{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:54:12Z","timestamp":1760147652609,"version":"build-2065373602"},"reference-count":15,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2023,2,20]],"date-time":"2023-02-20T00:00:00Z","timestamp":1676851200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Active Radar Calibrators (ARC), also called calibration transponders, are often used as reference targets for absolute radiometric calibration of radar systems due to their large achievable Radar Cross-Section (RCS). However, before using a transponder as a reference target, the hardware itself has to be calibrated. A novel method, called the three-transponder method, was proposed some years ago and allows for RCS calibration of digital transponders without using any RCS targets as reference. In this paper, this technique is further refined and applied to a setup utilizing only one digital transponder. The accurate measurement design is described and a novel, elaborated data processing scheme is developed to minimize remaining noise and clutter effects in the data. A comprehensive error analysis is presented in the second part of this paper.<\/jats:p>","DOI":"10.3390\/rs15041153","type":"journal-article","created":{"date-parts":[[2023,2,20]],"date-time":"2023-02-20T04:28:57Z","timestamp":1676867337000},"page":"1153","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Highly Accurate Radar Cross-Section and Transfer Function Measurement of a Digital Calibration Transponder without Known Reference\u2014Part I: Measurement and Results"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0650-9073","authenticated-orcid":false,"given":"Jens","family":"Reimann","sequence":"first","affiliation":[{"name":"Deutsches Zentrum f\u00fcr Luft- und Raumfahrt e.V., Institut f\u00fcr Hochfrequenztechnik und Radarsysteme, 82234 Wessling, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3827-7932","authenticated-orcid":false,"given":"Anna Maria","family":"B\u00fcchner","sequence":"additional","affiliation":[{"name":"Deutsches Zentrum f\u00fcr Luft- und Raumfahrt e.V., Institut f\u00fcr Hochfrequenztechnik und Radarsysteme, 82234 Wessling, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4902-5551","authenticated-orcid":false,"given":"Sebastian","family":"Raab","sequence":"additional","affiliation":[{"name":"Deutsches Zentrum f\u00fcr Luft- und Raumfahrt e.V., Institut f\u00fcr Hochfrequenztechnik und Radarsysteme, 82234 Wessling, Germany"}]},{"given":"Klaus","family":"Weidenhaupt","sequence":"additional","affiliation":[{"name":"Deutsches Zentrum f\u00fcr Luft- und Raumfahrt e.V., Institut f\u00fcr Hochfrequenztechnik und Radarsysteme, 82234 Wessling, Germany"}]},{"given":"Matthias","family":"Jirousek","sequence":"additional","affiliation":[{"name":"Deutsches Zentrum f\u00fcr Luft- und Raumfahrt e.V., Institut f\u00fcr Hochfrequenztechnik und Radarsysteme, 82234 Wessling, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0045-3726","authenticated-orcid":false,"given":"Marco","family":"Schwerdt","sequence":"additional","affiliation":[{"name":"Deutsches Zentrum f\u00fcr Luft- und Raumfahrt e.V., Institut f\u00fcr Hochfrequenztechnik und Radarsysteme, 82234 Wessling, Germany"}]}],"member":"1968","published-online":{"date-parts":[[2023,2,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"487","DOI":"10.1109\/TGRS.2012.2201946","article-title":"High-Precision Assessment and Calibration of Polarimetric RADARSAT-2 SAR Using Transponder Measurements","volume":"51","author":"Touzi","year":"2013","journal-title":"IEEE Trans. Geosci. Remote. Sens."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1269","DOI":"10.1109\/TGRS.2017.2745206","article-title":"A Polarimetric Active Transponder With Extremely Large RCS for Absolute Radiometric Calibration of SMAP Radar","volume":"56","author":"Sarabandi","year":"2018","journal-title":"IEEE Trans. Geosci. Remote. Sens."