AbstractRETRACTION: H. U. Tahseen, L. Mescia, and L. Catarinucci, “A Survey of Five Generations of MIMO Multiband Base Station Antennas,” Radio Science 58, no. 7 (2023): e2023RS007725, https://doi.org/10.1029/2023RS007725. The above article, published online on 18 July 2023 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal Editor‐in‐Chief, Sana Salous; the American Geophysical Union; and Wiley Periodicals LLC. The first author, H. U. Tahseen, asked to retract the article due to a major unattributed overlap between the figures and tables of this article (Figures 3–15, Table 1, 2 and 4) and another article previously published elsewhere by a different group of authors (Farasat et al., 2021). Such publishing practice is against the journal's policy and Wiley's Best Practice Guidelines on Research Integrity and Publishing Ethics. The first author, H. U. Tahseen has confirmed that the co‐authors, L. Mescia and L. Catarinucci, were not involved in the practice described above. The authors were informed but did not agree to the retraction wording.

AbstractThis study introduces the development of a flexible and compact radiator using a jeans material as a substrate for wireless body area network (WBAN) applications. A fabric made of jeans with a thickness of 0.6 mm, a tangent loss (tan δ) of 0.02, and a dielectric constant (εr) of 1.6 is used for designing an element with dimensions of 18.5 × 27 × 0.6 mm3. The jeans substrate incorporates a triangular feed structure on top and a defected ground structure on its back. This design enables a span ranging from 3.41 to more than 20 GHz, with a magnitude of S11 < −10 dB, a peak gain of 4.48 dBi, and a peak efficiency of 97.28%. The system is designed for Ultra‐wideband (UWB) integrated with Ku band. The measurement findings are very consistent with the results obtained from the models. The suggested antenna is highly appropriate for WBAN applications because of its thin profile, flexible design, and compatibility with WBAN and UWB technologies.

AbstractThis paper introduces an innovative blind adaptive 3D Beam steering algorithm designed to mitigate interference, ultimately improving the signal‐to‐interference and noise ratio (SINR) to enhance the overall performance of mMIMO (massive multiple‐input multiple‐output (MIMO)) networks. The proposed algorithm combines an optimized direction of arrival (DoA) estimation method with an inventive adaptive signal processing technique. To address the computational complexity associated with determining the 2D‐DoA of incoming signals, an improved RD‐MUSIC (Reduced Dimension ‐ MUltiple SIgnal Classification) estimator is proposed. This method streamlines the process into an efficient 1D search, significantly reducing computational overhead compared to conventional 2D‐MUSIC and minimizing noise, maintaining superior accuracy over the conventional RD‐MUSIC method. Leveraging the estimated 2D‐DoAs, the proposed adaptive signal processing technique integrates the Dolph‐Chebyshev weighting method with nulling constraints to calculate the optimal complex weig0hts necessary to accurately steer the main Beam toward the desired signal direction and create deep nulls in the directions of interfering signals, resulting in enhanced SINR. Compared to alternative algorithms, our approach demonstrates superior performance and offers an efficient solution without requiring a training signal or additional antenna elements. This is advantageous, particularly in environments with intense interference and high mobility, making it a promising candidate for future wireless systems.

AbstractThis article introduces the concept, theory, and design of an angle and polarization insensitive radar cross section (RCS) reduction metasurface, using a hybrid mechanism of polarization conversion and absorption. By introducing ladder‐ and rectangle‐shaped metallic patches in the vertical dimension of a 3‐D structure, polarization conversion rate (PCR) deterioration, brought by the increase of equivalent substrate thickness at oblique incidences, can be suppressed. Furthermore, lumped resistors are loaded at proper places in each polarization conversion cell, to achieve the power absorption while maintain the angular insensitivity of the PCR. With the above hybrid mechanism, a stable 10‐dB RCS reduction can be achieved regardless of the angle of incidence in a wide range and polarization directions. An equivalent circuit model is established for explaining the physical mechanism of the proposed metasurface. For validation, a prototype is fabricated and tested. Measurement results indicate that, for both monostatic RCS at the normal incidence and specular RCS of off‐normal incidences from 0° to 45°, a 10‐dB TE‐ and TM‐mode RCS reduction can be achieved in the entire X‐band (8–12 GHz) and Ku‐band (12–18 GHz).

