A CSRR Loaded Triple-Band Microstrip Patch Antenna with Suppressed Higher Order Modes for Sub-6 GHz Phased Array Application

In this paper, we design a CSRR loaded tripe band antenna with suppressed higher order modes. The CSRR loading is incorporated in a square microstrip antenna such that in addition to the triple band response at 3.52 GHz, 3.865 GHz, 4.39 GHz, antenna miniaturization is obtained yielding an overall footprint of $0.23\lambda_{0}\times 0.23\lambda_{0}$, where $\lambda_{0}$ is the free space wavelength at 3.52 GHz. Further, the higher order mode suppression is achieved using a plated through hole (PTH) placed close to the CSRR loading position. The proposed antenna achieves satisfactory impedance matching $\leq -15$ dB for all three operating frequencies. Further, the proposed antenna is arranged in $4\times 4$ configuration with an inter-element spacing of $0.25\lambda_{0}$ for phased array application. This $4\times 4$ array configuration enables beam steering up to $80^{0}$ without grating lobes, while maintaining lowest side lobe level $\geq 19\mathbf{dB}$ and satisfactory array gains of 12 dBi, 13 dBi, 14 dBi at 3.52 GHz, 3.865 GHz, and 4.39 GHz respectively are achieved. The proposed concept is experimentally validated by S-parameter and pattern measurements on fabricated prototype.