Compact rf power amplifier

A compact RF power amplifier, comprising:

• a Doherty amplifier comprising a carrier amplifier comprising a first input impedance matching unit configured to match input impedance of an input first RF signal, a first amplifier configured to amplify the first RF signal matched by the first input impedance matching unit to a first RF amplified signal, and a first output impedance matching unit configured to match output impedance of the first RF amplified signal, and a peaking amplifier comprising a second input impedance matching unit configured to match input impedance of input second RF signal, a second amplifier configured to amplify the second RF signal matched by the second input impedance matching unit to a second RF amplified signal, and a second output impedance matching unit configured to match output impedance of the second RF amplified signal;
• a first quarter wave transformer connected to the first output impedance matching unit, and configured to maintain the first RF amplified signal with impedance of 50Ω;
• and
• a second quarter wave transformer connected to the first quarter wave transformer and the second output impedance matching unit, and configured to output a third RF signal combined with at least one of the first and second RF amplified signals,
• wherein when a power level of the first RF amplified signal reaches a predetermined power level, the peaking amplifier outputs the second RF amplified signal, and the third RF signal is the same as the first RF amplified signal before the predetermined power level, and is the same as a combined signal of the first and second RF amplified signals after the predetermined power level.