A Slot-Mode SIW Glide-Symmetry Periodic Leaky Wave Antenna With Suppression of Two Stopbands and Grating Lobe

This article proposes a new slot-mode substrate integrated waveguide (SIW) periodic leaky wave antenna (PLWA) with glide-symmetry (GS). The scanning range of a PLWA is generally limited by two stopbands (the open stopband at the broadside and the next coming stopband in the forward quadrant) and the grating lobe (caused by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n= -2$ </tex-math></inline-formula> space harmonic). To suppress the two stopbands and the grating lobe, we propose and investigate a novel PLWA based on GS unit cells, in which each unit cell consists of two identical sub-unit cells, with each sub-unit cell containing two nonidentical slots. The two nonidentical slots are adopted to suppress the open stopband by quarter-wavelength impedance matching, while the unit cell with GS is employed to suppress the next coming stopband by three-quarter-wavelength impedance matching. Additionally, the antenna with GS avoids the next coming stopband and the grating lobe by directly suppressing the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n= -2$ </tex-math></inline-formula> space harmonic. With the simultaneous suppression of he two stopbands and the grating lobe, the PLWA generates a single beam that continuously scans from the near backward to forward endfire directions. A prototype of the proposed antenna with a broadband feeding network is fabricated and measured for validation.