Phase-locked loop having a multi-band oscillator and method for calibrating same
A phase-locked loop (PLL) comprising a multi-band oscillator and a memory configured to store control input for the oscillator. The PLL is operable in a calibration mode in which the PLL is configured to acquire a frequency controlled word (FCW) for the PLL corresponding to a frequency generated by the oscillator in response to a first control input threshold on a first band of the oscillator; generate a frequency corresponding to said FCW on a second band of the oscillator adjacent to said first band; identify a second control input causing the oscillator to generate said frequency corresponding to said FCW and store said second control input in memory.
1. A phase-locked loop (PLL) that is re-configurable for calibration, the PLL comprising:
an input of the PLL configured to receive a frequency controlled word (FCW);
a multi-band oscillator, a loop filter, and a memory configured to store a control input value for the multi-band oscillator;
wherein the PLL is operable in a calibration mode to provide an output from the loop filter to the input of the PLL to thereby acquire a value for the FCW based on the output from the loop filter, and wherein an output of the multi-band oscillator is coupled to an input of the loop filter;
wherein the PLL is operable to provide the output from the loop filter to the multi-band oscillator and to determine the control input value based on providing the value for the FCW to the input of the PLL; and
wherein the PLL is configured to provide a control input threshold value to a fine control input of the multi-band oscillator in the calibration mode while the multi-band oscillator operates in a first band.
2. The PLL of claim 1 , wherein the loop filter is configured to provide the output to the fine control input of said multi-band oscillator and to provide a second output to a coarse control input of the multi-band oscillator in a normal mode of operation of the PLL.
3. The PLL of claim 1 , wherein the multi-band oscillator is configured to generate a frequency corresponding to the value for the FCW when the control input threshold value is provided to the fine control input in the calibration mode while the multi-band oscillator operates in the first band; and
wherein the PLL is configured to change to the normal mode and identify the control input value that causes the multi-band oscillator to generate the frequency corresponding to the value for the FCW while operating the multi-band oscillator in a second band to generate the frequency corresponding to the value for the FCW, the second band being adjacent to the first band.
4. The PLL of claim 1 , wherein prior to said acquiring of the value for the FCW, the PLL is further configured to set the fine control input of the multi- band oscillator to the control input threshold value.
5. The PLL of claim 1 , wherein for each band of the multi- band oscillator, the PLL is further configured to store in said memory a respective control input value that, when provided to the multi-band oscillator, causes the multi-band oscillator to generate a respective value for the FCW on another adjacent band of the multi-band oscillator.
6. The PLL of claim 4 , wherein the PLL is a digital PLL, and wherein the multi-band oscillator is a Digitally Controlled Oscillator (DCO) configured to receive a coarse digital control input and a fine digital control input, the control input threshold value being provided for the fine digital control input.
7. A frequency modulated continuous wave (FMCW) radar device comprising:
a transceiver configured to transmit and receive a frequency ramp signal;
a frequency ramp generator configured to produce the frequency ramp signal, the frequency ramp generator comprising a phase-locked loop (PLL) comprising:
a multi-band oscillator,
a loop filter,
a memory configured to store a control input value for providing to a control input for the multi-band oscillator, and
a phase accumulator comprising an input of the PLL configured to receive a frequency controlled word (FCW);
wherein the PLL is operable in a calibration mode in which the PLL is configured to provide an output from the loop filter to an input of the PLL to thereby acquire a value for the FCW and wherein an output of the multi-band oscillator is coupled to an input of the loop filter; and
wherein the PLL is operable to provide the output from the loop filter to the multi-band oscillator and to determine the control input value based on providing the value for the FCW to the input of the PLL.
8. The FMCW radar device of claim 7 , wherein the loop filter is further configured to provide a second output to a coarse control input of the multi-band oscillator, and wherein the control input is a fine control input of the multi-band oscillator.
9. The FMCW radar device of claim 8 , wherein the PLL is further configured to:
generate a frequency corresponding to the value for the FCW when a control input threshold value is provided to the fine control input while the multi-band oscillator operates in a first coarse band while the PLL is in the calibration mode;
determine the control input value based on providing the value for the FCW to the input of the PLL while the multi-band oscillator generates the frequency while operating in a second coarse band that is adjacent to the first coarse band while the PLL is in the normal mode; and
store the control input value into the memory.
