Stub tuners are simple to implement and cheap to manufacture: they only require more of the same material used to make the transmission line. The image below depicts the basic layout of stub tuners from Pozar's Microwave Design: This occurs by placing a specific length of stub a specific distance away from the load. Stub tuning is one method that satisfies both of these criteria stub tuning is simply the process of adding a length of transmission line to the existing length in either series, shunt, open circuit, or short circuit configuration to match the line to the load. This can be accomplished using a variety of different methods and components, each suited towards specific applications. This of course leads to the inevitable and age-old dilemma of the engineer where we will have to balance the best possible solution with the cheapest possible implementation. In RF engineering, it is critical to have a waveguide line matched to its load this minimizes signal loss, maximizes power handling, and ultimately will give the best performance out of any given RF circuit. Learn the secrets to becoming a stub tuning wizard. Having the ability to design these matching circuits on the fly can be very handy if you ever find yourself working in the RF field both because it can be faster than calculation, as well as being a great tool for visualizing what is going on.

Overview of stub tuning examples using the Smith chart to match RF lines to various loads.

Smith chart series shunt