Phase synchronization for round trip delay estimation
Phase variations between a transmitter (TX) waveform and a receiver (RX) waveform produced by a TX Phase-Locked-Loop (PLL) and a RX PLL, respectively, is a source of error in processing delay calibration used, e.g., in Round Trip Time (RTT) estimation. While a TX waveform and a RX waveform have a constant phase delay while in steady state conditions, during transient times, e.g., at start up or reset, the phase delay may vary by as much as ±180°, which at baseband frequencies of 50 MHz, introduces a random delay variations of as much as ±10 nsec, which is undesirable for fine position estimation using RTT. The phase delay variation between the TX waveform and RX waveform may be reduced or eliminated using a phase correction signal generated using the output signals of the TX PLL and RX PLL.
1. An entity in a wireless network, the entity being one of a mobile device or base station, the entity comprising:
a transmitter (TX) phase-locked loop (PLL) configured to receive a first clock signal from a reference clock and generate a TX waveform;
a receiver (RX) phase-locked loop (PLL) configured to receive a second clock signal from the reference clock and generate a RX waveform;
wherein one or both of the transmitter PLL and the receiver PLL is configured to receive a phase correction signal and to adjust a phase relationship between the TX waveform and the RX waveform based on the phase correction signal so that the TX waveform and the RX waveform have a same phase relationship each time the transmitter PLL and the receiver PLL achieve a steady-state condition.
2. The entity of claim 1 , further comprising:
a phase match estimation circuit configured to receive a third clock signal from the reference clock, the TX waveform, the RX waveform, the phase match estimation circuit configured to determine a phase relationship between the TX waveform and the RX waveform and to generate the phase correction signal to produce the phase relationship between the reference clock and the TX waveform.
3. The entity of claim 1 , wherein one of a transmitter loop filter or a transmitter ΣΔ modulator that controls a transmitter feedback divider in the transmitter PLL is configured to receive the phase correction signal and adjust a phase delay in the TX waveform, and wherein one of a receiver loop filter or a receiver ΣΔ modulator that controls a receiver feedback divider in the receiver PLL is configured to receive the phase correction signal and adjust a phase delay in the RX waveform.
4. The entity of claim 1 , further comprising:
a transmitter digital-to-analog converter configured to receive a third clock signal from a digital reference sampling clock;
a receiver analog-to-digital converter configured to receive a fourth clock signal from the digital reference sampling clock;
wherein a ratio of the first clock signal and the second clock signal is a rational number.
5. The entity of claim 4 , further comprising:
a first frequency divider coupled to the digital reference sampling clock that divides a clock signal from the digital reference sampling clock by N, wherein N is an integer, to produce the third clock signal received by the transmitter digital-to-analog converter; and
a second frequency divider coupled to the digital reference sampling clock that divides the clock signal from the digital reference sampling clock by M, wherein M is an integer, to produce the fourth clock signal received by the receiver analog-to-digital converter, wherein a ratio N/M is a rational number.
6. The entity of claim 4 , wherein the digital clock is configured to receive the phase correction signal and produce a digital clock signal based on the phase correction signal.
7. A method of calibration of an entity in a wireless network, the entity being one of a mobile device or base station, the method comprising:
providing a first clock signal from a reference clock to a transmitter (TX) phase-locked loop (PLL) that generates a TX waveform;
providing a second clock signal from the reference clock to a receiver (RX) PLL that generates a RX waveform;
generating a phase correction signal that is received by the transmitter PLL and the receiver PLL; and
adjusting a phase relationship between the TX waveform and the RX waveform based on the phase correction signal so that the TX waveform and the RX waveform have a same phase relationship each time the transmitter PLL and the receiver PLL achieve a steady-state condition.
8. The method of claim 7 , wherein generating the phase correction signal comprises:
receiving a third clock signal from the reference clock;
receiving the TX waveform;
receiving the RX waveform;
determining a phase relationship between the TX waveform and the RX waveform; and
generating the phase correction signal based on the phase relationship between the TX waveform and the RX waveform.
9. The method of claim 7 , wherein adjusting the phase relationship between the TX waveform and the RX waveform based on the phase correction signal comprises:
adjusting at least one of a transmitter loop filter or a transmitter ΣΔ modulator that controls a transmitter feedback divider in the transmitter PLL based on the phase correction signal to alter a phase delay in the TX waveform; and
adjusting one of a receiver loop filter or a receiver ΣΔ modulator that controls a receiver feedback divider in the receiver PLL based on the phase correction signal to alter a phase delay in the RX waveform.
10. The method of claim 7 , further comprising:
providing a third clock signal from a digital reference sampling clock to a transmitter digital-to-analog converter;
providing a fourth clock signal from the digital reference sampling clock to a receiver analog-to-digital converter;
wherein a ratio of the third clock signal and the fourth clock signal is a rational number.
