Ultra-stable crystal oscillator short-term stability system

Abstract

The invention relates to an ultra-stable crystal oscillator short-term stability system, which comprises a temperature measurement amplification circuit, which is used for acquiring a voltage difference between a thermistor and a temperature setting resistor through a balanced bridge in a three-operational-amplifier instrumentation amplifier, amplifying the voltage difference through a differential amplifier to obtain a temperature control voltage carrying offset voltage information, and sending the temperature control voltage to the temperature control amplification circuit; the signal is output to the second-stage amplification circuit; the thermistor is used for collecting the temperature of the ultra-stable crystal oscillator thermostatic bath; the temperature change compensation circuit is used for finely adjusting a temperature inflection point set value of an instrument amplifier in the temperature measurement amplification circuit, compensating frequency change caused by temperature gradient change of the thermostatic bath at high and low temperatures, and improving the stability of output frequency; the second-stage amplifying circuit is used for amplifying and outputting the difference between the standard reference voltage Vref and the temperature control voltage Vt; the error feedback control circuit is used for correcting the control voltage output by the two-stage amplification circuit to obtain a benchmark reference voltage Vref, so that the benchmark reference voltage Vref is dynamically adjusted according to temperature change, and system errors and error control voltage introduced by operational amplifier drift are reduced; and the power tube is used for heating the ultra-stable crystal oscillator thermostatic bath.

Description

Technical Field

[0001] This invention belongs to the technical field of OCXO (high stability crystal oscillator), specifically relating to a short-term stability system for an ultra-stable crystal oscillator. Background Technology

[0002] The ultra-high stability crystal oscillator (USO) is the crystal oscillator with the best frequency stability and phase noise, and its short-term stability is better than that of E. -13 The phase noise level is on the order of 1s to 30s, reaching -125dBc / Hz at 1Hz, and the long-term stability reaches E. -11 ∽E -12 / day. Ultra-high stability crystal oscillators have been applied in high-performance time and frequency applications such as deep space exploration, precision mapping, precision orbit determination, frequency measurement, and time-holding systems.

[0003] Cryostatic crystal oscillators can be categorized into single-layer and double-layer temperature-controlled oscillators based on their temperature control methods. The former uses a single temperature-controlled bath to maintain the temperature of the crystal resonator and oscillation circuit, while the latter uses two temperature-controlled baths and two temperature-controlled circuits to maintain the temperature of the crystal and its internal circuitry. Single-layer temperature-controlled oscillators have lower temperature control accuracy and poorer stability. Double-layer temperature control offers higher temperature control accuracy but also introduces problems such as increased size, power consumption, and structural complexity. The power consumption of double-layer temperature control is generally about twice that of single-layer temperature control, making it unsuitable for miniaturized, low-power applications.

[0004] The purpose of precision temperature control design is to maintain the stability of characteristics such as the output frequency of the crystal oscillator when the external ambient temperature changes. This not only helps improve the frequency-temperature stability of the crystal oscillator, but also plays a very important role in achieving excellent short-term frequency stability.

[0005] Traditional high-stability crystal oscillators use direct amplification continuous temperature control circuits. Because of the temperature gradient in the thermostat bath, changes in this gradient at high and low temperatures cause a deviation between the temperature-controlling thermistor and the crystal's operating temperature, resulting in variations in the output frequency. Furthermore, direct amplification continuous temperature control circuits suffer from offset voltage, leading to drift over long-term temperature control, affecting long-term stability and aging rate. Summary of the Invention

[0006] The technical problem solved by this invention is: addressing the issues of high power consumption in dual-layer temperature control and low accuracy in single-layer temperature control, this invention proposes an ultra-stable crystal oscillator short-term stability system, resulting in a miniaturized ultra-stable frequency source and a crystal oscillator with high short-to-medium-term stability.

