“…To our knowledge, no balanced SIW phase shifter has been reported till now. Various single-ended SIW phase shifters have been reported [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ], and their design methods can be categorized as inserted metallic posts [ 12 , 13 , 14 ], buried PIN diodes [ 15 ], embedded omega particles [ 16 ], CSRR-loaded SIW [ 17 ], air-filled SIW loaded with dielectric slab [ 18 ], loaded rod-shaped artificial dielectric slabs [ 19 ], slow-wave structures [ 20 ], slotted SIW [ 21 , 22 ], varactor-loaded slotted SIW [ 23 ], transverse slot coupling [ 24 ], and so on. Among the aforementioned SIW phase shifters, some designs pursue equal lengths of the reference and main lines ([ 12 , 13 , 15 , 17 ]), some designs obtain wide operating bandwidths ([ 14 , 16 , 19 , 20 , 21 ]), some designs attain low insertion loss ([ 18 , 22 ]), and some designs realize tunable phase shift ([ 23 , 24 ]).…”