Deriving the precise true height electron density profile from the measured ionosonde virtual heights is quite a challenging problem. Recently, Ankita and Tulasi Ram (2023, https://doi.org/10.1029/2023RS007808) presented a new method, Iterative Gradient Correction (IGC) method, for true height analysis that uses HF radio wave propagation path computations to reconstruct the true height profile. Through iterative corrections on electron density gradients between successive points, the IGC method minimizes errors below a specified tolerance at each point and reconstructs a complete electron density profile. The derived profiles from the IGC method are found to be accurate when compared with Incoherent Scatter Radar and Global Navigation Satellite System—Radio Occultation observations. To facilitate true height analysis by IGC method for a wider user community, a MATLAB-based software has been developed and is outlined in this report. The software can be installed on any Windows platform and is designed with a user-friendly interface for easy and efficient application by the users. It can analyze multiple scaled ionograms in a single run and outputs the real height profiles in ASCII format. Further, the software also captures important ionospheric parameters such as the base altitudes and peak frequencies of E- and F-layers (e.g., hE, hF, foE, and foF2) etc., from the computed true height profiles and tabulates in a separate output file for the ready use. The software also provides the option for extrapolation of true height profile into top-side ionosphere up to a user-specified height and reconstructs the complete vertical electron density profile.
从测量的电离层探测仪虚拟高度得出精确的真实高度电子密度剖面是一个相当具有挑战性的问题。最近，Ankita 和 Tulasi Ram（2023，https://doi.org/10.1029/2023RS007808）提出了一种用于真实高度分析的新方法--迭代梯度校正法（IGC），该方法利用高频无线电波传播路径计算来重建真实高度剖面。通过对连续点之间的电子密度梯度进行迭代修正，IGC 方法可将每个点的误差降至指定容差以下，并重建完整的电子密度剖面。与相干散射雷达和全球导航卫星系统无线电掩星观测结果相比，IGC 方法得出的剖面图非常准确。为了方便更多用户使用 IGC 方法进行真实高度分析，我们开发了一个基于 MATLAB 的软件，本报告对此进行了概述。该软件可安装在任何视窗平台上，界面设计友好，便于用户高效应用。它可以在一次运行中分析多个缩放离子图，并以 ASCII 格式输出实际高度剖面图。此外，该软件还能从计算出的真实高度剖面图中捕获重要的电离层参数，如 E 层和 F 层的基底高度和峰值频率（如 hE、hF、foE 和 foF2）等，并将其制成表格，存入单独的输出文件中，以备随时使用。该软件还可将真实高度剖面外推至用户指定高度的顶部电离层，并重建完整的垂直电子密度剖面。
{"title":"A software tool for the true height analysis of ionograms using the iterative gradient correction (IGC) method","authors":"M. Ankita;S. Tulasi Ram","doi":"10.1029/2024RS007955","DOIUrl":"https://doi.org/10.1029/2024RS007955","url":null,"abstract":"Deriving the precise true height electron density profile from the measured ionosonde virtual heights is quite a challenging problem. Recently, Ankita and Tulasi Ram (2023, https://doi.org/10.1029/2023RS007808) presented a new method, Iterative Gradient Correction (IGC) method, for true height analysis that uses HF radio wave propagation path computations to reconstruct the true height profile. Through iterative corrections on electron density gradients between successive points, the IGC method minimizes errors below a specified tolerance at each point and reconstructs a complete electron density profile. The derived profiles from the IGC method are found to be accurate when compared with Incoherent Scatter Radar and Global Navigation Satellite System—Radio Occultation observations. To facilitate true height analysis by IGC method for a wider user community, a MATLAB-based software has been developed and is outlined in this report. The software can be installed on any Windows platform and is designed with a user-friendly interface for easy and efficient application by the users. It can analyze multiple scaled ionograms in a single run and outputs the real height profiles in ASCII format. Further, the software also captures important ionospheric parameters such as the base altitudes and peak frequencies of E- and F-layers (e.g., hE, hF, foE, and foF2) etc., from the computed true height profiles and tabulates in a separate output file for the ready use. The software also provides the option for extrapolation of true height profile into top-side ionosphere up to a user-specified height and reconstructs the complete vertical electron density profile.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 10","pages":"1-10"},"PeriodicalIF":1.6,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qi Song;Feng-Gang Yan;Xiang-Tian Meng;Bing-Xia Cao;Ming Jin
In this paper, we utilize the original noise subspace and its conjugate to reconstruct a new estimator for the fast joint estimation of DOA and inter-subarray errors in the partly calibrated arrays (PCA), namely fast-rank-reduce (F-RARE). Based on the new estimator, the collection of true DOA estimation and its virtual mirror can be obtained by searching over only half of the total angular field-of-view. Then, the true DOA estimation can be selected by using the conventional beamforming (CBF) technique. Additionally, the inter-subarray errors can also be computed by a finite number of subspace decompositions. Numerical simulation illustrates that compared with the conventional RARE algorithm, the new method can not only reduce the computational burden by a half but also provide a similar estimation accuracy.