[0007] The solution of this invention is: a short-term stability system for an ultra-stable crystal oscillator, comprising a temperature-sensing amplifier circuit, a temperature-change compensation circuit, a second-stage amplifier circuit, an error feedback control circuit, and a power transistor; wherein:

[0008] The temperature measurement amplification circuit acquires the voltage difference between the thermistor and the temperature setting resistor through a balanced bridge in a three-op-amp instrumentation amplifier, amplifies the voltage difference to obtain a temperature control voltage carrying offset voltage information, and outputs it to the second-stage amplification circuit; the thermistor is used to acquire the temperature of the ultra-stable crystal oscillator constant temperature bath.

[0009] Temperature compensation circuit is used to fine-tune the temperature inflection point setting of the instrumentation amplifier in the temperature measurement amplifier circuit, and to compensate for the frequency change caused by the temperature gradient change of the constant temperature bath under high and low temperatures.

[0010] The second-stage amplifier circuit converts the reference voltage V ref and temperature control voltage V t The output is amplified after differential calculation to obtain the control voltage;

[0011] The error feedback control circuit corrects the control voltage output from the two-stage amplifier circuit to obtain the reference voltage V. ref This makes the reference voltage V ref The control voltage is dynamically adjusted according to temperature changes to reduce system errors and errors introduced by operational amplifier drift.

[0012] Power transistors are used to heat the thermostatic bath of ultra-stable crystal oscillators.

[0013] Preferably, the temperature compensation circuit includes resistors R2, R3, R4, and R5, and thermistors Rt2 and Rt3;

[0014] Resistor R2 is connected in series with thermistor Rt2; resistor R2 and thermistor Rt3 are connected in parallel and then connected to resistor R4, with the other end of R4 connected to the power supply.

[0015] Resistor R3 is connected in series with thermistor Rt3; resistor R3 is connected in parallel with thermistor Rt2 and then connected to resistor R5, with the other end of R5 grounded.

[0016] Preferably, the error feedback control circuit includes resistors R15, R6, and R13; and thermistors Rt4 and Rt5.

[0017] Resistor R15 and thermistor Rt4 are connected in series at node A; resistor R13 and thermistor Rt5 are connected in series at node B; node A and node B are connected and serve as the output terminal of the error feedback control circuit.

[0018] Resistor R15 and sensitive resistor Rt5 are connected in parallel and then connected to resistor R6. The other end of R6 is connected to the power supply.

[0019] Resistor R17 and thermistor Rt4 are connected in parallel and then grounded.

[0020] Preferably, the second amplifier circuit includes resistors R8 and R9, operational amplifier OP2, resistors R10 and R11;

[0021] The non-inverting input of operational amplifier OP2 is connected to resistor R10 and the output of the error feedback control circuit. One end of resistor R10 is connected to the power supply V0. The non-inverting input of operational amplifier OP2 is also connected to resistor R11. The other end of resistor R11 is connected to resistor R12 and the collector of the power transistor. The other end of resistor R12 is connected to voltage V. s Voltage V s Used to power the power transistor;

[0022] The negative input terminal of operational amplifier OP2 is connected to resistors R8 and R9. The other end of resistor R9 is grounded, and resistor R8 is connected to the temperature control voltage V. 01 ;

[0023] The output of operational amplifier OP2 is connected to the base of the power transistor, and the emitter of the power transistor is grounded.

[0024] Preferably, the temperature measuring amplifier circuit includes a resistor R1, a thermistor Rt1, and an instrumentation amplifier;

[0025] The non-inverting input of the instrumentation amplifier is connected to the power supply.

[0026] The negative input terminal of the instrumentation amplifier is connected to the thermistor Rt1 and the resistor R1. The other end of the thermistor Rt1 is connected to the power supply, and the other end of the resistor R1 is connected in series and grounded.

[0027] The output terminal of the instrumentation amplifier is the output terminal of the temperature measurement amplifier circuit, which is used to output the temperature control voltage.

