Temperature compensation method for temperature compensated crystal oscillator and crystal oscillator

Abstract

The application belongs to the technical field of crystal oscillator design, and particularly discloses a temperature compensation method of a temperature-compensated crystal oscillator and the crystal oscillator. The temperature compensation method comprises the following steps: measuring a working temperature signal of a crystal resonator in the temperature-compensated crystal oscillator; generating a frequency control signal according to the working temperature signal and a pre-determined target nominal frequency temperature curve, and controlling the oscillation frequency of the crystal resonator by using the frequency control signal; wherein the target nominal frequency temperature curve is obtained by adding a linear compensation line segment to an initial nominal frequency temperature curve of the crystal resonator for linear compensation, and the initial nominal frequency temperature curve is obtained by compensating the frequency deviation of the crystal resonator by a polynomial compensation function generator. The application solves the problem that the compensation accuracy of temperature compensation in the related art is still low.

Description

Technical Field

[0001] This invention belongs to the field of crystal oscillator design technology, specifically relating to a temperature compensation method for a temperature-compensated crystal oscillator and a crystal oscillator. Background Technology

[0002] Quartz crystal is an anisotropic crystal. Utilizing the piezoelectric effect of quartz crystal, crystal oscillators that provide stable frequency signals can be designed. However, crystal oscillators made from ordinary AT-cut quartz crystals exhibit frequency variations of tens of ppm when the ambient temperature changes. To achieve higher frequency temperature stability, temperature compensation is required.

[0003] According to the resonance model of a crystal resonator, connecting a reactor in series with the crystal resonator will cause a shift in the crystal's resonant frequency. If a variable reactor is used, and the change in reactance with temperature is opposite to the frequency shift, the frequency shift can be reduced, and the temperature coefficient can be significantly improved. Therefore, a varactor diode can be connected in series in the crystal resonator branch, and its reactance can be adjusted according to temperature changes to regulate the oscillation frequency. The equation obtained by adding the compensation voltage on the varactor diode to the frequency-temperature characteristic equation of the quartz resonator is as follows:

[0004]

[0005] In the formula, T – arbitrary temperature, unit °C; T0 – reference temperature, unit °C; f – oscillation frequency, unit Hz; f0 – reference frequency, unit Hz; a0 – first-order temperature coefficient at reference temperature T0, unit 1 / ℃; b0 – second-order temperature coefficient at reference temperature T0, unit 1 / ℃²; c0 – third-order temperature coefficient at reference temperature T0, unit 1 / ℃³; a – dynamic temperature coefficient, a = 10⁻⁵ s / ℃; KV – voltage control coefficient of the varactor tube, unit Hz / V; UK – control voltage applied across the varactor tube.

[0006] Existing technology integrates a function generator into the temperature-compensated crystal oscillator (TCXO) IC to compensate for the frequency-temperature offset of the crystal itself. Specifically, by changing the value of the function generator's register, the coefficients of each term in the function generator are altered, generating a frequency compensation curve that complements the resonator's frequency-temperature characteristics. This yields the nominal frequency-temperature curve, automatically generating a corresponding control voltage to control the varactor diode inside the crystal oscillator, changing the crystal's load capacitance and adjusting the crystal oscillator's frequency to achieve temperature compensation. Thus, when the temperature changes, the frequency can be compensated according to the nominal frequency-temperature curve, adjusting the crystal oscillator frequency to achieve stable output. The frequency-temperature stability of the crystal oscillator after this temperature compensation is generally controlled within ±1ppm in the temperature range of -40℃ to +85℃. However, for applications with higher environmental requirements, the compensation accuracy of this method is still relatively low, and further improvements in crystal oscillator compensation are urgently needed. Summary of the Invention

[0007] The purpose of this invention is to provide a temperature compensation method and a crystal oscillator for a temperature-compensated crystal oscillator, so as to solve the problem that the compensation accuracy of temperature compensation is still low in related technologies.

[0008] To achieve the above objectives, in a first aspect of the present invention, a temperature compensation method for a temperature-compensated crystal oscillator is provided, wherein the temperature-compensated crystal oscillator integrates a polynomial compensation function generator, and the method includes:

[0009] Measure the operating temperature signal of the crystal resonator in a temperature-compensated crystal oscillator;

[0010] Based on the operating temperature signal and the predetermined target nominal frequency temperature curve, a frequency control signal is generated, and the oscillation frequency of the crystal resonator is controlled by the frequency control signal; wherein, the target nominal frequency temperature curve is obtained by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator for linear compensation, and the initial nominal frequency temperature curve is obtained by the polynomial compensation function generator to compensate for the frequency offset of the crystal resonator.

