Radio frequency time skew calibration systems and methods

Patent metadata

Field	Value
Publication number	US-9577771-B1
Application number	US-201615218923-A
Country	US
Kind code	B1
Filing date	Jul 25, 2016
Priority date	Jul 25, 2016
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

Systems and method for improving operation of a radio frequency system are provided. One embodiment provides a radio frequency system that includes an amplifier device with a first data path and a second data path. Additionally, the radio frequency system includes a controller that instructs the radio frequency system to transmit a calibration signal, which includes a first portion that excites the first data path and a second portion that excites the second data path; determines time skew between the first and second data paths based at least in part on phase shift between a first sample of a feedback signal and the first portion, phase shift between a second sample of the feedback signal and the second portion, or both; and instructs the radio frequency system to adjust delay applied on the first data path, the second data path, or both based at least on the time skew.

First claim

What is claimed is:

1. An electronic device comprising a radio frequency system configured to wirelessly transmit data, wherein the radio frequency system comprises:
an amplifier device comprising a first data path and a second data path, wherein the amplifier device is configured to:
receive an analog representation of the data as an analog electrical signal, a digital representation of the data as a digital electrical signal, or both; and
generate an amplified analog electrical signal used to wirelessly transmit the data based on a first signal output from the first data path and a second signal output from the second data path; and

a controller configured to:
instruct the radio frequency system to transmit a calibration signal comprising a first portion configured to excite the first data path and a second portion configured to excite the second data path;
determine a feedback signal resulting from transmission of the calibration signal;
determine time skew between the first data path and the second data path based on one or more of:
a first phase shift between a first sample of the feedback signal and the first portion of the calibration signal; and
a second phase shift between a second sample of the feedback signal and the second portion of the calibration signal; and

instruct the radio frequency system to adjust at least one of a first delay applied on the first data path and a second delay applied on the second data path based on the time skew.

2. The electronic device of claim 1 , wherein:
the first portion of the calibration signal comprises a first amplitude component and a first phase component, wherein the first amplitude component changes to excite the first data path and the first phase component is constant to not excite the second data path; and
the second portion of the calibration signal comprises a second amplitude component and a second phase component, wherein the second phase component changes to excite the second data path and the first amplitude component is constant to not excite the first data path.

3. The electronic device of claim 1 , wherein the controller is configured to:
determine a third sample of the feedback signal based on a first duration of the calibration signal;
determine a total delay of the radio frequency system based on cross-correlation between the third sample and the calibration signal; and
determine the time skew based on the total delay of the radio frequency system.

4. The electronic device of claim 3 , wherein the controller is configured to:
adjust the feedback signal based on the total delay of the radio frequency system;
determine the first sample of the feedback signal based on a second duration of the first portion of the calibration signal after the feedback signal is adjusted;
determine a first relative delay of the first data path based on the first phase shift between the first sample and the first portion of the calibration signal, wherein the first relative delay is proportional to the first phase shift;
determine the second sample of the feedback signal based on a third duration of the first portion of the calibration signal and the second portion of the calibration signal;
determine a second relative delay of the second data path based on the second phase shift between the second sample and the second portion of the calibration signal; and
determine the time skew based on difference between the first relative delay and the second relative delay.

5. The electronic device of claim 1 , wherein:
the first data path is configured to generate a variable voltage signal by amplifying an amplitude component of the data based on a target output power of the radio frequency system;
a second data path is configured to generate a frequency signal by adjusting frequency of a phase component of the data based on a target output frequency of the radio frequency system; and
the amplifier device comprises a switch mode power amplifier configured to facilitate generating the amplified analog electrical signal based on the variable voltage signal and the frequency signal.

6. The electronic device of claim 1 , wherein:
the first data path is configured to generate a variable voltage signal by amplifying an amplitude component of the data based on a target output power of the radio frequency system;
a second data path is configured to generate a frequency converted signal by adjusting frequency of the data based on a target output frequency of the radio frequency system; and
the amplifier device comprises a linear mode power amplifier configured to generate the amplified analog electrical signal based on the variable voltage signal and the frequency converted signal.

7. The electronic device of claim 1 , comprising:
an antenna configured to output a transmitted analog electrical signal as modulated radio waves based on the amplified analog electrical signal;
a coupler configured to feed back the transmitted analog electrical signal; and
a feedback local oscillator configured to generate the feedback signal by adjusting frequency of the transmitted analog electrical signal.

8. The electronic device of claim 1 , wherein:
the first data path comprises a first delay device configured to apply a first delay to the first signal;
the second data path comprises a second delay device configured to apply a second delay to the second signal; and
the controller is configured to:
instruct at least one of the first delay device to decrease the first delay and the second delay device to increase the second delay when the time skew indicates that a first relative delay of the first data path is greater than a second relative delay of the second data path by more than a time skew threshold;
instruct at least one of the first delay device to increase the first delay and the second delay device to decrease the second delay when the time skew indicates that the second relative delay is greater than then first relative delay by more than the time skew threshold; and
instruct the first delay device to maintain the first delay and the second delay to maintain the second delay otherwise.

9. The electronic device of claim 1 , wherein the electronic device comprises a computer, a mobile phone, a portable media device, a tablet, a television, a virtual-reality headset, a personal data organizer, a handheld game platform, or a vehicle dashboard.

10. A tangible, non-transitory, computer-readable medium configured to store instructions executable by one or more processors of a radio frequency system, wherein the instructions comprise instructions to:
instruct, using the one or more processors, the radio frequency system to successively repeat transmission of a calibration signal at a target output power by amplifying the calibration signal using an amplifier device;
determine, using the one or more processors, a feedback signal resulting from transmission of the calibration signal;
determine, using the one or more processors, a total delay of the radio frequency system based at least in part on cross-correlation between the calibration signal and a first sample of the feedback signal;
determine, using the one or more processors, a first relative delay of an envelope data path in the amplifier device based at least in part on a first phase shift between a first portion of the calibration signal and a second sample of the feedback signal, wherein the first portion of the calibration signal comprises a changing amplitude component and a constant phase component;
determine, using the one or more processors, a second relative delay of a phase data path in the amplifier device based at least in part on a second phase shift between a second portion of th

Assignees

• Apple Inc

Inventors

• Lashkarian Navid
• Chehrazi Saeed
• Parsa Ali

Classifications

• H04B17/11

  for calibration · CPC title

• H04B17/24

  with feedback of measurements to the transmitter · CPC title

• H03F2200/411

  the output amplifying stage of an amplifier comprising two power stages · CPC title

• H03F1/0266

  by using a signal derived from the input signal · CPC title

• H04B17/13 Primary

  of power amplifiers, e.g. gain or non-linearity · CPC title