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Hybrid CouplerSheet 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

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