[0028] Preferably, the temperature measuring amplification circuit further includes a constant voltage sampling circuit, which includes a fourth amplifier OP4, a fifth amplifier OP5, a sixth amplifier OP6, and resistors R13 and R14; wherein:

[0029] One end of resistor R13 is connected to the power supply V0, and the other end is connected to the non-inverting input of the fourth amplifier OP4 and resistor R14. The other end of resistor R14 is grounded.

[0030] The output of the fourth amplifier OP4 is fed back to the negative input terminal, and is simultaneously connected to the positive input terminals of the fifth amplifier OP5 and the sixth amplifier OP6;

[0031] The output terminal of the fifth amplifier OP5 is connected to the temperature compensation circuit and the positive input terminal of the instrumentation amplifier, which is the first reference power supply voltage. The negative input terminal of the fifth amplifier OP5 is connected to point P of the temperature compensation circuit; point P is the connection point of the thermistor Rt3 and resistor R3 in the temperature compensation circuit.

[0032] The output of the sixth amplifier OP6 is connected to Rt1 and another positive input of the instrumentation amplifier, which is the second reference power supply voltage.

[0033] The negative inverting input of the sixth amplifier OP6 is connected to the junction of Rt1 and R1.

[0034] Preferably, the ultra-stable crystal oscillator is a single-layer thermostatic bath.

[0035] Preferably, the output voltage of the instrumentation amplifier is:

[0036]

[0037] Where G is the gain of the instrumentation amplifier; r1, r2, r3, r4, and r5 are the resistance values ​​of resistors R1, R2, R3, R4, and R5, respectively; rt2 and rt3 are the resistance values ​​of thermistors Rt2 and Rt3, respectively; and "a / / b" indicates that resistance values ​​a and b are connected in parallel.

[0038] The beneficial effects of this invention compared to the prior art are:

[0039] (1) The present invention uses analog circuits to achieve low drift and high precision in the temperature control system, and has the characteristics of miniaturization and high reliability;

[0040] (2) By superimposing a temperature control voltage error feedback control circuit, this invention solves the problem of temperature measurement deviation caused by the offset voltage, offset current and bias current of the superimposed port of the temperature measurement circuit in the direct amplification continuous temperature control circuit, which can reduce the measurement deviation voltage by more than one order of magnitude; by superimposing a temperature control voltage error feedback control circuit, the control accuracy of the temperature control voltage near the crystal inflection point temperature (i.e. the temperature of the constant temperature bath, which is generally around 85°C) can be further improved, ensuring the excellent short-term stability of the product;

[0041] (3) The present invention solves the frequency change caused by the change of ambient temperature in the temperature control system. The temperature change compensation circuit is used to fine-tune the temperature inflection point setting value of the instrument amplifier, compensate for the frequency change caused by the temperature gradient change of the constant temperature bath under high and low temperatures, and improve the stability of the output frequency.

[0042] (4) The present invention solves the problem of adjusting the maximum heating current by adjusting the value of resistor R12 without increasing the stable power consumption, thereby improving the heating efficiency of the power supply, shortening the stabilization time, avoiding current overshoot and the dispersion of the maximum heating current caused by transistor parameter dispersion, and maintaining the stability of the product status.

[0043] (5) The present invention adds a constant voltage source sampling circuit, which can further improve the temperature sampling accuracy;

[0044] (6) The present invention uses a single-layer constant temperature bath, which has a simple structure, fewer temperature control circuit components, is easy to debug and implement, and has high reliability.

[0045] (7) This invention can significantly improve the frequency stability of USO at high and low temperatures, and at the same time improve the short- and medium-term frequency stability and aging characteristics.

[0046] (8) This invention can be applied to compensation under different frequency temperature characteristics, and can also be applied to other occasions with temperature control accuracy requirements. Attached Figure Description

[0047] Figure 1 This is a block diagram illustrating the implementation of a short-term stability system for an ultrastable crystal oscillator according to an embodiment of the present invention.

