HybridSheet 1 of 13
(1) BranchLine Coupler - Quadrature
Zo 2
Zo λ/4 90°
NOTE This device is sensitive to load mismatches. (2) Lange Coupler (Quadrature)
Output φ90°
Coupled
Broadband coupling 3dB → ≈20dB Quadrature
λ/4 Input Directive
To calculate the finger dimensions and spacings, we need to calculate the even and odd mode line impedances:-
C = 10
Coupling coefficien t 20
Z 0e =
4C 3 + 9 8C 2 2C (1 C ) /(1 + C ) 4C + 3 9 8C 2 2C (1 + C ) /(1 C )
Z0
Z 0o =
Z0
Armed with these line impedances the finger widths and spacings can be read from the graph plotting coupled micro-strip line data against even and odd mode line impedances.
1
Sheet 2 of 13
Even and odd-mode characteristic impedance design data for coupled micro-strip lines. Example Lange coupler for use at 7.5GHz……
