From Electronic Applications of the Smith Chart: In Waveguide, Circuit, and Component Analysis

9.1 Stub and Slug Transformers

As discussed in previous chapters, a mismatch between the load impedance and the characteristic impedance (or between the load admittance and the characteristic admittance) of a waveguide or transmission line causes a reflection loss at the load and increased dissipative losses along the entire length of the line. Also, a mismatch termination causes the transmission phase to vary nonlinearly with changes in frequency or line length, and increases the tendency of the waveguide or line to overheat and arc over at the current and voltage maximum points, respectively, when operating under high power.

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 [65], 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...

Copyright Noble Publishing Corporation 2000 under license agreement with Books24x7

Products & Services
Signal Transformers
Signal transformers transfer information from one circuit to another by electromagnetic induction. They are used to increase or decrease the voltage from one side of a power transformer to the other.
RF Waveguide Couplers
RF waveguide couplers are RF circuits used to sample RF frequency transmissions by coupling (combining) signals asymmetrically.
Waveguide Rotary Joints
Waveguide rotary joints (WRJ) are waveguide components used to transmit microwave energy from stationary lines to rotating lines. They are also known as rotating couplers and RF rotary joints.
RF Adapters
RF adapters are used to connect different waveguides and/or coaxial cables. They are passive devices that direct radio frequency (RF) signals with minimal return loss.
Gate Drive Transformers
Gate drive transformers are used to modify the voltage level to a gate. They also provide impedance matching and voltage isolation.

Topics of Interest

10.1 L-Type Matching Circuits The advantages of matching impedances at a junction between two circuits or media have been pointed out in Chap. 9 and elsewhere in this book and need no further...

1.10 IMPEDANCE MATCHING There are two different concepts of impedance matching in microwave engineering. The first one refers to terminating a transmission line with the characteristic impedance of...

9.11 Transmission Line-Matching Networks Matching with lumped elements Recall the input impedance looking into a T-line varies periodically As shown in Fig. 9.36, move a distance ? 1 away from the...

The use of tables for designing impedance matching filters for real loads is well known [1]. Simple complex loads can often be matched by this technique by incorporating the imaginary portion of the...

Sec 5.1: Introduction Chapter 4 dealt with transformer parameters for working at low-impedance levels; transformers which are basically used to match the ubiquitous 50- ? cable to impedances...