[0048] Figure 2 This is a schematic diagram of the short-term stability system according to the first embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of the short-term stability system according to the second embodiment of the present invention. Detailed Implementation

[0050] To more clearly illustrate the embodiments of the present invention, specific implementation methods will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. Those skilled in the art can obtain other drawings and other implementation methods based on these drawings without any creative effort.

[0051] This invention provides a short-term stability system that combines metal Dewar thermal insulation with low-drift and high-precision temperature measurement and control. It solves the problem of low stability and susceptibility to interference in the medium and short term by adding temperature change compensation and error feedback control circuits. Its feature is that it is implemented using analog devices without increasing the size and power consumption.

[0052] To achieve the objectives of the invention described above, the present invention adopts the following technical solution:

[0053] like Figure 1 As shown, a short-term stability system for an ultra-stable crystal oscillator is disclosed. This system includes a temperature-sensing amplifier circuit, a temperature-variance compensation circuit, a second-stage amplifier circuit, an error feedback control circuit, and a power transistor; wherein:

[0054] The temperature measurement amplification circuit acquires the voltage difference between the thermistor and the temperature setting resistor through a balanced bridge in a three-op-amp instrumentation amplifier, amplifies the voltage difference to obtain a temperature control voltage carrying offset voltage information, and outputs it to the second-stage amplification circuit; the thermistor is used to acquire the temperature of the ultra-stable crystal oscillator constant temperature bath.

[0055] The temperature compensation circuit is used to fine-tune the temperature inflection point setting of the instrumentation amplifier in the temperature measurement amplifier circuit, compensate for the frequency changes caused by the temperature gradient changes of the constant temperature bath under high and low temperatures, and improve the stability of the output frequency. The instrumentation amplifier is a three-operation amplifier instrument. It collects the voltage difference between the thermistor and the temperature setting resistor through a balanced bridge. By utilizing its offset characteristic which is an order of magnitude smaller than that of a general direct amplifier circuit, the temperature measurement accuracy can be improved.

[0056] The second-stage amplifier circuit converts the reference voltage V ref and temperature control voltage V t The output is amplified after differential calculation to obtain the control voltage;

[0057] The error feedback control circuit corrects the control voltage output from the two-stage amplifier circuit to obtain the reference voltage V. ref This makes the reference voltage V ref The control voltage is dynamically adjusted according to temperature changes to reduce system errors and errors introduced by operational amplifier drift.

[0058] Power transistors are used to heat the thermostatic bath of ultra-stable crystal oscillators.

[0059] The temperature compensation circuit includes resistors R2, R3, R4, and R5, and thermistors Rt2 and Rt3.

[0060] Resistor R2 is connected in series with thermistor Rt2; resistor R2 and thermistor Rt3 are connected in parallel and then connected to resistor R4, with the other end of R4 connected to the power supply.

[0061] Resistor R3 is connected in series with thermistor Rt3; resistor R3 is connected in parallel with thermistor Rt2 and then connected to resistor R5, with the other end of R5 grounded.

[0062] The error feedback control circuit includes resistors R15, R6, and R13; and thermistors Rt4 and Rt5.

[0063] Resistor R15 and thermistor Rt4 are connected in series at node A; resistor R13 and thermistor Rt5 are connected in series at node B; node A and node B are connected and serve as the output terminal of the error feedback control circuit.

[0064] Resistor R15 and sensitive resistor Rt5 are connected in parallel and then connected to resistor R6. The other end of R6 is connected to the power supply.

[0065] Resistor R17 and thermistor Rt4 are connected in parallel and then grounded.

[0066] The second-stage amplifier circuit consists of a single operational amplifier, used to drive the power transistor. This second-stage amplifier circuit includes resistors R8 and R9, operational amplifier OP2, resistors R10 and R11.

