Power amplification and coupling circuit with transformer line

Abstract

An apparatus, system and method may include a coupler obeying an equation of a Doherty amplifier, comprising: an input port of a quarter wavelength transformer line having impedance R1; an output port of the quarter wavelength transformer line having impedance R2, wherein the input port and the output port are ends of a main signal line for amplification; a coupling port for providing feedback having impedance R3; and a loaded, isolated port impedance, R4. The amplification obeys the Doherty equation, thereby defining R1 and R2, and R3 and R4 define the coupling, such that: R1/R2=R3/R4. A length allocation of transformer lines that provide the coupling is one quarter wavelength, in order to provide a phase difference between impedances R3 and R4 of 90 degrees. Reflected coefficients are less than minus 20 dB, and directivity is at least 30 dB.

Dependencies are inferred from the claim text.