Crystal oscillator and atomic clock

Abstract

The invention provides a crystal oscillator and an atomic clock, and relates to the technical field of oscillators, the crystal oscillator comprises a packaging cavity, a crystal, a temperature sensor and a cantilever beam assembly, the crystal, the temperature sensor and the cantilever beam assembly are arranged in a containing cavity of the packaging cavity, and the packaging cavity is of a vacuum packaging structure. The crystal and the temperature sensor are arranged on the cantilever beam assembly, the crystal and the temperature sensor are electrically connected with different connection points of the packaging cavity through the cantilever beam assembly, and the temperature sensor is arranged around the crystal; the cantilever beam assembly comprises a heating module, and when the temperature sensor monitors that the temperature of the area where the crystal is located is smaller than a preset temperature threshold value, the heating module heats the crystal. The energy loss of air damping to the high-frequency vibration of the crystal is eliminated, the Q value is improved, and the phase noise suppression capability is enhanced; accurate control over the temperature of the area where the crystal is located is achieved, the thermal response speed and the temperature control precision are improved, and the problem that an existing crystal oscillator is poor in stability is solved.

Description

Technical Field

[0001] This application relates to the technical field of oscillators, and particularly to a crystal oscillator and an atomic clock. Background Art

[0002] As a core frequency control component, crystal oscillators are widely used in fields such as satellite navigation and quantum communication. A stable reference frequency source can be provided through crystal oscillators and atomic clocks to ensure the timing synchronization and signal accuracy of devices.

[0003] However, when the crystal vibrates at high frequencies, it is affected by air damping, resulting in energy loss. This limits the Q value, a key parameter for measuring the performance of the resonator, and weakens the ability to suppress phase noise. Its typical phase noise value is only -120 dBc / Hz@1 kHz, which is likely to cause problems such as signal distortion and increased bit error rate in fields with high signal accuracy requirements such as communication and radar. Moreover, existing crystal oscillators usually need to heat multiple components with different thermal characteristics, such as the crystal, circuit board, and housing, resulting in slow thermal response and insufficient temperature control accuracy. This makes the frequency stability and phase stability of crystal oscillators poor, making it difficult to meet the timing synchronization requirements in high-precision scenarios such as communication and navigation.

[0004] It can be seen that there are problems with poor stability in existing crystal oscillators. Summary of the Invention

[0005] Embodiments of this application provide a crystal oscillator and an atomic clock to solve the problem of poor stability in existing crystal oscillators.

[0006] Embodiments of this application provide a crystal oscillator, including a packaging cavity, a crystal, a temperature sensor, and a cantilever beam assembly. The crystal, the temperature sensor, and the cantilever beam assembly are arranged in the accommodation cavity of the packaging cavity. The packaging cavity is a vacuum packaging structure. The crystal and the temperature sensor are arranged on the cantilever beam assembly. The crystal and the temperature sensor are electrically connected to different connection points of the packaging cavity through the cantilever beam assembly, and the temperature sensor surrounds the crystal. Among them, the cantilever beam assembly includes a heating module. When the temperature sensor monitors that the temperature in the area where the crystal is located is less than a preset temperature threshold, the heating module heats the crystal.

[0007] Optionally, the cantilever beam assembly further includes a cantilever beam bracket and a thin film layer. The cantilever beam bracket is adapted to the accommodation cavity. The thin film layer is disposed on the top surface of the cantilever beam bracket. The heating module is disposed in the interlayer of the thin film layer. The thin film layer is integrated with metal traces. The crystal and the temperature sensor are disposed on the thin film layer, and the crystal and the temperature sensor are electrically connected to different connection points of the encapsulation cavity through the metal traces.

[0008] Optionally, the projection of the crystal onto the thin film layer is located in the region where the heating module is located.

[0009] Optionally, the heating module is a concentric ring structure formed by winding a heating wire.

[0010] Optionally, the thin film layer is a polyimide thin film.

[0011] Optionally, the temperature sensor is a negative temperature coefficient NTC resistor.

[0012] Optionally, the encapsulation cavity includes a cover plate and a base. The cover plate and the base cooperate to form the accommodation cavity. A sealing coating is provided at the contact position between the cover plate and the base.