[0011] Furthermore, the step of obtaining the target nominal frequency temperature curve by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator for linear compensation includes:

[0012] The initial nominal frequency temperature curve is divided into multiple frequency temperature curve segments according to a preset temperature range. Within the corresponding temperature range, a linear compensation line segment is added to each frequency temperature curve segment. The changing trend of the linear compensation line segment is opposite to the changing trend of the frequency temperature curve segment. By using each of the linear compensation line segments, the corresponding frequency temperature curve segment is linearly compensated to obtain the target nominal frequency temperature curve.

[0013] Furthermore, the constituent parameters of the linear compensation segment include:

[0014] Zero bias temperature, which is the temperature value selected from the temperature values ​​within the temperature range when the frequency compensation of the initial nominal frequency temperature curve is zero.

[0015] The slope of the line segment is the slope obtained according to a preset slope value range.

[0016] Furthermore, the constituent parameters of the linear compensation segment include:

[0017] Zero bias temperature, which is a temperature value selected from multiple temperature values ​​within the corresponding temperature segment when the frequency compensation of the preset linear compensation line segment to the initial nominal frequency temperature curve is zero.

[0018] The slope of the line segment is a slope obtained according to a preset range of slope values;

[0019] Therefore, before performing linear compensation on the corresponding frequency-temperature curve segments using each of the linear compensation line segments, the method further includes:

[0020] For each of the linear compensation segments, the zero bias temperature and the slope of the segment are adjusted according to the selected temperature value and the range of the slope value of the segment to obtain multiple pre-selected linear compensation segments;

[0021] A target linear compensation segment is selected from the multiple pre-selected linear compensation segments, and the target linear compensation segment is used to perform linear compensation on the corresponding frequency-temperature curve segment.

[0022] Further, the step of adjusting the zero-bias temperature and the slope of the line segment to obtain multiple pre-selected linear compensation line segments based on the selected temperature value and the slope range of the line segment includes:

[0023] When different temperature values ​​are selected at the zero bias temperature, different slope values ​​are selected from the slope value range as the slope of the line segment to obtain multiple pre-selected linear compensation line segments.

[0024] In a second aspect, the present invention provides a temperature-compensated crystal oscillator, wherein the temperature-compensated crystal oscillator employs a temperature compensation method for temperature compensation, and the temperature-compensated crystal oscillator comprises:

[0025] The control chip includes a polynomial compensation function generator;

[0026] A crystal resonator, which is electrically connected to the control chip;

[0027] The control chip is used to measure the operating temperature signal of the crystal resonator and to control the polynomial compensation function generator to generate a frequency control signal based on the operating temperature signal and a predetermined target nominal frequency temperature curve. The frequency control signal is then used to control the oscillation frequency of the crystal resonator. The target nominal frequency temperature curve is obtained by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator for linear compensation. The initial nominal frequency temperature curve is obtained by the polynomial compensation function generator to compensate for the frequency offset of the crystal resonator.

[0028] Furthermore, the control chip also includes:

[0029] Temperature sensor, used to measure the operating temperature signal of the crystal resonator in a temperature-compensated crystal oscillator;

[0030] An oscillation control module is provided, with one end electrically connected to the polynomial compensation function generator and the other end electrically connected to the crystal resonator.

[0031] Furthermore, the oscillation control module includes:

[0032] A variable container, one end of which is electrically connected to the polynomial compensation function generator;

[0033] An oscillation circuit is electrically connected between the variable capacitor and the crystal resonator.

[0034] Furthermore, the polynomial compensation function generator includes:

[0035] A temperature coefficient compensation unit is electrically connected to the output terminal of the temperature sensor.

[0036] A linear compensation unit, which is electrically connected to the output terminal of the temperature sensor;

[0037] An adder, the input of which is electrically connected to the output of the temperature coefficient compensation unit and the output of the linear compensation unit, and the output of which is electrically connected to the oscillation control module.

[0038] Furthermore, the control chip also includes:

[0039] A shaping frequency divider circuit is electrically connected to the oscillation control module.

