Pub Date : 2025-02-04DOI: 10.1109/OJAP.2025.3538797
Margaux Bruliard;Marcello Zucchi;Giuseppe Vecchi
The Impedance Boundary Condition (IBC) is a homogenization approximation of great importance, especially in the design of metasurfaces. However, the standard Electric-Field Integral-Equation formulation of the IBC boundary-value problem (EFIE-IBC) has been shown to lead to numerical instabilities for some impedance ranges of practical interest, in particular inductive reactances. This contribution shows that the numerical instabilities are due to an intrinsic ill-conditioning of the EFIE-IBC operator for the concerned surface impedance values, that can degenerate into an ill-posedness that does not allow for definite solution. Hence, the stable discretization of the EFIE-IBC operator requires a regularization. The analysis leads to a proposed regularization by systematically limiting the wavenumber spectrum of the basis functions, which amounts to a spatial filtering. This is implemented using entire-domain basis functions. Given the possible ill-posedness, we devise two “ground truth” test examples starting from a physical metasurface, then approximated via IBC. Comparison to ground truth results shows that the standard EFIE-IBC may lead to significant errors, and that these may be challenging to detect. Conversely, the regularized system yields stable results that well match the ground truth of the physical structure of which the IBC is an approximation.
{"title":"Stability Analysis of the EFIE-IBC Formulation and Regularization via Spatial Filtering","authors":"Margaux Bruliard;Marcello Zucchi;Giuseppe Vecchi","doi":"10.1109/OJAP.2025.3538797","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3538797","url":null,"abstract":"The Impedance Boundary Condition (IBC) is a homogenization approximation of great importance, especially in the design of metasurfaces. However, the standard Electric-Field Integral-Equation formulation of the IBC boundary-value problem (EFIE-IBC) has been shown to lead to numerical instabilities for some impedance ranges of practical interest, in particular inductive reactances. This contribution shows that the numerical instabilities are due to an intrinsic ill-conditioning of the EFIE-IBC operator for the concerned surface impedance values, that can degenerate into an ill-posedness that does not allow for definite solution. Hence, the stable discretization of the EFIE-IBC operator requires a regularization. The analysis leads to a proposed regularization by systematically limiting the wavenumber spectrum of the basis functions, which amounts to a spatial filtering. This is implemented using entire-domain basis functions. Given the possible ill-posedness, we devise two “ground truth” test examples starting from a physical metasurface, then approximated via IBC. Comparison to ground truth results shows that the standard EFIE-IBC may lead to significant errors, and that these may be challenging to detect. Conversely, the regularized system yields stable results that well match the ground truth of the physical structure of which the IBC is an approximation.","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 2","pages":"578-593"},"PeriodicalIF":3.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10870329","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to ensure high-resolution angle estimation results, antenna apertures of radar sensors become large relative to the wavelength. To prevent high sidelobe levels, the number of antennas is constantly increased, generally through the employment of multiple-input multiple-output operation. As systems become larger relative to the wavelength, influences of near-field effects in calibration measurements become more critical. To achieve precise calibrations despite near-field effects, calibration algorithms must be developed further. This paper proposes the deployment of sub-apertures to avoid near-field effects and to reduce the calibration effort, which is in this work related to the number of measuring points in the calibration measurement. An algorithm to create beneficial sub-apertures from a large array based on clustering is described. This allows the far-field distance to be reduced, as well as the effort required for state-of-the-art calibration methods, which depends on the aperture size. The trade-off between the benefits and error propagations as well as other limitations by the deployment of an increasing number of sub-apertures is demonstrated by simulations and measurements. Exemplary measurements show that even for large arrays in compact measuring chambers, far-field like conditions can be created. Finally, it is exemplarily demonstrated that the measurement effort is decreased by nearly 93 percent compared to a conventional calibration approach.
