This paper presents a 24 GHz circularly polarized (CP) two-dimensional (2D) MIMO FMCW radar front-end based on a scalable aperture-shared array for compact IoT radar imaging. The key contribution is an aperture-shared CP architecture that enables dense Tx/Rx integration within a compact footprint, addressing a fundamental limitation of conventional 2D MIMO radars in which improving angular sensing efficiency under a size-constrained aperture typically requires a larger physical aperture and therefore results in poor spatial efficiency for compact platforms. The proposed design implements a shared-aperture tile that integrates 2 TX and 4 RX channels within a 2.0λ0 × 2.0λ0 aperture, while preserving wide 2D angular coverage and practically sufficient angular discrimination for volumetric sensing tasks relevant to IoT applications. High-isolation operation under dense aperture sharing is achieved through a co-aperture CP antenna structure incorporating a defected ground structure (DGS), which maintains radiation integrity and mitigates Tx-to-Rx leakage and coupling. The proposed architecture also supports scalable tiling of identical aperture-shared tiles to extend the effective 2D aperture while preserving a compact per-tile footprint. The proposed radar is validated through an end-to-end hardware prototype with simulations and measurements, demonstrating reliable multi-target separation and two-dimensional imaging capability.

This article presents a hybrid power-combining rectifying antenna array designed to broaden the spatial coverage of self-powered Internet of Things (IoT) devices. The receiver’s coverage, which receives power from microwave power transmission (MPT), could restrict the placement of IoT devices. To address this, we propose a new hybrid power combining method. This method simultaneously integrates both RF and dc power combining techniques, allowing for efficient power reception without being constrained by the direction of RF signal reception. The proposed method includes the design and fabrication of a dual-port antenna array, a reconfigurable passive beamforming network, and a rectifier. Theoretical analysis, simulations, and experimental validations confirm the enhanced performance of the proposed method over traditional RF and dc power combining techniques. Our hybrid approach demonstrates wider spatial coverage, higher received power, and improved efficiency, making it a robust and flexible power supply solution for IoT devices.

In the context of automation, managing large volumes of data with ultralow latency is crucial. Maintaining continuous connectivity with mobile robots, which are equipped with multiple sensors and connectivity options, presents a particular challenge. This necessitates broad coverage for sensors and communication networks. To address this challenge, a novel antenna design is introduced that promises comprehensive mmWave connectivity, integrating Industrial Internet of Things (IIoT) with mobile robotics applications. The solution requires the use of planar antenna arrays due to the necessity for the fabrication of integrated chips and antennas within a single mmWave communication module. Traditional patch-array antennas have a limited beamforming range of 120°, constrained by their ±60° radiation pattern. However, the newly proposed flat-panel array antenna (FPAA) extends this range to approximately 160°, significantly minimizing blind spots. The proposed FPAA utilizes a simple planar structure with a dielectric grid layer. It achieves scan angles of 162° and 168° in the E- and H-planes, respectively, at 28 GHz, offering more than 42% improved coverage compared to traditional patch-array antennas.

This article proposes a widebeam coverage antenna solution for a low-complexity millimeter-wave (mmWave) indoor Internet of Things (IoT) network. The proposed switched beamforming antenna (SBA) system eliminates the need for complex feed networks or beamformers by utilizing a single RF switch and multiple radiators. Each radiating element of the antenna is capable of generating multiple main lobe directions, ensuring wide beam coverage and sufficient antenna gain. This design approach effectively addresses the key requirements of distributed antenna system (DAS) configurations, including low complexity, low loss, low power consumption, and cost effectiveness for indoor IoT networks. To validate the effectiveness of the proposed SBA solution, a three-radiator-based SBA was fabricated. The antenna core size was compact, measuring$1.77\,\,\lambda _{0} \times 4.3\,\,\lambda _{0} \times 0.05\,\,\lambda _{0}\,\,(\lambda _{0}$representing the free-space wavelength at 28 GHz). This compact size is more suitable for indoor low-profile networks compared to previously reported SBAs. Experimental measurements revealed peak gains of 5.62, 7.2, and 5.77 dBi for the three different radiation patterns, respectively. Moreover, each beam pattern exhibited a measured 3-dB beam coverage of 101°, 64°, and 106°. The overall 3-dB beamwidth of the system based on the peak gain of the boresight ranged from −66° to 64°, which is wider than previously reported works.