Active harmonic filters for integrated radio frequency power amplifiers

1. A radio frequency front end circuit comprising:

an output signal transmission line;

an amplifier circuit with an input connected to a radio frequency signal source and an output connected to the output signal transmission line; and

a harmonic suppression circuit connected to the amplifier circuit, the harmonic suppression circuit including an active circuit element having a frequency-dependent impedance and being tuned as a reflective trap with a negative capacitance for one or more rejection frequency ranges each corresponding to a multiple of a fundamental frequency of a signal generated by the radio frequency signal source.

2. The radio frequency front end circuit of claim 1 wherein the active circuit element is an operational amplifier with an inverting input, a non-inverting input, and a single-ended output.

3. The radio frequency front end circuit of claim 2 wherein the harmonic suppression circuit includes a first inductive-capacitive element connected to the inverting input and to the single-ended output and defining a first rejection frequency notch.

4. The radio frequency front end circuit of claim 3 wherein the harmonic suppression circuit includes a resistor network connected to the non-inverting input and to the single-ended output.

5. The radio frequency front end circuit of claim 4 wherein the harmonic suppression circuit includes a first tank circuit connecting the active circuit element to the transmission line.

6. The radio frequency front end circuit of claim 4 wherein the harmonic suppression circuit includes a second tank circuit in line with the transmission line.

7. The radio frequency amplifier of claim 6 wherein the harmonic suppression circuit includes a third tank circuit connected to the second tank circuit in line with the transmission line.

8. The radio frequency front end circuit of claim 1 wherein the active circuit element is a differential amplifier including a first pair of transistors and a second pair of transistors.

9. The radio frequency front end circuit of claim 1 wherein the amplifier circuit is a radio frequency power amplifier and the signal is a transmit signal, the harmonic suppression circuit being connected to the output signal transmission line.

10. The radio frequency front end circuit of claim 1 wherein the amplifier circuit is a radio frequency low noise amplifier and the signal is a receive signal, the harmonic suppression circuit being connected to the input of the amplifier circuit.

11. The radio frequency front end circuit of claim 1 wherein the amplifier circuit and the harmonic suppression circuit are fabricated on a single semiconductor die.

12. A radio frequency communications module comprising:

a packaging substrate on which a plurality of components are mounted;

an output signal transmission line disposed on the packaging substrate;

an amplifier circuit implemented on the packaging substrate, the amplifier circuit including an input connected to a radio frequency signal source and an output connected to the output signal transmission line; and

a harmonic suppression circuit implemented on the packaging substrate and connected to the amplifier circuit, the harmonic suppression circuit including an active circuit element having a frequency-dependent impedance and being tuned as a reflective trap with a negative capacitance for one or more rejection frequency ranges each corresponding to a multiple of a fundamental frequency of a signal generated by the radio frequency signal source.

13. The radio frequency communications module of claim 12 wherein the active circuit element is an operational amplifier with an inverting input, a non-inverting input, and a single-ended output.

14. The radio frequency communications module of claim 13 wherein the harmonic suppression circuit includes a first inductive-capacitive element connected to the inverting input and to the single-ended output and defining a first rejection frequency notch.

15. The radio frequency communications module of claim 14 wherein the harmonic suppression circuit includes a resistor network connected to the non-inverting input and to the single-ended output.

16. The radio frequency communications module of claim 15 wherein the harmonic suppression circuit includes a first tank circuit connecting the active circuit element to the transmission line.

17. The radio frequency communications module of claim 15 wherein the harmonic suppression circuit includes a second tank circuit in line with the transmission line.

18. The radio frequency communications module of claim 17 wherein the harmonic suppression circuit includes a third tank circuit connected to the second tank circuit in line with the transmission line.

19. The radio frequency communications module of claim 12 wherein the active circuit element is a differential amplifier including a first pair of transistors and a second pair of transistors.

20. A wireless communications device comprising:

an antenna receptive to an incoming radio frequency signal and transmissive of an outgoing radio frequency signal;

an output transmission line connectable to the antenna;

a radio frequency amplifier circuit connected to the antenna; and

a harmonic suppression circuit connected to the amplifier circuit, the harmonic suppression circuit including an active circuit element having a frequency-dependent impedance and being tuned as a reflective trap with a negative capacitance for one or more rejection frequency ranges each corresponding to a multiple of a fundamental frequency of a signal generated by a radio frequency signal source.

21. The wireless communications device of claim 20 wherein the active circuit element is an operational amplifier with an inverting input, a non-inverting input, and a single-ended output.

22. The wireless communications device of claim 20 wherein the active circuit element is a differential amplifier including a first pair of transistors and a second pair of transistors.