Triple band lateral 4-port flexible MIMO antenna for millimeter wave applications at 24/28/38 GHz

• The proposed low profile antenna produces the triple-band operation at 24 GHz, 28 GHz and 38 GHz. • The antenna achieves port isolation exceeding 20 dB. • The realized gains at 24, 28, and 38 GHz are 5.96 dBi, 6.62 dBi, and 8.48 dBi, respectively, with a radiation efficiency greater than 82% across all bands. • Acceptable SAR values at the three resonant frequencies (24, 28, and 38 GHz) are achieved, with values of 0.1129, 0.4994 and 0.7402 W/Kg at 1 g and 0.0848, 0.2561 and 0.4083 at 10 g, respectively, supporting its use in on-body applications. • To ensure reliable wireless communication, the link margin for this antenna was calculated at each resonance frequency, resulting in values between 42.93 to 62.93, 42.23 to 62.23, and 41.14 to 61.14 dB, respectively. A triple-band, 4-port multiple-input and multiple-output (MIMO) antenna in a linear configuration has been designed and fabricated for millimeter wave (mmWave) wearable applications. The proposed design uses a flexible substrate (Rogers RO3003) with antenna dimension of 14.5 × 48.0 × 0.25 mm 3 . Its radiating structure features a rectangular slot within a circular patch, encircled by eight small, coalesced disc patches. This design supports three prominent frequency bands at 24, 28, and 38 GHz. The antenna achieves port isolation exceeding 20 dB, owing to the inverted configuration of the radiating patch in the MIMO layout. Realized gains at 24, 28, and 38 GHz are 5.96 dBi, 6.62 dBi, and 8.48 dBi, respectively, with a radiation efficiency greater than 82% across all bands. Diversity parameters indicate excellent antenna performance with envelope correlation coefficient (ECC) < 0.046, channel capacity loss (CCL) < 0.32 bits/sec/Hz, and diversity gain (DG) > 9.95 dBi across the operating frequencies. The antenna's S-parameters are also analyzed under various bending conditions, confirming its suitability for wearable applications. Acceptable specific absorption rate (SAR) values at the three resonant frequencies (24, 28, and 38 GHz) are achieved, with values of 0.1129, 0.4994 and 0.7402 W/Kg at 1 g and 0.0848, 0.2561 and 0.4083 at 10 g, respectively, supporting its use in on-body applications. Finally, to ensure reliable wireless communication, the link margin for this antenna was calculated at each resonance frequency, resulting in values between 42.93 to 62.93, 42.23 to 62.23, and 41.14 to 61.14 dB, respectively.