[0067] The non-inverting input of operational amplifier OP2 is connected to resistor R10 and the output of the error feedback control circuit. One end of resistor R10 is connected to the power supply V0. The non-inverting input of operational amplifier OP2 is also connected to resistor R11. The other end of resistor R11 is connected to resistor R12 and the collector of the power transistor. The other end of resistor R12 is connected to voltage V. s Voltage V s Used to power the power transistor;

[0068] The negative input terminal of operational amplifier OP2 is connected to resistors R8 and R9. The other end of resistor R9 is grounded, and resistor R8 is connected to the temperature control voltage.

[0069] The output of operational amplifier OP2 is connected to the base of the power transistor, and the emitter of the power transistor is grounded.

[0070] Op-amp OP2 is a direct amplifier comparator circuit. OP2 converts the reference voltage V... ref and temperature control voltage V t The output is amplified after differential calculation, which also cancels out the effect of offset voltage.

[0071] Preferably, the temperature measuring amplifier circuit includes a resistor R1, a thermistor Rt1, and an instrumentation amplifier;

[0072] The non-inverting input of the instrumentation amplifier is connected to the power supply.

[0073] The negative input terminal of the instrumentation amplifier is connected to thermistor Rt1 and resistor R1. The other end of thermistor Rt1 is connected to the power supply, and the other end of resistor R1 is connected in series and grounded.

[0074] The output terminal of the instrumentation amplifier is the output terminal of the temperature measurement amplifier circuit, which is used to output the temperature control voltage.

[0075] like Figure 2 As shown, the temperature measurement amplifier circuit also includes a constant voltage sampling circuit, which can further improve the temperature sampling accuracy. The constant voltage sampling circuit includes a fourth amplifier OP4, a fifth amplifier OP5, a sixth amplifier OP6, and resistors R13 and R14; wherein:

[0076] One end of resistor R13 is connected to the power supply V0, and the other end is connected to the non-inverting input of the fourth amplifier OP4 and resistor R14. The other end of resistor R14 is grounded.

[0077] The output of the fourth amplifier OP4 is fed back to the negative input terminal, and the positive input terminals of the fifth amplifier OP5 and the sixth amplifier OP6 are also connected.

[0078] The output terminal of the fifth amplifier OP5 is connected to the temperature compensation circuit and a positive input terminal of the instrumentation amplifier, which is the first reference power supply voltage. The negative input terminal of the fifth amplifier OP5 is connected to point P of the temperature compensation circuit; point P is the connection point of the thermistor Rt3 and resistor R3 in the temperature compensation circuit.

[0079] The output of the sixth amplifier OP6 is connected to Rt1 and another positive input of the instrumentation amplifier, which is the second reference power supply voltage.

[0080] The negative inverting input of the sixth amplifier OP6 is connected to the junction of Rt1 and R1.

[0081] The ultra-stable crystal oscillator thermostat bath is a single-layer thermostat bath with a simple structure, fewer temperature control circuit components, easy debugging and implementation, and high reliability.

[0082] Because a feedback control circuit is added to the reference voltage Vref, the reference voltage can be dynamically adjusted according to changes in the external temperature. This allows the output Vt to carry feedback control voltage information, fine-tuning the temperature control voltage and controlling the power transistor to keep the temperature at the control point stable.

[0083] Depend on Figure 2 It can be seen that the output voltage of the instrumentation amplifier is:

[0084]

[0085] Where G is the gain of the instrumentation amplifier; r1, r2, r3, r4, and r5 are the resistance values ​​of resistors R1, R2, R3, R4, and R5, respectively; rt2 and rt3 are the resistance values ​​of thermistors Rt2 and Rt3, respectively; "a / / b" indicates that resistance values ​​a and b are connected in parallel; and V0 is the power supply voltage.

[0086] The heating current of the temperature control system is:

[0087]

[0088] in:

[0089] Re = (r 16 +r 15 / / rt5) / / (r 17 / / rt4)

[0090] V0'=V0(r 17 / / rt4) / (r 16 +r 15 / / rt5+r 17 / / rt4).

