Constant-temperature crystal oscillator and rubidium clock combined taming device and method

Abstract

The invention discloses a constant-temperature crystal oscillator and rubidium clock combined taming device and method, and relates to the technical field of time frequency, and the device comprises a single-chip microcomputer, an FPGA module, a TDC module, a rubidium atomic clock and a constant-temperature crystal oscillator. The FPGA module is connected with the single-chip microcomputer, the TDC module, the rubidium atomic clock and the constant-temperature crystal oscillator, the FPGA module is used for receiving a reference 1PPS signal input from the outside, the single-chip microcomputer is connected with the constant-temperature crystal oscillator through the DAC module, the TDC module is connected with the single-chip microcomputer through an SPI bus, the TDC module is used for measuring the phase difference, and the single-chip microcomputer is used for adjusting the voltage control of the constant-temperature crystal oscillator or the frequency of the rubidium atomic clock; and the FPGA module communicates with the rubidium atomic clock through a UART serial port. The output frequency has the characteristics of a constant-temperature crystal oscillator and a rubidium atomic clock at the same time, and low noise and high stability are achieved; a taming state can be quickly entered to output an accurate clock without waiting for preheating of a rubidium clock during startup; a serial taming mode is avoided, parallel taming is adopted, and when one clock source is abnormal, clock hot backup can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of time and frequency technology, and in particular to a combined taming device and method for a constant temperature crystal oscillator and a rubidium clock. Background Art

[0002] At present, the main clock sources for time and frequency equipment in the time and frequency industry are oven-controlled crystal oscillators and rubidium clocks. After being tamed with an external reference, they can output low-noise clock signals and provide high-precision timekeeping when there is no external reference input. To meet the requirements of low noise and high timekeeping accuracy at the same time, the industry generally needs to use oven-controlled crystal oscillators and rubidium atomic clocks. The oven-controlled crystal oscillator meets the low noise requirement, and the rubidium atomic clock meets the high timekeeping accuracy requirement. The existing technology generally uses 1PPS to tame the rubidium atomic clock, and then synchronizes the oven-controlled crystal oscillator to the rubidium atomic clock, and then outputs the oven-controlled crystal oscillator clock to the outside. This method has disadvantages: first, the rubidium atomic clock has a long preheating time, and generally it can only be tamed after half an hour of preheating after power-on; second, the clock taming is in serial mode. If the atomic clock or crystal oscillator has an abnormality, the output clock will also be abnormal and cannot be used as a parameter clock. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a combined taming device and method for an oven controlled crystal oscillator and a rubidium clock.

[0004] The object of the present invention is achieved through the following technical solutions: In a first aspect, the present invention discloses a combined taming device of a constant temperature crystal oscillator and a rubidium clock, comprising a single chip microcomputer, an FPGA module, a TDC module, a rubidium atomic clock and a constant temperature crystal oscillator; The FPGA module is connected to the single-chip microcomputer, the TDC module, the rubidium atomic clock and the oven-controlled crystal oscillator respectively. The FPGA module is used to receive an external reference 1PPS signal. The single-chip microcomputer is connected to the oven-controlled crystal oscillator through the DAC module. The TDC module is connected to the single-chip microcomputer through the SPI bus. The TDC module is used to measure the phase difference. The single-chip microcomputer is used to adjust the voltage control of the oven-controlled crystal oscillator or the frequency of the rubidium atomic clock; The FPGA module communicates with the rubidium atomic clock via a UART serial port.

[0005] Based on the first aspect, the rubidium atomic clock meets the long-term stability requirement: ≤5×10 -12 sky.

[0006] Based on the first aspect, the TDC module uses a time-to-digital converter model MS1050NA, with a measurement range of 0s to 16s and a measurement accuracy of 20ps.

