A correction was published on 15 September 2009,
Sensors 2009, 9(9), 7430
Open AccessThis article is
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Calibration of Correlation Radiometers Using Pseudo-Random Noise Signals
Remote Sensing Lab., Dept. Signal Theory and Communications, Universitat Politècnica de Catalunya (UPC) Campus Nord, Bldg D3, E-08034 Barcelona, Spain
DAS Photonics, Ciudad Politécnica de la Innovación, Camino de Vera s/n, Edificio 8F, E-46022 Valencia, Spain
* Author to whom correspondence should be addressed.
Received: 1 July 2009; in revised form: 29 July 2009 / Accepted: 31 July 2009 / Published: 3 August 2009
Abstract: The calibration of correlation radiometers, and particularly aperture synthesis interferometric radiometers, is a critical issue to ensure their performance. Current calibration techniques are based on the measurement of the cross-correlation of receivers’ outputs when injecting noise from a common noise source requiring a very stable distribution network. For large interferometric radiometers this centralized noise injection approach is very complex from the point of view of mass, volume and phase/amplitude equalization. Distributed noise injection techniques have been proposed as a feasible alternative, but are unable to correct for the so-called “baseline errors” associated with the particular pair of receivers forming the baseline. In this work it is proposed the use of centralized Pseudo-Random Noise (PRN) signals to calibrate correlation radiometers. PRNs are sequences of symbols with a long repetition period that have a flat spectrum over a bandwidth which is determined by the symbol rate. Since their spectrum resembles that of thermal noise, they can be used to calibrate correlation radiometers. At the same time, since these sequences are deterministic, new calibration schemes can be envisaged, such as the correlation of each receiver’s output with a baseband local replica of the PRN sequence, as well as new distribution schemes of calibration signals. This work analyzes the general requirements and performance of using PRN sequences for the calibration of microwave correlation radiometers, and particularizes the study to a potential implementation in a large aperture synthesis radiometer using an optical distribution network.
Keywords: correlation radiometers; calibration; Pseudo-Random Noise; PRN
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Pérez, I.R.; Bosch-Lluis, X.; Camps, A.; Alvarez, N.R.; Hernandez, J.F.M.; Domènech, E.V.; Vernich, C.; De la Rosa, S.; Pantoja, S. Calibration of Correlation Radiometers Using Pseudo-Random Noise Signals. Sensors 2009, 9, 6131-6149.
Pérez IR, Bosch-Lluis X, Camps A, Alvarez NR, Hernandez JFM, Domènech EV, Vernich C, De la Rosa S, Pantoja S. Calibration of Correlation Radiometers Using Pseudo-Random Noise Signals. Sensors. 2009; 9(8):6131-6149.
Pérez, Isaac R.; Bosch-Lluis, Xavi; Camps, Adriano; Alvarez, Nereida R.; Hernandez, Juan F. M.; Domènech, Enric V.; Vernich, Carlos; De la Rosa, Sonia; Pantoja, Sebastián. 2009. "Calibration of Correlation Radiometers Using Pseudo-Random Noise Signals." Sensors 9, no. 8: 6131-6149.