[0091] r8, r9, r 10 r 11 r12 r 15 r 16 r 17 The values ​​of resistors R8, R9, R10, R11, R12, R15, R16, and R17 are respectively; rt4 and rt5 are the values ​​of thermistors Rt4 and Rt5, respectively.

[0092] Example 1: As Figure 2 As shown

[0093] Step 1: Select thermistors Rt1 to Rt5, instrumentation amplifiers, OP2 operational amplifiers, and other components according to the actual application temperature range and reference voltage;

[0094] It is recommended that the thermistor Rt1 be selected with a resistance of approximately 10KΩ near the inflection point temperature. Thermistors Rt2 to Rt5 can be of the same specification as Rt1 or different, depending on the actual situation; there are no specific requirements. There are no specific requirements for the instrumentation amplifier, operational amplifier OP2, and operational amplifiers OP4 to OP6; they can be selected based on the actual circuit requirements.

[0095] Step 2: Short-circuit (to ground) both the instrumentation amplifier and the input terminal of the second-stage operational amplifier in the temperature control circuit; measure the offset voltage value at high and low temperatures, and adjust the output voltage V_error of the error feedback control circuit to make the offset voltage 0. Based on the recorded V_error value at different temperature points and the resistance values ​​of Rt4 and Rt5, use the least squares algorithm to calculate the device parameters of R15, R16, and R17 in the error feedback control circuit.

[0096] V0'=V0(r 17 / / rt4) / (r 16 +r 15 / / rt5+r 17 / / rt4) (3)

[0097] Based on the above formula, test three or more sets of V0, V error value V0', the resistance values ​​rt4 and rt5 of thermistors Rt4 and Rt5, and the device parameters R15, R16, and R17 can be calculated using formula 3.

[0098] Step 3: Based on the crystal inflection point temperature and the resistance value of thermistor Rt1 near the inflection point temperature, the installation positions of thermistors Rt2 and Rt3 are determined. One is far away from the constant temperature bath (PCB edge), and the other is close to the constant temperature bath. Here, Rt2 and Rt3 are not distinguished.

[0099] Step 4: Select the value of R12 based on the maximum startup power consumption. Use the power supply output reference voltage as Vref to replace the voltage generated by the feedback control circuit. Adjust the power supply output reference voltage under high and low temperature conditions to keep the temperature of the constant temperature bath (product output frequency) constant. Record the reference voltage value V at different temperature points. ref Simultaneously record the resistance values ​​of Rt2 and Rt3 at different temperatures;

[0100] Step 5: Utilize the reference voltage value V set at different temperature points ref Using the measured values ​​of Rt2 and Rt3, the least squares method is employed for polynomial fitting to determine the values ​​of R2, R3, R4, and R5 in the feedback control circuit. For ease of calculation, r4 = r5 = 10kΩ is initially chosen, and the values ​​are obtained by applying V at two temperature points. ref The resistance values ​​of R2 and R3 are calculated by solving for the values ​​of Rt2 and Rt3.

[0101]

[0102] Equation (4) utilizes V0 and V at different temperature points ref From the two sets of values ​​r1, r2, r3, r4, r5, rt2, and rt3, the set values ​​r2 and r3 of R2 and R3 can be calculated.

[0103] Reference Figure 3 Excellent short-term stability system, main implementation methods:

[0104] exist Figure 2 Based on this, by adding a constant voltage sampling circuit, the sampling rate of the temperature control circuit is kept constant, thus improving the linearity of the sampling.

[0105] Example 2: Figure 3 As shown:

[0106] The reference voltage divider resistors R13 and R14, together with the operational amplifier OP4, form a constant voltage source, whose output voltage is:

[0107]

[0108] U OP4 r is the output voltage of the OP4 operational amplifier. 13 r 14 These are the resistance values ​​of resistors R13 and R14, respectively.