11. The method of claim 10 , further comprising:
generating the third clock signal by dividing a clock signal from the digital reference sampling clock by N, wherein N is an integer; and
generating the fourth clock signal by dividing the clock signal from the digital reference sampling clock by M, wherein M is an integer, wherein a ratio N/M is a rational number.
12. The method of claim 10 , further comprising producing the clock signal from the digital reference sampling clock based on the phase correction signal.
13. An entity in a wireless network, the entity being one of a mobile device or base station, the entity comprising:
means for providing a first clock signal from a reference clock to a transmitter (TX) phase-locked loop (PLL) that generates a TX waveform;
means for providing a second clock signal from the reference clock to a receiver (RX) PLL that generates a RX waveform;
means for generating a phase correction signal that is received by the transmitter PLL and the receiver PLL; and
means for adjusting a phase relationship between the TX waveform and the RX waveform based on the phase correction signal so that the TX waveform and the RX waveform have a same phase relationship each time the transmitter PLL and the receiver PLL achieve a steady-state condition.
14. The entity of claim 13 , wherein the means for generating the phase correction signal comprises:
means for receiving a third clock signal from the reference clock;
means for receiving the TX waveform;
means for receiving the RX waveform;
means for determining a phase relationship between the TX waveform and the RX waveform; and
means for generating the phase correction signal based on the phase relationship between the TX waveform and the RX waveform.
15. The entity of claim 13 , wherein the means for adjusting the phase relationship between the TX waveform and the RX waveform based on the phase correction signal comprises:
means for adjusting at least one of a transmitter loop filter or a transmitter ΣΔ modulator that controls a transmitter feedback divider in the transmitter PLL based on the phase correction signal to alter a phase delay in the TX waveform; and
means for adjusting one of a receiver loop filter or a receiver ΣΔ modulator that controls a receiver feedback divider in the receiver PLL based on the phase correction signal to alter a phase delay in the RX waveform.
16. The entity of claim 13 , further comprising:
means for providing a third clock signal from a digital reference sampling clock to a transmitter digital-to-analog converter;
means for providing a fourth clock signal from the digital reference sampling clock to a receiver analog-to-digital converter;
wherein a ratio of the third clock signal and the fourth clock signal is a rational number.
17. The entity of claim 16 , further comprising:
means for generating the third clock signal by dividing a clock signal from the digital reference sampling clock by N, wherein N is an integer; and
means for generating the fourth clock signal by dividing the clock signal from the digital reference sampling clock by M, wherein M is an integer, wherein a ratio N/M is a rational number.
18. The entity of claim 16 , further comprising means for producing the clock signal from the digital reference sampling clock based on the phase correction signal.
19. A non-transitory storage medium including program code stored thereon, the program code is operable to control at least one processor in an entity in a wireless network, the entity being one of a mobile device or base station comprising:
wherein a first clock signal is provided from a reference clock to a transmitter (TX) phase-locked loop (PLL) that generates a TX waveform and a second clock signal is provided from the reference clock to a receiver (RX) PLL that generates a RX waveform;
program code to generate a phase correction signal that is received by the transmitter PLL and the receiver PLL; and
program code to adjust a phase relationship between the TX waveform and the RX waveform based on the phase correction signal so that the TX waveform and the RX waveform have a same phase relationship each time the transmitter PLL and the receiver PLL achieve a steady-state condition.
20. The non-transitory storage medium of claim 19 , wherein the program code to generate the phase correction signal comprises:
program code to receive a third clock signal from the reference clock;
program code to receive the TX waveform;
program code to receive the RX waveform;
program code to determine a phase relationship between the TX waveform and the RX waveform; and
program code to generate the phase correction signal based on the phase relationship between the TX waveform and the RX waveform.
21. The non-transitory storage medium of claim 19 , wherein the program code to adjust the phase relationship between the TX waveform and the RX waveform based on the phase correction signal comprises:
program code to adjust at least one of a transmitter loop filter or a transmitter ΣΔ modulator that controls a transmitter feedback divider in the transmitter PLL based on the phase correction signal to alter a phase delay in the TX waveform; and
program code to adjust one of a receiver loop filter or a receiver ΣΔ modulator that controls a receiver feedback divider in the receiver PLL based on the phase correction signal to alter a phase delay in the RX waveform.
22. The non-transitory storage medium of claim 19 , further comprising:
program code to providing a third clock signal from a digital reference sampling clock to a transmitter digital-to-analog converter;
program code to providing a fourth clock signal from the digital reference sampling clock to a receiver analog-to-digital converter;
wherein a ratio of the third clock signal and the fourth clock signal is a rational number.
23. The non-transitory storage medium of claim 22 , further comprising:
program code to generate the third clock signal by dividing a clock signal from the digital reference sampling clock by N, wherein N is an integer; and
program code to generate the fourth clock signal by dividing the clock signal from the digital reference sampling clock by M, wherein M is an integer, wherein a ratio N/M is a rational number.
24. The non-transitory storage medium of claim 22 , further comprising program code to produce the clock signal from the digital reference sampling clock based on the phase correction signal.