[0007] In a second aspect, the present invention discloses a method for jointly training an oven controlled crystal oscillator and a rubidium clock, comprising the following steps: S1. If the external input reference 1PPS signal is valid, the oven-controlled crystal oscillator and the rubidium atomic clock are tamed and their status is detected. If the status is normal, the oven-controlled crystal oscillator outputs at a frequency of 10 MHz. S2. If the external reference 1PPS signal is lost, the phase difference between the STOP2 and STOP4 pins of the rubidium atomic clock is measured, and the voltage control of the oven-controlled crystal oscillator is adjusted to synchronize the local pulse LOCAL_1PPS signal with the local synchronous RU_1PPS signal, providing high-precision timekeeping. S3. If the rubidium atomic clock is detected to be in an abnormal state, the oven controlled crystal oscillator is tamed separately and the output is maintained; S4. If an abnormality of the constant temperature crystal oscillator is detected, the rubidium atomic clock is tamed separately and switched to the rubidium atomic clock for 10M output.

[0008] Based on the second aspect, the taming of the oven controlled crystal oscillator in step S1 specifically includes: After receiving the reference 1PPS signal from the external input, the FPGA module transmits the reference 1PPS signal to the STOP1 pin and STOP3 pin of the TDC module; The FPGA module uses the 10MHz frequency division of the oven-controlled crystal oscillator to generate the local pulse LOCAL_1PPS signal, and then sends the local pulse LOCAL_1PPS signal to the STOP2 pin of the TDC module; The MCU obtains the phase difference between the STOP1 and STOP2 pins on the TDC module through the SPI bus, adjusts the phase difference, and feeds it back to the FPGA module. Based on the adjusted phase difference, the FPGA module adjusts the delay of the local pulse LOCAL_1PPS signal and the time difference between the reference 1PPS signal within one cycle. The microcontroller obtains the phase difference data of the STOP1 pin and the STOP2 pin on the TDC module after the phase difference is adjusted, and adjusts the constant temperature crystal oscillator voltage control through the DAC module to keep the adjusted local pulse LOCAL_1PPS signal synchronized with the reference 1PPS signal.

[0009] Based on the second aspect, the taming of the rubidium atomic clock in step S1 specifically includes: After receiving the reference 1PPS signal from the external input, the FPGA module transmits the reference 1PPS signal to the STOP1 pin and STOP3 pin of the TDC module; The FPGA module uses the 10MHz frequency division of the rubidium atomic clock to generate the local synchronous RU_1PPS signal, and then sends the local synchronous RU_1PPS signal to the STOP4 pin of the TDC module; The MCU obtains the phase difference between the STOP3 and STOP4 pins on the TDC module through the SPI bus, adjusts the phase difference, and feeds it back to the FPGA module. Based on the adjusted phase difference, the FPGA module adjusts the delay of the local synchronous RU_1PPS signal and the time difference between the reference 1PPS signal within one cycle. The microcontroller obtains the phase difference data of the STOP3 pin and the STOP4 pin on the TDC module after the phase difference is adjusted, and adjusts the frequency of the rubidium atomic clock through the serial port so that the adjusted local synchronous RU_1PPS signal is synchronized with the reference 1PPS signal.

[0010] The beneficial effects of the present invention are: 1) The output frequency of the present invention has the characteristics of both a constant temperature crystal oscillator and a rubidium atomic clock, and has low noise and high stability.

[0011] 2) The present invention can quickly enter the taming state and output an accurate clock without waiting for the rubidium clock to warm up when it is turned on.