AbstractIt has been previously established that the Doppler velocities of F‐region ionospheric echoes observed by the Super Dual Auroral Radar Network (SuperDARN) at high frequencies (HF, 8–20 MHz) are persistently lower than those measured by other instruments at the same locations. This was attributed to the ionospheric refractive index for HF radio waves being noticeably smaller than one. The refractive index values can be obtained in two ways: based on electron density estimates from a co‐located instrument or a model, or by deriving them from SuperDARN elevation angle data. To compare these methods, we considered line‐of‐sight Doppler velocity observations by the Rankin Inlet (RKN) SuperDARN radar and the Resolute Bay Incoherent Scatter Radars (RISR). The velocity data were supplemented by electron density measurements from RISR. The elevation angle data were also used for accurate determination of SuperDARN echo geolocation because the actual ground range to the echo location may significantly differ from that obtained with the conventional SuperDARN models. The RISR Doppler velocity values were used as a reference to the RKN observations via 0.5‐hop and 1.5‐hop propagation paths. Correction by the index of refraction based on both maximum electron density from the RISR and elevation angle data from RKN brought 0.5‐hop data close to the RISR velocity values, with the latter representing a self‐contained approach. However, for 1.5‐hop echoes from the polar cap, the uncorrected SuperDARN velocities exceeded those from RISR. We discuss potential causes of this apparent anomaly.

AbstractHigh frequency radio wave propagation is sensitive to absorption in the D and lower E‐region ionosphere. Absorption models typically characterize attenuation expected at 30 MHz, meaning scaling relationships are required to map to absorption expected at other frequencies. This is important when evaluating absorption at <20 MHz, as these frequencies are typically used for communication, and are highly sensitive to ionospheric disturbances. Typically, a power law relationship between absorption and frequency with a coefficient of n = −2 is used. This relationship can be demonstrated through consideration of the Appleton‐Hartree equation. This paper examines the performance of this relationship using data from the Kilpisjärvi Atmospheric Imaging Receiver Array for 13–14 November 2012. Using absorption measured at 30 MHz as a baseline, the power law relationship was used to calculated absorption at frequencies of 10–80 MHz. For this event, the power law relationship performed well when the measured absorption at 30 MHz was <1–2 dB, but strongly overestimated measurements as absorption increased. Performance improved when n was allowed to vary as a function of the overall level of absorption at 30 MHz. This accounts for local ionospheric changes associated with absorption events that change the balance of parameters in the Appleton‐Hartree equation causing deviation from n = −2. To further accommodate deviations associated with both local ionospheric disturbances and ambient electromagnetic noise contributions, an empirical relationship relating the logarithm of absorption to frequency was evaluated as a function of overall absorption. Compared to the simplified n = −2 power law relationship between absorption and frequency, the new relationship better represents measured absorption for the event studied.

AbstractDigital Radio Mondiale (DRM) is a digital Orthogonal Frequency Division Multiplexing (OFDM) broadcasting standard that has been employed all over the world. The operating carrier frequency and time of DRM station change with the scheduling period. The user terminal commonly uses channel decoding and audio decoding to detect the DRM radio. This conventional signal detection method always fail when the station is not working, or the signal‐to‐noise ratio (SNR) is weak, or the designated frequency band is illegally occupied. Besides, the conventional method needs at least one DRM transmission super frame with a duration of 1.2 s, which causes delay and brings additional computations. To solve the challenges faced by conventional method, this paper has proposed an agile and efficient signal detection method based on the Generalized Likelihood Ratio Test. The proposed method coherently integrates the frequency pilots of successive OFDM symbols via discrete Fourier transform, then propose a sufficient statistic to detect the DRM radio. The required number of OFDM symbols, which is much smaller than that of one transmission super frame, is adaptively chosen from the given probabilities of false alarm and correct detection. The computations and SNR requirement of the proposed method are both smaller than the conventional method, which help the user terminal quickly detect the DRM signal over the given frequency band. The proposed method also provides a new perspective for electromagnetic spectrum management.