Unequal Power Divider Based on Inverted Microstrip Gap Waveguide and Its Application for Low Sidelobe Slot Array Antenna at 39 GHz

Abstract

This article presents a novel unequal power divider based on an inverted microstrip gap waveguide. This new geometry can achieve a large power ratio of the two output ports and a small phase difference less than 5°. Based on this novel geometry, a few distinctive unequal power dividers with different output power ratios were proposed for designing a low sidelobe array antenna at 39 GHz. To verify the design, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16\times 16$ </tex-math></inline-formula> antenna array was designed and measured. The measurement results indicate that the entire array antenna achieves a −10 dB impedance bandwidth of 18.5% (in the range of 35.9–43.2 GHz), a gain greater than 29 dBi from 37.5 to 41.8 GHz, and an antenna efficiency greater than 50% over the entire operating frequency band. Based on the application of the newly invented distribution network, the proposed array antenna is below −23 dB on both the E- and H-planes at 37–42 GHz. Furthermore, the radiation pattern of the entire array complies with the European Telecommunications Standards Institute (ETSI)-Class II standard for all azimuth angles.