Bandwidth enhancement of broad-band cavity-coupled microstrip vertical transitions

Techniques to enhance the bandwidth of the broad-band cavity-coupled vertical transitions were proposed in this paper. A nearly 40% increase in bandwidth can be achieved by choosing the bowtie coupling slots and the radial-line tuning stubs. Moreover, the proposed cavity-coupled design example outperforms its corresponding slot-coupled design in the transmission bandwidth of the vertical transitions. In addition to the advantage of offering more bandwidth, the proposed design also reduce the longitudinal dimensions of the coupling slots and the tuning stubs significantly. This character is crucial for modern MMIC applications, which require high density in circuit elements.