In electric vehicle wireless power transfer systems, misalignment between primary and secondary coils commonly occurs, resulting in mutual inductance fluctuations that decrease transfer efficiency. To overcome this problem, this paper proposed a novel misalignment-tolerant coil design combining quadrupolar trapezoidal coils with unipolar square coils on the secondary side. These two sets of coils are connected in series through a diode rectifier, making the equivalent mutual inductance equal to the sum of their absolute mutual inductance values. When perfectly aligned, the unipolar square coils maintain good coupling with the transmitter coil while the quadrupolar trapezoidal coils remain decoupled. During misalignment, as the mutual inductance between unipolar coils and the transmitter decreases, the mutual inductance between quadrupolar coils and the transmitter increases. This complementary relationship maintains a nearly constant total equivalent mutual inductance, providing exceptional misalignment tolerance and stable system output. Simulation results show mutual inductance fluctuation of only 2.60%, with experimental verification demonstrating 3.11%. The output voltage fluctuation in simulation is just 2.51%, while the system achieves a peak efficiency of 95.52%.

The Aperture Synthetic Radiometer (ASR) system consists of an antenna array along with subsequent receiving channels and data processing modules, and it has been widely applied in Earth observation fields. The arrangement of the antenna array directly affects the system’s sampling coverage in the spatial frequency, which in turn determines its imaging quality. Therefore, we propose a cooperative optimization method for antenna arrays based on deep reinforcement learning, aiming to improve the sampling coverage of the ASR system, thereby enhancing its imaging performance. Experimental results show that the final stable coverage value of the proposed method is 10.545%, representing a 41.2% improvement over the lowest value. Furthermore, it outperforms other comparative methods in both coverage performance and reconstructed image quality, demonstrating its effectiveness in optimizing antenna array layout and enhancing the imaging quality of the system.

Sea surface salinity (SSS) is a fundamental parameter for understanding ocean phenomena and plays a vital role in studying global climate change and weather prediction models. Following the earlier launch of Soil Moisture and Ocean Salinity (SMOS), Aquarius, and Soil Moisture Active Passive (SMAP) satellites, the Chinese Ocean Salinity and Soil Moisture Mission (COSM) was successfully launched on November 14, 2024. The launched satellite is equipped with the 2-D L-band Aperture Synthesis Microwave Radiometer (LASMR) and the Microwave Imager Combined Active and Passive (MICAP) components to gather high-precision SSS information. This paper presents the Airborne LASMR (ALASMR), which features a Y-shaped two-dimensional synthetic aperture microwave radiometer and contains 11 antenna units with a unit spacing of 0.82λ. The ground test investigations of the ALASMR have been conducted to evaluate antenna patterns, test the sensitivity of receiving channels, and conduct ocean aviation experiments. To examine the flight observation, uniform salinity is assumed for the sea area obtained from the calibration platform of National Satellite Ocean Application Service (NSOAS) whereas the salinity gradient is taken for the Laizhou Bay area. The ALASMR exhibits enhanced imaging performance, with a spatial resolution of about 0.35 km and a width of about 1.24 km at the flight altitude of 1.2 km. The retrieval of SSS in the sea area of the ocean calibration platform is also demonstrated in this work. This indicates that ALASMR can reliably execute salinity observation of near-shore with high precision and provide a cross-calibration data source for COSM after its launch.

In electric vehicle (EV) dynamic wireless power transfer (DWPT) systems, changes in the mutual inductance will lead to fluctuations in the output voltage and efficiency. In this paper, a novel three-phase rectifier that can reduce the number of diodes is proposed, with each phase connected to one of the triple decoupling coils (TDC) on the receiving side. Decoupling is achieved with partial overlapping. Reverse windings are integrated into TDC to smooth the mutual inductance fluctuations. The proposed novel rectifier switches between the single-coil receiving mode and the dual-coil receiving mode in response to the different positions of the EV. The proposed magnetic coupler structure and the novel rectifier guarantee a constant output during movement. The effectiveness of the proposed DWPT system has been verified by the experimental prototype. The output voltage remains stable over a long range, with a fluctuation only about 2.23%. The proposed DWPT system can not only reduce the number of track coils but also extend the novel three-phase rectifier to multi-phase with a reduced diode number, which has good reference value.

