Phase-locked loop automatic frequency calibration method, device and circuit

Abstract

The present invention provides a phase-locked loop automatic frequency calibration method, device and circuit. The phase-locked loop comprises: a capacitor-inductor oscillator; the phase-locked loop automatic frequency calibration method comprises: after starting the phase-locked loop, configuring the phase-locked loop operating frequency, connecting the capacitor-inductor oscillator to an open-loop calibration reference input voltage to enter an open-loop calibration mode, and obtaining an output high-frequency signal; according to the frequency difference between a low-frequency signal corresponding to the high-frequency signal and a reference signal corresponding to the low-frequency signal, performing an open-loop calibration on a capacitor array of the capacitor-inductor oscillator, and then entering a closed-loop calibration mode; real-time monitoring of whether the phase-locked loop operating frequency changes, if the phase-locked loop operating frequency remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop enters a closed-loop operating mode; if the phase-locked loop operating frequency remains unchanged and the phase-locked loop is in an unlocked state, performing a closed-loop online calibration on the capacitor array; the present invention can improve the efficiency and accuracy of the phase-locked loop automatic calibration, thereby improving the applicability in practical applications.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a method, device and circuit for automatic frequency calibration of a phase-locked loop. Background Art

[0002] In the field of phase-locked loop (PLL) technology, automatic frequency calibration (AFC) technology is a crucial technology that affects the operation and locking time of the phase-locked loop. The current main automatic frequency calibration technologies include: closed-loop automatic frequency calibration and open-loop automatic frequency calibration. Closed-loop automatic frequency calibration refers to the automatic calibration of the capacitor array of the voltage-controlled oscillator (VCO) through a feedback mechanism, which is usually achieved by monitoring the input control voltage of the voltage-controlled oscillator. Open-loop automatic frequency calibration refers to the calibration of the capacitor array of the voltage-controlled oscillator through a specific algorithm or calibration signal when the voltage-controlled oscillator works in open-loop mode, and the target operating frequency is achieved after the phase-locked loop is closed.

[0003] However, both automatic frequency calibration technologies have some shortcomings and application limitations. The frequency range that can be calibrated by closed-loop automatic frequency calibration is usually relatively small, and it is difficult to meet the requirements for fast calibration of the capacitor array of the voltage-controlled oscillator of a wideband phase-locked loop. Although the open-loop automatic frequency calibration is relatively fast in the calibration of a wideband phase-locked loop, in actual applications, when affected by environmental changes and device parameter drift, the voltage-controlled oscillator capacitor array after open-loop calibration becomes unsuitable, resulting in the loss of phase-locked loop lock. After the loss of lock, it takes a long time to re-perform the open-loop automatic frequency calibration. Therefore, the current closed-loop and open-loop automatic frequency calibration technologies have certain limitations in practical applications. Summary of the invention

[0004] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to propose a method, device and circuit for automatic frequency calibration of a phase-locked loop, which can improve the efficiency and accuracy of automatic calibration of the phase-locked loop.

[0005] In a first aspect, the present invention provides a phase-locked loop automatic frequency calibration method, the phase-locked loop comprising: a capacitor-inductor oscillator; the phase-locked loop automatic frequency calibration method comprising:

[0006] After the phase-locked loop is turned on, the operating frequency of the phase-locked loop is configured, and the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter the open-loop calibration mode to obtain the output high-frequency signal;

[0007] According to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, an open-loop calibration is performed on the capacitor array of the capacitor-inductor oscillator, and then a closed-loop calibration mode is entered;

[0008] Real-time monitoring of whether the operating frequency of the phase-locked loop changes, if the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop enters a closed-loop operating mode;

[0009] If the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in an unlocked state, a closed-loop online calibration is performed on the capacitor array.

[0010] The present invention performs open-loop calibration on a phase-locked loop that is powered on for the first time, which can meet the calibration scenario of a wideband phase-locked loop corresponding to a capacitor array, and enters a closed-loop calibration mode after the open-loop calibration, which can avoid the first open-loop calibration being easily affected by environmental changes and device parameter drift, thereby improving the calibration accuracy. After adopting simultaneous open-loop calibration and closed-loop calibration, the calibration adjustment is performed by real-time monitoring of the phase-locked loop locking state and the phase-locked loop operating frequency, which can further improve the calibration accuracy and the applicability of the simultaneous open-loop calibration and closed-loop calibration in actual scenarios.

[0011] Further, the real-time monitoring of whether the operating frequency of the phase-locked loop changes also includes:

[0012] If the phase loop operating frequency changes, and the change value compared with the original phase-locked loop operating frequency exceeds a preset threshold, the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter the open-loop calibration mode; the preset threshold is a reference frequency value obtained by comparing the locking time of the closed-loop calibration mode with that of the open-loop calibration mode.

[0013] The present invention can not only perform open-loop calibration for the first time to adapt to wideband phase-locked loop calibration, but also monitor the phase-locked loop locking state and the phase-locked loop operating frequency in real time, and can intelligently switch to closed-loop calibration when affected by environmental changes and device parameter drift. Therefore, the present invention can improve the applicability of closed-loop calibration and open-loop calibration in different application scenarios.

