A high directivity compact size inter-layer coupler that has application for coupling off a pre-distortion coupling signal from a main signal at an output of a power amplifier to a pre-distortion circuit. The coupler includes a main signal line formed on a surface of a first dielectric layer opposite to a second dielectric layer, where the main signal line receives the main signal, and a coupling line formed between the second dielectric layer and a third dielectric layer, where the coupling line is electromagnetically coupled to the main line so as to generate the coupling signal thereon. The coupling line has a general U-shape including a first leg portion, a second leg portion and a transverse portion between the first and second leg portions. The transverse portion includes a plurality of spaced apart blocks coupled together by a narrow line portion.

A method for communication includes producing an error signal by comparing a driving signal applied to a transmitter to an output signal generated by the transmitter in response to the driving signal. The error signal is decomposed into a linear component having a first memory depth and a nonlinear component having one or more polynomial orders and a second memory depth that is less than the first memory depth. First coefficients, up to the first memory depth, of a linear predistortion kernel are computed for application to the driving signal so as to compensate for the linear component of the error signal. Second coefficients for the one or more polynomial orders, up to the second memory depth, of a nonlinear predistortion kernel are computed so as to compensate for the nonlinear component of the error signal. Operation of the transmitter is optimized using the first and second coefficients.

Apparatus and methods for true power detection are provided herein. In certain embodiments, a power amplifier system includes an antenna, a directional coupler, and a power amplifier electrically connected to the antenna by way of a through line of the directional coupler. The power amplifier system further includes a combiner that combines a first coupled signal from a first end of the directional coupler's coupled line with a second coupled signal from a second end of the directional coupler's coupled line.

A compound semiconductor device includes a semiconductor multilayer structure including an electron transit layer and an electron supply layer of a compound semiconductor; a source electrode, a gate electrode, and a drain electrode that are disposed above the semiconductor multilayer structure and are aligned in a first direction; a first insulating film that is formed on the semiconductor multilayer structure between the gate electrode and the drain electrode, and has a tensile stress; a second insulating film that is formed on the semiconductor multilayer structure between the gate electrode and the source electrode, and has a compressive stress; and a protective film that is formed between the first insulating film and the semiconductor multilayer structure, and between the second insulating film and the semiconductor multilayer structure.

A compound semiconductor device includes a semiconductor laminate structure including an electron transit layer and an electron supply layer that are formed from compound semiconductor, a source electrode, a gate electrode, and a drain electrode that are provided above the semiconductor laminate structure and arranged in a first direction, and a first insulating film having a first internal stress and formed over the semiconductor laminate structure and between the gate electrode and the drain electrode, wherein a slit extending in the first direction is defined in the first insulating film.

A method for communication includes producing an error signal by comparing a driving signal applied to a transmitter to an output signal generated by the transmitter in response to the driving signal. The error signal is decomposed into a linear component having a first memory depth and a nonlinear component having one or more polynomial orders and a second memory depth that is less than the first memory depth. First coefficients, up to the first memory depth, of a linear predistortion kernel are computed for application to the driving signal so as to compensate for the linear component of the error signal. Second coefficients for the one or more polynomial orders, up to the second memory depth, of a nonlinear predistortion kernel are computed so as to compensate for the nonlinear component of the error signal. Operation of the transmitter is optimized using the first and second coefficients.

A RF-digital hybrid mode power amplifier system for achieving high efficiency and high linearity in wideband communication systems is disclosed. The present invention is based on the method of adaptive digital predistortion to linearize a power amplifier in the RF domain. The present disclosure enables a power amplifier system to be field reconfigurable and support multi-modulation schemes (modulation agnostic), multi-carriers and multi-channels. As a result, the digital hybrid mode power amplifier system is particularly suitable for wireless transmission systems, such as base-stations, repeaters, and indoor signal coverage systems, where baseband I-Q signal information is not readily available.

A radio frequency front-end includes a power amplifier. The radio frequency front-end also includes a coupler implemented in at least a portion of a matching circuit, the matching circuit coupled to an output of the power amplifier. The radio frequency front-end further includes a control loop comprising a first feedback terminal at an output of the power amplifier. The control loop includes the coupler coupled to the first feedback terminal of the power amplifier and is configured to generate a feedback signal provided to a second feedback terminal to adjust a gain of the power amplifier. The feedback signal is based on a reflected radio frequency signal provided by the coupler.

A directional coupler and a method for manufacturing the same are disclosed. According to an embodiment, the directional coupler comprises a first transmission line configured to receive an input signal. The directional coupler further comprises a second transmission line that can be coupled to the first transmission line by electromagnetic coupling to output a coupled signal. The first transmission line is further configured to act as a quarter-wave impedance transformer. A radio transmitter comprising the directional coupler and a radio device comprising the radio transmitter are also disclosed.

A compound semiconductor device includes a compound semiconductor stack structure, a protective film provided on the compound semiconductor stack structure and containing titanium oxide, and a polycrystalline diamond film provided on the protective film.