Frequency standard equipment with excellent long-term and short-term stability
Through digital loop negative feedback control technology, combined with high-stable constant temperature crystal oscillator and atomic clock, the crystal oscillator frequency is adjusted using a high-precision frequency standard tester and a microcontroller, the problem of analog phase-locked loop bandwidth limitation is solved, and the short-term and long-term stability of frequency standard equipment is achieved, and the debugging process is simple.
Patent Information
- Application Number
- CN202422502010.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-16
- Publication Date
- 2025-08-12
- Estimated Expiration
- 2034-10-16
AI Technical Summary
In the prior art, the bandwidth of the loop filter that simulates a phase-locked loop is difficult to reach extremely narrow, resulting in the short-term stability of the high-stable constant temperature crystal oscillator. At the same time, the debugging process is time-consuming and labor-intensive, and good short-term and long-term stability cannot be achieved.
The digital loop negative feedback control technology is adopted, and the high-precision frequency standard tester and microcontroller are combined with high-stable constant temperature crystal oscillator and atomic clock to achieve frequency locking. The high-precision digital-to-analog converter is used to adjust the crystal oscillator frequency, eliminating the impact of the loop bandwidth of the analog phase-locked loop, and eliminating the debugging of the analog phase-locked loop hardware process.
The high-stable constant temperature crystal oscillator of frequency standard equipment is achieved with excellent short-term stability and excellent long-term stability of atomic clock. At the same time, the debugging process is fast and efficient, avoiding the negative impact of the loop bandwidth of the simulated phase-locked loop on the crystal oscillator stability.
Smart Images
Figure CN223219083U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of frequency standard equipment, in particular to a frequency standard equipment with excellent long-term and short-term stability. Background Art
[0002] High-stability oven-controlled crystal oscillators have good short-term stability, but the crystal oscillator will slowly age over a long period of time, causing the output frequency to drift slowly, deteriorating its long-term stability. Unlike high-stability oven-controlled crystal oscillators, atomic clock frequency standards have good long-term stability characteristics. Combining the stability advantages of the two and complementing their shortcomings can form a frequency standard with excellent short-term and long-term stability.
[0003] Existing technical means usually use an analog phase-locked loop to synchronize the local oscillator and the reference frequency. However, the loop filter bandwidth of the analog phase-locked loop is usually in the kHz range. Due to the size of the components, it is difficult to achieve an extremely narrow loop bandwidth of the order of 0.01 Hz or even narrower. At the same time, when the analog phase-locked loop operates below the narrow loop bandwidth, it is easy to lose lock. Using a voltage-controlled high-stability constant-temperature crystal oscillator as the local oscillator and an atomic clock as the reference, when the high-stability constant-temperature crystal oscillator is locked to the frequency of the atomic clock through an analog phase-locked loop, the short-term stability of the high-stability constant-temperature crystal oscillator will be affected by the loop bandwidth of the analog phase-locked loop, which will eventually deteriorate and fail to fully demonstrate the advantages of the high-stability constant-temperature crystal oscillator's good short-term stability. In addition, in the process of debugging the loop bandwidth of the loop filter, it is necessary to repeatedly solder components, which is time-consuming and labor-intensive, uneconomical, and cannot achieve good performance indicators. Utility Model Content
[0004] (1) Technical issues to be resolved
[0005] The technical problem to be solved by the present invention is to provide a frequency standard adopting digital loop negative feedback control technology in response to the status quo of the existing technology, which locks the voltage-controlled high-stable constant-temperature crystal oscillator to the frequency of the atomic clock, fully combining the stability advantages of the two, and realizing good short-term stability and long-term stability of the frequency standard, thereby achieving a frequency standard device with excellent long-term and short-term stability.
[0006] (2) Technical solution
[0007] The present invention is achieved through the following technical solutions: The present invention proposes a frequency standard device with excellent long-term and short-term stability, including a high-stable constant temperature crystal oscillator, the signal output end of the high-stable constant temperature crystal oscillator is connected to a signal distributor, one signal output end of the signal distributor is connected to a signal output module, the other signal output end of the signal distributor is connected to a high-precision frequency standard tester, the other signal input end of the high-precision frequency standard tester is connected to an atomic clock, the signal output end of the high-precision frequency standard tester is connected to a microcontroller, one signal output end of the microcontroller is connected to a high-precision digital-to-analog converter, the signal input end of the high-precision digital-to-analog converter is connected to a low-noise voltage reference module, and the other signal input end of the high-precision digital-to-analog converter is connected to a computer.