在本文中，我们利用原始噪声子空间及其共轭重构了一种新的估计器，用于快速联合估计部分校准阵列（PCA）中的 DOA 和子阵间误差，即快速rank-reduce（F-RARE）。基于新的估计器，只需搜索总视场角的一半，就能获得真实 DOA 估计及其虚拟镜像的集合。然后，就可以利用传统波束成形（CBF）技术选择真正的 DOA 估计值。此外，子阵列间误差也可以通过有限数量的子空间分解来计算。数值模拟表明，与传统的 RARE 算法相比，新方法不仅能减少一半的计算负担，还能提供类似的估计精度。
{"title":"Fast joint DOA and inter-subarray errors estimation in partly calibrated arrays","authors":"Qi Song;Feng-Gang Yan;Xiang-Tian Meng;Bing-Xia Cao;Ming Jin","doi":"10.1029/2024RS008061","DOIUrl":"https://doi.org/10.1029/2024RS008061","url":null,"abstract":"In this paper, we utilize the original noise subspace and its conjugate to reconstruct a new estimator for the fast joint estimation of DOA and inter-subarray errors in the partly calibrated arrays (PCA), namely fast-rank-reduce (F-RARE). Based on the new estimator, the collection of true DOA estimation and its virtual mirror can be obtained by searching over only half of the total angular field-of-view. Then, the true DOA estimation can be selected by using the conventional beamforming (CBF) technique. Additionally, the inter-subarray errors can also be computed by a finite number of subspace decompositions. Numerical simulation illustrates that compared with the conventional RARE algorithm, the new method can not only reduce the computational burden by a half but also provide a similar estimation accuracy.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 10","pages":"1-12"},"PeriodicalIF":1.6,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A newly conceived microstrip element, that features adequately suppressed cross-polar discrimination (XPD) over both the orthogonal (H-) and diagonal (D-) planes, has been explored here. The proposed patch is of rectangular shape with a pair of loading at its corner region. A standalone patch as well as its linear and square array formation has been investigated. Their design and characterization along with a partial experimental verification are presented. They promise considerable improvement in D-plane XPD, around 6 dB for single element, 10 dB for four-element linear and 5 dB for four-element square sub-arrays. The XPD performance over H-plane is equally promising, 8 dB for single element (10-18) dB for both planar and square arrays. The overall 3D-XP scenario thus gets improved by about (8-10) dB on average which is quite significant in the case of arrays.
{"title":"Rectangular microstrip with co-planar corner loading: advanced antenna and array design for high cross-polar isolation across all radiation planes","authors":"D. Dutta;D. Guha;C. Kumar","doi":"10.1029/2024RS008027","DOIUrl":"https://doi.org/10.1029/2024RS008027","url":null,"abstract":"A newly conceived microstrip element, that features adequately suppressed cross-polar discrimination (XPD) over both the orthogonal (H-) and diagonal (D-) planes, has been explored here. The proposed patch is of rectangular shape with a pair of loading at its corner region. A standalone patch as well as its linear and square array formation has been investigated. Their design and characterization along with a partial experimental verification are presented. They promise considerable improvement in D-plane XPD, around 6 dB for single element, 10 dB for four-element linear and 5 dB for four-element square sub-arrays. The XPD performance over H-plane is equally promising, 8 dB for single element (10-18) dB for both planar and square arrays. The overall 3D-XP scenario thus gets improved by about (8-10) dB on average which is quite significant in the case of arrays.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 10","pages":"1-10"},"PeriodicalIF":1.6,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qi Jiang;Jiuhou Lei;Xinan Yue;Dexin Ren;Fuqing Huang;Xiaoli Luan;Guozhu Li
The ionosonde is widely used for detecting electron density profiles below the F2 peak altitude. Extracting precise profiles from ionograms is crucial, as it serves as a significant data source for ionospheric studies and applications. In our study, we utilized the ray tracing profile inversion method (RTPI) to derive more realistic electron density profiles from the ionosonde observations. By comparing the electron density profiles inverted by RTPI method with and without geomagnetic field against the profiles observed by Incoherent Scatter Radar (ISR) plasma lines, we validated the high precision of the RTPI with magnetic field effect method. The results showed that the average height difference and average peak height difference between profiles inverted by RTPI and plasma line observations are less than 10 and 5 km, respectively. Additionally, we quantified the errors associated with the geomagnetic field effect. It would cause an ~8—10 km overestimation in true height and a ~ 10%—15% underestimation in electron density if the geomagnetic field effect is not considered. These errors induced by the magnetic field accumulate with the frequency of the radio waves. Moreover, we conducted a comparative analysis of simulated echo traces using profiles with different E-layer shapes. It was demonstrated that the key parameters of the bottom structure have a significant impact on ionogram retrieval, while the E-layer shape has negligible influence on inversion. Furthermore, we analyzed echo traces simulated using ray tracing with and without collision. The collision effect has weak effect on the delay of the radio waves.
