Certain aspects of the present disclosure are directed to digital predistortion (DPD) for use with a multi-chain wireless transmitter. In various examples described herein, the multi-chain transmitter is configured to use a single common DPD device or module for all transmit chains and to adjust the bias voltages of the power amplifiers of the separate transmit chains to operate at substantially the same backoff so the distortion to the corresponding output signals is similar. Since the distortion of the output of the different chains is similar, a single common predistortion may be applied using the single DPD device to a signal to be transmitted. Techniques are also described for calibrating the predistortion coefficients of the DPD to optimize (or otherwise set) the amount of distortion reduction to be achieved. The predistortion coefficients for the single DPD may be set or calibrated based on a particular directionality needed for beamforming.

A semiconductor device includes the following elements. A chip has a main surface substantially parallel with a plane defined by first and second directions intersecting with each other. A power amplifier amplifies an input signal and outputs an amplified signal from plural output terminals. First and second filter circuits attenuate harmonics of the amplified signal. The first filter circuit includes a first capacitor connected between the plural output terminals and a ground. The second filter circuit includes a second capacitor connected between the plural output terminals and a ground. On the main surface of the chip, the plural output terminals are disposed side by side in the first direction, and the first capacitor is disposed on a side in the first direction with respect to the plural output terminals, while the second capacitor is disposed on a side opposite the first direction with respect to the plural output terminals.

A semiconductor device includes the following elements. A chip has a main surface substantially parallel with a plane defined by first and second directions intersecting with each other. A power amplifier amplifies an input signal and outputs an amplified signal from plural output terminals. First and second filter circuits attenuate harmonics of the amplified signal. The first filter circuit includes a first capacitor connected between the plural output terminals and a ground. The second filter circuit includes a second capacitor connected between the plural output terminals and a ground. On the main surface of the chip, the plural output terminals are disposed side by side in the first direction, and the first capacitor is disposed on a side in the first direction with respect to the plural output terminals, while the second capacitor is disposed on a side opposite the first direction with respect to the plural output terminals.

A protection circuit for use in an RF active circuit includes a signal strength detecting circuit, a current detecting circuit, a logic circuit, and a switching unit. The signal strength detecting circuit is coupled to the signal input end or the signal output end of the RF active circuit and configured to generate a first detecting signal according to the signal strength of the RF signal. The current detecting circuit is configured to detect the VSWR of the RF signal based on the driving current of the RF active circuit, thereby generating a corresponding second detecting signal. The logic circuit is configured to generate a switch control signal according to the first detecting signal and the second detecting signal. The switching unit is configured to lower the driving current of the RF active circuit according to the switch control signal.

A protection circuit for use in an RF active circuit includes a signal strength detecting circuit, a current detecting circuit, a logic circuit, and a switching unit. The signal strength detecting circuit is coupled to the signal input end or the signal output end of the RF active circuit and configured to generate a first detecting signal according to the signal strength of the RF signal. The current detecting circuit is configured to detect the VSWR of the RF signal based on the driving current of the RF active circuit, thereby generating a corresponding second detecting signal. The logic circuit is configured to generate a switch control signal according to the first detecting signal and the second detecting signal. The switching unit is configured to lower the driving current of the RF active circuit according to the switch control signal.

A power amplifier module includes an amplifier that amplifies an input signal and outputs an amplified signal, an emitter follower transistor that supplies a bias signal to the amplifier to control a bias point of the amplifier, and a current source that supplies a control current which changes in accordance with a change in control voltage to a collector of the emitter follower transistor. The current source limits the control current to not greater than an upper limit.

A power amplifier module includes an amplifier that amplifies an input signal and outputs an amplified signal, an emitter follower transistor that supplies a bias signal to the amplifier to control a bias point of the amplifier, and a current source that supplies a control current which changes in accordance with a change in control voltage to a collector of the emitter follower transistor. The current source limits the control current to not greater than an upper limit.

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.

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.

Spatial power-combining devices and antenna assemblies for spatial power-combining devices are disclosed. The disclosure relates to spatial power-combining devices with segmented waveguides and antennas. The spatial power-combining devices may be designed for high efficiency, high or low frequency ranges, ultra-wide bandwidth operation, and high output power. A spatial power-combining device may include a plurality of amplifiers, an output center waveguide including an output inner housing and an output outer housing, and an output coaxial waveguide. The output center waveguide may form a plurality of output center waveguide segments that are discontinuous with each other. Each output center waveguide segment may include a different portion of the output inner housing and the output outer housing. An antenna for a spatial power-combining device may include a plurality of antenna segments, each of which includes a different portion of a signal conductor and a ground conductor of the antenna.