[0014] Further, the real-time monitoring of whether the operating frequency of the phase-locked loop changes also includes:

[0015] If the phase loop operating frequency changes, and the change value does not exceed the preset threshold, the capacitor-inductor oscillator is connected to the control voltage to enter a closed-loop calibration mode.

[0016] Further, the step of performing an open-loop calibration on the capacitor array of the capacitor-inductor oscillator according to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, and then entering a closed-loop calibration mode, includes:

[0017] According to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, an open-loop calibration is performed on the capacitor array of the capacitor-inductor oscillator to obtain an optimal offline calibration value, the capacitor-inductor oscillator is connected to a control voltage to enter a closed-loop calibration mode, and in the closed-loop calibration mode, the optimal offline calibration value is maintained.

[0018] Further, obtaining a frequency difference between the high frequency signal and a low frequency signal corresponding to the high frequency signal includes:

[0019] The high frequency signal is divided to obtain a low frequency signal, and the count of the low frequency signal and a reference signal corresponding to the low frequency signal in a period is obtained, and the difference between the count result of the low frequency signal and the count result of the low frequency signal is taken as the frequency difference.

[0020] Further, the open-loop calibration of the capacitor array of the capacitor-inductor oscillator to obtain an optimal offline calibration value includes:

[0021] According to the frequency difference, a plurality of digital control signals in the capacitor array of the capacitor-inductor oscillator and the variable capacitance of the capacitor-inductor oscillator are adjusted respectively to obtain an optimal offline calibration value of the capacitor array.

[0022] Further, the phase-locked loop is in a locked state, including: if the control voltage is monitored in real time within the preset voltage upper and lower limits, the phase-locked loop is in a locked state; otherwise, the phase-locked loop is in an unlocked state; wherein the closed-loop online calibration of the capacitor array includes:

[0023] The capacitor array is calibrated online in a closed loop according to the control voltage monitored in real time, and the optimal offline calibration value is re-acquired. The capacitor inductor oscillator is connected to the control voltage to make the phase-locked loop enter the closed-loop working mode, and the phase-locked loop working frequency and locking state are monitored in real time again.

[0024] In a second aspect, the present invention provides a phase-locked loop automatic frequency calibration device, the phase-locked loop comprising: a capacitor-inductor oscillator; the phase-locked loop automatic frequency calibration device comprising: an open-loop calibration unit, a closed-loop calibration unit, a real-time monitoring unit and an online calibration unit; wherein,

[0025] The open-loop calibration unit is used to configure the operating frequency of the phase-locked loop after the phase-locked loop is turned on, and connect the capacitor-inductor oscillator to the open-loop calibration reference input voltage to enter the open-loop calibration mode, and obtain the output high-frequency signal;

[0026] A closed-loop calibration unit, configured to perform an open-loop calibration on the capacitor array of the capacitor-inductor oscillator according to a frequency difference between a low-frequency signal corresponding to the high-frequency signal and a reference signal corresponding to the low-frequency signal, and then enter a closed-loop calibration mode;

[0027] The real-time monitoring unit is used to monitor in real time whether the operating frequency of the phase-locked loop changes. If the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop enters a closed-loop operating mode;

[0028] The online calibration unit is used to perform closed-loop online calibration on the capacitor array if the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in an unlocked state.

[0029] In a third aspect, the present invention provides a phase-locked loop automatic frequency calibration circuit, comprising: a counter, an automatic frequency calibration offline control module, a capacitor-inductor oscillator, an automatic frequency calibration online control module and a phase-locked loop control center; wherein,

[0030] The phase-locked loop control center is used to configure the phase-locked loop operating frequency after the phase-locked loop is turned on;

[0031] The capacitor-inductor oscillator is used to access an open-loop calibration reference input voltage or a control voltage through a switchable switch. If the switchable switch is connected to the open-loop calibration reference input voltage, it enters an open-loop calibration mode through connection with the automatic frequency calibration offline control module and outputs a high-frequency signal;

[0032] The counter is used to obtain a frequency difference between the low-frequency signal corresponding to the high-frequency signal and a reference signal corresponding to the low-frequency signal;

[0033] The automatic frequency calibration offline control module is used to perform open-loop calibration on the capacitor array of the capacitor-inductor oscillator;

[0034] The automatic frequency calibration online control module is used to change the switchable switch from the open-loop calibration reference input voltage to the control voltage to enter the closed-loop calibration mode;

[0035] The phase-locked loop control center is also used to monitor in real time whether the operating frequency of the phase-locked loop changes. If the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop is kept working and the automatic frequency calibration online control module is controlled to monitor the locking state in real time; if the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in an unlocked state, the automatic frequency calibration online control module is controlled to perform closed-loop online calibration on the capacitor array.

[0036] The present invention adopts an open-loop automatic frequency calibration through an automatic frequency calibration offline control module when it is powered on for the first time, which can provide a faster locking frequency for a phase-locked loop used for the first time and meet the calibration requirements of a broadband phase-locked loop; then a closed-loop calibration is performed through an automatic frequency calibration online control module. After the frequency is locked, the operating frequency of the phase-locked loop may change due to changes in the use environment or fine-tuning of the operating frequency of the phase-locked loop. The closed-loop online calibration is performed by entering the automatic frequency calibration online control module through the phase-locked loop control center, which can avoid the influence of environmental parameters and device parameter drift when only using open-loop automatic frequency calibration, thereby improving the accuracy of the phase-locked loop automatic calibration, meeting not only the requirements of open-loop calibration scenarios, but also the requirements of closed-loop calibration scenarios, thereby improving the applicability of phase-locked loop calibration.