电离层探测仪广泛用于探测 F2 峰值高度以下的电子密度剖面。从电离图中提取精确的剖面图至关重要，因为它是电离层研究和应用的重要数据源。在我们的研究中，我们利用射线追踪剖面反演法（RTPI）从电离层探测仪的观测数据中得出更真实的电子密度剖面。通过将 RTPI 方法反演的有地磁场和无地磁场的电子密度剖面与非相干散射雷达（ISR）等离子体线观测到的剖面进行比较，我们验证了带磁场效应方法的 RTPI 的高精度。结果表明，用 RTPI 反演的剖面与等离子体线观测的剖面之间的平均高度差和平均峰高差分别小于 10 公里和 5 公里。此外，我们还量化了与地磁场效应相关的误差。如果不考虑地磁场效应，真实高度会被高估约8-10千米，电子密度会被低估约10%-15%。这些由磁场引起的误差会随着无线电波频率的增加而累积。此外，我们还利用不同 E 层形状的剖面对模拟回波轨迹进行了比较分析。结果表明，海底结构的关键参数对电离图检索有重大影响，而 E 层形状对反演的影响可以忽略不计。此外，我们还分析了利用射线追踪模拟的有碰撞和无碰撞的回波轨迹。碰撞效应对无线电波延迟的影响较弱。
{"title":"Electron density profile derived from ionogram using ray tracing inversion method","authors":"Qi Jiang;Jiuhou Lei;Xinan Yue;Dexin Ren;Fuqing Huang;Xiaoli Luan;Guozhu Li","doi":"10.1029/2024RS008086","DOIUrl":"https://doi.org/10.1029/2024RS008086","url":null,"abstract":"The ionosonde is widely used for detecting electron density profiles below the F2 peak altitude. Extracting precise profiles from ionograms is crucial, as it serves as a significant data source for ionospheric studies and applications. In our study, we utilized the ray tracing profile inversion method (RTPI) to derive more realistic electron density profiles from the ionosonde observations. By comparing the electron density profiles inverted by RTPI method with and without geomagnetic field against the profiles observed by Incoherent Scatter Radar (ISR) plasma lines, we validated the high precision of the RTPI with magnetic field effect method. The results showed that the average height difference and average peak height difference between profiles inverted by RTPI and plasma line observations are less than 10 and 5 km, respectively. Additionally, we quantified the errors associated with the geomagnetic field effect. It would cause an ~8—10 km overestimation in true height and a ~ 10%—15% underestimation in electron density if the geomagnetic field effect is not considered. These errors induced by the magnetic field accumulate with the frequency of the radio waves. Moreover, we conducted a comparative analysis of simulated echo traces using profiles with different E-layer shapes. It was demonstrated that the key parameters of the bottom structure have a significant impact on ionogram retrieval, while the E-layer shape has negligible influence on inversion. Furthermore, we analyzed echo traces simulated using ray tracing with and without collision. The collision effect has weak effect on the delay of the radio waves.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 10","pages":"1-13"},"PeriodicalIF":1.6,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding ionospheric irregularities and their dynamics is crucial, with the rate of change of the total electron content index (ROTI) serving as a significant metric for this purpose. However, inconsistencies in ROTI magnitudes have been noted when sampled at one-second interval across various Global Navigation Satellite System (GNSS) receivers. This study presents a detailed statistical analysis to investigate inconsistencies in ROTI using multi-GNSS observations in conjunction with four distinct GNSS receiver types. Various factors affecting the ROTI inconsistencies among receivers were examined, including differences in sampling rates (1, 5, 15, and 30 s), and varying time window widths (1, 2, and 5 min). By examination of data obtained from GNSS receivers with zero or short baselines on a global scale, the analysis uncovered substantial variations in multi-GNSS ROTI values across the four assessed receiver types. The main findings suggest that reducing the sampling rate reduces the inconsistencies in the magnitude of ROTI, particularly at lower sampling rates. This reduction can be attributed to the exclusion of high-frequency components in the ROTI spectrum. Interestingly, the width of the time window is found to have minimal impact on the ROTI magnitude. The study also shows a direct correlation between a larger magnitude of ROTI and the increased noise in the signals tracked by receivers. These results emphasize the importance of considering sampling rates and GNSS receiver types when utilizing ROTI to investigate ionospheric irregularities.
