High-order temperature compensation clock based on MEMS resonator and working method thereof

Abstract

The invention provides a high-order temperature compensation clock based on an MEMS resonator and a working method of the high-order temperature compensation clock. The high-order temperature compensation clock comprises an MEMS resonator, an oscillation maintaining circuit and a temperature compensation circuit. The temperature compensation circuit is connected with the oscillation maintaining circuit and provides temperature compensation voltage opposite to the temperature characteristic of the MEMS resonator for the oscillation maintaining circuit, and the temperature compensation voltage serves as control voltage of the oscillation maintaining circuit. And the oscillation maintaining circuit and the MEMS resonator are connected and work together to generate a stable periodic oscillation signal so as to output a clock signal subjected to temperature compensation. According to the invention, the compensation is realized by generating the compensation voltage based on the temperature characteristic of the MEMS resonator, and the temperature stability of the clock frequency is improved.

Description

Technical Field

[0001] The present invention relates to the field of circuit technology, and in particular to a high-order temperature compensation clock based on a MEMS resonator and a working method thereof. Background Art

[0002] With the rapid development of modern communications, computers, consumer electronics and other fields, higher and higher requirements are placed on the stability and accuracy of frequency sources. Although traditional quartz crystal-based clocks can meet these requirements to a certain extent, their large size, high cost, and difficulty in integration limit their application in modern electronic devices. Compared with traditional quartz oscillators, MEMS oscillators have the following significant advantages: easy integration, low cost, high frequency, and resistance to vibration and shock.

[0003] Although MEMS resonators have many advantages, their temperature characteristics are a disadvantage that cannot be ignored. Similar to quartz crystal oscillators, the oscillation frequency of MEMS resonators will also drift due to the influence of ambient temperature. This temperature drift will cause the accuracy and stability of the clock signal to decrease, thus affecting the performance of the entire electronic system.

[0004] In summary, the study of high-order temperature compensated clock design based on MEMS resonators has important practical significance and application value. By overcoming the disadvantages of its temperature characteristics, the advantages of MEMS resonators can be fully utilized to provide strong support for the development of modern communications, computers, consumer electronics and other fields. Summary of the invention

[0005] The purpose of the present invention is to propose a high-order temperature compensated clock based on a MEMS resonator and a working method thereof, which utilizes a CMOS temperature compensation circuit based on a MEMS resonator to achieve compensation by generating a compensation voltage based on the temperature characteristics of the MEMS resonator while meeting the requirements of low phase noise and small volume, thereby improving the temperature stability of the clock frequency.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] In the first aspect, the present invention provides a high-order temperature compensated clock based on a MEMS resonator; the high-order temperature compensated clock includes a MEMS resonator, an oscillation maintaining circuit, and a temperature compensation circuit; the temperature compensation circuit is connected to the oscillation maintaining circuit and provides the oscillation maintaining circuit with a temperature compensation voltage opposite to the temperature characteristics of the MEMS resonator as a control voltage of the oscillation maintaining circuit; the oscillation maintaining circuit is connected to the MEMS resonator and works together to generate a stable periodic oscillation signal to output a temperature compensated clock signal.

[0008] Preferably, the oscillation maintaining circuit is a voltage-controlled oscillator whose control voltage varies with temperature.

[0009] Preferably, the temperature compensation circuit includes a reference voltage module, a high-order compensation voltage module, a coefficient buffer stage, and a summing module connected in sequence; the reference voltage module generates a primary voltage related to temperature, the high-order compensation voltage module generates a high-order compensation voltage related to temperature based on the input primary voltage related to temperature, the coefficient buffer stage is used to scale the input power voltages of each level, and the summing module sums the scaled power voltages of each level to obtain the temperature compensation voltage.

[0010] Preferably, the reference voltage module is specifically a bandgap reference voltage source.

[0011] Preferably, the high-order compensation voltage module generates the high-order compensation voltage through a cascaded analog multiplier.

[0012] Preferably, the analog multiplier of the high-order compensation voltage module adopts a Gilbert structure.

[0013] Preferably, the summing module is implemented by a summing circuit.

