies for the Planck mission, and will have the
required sensitivity to detect a primordial gravitational-wave component if the tensor-to-scalar ratio is larger
than r = 0.05.