Distributed Doherty amplifiers
View Patent ↗Doherty and distributed amplifier (DA) designs are combined to achieve, wideband amplifiers with high efficiency dynamic range. A modified Doherty amplifier includes a wideband phase shifter providing first and second outputs, a main amplifier coupled to the first output, an auxiliary amplifier coupled to the second output, and a wideband combining network combining the outputs in phase. A multi-stage DA has a main output and a termination port, and a phase delay module and transforming network allowing power at the termination port to be combined in phase with power at the main output. In one combination, one or more stages of the DA may comprise a Doherty amplifier. In another combination, a modified series-type Doherty amplifying system is achieved by cascading main and auxiliary DAs. In any combination, Doherty topology may include a bias control module.
1. A high efficiency, wideband amplifying system comprising:
a main distributed amplifier comprising a main output and a main termination port;
wherein the main distributed amplifier is configured to receive an input signal;
an auxiliary distributed amplifier coupled to the main termination port and comprising an auxiliary output and an auxiliary termination port;
a bias control module coupled between the auxiliary distributed amplifier and the main output of the main distributed amplifier;
a first phase delay module coupled between the main output and the auxiliary output; and
a second phase delay module coupled between the auxiliary termination port and the auxiliary output.
2. The amplifying system of claim 1 , wherein the bias control module is configured to adjust an input bias of the auxiliary distributed amplifier responsive to at least one of power detected at the main output of the main distributed amplifier or power detected at the main input to the main distributed amplifier.
3. The amplifying system of claim 1 , wherein the bias control module is configured to sample the main distributed amplifier output power at a sampling frequency.
4. The amplifying system of claim 1 , wherein the bias control module is controlled to optimize switching efficiency.
5. The amplifying system of claim 1 , wherein the bias control module monitors output of the main distributed amplifier to optimize the duty cycle of the auxiliary distributed amplifier.
6. The amplifying system of claim 1 , wherein the bias control module is configured to adjust the bias voltage based on sensing of a DC current to the auxiliary distributed amplifier and determine a compression point based on the sensed DC current.
7. The amplifying system of claim 1 , wherein the bias control module is configured to automatically adjust the input bias to the auxiliary distributed amplifier responsive to power detected at the output of the main distributed amplifier absent detecting power at the output of the auxiliary distributed amplifier.
8. The amplifying system of claim 1 , wherein the bias control module is configured to:
predict, based on the detected output power of the main distributed amplifier, the main distributed amplifier entering or the main distributed amplifier leaving saturation; and
adjust the timing of the auxiliary distributed amplifier switching.
9. The amplifying system of claim 1 , wherein at least one of the main distributed amplifier and the auxiliary distributed amplifier comprise multiple stages.
10. The amplifying system of claim 1 , wherein at least one of the main distributed amplifier and auxiliary distributed amplifier comprises a Doherty unit cell.
11. The amplifying system of claim 10 , wherein the Doherty unit cell comprises a cascaded reactively terminated single-stage distributed amplifier.
12. The amplifying system of claim 10 , wherein the Doherty unit cell comprises
a main amplifier having an output;
an auxiliary amplifier; and
a bias control automatically adjusting an input bias to the auxiliary amplifier responsive to at least one of power detected at the output of the main amplifier or power detected to the input of the main amplifier.
13. The amplifying system of claim 1 , further comprising a transforming network coupled to at least one of the output of the first phase delay module and the output of the second phase delay module.
14. The amplifying system of claim 1 , further comprising a transforming network coupled to the auxiliary output configured for impedance matching.
15. The amplifying system of claim 1 , wherein signal power is recaptured through the second phase delay module and a transforming network via a coupling to the auxiliary output.
16. A high efficiency, wideband amplifying system comprising:
a main distributed Doherty amplifier in series with an auxiliary distributed Doherty amplifier; and
a bias control module coupled between the auxiliary distributed Doherty amplifier and a main output of the main distributed Doherty amplifier, wherein the bias control module is configured to adjust the bias voltage based on sensing of a DC current to the auxiliary distributed Doherty amplifier and further determining a compression point based on the sensed DC current.
17. A high efficiency, wideband amplifying system comprising:
a main distributed Doherty amplifier in series with an auxiliary distributed Doherty amplifier;
a bias control module coupled between the auxiliary distributed Doherty amplifier and a main output of the main distributed Doherty amplifier, and
a transforming network configured for impedance matching coupled to at least one of an auxiliary distributed Doherty amplifier output and the main distributed Doherty amplifier output.
18. A high efficiency, wideband amplifying system comprising:
a main distributed Doherty amplifier in series with an auxiliary distributed Doherty amplifier;
a bias control module coupled between the auxiliary distributed Doherty amplifier and a main output of the main distributed Doherty amplifier, and
phase delay modules coupled between at least two of:
a) the main distributed Doherty amplifier output and an auxiliary distributed Doherty amplifier output;
b) the auxiliary distributed Doherty amplifier output and the main distributed Doherty amplifier output; and
c) an auxiliary distributed Doherty amplifier termination port and the auxiliary distributed Doherty amplifier output.