[0037] Furthermore, the capacitor array includes: multiple groups of parallel control switches, and two groups of capacitors controlled by each group of control switches; wherein, the multiple control switches in the capacitor array and the variable capacitor of the capacitor-inductor oscillator are adjusted respectively, so that the capacitor-inductor oscillator outputs high-frequency signals with different operating frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a flow chart of a phase-locked loop automatic frequency calibration method provided in this embodiment;

[0039] Figure 2 is a complete flow chart of another phase-locked loop automatic frequency calibration method provided by this embodiment;

[0040] Figure 3 is a schematic structural diagram of a phase-locked loop automatic frequency calibration device provided in this embodiment;

[0041] Figure 4 is a schematic structural diagram of a phase-locked loop automatic frequency calibration circuit provided in this embodiment;

[0042] Figure 5 Schematic diagram of a circuit of a capacitor-inductor oscillator provided in this embodiment. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] It is worth noting that in order to solve the problems existing in the existing closed-loop automatic frequency calibration technology and open-loop automatic frequency calibration technology of the phase-locked loop, the present invention provides an intelligent phase-locked loop automatic frequency calibration method, device and circuit. When the open-loop automatic frequency calibration is used for the first time when it is powered on, a faster locking frequency is provided; after the frequency is locked, the closed-loop automatic frequency calibration quickly completes the frequency calibration due to changes in the use environment or fine-tuning of the phase-locked loop operating frequency; when the change in the phase-locked loop operating frequency exceeds the threshold, it is faster to use the open-loop automatic frequency calibration, then the open-loop automatic frequency calibration is intelligently switched to, thereby realizing the intelligent switching of the automatic frequency calibration mode of the phase-locked loop, which is conducive to improving the locking speed of the phase-locked loop in different application environments, thereby improving the calibration efficiency and accuracy of the phase-locked loop.

[0045] Example 1

[0046] See also Figure 1 , is a flow chart of a phase-locked loop automatic frequency calibration method provided in this embodiment, the phase-locked loop includes: a capacitor-inductor oscillator; the phase-locked loop automatic frequency calibration method includes: steps S11 to S14, specifically:

[0047] Step S11, after the phase-locked loop is turned on, the operating frequency of the phase-locked loop is configured, and the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter the open-loop calibration mode, and the output high-frequency signal is obtained.

[0048] Step S12: performing an open-loop calibration on the capacitor array of the capacitor-inductor oscillator according to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, and then entering a closed-loop calibration mode.

[0049] In some embodiments, after performing an open-loop calibration on the capacitor array of the capacitor and inductor oscillator according to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, a closed-loop calibration mode is entered, including: performing an open-loop calibration on the capacitor array of the capacitor and inductor oscillator according to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal to obtain an optimal offline calibration value, connecting the capacitor and inductor oscillator to a control voltage to enter a closed-loop calibration mode, and maintaining the optimal offline calibration value in the closed-loop calibration mode.

[0050] In some embodiments, obtaining the frequency difference between a high-frequency signal and a low-frequency signal corresponding to the high-frequency signal includes: dividing the high-frequency signal to obtain a low-frequency signal, and simultaneously obtaining the count of the low-frequency signal and a reference signal corresponding to the low-frequency signal in a period, and taking the difference between the count result of the low-frequency signal and the count result of the low-frequency signal as the frequency difference.

[0051] In some embodiments, an open-loop calibration is performed on the capacitor array of the capacitor-inductor oscillator to obtain an optimal offline calibration value, including: adjusting multiple digital control signals in the capacitor array of the capacitor-inductor oscillator and the variable capacitance of the capacitor-inductor oscillator respectively according to frequency differences to obtain the optimal offline calibration value of the capacitor array.

[0052] In some embodiments, it is assumed that the capacitor-inductor oscillator has a 6-bit controlled capacitor array Cap Array, and the 6-bit controlled capacitor array Cap Array is initialized to 100000 before calibration. The capacitance of the capacitor array Cap Array is judged to be too large or too small based on the count values ​​of the comparison counter A and the counter B, and the digital control signal of the capacitor array Cap Array is gradually adjusted to finally obtain an optimal offline calibration value to complete the open-loop calibration of the capacitor array of the capacitor-inductor oscillator.

[0053] In some embodiments, the digital control signal of the capacitor array Cap Array is represented by Capsel <n:0>, which means that by Capsel <0> , Capsel <1> …Capsel <n>The n+1 digital control signals composed of the switches S0, S1...Sn are used to control the switches S0, S1...Sn respectively.

[0054] Step S13: monitor in real time whether the operating frequency of the phase-locked loop changes; if the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop enters a closed-loop operating mode.

[0055] In some embodiments, the phase-locked loop is in a locked state, including: if the control voltage is monitored in real time to be within the preset voltage upper and lower limits, the phase-locked loop is in a locked state; otherwise, the phase-locked loop is in an unlocked state.