[0013] Optionally, a getter is provided on the side of the cover plate facing the accommodation cavity.

[0014] Optionally, the encapsulation cavity is made of a metal-ceramic composite material, and the vacuum degree of the encapsulation cavity is less than or equal to 10 -1 Pa.

[0015] An embodiment of the present application further provides an atomic clock, including the crystal oscillator described above.

[0016] In the embodiment of the present application, the crystal, the temperature sensor, and the cantilever beam assembly are disposed in the accommodation cavity of the encapsulation cavity, and the encapsulation cavity adopts a vacuum encapsulation structure to eliminate the energy loss of the air damping on the high-frequency vibration of the crystal, improve the Q value and enhance the phase noise suppression ability; and, the cantilever beam assembly is used to achieve mechanical shock absorption and thermal isolation, improve the seismic performance of the crystal, and reduce the influence of external temperature fluctuations on the crystal; the temperature sensor is disposed around the crystal, and cooperate with the heating module of the cantilever beam assembly to achieve precise control of the temperature in the region where the crystal is located. Compared with the traditional overall heating method, the thermal response speed and temperature control accuracy are greatly improved, the problem of poor stability of the existing crystal oscillator is solved, and the timing synchronization requirements of high-precision scenarios are met. Description of the Drawings

[0017] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0018] Figure 1 is a schematic structural diagram of a crystal oscillator provided by an embodiment of the present application; Figure 2 is a phase noise curve graph of a common crystal oscillator; Figure 3 is a phase noise curve graph of the crystal oscillator provided by the embodiment of the present application; Figure 4 is a schematic structural diagram of an atomic clock provided by the embodiment of the present application. Detailed implementation manners

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0020] Terms such as "first" and "second" in the embodiments of the present application are used to distinguish similar objects and do not necessarily describe a specific order or sequence. In addition, the terms "include" and "have" and any of their variants are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0021] As Figure 1 shown, an embodiment of the present application provides a crystal oscillator. The crystal oscillator 1 includes a package cavity 10, a crystal 20, a temperature sensor 30, and a cantilever beam assembly 40. The crystal 20, the temperature sensor 30, and the cantilever beam assembly 40 are disposed in the accommodation cavity of the package cavity 10. The package cavity 10 is a vacuum package structure. The crystal 20 and the temperature sensor 30 are disposed on the cantilever beam assembly 40. The crystal 20 and the temperature sensor 30 are electrically connected to different connection points of the package cavity 10 through the cantilever beam assembly 40, and the temperature sensor 30 is disposed around the crystal 20; Among them, the cantilever beam assembly 40 includes a heating module 401. When the temperature sensor 30 monitors that the temperature in the area where the crystal 20 is located is lower than a preset temperature threshold, the heating module 401 heats the crystal 20.

[0022] For the crystal oscillator 1 provided in the embodiment of the present application, the crystal 20, the temperature sensor 30, and the cantilever beam assembly 40 are arranged in the accommodation cavity of the packaging cavity 10, and the packaging cavity 10 adopts a vacuum packaging structure to eliminate the energy loss of the high-frequency vibration of the crystal 20 caused by air damping, improve the Q value, and enhance the phase noise suppression ability; moreover, the cantilever beam assembly 40 is used to achieve mechanical shock absorption and thermal isolation, improve the seismic performance of the crystal 20, and reduce the influence of external temperature fluctuations on the crystal 20; the temperature sensor 30 is arranged around the crystal 20 and, in cooperation with the heating module 401 of the cantilever beam assembly 40, realizes precise control of the temperature in the area where the crystal 20 is located. Compared with the traditional overall heating method, the thermal response speed and temperature control accuracy are greatly improved, the problem of poor stability of the existing crystal oscillator is solved, and the timing synchronization requirements of high-precision scenarios are met.