[0014] In a second aspect, the present invention provides a working method of a high-order temperature compensation clock based on a MEMS resonator; the details are as follows:

[0015] The reference voltage module generates a negative temperature coefficient voltage V that is negatively correlated with temperature. CTAT and reference voltage V REF ;

[0016] The negative temperature coefficient voltage V CTAT and reference voltage V REF Sent to the high-order compensation voltage module, the high-order compensation voltage γ (V CTAT -V REF ) 2 , γ 2 (V CTAT -V REF ) 3 …γ n-1 (V CTAT -V REF ) n , γ is the scaling factor of the analog multiplier;

[0017] The primary voltage output by the reference voltage generation module and the high-order compensation voltage output by the high-order compensation voltage module form the power voltages of each level and send them to the coefficient buffer stage for scaling. The power voltages of each level after scaling are a1(V CTAT -V REF ), a2γ(V CTAT -VREF ) 2 , a3γ 2 (V CTAT -V REF ) 3 ……a n γ n-1 (V CTAT -V REF ) n , where a1, a2, a3, ... a n is the scaling factor;

[0018] The scaled voltages of each level are sent to the summing module for summing to obtain the temperature compensation voltage V C :

[0019] V C =b0+b1(V CTAT -V REF )+b2(V CTAT -V REF ) 2 +......+b n (V CTAT -V REF ) n

[0020] Where b0 is the calibration voltage and b0 = a0V REF , a0 is the calibration coefficient, b1, b2, b3...b n is the product of the scaling factor and the multiplier ratio factor, and b n =a n γ n-1 .

[0021] Preferably, the coefficients b1, b2, ... b of the temperature compensation voltage are n The settings satisfy Where k is V CTAT Correlation coefficient with temperature, d1, d2, ... d n are the coefficients of the MEMS resonator temperature characteristics c1, c2, ... c n Zoom Out - K VCO The compensation voltage coefficient is obtained by multiplying the voltage by d1, that is, d1 = -c1 / K VCO d2=-c2 / K VCO ……d n =-c n / K VCO .

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention proposes a high-order temperature compensation clock based on a MEMS resonator and an implementation method thereof, which realizes compensation by generating a compensation voltage based on the temperature characteristics of the MEMS resonator, thereby improving the temperature stability of the clock frequency. An analog temperature compensation circuit is used to generate a compensation voltage with a trend opposite to the temperature characteristics of the MEMS resonator to compensate for the temperature drift of the MEMS resonator. The overall circuit is mainly divided into two parts: an oscillation maintenance circuit and a temperature compensation circuit, wherein the oscillation maintenance circuit includes a GM unit and a variable capacitor, and the temperature compensation circuit includes a bandgap reference voltage source, a voltage generation circuit, a coefficient buffer stage, and a summing circuit. The circuit generates a high-order compensation voltage related to temperature, which offsets the high-order terms of the temperature characteristics of the MEMS resonator, thereby improving the temperature stability of the clock frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the working principle of a high-order temperature compensation clock based on a MEMS resonator according to the present invention;

[0025] Figure 2 It is a schematic diagram of the structure of the temperature compensation circuit of the present invention. DETAILED DESCRIPTION

[0026] The following is combined with Figure 1-2 , the technical solution of the present invention is specifically described.

[0027] The present invention proposes a high-order temperature compensated clock based on a MEMS resonator; the clock comprises a MEMS resonator, an oscillation maintaining circuit, and a temperature compensation circuit; the oscillation maintaining circuit works together with the MEMS resonator to generate a stable periodic oscillation signal; the temperature compensation circuit provides a compensation voltage opposite to the temperature characteristic of the MEMS resonator to the oscillation maintaining circuit; the temperature compensation circuit is connected to the oscillation maintaining circuit and outputs a temperature-compensated clock signal.

[0028] The oscillation maintaining circuit is a voltage controlled oscillator whose control voltage varies with temperature.

[0029] The temperature compensation circuit includes a reference voltage module, a high-order compensation voltage module, a coefficient buffer stage, and a summing module which are connected in sequence; the reference voltage module generates a primary voltage related to temperature, the high-order compensation voltage module generates a high-order compensation voltage related to temperature according to the input primary voltage related to temperature, the coefficient buffer stage is used to scale the input power voltages of each level, and the summing module sums the scaled power voltages of each level to obtain the temperature compensation voltage.

[0030] The reference voltage module is specifically a bandgap reference voltage source.

[0031] The high-order compensation voltage module generates a high-order compensation voltage through a cascaded analog multiplier.

[0032] The analog multiplier of the high-order compensation voltage module adopts a Gilbert structure.

[0033] The summing module is implemented by a summing circuit.