{"title":"Revealing inconsistencies in ROTI index using multi-GNSS constellation measurements: impact of sampling rates and time window","authors":"Yi Sui;Zhe Yang;Weijia Zhan","doi":"10.1029/2024RS007982","DOIUrl":"https://doi.org/10.1029/2024RS007982","url":null,"abstract":"Understanding ionospheric irregularities and their dynamics is crucial, with the rate of change of the total electron content index (ROTI) serving as a significant metric for this purpose. However, inconsistencies in ROTI magnitudes have been noted when sampled at one-second interval across various Global Navigation Satellite System (GNSS) receivers. This study presents a detailed statistical analysis to investigate inconsistencies in ROTI using multi-GNSS observations in conjunction with four distinct GNSS receiver types. Various factors affecting the ROTI inconsistencies among receivers were examined, including differences in sampling rates (1, 5, 15, and 30 s), and varying time window widths (1, 2, and 5 min). By examination of data obtained from GNSS receivers with zero or short baselines on a global scale, the analysis uncovered substantial variations in multi-GNSS ROTI values across the four assessed receiver types. The main findings suggest that reducing the sampling rate reduces the inconsistencies in the magnitude of ROTI, particularly at lower sampling rates. This reduction can be attributed to the exclusion of high-frequency components in the ROTI spectrum. Interestingly, the width of the time window is found to have minimal impact on the ROTI magnitude. The study also shows a direct correlation between a larger magnitude of ROTI and the increased noise in the signals tracked by receivers. These results emphasize the importance of considering sampling rates and GNSS receiver types when utilizing ROTI to investigate ionospheric irregularities.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 10","pages":"1-18"},"PeriodicalIF":1.6,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work describes the instrumental error budget for space-based measurements of the absolute flux of the sky synchrotron spectrum at frequencies below the ionospheric cutoff (≤20 MHz). We focus on an architecture using electrically short dipoles onboard a small satellite. The error budget combines the contributions of the dipole dimensions, plasma noise, stray capacitance, and front-end amplifier input impedance. We treat the errors using both a Monte Carlo error propagation model and an analytical method. This error budget can be applied to a variety of experiments and used to ultimately improve the sensing capabilities of space-based electrically short dipole instruments. The impact of individual uncertainty components, particularly stray capacitance, is explored in more detail.
