Impedance Matching Techniques For Antennas

Although antennas come in a variety of shapes and sizes, they have one thing in common: they need to have impedance matching enforced at the end of the feedline to ensure maximum power transfer into the load. Impedance matching circuits are rather simple; they act like filters that ensure an antenna’s feedline impedance matches the input impedance at the input port of the antenna. Starting from a filtration perspective is the easiest impedance matching technique in antennas or other RF circuit elements. 

Impedance Matching Techniques in Antennas: Defining Impedance Matching Requirements

The need for impedance matching techniques in antennas comes from the fact that antenna impedances are not always 50 Ohms. Some antennas, such as chip antennas, have either low or high impedance when fabricated. For other antennas, such as a printed antenna, it may be difficult to design the antenna to perfectly hit a 50 Ohm target impedance; the traces might be very wide or the antenna may take up board space. The result is that the design needs to be fabricated smaller, which creates an impedance mismatch.