{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,18]],"date-time":"2026-03-18T09:18:43Z","timestamp":1773825523946,"version":"3.50.1"},"reference-count":53,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2024,5,27]],"date-time":"2024-05-27T00:00:00Z","timestamp":1716768000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"German Federal Ministry for Economic Affairs and Climate Action (BMWK)","award":["20D1905"],"award-info":[{"award-number":["20D1905"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Increasing airspace safety is an important challenge, both for unmanned aerial vehicles (UAVs) as well as manned aircraft. Future developments of collision avoidance systems are supposed to utilize information from multiple sensing systems. A compact sensing system could employ a multi-mode multi-port antenna (M\u00a03PA). Their ability to radiate multiple orthogonal patterns simultaneously makes them suitable for communication applications as well as bearing and ranging applications. Furthermore, they can be designed to flexibly originate near-omnidirectional and\/or directional radiation patterns. This option of flexibility with respect to the radiation characteristic is desired for antennas integrated in collision avoidance systems. Based on the aforementioned properties, M\u00a03PAs represent a compelling option for aircraft transponders. In this paper, direction-of-arrival (DoA) estimation using an M\u00a03PA designed for aerial applications is put to the test. First, a DoA estimation scheme suitable to be employed with M\u00a03PAs is introduced. Next, the validity of the proposed method is confirmed through numerical simulations. Lastly, practical experiments are conducted in an antenna measurement chamber to verify the numerical results.<\/jats:p>","DOI":"10.3390\/s24113452","type":"journal-article","created":{"date-parts":[[2024,5,27]],"date-time":"2024-05-27T09:33:31Z","timestamp":1716802411000},"page":"3452","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Direction-of-Arrival Estimation for Unmanned Aerial Vehicles and Aircraft Transponders Using a Multi-Mode Multi-Port Antenna"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9774-2286","authenticated-orcid":false,"given":"Sami Alkubti","family":"Almasri","sequence":"first","affiliation":[{"name":"Chair of Information and Coding Theory, Kiel University, 24143 Kiel, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1533-5175","authenticated-orcid":false,"given":"Nils L.","family":"Johannsen","sequence":"additional","affiliation":[{"name":"Chair of Information and Coding Theory, Kiel University, 24143 Kiel, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3475-1710","authenticated-orcid":false,"given":"Peter A.","family":"Hoeher","sequence":"additional","affiliation":[{"name":"Chair of Information and Coding Theory, Kiel University, 24143 Kiel, Germany"}]}],"member":"1968","published-online":{"date-parts":[[2024,5,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1016\/j.paerosci.2008.08.001","article-title":"On Unmanned Aircraft Systems Issues, Challenges and Operational Restrictions Preventing Integration into the National Airspace System","volume":"44","author":"Dalamagkidis","year":"2008","journal-title":"Prog. Aerosp. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1109\/MAES.2009.4772749","article-title":"UAVs in Civil Airspace: Safety Requirements","volume":"24","author":"Loh","year":"2009","journal-title":"IEEE Aerosp. Electron. Syst. Mag."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Balestrieri, E., Daponte, P., De Vito, L., Picariello, F., and Tudosa, I. (2021). Sensors and Measurements for UAV Safety: An Overview. Sensors, 21.","DOI":"10.3390\/s21248253"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2809","DOI":"10.1109\/TITS.2021.3108995","article-title":"Unmanned Aircraft System Airspace Structure and Safety Measures Based on Spatial Digital Twins","volume":"23","author":"Wang","year":"2022","journal-title":"IEEE Trans. Intell. Transp. Syst."},{"key":"ref_5","unstructured":"EUROCONTROL (2024, March 31). ACAS Guide. Available online: https:\/\/www.eurocontrol.int\/system\/acas."