{"title":"An instrument error budget for space-based absolute flux measurements of the sky synchrotron spectrum below 20 MHz","authors":"J. Rolla;A. Romero-Wolf;T. J. W. Lazio","doi":"10.1029/2023RS007824","DOIUrl":"https://doi.org/10.1029/2023RS007824","url":null,"abstract":"This work describes the instrumental error budget for space-based measurements of the absolute flux of the sky synchrotron spectrum at frequencies below the ionospheric cutoff (≤20 MHz). We focus on an architecture using electrically short dipoles onboard a small satellite. The error budget combines the contributions of the dipole dimensions, plasma noise, stray capacitance, and front-end amplifier input impedance. We treat the errors using both a Monte Carlo error propagation model and an analytical method. This error budget can be applied to a variety of experiments and used to ultimately improve the sensing capabilities of space-based electrically short dipole instruments. The impact of individual uncertainty components, particularly stray capacitance, is explored in more detail.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 9","pages":"1-23"},"PeriodicalIF":1.6,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142377077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The growing demand for advanced wireless communication, high-resolution imaging, and innovative medical applications in the Terahertz (THz) frequency range has driven remarkable developments in meta-surface-based antennas. This comprehensive review delves into the cutting-edge advancements, novel designs, and practical applications of meta-surfaces in the THz spectrum. The review begins by exploring the materials employed in meta-surfaces and their crucial role in achieving efficient THz operation. It delves into the realm of polarization diversity, revealing innovative approaches to harnessing the potential of meta-surfaces for polarization control and conversion. A key area of focus is beam-steering technology, with a thorough investigation into beam-steering techniques that have significant implications for enhancing wireless communication, high-resolution imaging, and the internet of things. The paper highlights the potential of these techniques in addressing real-world challenges and advancing THz technology. Furthermore, this review provides an in-depth examination of the innovative antenna designs tailored for THz applications, shedding light on their characteristics and benefits. It also explores the exciting possibilities of THz technology within the medical field, including precise bio sensing and cancer cell detection.
{"title":"A systematic review of meta-surface based antennas for Thz applications","authors":"Nipun Sharma;Amrit Kaur","doi":"10.1029/2024RS007980","DOIUrl":"https://doi.org/10.1029/2024RS007980","url":null,"abstract":"The growing demand for advanced wireless communication, high-resolution imaging, and innovative medical applications in the Terahertz (THz) frequency range has driven remarkable developments in meta-surface-based antennas. This comprehensive review delves into the cutting-edge advancements, novel designs, and practical applications of meta-surfaces in the THz spectrum. The review begins by exploring the materials employed in meta-surfaces and their crucial role in achieving efficient THz operation. It delves into the realm of polarization diversity, revealing innovative approaches to harnessing the potential of meta-surfaces for polarization control and conversion. A key area of focus is beam-steering technology, with a thorough investigation into beam-steering techniques that have significant implications for enhancing wireless communication, high-resolution imaging, and the internet of things. The paper highlights the potential of these techniques in addressing real-world challenges and advancing THz technology. Furthermore, this review provides an in-depth examination of the innovative antenna designs tailored for THz applications, shedding light on their characteristics and benefits. It also explores the exciting possibilities of THz technology within the medical field, including precise bio sensing and cancer cell detection.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 9","pages":"1-22"},"PeriodicalIF":1.6,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142377151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Z. Ding;J. Cao;J. Yu;Nasimuddin Nasimuddin;M. Y. Chia;S. Fei;H. Wang
Low-profile miniaturized wideband circularly polarized (CP) monopole and multiple-input-multiple-output (MIMO) antennas using characteristic mode analysis (CMA) are presented. The antennas are constructed with a microstrip feeding line, a slot, and a branch, which positions the transmission line perpendicularly to the branch to achieve CP. The CP characteristic is realized through a characteristic angle (CA) difference of approximately 90° at three mode significance (MS) intersections across four modes. CMA provides both theoretical analysis and design guidance for these antennas. The antennas were fabricated and tested, with dimensions of 0.48λ 0 × 0.48λ 0 × 0.03λ 0 and 0.47λ 0 × 0.47λ 0 × 0.03λ 0 , where λ 0 represents the freespace wavelength. Measurements indicate that the monopole antenna achieves a —10 dB impedance bandwidth (IBW) from 3.2 to 8.4 GHz (89.7% relative bandwidth), a 3 dB axial ratio bandwidth (ARBW) from 3.6 to 5.1 GHz (34.5%), and a peak gain of 6.6 dBic. The MIMO antenna has a —10 dB IBW from 3.1 to 8.2 GHz (90.3%), a 3 dB ARBW from 3.2 to 6 GHz (60.9%), and a peak gain of 5.1 dBic. Both antennas feature a low profile, ultra-wideband IBW, broadband ARBW, and miniaturized design, making them suitable for wideband wireless communication applications.