[0008] Furthermore, the signal output terminal of the highly stable constant temperature crystal oscillator is electrically connected to the signal input terminal of the signal distributor, and the signal frequency output by the highly stable constant temperature crystal oscillator is 10 MHz.
[0009] By adopting the above technical solution, the high-stability constant temperature crystal oscillator has good short-term stability.
[0010] Furthermore, the signal output end of the signal distributor is electrically connected to the signal input end of the signal output module, and the other signal output end of the signal distributor is electrically connected to the signal input end of the high-precision frequency standard tester.
[0011] By adopting the above technical solution, the signal distributor is mainly used to divide the signal output by the high-stable constant temperature crystal oscillator into two 10MHz signal outputs, one is output through the signal output module, and the other is transmitted to the high-precision frequency standard tester.
[0012] Furthermore, the signal output terminal of the atomic clock is electrically connected to the corresponding signal input terminal of the high-precision frequency standard tester, and the signal frequency output by the atomic clock is 10 MHz.
[0013] By adopting the above technical solution, the atomic clock is mainly used to output a 10 MHz signal to the high-precision frequency standard tester as a reference signal.
[0014] Furthermore, the signal output terminal of the high-precision frequency standard tester is electrically connected to a signal input terminal of the microcontroller.
[0015] By adopting the above technical solution, a serial communication interface is used between the microcontroller and the high-precision frequency standard tester. The microcontroller parses the data frame sent by the high-precision frequency standard tester into floating-point frequency error data, and calculates the target voltage on the voltage-controlled pin of the voltage-controlled high-stable constant temperature crystal oscillator based on the frequency error data. The microcontroller communicates with the high-precision digital-to-analog converter through the serial communication interface and configures the output voltage control word of the high-precision digital-to-analog converter. When the high-precision digital-to-analog converter does not achieve sufficient resolution, the control process will directly affect the short-term stability of the output signal of the entire device; the microcontroller controls the output voltage of the high-precision digital-to-analog converter at the sampling rate of the high-precision standard tester, and the output voltage is directly fed back to the voltage-controlled pin of the high-stable constant temperature crystal oscillator, thereby changing the output frequency of the high-stable constant temperature crystal oscillator, forming a "sampling"-"calculation"-"control" loop.
[0016] Furthermore, a signal output terminal of the microcontroller is electrically connected to a signal input terminal of the high-precision digital-to-analog converter, and the signal transmission channel between the microcontroller and the computer is a bidirectional transmission channel.
[0017] By adopting the above technical solution, the computer can configure loop control parameters as needed, eliminating the process of debugging analog phase-locked loop hardware.
[0018] Furthermore, the signal input terminal of the high-precision digital-to-analog converter is electrically connected to the signal output terminal of the low-noise voltage reference module.
[0019] By adopting the above technical solution, the high-precision digital-to-analog converter is a high-precision, low-noise digital-to-analog converter with a resolution of 24 bits or more.
[0020] Furthermore, the signal output terminal of the high-precision digital-to-analog converter is electrically connected to the signal input terminal of the high-stability constant-temperature crystal oscillator.
[0021] By adopting the above technical solution, when the frequency error is large, the microcontroller writes the output voltage control word of the high-precision digital-to-analog converter with a larger voltage control step. When the frequency error gradually decreases, the microcontroller synchronously reduces the voltage control step until the high-stable constant temperature crystal oscillator locks to the frequency of the rubidium atomic clock. When the frequency error measured by the high-precision frequency standard tester is less than 5×10 12 or greater than -5×10 12 When the microcontroller determines that the voltage-controlled high-stable constant-temperature crystal oscillator has been locked to the output frequency of the atomic clock, the loop will continue to work even in the locked state, so that the frequency deviation between the two will gradually decrease.