[0012] 3) The present invention avoids the serial training mode and adopts parallel training, which can achieve clock hot backup when one of the clock sources is abnormal. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the circuit structure of a combined oven-controlled crystal oscillator and rubidium clock taming device according to an embodiment of the present invention; Figure 2 A schematic diagram of adjusting the delay according to the phase difference of the tamed oven controlled crystal oscillator FPGA module according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the time delay after the ARM in an embodiment of the present invention is tamed by the constant temperature crystal oscillator through voltage control; Figure 4 This is a schematic diagram of adjusting the delay of the disciplined rubidium atomic clock FPGA module according to the phase difference according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the time delay after the ARM in an embodiment of the present invention tames the rubidium atomic clock through the serial port; Figure 6 This is a schematic diagram of synchronizing a local pulse LOCAL_1PPS signal to a local synchronization RU_1PPS signal according to an embodiment of the present invention. DETAILED DESCRIPTION

[0014] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0015] The present application provides a device and method for jointly training an oven-controlled crystal oscillator and a rubidium clock, with the purpose of providing a technology for jointly training an oven-controlled crystal oscillator and a rubidium atomic clock. The oven-controlled crystal oscillator and the rubidium atomic clock can be trained simultaneously through an external reference. When the rubidium atomic clock is preheated, the oven-controlled crystal oscillator can be trained separately. With respect to the external space-time reference time difference, the rubidium atomic clock can be trained synchronously after the preheating is completed. When the external reference is lost, the oven-controlled crystal oscillator can be switched to synchronize with the rubidium atomic clock to provide high-precision timekeeping. When the oven-controlled crystal oscillator or the rubidium atomic clock fails, the remaining normal clock source can be trained separately and output independently to achieve reference redundancy.

[0016] For example, the combined taming device of constant temperature crystal oscillator and rubidium clock of the present invention adopts a circuit structure of single chip microcomputer, FPGA module, TDC module, rubidium atomic clock and constant temperature crystal oscillator, and its structural diagram is shown as follows: Figure 1 As shown, the oven-controlled crystal oscillator and rubidium atomic clock are tamed by externally inputting a reference 1PPS signal. The FPGA module is connected to the single-chip microcomputer, the TDC module, the rubidium atomic clock, and the oven-controlled crystal oscillator respectively. The FPGA module is used to receive the external input reference 1PPS signal. The single-chip microcomputer is connected to the oven-controlled crystal oscillator via the DAC module. The TDC module is connected to the single-chip microcomputer via the SPI bus. The TDC module is used to measure the phase difference. The single-chip microcomputer is used to adjust the voltage control of the oven-controlled crystal oscillator or the frequency of the rubidium atomic clock. The FPGA module communicates with the rubidium atomic clock via the UART serial port. The model of the rubidium atomic clock is selected according to the long-term stability requirements, such as the long-term stability requirement: ≤5×10 -12 The rubidium clock can be a rubidium atomic clock with serial communication; the oven-controlled crystal oscillator is selected according to the requirements of phase noise and short-term stability. In this embodiment, an oven-controlled crystal oscillator with a voltage-controlled pin is selected; the FPGA resource requirements are not high, and a mainstream low-cost chip is selected; the MCU can select the mainstream STM32F407 series microcontroller or other similar models; the TDC module uses the Hangzhou Ruimeng MS1050NA time-to-digital converter with a measurement range of 0s~16s and a measurement accuracy of 20ps.

[0017] Exemplarily, the present invention further discloses a method for jointly training an oven controlled crystal oscillator and a rubidium clock, comprising the following steps: S1. If the external input reference 1PPS signal is valid, the oven-controlled crystal oscillator and the rubidium atomic clock are tamed and their status is detected. If the status is normal, the oven-controlled crystal oscillator outputs at a frequency of 10 MHz. S2. If the external input reference 1PPS signal is lost, the phase difference between the STOP2 pin and the STOP4 pin of the rubidium atomic clock is measured, and the voltage control of the constant temperature crystal oscillator is adjusted to synchronize the local pulse LOCAL_1PPS signal to the local synchronous RU_1PPS signal, providing high-precision timekeeping. The schematic diagram of synchronizing the local pulse LOCAL_1PPS signal to the local synchronous RU_1PPS signal is shown in the figure. Figure 6 As shown; S3. If the rubidium atomic clock is detected to be in an abnormal state, the oven controlled crystal oscillator is tamed separately and the output is maintained; S4. If an abnormality of the constant temperature crystal oscillator is detected, the rubidium atomic clock is tamed separately and switched to the rubidium atomic clock for 10M output.

