SSMatch (Single-Stub Match)

Symbol

Parameters

Name	Description	Unit	Default
Subst	Microstrip substrate name	None	MSub1
F	Center frequency	GHz	1
Zin	Desired complex input impedance	Ohm	50
Zload	Complex load impedance to match	Ohm	100
Zstub	Characteristic impedance of stub line	Ohm	50
Zline	Characteristic impedance of line	Ohm	50
Zfeed	Characteristic impedance of line connected to port 1 or 2	Ohm	50
StubType	Stub type (open or short circuit)	Open Circuit
NetType	Network type (source to load)	Automatic
Delta	Length added to stub for tuning performance	mil	0

Notes

1. A single-stub matching network matches a complex load impedance (Zload) to a desired complex input impedance (Zin) using a single shunt stub and length of line.
2. The parameter NetType can be Automatic, stub-line, or line-stub, with the latter two choices representing configurations that have a stub followed by a line or vice-versa as the network is observed from source to load. Many impedance combinations can be realized using both possible types, although some can only be realized using one of the two choices. Choosing Automatic will ensure a realizable choice is given.
3. An impedance match can be realized using either stub type.
4. Zline represents the impedance of the line either next to the source or load (depending on the value of NetType). Zfeed represents the desired impedance on the other side of the stub from the line and is used to ensure that the corresponding leg of the microstrip tee component is of the proper width.
5. MTEE component width constraint violations will be avoided generally by choosing similar characteristic impedances for the line, stub, and feed.
6. The input port termination is set to the conjugate of Zin so that the ideal input reflection coefficient will be zero. The output port termination is set to Zload.
7. The optimization minimizes the value of S11 (referenced to the conjugate of Zin) at the design center frequency by changing the length of the stub.
8. 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. 258-266.

Example

A single-stub matching network was designed to match a load impedance of 100 - j25 Ohms to a 50 Ohms line at a center frequency of 2GHz. Choosing an open-circuit stub with automatic selection of the NetType resulted in a stub-line configuration. Tuning using the Optimization Assistant yielded a value of Delta =-5.078 mil.