Demostrador interferométrico para la medida de la polarización a 90 GHz

This document describes a baseband digital correlator implemented using two commercial synchronized FPGAs. The correlator is part of a broadband radioastronomy radiometer demonstrator aimed to obtain polarization data of Cosmic Microwave Background (CMB) radiation from the sky in the W band. Using correlation techniques, it is possible to obtain the Stokes parameters (I, Q, U) of the CMB correcting the phase differences produced by the different subsystems between the receivers’ branches on real time. Ought to the input frequency limitation of the digitizers, it is necessary to down convert all the signals from IF to baseband using commercial mixers and filters. Other digital implementations could be applied to large antenna arrays like the Square Kilometre Array (SKA) using specific electronics or supercomputing networks designed to work with lots of real time data

Análisis de errores sistemáticos en un polarímetro a 90 GHz para aplicaciones de radioastronomía

This paper describes a systematic error analysis applied to a 90 GHz receiver designed to measure the polarization of the Cosmic Microwave Background (CMB) radiation. Although the reported polarimeter allows the measurement of the Stokes parameters (I, Q, U) of the CMB, a previous systematic errors analysis is required in order to correct them when using the instrument to measure the radiation coming from the sky. In this work two sources of systematic errors, as the amplitude and phase imbalance between the two main branches of the polarimeter, are taken into account. These branches are assumed to have the same gain and phase, so the imbalance effects will be studied over the polarimeter’s detected signal and the corresponding polarization measurement

Electro-optic correlator for large-format microwave interferometry: Up-conversionand correlation stages performance analysis

In this paper, a microwave interferometer prototype with a near-infra-red optical correlator is proposed as a solution to get a large-format interferometer with hundreds of receivers for radio astronomy applications. A 10 Gbits/s Lithium Niobate modulator has been tested as part of an electro-optic correlator up-conversion stage that will be integrated in the interferometer prototype. Its internal circuitry consists of a single-drive modulator biased by a SubMiniature version A (SMA) connector allowing to up-convert microwave signals with bandwidths up to 12.5 GHz to the near infrared band. In order to characterize it, a 12 GHz tone and a bias voltage were applied to the SMA input using a polarization tee. Two different experimental techniques to stabilize the modulator operation point in its minimum optical carrier output power are described. The best achieved results showed a rather stable spectrum in amplitude and wavelength at the output of the modulator with an optical carrier level 23 dB lower than the signal of interest. On the other hand, preliminary measurements were made to analyze the correlation stage, using 4f and 6f optical configurations to characterize both the antenna/fiber array configuration and the corresponding point spread function.This work was supported by the Ministerio de Economía y Competitividad, Spain, under the Plan Nacional de I+D+i project with Reference No. ESP2015-70646-C2-1-R cofinanced with EU FEDER funds and the CONSOLIDER INGENIO 2010 programme under the Reference No. CSD2010-00064. The authors would like to thank Félix Gracia from Instituto Astrofísico de Canarias (IAC) for his assistance and help

Correladores en banda base para un interferómetro de gran formato a 30 GHz

The aim of the reported work is to explore the viability of a correlator for a future large-scale interferometer, with hundreds of receivers, by developing a pathfinder in which the 30 GHz receivers of QUIJOTE experiment will be reused. Nowadays, there are some interferometric experiments designed to study the Cosmic Microwave Background (CMB). Although the sensitivity of the instruments is proportional to the number of receivers, interferometers normally present a reduced number of them due to the difficulty to correlate a large number of wide-band signals. For this reason, thinking about a Michelson-type interferometer, two types of single base-line correlators are proposed in order to compare them and to analyse their viability. The first choice is an analog correlator designed on FR4 substrate with a 10 kHz video bandwidth. The maximum frequency of the correlator input signals should not exceed 300MHz. On the other hand, a digital version has been implemented using a PCI card from Agilent Technologies with a maximum digitalization rate of 1GS/s on each of its two inputs

Caracterización de la compresión en LNAs para aplicaciones de astronomía

In this work, system level modelling and realistic simulation and measurement results of a 31 GHz Back-End Module (BEM) Low-Noise Amplifier (LNA), designed for the QUIJOTE CMB (Q U I JOint TEnerife CMB) experiment radiometer, are reported. The signals received by radiometers can be identified as continuous spectre gaussian white noise signals. This makes necessary time-domain simulation techniques and appropriate models for the realistic analysis of radiometers behaviour. The measured-based modelling of one BEM´s LNA, its simulation in nominal conditions and the measurement of the nonlinear characteristic by using filtered white noise excitation signals, will be shown. Typically, in the LNAs design process the linearity is not taken into account but, as we will see, in the radiometers case, the nature of Gaussian noise excitation signals makes amplifiers to present higher nonlinearity in their characteristics than when using single tone excitation signals. Therefore, in order to analyze the suitability of the LNAs nominal operation, linearity figures of merit have to be obtained, but using realistic excitation signals. In this paper, the LNAs nonlinear characteristics with gaussian noise excitation signals have been obtained

