In this paper, a new miniature size microstrip antenna design with defected ground structure (DGS) based on the complementary split ring resonator (CSRR) element is proposed for sub-6 GHz 5 G wireless cellular networks. The miniature antenna design is of dimensions 16 mm \(\times\) 16 mm with an electrical size of 0.18 \(\lambda _0\) \(\times\) 0.18 \(\lambda _0\) at 3.5 GHz. The proposed antenna design consists of a stepped microstrip line fed circular patch placed on a CSRR-DGS backed dielectric substrate ( \(\varepsilon _r\) = 2.2). Numerical analysis and measurement results of the proposed CSRR-DGS backed compact circular patch antenna are presented in the paper. By etching a CSRR into the ground plane, the resonant frequency is significantly lowered from 17.3 GHz to 3.5 GHz, achieving a miniaturization ratio of 5.7 and a physical size reduction of 83%. The CSRR-DGS also improves impedance matching and suppresses out-of-band radiation, enabling \(|S_{11}| < -\) 10 dB operation across a 6% bandwidth (3.37 \(-\) 3.58 GHz). The antenna is fabricated on an Arlon DiClad880 substrate and validated through simulations and measurements. Its compact form factor, sub-6 GHz compatibility, and favorable gain pattern make it highly suitable for integration into next-generation 5 G mobile terminals and IoT devices where physical space is limited.
