A co-design of wide-band, high-gain, filtering, and single-feeding method is proposed to meet the demand of multifunctional antenna for Internet of Vehicles (IoV) applications. This single antenna enables the IoV communication to operate across multiple frequency bands within a long distance simultaneously, while maintaining frequency-interference-resilient performance. The metasurface (MS), composed of 4 × 4 rectangular patches, is centered on the substrate. To improve the bandwidth and gain, a pair of dipoles are placed on two sides of the MS to form a hybrid antenna with three resonant modes. At the same time, the MS and the dipoles produce the 1stradiation null. The MS is fed by a slot line, and two dipoles are fed by two U-shaped microstrip lines. The two feeding structures are mixed together through the microstrip-slotline-microstrip transition with a single exciting port. Two pairs of coupled lines (CL 1 and CL 2) are used to increase the steepness at the edges of the passband, which can produce 2ndand 3rdnulls. Two open-circuit microstrip lines are added to the feeding line to generate 4th, 5th, and 6thnulls, which can further suppress the out-of-band low- and high-frequency radiation capabilities. The proposed antenna has an impedance bandwidth (IMBW) of 33.9%, a high gain of 9.9–11 dBi within the passband, and an out-of-band suppression width of 1.93f0.

Mobile smart devices, such as smart glasses, smartwatch, smartphone, and unmanned aerial vehicle (UAV), have rich capabilities of Internet of Things (IoT). They are so handy and ready-to-use that interfacing with the ubiquitous IoT nodes becomes much easier. Mobile smart devices capability of multi-protocol massive IoT relies on enough bandwidth of their antennas. However, the small size results in a higher quality factor (Q-factor) of the antennas, which severely constrains the bandwidth. In this paper, we proposed a novel feeding mechanism that can excite and detune dual-degenerate modes for multiple orders of a loop antenna, compared with present loop antennas one single mode/resonance for each order. This loop antenna significantly increases the number of the excited modes/resonances up to 12, thus covering 0.73–7.10 GHz, including the whole sub-6 GHz band, which is several times that of the present loop antennas. Further, we demonstrated its size-compressing method. An even smaller folded multi-order-dual-degenerate-modes loop antenna was applied to smartwatch-size devices. It achieves a bandwidth of 1.74–8.87 GHz, which is several times that of the present smartwatch antennas. The proposed method requires no impedance-matching networks, multi-ports, switches, or tuners, offering ultra-broadband, low-loss, and cost-effective advantages. Because of its ultra-broadband property, it provides a ready-to-use antenna solution to massive IoT, ultra-wideband (UWB) energy harvesting, and multi-band cellular network communication for mobile smart devices.

Quasi-isotropic antennas are essential to the massive Internet of Things (IoT) of 6G for mobile smart devices, such as uncrewed aerial vehicle (UAV)/uncrewed ground vehicle (UGV) and smart glasses. However, until now, present quasi-isotropic antennas can achieve at most two discrete frequency bands. It is because of the substantially increased structural complexity with the increased number of frequency bands. Since dual-band property is much far from the requirement of massive IoT, we investigated a novel method for multiband (>2) quasi-isotropic antennas. This method combines two inductor-embedded U-radiators, manipulates and purifies the four isotropically radiated modes, and excites all of them simultaneously by wideband-matching capacitive coupling feeding. Consequently, four isotropically radiated frequency bands are produced with a highest-to-lowest frequency ratio up to 3. More importantly, this method has great potential to achieve even more frequency bands for future massive IoT applications. This research releases quasi-isotropic antennas from the constraint of dual frequency bands, which impedes the advances of 6G massive IoT.

Millimeter wave (mm-wave) antenna modules with switchable beam radiation provide a potential solution for enabling flexible wireless links and high data rate in Internet of Things (IoT) networks. Aiming to simultaneously fulfill a wide coverage and follow the cost-effective principle of IoT devices, a novel mm-wave wideband antenna module with switchable fan-beam radiation is proposed based on an air-filled planar Cassegrain beam-former. A comprehensive design procedure combing the theoretical calculation and differential evolution (DE) algorithm is first introduced to construct the beam-former with wide-angle scanning capability. The desirable aperture-shared switchable fan-beam radiation with high crossover is then obtained with the aid of a proposed two-feed-per-beam (2FPB) scheme based on a low-loss integrated switch network. A prototype of the antenna in the Ka-band is fabricated by simultaneously adopting the metallic 3-D printing and printed circuit board (PCB) technology. Excellent operating characteristics, including a wide bandwidth of more than 32%, twenty stable fan-shaped radiation beams scanning over a wide angular range of ±45° in the H-plane, a high beam crossover of about −3 dB, a gain of up to 19.6 dBi, and a radiation efficiency of greater than 80% are demonstrated experimentally. With the ability to fulfill the radio coverage within a wide conical area, the presented antenna module would be an attractive candidate for the fifth generation (5G) IoT applications.

Smartwatch is a potential candidate for the Internet-of-Things (IoT) hub. However, the performance of smartwatch antennas is severely restricted by the smartwatch structure, especially when the antennas are designed by traditional methods. For adapting smartwatches to the role of IoT hub, a novel method of designing the multiband smartwatch antenna is presented in this article, aiming at increasing the number of frequency bands, omnidirectivity, and structural suitability. First, the fundamental structure (including the full screen and the system PCB) of the smartwatch is analyzed as a whole by characteristic mode analysis (CMA). Thus, abundant resources of characteristic modes are introduced. The fundamental structure is then modified as the radiator of a multiband antenna. Then, a nonradiating capacitive coupling element (CCE) excites the desired four 0.5${\lambda }$modes from this structure. This method could fully utilize the intrinsic modes of the smartwatch structure itself, thus exhibiting multiple advantages: significantly small size, smaller ground, omnidirectional radiation, and fitting to the full-screen smartwatch structure.