[0023] Among them, the crystal 20 and the temperature sensor 30 are electrically connected to different connection points of the packaging cavity 10 through the cantilever beam assembly 40. Different connection points can correspond to different control circuits or modules connected externally to realize independent signal transmission, ensure that the oscillation signal generated by the crystal 20 can be stably transmitted to the frequency output device, and the temperature signal collected by the temperature sensor 30 is accurately transmitted to the temperature control device to avoid mutual interference between signals and ensure the accuracy of signal transmission; moreover, the oscillation function and the temperature control function of the crystal oscillator 1 are relatively independent, which is convenient for external devices to accurately control and monitor them respectively, thereby improving the stability and reliability of the entire crystal oscillator 1 and meeting the efficient collaborative work requirements of different functional modules.

[0024] Optionally, the cantilever beam assembly 40 further includes a cantilever beam bracket 403 and a thin film layer 402. The cantilever beam bracket 403 is adapted to the accommodation cavity. The thin film layer 402 is arranged on the top surface of the cantilever beam bracket 403. The heating module 401 is arranged in the sandwich of the thin film layer 402. The thin film layer 402 is integrated with metal traces. The crystal 20 and the temperature sensor 30 are arranged on the thin film layer 402, and the crystal 20 and the temperature sensor 30 are electrically connected to different connection points of the packaging cavity 10 through the metal traces.

[0025] In this embodiment, the cantilever beam bracket 403 serves as the basic bracket disposed in the encapsulation cavity 10. The cantilever beam bracket 403 is adapted to the accommodation cavity, providing stable support for the heating module 401, the thin film layer 402, the crystal 20, the temperature sensor 30, etc. disposed on the cantilever beam bracket 403. Precise local heating of the area where the crystal 20 is located is achieved through the heating module 401. The heating module 401 is disposed in the interlayer of the thin film layer 402. By utilizing the good heat insulation performance of the thin film layer 402, heat dissipation is effectively reduced, and the stability of the working temperature of the crystal 20 is maintained. At the same time, an independent electrical connection channel is constructed through the metal traces integrated in the thin film layer 402, enabling the crystal 20 and the temperature sensor 30 to be connected to the corresponding control circuits or modules outside the encapsulation cavity 10 through different connection points respectively. This not only ensures the independent transmission and precise control of the oscillation signal and the temperature signal, avoiding signal interference, but also realizes low parasitic parameter electrical connection by optimizing the wiring layout, reducing the signal transmission loss, and further improving the stability and reliability of signal transmission. With the mechanical support and shock absorption functions of the cantilever beam bracket 403, the overall performance of the crystal oscillator 1 is comprehensively improved.

[0026] Optionally, the projection of the crystal 20 onto the thin film layer 402 is located in the area where the heating module 401 is located.

[0027] In this embodiment, the projection of the crystal 20 onto the thin film layer 402 is located in the area where the heating module 401 is located to ensure that the heat generated by the heating module 401 can act on the crystal 20 precisely and efficiently. The heat transfer loss and delay are minimized to the greatest extent, enabling the crystal 20 to quickly reach and maintain the optimal working temperature. At the same time, problems such as local overheating or uneven heating caused by misalignment of the heating area are avoided. With the real-time monitoring of the temperature sensor 30, precise closed-loop control of the crystal temperature is achieved, thereby effectively improving the frequency stability and overall performance of the crystal oscillator.

[0028] Optionally, the thin film layer 402 is a polyimide thin film.

[0029] In this embodiment, a polyimide (PI) thin film can be used as the thin film layer 402. The PI thin film has characteristics such as high temperature resistance (it can withstand high temperatures above 200°C for a long time), excellent electrical insulation, high mechanical strength, and good flexibility. It can carry the crystal 20 and the temperature sensor 30, ensuring the structural stability of the cantilever beam assembly 40. And it can cooperate with the heating module 401 in the interlayer to reduce heat dissipation and maintain the stable working temperature of the crystal 20. At the same time, the good insulation performance of the PI thin film helps the integrated metal traces to achieve low parasitic parameter electrical connection, reduce signal transmission loss, avoid interference, and comprehensively improve the performance and reliability of the crystal oscillator.