[0022] (3) Beneficial effects
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] To solve this problem, existing technical means usually use an analog phase-locked loop to make the local oscillator and the reference frequency synchronized, but the loop filter bandwidth of the analog phase-locked loop is usually in the KHz range. Due to the size of the components, it is difficult to achieve an extremely narrow loop bandwidth of the order of 0.01 Hz or even narrower. At the same time, when the analog phase-locked loop works below the narrow loop bandwidth, it is easy to lose lock. Using a voltage-controlled high-stability constant-temperature crystal oscillator as the local oscillator and an atomic clock as the reference, when the high-stability constant-temperature crystal oscillator is locked to the frequency of the atomic clock through an analog phase-locked loop, it will be affected by the loop bandwidth of the analog phase-locked loop, and will eventually deteriorate the short-term stability of the high-stability constant-temperature crystal oscillator, and cannot fully reflect the advantage of the good short-term stability of the high-stability constant-temperature crystal oscillator. In addition, in the process of debugging the loop bandwidth of the loop filter, it is necessary to repeatedly solder components, which is time-consuming and labor-intensive, and is neither economical nor effective. In order to solve the problem of good performance indicators, the utility model integrates a high-stable constant temperature crystal oscillator and an atomic clock at the same time, uses a high-precision frequency standard tester to digitize the frequency error between the two, and controls the output voltage of the high-precision digital-to-analog converter through a microcontroller to adjust the output frequency of the high-stable constant temperature crystal oscillator, so as to lock the output frequency to the frequency of the atomic clock. Through the digital loop negative feedback control technology, the problem that it is difficult for analog phase-locked loops to achieve extremely narrow loop bandwidth is effectively solved, and the influence of the loop bandwidth of the analog phase-locked loop on the short-term stability of the high-stable constant temperature crystal oscillator is eliminated, so that the frequency standard has both the excellent short-term stability of the high-stable constant temperature crystal oscillator and the excellent long-term stability of the atomic clock. At the same time, the loop control parameters can be configured as needed through a computer, which saves the process of debugging the analog phase-locked loop hardware and makes the debugging process convenient and fast. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 This is a structural block diagram of a frequency standard device with excellent long-term and short-term stability described in the utility model.
[0026] The following are the descriptions of the reference numerals:
[0027] 1. Atomic clock; 2. Signal distributor; 3. Signal output module; 4. High-stability constant-temperature crystal oscillator; 5. High-precision digital-to-analog converter; 6. Low-noise voltage reference module; 7. Microcontroller; 8. Computer; 9. High-precision frequency standard tester. DETAILED DESCRIPTION
[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0029] like Figure 1As shown, a frequency standard device with excellent long-term and short-term stability in this embodiment includes a high-stable constant temperature crystal oscillator 4, a signal output end of the high-stable constant temperature crystal oscillator 4 is connected to a signal distributor 2, one signal output end of the signal distributor 2 is connected to a signal output module 3, and the other signal output end of the signal distributor 2 is connected to a high-precision frequency standard tester 9. The signal distributor 2 is mainly used to divide the signal output by the high-stable constant temperature crystal oscillator 4 into two 10MHz signal outputs, one of which is output through the signal output module 3 and the other is transmitted to the high-precision frequency standard tester 9. The other signal input port of the high-precision frequency standard tester 9 is connected to an atomic clock 1. The high-precision frequency standard The signal output end of the tester 9 is connected to the microcontroller 7, one signal output end of the microcontroller 7 is connected to the high-precision digital-to-analog converter 5, the signal input end of the high-precision digital-to-analog converter 5 is connected to the low-noise voltage reference module 6, and the other signal input end of the high-precision digital-to-analog converter 5 is connected to the computer 8. When the frequency error is large, the microcontroller 7 writes the output voltage control word of the high-precision digital-to-analog converter 5 with a large voltage control step. When the frequency error gradually decreases, the microcontroller 7 synchronously reduces the voltage control step until the high-stable constant temperature crystal oscillator 4 is locked to the frequency of the rubidium atomic clock 1. When the frequency error measured by the high-precision frequency standard tester 9 is less than 5×10 12 or greater than -5×10 12 When , the microcontroller 7 determines that the voltage-controlled high-stable constant-temperature crystal oscillator 4 has locked on the output frequency of the atomic clock 1. Even in the locked state, the loop will continue to work, so that the frequency deviation between the two will gradually decrease.
