Coplanar Interdigital Coupler
The example documented here is an interdigital coupler using 4 coupled coplanar lines. The schematic of the circuit is shown in Figure 9-17. It shows the use of coplanar airbridges at ports of the coupler. The photo of the realized coupler is shown in Figure 9-18 with some details in region of the used air-bridges. The over-crossing of coupled lines at the ends of coupler and the corresponding capacitance is not taken into account. The simulated and measured S-Parameters of the coupler are plotted in Figures 9-19 and 9-20. A coupling of nearly 4dB could be achieved.
Figure 9-17. Schematic of the Coplanar Interdigital Coupler.
Figure 9-18. Photo of the Coplanar
|Figure 9-19. Insertion loss and coupling of the Coplanar interdigital Coupler.||Figure 9-20. Phase of insertion loss and coupling of the Coplanar interdigital Coupler.|