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Manfredi, G., and Jestin, Y. (2016, January 25\u201329). An Introduction to ACAS Xu and the Challenges Ahead. Proceedings of the 2016 IEEE\/AIAA 35th Digital Avionics Systems Conference (DASC), Sacramento, CA, USA.","DOI":"10.1109\/DASC.2016.7778055"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Balestrieri, E., Daponte, P., De Vito, L., and Lamonaca, F. (2021). Sensors and Measurements for Unmanned Systems: An Overview. Sensors, 21.","DOI":"10.3390\/s21041518"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Corraro, F., Corraro, G., Cuciniello, G., and Garbarino, L. (2022). Unmanned Aircraft Collision Detection and Avoidance for Dealing with Multiple Hazards. Aerospace, 9.","DOI":"10.3390\/aerospace9040190"},{"key":"ref_9","first-page":"6949","article-title":"A Review on 6G for Space-Air-Ground Integrated Network: Key Enablers, Open Challenges, and Future Direction","volume":"34","author":"Ray","year":"2022","journal-title":"J. King Saud Univ.-Comput. Inf. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.cja.2021.04.025","article-title":"Green UAV Communications for 6G: A Survey","volume":"35","author":"Jiang","year":"2022","journal-title":"Chin. J. Aeronaut."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.cja.2021.12.013","article-title":"6G Service-Oriented Space-Air-Ground Integrated Network: A Survey","volume":"35","author":"Cheng","year":"2022","journal-title":"Chin. J. Aeronaut."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Dicandia, F.A., Fonseca, N.J., Bacco, M., Mugnaini, S., and Genovesi, S. (2022). Space-Air-Ground Integrated 6G Wireless Communication Networks: A Review of Antenna Technologies and Application Scenarios. Sensors, 22.","DOI":"10.3390\/s22093136"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"74","DOI":"10.1109\/MCOM.005.2100142","article-title":"Toward 6G with Connected Sky: UAVs and Beyond","volume":"59","author":"Mozaffari","year":"2021","journal-title":"IEEE Commun. Mag."},{"key":"ref_14","first-page":"2183","article-title":"Cooperative Conflict Detection and Resolution and Safety Assessment for 6G Enabled Unmanned Aerial Vehicles","volume":"24","author":"Li","year":"2023","journal-title":"IEEE Trans. Intell. Transp. Syst."},{"key":"ref_15","unstructured":"International Civil Aviation Organization (2006). Airborne Collision Avoidance System Manual, International Civil Aviation Organization. [1st ed.]."},{"key":"ref_16","unstructured":"Tuncer, T.E., and Friedlander, F. (2009). Classical and Modern Direction-of-Arrival Estimation, Academic Press."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1109\/MAP.2022.3145714","article-title":"Characteristic Mode-Inspired Advanced Multiple Antennas: Intuitive Insight Into Element-, Interelement-, and Array Levels of Compact Large Arrays and Metantennas","volume":"64","author":"Manteuffel","year":"2022","journal-title":"IEEE Antennas Propag. Mag."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"622","DOI":"10.1109\/TAP.1971.1139999","article-title":"Theory of Characteristic Modes for Conducting Bodies","volume":"19","author":"Harrington","year":"1971","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Chen, Y., and Wang, C.F. (2015). Characteristic Modes: Theory and Applications in Antenna Engineering, John Wiley & Sons.","DOI":"10.1002\/9781119038900"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Lu, W.J., and Zhu, L. (2022). Multi-Mode Resonant Antennas: Theory, Design, and Applications, CRC Press.","DOI":"10.1201\/9781003291633"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"3902","DOI":"10.1109\/TAP.2019.2905718","article-title":"Upper Bounds and Design Guidelines for Realizing Uncorrelated Ports on Multi-Mode Antennas Based on Symmetry Analysis of Characteristic Modes","volume":"67","author":"Peitzmeier","year":"2019","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1109\/TAP.2021.3098610","article-title":"Systematic Design of Multimode Antennas for MIMO Applications by Leveraging