This letter pays attention to the mitigation of the Radio Frequency Interference (RFI) sources located at coastal regions for Synthetic Aperture Interferometric Radiometer (SAIR). To remove an RFI at the visibility level, it will be necessary to estimate the Brightness Temperature (BT) of the point source, which is currently done by computing the median of the surrounded pixels to get the background BT, and subtracting it from the original contaminated BT. However, this strategy is based on the assumption that the background BT distribution around the RFI is flat, and this is not reasonable for those RFIs from coastal cities, and could result in estimation deviation. A robust RFI mitigation method is proposed without introducing complex computing. Instead of focusing only on the local area, the basic idea of our method is to step into the wide area, and minimize the overall fluctuation of the pixels affected by the RFI in the BT image. The method tests based on SMOS visibility samples validate the correctness of the developed method.

For 1-D aperture synthesis (1-D AS) radiometers, truncated sampling occurs in the frequency domain due to the system baseline limitation. Therefore, there is an obvious Gibbs oscillation in the reconstructed image. To solve this problem, an imaging method based on a 1-D convolutional neural network (1-D CNN) is proposed in this article. Compared with deep learning methods based on 2-D convolutions, the 1-D convolution not only reduces the amount of computation but also produces further performance improvements. The input data of the network are the 1-D visibility function samples, and the output data are the 1-D brightness temperature (BT) samples. The network learns the mapping relationship from the training of the 1-D visibility function samples and 1-D BT samples to complete 1-D AS imaging without any prior knowledge. To verify the performance of this imaging method, simulations and experiments based on the airborne C-band 1-D microwave interferometric radiometer (ACMIR) system are implemented. The simulation and experimental results demonstrate that the proposed AS-CNN method achieves higher performance than the inverse fast Fourier transform (IFFT) method in terms of image quality and Gibbs phenomenon suppression. In the case of an antenna failure and missing baseline, the AS-CNN method proposed in this article can still obtain a BT image with high imaging quality, which shows that the robustness of the network is better than that of the IFFT method.

In this paper, Mirrored Aperture Synthesis with tilting reflectors (MAS-T) is proposed to improve spatial resolution with fewer antennas for passive microwave remote sensing. The principle of MAS-T is given. The initial experimental results demonstrate that MAS-T can achieve higher spatial resolution with the same antenna array compared with conventional aperture synthesis.

Mirrored aperture synthesis (MAS) has been proposed as a novel interferometry to achieve higher spatial resolution in passive microwave remote sensing. The phase and amplitude errors for MAS are a crucial problem that has yet to be analyzed. In this letter, a model for the phase and amplitude errors is established. A correction method based on an external source is proposed to correct the phase and amplitude errors. An analysis of the position of the external source is performed by computing its impact on the radiometric accuracy of a reference scene. The imaginary parts of the cross correlations for MAS are analyzed for the first time. Simulations and experiments are carried out to demonstrate the effectiveness of the correction method.

In this letter, 1-D mirrored aperture synthesis with two tilted reflectors (1-D MAS-T) is proposed to improve the spatial resolution of an antenna array without extending its size. The principle of 1-D MAS-T is given. The size of the reflector is analyzed, and detailed calculation formulae is derived. Numerical simulations and experiments are carried out to illustrate the performance of 1-D MAS-T. The results demonstrate that 1-D MAS-T can achieve a higher spatial resolution than conventional aperture synthesis with the same antenna array.