[0034] A working method of a high-order temperature compensation clock based on a MEMS resonator, wherein the temperature compensation circuit is used to provide a temperature compensation voltage to an oscillation maintenance circuit. The reference voltage module generates a negative temperature coefficient voltage V CTAT and reference voltage V REF , then the negative temperature coefficient voltage V CTAT and reference voltage V REF The analog multiplier is connected to the cascade to obtain the high-order compensation voltage. The analog multiplier adopts the classic Gilbert structure. The two sets of primary differential voltage (V CTAT -V REF ) is sent to the first multiplier to obtain a set of secondary differential output signals γ(V CTAT -V REF ) 2 ; Then this set of quadratic difference output signals γ(V CTAT -V REF ) 2 With a set of first square differential signals (V CTAT -V REF ) is sent to the second multiplier for multiplication to obtain a set of cubic difference output signals γ 2 (V CTAT -V REF ) 3 ; When n is an odd number, a group of n-order differential output signals can be obtained by sending a group of (n-1) / 2-order differential voltages and a group of (n+1) / 2-order differential voltages to an analog multiplier; when n is an even number, a group of n-order differential output signals can be obtained by sending two groups of n / 2-order differential voltages to an analog multiplier; the linear signal and the differential signal are scaled by the coefficient buffer stage, and then the scaled power signals of each level are summed to generate a temperature compensation voltage.

[0035] The high-order coefficients of the compensation voltage are obtained by scaling the high-order coefficients of the temperature characteristics of the MEMS resonator.

[0036] The relationship between the resonant frequency f of the MEMS resonator and the temperature T is:

[0037] f(T)=c1(T-T0)+c2(T-T0) 2 +c3(T-T0) 3 +……+c n (T-T0) n +f0 formula 1;

[0038] where c1, c2, c3, ... cn is a constant, T0 is the reference temperature, and f0 is the frequency component that has nothing to do with temperature;

[0039] The relationship between the temperature compensation voltage and temperature is:

[0040] V C (T) = d0 + d1 (T - T0) + d2 (T - T0) 2 +d3(T-T0) 3 +……+d n (T-T0) n Formula 2:

[0041] where d0, d1, d2, d3, ... n is the compensation voltage coefficient;

[0042] The oscillation frequency f of the oscillation maintaining circuit VCO With control voltage V C The relationship is:

[0043] f VCO (V C )=V C K VCO +f1 formula three;

[0044] Where f1 is the frequency component that has nothing to do with the control voltage, K VCO is the slope of the oscillation frequency versus the control voltage:

[0045]

[0046] Where L m , C m and C p They are the motional inductance, motional capacitance and plate capacitance of the MBVD model of the MEMS resonator, C v Is with V C Positively correlated variable capacitance;

[0047] The oscillation frequency f of the oscillation maintaining circuit VCO With control voltage V C The relationship with temperature T is:

[0048] f VCO (V C ,T)=V C K VCO +c1(T-T0)+c2(T-T0) 2 +……+c n (T-T0) n +f3 formula five;

[0049] Where f3 is the frequency component that is independent of temperature and control voltage;

[0050] The compensation voltage coefficient of the compensation voltage satisfies the temperature characteristics of the MEMS resonator and the coefficients of each level are reduced by -K VCO times, that is, d1=-c1 / K VCO d2=-c2 / K VCO ……d n =-c n / K VCO When the oscillation frequency output is stable,

[0051] The reference voltage module generates a negative temperature coefficient voltage V that is negatively correlated with temperature. CTAT and reference voltage V REF , then the negative temperature coefficient voltage V CTAT and reference voltage V REF Sent to the cascaded analog multiplier to obtain the high-order compensation voltage γ (V CTAT -V REF ) 2 , γ 2 (V CTAT -V REF ) 3 …γ n-1 (V CTAT -V REF ) n , where γ is the scaling factor of the analog multiplier;

[0052] The temperature is negatively correlated with the negative temperature coefficient voltage V CTAT The relationship with temperature T is:

[0053] V CTAT =kT+V0 Formula 6;

[0054] Substituting formula 6 into formula 2 yields:

[0056] Formula 7;

[0057] Where k is V CTAT The correlation coefficient with temperature represents V CTAT Relationship with temperature;

[0058] The primary voltage output by the reference voltage generation module and the high-order compensation voltage output by the analog multiplier are sent to the coefficient buffer stage for scaling. The scaled high-order compensation voltage is b2 (V CTAT -V REF ) 2 b3(V CTAT -V REF ) 3 ……b n (V CTAT -VREF ) n ;

[0059] The temperature compensation voltage can be obtained by sending the scaled voltage of each level to the summing circuit for summing, which is expressed as:

