Wireless transceiver with amplifier bias adjusted based on modulation scheme and transmit power feedback

• US 8,738,066 B2
• Filed: 10/07/2010
• Issued: 05/27/2014
• Est. Priority Date: 10/07/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Reddy, Vusthla Sunil, Akhi, Fraldun
• Primary Examiner(s): TRINH, TAN H
• Application Number:
  US12/900,406
• Publication Number:
  US 20120088510A1
• Time in Patent Office: 1,328 Days
• Field of Search: 455/69, 455/522, 455/13.4, 455/513, 455/504, 455/67.13, 455/67.11, 455/63.1, 455/115.1, 455/136, 455/138, 455/220, 455/213, 455/222, 455/245.1, 455/341, 455/574, 455/127.2, 455/127.4, 455/73, 455/450, 455/127.5, 455/119, 455/126, 455/108, 455/572, 330/136, 330/129, 330/302, 330/127, 330/297, 330/83, 330/98, 330/200
• US Class Current: 455/522
• 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 1/0261 with control of the polarisation voltage or current, e.g. gliding Class A
• CPC Class Codes: H03F 2200/393 A measuring circuit being coupled to the output of an amplifier
• CPC Class Codes: H03F 2200/465 Power sensing
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/045 with means for improving efficiency

Abstract

An electronic device may contain a transceiver that transmits and receives radio-frequency signals through antenna structures. Power amplifier circuitry may amplify the radio-frequency signals that are being transmitted. An adjustable voltage supply may supply an adjustable power amplifier bias voltage to the power amplifier circuitry. The power amplifier circuitry may include multiple power amplifiers each of which may handle signals transmitted using a different cellular telephone standard. For each cellular telephone standard, multiple modulation schemes may be supported. A power detector may provide real time measurements of output power. Control circuitry can adjust the transceiver circuitry based on the measurements of output power and can adjust the adjustable power amplifier bias voltage in real time to select an optimum power amplifier bias voltage based on the current cellular telephone standard, modulation scheme, power amplifier gain state, and operating frequency in use.

Claims

1. An electronic device that is configured to wirelessly transmit radio-frequency signals using a plurality of cellular telephone modulation schemes, comprising:

antenna structures;

a transceiver that produces the radio-frequency signals for transmission;

power amplifier circuitry that amplifies the radio-frequency signals for transmission of the radio-frequency signals through the antenna structures at an output power;

a power detector that produces measurements of the output power;

an adjustable voltage supply that supplies an adjustable power amplifier bias voltage to the power amplifier circuitry to power the power amplifier circuitry; and

control circuitry that is configured to direct the adjustable voltage supply to supply the adjustable power amplifier bias voltage at a level that is adjusted in real time based at least partly on which cellular telephone modulation scheme of the plurality of cellular telephone modulation schemes is currently being used in transmitting the radio-frequency signals through the antenna structures, wherein the control circuitry includes storage that contains calibration data, wherein the calibration data includes calibration data specifying a first power amplifier bias voltage for a first operating frequency and a second power amplifier bias voltage for a second operating frequency, and wherein the first operating frequency is different from the second operating frequency.

2. The electronic device defined in claim 1 wherein the control circuitry is configured to use the measurements of the output power in adjusting the transceiver.

3. The electronic device defined in claim 2 wherein the transceiver includes a variable gain amplifier and wherein the control circuitry is configured to adjust the variable gain amplifier at least partly in response to the measurements of the output power.

4. The electronic device defined in claim 3 wherein the transceiver is configured to transmit the radio-frequency signals using a plurality of modulation schemes selected from the group consisting of:

Gaussian Minimum Shift Keying, 8 Phase Shift Keying, Binary Phase Shift Keying, Quadrature Phase Shift Keying, 16 Quadrature Amplitude Modulation, 64-Quadrature Amplitude Modulation.

5. The electronic device defined in claim 4 wherein the transceiver is configured to transmit the radio-frequency signals in accordance with a plurality of cellular telephone standards selected from the group consisting of:

a Global System for Mobile Communications cellular telephone standard, an Evolution-Data Optimized cellular telephone standard, a Universal Mobile Telecommunications System cellular telephone standard, a Code Division Multiple Access 2000 cellular telephone standard, and a Long Term Evolution cellular telephone standard.

6. The electronic device defined in claim 1 wherein the calibration data includes calibration data specifying which levels of power amplifier bias voltage the adjustable voltage supply is to supply in multiple power amplifier gain states for the power amplifier circuitry.

