CLCoupler (Coupled-Line Coupler)

Symbol

Parameters

Name	Description	Unit	Default
Subst	Microstrip substrate name	None	MSub1
F	Center frequency	GHz	1
C	Coupling coefficient	dB	20
Zo	Characteristic impedance	Ohm	50
N	Number of coupler sections (N is odd)	None	1
Delta	Length added to branches for tuning performance	mil	0

Notes

1. A coupled-line coupler outputs from the coupled port (pin 4) a fraction of the power presented at the input (pin 1). The remainder of the power is passed through to the output port (pin 2). The coupling coefficient specifies the ratio of the input power to the coupled power (P ₁ /P ₄ ). The remaining port is isolated, although the isolation is often similar in value to the coupling coefficient for microstrip realizations.
2. The optimization minimizes the absolute difference between S41 in dB and the specified coupling coefficient at the design center frequency by changing the length of the coupled-line section.
3. The coupling coefficient must be positive and greater than 3 dB. Best results are obtained for weak couplings of roughly 10 dB or more (C >10dB). Choosing the coupling coefficient too small can require a spacing between the coupled lines too small to realize.
4. A SmartComponent subnetwork is empty until the Design Assistant is used to generate the design. Refer to Design Assistant.

For a more detailed discussion of this device, see: D. M. Pozar, Microwave Engineering, 2nd Edition, John Wiley & Sons: New York, 1998, pp. 383-394.

Example

A coupled-line coupler was designed for a center frequency of 5 GHz with 20 dB of coupling. Tuning using the Optimization Assistant yielded a value of Delta =-1.087 mil.