[0056] In some embodiments, if the operating frequency of the phase-locked loop remains unchanged and the control voltage is monitored in real time to be within the preset voltage upper and lower limits, the phase-locked loop enters a closed-loop operating mode, and in the closed-loop operating mode of the phase-locked loop, the locking state of the phase-locked loop is monitored in real time. That is, in the closed-loop operating mode of the phase-locked loop, whether the control voltage is within the preset voltage upper and lower limits is monitored in real time.

[0057] Step S14: If the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in an unlocked state, a closed-loop online calibration is performed on the capacitor array.

[0058] In some embodiments, closed-loop online calibration is performed on the capacitor array, including: performing closed-loop online calibration on the capacitor array according to a control voltage monitored in real time, re-obtaining an optimal offline calibration value, and after the closed-loop online calibration of the capacitor array, connecting the capacitor inductor oscillator to the control voltage to put the phase-locked loop into a closed-loop operating mode, and then re-monitoring the phase-locked loop operating frequency and locking state in real time.

[0059] In some embodiments, if the operating frequency of the phase-locked loop remains unchanged and the control voltage is monitored in real time to be within the preset voltage upper and lower limits, the capacitor array is calibrated online in a closed loop based on the control voltage monitored in real time to obtain the optimal offline calibration value, and then the capacitor-inductor oscillator is connected to the control voltage to put the phase-locked loop into a closed-loop operating mode, and the control voltage is again monitored in real time to see if it is within the preset voltage upper and lower limits.

[0060] In some embodiments, if the operating frequency of the phase-locked loop changes, and the change value compared with the original phase-locked loop operating frequency exceeds a preset threshold, the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter the open-loop calibration mode; the preset threshold is a reference frequency value obtained by comparing the locking time of the closed-loop calibration mode and the open-loop calibration mode.

[0061] In some embodiments, if the operating frequency of the phase-locked loop changes and the change value does not exceed a preset threshold, the capacitor-inductor oscillator is connected to the control voltage to enter a closed-loop calibration mode.

[0062] In some embodiments, see Figure 2 , is a complete flow chart of another phase-locked loop automatic frequency calibration method provided in this embodiment, including: steps S101 to S108, specifically:

[0063] Step S101: After the phase-locked loop is turned on, the phase-locked loop operating frequency is configured through the phase-locked loop control center.

[0064] Step S102, first, the input voltage port Vin of the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage Vref, the phase-locked loop enters the open-loop calibration mode, the capacitor-inductor oscillator outputs a high-frequency signal for the input open-loop calibration reference input voltage Vref, and then divides the output high-frequency signal to obtain a low-frequency signal, the low-frequency signal and the reference signal corresponding to the low-frequency signal are counted within a period, the difference between the counting result of the low-frequency signal and the counting result of the low-frequency signal is taken as the frequency difference, and the capacitor array Cap Array of the capacitor-inductor oscillator is open-loop calibrated according to the frequency difference.

[0065] Step S103, obtaining the best offline calibration value of the capacitor array Cap Array through the phase-locked loop open-loop automatic frequency calibration mode, and using it as the last control word used by the capacitor array Cap Array to obtain the best capacitor array Cap Array size of the capacitor-inductor oscillator after the phase-locked loop open-loop calibration.

[0066] Step S104: Connect the input voltage port Vin of the capacitor-inductor oscillator to the control voltage Vtune, the phase-locked loop enters a closed-loop operation mode, the capacitor array Cap Array maintains the optimal offline calibration value control, and monitors the locking state of the phase-locked loop in real time. The locking state of the phase-locked loop is monitored in real time according to the real-time monitoring of the control voltage Vtune.

[0067] Step S105, monitoring whether the operating frequency of the phase-locked loop is adjusted externally, if the operating frequency of the phase-locked loop remains unchanged, proceeding to step S106, otherwise proceeding to step S107.

[0068] Step S106: Determine the locked state of the phase-locked loop. If V L ≤Vtune≤V H If established, the process goes to step S104; wherein V H and V L are the preset voltage upper and lower limits respectively; if V L ≤Vtune≤V H If not established, proceed to step S108.

[0069] Step S108, the phase-locked loop is in a unlocked state, and at this time, the capacitor array of the capacitor-inductor oscillator is calibrated online in a closed loop according to the preset voltage upper and lower limits and the real-time monitored control voltage Vtune, and the best offline calibration value is adjusted, and then the process goes to step S104. For example, the capacitor array Cap Array originally 100000 is adjusted to 101100.

[0070] Step S107, determine whether the change value between the adjusted phase-locked loop operating frequency and the original phase-locked loop operating frequency exceeds a preset threshold; wherein the preset threshold is a reference frequency value obtained by comparing the locking time of the closed-loop automatic calibration algorithm and the open-loop automatic calibration algorithm. When the change value is greater than the preset threshold, enter step S102. wherein at this time, the locking time of the open-loop automatic calibration algorithm is shorter than the locking time of the closed-loop automatic calibration algorithm, the input voltage port Vin of the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage Vref, the phase-locked loop enters the open-loop calibration mode, and after re-counting, the capacitor array of the capacitor-inductor oscillator is open-loop calibrated.

[0071] Otherwise, when the change value is less than the threshold, the process goes to step S104. The closed-loop automatic calibration algorithm has a shorter locking time than the open-loop automatic calibration algorithm, the input voltage port Vin of the capacitor-inductor oscillator is switched from the open-loop calibration reference input voltage Vref to the control voltage Vtune, the phase-locked loop enters the closed-loop working mode, and the locking state of the phase-locked loop is monitored in real time.

