Calibration method of temperature compensated crystal oscillator, control chip and calibration system

Abstract

This invention provides a calibration method, control chip, and calibration system for a temperature-compensated crystal oscillator. The method includes: setting multiple calibration temperature values ​​and initial values ​​for multi-order coefficients; acquiring the initial frequency of the temperature-compensated crystal oscillator at different temperatures, comparing the initial frequency with a benchmark oscillation frequency to determine an initial deviation ε; changing the values ​​of each order calibration coefficient to acquire the output frequency at different temperatures, and comparing the output frequency with the initial frequency to determine the unit change J of each order coefficient. ni The elements of the correlation matrix J are used to determine the calibration error relationship. The calibration error relationship is constructed based on the correlation matrix J, the initial deviation ε, the correction amounts ΔB for each order of coefficients to be solved, and the residual deviation Ø after calibration. The optimal correction amounts ΔB for each order of calibration coefficients are obtained by minimizing the range of the residual deviation Ø, i.e., the difference between the maximum and minimum values. This invention can effectively improve the calibration accuracy of TCXO.

Description

Technical Field

[0001] This invention relates to the field of crystal oscillator technology, and in particular to a calibration method, control chip and calibration system for a temperature-compensated crystal oscillator. Background Technology

[0002] Temperature-compensated crystal oscillators (TCXOs) are oscillators that maintain high-precision frequency output over a wide temperature range and are widely used in communications, navigation, and measurement. As electronic devices increasingly demand higher frequency stability, the temperature compensation accuracy of TCXOs has become a key technical indicator.

[0003] Existing TCXO temperature compensation methods typically involve iterating through the changes in the frequency effect of each order coefficient under various temperature conditions, testing the ideal voltage value at the target frequency, changing the settings of each order coefficient register to align the output voltage with the ideal voltage parameters, and then back-calculating the correction values ​​of each order coefficient register. This process involves numerous calibration steps, long calculation times, high calibration difficulty and cost, and insufficient compensation accuracy. Summary of the Invention

[0004] This invention provides a calibration method, control chip, and calibration system for a temperature-compensated crystal oscillator to solve the technical problem of insufficient calibration accuracy in traditional calibration methods.

[0005] This invention provides a calibration method for a temperature-compensated crystal oscillator. The method includes: setting multiple calibration temperature values ​​and initial values ​​for multi-order coefficients; obtaining the initial frequency of the temperature-compensated crystal oscillator at different temperatures based on the temperature values ​​and the initial values, and comparing the initial frequency with a benchmark oscillation frequency to determine an initial deviation ε; changing the values ​​of each order coefficient to obtain the output frequency at different temperatures, and comparing the output frequency with the initial frequency to determine the unit change J of each order coefficient corresponding to the output frequency. ni According to the unit change J ni Construct an correlation matrix J, wherein the correlation matrix J is used to characterize the unit change J of frequency at different temperatures. ni The mapping relationship between the coefficient corrections ΔB and the coefficients of each order is established; the calibration error relationship is constructed based on the correlation matrix J, the initial deviation ε, the coefficient corrections ΔB of each order, and the residual deviation Ø after calibration; optimization is performed with the goal of minimizing the range of the residual deviation Ø to obtain the optimal coefficient corrections ΔB of each order, and the temperature-compensated crystal oscillator is calibrated based on the optimal coefficient corrections ΔB of each order.

[0006] In one embodiment of the present invention, the correlation matrix J is n An m-order matrix; where n is the number of temperatures and m is the order of the coefficients, and the elements in the correlation matrix J are used to characterize the degree of influence of the adjustment amount of each order coefficient on the frequency change at the corresponding temperature.

[0007] In one embodiment of the present invention, the residual deviation Ø is the result of the combined effect of the initial deviation ε, the correlation matrix J, and the correction amounts ΔB of each order of coefficients.

