Quasi-differential RF power amplifier with high level of harmonics rejection
A quasi-differential amplifier with an input port and an output port. The amplifier has a phase shifter network with a first port connected to the input port, a second port, and a third port. A first amplifier has an input connected to the second port of the phase shifter network, and an output, and a second amplifier has an input connected to the third port of the phase shifter network, and an output. A balun circuit includes a first differential port connected to an output of the first amplifier, a second differential port connected to an output of the second amplifier, and a single-ended port. An output matching network is connected to the single-ended port of the balun circuit and to the output port.
1. A quasi-differential amplifier, comprising:
an input port;
an output port;
a phase shifter network having a first port connected to the input port, a second port, and a third port;
a first amplifier having an input connected to the second port of the phase shifter network, and an output;
a second amplifier having an input connected to the third port of the phase shifter network, and an output;
a balun circuit including a first differential port connected to an output of the first amplifier, a second differential port connected to an output of the second amplifier, a single-ended port, a first pair of first and second coupled inductors with the first coupled inductor being electrically connected to the first differential port and the single-ended port, the second coupled inductor being electrically connected to the second differential port, a first capacitor electrically connected between the first coupled inductor and the single ended port, and to the second coupled inductor and the second differential port, a second capacitor electrically connected to the second coupled inductor, and a grounded inductor electrically coupled in series to the second capacitor;
a compensation network connected to the output of the second amplifier and the second differential port of the balun circuit; and
an output matching network connected to the single-ended port of the balun circuit and to the output port.
2. The quasi-different amplifier of claim 1 wherein a differential signal fed to the first differential port and the second differential port from the respective one of the first amplifier and the second amplifier are converted to a single signal output from the single-ended port, and a common output impedance of the single-ended port is transformed from an input impedance of the first and second differential ports.
3. The quasi-differential amplifier of claim 1 further comprising a first amplifier interconnection inductor connected to the output of the first amplifier and the first differential port of the balun circuit.
4. The quasi-differential amplifier of claim 3 wherein the first amplifier interconnection inductor is an interconnect trace.
5. The quasi-differential amplifier of claim 1 further comprising a second amplifier interconnection inductor connected to the output of the second amplifier and the compensation network.
6. The quasi-differential amplifier of claim 1 wherein the compensation network is tuned to reject third harmonic signal components.
7. The quasi-differential amplifier of claim 1 wherein the output matching network transforms an output impedance from an initial predefined value to a final predefined value.
8. The quasi-differential amplifier of claim 7 wherein the final predefined value of the output impedance is fifty (50) ohm.
9. The quasi-differential amplifier of claim 1 wherein the output matching network is tuned to reject second harmonic signal components.
10. The quasi-differential amplifier of claim 9 wherein the output matching network includes a first network segment tuned to reject the second harmonic signal components, and a second network segment tuned to reject fourth harmonic signal components.
11. The quasi-differential amplifier of claim 1 further comprising a harmonic rejection component connected to the first differential port of the balun circuit and the second differential port of the balun circuit.
12. The quasi-differential amplifier of claim 1 further comprising a first common bias supply connected to the first amplifier and the second amplifier.
13. The quasi-differential amplifier of claim 12 wherein the first common bias supply includes a voltage source connected to a pair of coupled inductors, a first one of the coupled inductors being connected to the first amplifier, and a second one of the coupled inductors being connected to the second amplifier.
14. The quasi-differential amplifier of claim 1 further comprising a second common bias supply connected to the first amplifier and the second amplifier.
15. The quasi-differential amplifier of claim 14 wherein the second common bias supply includes a control signal source connected to a pair of coupled inductors, a first one of the coupled inductors being connected to the first amplifier, and a second one of the coupled inductors being connected to the second amplifier.
16. The quasi-differential amplifier of claim 15 further comprising a matching capacitor connected to the first one of the coupled inductors and the second one of the coupled inductors.
17. The quasi-differential amplifier of claim 1 wherein the first amplifier and the second amplifier each include a bipolar junction transistor having a base, a collector, and an emitter.
18. The quasi-differential amplifier of claim 1 wherein the first amplifier and the second amplifier each include a field effect transistor having a gate, a source, and a drain.
19. The quasi-differential amplifier of claim 1 wherein either one or both of the first amplifier and the second amplifier have a cascode configuration.
20. The quasi-differential amplifier of claim 1 wherein the phase shifter network includes a splitter with a common terminal connected to the first port of the phase shifter network, a first split terminal connected to the second port of the phase shifter network, and a second split terminal.
21. The quasi-differential amplifier of claim 20 wherein the phase shifter network further includes a shifter having a first terminal connected to the second split terminal of the splitter, and a second terminal connected to the third port of the phase shifter network.
22. The quasi-differential amplifier of claim 2 wherein phases of voltage components and current components of the differential signal are tuned to a predefined minimum.
23. The quasi-differential amplifier of claim 22 wherein the predefined minimum is less than five degrees.
24. The quasi-differential amplifier of claim 2 wherein a total power level delivered to the first and second differential ports are within a predefined percentage of each other.
25. The quasi-differential amplifier of claim 24 wherein the predefined percentage is less than ten percent.
26. A quasi-differential amplifier, comprising:
an input port;
an output port;
a phase shifter network having a first port connected to the input port, a second port, and a third port;
a first amplifier having an input connected to the second port of the phase shifter network, and an output;
a second amplifier having an input connected to the third port of the phase shifter network, and an output;
a balun circuit including a first differential port connected to an output of the first amplifier, a second differential port connected to an output of the second amplifier, a single-ended port, a first pair of first and second coupled inductors with the first coupled inductor being electrically connected to the first differential port and the single-ended port, the second coupled inductor being electrically connected to the second differential port, a first capacitor electrically connected between the first coupled inductor and the single ended port, and to the second coupled inductor and the second differential port, a second capacitor electrically connected to the second coupled inductor, and a grounded inductor electrically coupled in series to the second capacitor; and
an output matching network connected to the single-ended port of the balun circuit and to the output port, the output matching network including a first network segment tuned to reject second harmonic signal components, and a second network segment tuned to reject fourth harmonic signal components.
27. The quasi-different amplifier of claim 26 wherein a differential signal fed to the first differential port and the second differential port from the respective one of the first amplifier and the second amplifier are converted to a single signal output from the single-ended port, and a common output impedance of the single-ended port is transformed from an input impedance of the first and second differential ports.
28. The quasi-differential amplifier of claim 27 wherein the common output impedance of the single-ended port is ten (10) ohm, the input impedance of the first differential port is seven (7) ohm, and the input impedance of the second differential port is seven (7) ohm.
29. The quasi-differential amplifier of claim 26 further comprising a harmonic rejection component connected to the first differential port of the balun circuit and the second differential port of the balun circuit.