[0040] Compared with the prior art, the technical solution provided in this application has at least the following technical effects:

[0041] The temperature compensation method proposed in this invention optimizes the temperature compensation effect in the prior art, and can achieve a frequency temperature stability of better than ±0.28ppm in the range of -40℃ to +85℃, which meets the ever-increasing demand of electronic devices for miniaturization and high precision of temperature-compensated crystal oscillators. Attached Figure Description

[0042] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0043] Figure 1 A temperature compensation method for a temperature-compensated crystal oscillator is provided in one embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the circuit structure of a temperature-compensated crystal oscillator provided in an embodiment of the present invention;

[0045] Figure 3 A schematic diagram illustrating the principle of frequency compensation provided in an embodiment of the present invention;

[0046] Figure 4 A schematic diagram of the test process for five temperature coefficient curve compensation provided in an embodiment of the present invention;

[0047] Figure 5 This is a schematic diagram illustrating the influence of changes in the values ​​of several registers on the frequency-temperature curve, as provided in an embodiment of the present invention.

[0048] Figure 6 This is a schematic diagram illustrating the influence of the value change of the FIFTH register on the frequency-temperature curve according to an embodiment of the present invention.

[0049] Figure 7 This is a schematic diagram illustrating the typical effects of different values ​​of zero bias temperature and line segment slope on the frequency curve, as provided in an embodiment of the present invention.

[0050] Figure 8 This is a schematic diagram of linear compensation provided in an embodiment of the present invention.

[0051] Explanation of reference numerals in the attached figures:

[0052] 10. Temperature-compensated crystal oscillator; 11. Control chip; 111. Temperature sensor; 112. Polynomial compensation function generator; 121. Temperature coefficient compensation unit; 122. Linear compensation unit; 123. Adder; 113. Varactor diode; 114. Oscillation circuit; 115. Shaping and frequency division circuit; 12. Crystal resonator. Detailed Implementation

[0053] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and are not to a precise scale, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0054] It should be noted that, in order to clearly illustrate the content of this invention, several embodiments are provided to further explain different implementations of the invention. These embodiments are enumerated rather than exhaustive. Furthermore, for the sake of brevity, content mentioned in the preceding embodiments is often omitted in the following embodiments. Therefore, content not mentioned in the later embodiments can be referred to in the preceding embodiments.

[0055] Please see Figure 1 The first embodiment of the present invention provides a temperature compensation method for a temperature-compensated crystal oscillator 10. The temperature-compensated crystal oscillator 10 integrates a polynomial compensation function generator 112. The temperature compensation method provided by the embodiment of the present invention includes the following steps:

[0056] Step S11: Measure the operating temperature signal of the crystal resonator 12 in the temperature-compensated crystal oscillator 10.

[0057] Step S12: Based on the operating temperature signal and the predetermined target nominal frequency temperature curve, a frequency control signal is generated, and the oscillation frequency of the crystal resonator 12 is controlled by the frequency control signal. The target nominal frequency temperature curve is obtained by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator 12 for linear compensation. The initial nominal frequency temperature curve is obtained by the polynomial compensation function generator 112 to compensate for the frequency offset of the crystal resonator 12.

[0058] The polynomial compensation function generator 112 includes registers such as FIFTH, FOUR, CUB, INF, and LIN. By changing the values ​​of each register, the coefficients of each term in the polynomial compensation function generator 112 are controlled, generating an initial nominal frequency-temperature curve (i.e., a curve complementary to the frequency-temperature characteristics of the crystal resonator 12) that is also compatible with the frequency-temperature characteristics of the crystal resonator 12. Figure 3The compensated frequency curve (in the figure) achieves the effect of temperature compensation. With this compensation method, the frequency temperature stability of the crystal oscillator can generally be controlled within ±1ppm in the temperature range of -40℃ to +85℃. However, in the embodiment of the present invention, in addition to temperature compensation of the crystal resonator 12 based on the initial nominal frequency temperature curve, corresponding linear compensation is also performed on the crystal resonator 12. As a result, the frequency temperature stability of the crystal oscillator in the temperature range of -40℃ to +85℃ can be reduced from ±1ppm to ±0.1ppm to ±0.2ppm, which significantly improves the compensation level of the temperature-compensated crystal oscillator 10.