{"title":"Low-profile miniaturized wideband circularly polarized monopole and MIMO antennas using characteristic mode analysis for wireless communication","authors":"Z. Ding;J. Cao;J. Yu;Nasimuddin Nasimuddin;M. Y. Chia;S. Fei;H. Wang","doi":"10.1029/2024RS008030","DOIUrl":"https://doi.org/10.1029/2024RS008030","url":null,"abstract":"Low-profile miniaturized wideband circularly polarized (CP) monopole and multiple-input-multiple-output (MIMO) antennas using characteristic mode analysis (CMA) are presented. The antennas are constructed with a microstrip feeding line, a slot, and a branch, which positions the transmission line perpendicularly to the branch to achieve CP. The CP characteristic is realized through a characteristic angle (CA) difference of approximately 90° at three mode significance (MS) intersections across four modes. CMA provides both theoretical analysis and design guidance for these antennas. The antennas were fabricated and tested, with dimensions of 0.48λ\u0000<inf>0</inf>\u0000 × 0.48λ\u0000<inf>0</inf>\u0000 × 0.03λ\u0000<inf>0</inf>\u0000 and 0.47λ\u0000<inf>0</inf>\u0000 × 0.47λ\u0000<inf>0</inf>\u0000 × 0.03λ\u0000<inf>0</inf>\u0000, where λ\u0000<inf>0</inf>\u0000 represents the freespace wavelength. Measurements indicate that the monopole antenna achieves a —10 dB impedance bandwidth (IBW) from 3.2 to 8.4 GHz (89.7% relative bandwidth), a 3 dB axial ratio bandwidth (ARBW) from 3.6 to 5.1 GHz (34.5%), and a peak gain of 6.6 dBic. The MIMO antenna has a —10 dB IBW from 3.1 to 8.2 GHz (90.3%), a 3 dB ARBW from 3.2 to 6 GHz (60.9%), and a peak gain of 5.1 dBic. Both antennas feature a low profile, ultra-wideband IBW, broadband ARBW, and miniaturized design, making them suitable for wideband wireless communication applications.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 9","pages":"1-16"},"PeriodicalIF":1.6,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142376783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Global Navigation Satellite System Ionospheric Seismology investigates the ionospheric response to earthquakes and tsunamis. These events are known to generate Traveling Ionospheric Disturbances (TIDs) that can be detected through GNSS-derived Total Electron Content (TEC) observations. Real-time TID identification provides a method for tsunami detection, improving tsunami early warning systems (TEWS) by extending coverage to open-ocean regions where buoy-based warning systems are impractical. Scalable and automated TID detection is, hence, essential for TEWS augmentation. In this work, we present an innovative approach to perform automatic real-time TID monitoring and detection, using deep learning insights. We utilize Gramian Angular Difference Fields (GADFs), a technique that transforms time-series into images, in combination with Convolutional Neural Networks (CNNs), starting from VARION (Variometric Approach for Real-time Ionosphere Observation) real-time TEC estimates. We select four tsunamigenic earthquakes that occurred in the Pacific Ocean: the 2010 Maule earthquake, the 2011 Tohoku earthquake, the 2012 Haida-Gwaii, the 2015 Illapel earthquake. The first three events are used for model training, whereas the out-of-sample validation is performed on the last one. The presented framework, being perfectly suitable for real-time applications, achieves 91.7% of F1 score and 84.6% of recall, highlighting its potential. Our approach to improve false positive detection, based on the likelihood of a TID at each time step, ensures robust and high performance as the system scales up, integrating more data for model training. This research lays the foundation for incorporating deep learning into real-time GNSS-TEC analysis, offering a joint and substantial contribution to TEWS progression.
