CN103293376B - A kind of measuring method of frequency stability and device - Google Patents

Abstract

The invention discloses a kind of frequency stability measurement method and apparatus, belong to electronic technology field.Described method comprises carries out frequency inverted to the output signal in measured signal source, obtains first frequency signal; With the first reference signal for reference signal, and set multiple as Measurement bandwidth with first frequency signal frequency, measure the frequency of first frequency signal; Adopt the frequency of first frequency signal, according to the short-term frequency stability in first variance formulae discovery measured signal source; Frequency inverted is carried out to the output signal in measured signal source, obtains second frequency signal; With the second reference signal for reference signal, measure the frequency of second frequency signal; Adopt the frequency of second frequency signal, according to the long-term stability in second variance formulae discovery measured signal source.The present invention, by when measuring short-term frequency stability, controls the Measurement bandwidth of count measurement, improves the accuracy measuring short-term frequency stability.

Description

A method and device for measuring frequency stability

technical field

The invention relates to the field of electronic technology, in particular to a method and device for measuring frequency stability.

Background technique

With the rapid development of modern society, the application of high-precision time-frequency technology is becoming more and more extensive, and people's requirements for the stability of the time-frequency output of the clock source are also getting higher and higher. Usually, the stability of a clock source is measured by frequency stability.

There is a measurement method for measuring frequency stability. The method includes: performing frequency division processing on the output signal of the signal source under test; Count the number of pulses; calculate the frequency of the signal under test according to the number of pulses; calculate the frequency stability of the signal source under test according to the frequency of the output signal of the signal source under test and the standard formula of frequency stability.

In the process of realizing the present invention, the inventor finds that there are at least the following problems in the prior art:

In the prior art, the standard variance formula is usually used to calculate the frequency stability of the signal source. However, it is found through research that a signal source usually has two stability indicators, which are short-term frequency stability and long-term frequency stability respectively. Frequency stability, wherein, the short-term frequency stability characterizes the jitter level of the signal, and the long-term frequency stability characterizes the drift degree of the signal frequency over time. Therefore, a single frequency stability is used to measure the frequency of a signal source in the prior art. performance is not accurate enough.

Contents of the invention

In order to solve the problem in the prior art that the single frequency stability is not accurate enough to measure the performance of a signal source, the embodiments of the present invention provide a frequency stability measurement method and device. Described technical scheme is as follows:

On the one hand, an embodiment of the present invention provides a method for measuring frequency stability, the method comprising:

performing frequency conversion on the output signal of the signal source under test to obtain a first frequency signal;

Using the first reference signal as a reference signal and using a set multiple of the frequency of the first frequency signal as a measurement bandwidth, measure the frequency of the first frequency signal;

Using the frequency of the first frequency signal, determine the short-term frequency stability of the measured signal source according to the first variance formula;

performing frequency conversion on the output signal of the signal source under test to obtain a second frequency signal;

Using the second reference signal as a reference signal, measuring the frequency of the second frequency signal;

Using the frequency of the second frequency signal, determine the long-term frequency stability of the measured signal source according to the second variance formula;

The measuring the frequency of the first frequency signal by using the first reference signal as a reference signal and using a set multiple of the frequency of the first frequency signal as a measurement bandwidth includes:

performing low-pass filtering on the first frequency signal, and the filtering bandwidth is the measurement bandwidth;

Taking the first reference signal as the time base signal, measuring the number of pulses of the first frequency signal filtered within a given time;

Calculate the frequency of the first frequency signal according to the following formula:

F=1/(T/N);

Wherein, F is the frequency of the first frequency signal, T is the given time, and N is the measured pulse number of the first frequency signal after filtering;

The measuring the frequency of the second frequency signal by using the second reference signal as a reference signal includes:

collecting the instantaneous phase difference between the second frequency signal and the second reference signal, and obtaining a digital signal representing the change of the phase difference;

Integrating the digital signal to obtain a DC voltage signal;

performing analog-to-digital conversion on the DC voltage signal to obtain a phase difference between the second frequency signal and the second reference signal;

Determine the frequency of the second frequency signal according to the phase difference and the second reference signal.

Optionally, the set multiple is 1-5 times.

Preferably, the first variance formula is Allan variance formula, and the second variance formula is Hadamard variance formula.