Symmetry","volume":"70","author":"Peitzmeier","year":"2022","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2689","DOI":"10.1109\/TAP.2016.2537388","article-title":"Compact Multimode Multielement Antenna for Indoor UWB Massive MIMO","volume":"64","author":"Manteuffel","year":"2016","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"429","DOI":"10.1515\/freq-2017-0148","article-title":"Ultra-Wideband Massive MIMO Communications Using Multi-mode Antennas","volume":"71","author":"Hoeher","year":"2017","journal-title":"Frequenz"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"e2934","DOI":"10.1002\/ett.2934","article-title":"A massive MIMO Terminal Concept Based on Small-Size Multi-Mode Antennas","volume":"28","author":"Hoeher","year":"2017","journal-title":"Trans. Emerg. Telecommun. Technol."},{"key":"ref_26","first-page":"1120","article-title":"Single-Element Beamforming Using Multi-Mode Antenna Patterns","volume":"9","author":"Johannsen","year":"2020","journal-title":"IEEE Wirel. Commun. Lett."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1109\/MCOM.001.1900429","article-title":"On the Feasibility of Multi-Mode Antennas in UWB and IoT Applications Below 10 GHz","volume":"58","author":"Johannsen","year":"2020","journal-title":"IEEE Commun. Mag."},{"key":"ref_28","unstructured":"Johannsen, N.L., Hoeher, P.A., Peitzmeier, N., and Manteuffel, D. (2022). Wireless 100 Gbps and Beyond: Architectures, Approaches and Findings of German Research Foundation (DFG) Priority Programme SPP1655, IHP\u2014Innovations for High Performance Microelectronics."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Ojaroudi Parchin, N., Jahanbakhsh Basherlou, H., and Abd-Alhameed, R.A. (2020). Design of Multi-Mode Antenna Array for Use in Next-Generation Mobile Handsets. Sensors, 20.","DOI":"10.3390\/s20092447"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Almasri, S.A., Doose, N., and Hoeher, P.A. (2017, January 25\u201326). Parametric Direction-of-Arrival Estimation for Multi-Mode Antennas. Proceedings of the 14th Workshop on Positioning, Navigation and Communications (WPNC), Bremen, Germany.","DOI":"10.1109\/WPNC.2017.8250060"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"3374","DOI":"10.1109\/TAP.2019.2899010","article-title":"On the Potential of Multi-Mode Antennas for Direction-of-Arrival Estimation","volume":"67","author":"Almasri","year":"2019","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"4585","DOI":"10.1109\/JSEN.2019.2902674","article-title":"Modeling Aspects of Planar Multi-Mode Antennas for Direction-of-Arrival Estimation","volume":"19","author":"Almasri","year":"2019","journal-title":"IEEE Sens. J."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1109\/OJCOMS.2023.3338529","article-title":"Joint Communication and Sensing Using Compressive Sensing and a Single Multi-Mode Multi-Port Antenna","volume":"5","author":"Johannsen","year":"2024","journal-title":"IEEE Open J. Commun. Soc."},{"key":"ref_34","unstructured":"Johannsen, N.L., Schurwanz, M., Grundmann, L., Mietzner, J., Manteuffel, D., and Hoeher, P.A. (2022). Joint Communication, Sensing and Localization for Airborne Applications. arXiv."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"11024","DOI":"10.1109\/TAP.2022.3191418","article-title":"Geometry-Based UAV MIMO Channel Modeling and Pattern Optimization for Multimode Antennas","volume":"70","author":"Johannsen","year":"2022","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_36","unstructured":"EUROCAE (2020). Minimum Operational Performance Standards For Airborne Collision Avoidance System XU (ACAS XU). ED 275, 1, 176\u2013177."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1417","DOI":"10.1109\/TAP.2018.2884878","article-title":"Design of Platform-Based HF Direction-Finding Antennas Using the Characteristic Mode Theory","volume":"67","author":"Ma","year":"2019","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"793","DOI":"10.1109\/OJAP.2021.3095223","article-title":"Performance-Enhancement of Platform-Based, HF Direction-Finding Systems Using Dynamic Mode Selection","volume":"2","author":"Ren","year":"2021","journal-title":"IEEE Open J. Antennas Propag."