[0008] The present invention also provides a control chip for performing the calibration method of the temperature-compensated crystal oscillator described above, the control chip comprising:

[0009] Multiple coefficient registers are used to store and adjust coefficients of various orders; Temperature sensor is used to scan the temperature of the chip and convert different temperatures into corresponding voltage signals, which are then provided to the power product term generation circuit corresponding to the coefficient components of the frequency adjustment function. An adder is used to sum the components of the frequency adjustment function. The gain unit provides gain to the voltage output by the adder, and the output voltage signal is applied to the frequency adjustment element of the oscillator to adjust the frequency.

[0010] The present invention also provides a calibration system, comprising: a control chip; a temperature-compensated crystal oscillator calibration chip, which acquires voltage values ​​corresponding to different temperatures through an internal temperature sensor, and is used to generate power product terms of each order component of the frequency adjustment function; registers corresponding to each order coefficient are used to adjust the magnitude of each order coefficient component of the function; an adder is used to sum the coefficient components of each order, and the output of the adder is applied to the frequency adjustment element of the oscillator in the form of voltage through a gain unit to achieve frequency adjustment.

[0011] In one embodiment of the present invention, the temperature-compensated crystal oscillator calibration chip is further used to perform optimization with the goal of minimizing the range of the residual deviation Ø, to obtain the optimal coefficient correction amount ΔB for each order, and to adjust the corresponding coefficient register using the optimal coefficient correction amount ΔB to achieve full-temperature calibration of the temperature-compensated crystal oscillator.

[0012] The beneficial effects of this invention: This invention proposes a calibration method, control chip, and calibration system for a temperature-compensated crystal oscillator. By constructing a core correlation matrix J, which characterizes the unit frequency change J at different temperatures... niThe mapping relationship between the coefficients and their corresponding correction values ​​ΔB is established. The elements of the matrix reflect the influence of each coefficient's adjustment on the frequency change at the corresponding temperature. A calibration error relationship is constructed, consisting of the initial deviation ε before calibration, the aforementioned correlation matrix J, the correction values ​​ΔB for each coefficient, and the residual deviation Ø. By setting the objective as minimizing the range of the residual deviation Ø, and solving under the constraint of the coefficient's value range, the appropriate coefficient correction value is obtained. This invention provides a practical method for the testing, analysis, and batch calibration of TCXO chips. The algorithm is adaptable to various TCXO calibration chips, allowing for the arbitrary setting of multiple temperature points for data acquisition. Frequency is used as the adjustment target, eliminating concerns about the voltage output and measurement accuracy at the test temperature points, and the process discreteness of chip-related parameters. This simplifies the operation process and shortens calibration time. Attached Figure Description

[0013] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0014] In the attached diagram: Figure 1 This is a schematic diagram of a temperature-compensated crystal oscillator in one embodiment of the present invention; Figure 2 This is a schematic diagram of the control chip structure in one embodiment of the present invention; Figure 3 This is a schematic flowchart of a calibration method for a temperature-compensated crystal oscillator according to an embodiment of the present invention; Figure 4 This is a schematic diagram of temperature compensation for a temperature-compensated crystal oscillator in one embodiment of the present invention. Detailed Implementation

[0015] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0016] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0017] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0018] Please see Figure 1 , Figure 1 This is a schematic diagram of a temperature-compensated crystal oscillator according to one embodiment of the present invention. The control chip in the temperature-compensated crystal oscillator is typically an ASIC, which is the core control element. It monitors the ambient temperature in real time through a built-in temperature sensor and generates a reverse voltage signal based on a pre-stored polynomial algorithm or digital compensation model to compensate for temperature drift in the crystal frequency. Under normal circumstances, the calibration of the temperature-compensated crystal oscillator needs to satisfy the following formula: (Formula 1) in, ~A These represent the coefficients for the 5th to 0th order components, T0 is the initial temperature setting, T is the actual temperature, and the deviation of the actual frequency from the ideal frequency is also represented. The unit is ppm.