[0072] The present invention performs open-loop calibration on a phase-locked loop that is powered on for the first time, which can meet the calibration scenario of a wideband phase-locked loop corresponding to a capacitor array, and enters a closed-loop calibration mode after the open-loop calibration, which can avoid the first open-loop calibration being easily affected by environmental changes and device parameter drift, thereby improving the calibration accuracy. After adopting simultaneous open-loop calibration and closed-loop calibration, the calibration adjustment is performed by real-time monitoring of the phase-locked loop locking state and the phase-locked loop operating frequency, which can further improve the calibration accuracy and the applicability of the simultaneous open-loop calibration and closed-loop calibration in actual scenarios.

[0073] Example 2

[0074] See also Figure 3 , is a structural schematic diagram of a phase-locked loop automatic frequency calibration device provided in this embodiment, the phase-locked loop includes: a capacitor-inductor oscillator; the phase-locked loop automatic frequency calibration device includes: an open-loop calibration unit 21, a closed-loop calibration unit 22, a real-time monitoring unit 23 and an online calibration unit 24.

[0075] The open-loop calibration unit 21 is used to configure the operating frequency of the phase-locked loop after starting the phase-locked loop, and connect the capacitor-inductor oscillator to the open-loop calibration reference input voltage to enter the open-loop calibration mode to obtain the output high-frequency signal.

[0076] The closed-loop calibration unit 22 is used to perform an open-loop calibration on the capacitor array of the capacitor-inductor oscillator according to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, and then enter a closed-loop calibration mode.

[0077] In some embodiments, after performing an open-loop calibration on the capacitor array of the capacitor and inductor oscillator according to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, a closed-loop calibration mode is entered, including: performing an open-loop calibration on the capacitor array of the capacitor and inductor oscillator according to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal to obtain an optimal offline calibration value, connecting the capacitor and inductor oscillator to a control voltage to enter a closed-loop calibration mode, and maintaining the optimal offline calibration value in the closed-loop calibration mode.

[0078] In some embodiments, obtaining the frequency difference between a high-frequency signal and a low-frequency signal corresponding to the high-frequency signal includes: dividing the high-frequency signal to obtain a low-frequency signal, and simultaneously obtaining the count of the low-frequency signal and a reference signal corresponding to the low-frequency signal in a period, and taking the difference between the count result of the low-frequency signal and the count result of the low-frequency signal as the frequency difference.

[0079] In some embodiments, an open-loop calibration is performed on the capacitor array of the capacitor-inductor oscillator to obtain an optimal offline calibration value, including: adjusting multiple digital control signals in the capacitor array of the capacitor-inductor oscillator and the variable capacitance of the capacitor-inductor oscillator respectively according to frequency differences to obtain the optimal offline calibration value of the capacitor array.

[0080] The real-time monitoring unit 23 is used to monitor in real time whether the operating frequency of the phase-locked loop changes. If the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop enters a closed-loop operating mode.

[0081] In some embodiments, the phase-locked loop is in a locked state, including: if the control voltage is monitored in real time to be within the preset voltage upper and lower limits, the phase-locked loop is in a locked state; otherwise, the phase-locked loop is in an unlocked state.

[0082] The online calibration unit 24 is used to perform a closed-loop online calibration on the capacitor array if the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in an unlocked state.

[0083] In some embodiments, a closed-loop online calibration is performed on the capacitor array, including: performing a closed-loop online calibration on the capacitor array according to a control voltage monitored in real time, reacquiring an optimal offline calibration value, and connecting the capacitor inductor oscillator to the control voltage to allow the phase-locked loop to enter a closed-loop operating mode, and then re-monitoring the phase-locked loop operating frequency and locking state in real time.

[0084] In some embodiments, if the operating frequency of the phase-locked loop changes, and the change value compared with the original phase-locked loop operating frequency exceeds a preset threshold, the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter the open-loop calibration mode; the preset threshold is a reference frequency value obtained by comparing the locking time of the closed-loop calibration mode and the open-loop calibration mode.

[0085] In some embodiments, if the operating frequency of the phase-locked loop changes and the change value does not exceed a preset threshold, the capacitor-inductor oscillator is connected to the control voltage to enter a closed-loop calibration mode.

[0086] The present invention performs open-loop calibration on a phase-locked loop that is powered on for the first time, which can meet the calibration scenario of a wideband phase-locked loop corresponding to a capacitor array, and enters a closed-loop calibration mode after the open-loop calibration, which can avoid the first open-loop calibration being easily affected by environmental changes and device parameter drift, thereby improving the calibration accuracy. After adopting simultaneous open-loop calibration and closed-loop calibration, the calibration adjustment is performed by real-time monitoring of the phase-locked loop locking state and the phase-locked loop operating frequency, which can further improve the calibration accuracy and the applicability of the simultaneous open-loop calibration and closed-loop calibration in actual scenarios.

[0087] Example 3

[0088] This embodiment provides a phase-locked loop automatic frequency calibration circuit, including: a counter 301, an automatic frequency calibration offline control module (AFC Offline) 302, a capacitor-inductor oscillator 303, an automatic frequency calibration online control module (AFCOnline) 304 and a phase-locked loop control center 305.

