RF amplifier having a transition shaping filter

• US 10,038,461 B2
• Filed: 10/06/2016
• Issued: 07/31/2018
• Est. Priority Date: 10/30/2012
• Status: Active Grant

• Current Assignee: ETA Devices, Inc. (Nokia Corporation)
• Original Assignee: ETA Devices, Inc. (Nokia Corporation)
• Inventors: Briffa, Mark A., Dawson, Joel L., DeRoo, John E., Komoni, Krenar, Perreault, David J., Uyar, Oguzhan
• Primary Examiner(s): TRAN, PABLO N
• Application Number:
  US15/287,068
• Publication Number:
  US 20170063407A1
• Time in Patent Office: 663 Days
• Field of Search: 4551273, 455 91, 455102, 455103, 4551141, 4551151, 4551152, 455118, 455126, 4551271, 4551272, 4551274, 375296, 375297, 330124 R, 330127, 330129, 330149
• CPC Class Codes: H03F 1/02 Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
• CPC Class Codes: H03F 1/0211 with control of the supply voltage or current
• CPC Class Codes: H03F 1/0216 Continuous control
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 2200/171 A filter circuit coupled to the output of an amplifier
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/504 the supply voltage or current being continuously controlled by a controlling signal, e.g. the controlling signal of a transistor implemented as variable resistor in a supply path for, an IC-block showed amplifier
• CPC Class Codes: H03F 2200/511 Many discrete supply voltages or currents or voltage levels can be chosen by a control signal in an IC-block amplifier circuit
• CPC Class Codes: H03F 2203/21106 An input signal being distributed in parallel over the inputs of a plurality of power amplifiers
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/21 with semiconductor devices only H03F3/245 takes precedence
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths
• CPC Class Codes: H04B 2001/0416 having gain or transmission power control
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion
• CPC Class Codes: H04B 2001/045 : with means for improving efficiency

Abstract

A radio frequency (RF) power amplifier system or transmitter includes one or more power amplifiers and a controller that is configured to adjust amplitudes and phases of RF input signals of the one or more power amplifiers and supply voltages applied to the one or more power amplifiers. In embodiments where multiple power amplifiers are used, a combiner may be provided to combine outputs of the power amplifiers.

Claims

1. A radio frequency (RF) power amplifier system comprising:

an RF power amplifier;

a digital-to-RF modulator to generate an RF input signal for the RF power amplifier based on input information indicative of amplitude values and phase values;

a voltage control unit to provide a variable supply voltage to the RF power amplifier in response to one or more control signals, the variable supply voltage being selected from a plurality of discrete voltage levels; and

a controller to provide the input information to the digital-to-RF modulator and the one or more control signals to the voltage control unit based, at least in part, on data to be output by the RF power amplifier system;

wherein the voltage control unit includes;

an output terminal to provide an output voltage signal, the output terminal being coupled to a supply input of the RF power amplifier;

first, second, and third voltage terminals to carry first, second, and third discrete voltage levels in the plurality of discrete voltage levels, respectively;

a first switch coupled between the output terminal and the first voltage terminal;

a second switch coupled between the output terminal and a first intermediate node and wherein the controller is configured to control states of the second switch;

a third switch coupled between the first intermediate node and the second voltage terminal;

a network comprising at least one switch coupled between the first intermediate node and the third voltage terminal and wherein the controller is configured to control states of the at least one switch; and

a transition shaping filter having a low pass filter characteristic to filter the output voltage signal before it is provided to the RF power amplifier wherein said transition shaping filter incorporates parasitic elements associated with the interconnect of the voltage control unit to the power amplifier and said transition shaping filter is provided having a filter characteristic selected such that the frequency content of the supply voltage is matched to a frequency content which may be adjusted for in a drive waveform provided to the power amplifier.

2. The RF power amplifier system of claim 1, wherein:

the network includes a fourth switch coupled between the first intermediate node and a second intermediate node and a fifth switch coupled between the second intermediate node and the third voltage terminal; and

the voltage control unit further comprises;

a fourth voltage terminal to carry a fourth discrete voltage level in the plurality of discrete voltage levels; and

a sixth switch coupled between the second intermediate node and the fourth voltage terminal;

wherein the controller is configured to control states of at least the second, fourth, and sixth switches.

3. The RF power amplifier system of claim 1, wherein the voltage control unit further comprises a seventh switch coupled between the output terminal and a ground terminal, wherein the controller is configured to control states of at least the second, seventh and at least one switches.

4. The RF power amplifier system of claim 1, wherein the first and third switches each include a diode.

5. The RF power amplifier system of claim 1, wherein the plurality of discrete voltage levels consists of three voltage levels.

6. The RF power amplifier system of claim 1, wherein the plurality of discrete voltage levels consists of four voltage levels.

7. The RF power amplifier system of claim 1, wherein the controller is configured to make decisions about voltage level changes for the RF power amplifier based, at least in part, on a window of data samples representing data to be output by the RF power amplifier system.

8. The RF power amplifier system of claim 1, wherein one or more of the first switch, the second switch, the third switch, and the at least one switch are provided as complimentary metal oxide semiconductor (CMOS) technology.

9. The RF power amplifier system of claim 1, wherein the voltage control unit further comprises a switched capacitor converter to synthesize multiple ratiometric voltages from a single input voltage, the switched capacitor converter providing at least some of the discrete voltage levels of the plurality of discrete voltage levels.