[0019] Please see Figure 2 , Figure 2 This is a schematic diagram of the control chip structure in one embodiment of the present invention. The control chip may include multiple coefficient-related registers. The internal temperature sensor chip of the temperature-compensated crystal oscillator control chip converts the temperature into a voltage signal and provides the voltage signal to the frequency adjustment function's power product term generation circuit. Then, the summation of the coefficient components of each order is achieved through an adder, and a functional relationship similar to Equation 1 is constructed. For example, it includes a TO register and B0~B5 registers. The B5~B0 registers of the control chip can set the magnitude of each order coefficient, and the T0 register can adjust the function's offset with respect to temperature T.

[0020] Please see Figure 3 , Figure 3This is a schematic flowchart illustrating a calibration method for a temperature-compensated crystal oscillator according to an embodiment of the present invention. In this embodiment, a calibration method for a temperature-compensated crystal oscillator is provided. This method improves the frequency stability of the temperature-compensated crystal oscillator under different temperature environments by optimizing the coefficients of each order component. The calibration method for the temperature-compensated crystal oscillator includes the following steps: Step S300: Set multiple calibration temperature values ​​and initial values ​​for multi-order coefficients.

[0021] Before calibration begins, multiple temperature values ​​need to be set as reference temperature points based on the characteristics of the crystal oscillator. A fixed temperature offset is set in the TO register to ensure the symmetry of the frequency adjustment values ​​in high and low temperature environments (not included in the algorithm). At the same time, the values ​​of each order coefficient are set as initial values ​​in the B0~B5 registers.

[0022] Step S310: Obtain the initial frequency of the temperature-compensated crystal oscillator at different temperatures based on the temperature value and the initial value, and compare the initial frequency with the benchmark oscillation frequency to determine the initial deviation ε.

[0023] Set an appropriate T0 value and place the temperature-compensated crystal oscillator in a temperature-controlled environment. Sequentially set different ambient temperatures, such as multiple temperature points between -40℃ and 85℃. After the temperature stabilizes at each point, measure and record the oscillator's output frequency. Determine the initial deviation ε by comparing it with a benchmark oscillation frequency using a function constructed based on the aforementioned control chip and a structure similar to Equation 1. The initial deviation ε is expressed as a relative frequency deviation (ppm).

[0024] Step S320: Change the values ​​of each order coefficient to obtain the output frequency at different temperatures, and compare the output frequency with the initial frequency to determine the unit change J of each order calibration coefficient corresponding to the output frequency. ni .

[0025] To calibrate frequency accuracy across the entire temperature range, under n ambient temperatures T1~Tn, the corresponding... ~B The register adjusts the magnitude of each coefficient component and obtains the output frequency at different temperatures. It compares this output frequency with the initial frequency to determine the unit change in each coefficient.

[0026] Under n different temperature conditions, including ~B Register values ​​and corresponding frequencies The n function expressions are shown in Equation 2.

[0027] (Formula 2) Step S330, based on the unit change Jni Construct an correlation matrix J, wherein the correlation matrix J is used to characterize the unit change J of frequency at different temperatures. ni The mapping relationship between the coefficients and the correction amount ΔB of each order.

[0028] The correlation matrix J is an n×m matrix, where n is the number of temperature measurement points and m is the order of the coefficients. Each element in the correlation matrix J characterizes the degree of influence of the adjustment amount of each order coefficient on the frequency change at the corresponding temperature. The elements of the correlation matrix J are shown in Equation 3.

[0029] (Formula 3) Step S340: Construct a calibration error relationship based on the correlation matrix J, the initial deviation ε, the correction amount ΔB of each order calibration coefficient, and the residual deviation Ø after calibration; perform optimization with the goal of minimizing the range of the residual deviation Ø to obtain the optimal correction amount ΔB of each order coefficient, and calibrate the temperature-compensated crystal oscillator based on the optimal correction amount ΔB of each order coefficient.

[0030] Please see Figure 4 , Figure 4 This is a schematic diagram of temperature compensation for a temperature-compensated crystal oscillator in one embodiment of the present invention. Constrained least squares, gradient descent, or genetic algorithms are used as specific methods for solving the nonlinear programming problem, with the optimization objective being to minimize the range of the residual deviation Ø, to solve for the optimal correction amount ΔB for each order of coefficients.

