Study on construction of cost-effective printed circuits at millimeter-wave frequencies

Although the BIT line has a low loss nature at millimeter-wave frequencies, it may be face difficulties such as generation of unwanted modes due to happening to make asymmetrical structures in manufacturing process. For example, the dielectric-supported center conductors may be displaced for the horizontal mid-plane in the parallel metal plate housing, the dielectric substrate being fixed by spacers with slightly-different dimensions, or width of one of two center conductors may be unintentionally trimmed by actual etching. To evaluate increasing dissipation loss due to such asymmetrical structures, degradation of Q-factors was investigated using a BIT line resonator and a technique to overcome such difficulties was proposed using via-holes.