A first transmission line and a second transmission line that are connected in series to each other are disposed at different positions in a thickness direction of a substrate. A third transmission line is disposed between the first transmission line and the second transmission line in the thickness direction of the substrate. The third transmission line includes a first end portion connected to one end portion of the first transmission line, and a second end portion that is AC-grounded. The first transmission line and the second transmission line are electromagnetically coupled to the third transmission line.

A Doherty amplifier includes: a first filter circuit to output a first input signal obtained by attenuating an input signal lying in a first frequency band, and to output a second input signal obtained by allowing passage of an input signal lying in a second frequency band; a second filter circuit to output a third input signal obtained by attenuating an input signal lying in the first frequency band, and to output a fourth input signal obtained by attenuating an input signal lying in the second frequency band; a first amplifier to operate as an auxiliary amplifier when receiving the first input signal, and to operate as a main amplifier when receiving the second input signal; and a second amplifier tip operate as the main amplifier when receiving the third input signal, and to operate as the auxiliary amplifier when receiving the fourth input signal.

A stub whose end is connected to an end of a transmission line, and a coupled line disposed in parallel with each of the transmission line and the stub, and electromagnetically coupled to each of the transmission line and the stub are included, and the stub and the coupled line operate as a first resonator for resonating with an odd order harmonic included in the amplified signal, and the transmission line, the stub, and the coupled line operate as a second resonator for resonating with an even order harmonic included in the amplified signal.

A power amplifier module includes a first phase shifter, a second phase shifter, and an electromagnetic shield. The first phase shifter includes a first transmission line assembly to shift a first amplified signal by a first phase angle. The second phase shifter includes a second transmission line assembly to shift a second amplified signal by a second phase angle. The electromagnetic shield is arranged to shield the first transmission line assembly from the second transmission line assembly. The power amplifier module may have, for example, Doherty amplifier configuration.

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 multiple-path amplifier (e.g., a Doherty amplifier) includes a first transistor (e.g., a main amplifier FET), a second transistor (e.g., a peaking amplifier FET), a combining node, and a shunt-inductance circuit. The first and second amplifiers and the combining node structure are integrally-formed with a semiconductor die, and the shunt-inductance circuit is integrated with the die. Outputs of the first and second transistors are electrically coupled to the combining node structure. The shunt-inductance circuit is electrically coupled between the combining node structure and a ground reference node. The shunt-inductance circuit includes a shunt inductance (e.g., including wirebond(s) and/or spiral inductor(s)) that is integrated with the semiconductor die. The multiple-path amplifier also may include an integrated phase shifter/impedance inverter coupled between the outputs of the first and second transistors, and which is configured to impart a 90-degree phase delay between intrinsic drains of the first and second transistors.

A power amplifier circuit includes a power splitter, a first amplifier configured to output a first amplified signal from a first output terminal, and a second amplifier configured to output a second amplified signal from a second output terminal. The power amplifier circuit further includes a first termination circuit connected between the first output terminal and the second output terminal, a first transmission line, a second transmission line, a second termination circuit connected between another end of the first transmission line and another end of the second transmission line, and a power combiner.

An embodiment of a module (e.g., an amplifier module) includes a substrate, a transmission line, and a ground plane height variation structure. The substrate is formed from a plurality of dielectric material layers, and has a mounting surface and a second surface opposite the mounting surface. A plurality of non-overlapping zones is defined at the mounting surface. The transmission line is coupled to the substrate and is located within a first zone of the plurality of non-overlapping zones. The ground plane height variation structure extends from the second surface into the substrate within the first zone. The ground plane height variation structure underlies the transmission line, a portion of the substrate is present between the upper boundary and the transmission line, and the ground plane height variation structure includes a conductive path between an upper boundary of the ground plane height variation structure and the second surface.

An amplifier is configured in such a way that a first capacitor resonates at the frequency of a second harmonic wave included in a signal outputted from an amplifying element, a circuit including a second transmission line, the first capacitor, and a second capacitor resonates at the frequency of a third harmonic wave included in the signal outputted from the amplifying element, and also matches the impedance for a fundamental wave together with an impedance matching circuit.

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.