[0018] Specifically, the taming of the oven controlled crystal oscillator described in step S1 specifically includes: After receiving the reference 1PPS signal from the external input, the FPGA module transmits the reference 1PPS signal to the STOP1 pin and STOP3 pin of the TDC module; The FPGA module uses the 10MHz frequency division of the oven-controlled crystal oscillator to generate the local pulse LOCAL_1PPS signal, and then sends the local pulse LOCAL_1PPS signal to the STOP2 pin of the TDC module; The MCU obtains the phase difference between the STOP1 pin and the STOP2 pin on the TDC module through the SPI bus, adjusts the phase difference and feeds it back to the FPGA module. Based on the adjusted phase difference, the FPGA module adjusts the time delay of the local pulse LOCAL_1PPS signal and the time difference of the reference 1PPS signal within one cycle; the schematic diagram of the taming constant temperature crystal oscillator FPGA module adjusting the delay according to the phase difference is shown in the figure below. Figure 2 As shown; The MCU obtains the phase difference data of the STOP1 and STOP2 pins on the TDC module after adjusting the phase difference, and adjusts the voltage control of the constant temperature crystal oscillator through the DAC module to synchronize the adjusted local pulse LOCAL_1PPS signal with the reference 1PPS signal. The schematic diagram of the delay after ARM tames the constant temperature crystal oscillator through voltage control is shown as follows: Figure 3 shown.

[0019] Specifically, the taming of the rubidium atomic clock in step S1 includes: After receiving the reference 1PPS signal from the external input, the FPGA module transmits the reference 1PPS signal to the STOP1 pin and STOP3 pin of the TDC module; The FPGA module uses the 10MHz frequency division of the rubidium atomic clock to generate the local synchronous RU_1PPS signal, and then sends the local synchronous RU_1PPS signal to the STOP4 pin of the TDC module; The microcontroller obtains the phase difference between the STOP3 pin and the STOP4 pin on the TDC module through the SPI bus, adjusts the phase difference and feeds it back to the FPGA module. Based on the adjusted phase difference, the FPGA module adjusts the time delay of the local synchronous RU_1PPS signal and the time difference of the reference 1PPS signal within one cycle; the schematic diagram of the tamed rubidium atomic clock FPGA module adjusting the delay according to the phase difference is shown in the figure. Figure 4 shown The MCU obtains the phase difference data of the STOP3 and STOP4 pins on the TDC module after adjusting the phase difference, and adjusts the frequency of the rubidium atomic clock through the serial port so that the adjusted local synchronous RU_1PPS signal is synchronized with the reference 1PPS signal. The schematic diagram of the delay after ARM tames the rubidium atomic clock through the serial port is shown as follows: Figure 5 shown.

[0020] In summary, the present application provides a combined training device and method for a constant temperature crystal oscillator and a rubidium clock, which have the characteristics of a constant temperature crystal oscillator and a rubidium atomic clock in terms of output frequency, with low noise and high stability; there is no need to wait for the rubidium clock to warm up when the power is turned on, and the device can quickly enter the training state to output an accurate clock; it avoids the serial training mode and adopts parallel training, so that when one of the clock sources is abnormal, the clock can be hot-backed up.

[0021] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A combined taming device for a constant temperature crystal oscillator and a rubidium clock, characterized in that: Including single chip microcomputer, FPGA module, TDC module, rubidium atomic clock and constant temperature crystal oscillator; The FPGA module is connected to the single-chip microcomputer, the TDC module, the rubidium atomic clock and the oven-controlled crystal oscillator respectively. The FPGA module is used to receive an external reference 1PPS signal. The single-chip microcomputer is connected to the oven-controlled crystal oscillator through the DAC module. The TDC module is connected to the single-chip microcomputer through the SPI bus. The TDC module is used to measure the phase difference. The single-chip microcomputer is used to adjust the voltage control of the oven-controlled crystal oscillator or the frequency of the rubidium atomic clock; The FPGA module communicates with the rubidium atomic clock via a UART serial port.

