In this paper, a small size multistubs resonator based flexible wearable antenna is demonstrated for dual-band operation. The proposed antenna is composed of vertically aligned multistubs resonator, a 50 Ω microstrip feed and a defected ground structure (DGS). This configuration of antenna resonates at 2.4 and 5.8 GHz Industrial, Scientific, and Medical (ISM) sub-6 GHz bands. It has a small footprint of 32 × 17 × 0.508 mm³ (0.256 λ_L × 0.136 λ_L × 0.004 λ_L at f_L = 2.4 GHz), with measured reflection coefficient magnitudes (|S₁₁|) of − 15.81 dB with bandwidth of 280 MHz (2.3–2.58 GHz) and − 33.06 dB with bandwidth of 580 MHz (5.42–6 GHz) at 2.425 and 5.72 GHz, respectively. Moreover, it has bidirectional and omnidirectional radiation features due to DGS with a measured peak gains of 1.317 dBi (2.425 GHz) and 4.759 dBi (5.72 GHz). This study also explored a widespread investigation on a parametric study, specific absorption rate (SAR), diverse bending conditions and its interaction with diverse on-body circumstances (by placement on the chest, hand, and leg). The SAR values are 1.29 W/kg (1 g) and 0.88 W/kg (10 g) at 2.43 GHz whereas at 5.8 GHz, the SAR values are 0.507 W/kg (1 g) and 0.257 W/kg (10 g), which well within SAR safe limits. The antenna adhere the effective robustness, stable performance during bending deformations and on-body scenarios which validated the antenna effectiveness for wearable sub-6 GHz ISM band applications.

This article presents a defected ground structure (DGS)-based deformed microstrip wearable antenna for ON/OFF body smart wearable Internet of Things (IoT) applications.. The antenna design has certain features such as lightweight, cost-effectiveness, low profile, and flexibility. Fabricated using a Rogers RT/Duroid 5880 substrate with a thickness of 0.508 mm, the proposed antenna includes a deformed rectangular patch and DGS to enhance impedance matching and radiation performance at 2.45 GHz. The results show a low reflection coefficient of approximately −36 dB and a peak gain of 5.61 dBi at 2.45 GHz in a free-space environment without bending. Additionally, the specific absorption rate (SAR) is measured to be 0.249 W kg⁻¹ for 1 g of tissue and 0.137 W kg⁻¹ for 10 g of tissue when the antenna is placed 0.32λ ₀ away from the body. The study also indicates that SAR values decrease as the distance between the antenna and the body increases. The antenna prototype has been fabricated and experimentally tested under various ON/OFF body conditions and bending scenarios. The measured results closely align with the simulated data, confirming the antenna suitability for ON/OFF body IoT applications. Noteworthy features of the proposed wearable antenna include its conformability and suitability for body-worn applications, making it an excellent candidate for ON/OFF body smart wearable IoT devices.

The current study demonstrates a dual and wideband mmWave 4 × 4 port MIMO antenna for 5G and beyond applications. The proposed antenna is derived from a traditional inset-fed rectangular geometry, modified with multiple curved edges on the top plane to produce a large effective aperture and enable significant surface current distribution. Partial ground planes are connected using 45° tilted conducting strips to form a common ground, which enhances surface current distribution and balances power through each port. The antenna exhibits wide bandwidths of 2.3–6.5 GHz at resonant frequencies of 28–38 GHz, respectively. Moreover, the suggested antenna yields more than 21 dB isolation, 8.3 dB peak gain, 92% radiation efficiency, 89% multiplexing efficiency, an ECC of 0.00007, and a channel capacity of 21 bit/s/Hz. To validate the antenna design, the prototype was fabricated on a Rogers RT/Duroid 5880™ substrate, tested, and compared with simulated results, showing good agreement.