Compact Four‐Port Multiband Circularly Polarized mm‐wave MIMO Antenna for Wearable Biotechnologies, 5G, and Beyond Applications

Abstract This study presents a semi‐flexible and novel unique mallet‐like structure for four‐port multiband multiple‐input multiple‐output (MIMO) antenna with circular polarization (CP). This antenna is useful in the millimeter‐wave (mm‐wave), Ku‐band, and 5G mobile communications band with wearable applications in bio‐technologies. In this work, the on‐body and off‐body scenarios are studied. The off‐body flat antenna is designed for homogeneous space conditions. However, it's on body performance is studied on the surface, i.e., chest and hand. The presented design etched two vertical strips and two thin horizontal strips from ground plane, which is responsible for enhancing the isolation. The radiating elliptical patch attached to the inverted parabolic structure (mace‐like) is responsible for CP. The suggested antenna is fabricated on a Rogers 5880 (tm) substrate of height () 0.787 mm. The overall electrical dimension of the proposed work is 1.01 1.31 0.047 , where is wavelength associated with the lowest resonating frequency of 18 GHz, while the overall physical dimension is 17 22 0.787 mm. The proposed work covers the –10 dB range of frequencies at 16.8–20.84 GHz, 27.10–30.87 GHz, and 31.1–33.83 GHz (off‐body), and 17–20.01 GHz, 26.2–29.98 GHz, and 30.01–33.99 GHz (on‐body). In terms of performance, the antenna achieved peak values of realized gain 8.55, 9.02, and 9.98 dBi and radiation efficiency of 85.5%, 77.7%, and 80.1% respectively at the operating frequencies 18, 28, and 33 GHz. However, the ECC vlues less than 0.034, DG 9.89 dB, and CCL is 0.14 bits/sec/Hz in all the resonating band of frequencies. Moreover, the proposed antenna attains excellent diversity performances when the antenna is evaluated for the on‐body scenario for the chest. In order to guarantee human shielding, specific absorption rate analysis has also been discussed along with the communication link margins (uplink and downlink) to select the input power. The simulated outcomes have good agreement with measured results for on‐body and off‐body performances.