PIN-Switched Series Feed for Frequency- and Pattern-Reconfigurable MIMO Antenna Using Merged SRR, SIW, and Symmetric Slit Extensions

This paper proposes a frequency-reconfigurable (FR) and pattern-reconfigurable (PR) multiple-input and multiple-output (MIMO) antenna. Recent research has focused on MIMO antennas that can operate in multiple reconfigurable modes and many functions in a single construction. This proposed MIMO antenna reconfigures both the frequency and pattern. This novel FR-PR MIMO antenna element uses symmetric slit extensions in a patch to produce two radiating regions (primary patch and secondary patch). A PIN diode controls the feed current and reconfigures antenna elements as the primary patch feeds the secondary patch in series. A new merged split ring resonator and substrate-integrated waveguide structure are used in this design to enhance field confinement, improve inter-element isolation, and achieve radiation patterns with high gain and minimal distortion. The proposed MIMO antenna offers FR and stable planar antipodal radiating patterns at 3.82 GHz and 2.36 GHz. The proposed MIMO achieves isolation (> 20 dB) and offers gain values of 5.9 dBi and 6.4 dBi in two switchable frequency modes. The envelope correlation coefficient (ECC) calculated from both far-field and S parameter is less than 0.2, and diversity gain (DG) is 9.8 dB. The average channel capacity loss is less than 0.45 bits/s/Hz across the whole band, which ensures better performance from the MIMO antenna. The total active reflection coefficient values are less than -10 dB across the entire band. Mean effective gain ratios are closer to 1, proving that the proposed antenna MIMO system has better diversity performance, especially in highly challenging channels with a lot of multipath fading. The simulated and measured performances of the reflection coefficient and radiation patterns exhibit excellent agreement. The MIMO antenna beat the design complexity-performance trade-off.