Search

In this paper, we introduce a novel design for a high-gain, low-profile quad-feed folded transmitarray antenna (FTA) to enable a more compact system. The proposed antenna system consists of a transmitarray, a reflectarray, and four identical planar microstrip U-slot patch antennas placed on the same surface of the reflectarray with an adjacent distance greater than 1λ. To compare the effectiveness of our design, we developed three different antenna array systems with the same aperture size: a single-feed transmitarray antenna (TA) system, the proposed quad-feed FTA system, and a single-feed FTA system. Our experimental results demonstrate that employing four symmetrical feeders with an adjacent distance of 3.2λeffectively reduces the height by about 76.7 % in comparison to the height of a single-feed TA, and by 30 % when compared to the height of a single-feed FTA. We also present the design, fabrication, and testing of a prototype of the proposed quad-feed FTA operating in the Ku-band. The measured results of the prototype confirm the effectiveness of our design.

Localizing and reconstructing interference sources is crucial in applications such as electromagnetic interference. While the electromagnetic time-reversal (TR) method has been proposed for source localization, there is limited experimental validation for TR source reconstructions. This letter presents a theoretical analysis and experiments that validate the feasibility of TR source reconstruction within a closed metallic cavity. Wideband signals emitted by the sources are measured at preselected locations in the frequency domain using a vector network analyzer. These measurements are then converted to time-domain signals using a simple algorithm and subsequently time-reversed. The time-reversed signals are injected back into the solution domain, and backward propagation is numerically simulated to locate sources, incorporating space and time kurtoses. The results confirm the effectiveness of the TR method, validating the theoretical analysis and providing a pathway for developing a realistic hardware-based TR source reconstruction system.

The stable vehicular space-air-ground integrated network (SAGIN) requires high-gain multi-beam/beam-steering antenna systems. In this paper, we propose a compact high-gain wideband circularly-polarized (CP) beam-steering antenna with novel rotatable phase-gradient metasurface (PGM) transmitarrays for the SAGIN. It consists of a novel substrate-integrated-waveguide (SIW) array feed and three innovative metasurface transmitarrays (M0, M1, and M2), capable of providing any compensation phases between 0° and 360°. The novel PGM unit cells have two identical CP U-slot patches that perform CP-to-CP conversions with high transmission efficiencies. In addition, a new and accurate beam-steering analytical formulations are proposed for fast predictions of scanning angles. Experimental results show that the proposed compact SIW array feed achieves an aperture efficiency of 58.8%, a 3-dB gain bandwidth of 10.8%, and a 3-dB axial ratio (AR) bandwidth of over 23%. The proposed entire beam-steering antenna achieves a peak gain of 27.56 dBic, which corresponds to an aperture efficiency of 48.5%, and an exceptionally wide 3-dB AR bandwidth within the scanning range. It is a strong candidate for future millimeter-wave communications in satellite and radar systems and vehicular communications.

The time-reversal (TR) method has been proven effective in reconstructing sources due to its spatiotemporal focusing properties. Much work so far on the topic has been conducted with sources of specific frequency bandwidths. However, most sources in practical situations are time-harmonic or single frequency. This letter proposes a novel approach to address this challenge by analyzing the TR method in the frequency domain and modifying it to derive a source condition for single-frequency sources. The proposed method is validated through numerical examples, demonstrating its effectiveness in source reconstruction. This work provides an alternative pathway for further development of practical electromagnetic source reconstruction techniques and testing systems.