10. The RF power amplifier system of claim 1, wherein:

the RF power amplifier is a first RF power amplifier; and

the RF power amplifier system further comprises at least one additional RF power amplifier and a combiner to combine the output signals of the first RF power amplifier and the at least one additional RF power amplifier.

11. The RF power amplifier system of claim 1, wherein:

the controller is configured to control states of the first switch, the second switch, the third switch, and the at least one switch.

12. The RF power amplifier system of claim 1 wherein the transition shaping filter comprises:

a first inductive element having a first terminal coupled to an input terminal of said transition shaping filter and a second terminal;

a second inductive element having a first terminal coupled to the second terminal of the first inductive element having a second terminal coupled to an output terminal of said transition shaping filter;

a first resistor having a first terminal coupled to the second terminal of said first inductive element and a second terminal coupled to the output terminal of said transition shaping filter.

13. The RF power amplifier system of claim 1 wherein the transition shaping filter further comprises:

a first capacitor having a first terminal coupled to the second terminal of said second inductive element and a second terminal coupled to the second output terminal of said transition shaping filter;

a first resistor having a first terminal coupled to the second terminal of said second inductive element and a second terminal; and

a second capacitor having a first terminal coupled to the second terminal of said first resistor and a second terminal coupled to the second output terminal of said transition shaping filter.

14. A machine implemented method for operating a radio frequency (RF) transmitter having a digital-to-RF modulator driving an RF power amplifier, the method comprising:

obtaining transmit data to be transmitted from the RF transmitter;

providing input information for the digital-to-RF modulator based, at least in part, on the transmit data, the input information to control an amplitude and a phase of an RF output signal of the digital-to-RF modulator;

selecting a supply voltage for the RF power amplifier based, at least in part, on the transmit data, the supply voltage being selected from a plurality of discrete voltage levels, wherein the supply voltage changes with time;

providing control signals to a plurality of switches within a voltage control unit based on the changing supply voltage selection, wherein the voltage control unit includes;

an output terminal to provide an output voltage signal, the output terminal being coupled to a supply terminal of the RF power amplifier;

first, second, and third voltage terminals to carry first, second, and third discrete voltage levels in the plurality of discrete voltage levels, respectively;

a first switch coupled between the output terminal and the first voltage terminal;

a second switch coupled between the output terminal and a first intermediate node;

a third switch coupled between the first intermediate node and the second voltage terminal; and

a network comprising at least one switch coupled between the first intermediate node and the third voltage terminal, wherein providing control signals includes providing control signals to at least the second switch and the at least one switch; and

a transition shaping filter having a low pass filter characteristic to filter the output voltage signal before it is provided to the RF power amplifier wherein said transition shaping filter incorporates parasitic elements associated with the interconnect of the voltage control unit to the power amplifier and said transition shaping filter is provided having a filter characteristic selected such that the frequency content of the supply voltage is matched to a frequency content which may be adjusted for in a drive waveform provided to the power amplifier.

15. The method of claim 14, wherein:

the network includes a fourth switch coupled between the first intermediate node and a second intermediate node and a fifth switch coupled between the second intermediate node and the third voltage terminal; and

the voltage control unit further comprises;

a fourth voltage terminal to carry a fourth discrete voltage level in the plurality of discrete voltage levels; and

a sixth switch coupled between the second intermediate node and the fourth voltage terminal;

wherein providing control signals includes providing control signals to the second, fourth, and sixth switches.

16. The method of claim 15, wherein the voltage control unit further comprises a seventh switch coupled between the output terminal and a ground terminal, wherein providing control signals includes providing control signals to the first, second, third, fourth, fifth, sixth, and seventh switches.

17. The method of claim 14, wherein the first and third switches each include a diode.

18. The method of claim 14, wherein selecting a supply voltage for the RF power amplifier includes selecting a supply voltage from a group of three discrete voltage levels.

19. The method of claim 14, wherein selecting a supply voltage for the RF power amplifier includes selecting the supply voltage from a group of four discrete voltage levels.

20. The method of claim 14, wherein:

selecting a supply voltage includes selecting the supply voltage based, at least in part, on a window of data samples associated with the transmit data.

21. The method of claim 14, further comprising:

processing the supply voltage signal in a low pass filter before applying the signal to the RF power amplifier wherein said transition shaping filter has a first pair of terminals which form an input and a second pair of terminals which form an output, the shaping filter comprising;

a first inductive element having a first terminal coupled to a first one of the first pair of input terminals of said transition shaping filter and a second terminal coupled to a first one of the pair of output terminals of said transition shaping filter;

a first capacitor having a first terminal coupled to the second terminal of said first inductive element and a second terminal coupled to a second one of the pair of output terminals of said transition shaping filter;

a first resistor having a first terminal coupled to the second terminal of said first inductive element and a second terminal; and

a second capacitor having a first terminal coupled to the second terminal of said first resistor and a second terminal coupled to the second output terminal of said transition shaping filter.

22. The method of claim 14, wherein:

the RF transmitter includes multiple digital-to-RF modulators driving multiple RF power amplifiers and a combiner to combine output signals of the multiple power amplifiers.

23. The method of claim 14, wherein:

providing control signals includes providing control signals to the first switch, the second switch, the third switch, and the at least one switch.