[0030] like Figure 1 As shown, in this embodiment, the signal output end of the high-stable constant temperature crystal oscillator 4 is electrically connected to the signal input end of the signal distributor 2, the signal frequency output by the high-stable constant temperature crystal oscillator 4 is 10 MHz, and the high-stable constant temperature crystal oscillator 4 has good short-term stability. The signal output end of the signal distributor 2 is electrically connected to the signal input end of the signal output module 3, and the other signal output end of the signal distributor 2 is electrically connected to the signal input end of the high-precision frequency standard tester 9. The signal output end of the atomic clock 1 is electrically connected to the corresponding signal input end on the high-precision frequency standard tester 9, and the signal frequency output by the atomic clock 1 is 10 MHz. The atomic clock 1 is mainly used to output a 10 MHz signal to the high-precision frequency standard tester 9 as a reference signal.
[0031] like Figure 1As shown, in this embodiment, the signal output terminal of the high-precision frequency standard tester 9 is electrically connected to a signal input terminal of the microcontroller 7. A serial communication interface is used between the microcontroller 7 and the high-precision frequency standard tester 9. The microcontroller 7 parses the data frame sent by the high-precision frequency standard tester 9 into floating-point frequency error data, and calculates the target voltage on the voltage-controlled pin of the voltage-controlled high-stable constant-temperature crystal oscillator 4 based on the frequency error data. The microcontroller 7 communicates with the high-precision digital-to-analog converter 5 through the serial communication interface and configures the output voltage control word of the high-precision digital-to-analog converter 5. When the high-precision digital-to-analog converter 5 does not achieve sufficient resolution, the control process will directly affect the short-term stability of the output signal of the entire device; the microcontroller 7 controls the output voltage of the high-precision digital-to-analog converter 5 at the sampling rate of the high-precision frequency standard tester. The output voltage is directly fed back to the voltage-controlled pin of the high-stable constant-temperature crystal oscillator 4, thereby changing the output frequency of the high-stable constant-temperature crystal oscillator 4, forming a "sampling"-"calculation"-"control" loop.
[0032] like Figure 1 As shown, in this embodiment, a signal output terminal of the microcontroller 7 is electrically connected to the signal input terminal of the high-precision digital-to-analog converter 5. The signal transmission channel between the microcontroller 7 and the computer 8 is a bidirectional input channel. The computer 8 can configure the loop control parameters as needed, eliminating the process of debugging the analog phase-locked loop hardware. The signal input terminal of the high-precision digital-to-analog converter 5 is electrically connected to the signal output terminal of the low-noise voltage reference module 6. The high-precision digital-to-analog converter 5 is a high-precision, low-noise digital-to-analog converter with a resolution of 24 bits or more. The signal output terminal of the high-precision digital-to-analog converter 5 is electrically connected to the signal input terminal of the high-stable constant-temperature crystal oscillator 4.
