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A fully polarimetric antenna system, designed using ridge gap waveguide (RGW) technology, is proposed, fabricated, and experimentally validated based on circularly polarized slots. The proposed slot element not only plays a role as a radiator but also works as a polarizer. Its geometry is very compact with aperture dimensions of $0.44 \,\lambda _{0} \times 0.44\, \lambda _{0}$ and a profile depth of $0.64 \,\lambda _{0}$ . The proposed antenna system has full circular polarizations (CPs) at both the transmitter (Tx) and receiver (Rx) and comprises four layers with the ability to directly integrate into a radar front-end. High port isolation (≥35 dB) between adjacent Rx channels is achieved by using thin decoupling walls and dummy elements to suppress mutual couplings (MCs). The measured results show an excellent field of view (FoV) (embedded axial ratio ≤3 dB) in the azimuth plane, with about ±60° at Rx and ±50° at Tx. The antenna system is engineered for low radar cross section (RCS) target detection and offers suppression of environmental noise. Experimental evaluation of the integrated radar module shows good agreement between simulation and measurement results. The work offers potential applications of such antenna systems in automotive radar systems, especially where polarization diversity and environmental robustness are required.

This article presents a novel design of an automotive polarimetric radar sensor with circular polarization (CP) at 77 GHz band based on gap waveguide technology. The proposed design employs a multiple-input multiple-output (MIMO) configuration with single-CP TX antennas and dual-CP RX antennas, enabling the acquisition of sufficient polarimetric information while reducing the number of transmitters (TXs) by half. Gapwaveguide technology is utilized for the implementation of the multilayer waveguide front-end. Series-fed septum polarizers are employed for the antenna design with low-profile characteristics. Measurement results indicate that the antenna elements enable a high level of cross-polarization across the field of view (FoV). Integration of the waveguide front-end with RF boards is achieved using gap waveguide packaging techniques. Static measurements were conducted on common scattering objects to evaluate the sensor’s performance. Polarimetric rotation signatures of the objects were acquired from the measurements, demonstrating the sensor’s potential for use in object identification tasks. Dynamic measurements were performed to evaluate the sensor’s Doppler response. The assessments indicate a high level of accuracy, confirming the effectiveness of the proposed sensor in analyzing dynamic movements. Overall, the proposed polarimetric radar sensor provides persuasive evidence that gap waveguide technology is a highly promising candidate for the realization of advanced automotive radar front-ends.

Based on the overall and related perspectives of micro-history, this paper divided the development of China's sports system into initial, transitional, formational, final, developmental, adjustment and improvement stages. On the basis of summarizing the characteristics of management in different periods of time, the sports system in China was categorized into eight organizational models from a macro perspective: military mobilization, integration of the party, government and army, function distribution, all-purpose and universal departments, limited division of labor among departments, formation of contractual relationship, non-routine task-driven and ecosystem governance. Combined with the goals of sports development, the paper expounded the core issues of sports system reform in each historical stage: the historical "mission of "national construction", the task and objective of establishing "new sports", guidelines for sports popularization and regularization", the institutional arrangement of the "national interagency mechanism", the development oriental ion of "sports socialization, reform objectives of "six modernizations and six transformations", central task of "hosting successful Olympic Games" and strategic positioning of "building a sports power". [ABSTRACT FROM AUTHOR]