[0089] In some embodiments, the phase-locked loop control center 305 is used to configure the phase-locked loop operating frequency after the phase-locked loop is turned on.

[0090] In some embodiments, the capacitor-inductor oscillator 303 is used to connect to an open-loop calibration reference input voltage or a control voltage through a switchable switch. If the switchable switch is connected to the open-loop calibration reference input voltage, it enters an open-loop calibration mode through connection with the automatic frequency calibration offline control module 302 and outputs a high-frequency signal.

[0091] In some embodiments, the capacitor-inductor oscillator 303 outputs a high-frequency oscillation signal F VCO , its oscillation frequency is controlled by the input voltage port Vin.

[0092] In some embodiments, the counter 301 is used to obtain a frequency difference between a low-frequency signal corresponding to the high-frequency signal and a reference signal corresponding to the low-frequency signal.

[0093] In some embodiments, the automatic frequency calibration offline control module 302 is used to perform an open-loop calibration on the capacitor array of the capacitor-inductor oscillator 303;

[0094] In some embodiments, the automatic frequency calibration online control module 304 is used to switch the switch from the open-loop calibration reference input voltage to the control voltage to enter the closed-loop calibration mode. 。

[0095] In some embodiments, the phase-locked loop control center 305 is also used to monitor in real time whether the phase-locked loop operating frequency changes. If the phase-locked loop operating frequency remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop is kept working and the automatic frequency calibration online control module 304 is controlled to enter a closed-loop calibration mode; if the phase-locked loop operating frequency remains unchanged and the phase-locked loop is in an unlocked state, the automatic frequency calibration online control module 304 is controlled to perform a closed-loop online calibration on the capacitor array.

[0096] In some embodiments, the phase-locked loop automatic frequency calibration circuit also includes: a phase / frequency detector 306 (Phase / Frequency Detector, PFD), a charge pump 307 (Charge Pump, CP), a loop filter 308 (Loop Filter, LF), a feedback divider 309 (Feedback Divider) and a comparator (Comparator, CMP) 310.

[0097] See also Figure 4 , is a structural schematic diagram of a phase-locked loop automatic frequency calibration circuit provided in this embodiment, which integrates a closed-loop automatic frequency calibration circuit (blue part) and an open-loop automatic frequency calibration circuit (red part), and realizes intelligent switching of open-loop / closed-loop automatic frequency calibration mode by adding a phase-locked loop control center (PLL Control Center).

[0098] In some embodiments, the frequency detector 306 monitors the reference signal F REF and the low frequency signal F DIV The frequency and phase differences between the output UP signal and the DN signal control the charge pump 307.

[0099] In some embodiments, the charge pump 307 outputs the UP signal and the DN signal according to the frequency detector 306, and outputs the current I CP So that according to the current I CP , to charge and discharge the next-stage loop filter 308; wherein the current I CP Includes: pull-up current or pull-down current.

[0100] In some embodiments, the loop filter 308 is used to generate a current when the charge pump 307 outputs a current I CP When the control voltage Vtune is generated by LF, the output frequency of the LC / LI oscillator 303 is controlled in the phase-locked loop closed-loop operation mode.

[0101] In some embodiments, see Figure 5 , is a circuit diagram of a capacitor-inductor oscillator provided in this embodiment. Figure 5 In the embodiment, the capacitor-inductor oscillator 303 includes: a power supply (Voltage Drain Drain, VDD), an inductor L0, variable capacitors Cv1 and Cv2 controlled by an input voltage port Vin, a capacitor array (Cap Array), a group of cross-coupled active metal oxide semiconductor (MOS) tubes M1 and M2, a tail current source I0 and a ground connection (Voltage Source Supply, VSS).

[0102] In some embodiments, the feedback divider 309 is used to divide the high frequency signal F output by the capacitor and inductor oscillator 303. VCO Perform frequency division and output low-frequency signal F after frequency division DIV , the low-frequency signal F fed back after the phase-locked loop is locked DIV With reference signal F REF frequency and phase are consistent.

[0103] In some embodiments, the counter 301 includes: an A counter (Counter A) and a B counter (Counter B), which respectively detect the reference signal F REF The low frequency signal F output by the feedback divider DIV Count a period of time and calculate the value according to the reference signal F REF and the low frequency signal F DIV Count the results and obtain the frequency difference.

[0104] In some embodiments, the automatic frequency calibration offline control module 302, when the switchable switch SW connects the input voltage port Vin and the open-loop calibration reference input voltage Vref, the phase-locked loop is in the open-loop working mode, and the automatic frequency calibration offline control module 302 determines the output working frequency F of the capacitor-inductor oscillator 303 according to the counting results of the A counter and the B counter. VCO When the frequency is higher or lower than the target operating frequency of the phase-locked loop, the automatic frequency calibration offline control module 302 adjusts the capacitor array Cap Array of the capacitor-inductor oscillator 303 to obtain the optimal capacitance according to the open-loop automatic frequency calibration algorithm, and the digital control signal of the capacitor array Cap Array is the optimal offline calibration value.

[0105] In some embodiments, for a phase-locked loop supporting wideband operation, the capacitor array Cap Array usually has a large number of capacitors. Using an open-loop automatic frequency calibration method can accelerate obtaining the optimal capacitance value with the help of algorithms such as binary search, thereby improving the speed of automatic frequency calibration.

