Calibrating RF path delay and IQ phase imbalance for polar transmit system

• US 9,413,583 B2
• Filed: 12/18/2014
• Issued: 08/09/2016
• Est. Priority Date: 12/18/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel IP Corporation (Intel Corporation)
• Inventors: Belitzer, Alexander, Sogl, Bernhard
• Primary Examiner(s): Fan, Chieh M
• Assistant Examiner(s): Koeth, Michelle M
• Application Number:
  US14/575,733
• Publication Number:
  US 20160182162A1
• Time in Patent Office: 600 Days
• US Class Current: 1/1
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 17/104 of other parameters, e.g. DC offset, delay or propagation times
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion
• CPC Class Codes: H04B 2001/0433 with linearisation using feedback
• CPC Class Codes: H04H 20/12 Arrangements for observation, testing or troubleshooting
• CPC Class Codes: H04L 1/248 Distortion measuring systems measurement of non-linear distortion G01R23/20; measuring characteristics of individual pulses, e.g. deviation from pulse flatness, rise time, duration G01R29/02
• CPC Class Codes: H04L 27/361 Modulation using a single or unspecified number of carriers, e.g. with separate stages of phase and amplitude modulation
• CPC Class Codes: H04L 27/364 Arrangements for overcoming imperfections in the modulator, e.g. quadrature error or unbalanced I and Q levels
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
• CPC Class Codes: H04W 72/0473 the resource being transmission power

Abstract

A method of calibrating parameters for a polar transmitter (Polar TX) system includes receiving phase information derived from transmission information in a Polar TX for producing a radio frequency (RF) broadcast signal. An Inphase local oscillator (LO_I) signal and a quadrature phase local oscillator (LO_Q) signal are derived from a combination of a first signal and the phase information using a digital phase lock loop. A feedback receiver (FBR) receives the RF broadcast signal provided by the Polar TX. The LO_I signal and the LO_Q signal are mixed with the RF broadcast signal to obtain mixer output signals. RF path delay and IQ phase imbalance are concurrently determined as a function of the first signal and of the mixer output signals.

Claims

1. A polar transmitter system comprising:

a polar transmitter comprising

a radio frequency digital to analog converter (RFDAC) to receive phase modulation information and processed first amplitude modulation (AM) information to provide a radio frequency transmission signal for broadcast, and

oscillator circuitry configured to receive both a function of the phase modulation information and of a first signal, and to provide at least an Inphase local oscillator (LO_I) signal and a quadrature phase local oscillator (LO_Q) signal; and

a feedback receiver (FBR) comprising

a plurality of mixers to mix the radio frequency transmission signal with the LO_I signal and the LO_Q signal to obtain a plurality of mixer output signals,

processing circuitry to derive an AM component and a phase component from the plurality of mixer output signals, and

measuring circuitry to monitor at least one of the AM component or the phase component, as the first signal is varied, to concurrently determine, both an RF path delay and an IQ phase imbalance, each as a function of both the monitored at least one component and of the varied first signal.

2. The polar transmitter of claim 1 wherein the oscillator circuitry comprises a phase lock loop (PLL).

3. The polar transmitter (Polar TX) system of claim 2 wherein the measuring circuitry further derives at least a second AM information from at least one of the mixer output signals, varies the first signal and measures the variation of the second AM information as the first signal is varied to determine the RF path delay and the IQ phase imbalance.

4. The Polar TX system of claim 3 wherein the varied second AM information comprises a substantially sinusoid trajectory.

5. The Polar TX system of claim 4 wherein the second AM information is derived by coupling the mixer output signals to a coordinate rotation digital computer (CORDIC), the second AM information obtained as an output from the CORDIC.

6. The Polar TX system of claim 4 wherein the RF path delay is derived by calculating the difference in amplitude of the substantially sinusoid trajectory at two points of variation of the first signal and dividing the difference by a function of the first signal.

7. The Polar TX system of claim 4 wherein the first signal is an FM signal (FM_tune), the RF path delay is Δ

t, and the RF path delay is determined by calculating;

8. The Polar TX system of claim 4 wherein the first signal is an FM signal (FM tune) and the IQ phase imbalance is determined by increasing the value of FM tune in a plurality of discrete points for a full period of variation of the second AM information, the second AM information is measured as a function of each of the plurality of points, and the magnitude |e| of the IQ phase imbalance is calculated in terms of power as:

9. The Polar TX system of claim 8 wherein the sign of the IQ phase imbalance is calculated by comparing An measured at sequential quadrants of a constellation diagram for the variation of the second AM information.

