Efficient Millimeter-Wave Antenna Based on the Exploitation of Microstrip Line Discontinuity Radiation

In this paper, a new design perspective utilizes microstrip line discontinuities radiation losses to create an efficient, high-gain millimeter-wave low-profile antenna at 60 GHz. A very compact structure with dimensions of 1.14 λ_o × 0.82 λ_o and a substrate thickness of 0.0508 λ_o is proposed. A gain of 11.5 dBi boresight and a 10 dB return loss relative bandwidth of 3.66% (equivalent to 2.2 GHz of bandwidth) have been achieved. Qualitative analysis with simple transmission line theory was used to model the structure. An increase in the relative bandwidth to 11.67%, covering the 60 GHz ISM band (57-64 GHz), has been achieved by tuning the antenna to resonate at multiple resonances within the band of interest. A very high efficiency of 98% has been achieved. The proposed antenna possesses a significant advantage, where it can be employed in a linear antenna array, with a center-to-center distance between adjacent elements greater than half of the free-space wavelength, without producing grating lobes, this reflects positively on reducing the mutual coupling between elements, and gives higher flexibility in the design of feeding network.