[0031] By superimposing the correction amounts ΔB of each order coefficient, and continuously observing the range of the residual deviation Ø, the correction amount ΔB corresponding to the minimum range of the residual deviation Ø is found through iterative calculation, which is the optimal correction amount ΔB of each order coefficient.

[0032] The optimal correction values ​​ΔB for each order coefficient were written into the corresponding coefficient registers of the temperature-compensated crystal oscillator. By changing the ambient temperature and repeatedly measuring the calibration effect, the frequency deviation of the calibrated temperature-compensated crystal oscillator was significantly smaller than that before calibration over the entire operating temperature range, and the frequency-temperature curve was flatter, indicating that the calibration method effectively improved the temperature stability of the oscillator.

[0033] In this embodiment, a control chip is provided to perform a temperature-compensated crystal oscillator calibration method. This control chip provides the hardware conditions for implementing the temperature-compensated crystal oscillator calibration method.

[0034] The control chip includes multiple registers, a temperature sensor, an adder, and a gain unit.

[0035] Multiple coefficient registers are used to store and adjust coefficients of various orders. These coefficient registers are readable and writable storage units that can save and update relevant parameters during the calibration process. As shown in Equation 1, the temperature offset value T0 stored in the coefficient registers realizes the translation of the function curve on the temperature coordinate axis, and the amplitude values ​​of each order calibration coefficient are used to adjust the amplitude of A5~A0.

[0036] The variable T in Equation 1, representing the temperature sensor, is used to scan the temperatures of different control chips and convert these temperatures into corresponding voltage signals. These signals are then used to generate the power product terms of the coefficients of the frequency adjustment function. The temperature sensor can accurately detect changes in ambient temperature and output a voltage signal proportional to the temperature. These voltage signals are then superimposed with an offset T0 and transmitted to an adder circuit to generate the control voltage required for temperature compensation.

[0037] An adder is used to sum the coefficients of a function. The adder receives circuit signals from the product of the coefficients and the power of temperature, performs the addition operation, and obtains the voltage value corresponding to the frequency compensation at the current temperature.

[0038] The gain unit provides a certain gain to the voltage output of the adder, and the output voltage signal is applied to the frequency adjustment element of the oscillator to achieve frequency adjustment.

[0039] This control chip, through the aforementioned structure, implements the calibration method for the temperature-compensated crystal oscillator described in Example 1, effectively improving the frequency stability of the crystal oscillator under different temperature environments. The control chip integrates data storage, temperature detection, and frequency adjustment functions, making the calibration process more efficient and accurate.

[0040] In this embodiment, a calibration system is provided, which includes the aforementioned control chip and temperature-compensated crystal oscillator calibration chip.

[0041] Regarding the control chip, the calibration system employs the aforementioned control chip, which includes multiple coefficient registers, a temperature sensor, an adder, and a gain unit. The multiple coefficient registers store and adjust the magnitudes of coefficients of each order; the temperature sensor scans the chip's temperature and converts different temperatures into corresponding voltage signals, which are then provided to the power product term generation circuits corresponding to each order coefficient component; the adder sums the frequency coefficient components; and the gain unit provides gain to the voltage output from the adder, and the output voltage signal is applied to the oscillator's frequency adjustment element to adjust the frequency.

[0042] The calibration system includes high and low temperature environment detectors, a host computer and a slave computer, and testing instruments. The host computer runs calibration software to control the testing instruments and read frequency values, and the slave computer reads and writes to the chip. Simultaneously, the host computer software synchronously controls the high and low temperature environments, obtains the initial frequency error and the unit change of the corresponding coefficients at different temperatures, constructs a mathematical model of the calibration error relationship, and uses programming to obtain the optimal correction amount for each coefficient. The output of the internal temperature sensor of the temperature-compensated crystal oscillator control chip generates the product term of the power of each coefficient component; the registers corresponding to each coefficient are used to set the magnitude of the coefficients; the adder is used to sum the coefficient components; the output of the adder is applied as a voltage to the frequency adjustment element of the oscillator through the gain unit to achieve frequency adjustment.

