Abstract
This work presents the design and development of a high-performance frequency-reconfigurable multiple-input multiple-output (MIMO) antenna for the 24 GHz Industrial, Scientific, and Medical (ISM) band, targeting advanced sensing and automotive radar systems. The proposed antenna utilizing a varactor diode to enable agile frequency tuning across a 500 MHz bandwidth (23.8-24.3 GHz), ensuring adaptability to dynamic spectral requirements. The design incorporates four-port MIMO configurations, each integrating a 1×8 microstrip patch array with an optimized split-ring resonator metamaterial absorber. This engineered absorber assessed in suppressing mutual coupling by disrupting surface wave propagation, achieving exceptional inter-port isolation of 38.4 dB and a peak gain of 17.8 dBi at the resonance frequency of 24.12 GHz. Key radiation characteristics include an E-plane beamwidth of 74 and H-plane beamwidth of 11°, coupled with a side-lobe level (SLL) suppressed to −21 dB, ensuring precise directional control and minimal off-axis interference. With an envelope correlation coefficient (ECC) below 0.0004, the antenna demonstrates robust performance in spectral efficiency, diversity gain, and channel capacity. These attributes position the design as a promising solution for high-density wireless environments, offering reconfigurability feature, interference mitigation, and high gain for next-generation of mmWave sensing applications.