[0059] In one embodiment of the present invention, the step of obtaining the target nominal frequency temperature curve by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator 12 includes: dividing the initial nominal frequency temperature curve into multiple frequency temperature curve segments according to a preset temperature range, and adding a linear compensation segment (e.g., ...) to each frequency temperature curve segment within the corresponding temperature range. Figure 8 As shown in the broken line segments (the trend of the linear compensation line segments is opposite to that of the frequency-temperature curve segments), each linear compensation line segment is used to perform linear compensation on the corresponding frequency-temperature curve segments. Based on the compensation influence of each linear compensation line segment on the corresponding frequency-temperature curve segment, each linear compensation line segment is superimposed on the initial nominal frequency-temperature curve to obtain the target nominal frequency-temperature curve. When performing linear compensation on the initial nominal frequency-temperature curve segments, the initial nominal frequency-temperature curve can be divided into 8 temperature segments within the range of -40℃ to +85℃. A first-order linear compensation amount EVA0 to EVA7 is added to each temperature segment, as shown in Table 1.

[0060] EVA0 -40℃～-35℃ EVA1 -35℃～-20℃ EVA2 -15℃～0℃ EVA3 5℃～20℃ EVA4 25℃～40℃ EVA5 45℃～60℃ EVA6 65℃～80℃ EVA7 80℃～85℃

[0061] Table 1 shows the temperature range for each temperature segment during piecewise linear compensation.

[0062] The parameters for each linear compensation segment include two parameters: zero bias temperature and segment slope (both of which are set by the corresponding linear compensator integrated in the polynomial compensation function generator 112). The zero bias temperature is the temperature value selected from the temperature values ​​within the temperature range when the frequency compensation of the initial nominal frequency temperature curve is zero. In actual engineering, due to the configuration conditions of the linear compensator related storage devices in the linear compensation unit 122, the zero bias temperature can only be selected as an integer temperature value within each temperature range. For example, for the temperature range of -15℃ to 0℃ for the compensation amount EVA2, the zero bias temperature can be selected as integer values ​​such as -15℃, -10℃, -5℃, and 0℃. The slope of the line segment is the slope obtained according to a preset slope value range. For example, for the temperature range of -15℃ to 0℃ for the compensation amount EVA2, the slope of the line segment can be selected in steps from -0.08 to +0.08 with preset step values. For example, when the step value is 0.01, the slope of the line segment can be selected from -0.08, -0.07, -0.06, -0.05 to +0.08. The typical effects of different slope values ​​on the frequency curve are as follows: Figure 7 As shown.

[0063] Before performing linear compensation on the corresponding frequency-temperature curve segment using each linear compensation line segment, this embodiment of the invention adjusts the zero-bias temperature and the line segment slope for each linear compensation line segment based on the selected temperature value and the slope range of the line segment to obtain multiple pre-selected linear compensation line segments (e.g., ...). Figure 7Different pre-selected linear compensation segments are obtained under different zero bias temperatures and line slopes (as shown). Then, the target linear compensation segment is selected from multiple pre-selected linear compensation segments, thereby selecting the target linear compensation segment with the best compensation effect. The linear compensation segment with the best compensation effect is the one that minimizes the frequency temperature stability ppm value of the temperature-compensated crystal oscillator 10 when the ambient temperature changes. The target linear compensation segment is then used to perform linear compensation on the corresponding frequency temperature curve segment. The steps for obtaining multiple pre-selected linear compensation segments by adjusting the zero-bias temperature and the slope of the line segment based on the selected temperature value and the range of slope values ​​include: selecting different slope values ​​from the slope range as the line segment slopes when choosing different zero-bias temperatures to obtain multiple pre-selected linear compensation segments. For example, when the zero-bias temperature is a specific value, the line segment slope can be selected sequentially in steps from -0.08 to +0.08 with preset step values. For instance, when the zero-bias temperature is -15℃ and the line segment slope is selected as -0.07, one linear compensation segment is obtained; when the line segment slope becomes -0.06, another linear compensation segment is obtained, and so on, to obtain multiple different pre-selected linear compensation segments. From these, the zero-bias temperature and line segment slope with better compensation accuracy for the corresponding frequency temperature curve segment are selected. By using appropriate parameters, the target linear compensation line segment with the best compensation effect for each curve segment of the initial nominal frequency temperature curve is obtained. Each target linear compensation line segment obtained from the test is superimposed on each frequency temperature curve segment of the initial nominal frequency temperature curve, so that the compensation of the frequency temperature curve segment under each temperature range is more accurate and achieves a higher compensation effect. When the crystal oscillator is working, the polynomial compensation function generator 112 can select appropriate parameters for the linear compensation line segment through the corresponding linear compensator, and compensate for the frequency deviation of the crystal resonator 12 at the current operating temperature of the temperature-compensated crystal oscillator 10. It can also reduce the frequency temperature stability of the crystal oscillator from ±1ppm to ±0.1ppm to ±0.2ppm in the temperature range of -40℃ to +85℃, which greatly improves the compensation level of the temperature-compensated crystal oscillator.

