This paper presents the design of a dual-polarized frequency-modulated continuous wave (FMCW) radar system with a coupler-integrated lens antenna for automotive synthetic aperture radar (SAR) applications. High-resolution radar imaging is imperative for automotive use, with dual-polarized SAR imaging providing robust support in achieving this objective. However, exploration of the system design for dual-polarized FMCW SAR systems has been limited. The paper outlines the design of the aforementioned radar system, emphasizing its suitability for automotive SAR applications. It details the requisite parameters for dual-polarized automotive SAR systems and the design considerations for the dual-polarized lens antenna. Additionally, it proposes a radar signal monitoring method employing a coupler-integrated antenna to detect the radiated radar signal. Furthermore, a dual-polarization synthesis method is introduced to enhance SAR image quality. Experimental validation of the implemented dual-polarized FMCW radar with a coupler-integrated lens antenna confirms the effectiveness of the proposed system design.

This paper presents a curved-retrodirective beamforming system for improving microwave power transmission efficiency in the Fresnel region. Since microwave power transmission in the far-field region has very low efficiency, studies on the Fresnel region are being actively conducted. In these studies, a retrodirective beamforming (RDB) technique is popular. The RDB system with a sub-array structure was a realistic structure that reduced system complexity. However, the transmission efficiency is lowered because the beamwidth of the transmitter antenna element is narrow. To solve this problem, this paper proposes a curved-retrodirective beamforming system that can focus the microwave power on the receiver. The proposed system uses the peak gain of the transmitter antenna element by using tilted beams to improve transmission efficiency. The system design method that can maximize the transmission efficiency is also presented depending on the given conditions such as transmission distance, characteristics of the transmitter and receiver antenna. The simulation showed a reduction in power leakage compared to the conventional system. The fabrication and measurement validated the efficiency improvement of the proposed system for IoT devices in the Fresnel region.