6 research outputs found
Estudi de la coautoria de publicacions cientĂfiques entre la Universitat Politècnica de Catalunya i l’Aalto University
S'analitza la coautoria de la UPC amb autors vinculats a l'Aalto University, per totes les Ă rees temĂ tiques i sense considerar lĂmits cronològics o documentals.Postprint (published version
Calibration of a polarimetric microwave radiometer using a double directional coupler
This paper presents a built-in calibration procedure of a 10-to-20 GHz polarimeter aimed at measuring the I, Q, U Stokes parameters of cosmic microwave background (CMB) radiation. A full-band square waveguide double directional coupler, mounted in the antenna-feed system, is used to inject differently polarized reference waves. A brief description of the polarimetric microwave radiometer and the system calibration injector is also reported. A fully polarimetric calibration is also possible using the designed double directional coupler, although the presented calibration method in this paper is proposed to obtain three of the four Stokes parameters with the introduced microwave receiver, since V parameter is expected to be zero for the CMB radiation. Experimental results are presented for linearly polarized input waves in order to validate the built-in calibration system.The authors would like to thank The Spanish Ministry of Science and Innovation for financial support provided through the grants ESP2015-70646-C2-2-R, ESP2017-83921-C2-2-R and PID2019-110610RB-C2
Polarimetric Microwave Radiometer Calibration.
A polarimetric radiometer is a radiometer with the capability to measure the correlation information between vertically and horizontally polarized electric fields. To better understand and calibrate this type of radiometer, several research efforts have been undertaken.
1) All microwave radiometer measurements of brightness temperature (TB) include an additive noise component. The variance and correlation statistics of the additive noise component of fully polarimetric radiometer measurements are derived from theoretical considerations and the resulting relationships are verified experimentally. It is found that the noise can be correlated among polarimetric channels and that the correlation statistics can vary as a function of the polarization state of the scene under observation.
2) A polarimetric radiometer calibration algorithm has been developed which makes use of the Correlated Noise Calibration Standard (CNCS) to aid in the characterization of microwave polarimetric radiometers and to characterize the non-ideal characteristics of the CNCS itself simultaneously. CNCS has been developed by the Space Physics Research Laboratory of the University of Michigan (SPRL). The calibration algorithm has been verified using the DetMit L-band radiometer. The precision of the calibration is estimated by Monte Carlo simulations. A CNCS forward model has been developed to describe the non-ideal characteristics of the CNCS. Impedance-mismatches between the CNCS and radiometer under test are also considered in the calibration.
3) The calibration technique is demonstrated by applying it to the Engineering Model (EM) of the NASA Aquarius radiometer. CNCS is used to calibrate the Aquarius radiometer – specifically to retrieve its channel phase imbalance and the thermal emission characteristics of transmission line between its antenna and receiver. The impact of errors in calibration of the radiometer channel phase imbalance on Sea Surface Salinity (SSS) retrievals by Aquarius is also analyzed.
4) The CNCS has also been used to calibrate the Breadboard Model (BM) of the L-band NASA Juno radiometer. In order to cover the broad TB dynamic range of the Juno radiometer, a special linearization process has been developed for the CNCS. The method combines multiple Arbitrary Waveform Generator gaussian noise signals with different values of variance to construct the necessary range of TB levelsPh.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/61741/1/jzhpeng_1.pd
A calibration method for fully polarimetric microwave radiometers
A technique for absolute end-to-end calibration
of a fully polarimetric microwave radiometer is presented. The
technique is based on the tripolarimetric calibration technique
of Gasiewski and Kunkee, but is extended to provide a means of
calibrating all four Stokes parameters. The extension is facilitated
using a biaxial phase-retarding microwave plate to provide a
precisely known fourth Stokes signal from the Gasiewski–Kunkee
(GK) linearly polarized standard. The relations needed to determine
the Stokes vector produced by the augmented standard
are presented, and the effects of nonidealities in the various
components are discussed. The application of the extended
standard to determining the complete set of radiometer constants
(the calibration matrix elements) for the National Oceanic and
Atmospheric Administration Polarimetric Scanning Radiometer
in a laboratory environment is illustrated. A calibration matrix
inversion technique and error analysis are described, as well. The
uncertainties associated with practical implementation of the fully
polarimetric standard for spaceborne wind vector measurements
are discussed relative to error thresholds anticipated for wind
vector retrieval from the U.S. National Polar-Orbiting Environmental
Satellite System
A calibration method for fully polarimetric microwave radiometers
A technique for absolute end-to-end calibration
of a fully polarimetric microwave radiometer is presented. The
technique is based on the tripolarimetric calibration technique
of Gasiewski and Kunkee, but is extended to provide a means of
calibrating all four Stokes parameters. The extension is facilitated
using a biaxial phase-retarding microwave plate to provide a
precisely known fourth Stokes signal from the Gasiewski–Kunkee
(GK) linearly polarized standard. The relations needed to determine
the Stokes vector produced by the augmented standard
are presented, and the effects of nonidealities in the various
components are discussed. The application of the extended
standard to determining the complete set of radiometer constants
(the calibration matrix elements) for the National Oceanic and
Atmospheric Administration Polarimetric Scanning Radiometer
in a laboratory environment is illustrated. A calibration matrix
inversion technique and error analysis are described, as well. The
uncertainties associated with practical implementation of the fully
polarimetric standard for spaceborne wind vector measurements
are discussed relative to error thresholds anticipated for wind
vector retrieval from the U.S. National Polar-Orbiting Environmental
Satellite System