[0106] In some embodiments, the comparator 310 includes two comparators, namely CMP1 and CMP2. CMP1 is used to compare the control voltage Vtune with the preset voltage upper limit V H CMP2 is used to compare the control voltage Vtune with the preset voltage lower limit V L The size relationship.

[0107] In some embodiments, the automatic frequency calibration online control module 304 is used to monitor the locking state of the phase-locked loop online when the switchable switch SW connects the input voltage port Vin to the open-loop calibration reference input voltage Vref, and the phase-locked loop is in a closed-loop working mode: when the comparator determines that V L ≤Vtune≤V H When Vtune <V L or Vtune>V H After a period of time, it is determined that the phase-locked loop is in an unlocked state. When the automatic frequency calibration online control module 304 adjusts the capacitor array Cap Array of the capacitor-inductor oscillator 303 to obtain the optimal capacitance according to the closed-loop automatic frequency calibration algorithm, the digital control signal of the capacitor array CapArray is the optimal offline calibration value.

[0108] It is worth noting that when the operating frequency of the phase-locked loop does not change, but the operating environment of the phase-locked loop (such as the operating temperature) changes, resulting in the situation that the capacitance size of the originally selected capacitor array Cap Array is inappropriate, generally the capacitor array Cap Array can be switched to an adjacent frequency band. The closed-loop automatic frequency calibration method can be used to quickly switch to the adjacent frequency band through capacitor addition and subtraction, thereby reducing the fluctuation of the output operating frequency of the capacitor-inductor oscillator 303.

[0109] For specific application scenarios, the phase-locked loop operating frequency may not change much (such as a few MHz or tens of MHz). When switching the phase-locked loop operating frequency, the capacitor array Cap Array of the capacitor-inductor oscillator 303 does not need to be adjusted much. Selecting the closed-loop automatic frequency calibration method may also obtain a faster automatic frequency calibration speed.

[0110] In some embodiments, the phase-locked loop control center 305 is used to configure a suitable division ratio for the feedback divider 309 according to the input phase-locked loop operating frequency, control the SW to make the phase-locked loop enter an open-loop operating mode or a closed-loop operating mode, intelligently select automatic frequency calibration in offline mode or online mode, etc.

[0111] The circuit provided in this embodiment combines closed-loop automatic frequency calibration and open-loop automatic calibration. When the chip is initially working or the operating frequency is adjusted greatly, an open-loop automatic calibration method with a faster full-band search is adopted; when the chip operating frequency is adjusted slightly or the lock is lost only due to changes in the application environment, a closed-loop automatic calibration method with a faster adjacent frequency band search and stable switching is adopted. Through the intelligent scheduling of the phase-locked loop control center, the phase-locked loop adaptively selects the best automatic frequency calibration method to obtain the fastest locking speed in different usage environments, thereby improving the calibration efficiency and accuracy of the chip, adapting to different application scenarios, and further improving the applicability of the phase-locked loop calibration.

[0112] Those skilled in the art will appreciate that the embodiments of the present application may also provide computer program products. Therefore, the present application may adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application may adopt the form of computer program products implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program codes.

[0113] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (apparatus), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0114] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0115] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0116] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.< / n>

Claims

1. A phase-locked loop automatic frequency calibration method, characterized in that: The phase-locked loop comprises: a capacitor-inductor oscillator; the phase-locked loop automatic frequency calibration method comprises: After the phase-locked loop is turned on, the operating frequency of the phase-locked loop is configured, and the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter the open-loop calibration mode to obtain the output high-frequency signal; According to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, an open-loop calibration is performed on the capacitor array of the capacitor-inductor oscillator, and then a closed-loop calibration mode is entered; Real-time monitoring of whether the operating frequency of the phase-locked loop changes, if the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop enters a closed-loop operating mode; If the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in an unlocked state, performing a closed-loop online calibration on the capacitor array; If the phase loop operating frequency changes, and the change value from the original phase-locked loop operating frequency exceeds a preset threshold, the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter an open-loop calibration mode; If the phase loop operating frequency changes and the change value does not exceed the preset threshold, the capacitor-inductor oscillator is connected to the control voltage to enter the closed-loop calibration mode; the preset threshold is a reference frequency value obtained by comparing the locking time of the closed-loop calibration mode with that of the open-loop calibration mode.

2. The phase-locked loop automatic frequency calibration method according to claim 1, characterized in that: The method of performing an open-loop calibration on the capacitor array of the capacitor-inductor oscillator according to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, and then entering a closed-loop calibration mode, comprises: According to the frequency difference between the low-frequency signal corresponding to the high-frequency signal and the reference signal corresponding to the low-frequency signal, an open-loop calibration is performed on the capacitor array of the capacitor-inductor oscillator to obtain an optimal offline calibration value, the capacitor-inductor oscillator is connected to a control voltage to enter a closed-loop calibration mode, and in the closed-loop calibration mode, the optimal offline calibration value is maintained.

