Loss Reduction by Air-Region Insertion to LTCC Rectangular-Waveguide Slot Array Antenna in the Millimeter-Wave Band

In the millimeter-wave bands, the series-fed array antenna is facing a problem of large transmission loss and narrow bandwidth by using a high permittivity and large-loss tangent material. In this report, an air-layer is inserted in a LTCC waveguide of εr=6.6 and tanδ=0.013 to reduce the transmission loss. The reduction of the equivalent dielectric constant by the air insertion structure enhances both the gain and the bandwidth of the series-fed slot array. We confirm these by measuring the single-mode waveguides and the one-dimensional series-fed slot arrays. The transmission loss of the single-mode rectangular waveguide has been reduced to 1/6 by using the partially-filled structure. The total gain has been enhanced by 8dB. The 3dB bandwidth has also been increased from 1.3GHz to 2.3GHz enhanced in the 60GHz band. Keyword waveguide, LTCC, loss, slot array, millimeter-wave