2. The combined taming device of an oven controlled crystal oscillator and a rubidium clock according to claim 1, characterized in that: The rubidium atomic clock meets the long-term stability requirement: ≤5×10 -12 sky.

3. The combined taming device of a constant temperature crystal oscillator and a rubidium clock according to claim 1, characterized in that: The TDC module uses a time-to-digital converter model MS1050NA, with a measurement range of 0s to 16s and a measurement accuracy of 20ps.

4. A combined training method of a constant temperature crystal oscillator and a rubidium clock, characterized in that: The following steps are involved: S1. If the external input reference 1PPS signal is valid, the oven-controlled crystal oscillator and the rubidium atomic clock are tamed and their status is detected. If the status is normal, the oven-controlled crystal oscillator outputs at a frequency of 10 MHz. S2. If the external reference 1PPS signal is lost, the phase difference between the STOP2 and STOP4 pins of the rubidium atomic clock is measured, and the voltage control of the oven-controlled crystal oscillator is adjusted to synchronize the local pulse LOCAL_1PPS signal with the local synchronous RU_1PPS signal, providing high-precision timekeeping. S3. If the rubidium atomic clock is detected to be in an abnormal state, the oven controlled crystal oscillator is tamed separately and the output is maintained; S4. If an abnormality of the constant temperature crystal oscillator is detected, the rubidium atomic clock is tamed separately and switched to the rubidium atomic clock for 10M output.

5. The combined training method of a constant temperature crystal oscillator and a rubidium clock according to claim 4, characterized in that: The taming of the oven controlled crystal oscillator described in step S1 specifically includes: After receiving the reference 1PPS signal from the external input, the FPGA module transmits the reference 1PPS signal to the STOP1 pin and STOP3 pin of the TDC module; The FPGA module uses the 10MHz frequency division of the oven-controlled crystal oscillator to generate the local pulse LOCAL_1PPS signal, and then sends the local pulse LOCAL_1PPS signal to the STOP2 pin of the TDC module; The MCU obtains the phase difference between the STOP1 and STOP2 pins on the TDC module through the SPI bus, adjusts the phase difference, and feeds it back to the FPGA module. Based on the adjusted phase difference, the FPGA module adjusts the delay of the local pulse LOCAL_1PPS signal and the time difference between the reference 1PPS signal within one cycle. The microcontroller obtains the phase difference data of the STOP1 pin and the STOP2 pin on the TDC module after the phase difference is adjusted, and adjusts the constant temperature crystal oscillator voltage control through the DAC module to keep the adjusted local pulse LOCAL_1PPS signal synchronized with the reference 1PPS signal.

6. The combined training method of a constant temperature crystal oscillator and a rubidium clock according to claim 4, characterized in that: The taming of the rubidium atomic clock in step S1 specifically includes: After receiving the reference 1PPS signal from the external input, the FPGA module transmits the reference 1PPS signal to the STOP1 pin and STOP3 pin of the TDC module; The FPGA module uses the 10MHz frequency division of the rubidium atomic clock to generate the local synchronous RU_1PPS signal, and then sends the local synchronous RU_1PPS signal to the STOP4 pin of the TDC module; The MCU obtains the phase difference between the STOP3 and STOP4 pins on the TDC module through the SPI bus, adjusts the phase difference, and feeds it back to the FPGA module. Based on the adjusted phase difference, the FPGA module adjusts the delay of the local synchronous RU_1PPS signal and the time difference between the reference 1PPS signal within one cycle. The microcontroller obtains the phase difference data of the STOP3 pin and the STOP4 pin on the TDC module after the phase difference is adjusted, and adjusts the frequency of the rubidium atomic clock through the serial port so that the adjusted local synchronous RU_1PPS signal is synchronized with the reference 1PPS signal.

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