全球导航卫星系统电离层地震学研究电离层对地震和海啸的反应。众所周知，这些事件会产生移动电离层扰动（TID），可通过源自全球导航卫星系统的电子总含量（TEC）观测加以探测。实时 TID 识别为海啸探测提供了一种方法，通过将覆盖范围扩大到浮标预警系统不可行的公海地区，改进了海啸预警系统（TEWS）。因此，可扩展的自动 TID 检测对于增强 TEWS 至关重要。在这项工作中，我们提出了一种创新方法，利用深度学习的洞察力进行自动实时 TID 监测和检测。我们利用将时间序列转换为图像的技术--格兰角差场（GADFs），结合卷积神经网络（CNNs），从电离层实时观测变异方法（VARION）的实时 TEC 估计值出发。我们选择了四次发生在太平洋的海啸地震：2010 年毛勒地震、2011 年东北地震、2012 年海达-瓜伊岛地震和 2015 年伊利亚佩尔地震。前三个事件用于模型训练，而样本外验证则在最后一个事件上进行。所提出的框架完全适用于实时应用，F1 得分达到 91.7%，召回率达到 84.6%，彰显了其潜力。我们根据每个时间步的 TID 可能性改进误报检测的方法，确保了系统在扩展时的稳健性和高性能，并整合了更多数据用于模型训练。这项研究为将深度学习纳入实时 GNSS-TEC 分析奠定了基础，为 TEWS 的发展做出了重大贡献。
{"title":"Exploring AI progress in GNSS remote sensing: A deep learning based framework for real-time detection of earthquake and tsunami induced ionospheric perturbations","authors":"Michela Ravanelli;Valentino Constantinou;Hamlin Liu;Jacob Bortnik","doi":"10.1029/2024RS008016","DOIUrl":"https://doi.org/10.1029/2024RS008016","url":null,"abstract":"Global Navigation Satellite System Ionospheric Seismology investigates the ionospheric response to earthquakes and tsunamis. These events are known to generate Traveling Ionospheric Disturbances (TIDs) that can be detected through GNSS-derived Total Electron Content (TEC) observations. Real-time TID identification provides a method for tsunami detection, improving tsunami early warning systems (TEWS) by extending coverage to open-ocean regions where buoy-based warning systems are impractical. Scalable and automated TID detection is, hence, essential for TEWS augmentation. In this work, we present an innovative approach to perform automatic real-time TID monitoring and detection, using deep learning insights. We utilize Gramian Angular Difference Fields (GADFs), a technique that transforms time-series into images, in combination with Convolutional Neural Networks (CNNs), starting from VARION (Variometric Approach for Real-time Ionosphere Observation) real-time TEC estimates. We select four tsunamigenic earthquakes that occurred in the Pacific Ocean: the 2010 Maule earthquake, the 2011 Tohoku earthquake, the 2012 Haida-Gwaii, the 2015 Illapel earthquake. The first three events are used for model training, whereas the out-of-sample validation is performed on the last one. The presented framework, being perfectly suitable for real-time applications, achieves 91.7% of F1 score and 84.6% of recall, highlighting its potential. Our approach to improve false positive detection, based on the likelihood of a TID at each time step, ensures robust and high performance as the system scales up, integrating more data for model training. This research lays the foundation for incorporating deep learning into real-time GNSS-TEC analysis, offering a joint and substantial contribution to TEWS progression.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 9","pages":"1-18"},"PeriodicalIF":1.6,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142376782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The measurement of soil moisture is important for many practical applications. We describe the theoretical design of a simple, noncontact, electromagnetic probe that complements many existing soil moisture measurement techniques. The approach uses a low-frequency (i.e., 50–150 MHz) antenna operating in proximity of the soil. The presence of the soil affects the antenna input impedance, which in turn depends on the distance between the soil and antenna and the complex dielectric constant of the soil. The latter strongly depends on the soil wetness, which suggests that bulk soil moisture integrated over a depth of roughly 1 m can be inferred from antenna impedance measurements. This is in contrast with many current higher-frequency techniques that penetrate only a few centimeters into the soil and provide only near-surface values of soil wetness. Our work suggests that under ideal conditions bulk soil moisture can be mapped with an accuracy on the order of 1% over horizontal scales spanning a few tens of meters to a few kilometers using simple low-frequency antennas.
{"title":"A simple noncontact soil moisture probe for weather and climate applications","authors":"A. G. Voronovich;P. E. Johnston;R. J. Lataitis","doi":"10.1029/2023RS007857","DOIUrl":"https://doi.org/10.1029/2023RS007857","url":null,"abstract":"The measurement of soil moisture is important for many practical applications. We describe the theoretical design of a simple, noncontact, electromagnetic probe that complements many existing soil moisture measurement techniques. The approach uses a low-frequency (i.e., 50–150 MHz) antenna operating in proximity of the soil. The presence of the soil affects the antenna input impedance, which in turn depends on the distance between the soil and antenna and the complex dielectric constant of the soil. The latter strongly depends on the soil wetness, which suggests that bulk soil moisture integrated over a depth of roughly 1 m can be inferred from antenna impedance measurements. This is in contrast with many current higher-frequency techniques that penetrate only a few centimeters into the soil and provide only near-surface values of soil wetness. Our work suggests that under ideal conditions bulk soil moisture can be mapped with an accuracy on the order of 1% over horizontal scales spanning a few tens of meters to a few kilometers using simple low-frequency antennas.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 9","pages":"1-11"},"PeriodicalIF":1.6,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142376844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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