Analysis and design of quad-band four-section transmission line impedance transformer

The design of four-section transmission line matching transformer, operating at four arbitrary frequencies, is presented. Standard transmission line theory is used to obtain a closed form expression that is solved using particle swarm optimization technique to find the required transformer parameters (lengths, and characteristic impedances). Different examples are presented which validate the design approach. To further validate the analysis and design approach, a microstrip line four-section quad-band transmission line transformer is designed, analyzed, fabricated and measured.