Hybrid chireix/doherty amplifiers power waveform synthesis

TLDR: In this article, a coupler couples the first and second amplifiers to one another and to a load impedance, such that voltages or currents in the first amplifier become linearly related to voltages in the second amplifier.

Abstract: Two amplifiers that are driven using outphasing modulation are coupled to one another so that the amplifiers affect each other's effective load line. The two amplifiers can maintain efficiency over a wider dynamic range than in a conventional amplifier. Amplifiers according to the invention amplify an AC input signal of varying amplitude and varying phase using a DC power supply. A converter converts the AC input signal into a first signal having constant amplitude and a first phase angle and into a second signal having constant amplitude and a second phase angle. The first amplifier amplifies the first signal, and the second amplifier amplifies the second signal. A coupler couples the first and second amplifiers to one another and to a load impedance, such that voltages or currents in the first amplifier become linearly related to voltages or currents in the second amplifier. The coupler may include at least one transformer that serially couples the first and second amplifiers to one another and to the load impedance. The coupler may also include first and second quarter wave transmission lines that couple the first and second amplifiers to one another and to the load impedance. The amplifiers preferably use bilateral devices, such that current flows from the first and second amplifiers to the DC power supply during a part of a signal cycle, and thereby returns energy to the DC power supply. Each of the more than two signals of constant amplitude and controlled phase is then separately amplified in separate amplifiers. The separately amplified more than two signals of constant amplitude and controlled phase are then combined to produce an output signal that is an amplification of the input signal at the desired power level. When converting the input signal into more than two signals, the phase of each of the more than two signals of constant amplitude and controlled phase is controlled to produce the output signal that is an amplification of the input signal at the desired power level. According to another aspect, a signal of varying amplitude and varying phase is generated from a plurality of constant amplitude varying phase signals, the sum of which is the signal of varying amplitude and varying phase. An IQ waveform generator generates a cosine carrier modulation waveform I(t) and a sine carrier modulation waveform Q(t) from the signal of varying amplitude and varying phase. A function generator generates a complementary waveform Q'(t) from the cosine carrier modulation waveform I(t) such that the sum of squares of I(t) and Q'(t) is constant. A first modulator modulates a cosine carrier signal with I(t) to obtain a first modulated cosine carrier. A second modulator modulates a sine carrier signal with Q'(t) to obtain a first modulated sine carrier. A circuit such as a butterly circuit forms the sum and difference of the first modulated cosine carrier and the first modulated sine carrier to obtain the constant amplitude varying phase signals.