10. The FMCW radar device of claim 9 , wherein the PLL is configured to perform the acquiring, the generating, the determining of the control input values, and the storing for each band of the multi-band oscillator successively.
11. The FMCW radar device of claim 7 , wherein prior to said acquiring of the value for the FCW, the PLL is further configured to set the control input of the multi-band oscillator to have a control input threshold value.
12. The FMCW radar device of claim 7 , wherein for each band of the multi-band oscillator, the PLL is configured to store in said memory a respective control input generating respective values for said FCW on a respective adjacent band of the multi-band oscillator.
13. The FMCW radar device of claim 7 , wherein the PLL is a digital PLL, the multi-band oscillator is a Digitally Controlled Oscillator (DCO) configured to receive a coarse digital control input and a fine digital control input.
14. A vehicle comprising the frequency modulated continuous (FMCW) radar device of claim 7 .
15. A frequency calibration method for calibrating a phase- locked loop (PLL) comprising a multi-band oscillator, the method comprising:
coupling an output of a loop filter of the PLL to an input of the PLL in a calibration mode, wherein the input of the PLL is configured to receive a frequency controlled word (FCW) in a second mode;
acquiring a value for the FCW based on an output of the loop filter while an output of the multi-band oscillator is coupled to an input of the loop filter and a first control input threshold value is provided on a first band of the multi-band oscillator;
generating a frequency corresponding to the value for the FCW on a second band of the multi-band oscillator adjacent to said first band; and
identifying and storing a second control input value for the second band that, when provided to the multi-band oscillator, causes the multi-band oscillator to generate said frequency corresponding to the value for the FCW.
16. The method of claim 15 , wherein the frequency corresponding to the value for the FCW is generated on the second band of the multi-band oscillator while the output of the loop filter is coupled to an input of the multi-band oscillator.
17. The method of claim 15 , further comprising prior to said acquiring of the value for the FCW, setting a fine control input of the multi-band oscillator to have said first control input threshold value.
18. The method of claim 15 , wherein the acquiring, the generating, the identifying, and the storing are performed for each band of the multi-band oscillator.
19. The method of claim 15 , further comprising, for each band of the multi-band oscillator: storing in a look-up table a further control input value that causes the multi-band oscillator to generate the value for the FCW on another adjacent band of the multi- band oscillator.
20. The method of claim 15 , wherein the PLL is a digital PLL, the multi-band oscillator is a Digitally Controlled Oscillator (DCO) and the method comprises receiving a coarse digital control input and a fine digital control input.
21. The PLL of claim 1 , wherein the PLL comprises a phase accumulator, and the input of PLL is an input of the phase accumulator.
22. The method of claim 15 , wherein said coupling comprises coupling the output of the loop filter to an input of a phase accumulator of the PLL.
23. A phase-locked loop (PLL) that is re-configurable for calibration, the PLL comprising:
an input of the PLL configured to receive a frequency controlled word (FCW);
a multi-band oscillator, a loop filter, and a memory configured to store a control input value for the multi-band oscillator;
wherein the PLL is operable in a calibration mode to provide an output from the loop filter to the input of the PLL to thereby acquire a value for the FCW based on the output from the loop filter, and wherein an output of the multi-band oscillator is coupled to an input of the loop filter;
wherein the PLL is operable to provide the output from the loop filter to the multi- band oscillator and to determine the control input value based on providing the value for the FCW to the input of the PLL; and
wherein prior to said acquiring of the value for the FCW, the PLL is further configured to set a fine control input of the multi-band oscillator to a control input threshold value.
24. The PLL of claim 23 , wherein the PLL is a digital PLL, and wherein the multi-band oscillator is a Digitally Controlled Oscillator (DCO) configured to receive a coarse digital control input and the fine control input.
25. The PLL of claim 1 , wherein the PLL comprises a phase accumulator, and the input of PLL is an input of the phase accumulator.
26. The PLL of claim 23 , wherein the PLL is configured to provide the control input threshold value to the fine control input of the multi-band oscillator in the calibration mode while the multi-band oscillator operates in a first band.