[0064] In a second embodiment of the present invention, a temperature-compensated crystal oscillator 10 is provided. The temperature-compensated crystal oscillator 10 uses the temperature compensation method provided in the first embodiment for temperature compensation. The temperature-compensated crystal oscillator 10 includes a control chip 11 and a crystal resonator 12. The control chip 11 includes a polynomial compensation function generator 112. The crystal resonator 12 is electrically connected to the control chip 11.

[0065] The control chip 11 is used to measure the operating temperature signal of the crystal resonator 12 and to control the polynomial compensation function generator 112 to generate a frequency control signal based on the operating temperature signal and a predetermined target nominal frequency temperature curve. The frequency control signal is used to control the oscillation frequency of the crystal resonator 12. The target nominal frequency temperature curve is obtained by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator 12 for linear compensation. The initial nominal frequency temperature curve is obtained by the polynomial compensation function generator 112 to compensate for the frequency deviation of the crystal resonator 12.

[0066] The control chip 11 also includes a temperature sensor 111 and an oscillation control module. The temperature sensor 111 is used to measure the operating temperature signal of the crystal resonator 12 in the temperature-compensated crystal oscillator 10, and then inputs the operating temperature signal into the polynomial compensation function generator 112. The oscillation control module includes a varactor diode and an oscillation circuit 114. In this embodiment, the varactor diode is a varactor diode 113. One end of the varactor diode 113 is electrically connected to the polynomial compensation function generator 112, and the other end is electrically connected to the oscillation circuit 114. The oscillation circuit 114 is electrically connected between the varactor diode 113 and the crystal resonator 12, and is used to make the crystal resonator 12 generate an oscillation signal.

[0067] The polynomial compensation function generator 112 includes a temperature coefficient compensation unit 121, a linear compensation unit 122, and an adder 123. The temperature coefficient compensation unit 121 is electrically connected to the output terminal of the temperature sensor 111. Since the frequency-temperature curves of different crystal resonators 12 vary significantly, the temperature coefficient compensation unit 121 includes registers such as FIFTH, FOUR, CUB, INF, and LIN to accommodate different crystal resonators 12. During the stage of determining the initial nominal frequency-temperature curve, the temperature coefficient compensation unit 121 adjusts the values ​​of each register. The coefficients of each term in the numerically controlled polynomial compensation function generator 112 generate an initial nominal frequency-temperature curve that complements the original frequency-temperature characteristics of the crystal resonator 12, and obtain the compensation parameters of each register. Thus, during the actual operation of the temperature-compensated crystal oscillator 10, based on the initial nominal frequency-temperature curve, the coefficients of each term in the polynomial compensation function generator 112 are changed through the compensation parameters of each register to generate a control voltage to change the capacitance of the varactor diode 113, thereby changing the load capacitance of the crystal resonator 12, pulling the frequency of the crystal oscillator, and achieving the effect of temperature compensation.