{"title":"A Sub-Aperture-Based Calibration Algorithm for MIMO Antenna Arrays","authors":"Matthias Linder;Daniel Schmidt;Dominik Schwarz;Nico Riese;Christian Waldschmidt","doi":"10.1109/OJAP.2025.3537681","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3537681","url":null,"abstract":"In order to ensure high-resolution angle estimation results, antenna apertures of radar sensors become large relative to the wavelength. To prevent high sidelobe levels, the number of antennas is constantly increased, generally through the employment of multiple-input multiple-output operation. As systems become larger relative to the wavelength, influences of near-field effects in calibration measurements become more critical. To achieve precise calibrations despite near-field effects, calibration algorithms must be developed further. This paper proposes the deployment of sub-apertures to avoid near-field effects and to reduce the calibration effort, which is in this work related to the number of measuring points in the calibration measurement. An algorithm to create beneficial sub-apertures from a large array based on clustering is described. This allows the far-field distance to be reduced, as well as the effort required for state-of-the-art calibration methods, which depends on the aperture size. The trade-off between the benefits and error propagations as well as other limitations by the deployment of an increasing number of sub-apertures is demonstrated by simulations and measurements. Exemplary measurements show that even for large arrays in compact measuring chambers, far-field like conditions can be created. Finally, it is exemplarily demonstrated that the measurement effort is decreased by nearly 93 percent compared to a conventional calibration approach.","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 2","pages":"548-559"},"PeriodicalIF":3.5,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10869335","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-29DOI: 10.1109/OJAP.2025.3526037
{"title":"IEEE ANTENNAS AND PROPAGATION SOCIETY","authors":"","doi":"10.1109/OJAP.2025.3526037","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3526037","url":null,"abstract":"","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 1","pages":"C2-C2"},"PeriodicalIF":3.5,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10857667","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143107005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-29DOI: 10.1109/OJAP.2025.3526041
{"title":"IEEE Open Journal of Antennas and Propagation Instructions for authors","authors":"","doi":"10.1109/OJAP.2025.3526041","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3526041","url":null,"abstract":"","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 1","pages":"C3-C3"},"PeriodicalIF":3.5,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10857666","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-29DOI: 10.1109/OJAP.2025.3527823
{"title":"IEEE Open Journal of Antennas and Propagation List of Reviewers, Volume 5","authors":"","doi":"10.1109/OJAP.2025.3527823","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3527823","url":null,"abstract":"","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 1","pages":"344-346"},"PeriodicalIF":3.5,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10857600","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143106980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-29DOI: 10.1109/OJAP.2025.3529305
Zhongxiang Shen
{"title":"Editorial Status Update of OJAP","authors":"Zhongxiang Shen","doi":"10.1109/OJAP.2025.3529305","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3529305","url":null,"abstract":"","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 1","pages":"4-5"},"PeriodicalIF":3.5,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10857671","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143107122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-27DOI: 10.1109/OJAP.2025.3534860
Chechia Kang;Xin Du;Jun-Ichi Takada
The broad bandwidth availability of the sub-Terahertz band enables the next generation of mobile communication systems. Since the high-gain antennas are used to compensate for the severe propagation loss, the communication link depends on the line-of-sight (LoS) channel and suffers from a deep fading when the LoS is shadowed by small objects. This paper proposes a method that estimates the diffraction paths from a complex human body as the ones from the cross-section of the human body. The extracted diffraction paths are used for the uniform theory of diffraction (UTD) simulation. The proposal was evaluated by an indoor measurement (3.3 m) of the human body shadowing channel and a simulation based on the modified edge representation and equivalent edge currents (MER-EECs) method. The proposal was found four times more accurate than the conventional point cloud (PC)-based vertical screen model and available for predicting the Doppler frequencies with complex human motions.
{"title":"Point Cloud-Based Diffraction Path Extraction for Dynamic Human Body Shadowing Channel at 300 GHz","authors":"Chechia Kang;Xin Du;Jun-Ichi Takada","doi":"10.1109/OJAP.2025.3534860","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3534860","url":null,"abstract":"The broad bandwidth availability of the sub-Terahertz band enables the next generation of mobile communication systems. Since the high-gain antennas are used to compensate for the severe propagation loss, the communication link depends on the line-of-sight (LoS) channel and suffers from a deep fading when the LoS is shadowed by small objects. This paper proposes a method that estimates the diffraction paths from a complex human body as the ones from the cross-section of the human body. The extracted diffraction paths are used for the uniform theory of diffraction (UTD) simulation. The proposal was evaluated by an indoor measurement (3.3 m) of the human body shadowing channel and a simulation based on the modified edge representation and equivalent edge currents (MER-EECs) method. The proposal was found four times more accurate than the conventional point cloud (PC)-based vertical screen model and available for predicting the Doppler frequencies with complex human motions.","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 2","pages":"535-547"},"PeriodicalIF":3.5,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10855529","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Deep learning-based inversion methods show great promise. The most common way to develop deep learning inversion techniques is to use synthetic (i.e., computationally-generated) data for training and initial testing. Later, the method can be used to image calibrated experimental data. However, it may be better to use experimental data in the training (not just testing) of these networks. In this paper, we (1) present a publicly available large-scale experimental dataset with 1638 measurements of 5 targets in a near-field imaging system that can be used for testing such deep learning inversion methods. A calibration MATLAB script is provided to assist users in processing and calibrating the dataset. (2) Using this dataset, we show that training a data-to-image deep learning-based inversion algorithm on either experimental data alone, or a mixture of experimental and synthetic data, leads to improved experimental imaging results for this data. The deep learning-based approaches are also compared against the gradient descent-based Multiplicative-Regularized Contrast Source Inversion Method.
