140-GHz ${\rm TE}_{20}$-Mode Dielectric-Loaded SIW Slot Antenna Array in LTCC

A ${\rm TE}_{20}$ -mode substrate integrated waveguide (SIW) fed slot antenna array is proposed at 140 GHz for fabrication ease and cost reduction. The antenna array consists of a feeding network, radiators, and dielectric loadings. The proposed antenna array and an SIW-waveguide transition are integrated into the multilayered low-temperature co-fired ceramic (LTCC). The feeding network comprises a power divider and $E$ -plane couplers that support the ${\rm TE}_{20}$ mode. Each pair of symmetrical longitudinal radiating slots is fed by the ${\rm TE}_{20}$ mode in a doubled-width SIW. The pair of radiating slots is loaded by a doubled-width open-ended via-fence structure in which a higher order mode is also excited. Experimental results show that an 8 $\times$ 8 slot array with the transition achieves a maximum boresight gain of 21.3 dBi at 140.6 GHz and an impedance matching bandwidth of 129.2–146 GHz with a boresight gain above 18.3 dBi.