Wideband doherty power amplifier

A transmitter comprising:

• a signal processing path comprising:
• a digital baseband circuit to process data and output digital data;
• a converter to convert the digital data to analog data;
• at least one complex mixer to upconvert the analog data to quadrature radio frequency (RF) signals;
• a first power amplifier (PA) to receive a supply voltage and coupled to the at least one complex mixer to receive a first quadrature RF signal and output a first amplified quadrature RF signal;
• a second PA to receive the supply voltage and coupled to the at least one complex mixer to receive a second quadrature RF signal and output a second amplified quadrature RF signal;
• and
• a transformer circuit coupled to an output of the first PA and an output of the second PA, wherein the transformer circuit is to provide, to a load circuit, an RF output signal comprising the first amplified quadrature RF signal and the second amplified quadrature RF signal, wherein the transformer circuit comprises:
• a first transformer-capacitor circuit comprising:
• a first primary winding coupled to the output of the first PA and a first secondary winding inductively coupled to the first primary winding to provide the first amplified quadrature RF signal to the load circuit;
• a first capacitor coupled in parallel with the first primary winding;
• and
• a second capacitor coupled in parallel with the first secondary winding, wherein the first transformer-capacitor circuit, via the first primary winding, the first secondary winding, the first capacitor and the second capacitor, implements a transmission line having a characteristic impedance of the load circuit;
• and
• a second transformer-capacitor circuit comprising:
• a second primary winding coupled to the output of the second PA and a second secondary winding inductively coupled to the second primary winding to provide the second amplified quadrature RF signal to the load circuit;
• a third capacitor coupled in parallel with the second primary winding;
• a fourth capacitor coupled in parallel with the second secondary winding;
• a fifth capacitor coupled to the second secondary winding;
• and
• a sixth capacitor coupled to the second secondary winding.

A method comprising:

• amplifying, in a first power amplifier (PA) that receives a supply voltage, a first differential radio frequency (RF) signal and outputting a first amplified differential RF signal;
• amplifying, in a second PA that receives the supply voltage, a second differential RF signal and outputting a second amplified differential RF signal;
• transforming, in a first transformer coupled to the first PA, the first amplified differential RF signal to provide a first output RF signal to a load circuit, the first transformer comprising a matched transmission line and a first primary winding coupled to a first center tap node to receive half the supply voltage, the first primary winding coupled to an output of the first PA and a first secondary winding inductively coupled to the first primary winding to provide the first output RF signal to the load circuit, wherein a first capacitor is coupled in parallel with the first primary winding and a second capacitor is coupled in parallel with the first secondary winding to form the matched transmission line;
• and
• transforming, in a second transformer coupled to the second PA, the second amplified differential RF signal to provide a second output RF signal to the load circuit, the second transformer comprising a second primary winding coupled to a second center tap node to receive half the supply voltage, the second primary winding coupled to an output of the second PA and a second secondary winding inductively coupled to the second primary winding to provide the second output RF signal to the load circuit, wherein a third capacitor is coupled in parallel with the second primary winding, a fourth capacitor is coupled in parallel with the second secondary winding, a fifth capacitor is coupled between the second secondary winding and the load circuit, and a sixth capacitor is coupled between the second secondary winding and the load circuit.