Modelado, simulación y medida de la compresión en LNAs para aplicaciones de astronomía

In this work, system level modelling and realistic simulation and measurement results of a 31 GHz Back-End Module (BEM) Low-Noise Amplifier (LNA), designed for the QUIJOTE CMB (Q U I JOint TEnerife CMB) experiment radiometer, are reported. The signals received by radiometers can be identified as continuous spectre gaussian white noise signals. This makes necessary time-domain simulation techniques and appropriate models for the realistic analysis of radiometers behaviour. The measured-based modelling of one BEM´s LNA, its simulation in nominal conditions and the measurement of the nonlinear characteristic by using filtered white noise excitation signals, will be shown. Typically, in the LNAs design process the linearity is not taken into account but, as we will see, in the radiometers case, the nature of gaussian noise excitation signals makes amplifiers to present higher nonlinearity in their characteristics than when using single tone excitation signals. Therefore, in order to analyze the suitability of the LNAs nominal operation, linearity figures of merit have to be obtained, but using realistic excitation signals. In this paper, the LNAs nonlinear characteristics with gaussian noise excitation signals have been obtained by simulation and measurement

QUIJOTE scientific results - IV. A northern sky survey in intensity and polarization at 10-20-GHz with the multifrequency instrument

We present QUIJOTE intensity and polarization maps in four frequency bands centred around 11, 13, 17, and 19-GHz, and covering approximately 29?000?deg2, including most of the northern sky region. These maps result from 9000?h of observations taken between May 2013 and June 2018 with the first QUIJOTE multifrequency instrument (MFI), and have angular resolutions of around 1°, and sensitivities in polarization within the range 35?40?µK per 1° beam, being a factor ?2?4 worse in intensity. We discuss the data processing pipeline employed, and the basic characteristics of the maps in terms of real space statistics and angular power spectra. A number of validation tests have been applied to characterize the accuracy of the calibration and the residual level of systematic effects, finding a conservative overall calibration uncertainty of 5 per?cent. We also discuss flux densities for four bright celestial sources (Tau A, Cas A, Cyg A, and 3C274), which are often used as calibrators at microwave frequencies. The polarization signal in our maps is dominated by synchrotron emission. The distribution of spectral index values between the 11?GHz and WMAP 23?GHz map peaks at [Beta] = -3.09 with a standard deviation of 0.14. The measured BB/EE ratio at scales of [L lower case+ = 80 is 0.26 ± 0.07 for a Galactic cut |b| > 10°. We find a positive TE correlation for 11?GHz at large angular scales ([L lower case+ [less than or equivalent to] 50), while the EB and TB signals are consistent with zero in the multipole range 30 [less than or equivalent to] [L lower case+ [less than or equivalent to] 150. The maps discussed in this paper are publicly available.We thank the staff of the Teide Observatory for invaluable assistance in the commissioning and operation of QUIJOTE. The QUIJOTE experiment is being developed by the Instituto de Astrofisica de Canarias (IAC), the Instituto de Fisica de Cantabria (IFCA), and the Universities of Cantabria, Manchester and Cambridge. Partial finan- cial support was provided by the Spanish Ministry of Science and Innovation under the projects AYA2007-68058-C03-01, AYA2007- 68058-C03-02, AYA2010-21766-C03-01, AYA2010-21766-C03-02, AYA2014-60438-P, ESP2015-70646-C2-1-R, AYA2017-84185-P, ESP2017-83921-C2-1-R, AYA2017-90675-REDC (co-funded with EU FEDER funds), PGC2018-101814-B-I00, PID2019-110610RB- C21, PID2020-120514GB-I00, IACA13-3E-2336, IACA15-BE- 3707, EQC2018-004918-P, the Severo Ochoa Programs SEV-2015- 0548 and CEX2019-000920-S, the Maria de Maeztu Program MDM- 2017-0765, and by the Consolider-Ingenio project CSD2010-00064 (EPI: Exploring the Physics of Inflation). We acknowledge support from the ACIISI, Consejeria de Economia, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference ProID2020010108. This project has received funding from the European Union’s Horizon 2020 - Research and Innovation Framework Programme under grant agreement number 687312 (RADIOFOREGROUNDS). This research made use of computing time available on the high-performance computing systems at the IAC. We thankfully acknowledge the technical expertise and assistance provided by the Spanish Supercomputing Network (Red Espa ˜ nola de Supercom- putaci ´on), as well as the computer resources used: the Deimos/Di v a Supercomputer, located at the IAC. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The PWV data used in the tests presented in Section 4 comes from the Iza ˜ na Atmospheric Observatory (IZO), and have been made available to us by the Iza ˜ na Atmospheric Research Center (AEMET). SEH and CD acknowledge support from the STFC Consolidated Grant (ST/P000649/1). FP acknowledges support from the Spanish State Research Agency (AEI) under grant number PID2019-105552RB- C43. DT acknowledges the support from the Chinese Academy of Sciences (CAS) President’s International Fellowship Initiative (PIFI) with Grant N. 2020PM0042. Some of the presented results are based on observations obtained with Planck ( http:// www.esa.int/ Planck), an ESA science mission with instruments and contributions directly funded by ESA Member States, NASA, and Canada. We acknowl- edge the use of the Le gac y Archiv e for Microwav e Background Data Analysis (LAMBDA). Support for LAMBDA is provided by the NASA Office of Space Science. Some of the results in this paper have been derived using the HEALPIX (G ´orski et al. 2005 ) and HEALPY (Zonca et al. 2019 ) packages. We also use Numpy (Harris et al. 2020 ), Matplotlib (Hunter 2007 ), and the SKLEARN module (Pedregosa et al. 2011 )