{"title":"Improved Deep Learning-Based Microwave Inversion With Experimental Training Data","authors":"Seth Cathers;Ben Martin;Noah Stieler;Ian Jeffrey;Colin Gilmore","doi":"10.1109/OJAP.2025.3533373","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3533373","url":null,"abstract":"Deep learning-based inversion methods show great promise. The most common way to develop deep learning inversion techniques is to use synthetic (i.e., computationally-generated) data for training and initial testing. Later, the method can be used to image calibrated experimental data. However, it may be better to use experimental data in the training (not just testing) of these networks. In this paper, we (1) present a publicly available large-scale experimental dataset with 1638 measurements of 5 targets in a near-field imaging system that can be used for testing such deep learning inversion methods. A calibration MATLAB script is provided to assist users in processing and calibrating the dataset. (2) Using this dataset, we show that training a data-to-image deep learning-based inversion algorithm on either experimental data alone, or a mixture of experimental and synthetic data, leads to improved experimental imaging results for this data. The deep learning-based approaches are also compared against the gradient descent-based Multiplicative-Regularized Contrast Source Inversion Method.","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 2","pages":"522-534"},"PeriodicalIF":3.5,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10851335","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-22DOI: 10.1109/OJAP.2025.3532855
Yuying Li;Zhaoran Chen;Kaiyan Huang;Xiayuan Yao
The Orthomode Transducer (OMT) is a widely used device in satellite communication systems, and the T-junction OMT is always a candidate for volume saving. In this study, a design of an OMT loaded with a polarization grid is proposed, based on the traditional T-junction OMT structure. Additionally, a conical horn is integrated into the presented OMT. The entire system was subjected to simulation, fabrication, and measurement. In 29.8–32.2 GHz, both the simulated and tested Voltage Standing Wave Ratio (VSWR) values for the two orthogonal ports remain below 1.2, with a measured isolation of 60–75 dB. At 31 GHz, there is a good agreement between the simulated and measured far-field patterns for the main polarization, with cross polarization levels measured at less than −15 dB. These results from both simulation and measurement validate the effectiveness of the design approach, which not only improves the isolation levels compared to the traditional T-junction OMT but also simplified the OMT’s matching design.
{"title":"A Design of Orthomode Transducer Loaded With Polarization Grid","authors":"Yuying Li;Zhaoran Chen;Kaiyan Huang;Xiayuan Yao","doi":"10.1109/OJAP.2025.3532855","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3532855","url":null,"abstract":"The Orthomode Transducer (OMT) is a widely used device in satellite communication systems, and the T-junction OMT is always a candidate for volume saving. In this study, a design of an OMT loaded with a polarization grid is proposed, based on the traditional T-junction OMT structure. Additionally, a conical horn is integrated into the presented OMT. The entire system was subjected to simulation, fabrication, and measurement. In 29.8–32.2 GHz, both the simulated and tested Voltage Standing Wave Ratio (VSWR) values for the two orthogonal ports remain below 1.2, with a measured isolation of 60–75 dB. At 31 GHz, there is a good agreement between the simulated and measured far-field patterns for the main polarization, with cross polarization levels measured at less than −15 dB. These results from both simulation and measurement validate the effectiveness of the design approach, which not only improves the isolation levels compared to the traditional T-junction OMT but also simplified the OMT’s matching design.","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 2","pages":"513-521"},"PeriodicalIF":3.5,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10849665","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-16DOI: 10.1109/OJAP.2025.3530251
Christos Exadaktylos;Anastasios G. Koutinos;Constantinos L. Zekios;Stavros V. Georgakopoulos
This work introduces a novel design methodology to redesign traditional reflectarray antennas (RAs) with bandwidths in the order of 15% and double their bandwidth without increasing their design complexity. A wideband RA unit cell (UC) is designed utilizing multiple connection points between the radiating and phase shifting structure. Notably, to properly set the desired phase shift at each UC of the RA aperture across the entire frequency band, true-time-delay (TTD) lines are connected to each element. To validate the performance of our proposed approach a traditional microstrip patch-based RA is used as an example. By applying our proposed method to this RA, we develop a design that achieves a fractional 1.5 dB gain bandwidth of 31% (8.6 GHz to 11.8 GHz) in the X-band, which is more than two times larger than the 14% fractional bandwidth of the traditional RA design. Our RA is prototyped to validate its performance. The measurements show excellent agreement with simulations thereby validating our proposed methodology.
{"title":"A Design Method to Increase the Bandwidth of Reflectarray Antennas","authors":"Christos Exadaktylos;Anastasios G. Koutinos;Constantinos L. Zekios;Stavros V. Georgakopoulos","doi":"10.1109/OJAP.2025.3530251","DOIUrl":"https://doi.org/10.1109/OJAP.2025.3530251","url":null,"abstract":"This work introduces a novel design methodology to redesign traditional reflectarray antennas (RAs) with bandwidths in the order of 15% and double their bandwidth without increasing their design complexity. A wideband RA unit cell (UC) is designed utilizing multiple connection points between the radiating and phase shifting structure. Notably, to properly set the desired phase shift at each UC of the RA aperture across the entire frequency band, true-time-delay (TTD) lines are connected to each element. To validate the performance of our proposed approach a traditional microstrip patch-based RA is used as an example. By applying our proposed method to this RA, we develop a design that achieves a fractional 1.5 dB gain bandwidth of 31% (8.6 GHz to 11.8 GHz) in the X-band, which is more than two times larger than the 14% fractional bandwidth of the traditional RA design. Our RA is prototyped to validate its performance. The measurements show excellent agreement with simulations thereby validating our proposed methodology.","PeriodicalId":34267,"journal":{"name":"IEEE Open Journal of Antennas and Propagation","volume":"6 2","pages":"497-512"},"PeriodicalIF":3.5,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10843377","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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