{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,25]],"date-time":"2026-04-25T09:47:23Z","timestamp":1777110443838,"version":"3.51.4"},"reference-count":23,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2009,8,3]],"date-time":"2009-08-03T00:00:00Z","timestamp":1249257600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":["www.mdpi.com"],"crossmark-restriction":true},"short-container-title":["Sensors"],"abstract":"<jats:p>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\u2019 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 \u201cbaseline errors\u201d 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\u2019s 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.<\/jats:p>","DOI":"10.3390\/s90806131","type":"journal-article","created":{"date-parts":[[2009,8,3]],"date-time":"2009-08-03T13:05:58Z","timestamp":1249304758000},"page":"6131-6149","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["Calibration of Correlation Radiometers Using Pseudo-Random Noise Signals"],"prefix":"10.3390","volume":"9","author":[{"given":"Isaac Ramos","family":"P\u00e9rez","sequence":"first","affiliation":[{"name":"Remote Sensing Lab., Dept. Signal Theory and Communications, Universitat Polit\u00e8cnica de Catalunya (UPC) Campus Nord, Bldg D3, E-08034 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xavi","family":"Bosch-Lluis","sequence":"additional","affiliation":[{"name":"Remote Sensing Lab., Dept. Signal Theory and Communications, Universitat Polit\u00e8cnica de Catalunya (UPC) Campus Nord, Bldg D3, E-08034 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9514-4992","authenticated-orcid":false,"given":"Adriano","family":"Camps","sequence":"additional","affiliation":[{"name":"Remote Sensing Lab., Dept. Signal Theory and Communications, Universitat Polit\u00e8cnica de Catalunya (UPC) Campus Nord, Bldg D3, E-08034 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nereida Rodriguez","family":"Alvarez","sequence":"additional","affiliation":[{"name":"Remote Sensing Lab., Dept. Signal Theory and Communications, Universitat Polit\u00e8cnica de Catalunya (UPC) Campus Nord, Bldg D3, E-08034 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Juan F. March\u00e1n","family":"Hernandez","sequence":"additional","affiliation":[{"name":"Remote Sensing Lab., Dept. Signal Theory and Communications, Universitat Polit\u00e8cnica de Catalunya (UPC) Campus Nord, Bldg D3, E-08034 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Enric Valencia","family":"Dom\u00e8nech","sequence":"additional","affiliation":[{"name":"Remote Sensing Lab., Dept. Signal Theory and Communications, Universitat Polit\u00e8cnica de Catalunya (UPC) Campus Nord, Bldg D3, E-08034 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Carlos","family":"Vernich","sequence":"additional","affiliation":[{"name":"DAS Photonics, Ciudad Polit\u00e9cnica de la Innovaci\u00f3n, Camino de Vera s\/n, Edificio 8F, E-46022 Valencia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sonia","family":"De la Rosa","sequence":"additional","affiliation":[{"name":"DAS Photonics, Ciudad Polit\u00e9cnica de la Innovaci\u00f3n, Camino de Vera s\/n, Edificio 8F, E-46022 Valencia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sebasti\u00e1n","family":"Pantoja","sequence":"additional","affiliation":[{"name":"DAS Photonics, Ciudad Polit\u00e9cnica de la Innovaci\u00f3n, Camino de Vera s\/n, Edificio 8F, E-46022 Valencia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2009,8,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Thompson, A.R., Moran, J.M., and Swenson, G.W. 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