3. The phase-locked loop automatic frequency calibration method according to claim 2, characterized in that: Obtaining a frequency difference between the high frequency signal and a low frequency signal corresponding to the high frequency signal includes: The high frequency signal is divided to obtain a low frequency signal, and the count of the low frequency signal and a reference signal corresponding to the low frequency signal in a period is obtained, and the difference between the count result of the low frequency signal and the count result of the low frequency signal is taken as the frequency difference.

4. The phase-locked loop automatic frequency calibration method as claimed in claim 3, characterized in that: The open-loop calibration of the capacitor array of the capacitor-inductor oscillator to obtain an optimal offline calibration value includes: According to the frequency difference, a plurality of digital control signals in the capacitor array of the capacitor-inductor oscillator and the variable capacitance of the capacitor-inductor oscillator are adjusted respectively to obtain an optimal offline calibration value of the capacitor array.

5. The phase-locked loop automatic frequency calibration method as claimed in claim 4, characterized in that: The phase-locked loop is in a locked state, including: if the control voltage is monitored in real time within the preset voltage upper and lower limits, the phase-locked loop is in a locked state; otherwise, the phase-locked loop is in an unlocked state; wherein the closed-loop online calibration of the capacitor array includes: The capacitor array is calibrated online in a closed loop according to the control voltage monitored in real time, and the optimal offline calibration value is re-acquired. The capacitor inductor oscillator is connected to the control voltage to make the phase-locked loop enter the closed-loop working mode, and the phase-locked loop working frequency and locking state are monitored in real time again.

6. A phase-locked loop automatic frequency calibration device, characterized in that: The phase-locked loop includes: a capacitor-inductor oscillator; the phase-locked loop automatic frequency calibration device includes: an open-loop calibration unit, a closed-loop calibration unit, a real-time monitoring unit and an online calibration unit; wherein, The open-loop calibration unit is used to configure the operating frequency of the phase-locked loop after the phase-locked loop is turned on, and connect the capacitor-inductor oscillator to the open-loop calibration reference input voltage to enter the open-loop calibration mode to obtain the output high-frequency signal; A closed-loop calibration unit, configured to perform an open-loop calibration on the capacitor array of the capacitor-inductor oscillator according to a frequency difference between a low-frequency signal corresponding to the high-frequency signal and a reference signal corresponding to the low-frequency signal, and then enter a closed-loop calibration mode; The real-time monitoring unit is used to monitor in real time whether the operating frequency of the phase-locked loop changes. If the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop enters a closed-loop operating mode; The online calibration unit is used to perform closed-loop online calibration on the capacitor array if the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in an unlocked state; if the operating frequency of the phase-locked loop changes and the change value compared with the original phase-locked loop operating frequency exceeds a preset threshold, the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter an open-loop calibration mode; if the operating frequency of the phase-locked loop changes and the change value does not exceed the preset threshold, the capacitor-inductor oscillator is connected to the control voltage to enter a closed-loop calibration mode; the preset threshold is a reference frequency value obtained by comparing the locking time of the closed-loop calibration mode with that of the open-loop calibration mode.

7. A phase-locked loop automatic frequency calibration circuit, characterized in that: include: Counter, automatic frequency calibration offline control module, capacitor inductor oscillator, automatic frequency calibration online control module and phase-locked loop control center; wherein, The phase-locked loop control center is used to configure the phase-locked loop operating frequency after the phase-locked loop is turned on; The capacitor-inductor oscillator is used to access an open-loop calibration reference input voltage or a control voltage through a switchable switch. If the switchable switch is connected to the open-loop calibration reference input voltage, it enters an open-loop calibration mode through connection with the automatic frequency calibration offline control module and outputs a high-frequency signal; The counter is used to obtain a frequency difference between the low-frequency signal corresponding to the high-frequency signal and a reference signal corresponding to the low-frequency signal; The automatic frequency calibration offline control module is used to perform open-loop calibration on the capacitor array of the capacitor-inductor oscillator according to the frequency difference; The automatic frequency calibration online control module is used to switch the switchable switch from the open-loop calibration reference input voltage to the control voltage to enter a closed-loop calibration mode; The phase-locked loop control center is also used to monitor in real time whether the operating frequency of the phase-locked loop changes. If the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in a locked state, the phase-locked loop is kept working and the automatic frequency calibration online control module is controlled to monitor the locking state in real time; if the operating frequency of the phase-locked loop remains unchanged and the phase-locked loop is in an unlocked state, the automatic frequency calibration online control module is controlled to perform closed-loop online calibration on the capacitor array; if the phase-locked loop operating frequency changes and the change value from the original phase-locked loop operating frequency exceeds a preset threshold, the capacitor-inductor oscillator is connected to the open-loop calibration reference input voltage to enter an open-loop calibration mode; if the phase-loop operating frequency changes and the change value does not exceed the preset threshold, the capacitor-inductor oscillator is connected to the control voltage to enter a closed-loop calibration mode; the preset threshold is a reference frequency value obtained by comparing the locking time of the closed-loop calibration mode with that of the open-loop calibration mode.

8. The phase-locked loop automatic frequency calibration circuit as claimed in claim 7, characterized in that: The capacitor array includes: multiple groups of control switches connected in parallel, and two groups of capacitors controlled by each group of control switches; wherein, the multiple control switches in the capacitor array and the variable capacitor of the capacitor-inductor oscillator are adjusted respectively, so that the capacitor-inductor oscillator outputs high-frequency signals with different operating frequencies.

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