In this paper, a high-gain THz antenna array is presented. The array uses a polyimide substrate with a thickness of 10 $\mathsf{\mu }$m, a relative permittivity of 3.5, and an overall volume of 2920 $\mathsf{\mu }$m × 1055 $\mathsf{\mu }$m × 10 $\mathsf{\mu }$m, which can be employed for THz band space communication and other interesting applications. The dual-band single-element antenna is designed in four steps, while operating at 0.714 and 0.7412 THz with −10 dB bandwidths of 4.71 and 3.13 GHz, providing gain of 5.14 and 5 dB, respectively. In order to achieve a high gain, multiple order antenna arrays are designed such as the 2 × 1 antenna array and the 4 × 1 antenna array, named type B and C, respectively. The gain and directivity of the proposed type C THz antenna array are 12.5 and 11.23 dB, and 12.532 and 11.625 dBi at 0.714 and 0.7412 THz, with 99.76 and 96.6% radiation efficiency, respectively. For justification purposes, the simulations of the type B antenna are carried out in two simulators such as the CST microwave studio (CSTMWS) and the advance design system (ADS), and the performance of the type B antenna is compared with an equivalent circuit model on the bases of return loss, resulting in strong agreement. Furthermore, the parametric analysis for the type C antenna is done on the basis of separation among the radiating elements in the range 513 to 553 $\mathsf{\mu }$m. A 64 × 1 antenna array is used to achieve possible gains of 23.8 and 24.1 dB, and directivity of 24.2 and 24.5 dBi with good efficiencies of about 91.66 and 90.35% at 0.7085 and 0.75225 THz, respectively, while the 128 × 1 antenna array provides a gain of 26.8 and 27.2 dB, and directivity of 27.2 and 27.7 dBi with good efficiency of 91.66 and 90.35% at 0.7085 and 0.75225 THz, respectively. All the results achieved in this manuscript ensure the proposed design is a feasible candidate for high-speed and free space wireless communication systems.

A low form-factor design of an eight-element antenna array is presented for 5G mm-wave MIMO applications. The design features modified circular patch radiators that achieve an impedance bandwidth of 2.6 GHz, covering frequencies from 37.7 to 40.3 GHz. The radiating elements are strategically arranged on opposite sides of a common substrate and interleaved to significantly reduce mutual coupling between adjacent elements. This innovative technique effectively minimizes coupling between the array’s radiators without the need of a decoupling structure. The MIMO antenna is fabricated on a low-loss Rogers-5880 substrate, with a thickness of 0.8 mm, a dielectric constant of 2.2, and a loss tangent of 0.0009, ensuring minimal signal loss and confirming the accuracy of simulation results. The inter-element isolation exceeds 25 dB, and the array provides a gain greater than 6 dBi, with a peak gain of 7.5 dBi at 39 GHz. This high gain enhances the antenna’s ability to mitigate atmospheric attenuation at higher frequencies, making it highly suitable for 5G mm-wave applications.

A compact fork‐shaped MIMO antenna system with a 2 × 2 arrangement with four elements is presented. The MIMO elements are arranged orthogonally to achieve a small overall size of 36 × 28 mm² and a wide bandwidth for 5G mm‐wave applications. MIMO elements are positioned 4 mm from each corner of the substrate to achieve compact size and minimize coupling. To improve the isolation of the proposed MIMO system, a metamaterial slab is inserted in the middle of the substrate and between radiating elements of the MIMO antenna system, which improves isolation by 10 dB within the whole operating band and achieves maximum isolation of 65 dB at 34.5 GHz. The proposed MIMO system operates in the Ka‐band frequency range of 22–50 GHz with isolation greater than 30 dB and efficiency above 80% across the entire frequency spectrum for 5G communication. Additionally, the performance parameters of MIMO are examined, including diversity gain (DG) and envelope correlation coefficient (ECC), and it is found that they meet the required standards of DG approximately equal to 10 and ECC < 0.05. The proposed MIMO system has been fabricated and tested. The measured results are consistent with the design of the simulated structure using the CST Microwave Studio (CSTMWS) simulator.

This paper presents a novel, low-cost, compact sensor that integrates a double-negative (DNG) metamaterial with an artificial magnetic conductor (AMC)-backed microstrip patch antenna, specifically optimized for high-precision biomedical applications in the 2–4 GHz range. Unlike prior designs, the proposed sensor leverages the simultaneous negative permittivity and permeability of the DNG structure together with the AMC layer to achieve enhanced gain, directionality, and sensitivity—key performance factors for GHz-range diagnostics. Fabricated on a cost-effective FR4 substrate with a compact footprint of 50 × 50 mm², the sensor is well-suited for scalable, real-world deployment. Full-wave simulations confirm negative refractive index characteristics within the 2.0–2.7 GHz band, and a peak gain of 7.6 dBi is achieved, surpassing comparable designs. Experimental validation in an anechoic chamber shows excellent agreement with simulation results. Benchmarking demonstrates that the sensor outperforms state-of-the-art counterparts in gain, size, and directional response. These features make it a strong candidate for biomedical applications such as wearable health monitoring, portable medical imaging, and non-invasive diagnostics including early-stage brain abnormality detection.