An Efficiency-Enhanced High-Gain Large-Element Array for 220-GHz Band Applications

Compared to small radiating elements, large elements can reduce the stages and the losses of power dividers (PDs) within the same array aperture, significantly enhancing the array’s radiation efficiency. However, it faces the grating lobe challenge when they are formed into an array. This article investigates the factors that affect the rectangular lattice large-element array’s sidelobe levels (SLLs). Results show that the sidelobes are independent of element spacing but closely related to aperture efficiency (AE) and array scale. The element’s AE and number in the arraying dimension are suggested to be at least 82% and 4, respectively. The lens is selected as the large element’s architecture because its optimized feed and phase-shifting surface make it relatively easy to achieve a higher field uniformity, that is, a higher AE. Methods for extracting the 1-D aperture efficiencies of a 2-D region are proposed in this article to validate the derived SLL rules in full-wave simulations, and a simplified form is employed for the rapid optimization of architectural parameters. Finally, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> scale high AE lens array is designed with an element size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6\lambda _{0} \times 10\lambda _{0}$ </tex-math></inline-formula>. The reached directivity at 220 GHz is 39.7 dBi, with AE almost above 70% within the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$170\sim 260$ </tex-math></inline-formula>-GHz band. For the convenience of measurement, a prototype with a 16-way PD is fabricated. The measured peak realized gain is 37 dBi, with a peak total efficiency of 42% and a 3-dB gain bandwidth of 20.7%.