10. The Polar TX system of claim 9 wherein the comparing is a subtraction process.

11. The Polar transmitter system of claim 2 wherein the RF signal provided by the Polar TX is received by the FBR.

12. A method of calibrating parameters in a polar transmitter (Polar TX) system comprising:

receiving phase information derived from transmission information in a Polar TX;

deriving an Inphase local oscillator (LO_I) signal and a quadrature phase local oscillator (LO_Q) signal from a combination of a first signal and the phase information;

receiving an RF signal provided by the Polar TX;

mixing the LO_I signal and the LO_Q signal with the RF signal to obtain mixer output signals;

deriving amplitude modulation (AM) information and phase information from the mixer output signals; and

concurrently determining, by monitoring at least the amplitude of the derived AM information, as the first signal is varied, both an RF path delay and an IQ phase imbalance in the Polar TX system, each as a function of the monitored derive AM information and of the varied first signal.

13. The method of claim 12 wherein the varying the first signal results in the amplitude of the derived AM information having a substantially sinusoid trajectory.

14. The method of claim 13, wherein determining the RF path delay comprises calculating the difference in amplitude of the derived AM information having the substantially sinusoid trajectory at two points of variation of the first signal and dividing the difference by a function of the first signal.

15. The method of claim 14 wherein the first signal is an FM signal (FM_tune), the RF path delay is Δ

t, and determining the RF path delay comprises calculating;

16. The method of claim 13 wherein the first signal is an FM signal (FM_tune) and determining the IQ phase imbalance comprises increasing the value of FM_tune in a plurality of discrete points for a full period of the derived AM Information, measuring the derived AM information as a function of each of the plurality of discrete points, and calculating the magnitude |e| of the IQ phase imbalance in terms of power as:

17. A cellular transceiver comprising:

a polar transmitter (Polar TX) to receive phase modulation information and processed first amplitude modulation (AM) information to provide a radio frequency transmission signal for broadcast, the Polar TX comprising

a phase lock loop (PLL) to receive both a function of the phase modulation information and of a first signal, to provide at least an Inphase local oscillator (LO_I) signal and a quadrature phase local oscillator (LO_Q) signal; and

a feedback receiver (FBR) comprising

a plurality of mixers to mix the radio frequency transmission signal with the LO_I signal and the LO_Q signal to obtain mixer output signals,

processing circuitry to derive an AM component and a phase component from the plurality of mixer output signals, and

measuring circuitry configured to monitor at least one of the AM component or the phase component, as the first signal is varied, to concurrently determine an RF path delay and an IQ phase imbalance, each as a function of both the monitored at least one component and of the varied first signal.

18. The cellular transceiver of claim 17 wherein the measuring circuitry further derives at least second AM information from at least one of the mixer output signals, and concurrently varies the first signal and measures the variation of the second AM information as the first signal is varied to determine the RF path delay and the IQ phase imbalance.

19. The cellular transceiver of claim 18 wherein the variation of the second AM information comprises a substantially sinusoid trajectory.

20. The cellular transceiver of claim 19 wherein the second AM information is derived by coupling the mixer output signals to a coordinate rotation digital computer (CORDIC) and obtaining the second AM information as an output from the CORDIC.

21. The cellular transceiver of claim 19 wherein the RF path delay is derived by calculating the difference in amplitude of the substantially sinusoid trajectory at two points of variation of the first signal and dividing the difference by a function of the first signal.

22. The cellular transceiver of claim 21 wherein the first signal is an FM signal (FM_tune), the RF path delay is Δ

t, and the RF path delay is determined by calculating;

23. The cellular transceiver of claim 19 wherein the first signal is an FM signal (FM_tune) and the IQ phase imbalance is determined by increasing the value of FM_tune in a plurality of discrete points for a full period of variation of the second AM information, measuring the second AM information as a function of each of the plurality of points, and calculating the magnitude |e| of the IQ phase imbalance in terms of power as:

24. The cellular transceiver of claim 23 wherein the sign of the IQ phase imbalance is calculated by comparing An measured at sequential quadrants of a constellation diagram for the variation of the second AM information.