Sub-Arrays using CSRR Loaded Dual-band Microstrip Patch Antennas for MIMO and Phased Array Applications in 6G FR3 Band

In this paper, sub-arrays using a CSRR (complementary split-ring resonator) loaded microstrip patch antennas are proposed for MIMO and phased array applications in 6 G wireless communication systems. The CSRR-loading on the microstrip patch antenna leads to simultaneous miniaturization and dualband performance spanning center-frequencies of 11 GHz and 13 GHz, making the antenna element suitable for operation in the 6G FR3 band advocated by 3GPP. The CSRR-loaded dual-band microstrip patch is used to first realize a $2 \times 2$ subarray (configuration-I) with an inter-element spacing of $0.5 \lambda_{0}$, where $\lambda_{0}$ is the free-space wavelength at 13 GHz, which shows a grating lobe free beam steering up to 80°. The sub-array achieves a satisfactory impedance matching of $\leq-20 \mathrm{~dB}$ and inter-port isolation $\geq 16 \mathrm{~dB}$. Another sub-array (ConfigurationII) is then configured using the dual-band patch and sequential rotation principle for polarization diversity MIMO application. The proposed sub-arrays configurations using CSRR-loaded dualband microstrip patches are further fabricated, and the results are experimentally validated.