Muhammad Fitra Zambak;Safpbri Johari;Mohd Najib Mohd Yassin;Arif Marwardi Ismail;Abdullah Alghaihab
This paper addresses the limited gain of conventional Antipodal Vivaldi Antenna (AVA) at higher frequencies. We propose a novel Metamaterial Lens Vivaldi Antenna (MLVA) design that overcomes this limitation by integrating an exponentially tapered antenna lens and a strategically placed Near Zero Refractive Index (NRZI) metamaterial lattice. The MLVA achieves exceptional wideband performance with a — 3 dB gain bandwidth exceeding 148.6% from 3.7 to 25 GHz. The result demonstrates a peak realized gain of 11.8 dBi at 11.2 GHz, compared to 9.1 dBi conventional AVA, especially beyond 5 GHz. The compact MLVA design measures only 120 × 78 × 1.524 mm 3 (1.48 × 0.96 × 0.0188λ 03 ) λ 0 where free-space wavelength is the lowest frequency and is fabricated on RO4350 B substrate with a 50-Ω SMA connector. Key features of the design include exponential flaring, and trapezoidal lens geometries chosen for their inherent ability to effectively collimate and direct the spherical wavefront. The incorporation of a dielectric lens and metasurface further enhances gain and Front-to-Back Ratio (FBR) by directing the majority of energy in the end-fire direction. Experimental results validate the effectiveness of the proposed design, confirming simulation predictions. These outstanding characteristics make the MLVA a promising candidate for diverse wireless communication and radar applications demanding high data rates across a broad frequency range.
{"title":"Ultra-wide band antipodal vivaldi antenna using metasurface lens for gain and front-to-back ratio (FBR) improvement","authors":"Muhammad Fitra Zambak;Safpbri Johari;Mohd Najib Mohd Yassin;Arif Marwardi Ismail;Abdullah Alghaihab","doi":"10.1029/2024RS008115","DOIUrl":"https://doi.org/10.1029/2024RS008115","url":null,"abstract":"This paper addresses the limited gain of conventional Antipodal Vivaldi Antenna (AVA) at higher frequencies. We propose a novel Metamaterial Lens Vivaldi Antenna (MLVA) design that overcomes this limitation by integrating an exponentially tapered antenna lens and a strategically placed Near Zero Refractive Index (NRZI) metamaterial lattice. The MLVA achieves exceptional wideband performance with a — 3 dB gain bandwidth exceeding 148.6% from 3.7 to 25 GHz. The result demonstrates a peak realized gain of 11.8 dBi at 11.2 GHz, compared to 9.1 dBi conventional AVA, especially beyond 5 GHz. The compact MLVA design measures only 120 × 78 × 1.524 mm\u0000<sup>3</sup>\u0000 (1.48 × 0.96 × 0.0188λ\u0000<inf>0</inf>\u0000<sup>3</sup>\u0000) λ\u0000<inf>0</inf>\u0000 where free-space wavelength is the lowest frequency and is fabricated on RO4350 B substrate with a 50-Ω SMA connector. Key features of the design include exponential flaring, and trapezoidal lens geometries chosen for their inherent ability to effectively collimate and direct the spherical wavefront. The incorporation of a dielectric lens and metasurface further enhances gain and Front-to-Back Ratio (FBR) by directing the majority of energy in the end-fire direction. Experimental results validate the effectiveness of the proposed design, confirming simulation predictions. These outstanding characteristics make the MLVA a promising candidate for diverse wireless communication and radar applications demanding high data rates across a broad frequency range.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 10","pages":"1-15"},"PeriodicalIF":1.6,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595828","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}
In this paper, we present a review and classification of the published works on the use of Electromagnetic Time Reversal (EMTR)-based methods to locate landmines. Different approaches for landmine localization using EMTR are investigated. Specifically, the classical time-domain EMTR, iterative EMTR, EMTR-DORT (Décomposition de l’Opérateur du Retournement Temporel), and EMTR-MUSIC (Multiple SIgnal Classification) are implemented using different numerical techniques. The main properties of the mentioned EMTR-based approaches are reviewed and the TR-MUSIC method is selected as the most promising approach for the problem of interest, among all the reviewed methods. In the TR-MUSIC method, the transfer matrix is calculated in the first step. Then, the singular value decomposition of the transfer matrix is performed. In the last step, the location of the landmines is obtained through the evaluation of the pseudospectrum. As opposed to other EMTR-based techniques, TR-MUSIC features very high resolution (in the order of 1/10 or higher) with a reasonable number of sensors, allowing the detection of multiple closely spaced targets.