Modelado y simulación realista del módulo posterior de un radiómetro: aplicación al instrumento a 31 GHz del experimento QUIJOTE

In the reported work, an efficient modelling method is applied to the circuits of the 30 GHz Back End Module of the QUIJOTE experiment radiometer. In particular, efficient models of two LNAs, a band pass filter and a detector has been obtained. These models allow realistic time-domain BEM simulation by using Gaussian noise excitation signals. Simulation results have been reported, showing good agreement with the BEM expected operation. On the other hand, time-domain realistic simulations will provide valuable information about BEM behaviour previously to the receiver definitive implementation

A microwave polarimeter demonstrator for astronomy with near-infra-red up-conversion for optical correlation and detection

This paper presents a 10 to 20 GHz bandwidth microwave polarimeter demonstrator, based on the implementation of a near-infra-red frequency up-conversion stage that allows both the optical correlation, when operating as a synthesized-image interferometer, and signal detection, when operating as a direct-image instrument. The proposed idea is oriented towards the implementation of ultra-sensitive instruments presenting several dozens or even thousands of microwave receivers operating in the lowest bands of the cosmic microwave background. In this work, an electro-optical back-end module replaces the usual microwave detection stage with Mach–Zehnder modulators for the frequency up-conversion, and an optical stage for the signals correlation and detection at near-infra-red wavelengths (1550 nm). As interferometer, the instrument is able to correlate the signals of large-format instruments, while operating as a direct imaging instrument also presents advantages in terms of the possibility of implementing the optical back end by means of photonic integrated circuits to achieve reductions in cost, weight, size, and power consumption. A linearly polarized input wave, with a variable polar angle, is used as a signal source for laboratory tests. The receiver demonstrator has proved its capabilities of being used as a new microwave-photonic polarimeter for the study of the lowest bands of cosmic microwave background.The authors would like to thank Spanish Ministry for Economy and Competitiveness (currently Ministry of Science, innovation and Universities) for the financial support provided under the projects with references ESP2015-70646-C2-1-R, AYA2015-72768-EXP, ESP2017-83921-C2-1-R, TEC2013-47264-C2-1-R, TEC2016-76021-C2-2-R and CIBERBBN all co-financed with EU FEDER funds

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

This paper presents the analysis, design, and characterization of the thirty gigahertz instrument receiver developed for the Q-U-I Joint Tenerife experiment. The receiver is aimed to obtain polarization data of the cosmic microwave background radiation from the sky, obtaining the Q,U, and I Stokes parameters of the incoming signal simultaneously. A comprehensive analysis of the theory behind the proposed receiver is presented for a linearly polarized input signal, and the functionality tests have demonstrated adequate results in terms of Stokes parameters, which validate the concept of the receiver based on electronic phase switching