Characteristics of Broadside Coupled Suspended and Inverted Slotlines for Microwave and Millimeter Wave Applications

Abstract

The impedance and dispersion characteristics of shielded, broadside coupled, suspended and—inverted-slotlines are investigated. Spectral domain formulation is used for the analysis. Numerical results are reported for each of these slotline configurations in two different sizes of shielded enclosures—namely, a standard rectangular waveguide at Ka-band and a square waveguide with twice the height of the Ka-band guide. It is found that in all the cases, the propagation constant of the even mode is less sensitive to variation in the air gap (between the substrates) as compared with that for the odd mode. Furthermore, for small air gaps, the variation in the odd mode propagation constant as a function of air gap is rather small in the case of broadside coupled inverted slotline as compared with that in a corresponding broadside coupled suspended slotline.

Indexing terms:

• Suspended slotlines
• Dispersion
• Impedance
• Broadside coupling