[0030] In one example, the heating module 401 can be a gold thin film heater, or a platinum thin film heater with a thickness of 5μm to 10μm integrated in the PI film, which can achieve rapid heat conduction; the resistance value of the gold thin film heater is precisely controlled at 50Ω±0.5Ω, ensuring that the heater heats up quickly at appropriate power, and facilitating circuit design and precise adjustment of the temperature control system; in this way, the crystal oscillator 1 can quickly reach and stably maintain a preset operating temperature, effectively improving the response speed and accuracy of the overall temperature control.

[0031] In another example, the heating module 401 may be a concentric ring structure formed by a heating wire.

[0032] In this example, the heating module 401 is set to a concentric ring structure formed by a heating wire. When current flows through the heating wire, the current directions on adjacent rings are opposite. According to Ampere's law, the magnetic fields generated by the reverse currents cancel each other out, reducing the equivalent inductance of the heating wire, reducing the parasitic capacitance, and effectively suppressing high-frequency oscillations, thereby reducing the electromagnetic interference generated when power is turned on. The electromagnetic compatibility of the crystal oscillator is improved, so that it can still maintain stable operation in complex electromagnetic environments, especially suitable for high-precision application scenarios such as satellite navigation and quantum communication that are sensitive to electromagnetic interference.

[0033] In addition, the crystal 20 is placed in the center of the ring to ensure that the heat generated by the heating wire can be evenly radiated to the crystal in the circumferential direction, effectively avoiding thermal stress and temperature control deviation caused by local temperature differences; and the concentric ring structure realizes the maximum laying of the heating wire in a limited space, while ensuring the heating efficiency, it is easy to integrate with the thin film layer 402, and cooperate with the temperature control system to accurately adjust the output power, achieve stable control of the crystal temperature, and improve the stability and reliability of the crystal oscillator.

[0034] Optionally, the packaging cavity 10 is made of a metal-ceramic composite material, and the vacuum degree of the packaging cavity is less than or equal to 10 -1 Pa.

[0035] In this embodiment, the packaging cavity 10 can be made of a metal-ceramic composite material, and the vacuum degree is controlled to be less than or equal to 10 -1 Pa, achieving dual optimization of mechanical properties and vacuum environment. Among them, the metal-ceramic composite material has the advantages of high toughness of metal and high hardness, corrosion resistance, and strong insulation of ceramics, ensuring the structural safety of internal crystal 20, temperature sensor 30 and other components, and can effectively isolate external electromagnetic interference. The vacuum degree is controlled to be less than or equal to 10 -1Pa can weaken the influence of air damping on the high-frequency vibration of the crystal, reduce the energy loss (steady-state power consumption ≤ 0.5 W (when the output is 10 MHz)), improve the quality factor Q value of the crystal, thereby enhancing the phase noise suppression ability, and enabling the crystal oscillator to maintain excellent frequency stability and reliability in complex application scenarios.

[0036] Optionally, the temperature sensor 30 is a negative temperature coefficient NTC resistor.

[0037] In this embodiment, a negative temperature coefficient (NTC) resistor is used as the temperature sensor 30. By utilizing the characteristic that the resistance value of the NTC resistor decreases non-linearly with the increase of temperature, the temperature change in the area where the crystal 20 is located can be accurately monitored. Specifically, the NTC resistor has the advantages of fast response speed (millisecond level), high temperature measurement accuracy (±0.01 °C), small size and easy integration, etc. It can be closely arranged around the crystal and can provide real-time feedback on the crystal surface temperature. After circuit compensation using the NTC resistor characteristics, a precise closed-loop control can be formed with the heating module 401. When the temperature in the area where the crystal 20 is located is lower than the preset threshold, heating can be quickly started, and the heating power can be dynamically adjusted according to the change of the resistance value to ensure that the crystal always operates in a stable temperature range (temperature control accuracy ±0.01 °C (24-hour drift)), effectively improving the frequency stability and environmental adaptability of the crystal oscillator 1.

[0038] Among them, three NTC resistors can be arranged around the crystal 20. The temperature data at different circumferential positions of the crystal 20 can be collected in real time through the NTC resistors, and the local thermal deviation is eliminated by calculating the average value of the three-point temperatures. The size of each NTC resistor can be 1.0 mm × 0.5 mm × 0.3 mm, realizing a miniaturized design, enabling the NTC resistor to closely fit the crystal 20 and shortening the thermal response time. When any NTC resistor detects that the temperature deviates from the preset value, the heating power is immediately adjusted through the temperature control circuit, reducing the temperature gradient at different positions in the area where the crystal 20 is located, improving the frequency stability, and being applicable to high-precision oscillation scenarios with strict requirements for temperature uniformity.