在本文中，我们对已发表的有关使用基于电磁时间反演（EMTR）的地雷定位方法的著作进行了综述和分类。本文研究了利用 EMTR 进行地雷定位的不同方法。具体而言，利用不同的数值技术实现了经典时域 EMTR、迭代 EMTR、EMTR-DORT（Décomposition de l'Opérateur du Retournement Temporel）和 EMTR-MUSIC（多重信号分类）。对上述基于 EMTR 的方法的主要特性进行了评述，在所有评述方法中，TR-MUSIC 方法被选为最有希望解决相关问题的方法。在 TR-MUSIC 方法中，第一步是计算转移矩阵。然后，对传递矩阵进行奇异值分解。最后一步，通过评估伪谱获得地雷的位置。与其他基于 EMTR 的技术相比，TR-MUSIC 具有极高的分辨率（1/10 或更高）和合理的传感器数量，可探测多个紧密间隔的目标。
{"title":"Landmine detection using electromagnetic time reversalbased methods: 1. classical TR, iterative TR, DORT and TR-MUSIC","authors":"Hamidreza Karami;André Koch;Carlos Romero;Marcos Rubinstein;Farhad Rachidi","doi":"10.1029/2024RS007971","DOIUrl":"https://doi.org/10.1029/2024RS007971","url":null,"abstract":"In this paper, we present a review and classification of the published works on the use of Electromagnetic Time Reversal (EMTR)-based methods to locate landmines. Different approaches for landmine localization using EMTR are investigated. Specifically, the classical time-domain EMTR, iterative EMTR, EMTR-DORT (Décomposition de l’Opérateur du Retournement Temporel), and EMTR-MUSIC (Multiple SIgnal Classification) are implemented using different numerical techniques. The main properties of the mentioned EMTR-based approaches are reviewed and the TR-MUSIC method is selected as the most promising approach for the problem of interest, among all the reviewed methods. In the TR-MUSIC method, the transfer matrix is calculated in the first step. Then, the singular value decomposition of the transfer matrix is performed. In the last step, the location of the landmines is obtained through the evaluation of the pseudospectrum. As opposed to other EMTR-based techniques, TR-MUSIC features very high resolution (in the order of 1/10 or higher) with a reasonable number of sensors, allowing the detection of multiple closely spaced targets.","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":"142595779","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}
Stochastic analysis of the absorbed power density (APD) on skin surface exposed to radiation of halfwave dipole at 10, 30 and 90 GHz and for different antenna-body distances is presented. Skin tissue is modeled as a half-space consisting of one layer (skin) or three layers (skin, fat and muscle) whose permittivities and conductivities are uncertain. Deterministic part is based on numerical solution of Pocklington equation via Galerkin Bubnov Indirect Boundary Element method (GB-IBEM) and numerical integration of the corresponding field integrals. Uncertainty from tissue electric parameters is propagated to APD via nonintrusive Stochastic Collocation method (SCM) in order to compute stochastic moments of APD. For 1-layered model APD stochastic moments are computed with 3 deterministic simulations. On the other hand APD mean and variance for 3 layered model are successfully computed with 13 deterministic simulations while skewness and kurtosis require 85 deterministic simulations. The ratio of APD standard deviation and mean decreases with frequency thus indicating that the uncertainty in the tissue electric properties has smaller effect on APD uncertainty at higher frequencies. Finally, sensitivity analysis carried out for both 1-layered and 3-layered models indicates the same conclusions. At 10 GHz skin permittivity and conductivity are the two most important parameters. However, as frequency increases the impact of skin conductivity prevails. This indicates that in frequency range 10-90 GHz the APD uncertainty quantification and sensitivity analysis can be carried out by using only 2-dimensional stochastic model.
{"title":"Stochastic analysis of epithelial/absorbed power density in multilayered planar skin model with uncertain tissue electric properties","authors":"Anna Susnjara Nejasmic;Dragan Poljak","doi":"10.1029/2024RS007988","DOIUrl":"https://doi.org/10.1029/2024RS007988","url":null,"abstract":"Stochastic analysis of the absorbed power density (APD) on skin surface exposed to radiation of halfwave dipole at 10, 30 and 90 GHz and for different antenna-body distances is presented. Skin tissue is modeled as a half-space consisting of one layer (skin) or three layers (skin, fat and muscle) whose permittivities and conductivities are uncertain. Deterministic part is based on numerical solution of Pocklington equation via Galerkin Bubnov Indirect Boundary Element method (GB-IBEM) and numerical integration of the corresponding field integrals. Uncertainty from tissue electric parameters is propagated to APD via nonintrusive Stochastic Collocation method (SCM) in order to compute stochastic moments of APD. For 1-layered model APD stochastic moments are computed with 3 deterministic simulations. On the other hand APD mean and variance for 3 layered model are successfully computed with 13 deterministic simulations while skewness and kurtosis require 85 deterministic simulations. The ratio of APD standard deviation and mean decreases with frequency thus indicating that the uncertainty in the tissue electric properties has smaller effect on APD uncertainty at higher frequencies. Finally, sensitivity analysis carried out for both 1-layered and 3-layered models indicates the same conclusions. At 10 GHz skin permittivity and conductivity are the two most important parameters. However, as frequency increases the impact of skin conductivity prevails. This indicates that in frequency range 10-90 GHz the APD uncertainty quantification and sensitivity analysis can be carried out by using only 2-dimensional stochastic model.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 10","pages":"1-15"},"PeriodicalIF":1.6,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595830","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}
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}
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