A Doherty amplifier includes: a first amplifying element to amplify a first signal; a second amplifying element to amplify a second signal having a phase difference with the first signal; a first transmission line connected to an output terminal of the first amplifying element; and a second transmission line connected to an output terminal of the second amplifying element, wherein the first transmission line and the second transmission line are equal to each other in characteristic impedance, the phase difference between the first signal and the second signal is not equal to a difference in electrical length between the second transmission line and the first transmission line, and the first signal having passed through the first transmission line and the second signal having passed through the second transmission line are subjected to different phase synthesis.

Apparatus and methods for quadrature combined Doherty amplifiers are provided herein. In certain embodiments, a separator is used to separate a radio frequency (RF) input signal into a plurality of input signal components that are amplified by a pair of Doherty amplifiers operating in quadrature. Additionally, a combiner is used to combine a plurality of output signal components generated by the pair of Doherty amplifiers, thereby generating an RF output signal exhibiting quadrature balancing.

An RF power amplifier is described including a first amplifier and a second amplifier arranged in parallel between an RF power amplifier input and an RF power amplifier output. A phase adjuster adjusts the phase of a signal on at least one of the first amplifier signal path and the second amplifier signal path. A first impedance inverter has a first impedance inverter input coupled to an output of the second amplifier and a first impedance inverter output coupled to the RF power amplifier output. The RF power amplifier is configured to enable at least one of the first amplifier and the second amplifier dependent on an operation mode and the first impedance inverter is configured to modulate the load impedance of the second amplifier in response to the operation mode changing.

A power amplifier arrangement (200) for amplifying an input signal to produce an output signal comprises a plurality N of amplifier sections (212, 213), a first input transmission line (221) comprising multiple segments and a first output transmission line (231) comprising multiple segments. Each amplifier section comprises one or more first transistors (T1) distributed along the first input transmission line (221) and the first output transmission line (231). Each amplifier section is configured to amplify a portion of the input signal to produce a portion of the output signal. A portion of the input signal is one of N portions of the input signal partitioned on any one or a combination of an amplitude basis and a time basis. The output signal is produced at an end of the first output transmission line (231) by building up N potions of the output signal from each amplifier section.

Antenna waveguide transitions for solid state power amplifiers (SSPAs) are disclosed. An SSPA includes a waveguide channel that is configured to propagate an input signal, such as an electromagnetic signal, from an input port to a solid state amplifier for amplification. The waveguide channel is further configured to propagate an amplified signal from the solid state amplifier to an output port. Waveguide transitions to and from the solid state amplifier are bandwidth matched to the waveguide channel. Additionally, the waveguide transitions may be thermally coupled to the waveguide channel. The waveguide transitions may include antenna structures that have a signal conductor and a ground conductor. In this manner, the SSPA may have improved broadband coupling as well as improved thermal dissipation for heat generated by the solid state amplifier.

An output matching circuit includes: a converter electrically connected to an output end of a power amplifier element to convert an impedance of the output end to an impedance higher than the impedance of the output end by magnetic coupling; and a first filter circuit electrically connected between the output end of the power amplifier element and the converter to make a short circuit in a frequency band different from a predetermined transmission frequency band.

Example embodiments relate to push-pull class E amplifiers. One example push-pull class E amplifier includes an input configured for receiving a signal to be amplified. The push-pull class E amplifier also includes an output configured for outputting the signal after amplification. Additionally, the push-pull class E amplifier includes a printed circuit board having a first dielectric layer and a second dielectric layer. Further, the push-pull class E amplifier includes a first amplifying unit and a second amplifying unit. Yet further, the push-pull class E amplifier includes a balun, a capacitive unit, a first line segment, a second line segment, a third line segment, and a fourth line segment. The first line segment and the second line segment are arranged on the first dielectric layer. A combined length of the third line segment and the fourth line segment corresponds to a quarter wavelength of an operational frequency of the amplifier.

Example embodiments relate to push-pull class E amplifiers. One example push-pull class E amplifier includes an input configured for receiving a signal to be amplified. The push-pull class E amplifier also includes an output configured for outputting the signal after amplification. Additionally, the push-pull class E amplifier includes a printed circuit board having a first dielectric layer and a second dielectric layer. Further, the push-pull class E amplifier includes a first amplifying unit and a second amplifying unit. Yet further, the push-pull class E amplifier includes a balun, a capacitive unit, a first line segment, a second line segment, a third line segment, and a fourth line segment. The first line segment and the second line segment are arranged on the first dielectric layer. A combined length of the third line segment and the fourth line segment corresponds to a quarter wavelength of an operational frequency of the amplifier.

A microwave amplifier having a load network which provides more efficient amplification of a low power microwave frequency signal. The amplifier comprises a transistor and a load network coupled to the transistor output to shape a waveform of an amplified microwave signal at the transistor current source plane. The load network comprises: a fundamental matching network to provide impedance matching at a fundamental frequency; a half-wave transmission line for a second harmonic frequency disposed between the transistor output and the fundamental matching network; a quarter-wave stub and a five-quarter-wave stub for a third harmonic frequency arranged on the half-wave transmission line to provide an open circuit condition at the third harmonic; and a quarter-wave stub for the second harmonic frequency and a quarter-wave stub for the fundamental frequency, arranged on the half-wave transmission line to provide a short circuit condition at the second harmonic frequency.

A MIM capacitor is included in any one or more of a first matching circuit and a second matching circuit. The mat capacitor performs impedance matching of a fundamental wave included in a high-frequency signal with a transmission line, and forms a short-circuit point for a harmonic included in the high-frequency signal at a connection point with the transmission line.