A direct current (DC)-DC converter that includes a first switching converter and a multi-stage filter is disclosed. The multi-stage filter includes at least a first inductance (L) capacitance (C) filter and a second LC filter coupled in series between the first switching converter and a DC-DC converter output. The first LC filter has a first LC time constant and the second LC filter has a second LC time constant, which is less than the first LC time constant. The first LC filter includes a first capacitive element having a first self-resonant frequency, which is about equal to a first notch frequency of the multi-stage filter.

Transformer-based Doherty power amplifier (PA). In some embodiments, a Doherty PA can include a carrier amplification path having an output that includes a carrier transformer, and a peaking amplification path having an output that includes a peaking transformer. The Doherty PA can further include a combiner configured to combine the outputs of the carrier and peaking amplification paths into an output node. The combiner can include a quarter-wave circuit implemented between the carrier and peaking transformers.

According to one embodiment, a high-frequency amplifier includes an active element and an output matching circuit. The active element is provided on a substrate. The active element is configured to amplify a signal having a frequency band. The active element includes a cell region. The output matching circuit is connected to the active element. The output matching circuit includes a wire, a transmission line and an output terminal. The wire includes an input end and an output end. The input end of the wire is connected to an output part of the cell region of the active element. The transmission line is provided on the substrate. The transmission line includes an input part and an output part. The input part of the transmission line is connected to the output end of the wire. The output terminal is provided on the substrate.

An embodiment of a Doherty amplifier module includes a substrate, an RF signal splitter, a carrier amplifier die, and a peaking amplifier die. The RF signal splitter divides an input RF signal into first and second input RF signals, and conveys the first and second input RF signals to first and second splitter output terminals. The carrier amplifier die includes one or more first power transistors configured to amplify, along a carrier signal path, the first input RF signal to produce an amplified first RF signal. The peaking amplifier die includes one or more second power transistors configured to amplify, along a peaking signal path, the second input RF signal to produce an amplified second RF signal. The carrier and peaking amplifier die are coupled to the substrate so that the RF signal paths through the carrier and peaking amplifier die extend in substantially different (e.g., orthogonal) directions.

Examples of an amplifier includes an input divider section having a first path and a second path for branching of an input signal, wherein a passing phase at the first path and a passing phase at the second path are different; a first amplifying element that amplifies a signal input to the first path; a second amplifying element that amplifies a signal input to the second path; an output synthesizing section that performs synthesis of an output of the first amplifying element and an output of the second amplifying element with a third path for transmitting the output of the first amplifying element and a fourth path for transmitting the output of the second amplifying element, wherein a passing phase at the third path and a passing phase at the fourth path are different; and an electromagnetic coupling section that establishes electromagnetic coupling of two signals.

In order to realize a power-saving power amplifier compatible with Carrier Aggregation technology using a plurality of bands, with a small size and low cost, while improving the amplitude accuracy and power efficiency, a transmission device of the present invention comprises: a modulation means that generates, from a baseband signal corresponding to each of the plurality of bands, a first and a second constant-envelope signals having different phases; a power amplification means that amplifies respective ones of the first and second constant-envelope signals generated by the modulation means; and a combining means that combines together the first and second constant-envelope signals amplified by the power amplification means and thereby generating an RF signal in which amplitude information contained in each of the baseband signals corresponding to respective ones of the plurality of bands is restored.

An embodiment of the present disclosure provides an impedance matching circuit including a matching network. The matching network includes a first port and a second port, and one or more variable reactance components. The one or more variable reactance components are operable to receive one or more variable voltage signals to cause the one or more variable reactance components to change an impedance of the matching network. At least one of the one or more variable reactance components includes a first conductor coupled to one of the first port or the second port of the matching network, a second conductor, and a tunable material positioned between the first conductor and the second conductor. Additionally, at least one of the first conductor and the second conductor are adapted to receive the one or more variable voltage signals to cause the change in the impedance of the matching network. Additional embodiments are disclosed.

An embodiment of the present disclosure provides an impedance matching circuit including a matching network. The matching network includes a first port and a second port, and one or more variable reactance components. The one or more variable reactance components are operable to receive one or more variable voltage signals to cause the one or more variable reactance components to change an impedance of the matching network. At least one of the one or more variable reactance components includes a first conductor coupled to one of the first port or the second port of the matching network, a second conductor, and a tunable material positioned between the first conductor and the second conductor. Additionally, at least one of the first conductor and the second conductor are adapted to receive the one or more variable voltage signals to cause the change in the impedance of the matching network. Additional embodiments are disclosed.

An amplifier arrangement comprises N amplifier stages (10.sub.1 to 10.sub.N), wherein N is an integer equal or greater than four. The amplifier arrangement comprises a cascade of quarter wavelength transmission lines coupled between an output of an amplifier of a first amplifier stage (10.sub.1) and an output node (15) of the amplifier arrangement, wherein the cascade comprises N−1 quarter wavelength transmission lines (11.sub.1 to 11.sub.N−1). An amplifier of the Nth stage (10.sub.N) is coupled to the output node (15), and remaining amplifiers between the first and Nth stages (10.sub.2 to 10.sub.N−1) coupled to successive junctions in the cascade of quarter wavelength transmission lines (11.sub.1 to 11.sub.N−1). The amplifier arrangement is further configured such that apart from first and second amplifiers (10.sub.1 and 10.sub.2) coupled to first and second junctions of the cascade of quarter wavelength transmission lines, the remaining amplifiers (10.sub.3 to 10.sub.N) are coupled to their respective junctions of the cascade of quarter wavelength transmission lines such that successive pairs of amplifiers are either coupled via respective connecting quarter wavelength transmission lines (13) to their respective junctions, or coupled directly to their respective junctions.

Embodiments of a Doherty power amplifier that maintain efficiency over a large operating average power range are disclosed. In one embodiment, the Doherty power amplifier includes reconfigurable main and auxiliary output matching networks and a fixed combining network. The reconfigurable main and auxiliary output matching networks can be reconfigured such that together the reconfigurable main output matching network, the reconfigurable auxiliary output matching network, and the fixed combining network provide proper load modulation for multiple different back-off power levels. As a result, the Doherty power amplifier maintains high efficiency over an extended back-off power level range.