A low-profile wideband antenna loaded with CLS structures for sub-terahertz applications of 6G

In this paper, an arrow-shaped CLS (capacitively loaded strips) structure with a truncated head is inserted between two trapezoid-shaped CLS structures to get a wideband response in the low-frequency region. When the CLS structure without the arrow-shaped structure is excited, a low-frequency resonance is obtained with a 35 GHz bandwidth only. But when the combination is excited by an appropriate feeding network, a low-frequency resonance with a very large bandwidth of about 223 GHz is achieved in the sub-terahertz region of 6G. This combination also causes an unwanted spike-like resonance at low frequency. A T-shaped structure is added to the truncated arrowhead to notch this unnecessary spike. In addition, this structure shifts the lower cutoff frequency by 6 GHz. Simulation results show that the proposed antenna shows a fractional operating bandwidth of 87.24 % from 148 GHz to 377 GHz for |S11| <-10 dB, where a peak realized gain of 4.54 dBi is observed. The antenna also achieves a good bandwidth to dimension ratio of about 995.71. The overall dimension of the antenna is 600 µm × 600 µm × 10 µm, where the height is only 0.005λ, where λ is the operating wavelength at the lower cut-off frequency