In this paper, a compact dual-band Dolly-shaped antenna (DBDSA), resonating at 23.52 GHz and 28.39 GHz, is proposed for automotive radar, 5G, and Industrial, Scientific, and Medical (ISM) applications. The antenna is designed on a 7 Â 7 Â 1.28 mm 3 which is 0.541λ 0 Â0.541λ 0 Â0.099λ 0 in electric size, where λ 0 represents the free space wavelength at 23.16 GHz. Rogers RO3010 substrate with a dielectric constant of 10.2 and a loss tangent is about 0.0022 has been used. Two F-shaped parasitic elements and a rectangular slot have been used to achieve the desired electromagnetic antenna performances. After modeling and optimizing the proposed antenna configuration through High-Frequency Structure Simulator (HFSS) software, its prototype was manufactured and measured to validate the simulated results. The DBDSA achieves an overall radiation efficiency of 80% within the two operating frequency bands. The radar band exhibits a stable gain of 5.51 dBi, while the 5G band has a gain of 4.55 dBi. Furthermore, the experimental results show that the |S 11 | -10 dB bandwidths are 1.16 GHz (23.16 GHz-24.32 GHz) in the lower band and 634 MHz (28.078 GHz-28.712 GHz), respectively. A good agreement is found between the simulated and measured results.

Achieving antenna size reduction while maintaining high efficiency and multiband characteristics with wide bandwidths across all the operating frequency bands is highly demanded and challenging in microstrip antennas. A novel compact triband quasi‐rho‐shaped and cost‐effective antenna is designed on a 7 × 7 × 1 mm3 FR4 substrate having a permittivity of 4.4 and a loss tangent of 0.02. With an electrical size of 0.39λ0 × 0.39λ0 × 0.056λ0, where λ0 is the free space wavelength at 16.84 GHz, a circular slot and asymmetric microstrip feed are used to achieve the desires performance. The proposed antenna is designed, simulated, and optimized using high‐frequency structure simulator (HFSS) software, and its prototype is fabricated to validate its electromagnetic performance. Furthermore, an equivalent circuit is proposed using the Foster canonical model. The proposed antenna exhibits a maximum stable gain of 5.32 dB and an average radiation efficiency of 77.87% in all the operating frequency bands. The measurement results show that the antenna covers (16.84–18.15 GHz), (24.78–27.40 GHz), and (34.47–37.22 GHz) bands centred at 17.39 GHz, 25.98 GHz, and 35.83 GHz, respectively, with a minimum wide bandwidth (S11 ≤ −10 dB) of 1.31 GHz. The acquired results illustrate that the quasi‐rho‐shaped antenna is suitable for military radars and 5G applications.

In this paper, a quadband MIMO diamond-shaped antenna with two highly isolated elements is proposed and discussed. A novel metamaterial cell-inspired decoupling parasitic structure is deployed between the two antenna elements to achieve high isolation greater than 20 dB in the frequency bands of interest. Moreover, the design adopts a defected ground structure and open-ended multiple diamond-shaped branches for multiband characteristics, enabling the proposed MIMO to cover several modern wireless applications. The performance metrics of the proposed MIMO antenna are validated by evaluating various diversity parameters such as envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and channel capacity loss (CCL). This antenna is fabricated on an FR4 substrate with a compact size of 12 × 30 × 1.524 mm (0.082λ 0 × 0.204λ 0 × 0.001λ 0, λ 0 is the wavelength at 2.04 GHz). With the edge-to-edge separation distance of 0.053λ 0 between the antenna elements, its prototype is experimentally measured using a two-port Rohde & Schwarz ZVA50 Vector Network Analyzer. The port-to-port isolation is about −20.87 dB, −23 dB, −25.93 dB, and −25.22 dB for 2.3 GHz, 3.18 GHz, 4.08 GHz, and 5.42 GHz frequency bands, respectively. Also, the proposed MIMO antenna exhibits good diversity performances with the ECC < 0.005, DG > 9.99, and TARC<−10 dB making it an outstanding candidate covering 4G/LTE, 5G NR sub-6 GHz n40/n41/n77/n78, Wi-Fi, WiMAX, ISM, WBAN, Bluetooth, MBAN, WiBro, C-V2X, and UWB applications.