[0060] V C =b0+b1(V CTAT -V REF )+b2(V CTAT -V REF ) 2 +……+b n (V CTAT -V REF ) n Formula 8;

[0061] Formula 8 can be transformed into Formula 9:

[0062]

[0063] Comparing Formula 7 and Formula 9, the compensation voltage coefficient of the compensation voltage satisfies Formula 10:

[0064]

[0065] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A high-order temperature compensated clock based on a MEMS resonator, characterized in that: The high-order temperature compensated clock includes a MEMS resonator, an oscillation maintaining circuit, and a temperature compensation circuit; the temperature compensation circuit is connected to the oscillation maintaining circuit and provides the oscillation maintaining circuit with a temperature compensation voltage opposite to the temperature characteristics of the MEMS resonator as a control voltage of the oscillation maintaining circuit; the oscillation maintaining circuit is connected to the MEMS resonator and works together to generate a stable periodic oscillation signal to output a temperature-compensated clock signal.

2. A high-order temperature compensated clock based on a MEMS resonator according to claim 1, characterized in that: The oscillation maintaining circuit is a voltage controlled oscillator whose control voltage varies with temperature.

3. A high-order temperature compensated clock based on a MEMS resonator according to claim 1, characterized in that: The temperature compensation circuit includes a reference voltage module, a high-order compensation voltage module, a coefficient buffer stage, and a summing module which are connected in sequence; the reference voltage module generates a primary voltage related to temperature, the high-order compensation voltage module generates a high-order compensation voltage related to temperature according to the input primary voltage related to temperature, the coefficient buffer stage is used to scale the input power voltages of each level, and the summing module sums the scaled power voltages of each level to obtain the temperature compensation voltage.

4. A high-order temperature compensated clock based on a MEMS resonator according to claim 3, characterized in that: The reference voltage module is specifically a bandgap reference voltage source.

5. The high-order temperature compensated clock based on MEMS resonator according to claim 3, characterized in that: The high-order compensation voltage module generates a high-order compensation voltage through a cascaded analog multiplier.

6. A high-order temperature compensated clock based on a MEMS resonator according to claim 5, characterized in that: The analog multiplier of the high-order compensation voltage module adopts a Gilbert structure.

7. The high-order temperature compensated clock based on MEMS resonator according to claim 3, characterized in that: The summing module is implemented by a summing circuit.

8. A working method of a high-order temperature compensation clock based on a MEMS resonator according to any one of claims 3 to 7, characterized in that: The details are as follows: The reference voltage module generates a negative temperature coefficient voltage V that is negatively correlated with temperature. CTAT and reference voltage V REF ; The negative temperature coefficient voltage V CTAT and reference voltage V REF Sent to the high-order compensation voltage module, the high-order compensation voltage γ (V CTAT -V REF ) 2 , γ 2 (V CTAT -V REF ) 3 …γ n-1 (V CTAT -V REF ) n , γ is the scaling factor of the analog multiplier; The primary voltage output by the reference voltage generation module and the high-order compensation voltage output by the high-order compensation voltage module form the power voltages of each level and send them to the coefficient buffer stage for scaling. The power voltages of each level after scaling are a1(V CTAT -V REF ), a2γ(V CTAT -V REF ) 2 , a3γ 2 (V CTAT -V REF ) 3 ……a n γ n-1 (V CTAT -V REF ) n , where a1, a2, a3, ... a n is the scaling factor; The temperature compensation voltage can be obtained by sending the scaled voltages of each level to the summing module for summing: In C =b0+b1(V CTAT -V REF )+b2(V CTAT -V REF ) 2 +……+b n (In CTAT -V REF ) n Where b0 is the calibration voltage and b0 = a0V REF , a0 is the calibration coefficient, b1, b2, b3...b n is the product of the scaling factor and the multiplier ratio factor, and b n =a n γ n-1 .

9. The working method of a high-order temperature compensation clock based on a MEMS resonator according to claim 8, characterized in that: The coefficients b1, b2, ... b of the temperature compensation voltage are n The settings satisfy Where k is V CTAT Correlation coefficient with temperature, d1, d2, ... d n are the coefficients of the MEMS resonator temperature characteristics c1, c2, ... c n Zoom Out - K VCO The compensation voltage coefficient is obtained by multiplying the voltage by d1, that is, d1 = -c1 / K VCO d2=-c2 / K VCO ……d n =-c n / K VCO .

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