The Characteristic Impedance and Coupling Coefficient of Coupled Rectangular Strips in a Waveguide

The effect of both the ground planes and sidewalls on the characteristic impedance and coupling coefficient of two coupled strip-Iines are investigated. Numerical results are given that should aid in the design of miniature directional couplers where the sidewalls are close enough to the strips to have a large effect. It is shown, for example, that the coupling coefficient can be varied as a function of distance to enhance the bandwidth, while the impedance can he maintained constant to improve the directivity.