[0109] Step 2: The sampling circuit consists of operational amplifier OP5, operational amplifier OP6, temperature compensation circuit, thermistor Rt1 and resistor R1. Operational amplifier OP5, operational amplifier OP6, equivalent resistor R5' (r5' = rt2 / / r3+r5) and resistor R1 form the sampling circuit.

[0110] Taking operational amplifier OP6 (same as OP5) as an example for analysis, the sampling current I flowing through the thermistor Rt1 is sampled as U. op4 / r1, the output voltage of operational amplifier OP6 is:

[0111] U op6 =I 采样 ×rt1+U op4 (6)

[0112] Similarly, the sampling current I flowing through the equivalent resistance R5' is sampled as U. op4 / r5', the output voltage of operational amplifier OP5 is:

[0113] U op5 =I 采样 ×r4'+U op4 (7)

[0114] The equivalent resistance R4' has a value of r4' = rt3 / / r2 + r4.

[0115] From equation (1), we can see that:

[0116] V o1 =G(U op5 -U op6 (8)

[0117] Step 3: Subsequent steps can be found here. Figure 2 The steps in the process.

[0118] In summary, the present invention has the following advantages:

[0119] (1) The present invention introduces an instrumentation amplifier into a direct-amplifier circuit composed of operational amplifiers, and improves the temperature measurement accuracy by utilizing its offset characteristics which are one order of magnitude smaller than those of a general direct-amplifier circuit.

[0120] (2) The present invention solves the problem of frequency change caused by changes in ambient temperature in the temperature control system by finely adjusting the reference voltage under different ambient temperatures.

[0121] (3) The present invention also incorporates an error control circuit in the second stage amplifier circuit to further improve the control accuracy of the temperature control voltage near the inflection point temperature and ensure the excellent short-term stability of the product.

[0122] (4) This invention can significantly improve the frequency stability of USO at high and low temperatures, and at the same time improve the short- and medium-term frequency stability and aging characteristics.

[0123] (5) This invention can be applied to compensation under different frequency temperature characteristics, and can also be applied to other occasions with temperature control accuracy requirements.

[0124] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A short-term stability system for an ultra-stable crystal oscillator, characterized in that... It includes a temperature-sensing amplifier circuit, a temperature change compensation circuit, a second-stage amplifier circuit, an error feedback control circuit, and a power transistor; among which: The temperature measurement amplification circuit acquires the voltage difference between the thermistor and the temperature setting resistor through a balanced bridge in a three-op-amp instrumentation amplifier, amplifies the voltage difference to obtain a temperature control voltage carrying offset voltage information, and outputs it to the second-stage amplification circuit; the thermistor is used to acquire the temperature of the ultra-stable crystal oscillator constant temperature bath. Temperature compensation circuit is used to fine-tune the temperature inflection point setting of the instrumentation amplifier in the temperature measurement amplifier circuit, and to compensate for the frequency change caused by the temperature gradient change of the constant temperature bath under high and low temperatures. The second-stage amplifier circuit converts the reference voltage V ref and temperature control voltage V t The output is amplified after differential calculation to obtain the control voltage; The error feedback control circuit corrects the control voltage output from the two-stage amplifier circuit to obtain the reference voltage V. ref This makes the reference voltage V ref The control voltage is dynamically adjusted according to temperature changes to reduce system errors and errors introduced by operational amplifier drift. Power transistors are used to heat the thermostatic bath of ultra-stable crystal oscillators.

2. The ultra-stable crystal oscillator short-term stability system according to claim 1, characterized in that, The temperature compensation circuit includes resistors R2, R3, R4, and R5, and thermistors Rt2 and Rt3. Resistor R2 is connected in series with thermistor Rt2; resistor R2 and thermistor Rt3 are connected in parallel and then connected to resistor R4, with the other end of R4 connected to the power supply. Resistor R3 is connected in series with thermistor Rt3; resistor R3 is connected in parallel with thermistor Rt2 and then connected to resistor R5, with the other end of R5 grounded.