[0043] The optimal correction values ​​for each order coefficient are obtained by planning and solving. These optimal correction values ​​are then written into the registers of the control chip. Through internal temperature sensors, adders, and frequency adjustment components, the calibrated temperature-compensated crystal oscillator can automatically adjust its output frequency under different temperature conditions, thereby achieving high-precision frequency stability.

[0044] This calibration system significantly improves the frequency stability of the oscillator over a wide temperature range, making it suitable for various electronic devices and communication systems that require a high-precision clock source.

[0045] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method of calibrating a temperature compensated crystal oscillator, characterized by, The method includes: Set multiple calibration temperature values ​​and initial values ​​for multi-order coefficients; The initial frequency of the temperature-compensated crystal oscillator at different temperatures is obtained based on the temperature value and the initial value, and the initial frequency is compared with the benchmark oscillation frequency to determine the initial deviation ε. By changing the values ​​of each order coefficient, the output frequency at different temperatures is obtained, and the output frequency is compared with the initial frequency to determine the unit change J of each order coefficient corresponding to the output frequency. ni ; According to the unit variation J ni A correlation matrix J is constructed, wherein the correlation matrix J is used to represent the unit variation J of frequency at different temperatures ni The mapping relationship between the correction amount ΔB of each order coefficient The calibration error relationship is constructed based on the correlation matrix J, the initial deviation ε, the correction amount ΔB of each order coefficient, and the residual deviation Ø after calibration; optimization is performed with the goal of minimizing the range of the residual deviation Ø to obtain the optimal correction amount ΔB of each order coefficient, and the temperature-compensated crystal oscillator is calibrated based on the optimal correction amount ΔB of each order coefficient.

2. The calibration method for a temperature-compensated transistor oscillator according to claim 1, characterized in that, The correlation matrix J is n An m-order matrix; where n is the number of temperatures and m is the order of the coefficients, and the elements in the correlation matrix J are used to characterize the degree of influence of the adjustment amount of each order coefficient on the frequency change at the corresponding temperature.

3. The calibration method for a temperature-compensated transistor oscillator according to claim 1, characterized in that, The residual deviation Ø is the result of the combined effect of the initial deviation ε, the correlation matrix J, and the correction amount △B of each order coefficient.

4. A control chip for performing a calibration method for a temperature-compensated crystal oscillator as described in any one of claims 1-3, characterized in that, The control chip includes: Multiple coefficient registers are used to store and adjust coefficients of various orders; Temperature sensor is used to scan the temperature of the chip and convert different temperatures into corresponding voltage signals, which are then provided to the power product term generation circuit corresponding to the coefficient components of the frequency adjustment function. An adder is used to sum the components of the frequency adjustment function. The gain unit provides gain to the voltage output by the adder, and the output voltage signal is applied to the frequency adjustment element of the oscillator to adjust the frequency.

5. A calibration system, characterized in that, include: The control chip as described in claim 4; The temperature-compensated crystal oscillator calibration chip obtains voltage values ​​corresponding to different temperatures through an internal temperature sensor, which are used to generate the power product terms of each order component of the frequency adjustment function; the registers corresponding to each order coefficient are used to adjust the magnitude of each order coefficient component of the function; the adder is used to sum the coefficient components of each order, and the output of the adder is applied to the frequency adjustment element of the oscillator in the form of voltage through the gain unit to achieve frequency adjustment.

6. The calibration system according to claim 5, characterized in that, The temperature-compensated crystal oscillator calibration chip is also used to optimize the range of the residual deviation Ø to obtain the optimal correction amount ΔB for each order of coefficients. The corresponding coefficient register is adjusted using the optimal correction amount ΔB to achieve full-temperature calibration of the temperature-compensated crystal oscillator.

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