Low loss slow-wave unit based on even-mode bilateral broadside-coupled suspended microstrip line

This paper presents a low loss slow-wave meander-line unit for frequency scanning antennas based on the even-mode bilateral broadside-coupled suspended microstrip line (BSML). By symmetrically printing metal strips on both sides of the substrate and by biasing an equi-voltage to both of them, the even mode of BSML is excited and this transmission line exhibits very low loss. The losses in straight microstrip line (MSL), suspended substrate stripline (SSS) and the even-mode BSML have been investigated and compared. A low loss slow-wave meander-line unit for phase shifting has been fabricated and measured. The advantage of the very low loss is remarkable.