A compact quad-element multiple-input multiple-output (MIMO) antenna design for dual-band operation (38.07 and 42.87 GHz) has been proposed for fifth-generation new radio and mm-wave bands. The overall dimension of the proposed design is \(1.90\lambda _{0}\times \) \(2.53\lambda _{0}\times \) 0.06 \(\lambda _{0}\) (or 15 mm \(\times \) 20 mm \(\times \) 0.508 mm), where \(\lambda _{0}\) represents the wavelength corresponding to 38.07 GHz. The proposed antenna consists of slotted and truncated rectangular patch with H-shaped arms and partial ground structure. Parametric analysis with respect to ground width \((W_g)\) for reflection coefficient and antenna gain has been performed to find the optimum values of \(W_g\) which satisfies the required bandwidth and bands of operation (n259 and n260). The bandwidth achieved by the proposed quad-element MIMO antenna is 12.25 GHz (31.85–44.37 GHz). The isolation achieved by this antenna for the entire band of operation is < -20 dB. Moreover, the proposed design results stable radiation patterns along with high gain of 5.33 dBi and radiation efficiency of > 97%. The different MIMO diversity parameters achieved by the quad-element antenna are < 0.025 for envelope correlation coefficient, 9.99 dB for diversity gain, and < 0.4 bits/s/Hz for channel capacity loss in the entire operating band. The achieved channel capacity has also been analyzed for this design which resulted to \(\approx \) 18.5 bits/s/Hz. Furthermore, the equivalent circuit for the proposed MIMO antenna has also been presented and validated.