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"677","DOI":"10.1109\/TGRS.2009.2035308","article-title":"Final TerraSAR-X Calibration Results Based on Novel Efficient Methods","volume":"48","author":"Schwerdt","year":"2010","journal-title":"IEEE Trans. Geosci. Remote. Sens."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"3053","DOI":"10.1109\/JLT.2016.2535487","article-title":"Digital Compensation of Bandwidth Limitations for High-Speed DACs and ADCs","volume":"34","author":"Napoli","year":"2016","journal-title":"J. Light. Technol."},{"key":"ref_5","unstructured":"Jirousek, M., Doering, B., Rudolf, D., Raab, S., and Schwerdt, M. (2014, January 3\u20135). Development of the highly accurate DLR kalibri transponder. Proceedings of the EUSAR 2014, 10th European Conference on Synthetic Aperture Radar, Berlin, Germany."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Cendes, Z. (July, January 26). The development of HFSS. Proceedings of the 2016 USNC-URSI Radio Science Meeting, Fajardo, PR, USA.","DOI":"10.1109\/USNC-URSI.2016.7588501"},{"key":"ref_7","first-page":"Nr-171","article-title":"Erweiterte Momentenmethode zur Behandlung kompliziert aufgebauter und elektrisch grosser elektromagnetischer Steuprobleme","volume":"21","author":"Jakobus","year":"1995","journal-title":"Fortschrittsberichte VDI"},{"key":"ref_8","unstructured":"Raab, S., D\u00f6ring, B., Jirousek, M., Reimann, J., Rudolf, D., and Schwerdt, M. (2014, January 3\u20135). Comparison of Absolute Radiometric Transponder Calibration Strategies. Proceedings of the 10th European Conference on Synthetic Aperture Radar, Berlin, Germany."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Rudolf, D., Raab, S., D\u00f6ring, B.J., Jirousek, M., Reimann, J., and Schwerdt, M. (2015, January 16\u201318). Absolute radiometric calibration of the novel DLR \u201cKalibri\u201d transponder. Proceedings of the 2015 German Microwave Conference, N\u00fcrnberg, Germany.","DOI":"10.1109\/GEMIC.2015.7107819"},{"key":"ref_10","first-page":"297","article-title":"The Three-Transponder Method: A Novel Method for Accurate Transponder RCS Calibration","volume":"61","author":"Jirousek","year":"2015","journal-title":"Prog. Electromagn. Res. B"},{"key":"ref_11","unstructured":"(1979). IEEE Standard Test Procedures for Antennas (Standard No. 149-1977)."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1109\/TGRS.1984.350610","article-title":"Active Reflector for Radar Calibration","volume":"GE-22","author":"Brunfeldt","year":"1984","journal-title":"IEEE Trans. Geosci. Remote. Sens."},{"key":"ref_13","unstructured":"Weidenhaupt, K., Schwerdt, M., Raab, S., B\u00fcchner, A., Reimann, J., Jirousek, M., and Limbach, M. (2019, January 1\u20133). DLR\u2019s next Generation of fully Polarimetric Calibration Transponders. Proceedings of the ASAR, Montreal, QC, Canada."},{"key":"ref_14","unstructured":"Raab, S., Doering, B.J., Rudolf, D., Reimann, J., and Schwerdt, M. (2016, January 6\u20139). Analysis of an Improved Temperature Management Concept for SAR System Calibration Transponders. Proceedings of the EUSAR 2016: 11th European Conference on Synthetic Aperture Radar, Hamburg, Germany."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"374","DOI":"10.1109\/36.54363","article-title":"Synthetic aperture radar calibration using reference reflectors","volume":"28","author":"Gray","year":"1990","journal-title":"IEEE Trans. Geosci. Remote. Sens."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/15\/4\/1153\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T18:37:06Z","timestamp":1760121426000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/15\/4\/1153"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,2,20]]},"references-count":15,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2023,2]]}},"alternative-id":["rs15041153"],"URL":"https:\/\/doi.org\/10.3390\/rs15041153","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2023,2,20]]}}}