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1298","DOI":"10.1109\/TAP.2021.3111311","article-title":"A Spatially Confined, Platform-Based HF Direction Finding Array","volume":"70","author":"Ma","year":"2022","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"7146","DOI":"10.1109\/TAP.2023.3291424","article-title":"Evaluation Method and Design Guidance for Direction-Finding Antenna Systems","volume":"71","author":"Grundmann","year":"2023","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_41","unstructured":"The European Organisation for Civil Aciation Equipment (2008). Minimum Operational Performance Specification for Secondary Surveilance Radar Mode S Transponders. ED-73C, 1, 28."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"276","DOI":"10.1109\/TAP.1986.1143830","article-title":"Multiple Emitter Location and Signal Parameter Estimation","volume":"34","author":"Schmidt","year":"1986","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"2549","DOI":"10.1109\/78.324722","article-title":"Wavefield Modeling and Array Processing, I. Spatial Sampling","volume":"42","author":"Doron","year":"1994","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"2560","DOI":"10.1109\/78.324723","article-title":"Wavefield Modeling and Array Processing, II. Algorithms","volume":"42","author":"Doron","year":"1994","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"2571","DOI":"10.1109\/78.324724","article-title":"Wavefield Modeling and Array Processing, III. Resolution Capacity","volume":"42","author":"Doron","year":"1994","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_46","unstructured":"Kay, S.M. (1993). Fundamentals of Statistical Signal Processing\u2014Estimation Theory, Prentice Hall."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"720","DOI":"10.1109\/29.17564","article-title":"MUSIC, Maximum Likelihood, and Cramer-Rao Bound","volume":"37","author":"Stoica","year":"1989","journal-title":"IEEE Trans. Acoust. Speech Signal Process."},{"key":"ref_48","unstructured":"Ettus (2024, May 22). USRP N310 Datasheet. Available online: https:\/\/www.ettus.com\/wp-content\/uploads\/2019\/01\/USRP_N310_Datasheet_v3.pdf."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Marinho, D., Arruela, R., Varum, T., and Matos, J. (2020). Software-Defined Radio Beamforming System for 5G\/Radar Applications. Appl. Sci., 10.","DOI":"10.3390\/app10207187"},{"key":"ref_50","unstructured":"Jaffer, A. (1988, January 11\u201314). Maximum Likelihood Direction Finding of Stochastic Sources: A Separable Solution. Proceedings of the ICASSP-88, International Conference on Acoustics, Speech, and Signal Processing, New York, NY, USA."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"1295","DOI":"10.1109\/JSTSP.2021.3113120","article-title":"An Overview of Signal Processing Techniques for Joint Communication and Radar Sensing","volume":"15","author":"Zhang","year":"2021","journal-title":"IEEE J. Sel. Top. Signal Process."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"306","DOI":"10.1109\/COMST.2021.3122519","article-title":"Enabling Joint Communication and Radar Sensing in Mobile Networks\u2014 A Survey","volume":"24","author":"Zhang","year":"2021","journal-title":"IEEE Commun. Surv. Tutor."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"30845","DOI":"10.1109\/ACCESS.2021.3059488","article-title":"Joint Design of Communication and Sensing for Beyond 5G and 6G Systems","volume":"9","author":"Wild","year":"2021","journal-title":"IEEE Access"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/11\/3452\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T14:48:55Z","timestamp":1760107735000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/11\/3452"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,5,27]]},"references-count":53,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2024,6]]}},"alternative-id":["s24113452"],"URL":"https:\/\/doi.org\/10.3390\/s24113452","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,5,27]]}}}