[0068] The linear compensation unit 122 is electrically connected to the output terminal of the temperature sensor 111. The linear compensation unit 122 is used to provide the structural parameters of the linear compensation segment within the corresponding temperature range during the determination stage of the target nominal frequency temperature curve and the actual working stage of the temperature-compensated crystal oscillator 10, and outputs a compensation signal according to the structural parameters. The linear compensation unit 122 contains multiple linear compensators. According to Table 1, this invention provides eight linear compensators corresponding to the multiple linear compensation values ​​(EVA0 to EVA7). Figure 2 In the linear compensator N, N is a positive integer (N equals seven when there are eight linear compensators). Each linear compensator generates a corresponding compensation signal based on the required linear compensation segment for each temperature range. (Each linear compensator only outputs a compensation signal within the pre-set operating temperature range. For example, if the current operating ambient temperature is within the temperature range of the compensation amount EVA2, only linear compensator 3 outputs a voltage signal, while the outputs of other linear compensators are zero. At the same time, the registers in the temperature coefficient compensation unit 121 output voltage signals normally.) Thus, while the temperature coefficient compensation unit 121 performs temperature compensation, it further compensates for the frequency offset of the crystal resonator 12. The input terminal of adder 123 is electrically connected to the output terminal of temperature coefficient compensation unit 121 and the output terminal of linear compensation unit 122. The output terminal of adder 123 is electrically connected to the oscillation control module. Adder 123 outputs the voltage signals used for compensation processing from temperature coefficient compensation unit 121 and linear compensation unit 122. Therefore, in this embodiment of the invention, the temperature sensor 111 receives the temperature signal, and based on the target nominal frequency temperature curve of the crystal resonator 12, the frequency offset of the crystal resonator 12 is further linearly compensated by a linear compensator by changing the coefficients of each term of the polynomial compensation function generator 112 through a register, thereby generating a corresponding control voltage (i.e., a frequency control signal), changing the capacitance of the varactor diode 113, and thus changing the load capacitance of the crystal resonator 12, thereby increasing the output frequency of the crystal oscillator. Furthermore, the control chip 11 also includes a shaping and frequency divider circuit 115, which is electrically connected to the oscillation circuit 114 and is used to adjust the amplitude of the oscillation signal output by the temperature-compensated crystal oscillator.

[0069] In this embodiment of the invention, the principle by which the polynomial compensation function generator 112 compensates for the frequency shift of the crystal resonator 12 is as follows: Figure 8As shown in the figure, the uncompensated frequency curve is the original uncompensated frequency curve of the crystal resonator 12, the dashed line is the compensated frequency curve, and the compensated frequency curve is the initial nominal frequency temperature curve. When the temperature changes and the oscillation frequency of the crystal oscillator changes, the trend of the compensated frequency change is opposite to the trend of the crystal oscillator's oscillation frequency change, thus pulling the crystal oscillator's oscillation frequency to change in the opposite direction. When both temperature and frequency compensation are applied to the crystal oscillator simultaneously, and the two effects on the crystal oscillator's oscillation frequency are roughly equal, the crystal oscillator's oscillation frequency is stabilized at the nominal frequency. Once the law of frequency compensation changing with temperature is determined, frequency compensation can be performed when the temperature changes, adjusting the crystal oscillator frequency to achieve stable output. In this embodiment, the initial nominal frequency temperature curve is obtained by testing the temperature-compensated crystal oscillator 10 as follows:

[0070] Temperature compensation parameter analysis process as follows Figure 4 As shown, first set the temperature of the chamber. After the temperature stabilizes, set the initial value of each register and test the frequency corresponding to the initial register. Then change the value of each register in turn. After each register is changed, test the corresponding frequency. When changing the next register, restore the value of the previously changed register to the initial value. Collect the corresponding frequency values ​​at more than ten temperature points throughout the temperature range and record the frequency output of the crystal oscillator after changing each register.

[0071] During compensation testing, if each register is increased by 20 and decreased by 20 respectively, and the frequency-temperature curve corresponding to the temperature-compensated crystal oscillator 10 is measured, then subtracting each curve from the curve corresponding to the initial register value will yield the effect of each register change on the frequency-temperature curve. Figure 5 and Figure 6As shown, in the curves corresponding to each register, one line represents the effect of increasing the register by 20, and the other line represents the effect of decreasing the register by 20. For example, in the graph of the influence of the frequency-temperature curve of the LIN register, -LIN represents the effect of increasing the LIN register by 20, and +LIN represents the effect of decreasing the LIN register by 20. If increasing the current value of the LIN register by 20 from the original curve is still insufficient, the system will continuously increase the value of the LIN register until the first term of the temperature curve is canceled out. The value of the LIN register obtained at this point is taken as the optimal value of that register. Similarly, if increasing the current value of the INF register by 20 from the original curve is still insufficient, the system will continuously increase the value of the INF register until the second term of the temperature curve is canceled out, and so on. By changing the value of the CUB register, the third term of the original temperature curve of the crystal resonator 12 is canceled out; by changing the FOUR register, the fourth term of the original temperature curve is canceled out; and by changing the FIFTH register, the fifth term of the original temperature curve is canceled out. Finally, the compensation parameters of the five registers are obtained. Then, based on the original curve of the temperature-compensated crystal oscillator, the parameters are obtained through fitting calculations (such as fitting the influence of the frequency-temperature curve of each register using the least squares method). Figure 3 or Figure 8 The dashed line represents the compensated frequency curve. By superimposing the compensated frequency curve and the uncompensated frequency curve according to the ratio controlled by the register value, the initial nominal frequency temperature curve that satisfies frequency temperature stability can be obtained (i.e., Figure 3 and Figure 8 (Frequency curve after compensation).

