A Compact Super Wideband 5G Hilbert Slot Antenna for Wearable and IoT Applications

• Compact Design: A super-wideband (SWB) Hilbert Slot Antenna (HSA) measuring only 7.31 × 7.31 mm², fabricated on semi-flexible Rogers RT/Duroid 5880 substrate. • Wide Coverage: Operates across 24.71–63.81 GHz, covering all 5G FR2 bands (n257–n263). • High Performance: Achieves 39.1 GHz bandwidth and peak gain of 7.22 dBi with radiation efficiency up to 90.88%. • Design Optimization: Extensive parametric studies improved impedance matching, bandwidth, and gain without increasing size. • Wearable Suitability: Stable performance under bending and near-body operation (arm, shoulder, chest) with only minor matching degradation and increased bandwidth. • Safety Compliance: SAR values within FCC and EU limits, ensuring safe use in wearable devices. • Experimental Validation: Measurements closely match simulations for S11, gain, efficiency, and radiation patterns. • Application Potential: Suitable for compact 5G wearable and IoT devices; future work aims at MIMO integration and fully flexible substrates. This work presents the design, fabrication, and measurement of a compact, super-wideband (SWB) 5G mmWave Hilbert Slot Antenna (HSA) that includes all Frequency Range 2 (FR2) bands (n257-n263). The antenna is fabricated on a semi-flexible Rogers RT/Duroid 5880 substrate, known for its low losses at high frequencies (Ɛ r = 2.2, h = 0.508 mm, tan(σ) = 0.004). Despite its small size of 7.31 × 7.31 mm ² , the proposed antenna achieves an impressive measured super-wide bandwidth of 39.1 GHz, with a peak gain of 7.22 dBi. The design evolution of the HSA is thoroughly explored, focusing on the effects of iteration, segment count, and feed point location on antenna performance. Parametric studies reveal the antenna's optimized configuration, showcasing significant bandwidth improvements and a reduced size compared to other designs. The antenna's suitability for wearable, body-centric applications is discussed, with an emphasis on mechanical modifications and its performance near the human body. Additionally, the Specific Absorption Rate (SAR) values are evaluated and found to be within the safety limits, ensuring the antenna's compliance with electromagnetic radiation exposure standards. The proposed antenna design has a wide bandwidth, compact size, and optimal performance, outperforming other fractal designs with a simpler geometry and fewer iterations, making it an excellent candidate for 5G communication systems and wearable devices.