Wide-band amplifiers using clipper circuits for reduced harmonics

• US 10,230,339 B2
• Filed: 03/22/2018
• Issued: 03/12/2019
• Est. Priority Date: 05/16/2013
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Bayruns, Robert, Gittemeier, Tim
• Primary Examiner(s): Nguyen, Patricia T
• Application Number:
  US15/928,639
• Publication Number:
  US 20180294780A1
• Time in Patent Office: 355 Days
• CPC Class Codes: H03F 1/3205 in field-effect transistor amplifiers
• CPC Class Codes: H03F 1/483 with field-effect transistors
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/351 Pulse width modulation being used in an amplifying circuit
• CPC Class Codes: H03F 2200/36 the amplifier comprising means for increasing the bandwidth
• CPC Class Codes: H03F 2200/429 Two or more amplifiers or one amplifier with filters for different frequency bands are coupled in parallel at the input or output
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 3/193 with field-effect devices H03F3/195 takes precedence
• CPC Class Codes: H03F 3/1935 with junction-FET devices
• CPC Class Codes: H03F 3/21 with semiconductor devices only H03F3/245 takes precedence

Abstract

The present invention breaks up the frequency bands which can be filtered by a simple low-loss band-pass or low pass filter. The second harmonic frequency is reduced by use of a non-linear clipper element which controls the driving waveform symmetry and can reduce the harmonics by as much as 5-15 db which makes the filter much simpler and allows the amplifier to remain wide-band. The output waveform from the amplifier is symmetrical or nearly symmetrical.

Claims

1. A wideband power amplifier circuit comprising:

a transistor configured as an amplifier stage of a power amplifier; and

a voltage variable clipping element that shapes a peak-to-peak amplitude of a signal applied to the transistor and reduces a second harmonic of the signal, the voltage variable clipping element electrically coupled to the transistor and controlled by a control voltage generated based at least in part on one or more of a temperature, an output power, or a voltage standing wave ratio under mismatch.

2. The wideband power amplifier of claim 1 further comprising a harmonic filter electrically coupled to an output of the power amplifier to reduce harmonic levels of the signal.

3. The wideband power amplifier of claim 2 wherein the harmonic filter includes at least one of a bandpass filter or a low pass filter.

4. The wideband power amplifier of claim 2 wherein the harmonic filter is configured to have substantially the same impedance as a load of the power amplifier.

5. The wideband power amplifier of claim 1 further comprising a voltage generator configured to generate the control voltage to control the operation of the voltage variable clipping element.

6. The wideband power amplifier of claim 5 wherein the voltage generator is further configured to generate the control voltage based at least in part on an adaptive feedback loop.

7. The wideband power amplifier of claim 1 wherein the voltage variable clipping element includes a negative waveform clipping element.

8. The wideband power amplifier of claim 1 further comprising a direct current blocking capacitor in communication with an input of the power amplifier.

9. The wideband power amplifier of claim 1 further comprising a direct current blocking capacitor between a harmonic filter and an output of the wideband power amplifier circuit.

10. The wideband power amplifier of claim 1 wherein the voltage variable clipping element is created from one or more diodes.

11. The wideband power amplifier of claim 10 wherein at least one of the one or more diodes is a Gallium Arsenide diode.

12. The wideband power amplifier of claim 10 wherein at least one of the one or more diodes is a Schottky diode.

13. The wideband power amplifier of claim 1 wherein the voltage variable clipping element reduces the second harmonic of the signal by at least 5 decibels.

14. An envelope tracking system comprising:

a power amplifier including a transistor; and

a voltage variable clipping element that shapes a peak-to-peak amplitude of a signal applied to the transistor and reduces a second harmonic of the signal, the voltage variable clipping element electrically coupled to the transistor and controlled by a control voltage generated based at least in part on one or more of a temperature, an output power, or a voltage standing wave ratio under mismatch.

15. The envelope tracking system of claim 14 further comprising a harmonic filter in communication with an output of the power amplifier and that reduces harmonic levels of the signal.

16. The envelope tracking system of claim 14 further comprising a voltage generator configured to generate the control voltage to control the operation of the voltage variable clipping element.

17. The envelope tracking system of claim 14 further comprising one or more direct current blocking capacitors in communication with the power amplifier.

18. The envelope tracking system of claim 14 wherein the voltage variable clipping element is created from one or more diodes.

19. The envelope tracking system of claim 18 wherein at least one of the one or more diodes is a Gallium Arsenide Schottky diode.

20. The envelope tracking system of claim 14 further comprising an adaptive feedback loop, the control voltage set based at least in part on the adaptive feedback loop.