[0072] Based on the initial nominal frequency temperature curve obtained from the above five temperature curve compensations, the frequency temperature stability of the crystal oscillator can generally be controlled within ±1 ppm in the temperature range of -40℃ to +85℃. Figure 8 The frequency curve after compensation is shown in the figure.

[0073] To further optimize the frequency temperature stability of the temperature-compensated crystal oscillator, this embodiment of the invention performs tests every 5°C across the entire temperature range to obtain a complete initial nominal frequency temperature curve. The temperature curve is divided into 8 temperature segments within the range of -40°C to +85°C, and a linear compensation variable EVA0 to EVA7 is added to each temperature segment.

[0074] Each compensation value is a compensation line segment containing two parameters: zero bias temperature (the temperature corresponding to zero compensation for the initial nominal frequency temperature curve) and slope. Taking EVA2 as an example, for test conditions within the range of -15℃ to 0℃, by changing the zero bias temperature and slope parameters, the zero bias temperature can be selected from -15℃, -10℃, -5℃, and 0℃, and the slope can be selected from -0.08 to +0.08 in 0.01 steps. The typical effects of different values ​​on the frequency curve are as follows. Figure 7 As shown. Based on the test results of the first step of compensation, select appropriate parameters for the zero bias temperature and slope (e.g., Figure 8 As shown in the broken line segment in the figure, the compensation curve is superimposed on the compensated frequency curve, making the compensation for each temperature range more accurate, thereby achieving a higher compensation effect. The frequency temperature stability of the crystal oscillator can be reduced from ±1ppm to ±0.1ppm to ±0.2ppm in the temperature range of -40℃ to +85℃, which greatly improves the compensation level of the temperature-compensated crystal oscillator.

[0075] Therefore, the temperature compensation method proposed in this embodiment of the invention optimizes the temperature compensation effect in the prior art, and can achieve a frequency temperature stability of better than ±0.28ppm in the range of -40℃ to +85℃, which meets the ever-increasing demand of electronic devices for miniaturization and high precision of temperature-compensated crystal oscillators 10.

[0076] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0077] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0078] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A temperature compensation method for a temperature compensated crystal oscillator, characterized by, The temperature-compensated crystal oscillator (10) integrates a polynomial compensation function generator (112), and the method includes: Measure the operating temperature signal of the crystal resonator (12) in the temperature-compensated crystal oscillator (10); Based on the operating temperature signal and the predetermined target nominal frequency temperature curve, a frequency control signal is generated, and the oscillation frequency of the crystal resonator (12) is controlled by the frequency control signal; wherein, the target nominal frequency temperature curve is obtained by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator (12) for linear compensation, and the initial nominal frequency temperature curve is obtained by the polynomial compensation function generator (112) to compensate for the frequency offset of the crystal resonator (12); The step of obtaining the target nominal frequency temperature curve by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator (12) for linear compensation includes: The initial nominal frequency temperature curve is divided into multiple frequency temperature curve segments according to a preset temperature range. Within the corresponding temperature range, a linear compensation line segment is added to each frequency temperature curve segment. The changing trend of the linear compensation line segment is opposite to the changing trend of the frequency temperature curve segment. By using each of the linear compensation line segments, the corresponding frequency temperature curve segment is linearly compensated to obtain the target nominal frequency temperature curve.

2. The temperature compensation method of a temperature compensated crystal oscillator according to claim 1, wherein, The parameters constituting the linear compensation segment include: Zero bias temperature, which is the temperature value selected from the temperature values ​​within the temperature range when the frequency compensation of the initial nominal frequency temperature curve is zero. The slope of the line segment is the slope obtained according to a preset slope value range.