7. A method for operating an electronic device with wireless communications circuitry that has a variable gain amplifier that supplies radio-frequency signals, a power amplifier that amplifies the radio-frequency signals and transmits the radio-frequency signals with an output power, an adjustable voltage supply that supplies a bias voltage to the power amplifier, and a power detector that measures the output power, comprising:

wirelessly transmitting the radio-frequency signals with the wireless communications circuitry using a modulation scheme selected from a plurality of modulation schemes supported by the electronic device; and

while wirelessly transmitting the radio-frequency signals using the modulation scheme, using the adjustable voltage supply to adjust the bias voltage to a level that is selected based at least partly on which of the plurality of modulation schemes is being used to wirelessly transmit the radio-frequency signals and using measurements from the power detector in adjusting the variable gain amplifier, wherein using the measurements comprises using the measurements to adjust a variable gain amplifier gain setting in a calibration table that corresponds to a modulation scheme with worst-case adjacent channel leakage.

8. The method defined in claim 7 wherein the modulation scheme that is being used to wirelessly transmit the radio-frequency signals comprises a given modulation scheme selected from the group consisting of:

Gaussian Minimum Shift Keying, 8 Phase Shift Keying, Binary Phase Shift Keying, Quadrature Phase Shift Keying, 16 Quadrature Amplitude Modulation, 64-Quadrature Amplitude Modulation and wherein wirelessly transmitting comprises wirelessly transmitting using the given modulation scheme.

9. The method defined in claim 7 wherein wirelessly transmitting comprises wirelessly transmitting using a cellular telephone standard selected from the group consisting of:

a Global System for Mobile Communications cellular telephone standard, an Evolution-Data Optimized cellular telephone standard, a Universal Mobile Telecommunications System cellular telephone standard, a Code Division Multiple Access 2000 cellular telephone standard, and a Long Term Evolution cellular telephone standard.

10. The method defined in claim 7 wherein using the adjustable voltage supply comprises using the adjustable voltage supply to produce a bias voltage at a level selected based at least partly on a bias voltage entry in the calibration table stored in the electronic device.

11. The method defined in claim 7 wherein using the adjustable voltage supply comprises using the adjustable voltage supply to produce a bias voltage at a level selected based at least partly on a bias voltage entry in the calibration table stored in the electronic device, wherein the plurality of modulation schemes includes a worst-case modulation scheme and a plurality of other modulation schemes, and wherein the calibration table includes minimum bias voltage entries corresponding to the worst-case modulation scheme and minimum bias voltage entries corresponding to each of the other modulation schemes.

12. The method defined in claim 7 further comprising:

during first wireless operations with the electronic device, wirelessly transmitting radio-frequency signals at a given frequency using a first modulation scheme and during second wireless operations with the electronic device, wirelessly transmitting radio-frequency signals at the given frequency using a second modulation scheme, wherein the second modulation scheme has greater power amplifier linearity requirements than the first modulation scheme at the given frequency, and wherein during use of the second modulation scheme the adjustable voltage supply supplies the bias voltage at a level that is higher than during use of the first modulation scheme.

13. A method of operating an electronic device containing wireless communications circuitry that has been characterized across a plurality of cellular telephone standards and corresponding modulation schemes to produce calibration data for the electronic device, wherein the wireless communications circuitry includes a transceiver that produces radio-frequency signals, a power amplifier that transmits the radio-frequency signals at an output power, and a power detector that obtains measurements of the output power and wherein the calibration data comprises power amplifier bias voltage levels to use for each of the modulation schemes to enhance power conservation during operation of the electronic device, and wherein the transceiver includes a variable gain amplifier, the method comprising:

wirelessly transmitting the radio-frequency signals using the power amplifier in the electronic device;

while wirelessly transmitting the radio-frequency signals, applying power amplifier bias voltages to the power amplifier in the electronic device at levels that are adjusted in real time based on the calibration data;

adjusting the transceiver based at least partly on the measurements of the output power; and

identifying settings for the variable gain amplifier at a plurality of cellular telephone operating frequencies and a given one of the modulation schemes when producing the calibration data.

14. The method defined in claim 13 further comprising characterizing the wireless communications circuitry at a plurality of power amplifier gain states for the power amplifier when producing the calibration data.

15. The method defined in claim 14 further comprising characterizing the wireless communications circuitry at a plurality of cellular telephone operating frequencies when producing the calibration data.

16. The method defined in claim 13 further comprising producing at least some of the calibration data for a plurality of modulation schemes selected from the group consisting of:

Gaussian Minimum Shift Keying, 8 Phase Shift Keying, Binary Phase Shift Keying, Quadrature Phase Shift Keying, 16 Quadrature Amplitude Modulation, 64-Quadrature Amplitude Modulation.

17. The method defined in claim 16 further comprising producing at least some of the calibration data for a plurality of cellular telephone standards selected from the group consisting of:

a Global System for Mobile Communications cellular telephone standard, an Evolution-Data Optimized cellular telephone standard, a Universal Mobile Telecommunications System cellular telephone standard, a Code Division Multiple Access 2000 cellular telephone standard, and a Long Term Evolution cellular telephone standard.