Evaluating the performance measurement of novel octangular star shaped micromachined substrate with self-isolated 8 × 8 port MIMO antenna for dual band 28 GHz (n261) and 39 GHz (n260) millimeter-wave 5G applications

Abstract

Designing an electromagnetic radiating element that can enhance the capacity of a device operating with multiple frequencies simultaneously, while maintaining its compactness and compatibility with customer premise equipment, is a significant challenge. To tackle this issue, this work proposes a multiple input multiple output (MIMO) antenna with eight elements placed 45° apart on a Rogers 5880 substrate which has been micromachined from sixteen edges with a thickness of 0.252 mm. The substrate measures the area of 717.46 mm² boasting a dielectric constant of 2.2 and loss tangent of 0.0009 with a unique star shape. The slot technique improves the return loss accompanied by defected ground structure to achieve dual-band operation at 28.1 GHz (n261) with the impedance bandwidth from 27.95 to 28.4 (0.45 GHz) and 39.5 GHz (n260) having impedance bandwidth from 38.6 to 40.4(1.8 GHz). The inter-element isolation of more than 60 dB is achieved for both bands with micromachined substrate. The measured gain at 28 GHz is 7dBi and at 39 GHz it is obtained as 7.4dBi. The 8-port MIMO is simulated for all the diversity metrics such as Diversity Gain (DG), Channel Capacity Loss (CCL), Envelope Correlation Coefficient (ECC), Mean Effective Gain, Total Active Reflection Co-efficient (TARC). The parameters evaluated for all eight ports are within the standard values with ECC of < 0.001, DG > 9.99 dB, CCL < 0.1b/s/Hz, and the TARC < − 10 dB. The MIMO has been fabricated and tested for various results which favourably aligned with the simulated results validating the applicability of the proposed mm-Wave 8-port MIMO antenna for practical 5G applications. Furthermore, the 8-port is also simulated for conformality check which showed a minor change in impedance bandwidth at 15°, 30°, and 45°. The Specific Absorption Ratio (SAR) analysis has provided values less than 1.6 W/kg for both the intended bands. The conformal and SAR analysis has added an advantage to the application of the proposed antenna for 5G as well as for wearable on-body applications.