3. The temperature compensation method of a temperature compensated crystal oscillator according to claim 1, wherein, The parameters constituting the linear compensation segment include: Zero bias temperature, which is a temperature value selected from multiple temperature values ​​within the corresponding temperature segment when the frequency compensation of the preset linear compensation line segment to the initial nominal frequency temperature curve is zero. The slope of the line segment is a slope obtained according to a preset range of slope values; Therefore, before performing linear compensation on the corresponding frequency-temperature curve segments using each of the linear compensation line segments, the method further includes: For each of the linear compensation segments, the zero bias temperature and the slope of the segment are adjusted according to the selected temperature value and the range of the slope value of the segment to obtain multiple pre-selected linear compensation segments; A target linear compensation segment is selected from the multiple pre-selected linear compensation segments, and the target linear compensation segment is used to perform linear compensation on the corresponding frequency-temperature curve segment.

4. The temperature compensation method for a temperature-compensated crystal oscillator as described in claim 3, characterized in that, The step of adjusting the zero-bias temperature and the slope of the line segment to obtain multiple pre-selected linear compensation line segments based on the selected temperature value and the slope range of the line segment includes: When different temperature values ​​are selected at the zero bias temperature, different slope values ​​are selected from the slope value range as the slope of the line segment to obtain multiple pre-selected linear compensation line segments.

5. A temperature-compensated crystal oscillator, characterized in that, The temperature-compensated crystal oscillator (10) uses the temperature compensation method of the temperature-compensated crystal oscillator (10) according to any one of claims 1 to 4 to perform temperature compensation. The temperature-compensated crystal oscillator (10) includes: a control chip (11), and the control chip (11) includes a polynomial compensation function generator (112). A crystal resonator (12) is electrically connected to the control chip (11); The control chip (11) is used to measure the operating temperature signal of the crystal resonator (12) and control the polynomial compensation function generator (112) to generate a frequency control signal based on the operating temperature signal and a predetermined target nominal frequency temperature curve, and to control the oscillation frequency of the crystal resonator (12) using the frequency control signal. The target nominal frequency temperature curve is obtained by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator (12) for linear compensation. The initial nominal frequency temperature curve is obtained by the polynomial compensation function generator (112) to compensate for the frequency offset of the crystal resonator (12). The step of obtaining the target nominal frequency temperature curve by adding a linear compensation segment to the initial nominal frequency temperature curve of the crystal resonator (12) for linear compensation includes: The initial nominal frequency temperature curve is divided into multiple frequency temperature curve segments according to a preset temperature range. Within the corresponding temperature range, a linear compensation line segment is added to each frequency temperature curve segment. The changing trend of the linear compensation line segment is opposite to the changing trend of the frequency temperature curve segment. By using each of the linear compensation line segments, the corresponding frequency temperature curve segment is linearly compensated to obtain the target nominal frequency temperature curve.

6. The temperature-compensated crystal oscillator (10) as described in claim 5, characterized in that, The control chip (11) also includes a temperature sensor (111) for measuring the operating temperature signal of the crystal resonator (12) in the temperature-compensated crystal oscillator (10); An oscillation control module is provided, with one end electrically connected to the polynomial compensation function generator (112) and the other end electrically connected to the crystal resonator (12).

7. The temperature-compensated crystal oscillator (10) as described in claim 6, characterized in that, The oscillation control module includes: A variable container, one end of which is electrically connected to the polynomial compensation function generator (112); An oscillation circuit (114) is electrically connected between the variable capacitor and the crystal resonator (12).

8. The temperature-compensated crystal oscillator (10) as described in claim 6, characterized in that, The polynomial compensation function generator (112) includes: Temperature coefficient compensation unit (121), wherein the temperature coefficient compensation unit (121) is electrically connected to the output terminal of the temperature sensor (111); A linear compensation unit (122) is electrically connected to the output terminal of the temperature sensor (111); Adder (123), the input terminal of the adder (123) is electrically connected to the output terminal of the temperature coefficient compensation unit (121) and the output terminal of the linear compensation unit (122), and the output terminal of the adder (123) is electrically connected to the oscillation control module.

9. The temperature-compensated crystal oscillator (10) as described in claim 6, characterized in that, The control chip (11) further includes a shaping frequency divider circuit (115), which is electrically connected to the oscillation control module.

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