Power Amplifier Linearizer
Circuits and methods for achieving good amplifier AM-AM and AM-PM metrics while achieving good power, PAE, linearity, and EVM performance. Embodiments compensate for a non-linear distortion profile (e.g., an AM-PM and/or AM-AM profile) in an amplifier by pre-processing an input signal, such as a radio-frequency signal, to alter the non-linear distortion profile of the input signal so as to compensate for the non-linear distortion profile imposed by a coupled device, such as an amplifier. An inventive aspect includes linearizing an output from an amplifier having a first non-linear distortion profile, including passing an input signal having a second non-linear distortion profile through a reflective hybrid coupler to a non-linear termination circuit, and reflecting a modified input signal from the non-linear termination circuit back through the reflective hybrid coupler as an output signal, the output signal having a third non-linear distortion profile shaped to compensate for the first non-linear distortion profile.
1 . A circuit, including:
(a) a reflective hybrid coupler including an input port, a direct port, a coupled port, and an output port, the reflective hybrid coupler being configured to receive an input signal on the input port, the input signal having a first non-linear distortion profile; and
(b) a non-linear termination circuit including:
(1) a first reflective modulation device including a first field-effect transistor (FET) having a gate coupled to the direct port of the reflective hybrid coupler, a drain, and a source; and
(2) a second reflective modulation device including a second FET having a gate coupled to the coupled port of the reflective hybrid coupler, a drain, and a source;
(c) a first load inductor coupled to the drain of the first FET of the first reflective modulation device and configured to be coupled to a voltage supply; and
(d) a second load inductor coupled to the drain of the second FET of the second reflective modulation device and configured to be coupled to the voltage supply;
wherein the non-linear termination circuit reflects a modified input signal back through the output port of the reflective hybrid coupler as an output signal, the output signal having a second non-linear distortion profile.
2 . The circuit of claim 1 , wherein the gate of the first FET of the first reflective modulation device is capacitively coupled to the direct port of the reflective hybrid coupler, and the gate of the second FET of the second reflective modulation device is capacitively coupled to the coupled port of the reflective hybrid coupler.
3 . The circuit of claim 1 , wherein the respective gates of the first and second FETs of the first and second reflective modulation devices are coupled to respective bias voltages.
4 . The circuit of claim 1 , wherein the first load inductor and the second load inductor are the same inductor.
5 . The circuit of claim 1 , wherein the second non-linear distortion profile is shaped to compensate for a third non-linear distortion profile imposed on the output signal by another device.
6 . The circuit of claim 5 , wherein the other device comprises an amplifier.
7 . The circuit of claim 1 , wherein the input signal has a first amplitude-to-phase modulation (AM-PM) profile, the output signal has a second AM-PM profile, and the second AM-PM profile is shaped to compensate the first AM-PM profile for an AM-PM distortion imposed by another device coupled to the output port of the reflective hybrid coupler.
8 . The circuit of claim 7 , wherein the other device comprises an amplifier.
9 . A linearizer circuit, including:
(a) a reflective hybrid coupler including an input port, a direct port, a coupled port, and an output port, the reflective hybrid coupler being configured to receive an input signal on the input port, the input signal having a first non-linear distortion profile; and
(b) a non-linear termination circuit including:
(1) a first reflective modulation device including a first field-effect transistor (FET) having a gate coupled to the direct port of the reflective hybrid coupler, a drain, and a source; and
(2) a second reflective modulation device including a second FET having a gate coupled to the coupled port of the reflective hybrid coupler, a drain, and a source; and
(c) a common load inductor having a first terminal coupled to a voltage and a second terminal coupled to each of the drains of the respective first and second FETs of the first and second reflective modulation devices;
wherein the non-linear termination circuit reflects a modified input signal back through the output port of the reflective hybrid coupler as an output signal, the output signal having a second non-linear distortion profile.
10 . The circuit of claim 9 , wherein the gate of the first FET of the first reflective modulation device is capacitively coupled to the direct port of the reflective hybrid coupler, and the gate of the second FET of the second reflective modulation device is capacitively coupled to the coupled port of the reflective hybrid coupler.
11 . The circuit of claim 9 , wherein the respective gates of the first and second FETs of the first and second reflective modulation devices are coupled to respective bias voltages.
12 . The circuit of claim 9 , wherein the second non-linear distortion profile is shaped to compensate for a third non-linear distortion profile imposed on the output signal by another device.
13 . The circuit of claim 12 , wherein the other device comprises an amplifier.
14 . The circuit of claim 9 , wherein the input signal has a first amplitude-to-phase modulation (AM-PM) profile, the output signal has a second AM-PM profile, and the second AM-PM profile is shaped to compensate the first AM-PM profile for an AM-PM distortion imposed by another device coupled to the output port of the reflective hybrid coupler.
15 . The circuit of claim 14 , wherein the other device comprises an amplifier.
16 . A circuit, including:
(a) a reflective hybrid coupler including an input port, a direct port, a coupled port, and an output port, the reflective hybrid coupler configured to receive an input signal on the input port, the input signal having a first amplitude-to-phase modulation (AM-PM) profile;
(b) a first reflective modulation device including a first field-effect transistor (FET) having a gate coupled to the direct port of the reflective hybrid coupler, a drain, and a source;
(c) a second reflective modulation device including a second FET having a gate coupled to the coupled port of the reflective hybrid coupler, a drain, and a source;
(d) a first load inductor coupled to the drain of the first FET of the first reflective modulation device and configured to be coupled to a first voltage supply; and
(e) a second load inductor coupled to the drain of the second FET of the second reflective modulation device and configured to be coupled to a second voltage supply;
wherein the first and second reflective modulation devices modify the first AM-PM profile of the input signal to an output signal on the output port of the reflective hybrid coupler, the output signal having a second AM-PM profile.
17 . The circuit of claim 16 , wherein the gate of the first FET of the first reflective modulation device is capacitively coupled to the direct port of the reflective hybrid coupler, and the gate of the second FET of the second reflective modulation device is capacitively coupled to the coupled port of the reflective hybrid coupler.
18 . The circuit of claim 16 , wherein the respective gates of the first and second FETs of the first and second reflective modulation devices are coupled to respective bias voltages.
19 . The circuit of claim 16 , wherein the first load inductor and the second load inductor are the same inductor.
20 . The circuit of claim 16 , wherein the second AM-PM profile is shaped to compensate the first AM-PM profile for an AM-PM distortion imposed by another device coupled to the output port of the reflective hybrid coupler.