Broadband balun and impedance transformer for push-pull amplifiers

摘要

A balun and transformer system (201) is provided in which a balun (112) is cascaded between two 4:1 impedance transformers (102, 110) to form a 16:1 broadband impedance transformation for push-pull amplifier applications (200). The balun (112) is configured in a Marchand configuration. The balun and transformers (201) are formed with coupled lines realized with a very thin layer of ceramic. Additional coupling between the gap in the balun (112) is achieved by an embedded capacitor (260) built in the balun's ceramic. DC bias supply (294, 296) to the power amplifier (106) is achieved by using the hot plate of decoupling capacitors (298, 299), which serve as a floating ground plane to the whole application (200).