[0039] Moreover, it can cooperate with a digital proportional integral derivative (PID) control algorithm with a 1 ms sampling period to achieve high-frequency precise control of the temperature of the crystal 20. The digital PID algorithm quickly responds to the deviation through the proportional term, eliminates the static error through the integral term, and suppresses the temperature overshoot through the derivative term. Combined with the non-linear characteristic compensation of the NTC, the temperature control accuracy is improved to ±0.01 °C, and the temperature adjustment response time is shortened to within 50 ms, effectively suppressing the influence of ambient temperature fluctuations on the crystal frequency, and being applicable to precision oscillation applications with strict requirements for temperature stability.

[0040] Optionally, the crystal 20 can be a high-Q crystal, and the crystal 20 is suspended and supported by a PI film.

[0041] In this embodiment, the crystal 20 can adopt Stress Compensated Cut (SC) to improve the stability of the crystal 20 during operation. In combination with its inherent high-Q (Q value ≥ 2×10 6 ), the phase noise can be effectively reduced. The PI film suspension support structure utilizes the high flexibility and low thermal conductivity (thermal conductivity ≤ 0.1 W / m·K) of the polyimide material to suspend and fix the crystal, isolate the transmission of external mechanical vibrations, and at the same time reduce the heat conduction loss.

[0042] Optionally, the encapsulation cavity 10 includes a cover plate 101 and a base 102. The cover plate 101 and the base 102 cooperate to form the accommodation cavity, and a sealing coating is provided at the contact position between the cover plate 101 and the base 102.

[0043] In this embodiment, the cover plate 101 and the base 102 made of cermet can be precisely processed to form a micro-nano level bonding surface at the contact position between the cover plate 101 and the base 102, and a sealing coating (such as a gold-tin alloy solder or a glass glaze sealant) is provided. After high-temperature sintering, the interface gap is filled to form a continuous and dense sealing ring, which improves the vacuum degree of the encapsulation cavity 10 and ensures that the high vacuum degree of ≤ 10 -1 Pa is maintained under severe environmental changes, providing a long-term stable working environment for the internal crystal 20 and improving the anti-aging performance and reliability of the oscillator.

[0044] Optionally, an getter 50 is provided on the side of the cover plate 101 facing the accommodation cavity.

[0045] In this embodiment, a getter 50 is provided on the side of the cover plate 101 facing the accommodation cavity. The getter 50 adsorbs trace gas molecules remaining inside the cavity (such as water vapor, nitrogen, etc. remaining during the manufacturing process), continuously maintaining the high vacuum degree of the cavity. The getter 50 can be an active metal alloy such as barium or zirconium, which can chemically react or physically adsorb with gases in a vacuum environment, further improving the vacuum degree of the encapsulation cavity 10, effectively avoiding the damping effect of the remaining gas molecules on the high-frequency vibration of the crystal, continuously ensuring the high-Q characteristics of the crystal, and at the same time suppressing the vacuum degree attenuation caused by the desorption of gas molecules at high temperatures, so that the crystal oscillator can still maintain excellent frequency stability and phase noise performance during long-term operation.

[0046] As Figure 2 and Figure 3 shown, Figure 2 is the phase noise curve graph of a common crystal oscillator, Figure 3This is the phase noise curve graph of the crystal oscillator provided by the embodiment of the present application. The phase noise of a common crystal oscillator is -120 dBc / Hz @1kHz. The crystal oscillator 1 provided by the embodiment of the present application eliminates air damping, optimizing the phase noise to -150 dBc / Hz @1kHz (a 20 dB improvement compared to a common crystal oscillator).