3. The ultra-stable crystal oscillator short-term stability system according to claim 1, characterized in that, The error feedback control circuit includes resistors R15, R6, and R13; and thermistors Rt4 and Rt5. Resistor R15 and thermistor Rt4 are connected in series at node A; resistor R13 and thermistor Rt5 are connected in series at node B; node A and node B are connected and serve as the output terminal of the error feedback control circuit. Resistor R15 and sensitive resistor Rt5 are connected in parallel and then connected to resistor R6. The other end of R6 is connected to the power supply. Resistor R17 and thermistor Rt4 are connected in parallel and then grounded.

4. The ultra-stable crystal oscillator short-term stability system according to claim 1, characterized in that, The second amplifier circuit includes resistors R8 and R9, operational amplifier OP2, resistors R10 and R11; The non-inverting input of operational amplifier OP2 is connected to resistor R10 and the output of the error feedback control circuit. One end of resistor R10 is connected to the power supply V0. The non-inverting input of operational amplifier OP2 is also connected to resistor R11. The other end of resistor R11 is connected to resistor R12 and the collector of the power transistor. The other end of resistor R12 is connected to voltage V. s Voltage V s Used to power the power transistor; The negative input terminal of operational amplifier OP2 is connected to resistors R8 and R9. The other end of resistor R9 is grounded, and resistor R8 is connected to the temperature control voltage V. 01 ; The output of operational amplifier OP2 is connected to the base of the power transistor, and the emitter of the power transistor is grounded.

5. The short-term stability system of an ultra-stable crystal oscillator according to claim 1, characterized in that, The temperature measurement amplifier circuit includes a resistor R1, a thermistor Rt1, and an instrumentation amplifier; The non-inverting input of the instrumentation amplifier is connected to the power supply. The negative input terminal of the instrumentation amplifier is connected to the thermistor Rt1 and the resistor R1. The other end of the thermistor Rt1 is connected to the power supply, and the other end of the resistor R1 is connected in series and grounded. The output terminal of the instrumentation amplifier is the output terminal of the temperature measurement amplifier circuit, which is used to output the temperature control voltage.

6. The short-term stability system of an ultra-stable crystal oscillator according to claim 5, characterized in that, The temperature measurement amplification circuit further includes a constant voltage sampling circuit, which comprises a fourth amplifier OP4, a fifth amplifier OP5, a sixth amplifier OP6, and resistors R13 and R14; wherein: One end of resistor R13 is connected to the power supply V0, and the other end is connected to the non-inverting input of the fourth amplifier OP4 and resistor R14. The other end of resistor R14 is grounded. The output of the fourth amplifier OP4 is fed back to the negative input terminal, and is simultaneously connected to the positive input terminals of the fifth amplifier OP5 and the sixth amplifier OP6; The output terminal of the fifth amplifier OP5 is connected to the temperature compensation circuit and the positive input terminal of the instrumentation amplifier, which is the first reference power supply voltage. The negative input terminal of the fifth amplifier OP5 is connected to point P of the temperature compensation circuit; point P is the connection point of the thermistor Rt3 and resistor R3 in the temperature compensation circuit. The output of the sixth amplifier OP6 is connected to Rt1 and another positive input of the instrumentation amplifier, which is the second reference power supply voltage. The negative inverting input of the sixth amplifier OP6 is connected to the junction of Rt1 and R1.

7. The ultra-stable crystal oscillator short-term stability system according to claim 1, characterized in that, The ultra-stable crystal oscillator is a single-layer thermostatic bath.

8. The ultra-stable crystal oscillator short-term stability system according to claim 1, characterized in that, The output voltage of the instrumentation amplifier is: Where G is the gain of the instrumentation amplifier; r1, r2, r3, r4, and r5 are the resistance values ​​of resistors R1, R2, R3, R4, and R5, respectively; rt2 and rt3 are the resistance values ​​of thermistors Rt2 and Rt3, respectively; and "a / / b" indicates that resistance values ​​a and b are connected in parallel.

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