[0033] The specific implementation process of this embodiment is as follows: the 10MHz sine wave signal of the voltage-controlled high-stable constant-temperature crystal oscillator 4 is divided into two 10MHz signals after passing through the signal distributor 2, one of which is used as the output of the frequency standard, and the other is sent to the high-precision frequency standard tester 9. The high-precision frequency standard tester 9 receives two 10MHz signals, one of which comes from the 10MHz sine wave signal of the atomic clock 1, and the other comes from the signal distributor 2. The high-precision frequency standard tester 9 measures the frequency error between the two. The high-precision frequency standard tester 9 transmits the frequency error measurement result to the microcontroller 7 through the communication interface at a fixed sampling rate. The frequency error is digitized through the high-precision frequency standard tester 9. After obtaining the frequency error results of the two, the microcontroller 7 calculates the voltage amount that needs to be adjusted for the voltage-controlled high-stable constant-temperature crystal oscillator 4, and sends the target voltage value to the high-precision digital-to-analog converter 5 through the communication interface. The low-noise voltage reference module 6 is a high-precision digital-to-analog converter. The device 5 provides a voltage reference, so that the high-precision digital-to-analog converter 5 outputs a controlled low-noise voltage, and the output voltage is connected to the voltage-controlled pin of the voltage-controlled high-stable constant-temperature crystal oscillator 4, thereby adjusting the output frequency of the high-stable constant-temperature crystal oscillator 4. Under normal circumstances, the voltage-controlled high-stable constant-temperature crystal oscillator 4 has a positive slope frequency control curve, that is, when the voltage control voltage is increased, the output frequency also increases accordingly, and vice versa, the output frequency decreases. When the output frequency of the high-stable constant-temperature crystal oscillator 4 is higher than the output frequency of the atomic clock 1, the microcontroller 7 adjusts the output voltage of the high-precision digital-to-analog converter 5 in the negative direction, so that the output frequency of the high-stable constant-temperature crystal oscillator 4 gradually approaches the output frequency of the atomic clock 1. Through repeated loop feedback control adjustments, the output frequency of the high-stable constant-temperature crystal oscillator 4 is finally locked at the output frequency of the atomic clock 1. At the same time, the microcontroller 7 can receive and save instructions from the computer 8 through the communication interface, thereby changing the loop feedback control parameters to achieve the purpose of adjusting the loop control response.
[0034] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A frequency standard device with excellent long-term and short-term stability, characterized by: The invention comprises a high-stable constant temperature crystal oscillator (4), wherein a signal output end of the high-stable constant temperature crystal oscillator (4) is connected to a signal distributor (2), one signal output end of the signal distributor (2) is connected to a signal output module (3), another signal output end of the signal distributor (2) is connected to a high-precision frequency standard tester (9), another signal input port of the high-precision frequency standard tester (9) is connected to an atomic clock (1), the signal output end of the high-precision frequency standard tester (9) is connected to a microcontroller (7), one signal output end of the microcontroller (7) is connected to a high-precision digital-to-analog converter (5), the signal input end of the high-precision digital-to-analog converter (5) is connected to a low-noise voltage reference module (6), and another signal input end of the high-precision digital-to-analog converter (5) is connected to a computer (8).
2. A frequency standard device with excellent long-term and short-term stability according to claim 1, characterized in that: The signal output end of the high-stable constant temperature crystal oscillator (4) is electrically connected to the signal input end of the signal distributor (2), and the signal frequency output by the high-stable constant temperature crystal oscillator (4) is 10 MHz.
3. The frequency standard device with excellent long-term and short-term stability according to claim 2, characterized in that: The signal output end of the signal distributor (2) is electrically connected to the signal input end of the signal output module (3), and the other signal output end of the signal distributor (2) is electrically connected to the signal input end of the high-precision frequency standard tester (9).
4. The frequency standard device with excellent long-term and short-term stability according to claim 2, characterized in that: The signal output end of the atomic clock (1) is electrically connected to the corresponding signal input end of the high-precision frequency standard tester (9), and the signal frequency output by the atomic clock (1) is 10 MHz.
5. The frequency standard device with excellent long-term and short-term stability according to claim 1, characterized in that: The signal output terminal of the high-precision frequency standard tester (9) is electrically connected to a signal input terminal of the microcontroller (7).
6. The frequency standard device with excellent long-term and short-term stability according to claim 1, characterized in that: A signal output terminal of the microcontroller (7) is electrically connected to a signal input terminal of the high-precision digital-to-analog converter (5), and a signal transmission channel between the microcontroller (7) and the computer (8) is a bidirectional transmission channel.
7. The frequency standard device with excellent long-term and short-term stability according to claim 1, characterized in that: The signal input end of the high-precision digital-to-analog converter (5) is electrically connected to the signal output end of the low-noise voltage reference module (6).
8. The frequency standard device with excellent long-term and short-term stability according to claim 1, characterized in that: The signal output end of the high-precision digital-to-analog converter (5) is electrically connected to the signal input end of the high-stability constant-temperature crystal oscillator (4).