Several commonly used devices for obtaining a match at the load end of a transmission line will be described in this chapter. These include the single and the dual matching stub, and the single and the dual matching slug transformers. Matching stubs or building-out sections, as they are sometimes called, are sections of transmission line, frequently of the same characteristic impedance (or characteristic admittance) as that of the main line, and either open or short-circuited at their far end, connected in shunt with the main line at any one of several permissible positions in the general location where it is desired to provide the match. Slug transformers, on the other hand, are sections of line of appropriate characteristic impedance (or characteristic admittance) and length connected in series with, and forming a continuation of, the main line. These devices are described in some detail herein since it is through its terminations alone that the transmission characteristics of waves along any given waveguide can be controlled. Furthermore, the SMITH CHART provides the ideal medium for visualization of the principle of operation of such transformers and for quantitatively determining their specific design constants.

Chapter Contents:

• 9.1 Stub And Slug Transformers
• 9.2 Admittance Matching With A Single Shunt Stub
• 9.2.1 Relationships Between Impedance Mismatch, Matching Stub Length and Location
• 9.2.2 Determination of Matching Stub Length and Location with a Smith Chart
• 9.2.3 Mathematical Determination of Required Stub Length of Specific Characteristic Impedance
• 9.2.4 Determination with a Smith Chart of Required Stub Length of Specific Characteristic Impedance
• 9.3 Mapping of Stub Lengths and Positions on a Smith Chart
• 9.4 Impedance Matching with Two Stubs
• 9.5 Single-slug Transformer Operation and Design
• 9.6 Analysis of Two-slug Transformer with a Smith Chart
• 9.7 Determination of Matchable Impedance Boundary

Inspec keywords: waveguides; charts; transmission line theory; transformers

Other keywords: transmission line; Smith chart; characteristic impedance; dual matching stub; waveguide impedance; dual matching slug transformers; admittance matching; building-out sections

Subjects: Inductors and transformers; Transmission line theory; Waveguides and microwave transmission lines