[0047] As Figure 4 shown, the embodiment of the present application also provides an atomic clock, which includes a chip atomic clock housing 2, a physical optical path system 3, a control circuit system 4, and a crystal oscillator 1. The crystal oscillator 1, the physical optical path system 3, and the control circuit system 4 are all arranged in the cavity of the chip atomic clock housing 2. The crystal oscillator 1 is arranged on the control circuit system 4. The physical optical path system 3 can also be arranged on the control circuit system 4, and the crystal oscillator 1 is electrically connected to the control circuit system 4 through a packaging cavity 10.

[0048] In this embodiment, a vacuum-packaged crystal oscillator 1 is used as a high-stability reference source, eliminating the energy loss of air damping on the high-frequency vibration of the crystal 20, improving the Q value and enhancing the phase noise suppression ability, and realizing precise control of the temperature in the area where the crystal 20 is located, greatly improving the thermal response speed and temperature control accuracy. Thus, it provides a low-noise reference for the coherent population trapping (CPT) frequency-locking loop; the frequency-locking loop based on all-digital phase-locked loop (ADPLL) technology corrects the oscillator frequency in real time through digital processing algorithms, improving the short-term stability to the order of 10 -11 magnitude; combined with a low-power application-specific integrated circuit (ASIC) chip and a vacuum insulation structure, the power consumption is reduced. Moreover, while maintaining miniaturization and low power consumption, it has better phase noise and stability performance than a traditional temperature-compensated crystal oscillator (TCXO), enabling the atomic clock to meet the requirements for high-precision time and frequency in scenarios such as satellite navigation augmentation, deep space exploration time and frequency reference, and 5G base station synchronization.

[0049] It should be noted that in this text, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including that element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order discussed, but may also include performing functions in a substantially simultaneous manner or in a reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0050] Through the description of the above embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions for causing a terminal (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in various embodiments of the present application.

[0051] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims, and all of them fall within the protection scope of the present application.

Claims

1. A crystal oscillator, characterized in that, It includes an encapsulation cavity, a crystal, a temperature sensor and a cantilever beam assembly. The crystal, the temperature sensor and the cantilever beam assembly are arranged in the accommodation cavity of the encapsulation cavity. The encapsulation cavity is a vacuum encapsulation structure. The crystal and the temperature sensor are arranged on the cantilever beam assembly. The crystal and the temperature sensor are electrically connected to different connection points of the encapsulation cavity through the cantilever beam assembly, and the temperature sensor surrounds the crystal. Wherein, the cantilever beam assembly includes a heating module. When the temperature sensor monitors that the temperature in the area where the crystal is located is lower than a preset temperature threshold, the heating module heats the crystal.

2. The crystal oscillator according to claim 1, wherein, The cantilever beam assembly further includes a cantilever beam bracket and a thin film layer. The cantilever beam bracket is adapted to the accommodation cavity. The thin film layer is arranged on the top surface of the cantilever beam bracket. The heating module is arranged in the interlayer of the thin film layer. The thin film layer is integrated with metal traces. The crystal and the temperature sensor are arranged on the thin film layer, and the crystal and the temperature sensor are electrically connected to different connection points of the encapsulation cavity through the metal traces.

3. The crystal oscillator according to claim 2, wherein The projection of the crystal on the thin film layer is located in the area where the heating module is located.

4. The crystal oscillator according to claim 2, characterized in that, The heating module is a concentric ring structure formed by winding a heating wire.

5. The crystal oscillator according to claim 2, characterized in that, The thin film layer is a polyimide thin film.

6. The crystal oscillator according to claim 1, characterized in that, The temperature sensor is a negative temperature coefficient NTC resistor.

7. The crystal oscillator according to any one of claims 1 to 6, characterized in that, The encapsulation cavity includes a cover plate and a base. The cover plate and the base cooperate to form the accommodation cavity. A sealing coating is arranged at the contact position between the cover plate and the base.

8. The crystal oscillator according to claim 7, wherein An getter is arranged on the side of the cover plate facing the accommodation cavity.

9. The crystal oscillator according to any one of claims 1 to 6, characterized in that The encapsulation cavity is made of a cermet composite material, and the vacuum degree of the encapsulation cavity is less than or equal to 10 -1 Pa.

10. An atomic clock, characterized in that, It includes a crystal oscillator according to any one of claims 1 to 9.

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