Beam scanning antenna brings new opportunities to reduce the data collision of multinode communication in the Internet of Things (IoT). This article proposes a new type antenna design scheme that can be used for IoT relay communication. A programmable beam scanning antenna without phase shifters operating in the X-band is designed to evaluate the feasibility of this scheme. The integrated design of excitation source and phase-modulated structure greatly reduces the profile of the antenna and improves the integrated degrees of freedom with other equipment. By switching the state of the PIN diode loaded on each element, different radiators can be selected and the direction of current polarization on elements can be adjusted to change the radiation phase. Furthermore, the diode states are encoded by the holographic antenna theory and controlled by the FPGA controller to realize programmable beam scanning. One-element, two-element, and 1-D array containing 32 elements are fabricated and measured. The experimental results are in good agreement with the simulation data. The operating bandwidth is 7.5% at 10 GHz while the beam scanning range of the array is $- 60{^\circ }$ –60°, with a good scanning accuracy and stability. The proposed low-profile beam scanning antenna can provide stable communication services to multiple users and smart devices as a new type of beam scanning array antenna solution for the IoT application, which is beneficial to this field.

Wireless power transfer (WPT) and wireless energy harvesting (WEH) using rectennas are becoming an emerging technology. This paper presents a novel design method for a rectenna suitable for a wide range of selectable operating frequency band, input power level, and load impedance. Most importantly, it is realized without using complex impedance matching networks which shows significant advantages over existing rectennas in terms of the structure and cost. A rectenna example has been designed, made, and tested using this novel method. The proposed rectenna has a compact size of 90 × 90 × 1.58 mm ³ and operates at four different frequency bands that are selectable from 1.1 to 2.7 GHz. Over 60% (up to 85%) energy conversion efficiency is achieved for the input power from 0 to 15 dBm and load impedance between 700 and 4500 Ω. The rectenna shows excellent performance for the target applications (WPT and WEH) with a much-simplified structure and reduced cost.

The concept of dual-band reconfigurable terahertz patch antenna using a graphene-stack-defined backing cavity is presented. The proposed antenna employs patch resonance based on backing cavity defined by interleaved graphene/Al ₂ O ₃ stacks, which can be dynamically dual-resonance frequency-tuned on large range about 1 THz via electrostatic gating on the graphene stack. The performance is analyzed in terms of its directivity, sidelobe suppression, return loss, and bandwidth for different chemical potential. By applying different voltages on graphene stack, the direction of the antenna main beam can be steered with appreciable variation range.

A tiny and compact implantable antenna for wireless cardiac pacemaker systems is designed. The antenna works in the Industrial Scientific Medical (ISM) frequency band (2.4–2.48 GHz). The size of the antenna is greatly reduced with the adoption of a high dielectric constant medium and a folded meander structure. The volume of the antenna is 4.5 mm³, and the size is only 3 mm × 3 mm × 0.5 mm. Based on the literature research, it was found that the design was the smallest among the same type of implanted antenna. The antenna is optimized and loaded with a defective slotted structure, which improves the efficiency of the overall performance of the antenna and thus the gain thereof. The antenna maintains good impedance matching in the ISM frequency band, covering the entire ISM frequency band. The actual bandwidth of the antenna is 22%, with the peak gain of − 24.9 dBi. The antenna is processed and manufactured in such a manner that the simulation keeps consistent with the actual measurement. In addition, the specific absorption rate of the antenna is also evaluated and analyzed. The result shows that this kind of antenna is the best choice to realize the wireless biological telemetry communication in the extremely compact space of the wireless cardiac pacemaker system.

This paper presents a novel wearable antenna sensor based on localized surface plasmons (LSPs) for communication and non-invasive sweat monitoring. The sensor is made up of corrugated plasmonic structures based on the conventional printed monopole antenna, which achieves multi-band and miniaturization. The physical dimensions of the antenna sensor are 35 × 34 mm ² , with a thickness of only 0.13 mm. Simulated and measured results demonstrate that the proposed antenna sensor covers triple operating bands, including 2.4 GHz and 5.8 GHz ISM bands, as well as high frequency ultra-wideband ranging from 7.89 GHz to 9.56 GHz. The antenna sensor exhibits a good radiation pattern with a peak gain of 3.02 dBi and a high quality factor (Q) up to 35. The use of polyimide as a dielectric substrate enables the antenna sensor to achieve flexibility and conformality, maintaining stable operating states even when bent and deformed. The specific absorption rate (SAR) values in three frequency bands are simulated and evaluated to ensure its safety for human health. Moreover, the resonant frequency of antenna sensor significantly shifts with the volume and concentration of sweat, indicating that the proposed sensor is highly sensitive to sweat volume and concentration with a sensitivity of 120 MHz/1mm and 4.57 MHz/1, respectively. The proposed wearable antenna sensor is a promising candidate for a sweat monitoring system for athletes or patients, allowing for health monitoring at any time and place.

In this paper, a miniaturized wearable antenna is proposed, which has five band-notched characteristics. The antenna uses Rogers 5880 as the dielectric substrate, with a thickness of 0.508mm. Due to its thickness, the antenna can be bent slightly and used in the wearable field. The antenna is fed by a microstrip line with an input impedance of 50 ohms. Through the design of notch structures inside the radiating patch, on either side of the feed line, and on the bottom of the substrate, five notch bands are made possible. More notch bands can be produced by employing a new structure which produces two notch bands as well as adding metal on the substrate's sides that allows current to be introduced into the notch structures on the bottom of the substrate. Based on this, it is possible to achieve great space utilization and little interaction amongst notch structures. The proposed antenna has overall size of 30x25x0.508mm ³ and covers the entire UWB spectrum from 2.56 GHz to 12.7 GHz except notch bands from 2.58 GHz to 3.21 GHz, 4.05 GHz to 4.29 GHz, 5 GHz to 5.64 GHz, 8.60 GHz to 9.05 GHz, 9.20 GHz to 10.32 GHz. By applying the antenna to the doctor's chest badge, the number of swiping cards by hands can be reduced, which is convenient and avoids bacterial pollution. Thus, the antenna has a useful purpose in the medical development.