N-way doherty distributed power amplifier with power tracking
A power amplifier using N-way Doherty structure with adaptive bias supply power tracking for extending the efficiency region over the high peak-to-average power:ratio of the multiplexing modulated signals such as wideband code division multiple access and orthogonal frequency division multiplexing is disclosed. In an embodiment, present invention uses a dual-feed distributed structure to an N-way Doherty amplifier to improve the isolation between at least one main amplifier and at least one peaking amplifier and, and also to improve both gain and efficiency performance at high output back-off power. Hybrid couplers can be used at either or both of the input and output. In at least some implementations, circuit space is also conserved due to the integration of amplification, power splitting and combining.
1. A power tracking system for power amplifiers comprising:
an N-way Doherty distributed amplifier comprising a power splitter with a plurality of first outputs and N amplifiers, wherein:
N is an integer of three or more,
the N amplifiers includes a main amplifier and at least two peaking amplifiers, the main amplifier belonging to a different amplifier class than the peaking amplifiers,
a first output of the plurality of first outputs is distributed via a first transmission line amongst the a plurality of the peaking amplifiers,
each amplifier of the N amplifiers produces a second output,
the second outputs from the plurality of peaking amplifiers are combined via a second transmission line to produce a third output, and
the third output from the peaking amplifiers is combined with the second output the main amplifier; and
adaptive bias supply circuitry that adaptively adjusts a DC bias applied to at least one amplifier of the N amplifiers.
2. The power tracking system of claim 1 wherein the adaptive bias supply circuitry adaptively adjusts the DC bias based on a feature of an RF input.
3. The power tracking system of claim 1 wherein the adaptive bias supply circuitry adaptively adjusts the DC bias based on an envelope of an RF input.
4. The power tracking system of claim 1 wherein the adaptive bias supply circuitry adaptively adjusts the DC bias based on a power of an RF input.
5. The power tracking system of claim 1 wherein the adaptive bias supply circuit is coupled to a plurality of gate and drain terminals.
6. The power tracking system of claim 1 wherein the adaptive bias supply circuit is operable to output a plurality of gate biases.
7. The power tracking system of claim 1 wherein the adaptive bias supply circuit that adaptively adjusts a DC bias applied to a plurality of the N amplifiers.
8. The power tracking system of claim 1 wherein the adaptive bias supply circuit is configured to adjust gate biases of the at least one amplifier and a shunt capacitor, the N-way Doherty distributed amplifier comprising the at least one amplifier and shunt capacitor.
9. The power tracking system of claim 1 wherein the adaptive bias supply circuit is configured to adjust gate biases of a plurality of amplifiers and shunt capacitors, the N amplifiers of the N-way Doherty distributed amplifier comprising the plurality of peaking amplifiers and shunt capacitors.
10. The power tracking system of claim 1 further comprising an RF choke coupling the bias supply circuitry to an active device, the N-way Doherty distributed amplifier comprising the active device.
11. The power tracking system of claim 1 wherein the power splitter is an M-way power splitter, M being less than N.
12. The power tracking system of claim 1 wherein the output provided to a first amplifier of the plurality of N amplifiers is processed by fewer signal-altering components as compared to the output provided to a second amplifier of the plurality of N amplifiers.
13. The power tracking system of claim 1 wherein a first amplifier of the plurality of N amplifiers directly receives the output and a second amplifier of the plurality of N amplifiers does not directly receive the output.
14. The power tracking system of claim 1 wherein the adaptive bias supply circuitry is configured to apply different biases to be associated with each of N amplifiers in the N-way Doherty distributed amplifier.
15. A method for processing an RF input, the method comprising:
dividing the RF input into a plurality of resultant signals;
routing at least one of the resultant signals to a main amplifier, the main amplifier producing a first output in response to the at least one of the resultant signals;
routing another of the resultant signals via a first transmission line to a plurality of peaking amplifiers, each of the peaking amplifiers producing a second output in response to the another of the resultant signals;
combining the second outputs via a second transmission line to produce a third output;
combining the first output with the third output; and
adaptively controlling one or more bias voltages of at least one of the amplifiers,
wherein the main and peaking amplifiers are amplifiers in an N-way Doherty distributed amplifier.
16. The method of claim 15 wherein the at least one of the amplifiers comprises the main amplifier and at least one peaking amplifier.
17. The method of claim 15 wherein adaptively controlling the one or more bias voltages of the at least one of the amplifiers comprises adaptively applying different biases to at least two of the amplifiers.
18. The method of claim 15 wherein the one or more bias voltages are DC bias voltages.
19. The method of claim 15 wherein the one or more bias voltages comprise drain and gate bias voltages.
20. The method of claim 15 further comprising adaptively controlling one or more bias voltages of one or more shunt capacitors.
21. The method of claim 15 wherein the one or more bias voltages comprises at least three different bias voltages.