A high-frequency amplifier includes: a carrier amplifier amplifying a first signal; a peak amplifier amplifying a second signal; a first transmission line connected between output terminals of the carrier amplifier and the peak amplifier, and having an electrical length equal to one-quarter wavelength of a center frequency in the predetermined frequency band; a second transmission line connected between one end of the first transmission line and the output terminal of the high-frequency amplifier, and having an electrical length equal to one-quarter wavelength of the center frequency; and an impedance compensation circuit with one end connected to a node between the first transmission line and the second transmission line. At the center frequency, an imaginary part of an impedance during viewing of the impedance compensation circuit from the node is opposite in polarity from an imaginary part of an impedance during viewing of the second transmission line from the node.

A coupler circuit includes: a signal line disposed between a first terminal and a second terminal; a coupling line disposed between a coupling port and an isolation port such that the coupling line is coupled to the signal line and is configured to extract a coupling signal from the signal line; and a coupling adjusting circuit connected to the coupling port and the isolation port, and configured to reduce changes in an amount of coupling according to a change in a frequency band of a signal passing through the signal line.

An envelope detecting circuit is for generating an envelope signal of an input RF signal as described. The envelope detecting circuit includes an input terminal, an output terminal, a balun, a transistor, and an integrating circuit. The transistor, which is operated in the class B or the class C mode, receives an input signal from the balun, amplifies the input signal, and outputs an amplified signal. The integrating circuit, which is provided between the transistor and the output terminal, provides a series circuit of a resistor and a capacitor between the bias supply and ground. The transistor receives the bias through the resistor. The capacitor holds bottom levels of the amplified signal.

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.

A plurality of transmission lines (3b,3c) are connected to a transistor (1) and have different characteristic impedances. A plurality of open stubs (4a,4b) are connected to the plurality of transmission lines (3b,3c) respectively. A length of each open stub (4a,4b) is shorter than a length of each transmission line (3b,3c).

Methods and apparatus for providing high efficiency power amplifiers for both high and low output power levels are disclosed. An example apparatus includes a first amplifier to amplify a signal from a host device; and transmit the amplified signal to an antenna; a second amplifier to amplify the signal from the host device; and transmit the amplified signal to the antenna; and first, second, and third switches to: when the first and second switches are closed and the third switch is open, couple the first amplifier to the second amplifier in a parallel structure; and when the first and second switches are open and the third switch is closed, couple the first amplifier to the second amplifier in a stacked structure.

Provided is a harmonic suppression method, a corresponding low-noise amplifier (20, 30, 40), and a communication terminal. In the harmonic suppression method, an isolation unit (23, 33, 43) is arranged between a harmonic suppression unit (24, 34, 44) of the low-noise amplifier (20, 30, 40) and an output match network (25, 35, 45)/input match network (21, 31, 41). The harmonic suppression unit (24, 34, 44) is isolated from the output match network (25, 35, 45)/input match network (21, 31, 41) by means of the isolation unit (23, 33, 43), so that the two are not affected or compromised by each other, and can be designed separately. In this way, the design flexibility of a signal amplification circuit is greatly improved, and the design difficulty is reduced.

A MMIC support and cooling structure having a three-dimensional, thermally conductive support structure having a plurality of surfaces and a circuit having a plurality of heat generating electrical components disposed on a first portion of the surfaces and interconnected by microwave transmission lines disposed on a second portion of the plurality of surfaces of the thermally conductive support structure

A Doherty power amplifier circuit having a main power amplification device, an auxiliary power amplification device arranged in parallel with the main power amplification device, and a load modulation circuit comprising a harmonic injection circuit connected with respective outputs of the main power amplification device and the auxiliary power amplification device. The harmonic injection circuit is arranged to transfer harmonic components generated at the main power amplification device to the auxiliary power amplification device and harmonic components generated at the auxiliary power amplification device to the main power amplification device, when both the main and auxiliary power amplification devices are operating, for modulating the respective outputs of the main power amplification device and the auxiliary power amplification device.

A high-frequency front end circuit includes an antenna terminal, a reception circuit that is directly or indirectly connected to the antenna terminal, and a transmission circuit that is directly or indirectly connected to the antenna terminal, wherein the transmission circuit has an amplification circuit, the amplification circuit includes an input terminal and an output terminal, an amplification element provided on a path connecting the input terminal and the output terminal, and a bias circuit having an LC resonance circuit and connected to between the amplification element and the output terminal. A frequency pass band of the transmission circuit is lower than a frequency pass band of the reception circuit, and a value of a resonant frequency of the bias circuit is smaller than a value of a frequency pass band width of the transmission circuit.