The medium- and large- scale global sea surface temperature (SSTs), which is an important ocean parameter, are mainly measured by the space-borne microwave radiometry. However, the resolution and sensitivity are greatly limited by antenna size, orbit altitude, and flight speed. In this paper, an airborne C-band one-dimensional (1-D) microwave interferometric radiometer (ACMIR) is developed to obtain the SSTs with a high resolution and sensitivity. The spatial resolution of the ACMIR ranges from 40.7m to 612m, corresponding to the flight height of 500m to 8000m, while the sensitivity varies from 0.25K to 0.36K, associating with the boresight to the edge of the field of view. In order to evaluate the performance of the ACMIR, an ocean aviation experiment was conducted in the coastal area of the Yellow Sea in September 2020. The land observation results indicate that typical ground objects can be clearly distinguished. Furthermore, thesea surface brightness temperatures acquired by the ACMIR are compared with the estimates based on the radiative transfer model, with SST retrieval error of 0.77°C. The ACMIR can offer a high-resolution and accuracy of SST especially in coastal areas, and can meet several application requirements related to SSTs.

In 2-D mirrored aperture synthesis (2-D MAS), the array configuration determines the rank of the transformation matrix, which can affect the accuracy of the solved cosine visibilities. Ultimately, errors in solved cosine visibilities degrade the quality of reconstructed brightness temperature images. In this letter, the maximum rank of the transformation matrix is analyzed and proven by mathematical induction. An array optimization model of 2-D MAS based on the “maximum-rank” criterion is established, and optimal arrays are presented. Finally, the simulations and experiments are carried out to demonstrate the effectiveness of the optimization model.

In two-dimensional mirrored aperture synthesis (2-D MAS), the rank of the transformation matrix can affect the accuracy of the solved cosine visibilities; therefore, it has an impact on the accuracy of the reconstructed brightness temperature image. In this article, the influence of the rank deficient on the accuracy of the reconstructed brightness temperature image of 2-D MAS is discussed. An analysis of the rank-deficient error is performed by computing its impact on the radiometric accuracy for a reference scene. Two correction methods based on multiple measurements are proposed to correct the rank-deficient error. The simulations and experiments are carried out to demonstrate the effectiveness of the proposed methods.

Aperture synthesis technique is able to provide high spatial resolution without requiring very large and massive real aperture. Recently, in addition to the well-known aperture synthesis radiometer, the concept of mirrored aperture synthesis has been proposed, and the experiments has been carried out to validate this technique. However, the field of view (FOV) of a mirrored aperture synthesis radiometer (MASR) has not been analyzed. In this paper, the FOV of an one-dimensional MASR is analyzed based on the symmetric convolution. A simulation and experiment are carried out to validate the derived FOV. The FOV of a two-dimensional MASR can be analyzed in the same way.

The concept, principle, and method of microwave radiometric imaging with mirrored aperture synthesis (MAS) were proposed by the Huazhong University of Science and Technology (HUST), Wuhan, China. MAS can achieve higher spatial resolution without extending the size of the antenna array. However, the MAS principle has not been sufficiently validated by practical experiments. To solve this problem, an innovative experiment system of MAS at the V-band (MAS-V) has been developed by HUST. Experiments on the interference fringe pattern, spatial resolution, as well as the imaging of an electric warmer and the absorbing material in the styrofoam box filled with liquid nitrogen are performed. The initial experimental results demonstrate that MAS can achieve higher spatial resolution with the same antenna array compared with the conventional AS. For MAS, the experimental results are consistent with theory and simulation results.

Mirrored aperture synthesis (MAS) has been proposed to utilize a few antennas to provide high spatial resolution for atmospheric remote sensing. In order to verify the fundamentals of mirrored aperture synthesis (MAS) further, a prototype working at V band was developed in the past two years. In this paper, the prototype is briefly introduced, and then some indoor experiments and the experimental results for one-dimensional MAS based on the prototype are presented, mainly including the fringe pattern experiment for verifying the correlation output and the imaging experiment based on two point sources for evaluating the spatial resolution of MAS.

Mirrored Aperture Synthesis (MAS) was proposed to improve spatial resolution for passive microwave remote sensing. However, the MAS theory needs experimental verification. In this paper, an Experimental System of MAS (MAS-V) at V frequency band is introduced, which is developed for verifying the principle and performance of MAS. MAS-V is composed of an antenna array, reflectors, a receiving channel array, a synchronous acquisition subsystem, a computing server, and a rotatory platform. The initial experimental results demonstrate that the principle of MAS is valid. The experimental spatial resolutions are consistent with the theoretic spatial resolutions.