A Single-Layer Wideband Differential-Fed Microstrip Patch Antenna With Complementary Split-Ring Resonators Loaded

In this paper, a single-layer wideband differential-fed microstrip patch antenna (DMPA) with complementary split-ring resonators (CSRRs) loaded is proposed. First, a quarter-wave microstrip-line resonator is introduced as a capacitive coupling feeding structure which can generate a non-radiative resonant mode. Second, a set of rectangular parasitic patches is loaded co-planarly along the non-radiative edges of the DMPA. Thus, a parasitic radiative mode at the high side of the operation band is added. Meanwhile, with this arrangement, the field distribution of the DMPA has also changed, and a radiation null at high band edge is formed. Then, a pair of CSRRs is etched on the ground beneath the feeding lines, which has compensated the mismatched impedance of the DMAP at the low side of the operation band. As a result, the low-frequency bandwidth is significantly increased. Finally, the proposed antenna is fabricated and measured, and the measured results are in good agreement with the simulation ones. The measured bandwidth of the proposed antenna is ranged from 5.35 GHz to 7 GHz (about 26.7%) while keeping a low profile of 0.051 lambda (lambda is the free-space wavelength at the center frequency) without any air gaps. Besides, the broadside gain is from 7.7 dBi to 10.7 dBi.