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. An amplifier device comprising:
an input circuit having a radiofrequency input configured to receive a radiofrequency signal for amplification, the input circuit including a hybrid coupler, a first output, and a second output;
a main amplification circuit having a main input coupled to the first output of the input circuit, the main amplification circuit having a main output;
a first peaking amplification circuit having a first peaking input coupled to the second output of the input circuit, the first peaking amplification circuit having a first peaking output;
a second peaking amplification circuit having a second peaking input coupled to the first peaking input of the first peaking amplification circuit via a first half-wave transmission line, the second peaking amplification circuit having a second peaking output coupled to the first peaking output via a second half-wave transmission line;
an output circuit having a third input coupled to the main output of the main amplification circuit and a fourth input coupled to the first peaking output of the first peaking amplification circuit, the output circuit having a radiofrequency output providing an amplified radiofrequency signal, wherein the output circuit includes:
an offset line coupled to each of the third input and the fourth input of the output circuit; and
a second hybrid coupler coupled to the third input and the fourth input of the output circuit and the radiofrequency output of the output circuit.
2. The amplifier device of claim 1 , wherein the main amplification circuit includes a first input impedance matching circuit.
3. The amplifier device of claim 2 , wherein the first peaking amplification circuit includes a second input impedance matching circuit.
4. The amplifier device of claim 1 , wherein the main amplification circuit includes a first output impedance matching circuit and wherein the first peaking amplification circuit includes a second output impedance matching circuit.
5. The amplifier device of claim 1 , wherein the output circuit includes:
the offset line coupled to each of the third input and the fourth input of the output circuit; and
impedance transformers coupled to the offset line and the radiofrequency output of the output circuit.
6. The amplifier device of claim 1 , wherein the main amplification circuit includes a main amplifier, and wherein the main amplifier is biased as a Class AB amplifier.
7. The amplifier device of claim 6 , wherein the main amplifier comprises at least one transistor.
8. The amplifier device of claim 1 , wherein the first peaking amplification circuit includes a peaking amplifier, and wherein the peaking amplifier is biased as a Class C amplifier.
9. The amplifier device of claim 1 , wherein the first peaking amplification circuit comprises at least one transistor.
10. The amplifier device of claim 1 , wherein the first peaking amplification circuit includes a dual-feed distributed structure.
11. The amplifier device of claim 1 , further comprising:
a first shunt capacitor coupled to the second peaking input of the second peaking amplification circuit; and
a second shunt capacitor coupled to the second peaking output of the second peaking amplification circuit.
12. The amplifier device of claim 11 , wherein the first shunt capacitor is coupled to the second peaking input of the second peaking amplification circuit via a first quarter-wave transmission line, and wherein the second shunt capacitor is coupled to the second peaking output of the second peaking amplification circuit via a second quarter-wave transmission line.
13. A method for amplifying a radiofrequency signal, comprising:
producing, using an input circuit including a hybrid coupler, a first output and a second output, the input circuit having an input configured to receive the radiofrequency signal;
amplifying, using a main amplification circuit, the first output of the input circuit, the main amplification circuit having a main output providing a main amplified signal;
amplifying, using a first peaking amplification circuit and a second peaking amplification circuit, the second output of the input circuit, the first peaking amplification circuit having a first peaking input coupled to a second peaking input of the second peaking amplification circuit via a first half-wave transmission line, the first peaking amplification circuit having a first peaking output providing a first peaking amplified signal, the second peaking amplification circuit having a second peaking output coupled to the first peaking output of the first peaking amplification circuit via a second half-wave transmission line and providing a second peaking amplified signal; and
combining, using an output circuit, the main amplified signal, the first peaking amplified signal, and the second peaking amplified signal, wherein the output circuit drives each of the main amplified signal, the first peaking amplified signal, and the second peaking amplified signal through an offset line, wherein the output circuit combines an offset line output using a second hybrid coupler, wherein the second hybrid coupler produces a coupled output associated with the output circuit, wherein the coupled output associated with the output circuit provides an amplified radiofrequency output signal.
14. The method of claim 13 , further comprising:
impedance matching, using a first input impedance matching circuit, the first output of the input circuit; and
impedance matching, using a second input impedance matching circuit, the second output of the input circuit.
15. The method of claim 13 , further comprising:
impedance matching, using a first output impedance matching circuit, the main output of the main amplification circuit to produce the main amplified signal; and
impedance matching, using a second output impedance matching circuit, the first peaking output of the first peaking amplification circuit to produce the first peaking amplified signal.
16. The method of claim 13 , wherein combining the main amplified signal and the first peaking amplified signal includes:
driving each of the main amplified signal and the first peaking amplified signal through the offset line of the output circuit; and
combining the offset line output using impedance transformers, the impedance transformers producing the coupled output of the output circuit.
17. The method of claim 13 , wherein the main amplification circuit includes a main amplifier, and wherein the main amplifier is biased as a Class AB amplifier.
18. The method of claim 13 , wherein the first peaking amplification circuit includes a peaking amplifier, and wherein the peaking amplifier is biased as a Class C amplifier.
19. The method of claim 13 , wherein the first peaking amplification circuit includes a dual-feed distributed structure.