On the other hand, an embodiment of the present invention provides a frequency stability measuring device, the device comprising:

A first frequency conversion module for performing frequency conversion on an output signal of a signal source under test to obtain a first frequency signal;

A second frequency conversion module for performing frequency conversion on the output signal of the signal source under test to obtain a second frequency signal;

A first measurement module for measuring the frequency of the first frequency signal obtained by the first frequency conversion module with the first reference signal as the reference signal and the set multiple of the frequency of the first frequency signal as the measurement bandwidth;

a second measurement module for measuring the frequency of the second frequency signal obtained by the second frequency conversion module using the second reference signal as a reference signal; and

The frequency of the first frequency signal measured by the first measurement module is used to determine the short-term frequency stability of the measured signal source according to the first variance formula, and the frequency of the first frequency signal measured by the second measurement module is used to determine the short-term frequency stability of the signal source under test. The frequency of the second frequency signal is a processing module for determining the long-term frequency stability of the measured signal source according to the second variance formula;

The first frequency conversion module is electrically connected to the first measurement module and the processing module respectively, the second frequency conversion module is electrically connected to the second measurement module and the processing module respectively, and the processing module respectively electrically connected to the first measurement module and the second measurement module;

The first measurement module is used for,

performing low-pass filtering on the first frequency signal, and the filtering bandwidth is the measurement bandwidth;

Taking the first reference signal as the time base signal, measuring the number of pulses of the first frequency signal filtered within a given time;

Calculate the frequency of the first frequency signal according to the following formula:

F=1/(T/N);

Wherein, F is the frequency of the first frequency signal, T is the given time, and N is the measured pulse number of the first frequency signal after filtering;

The second measurement module includes:

a phase difference acquisition unit for acquiring the instantaneous phase difference between the second frequency signal and the second reference signal;

An integrating circuit for integrating a digital signal to obtain a DC voltage signal, the digital signal is obtained by the processing module according to the instantaneous phase difference between the second frequency signal and the second reference signal;

An analog-to-digital conversion unit for performing analog-to-digital conversion on the DC voltage signal to obtain a phase difference between the second frequency signal and the second reference signal;

Correspondingly, the processing module is used for,

The frequency of the second frequency signal is determined according to the phase difference obtained by the analog-to-digital conversion unit and the second reference signal.

Optionally, the set multiple is 1-5 times.

Optionally, the first frequency conversion module and the second frequency conversion module are the same module.

Optionally, the apparatus further includes a first signal source for providing the first reference signal and a second signal source for providing the second reference signal, the first signal source is respectively connected to the first A frequency conversion module and the first measurement module are electrically connected, and the first signal source is a crystal oscillator; the second signal source is electrically connected to the second frequency conversion module and the second measurement module respectively, and the second The signal source is an atomic clock.

Preferably, the first variance formula is Allan variance formula, and the second variance formula is Hadamard variance formula.

The beneficial effects brought by the technical solution provided by the embodiments of the present invention are:

By measuring the short-term frequency stability and long-term frequency stability of the signal source under test respectively, two frequency stability measures are used to measure the performance of a signal source, and the accuracy is high.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

FIG. 1 is a flow chart of a method for measuring frequency stability provided by Embodiment 1 of the present invention;

FIG. 2 is a flow chart of performing frequency conversion on a signal under test provided by Embodiment 1 of the present invention;

FIG. 3 is a flow chart of phase comparison between a second frequency signal and a third reference signal according to Embodiment 1 of the present invention;

FIG. 4 is a relationship diagram between measurement bandwidth and frequency stability provided by an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a frequency stability measuring device provided in Embodiment 2 of the present invention;

FIG. 6 is a schematic structural diagram of a frequency conversion module provided by Embodiment 2 of the present invention;

FIG. 7 is a schematic structural diagram of a phase comparison module provided by Embodiment 2 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Embodiment one

An embodiment of the present invention provides a method for measuring frequency stability, see FIG. 1, the method includes:

Step 101: Perform frequency conversion on the output signal of the signal source under test to obtain a first frequency signal.

Through frequency conversion, the output signal of the signal source under test can be converted into a low-frequency signal, which is convenient for measurement. At the same time, the frequency range of the signal source under test applicable to the embodiment of the present invention is wider.

In this step 101, when performing frequency conversion on the output signal of the signal source under test, the output signal of a clock source (such as a voltage-controlled crystal oscillator) with high short-term frequency stability (such as the first reference signal) as the time base signal, and an output signal (such as the second reference signal in the embodiment of the present invention) of a clock source with high long-term frequency stability (such as an atomic clock) may also be used as the time base signal.

Specifically, referring to FIG. 2, this step 101 may include:

Step 1011: Using the first reference signal or the second reference signal as a time base signal, count and measure the output signal of the signal source under test to obtain the frequency of the output signal of the signal source under test.

More specifically, this step 1011 includes:

Take the first reference signal or the second reference signal as the time base signal, measure the pulse number of the output signal of the signal source under test within a given time, and calculate the frequency of the signal under test according to the following formula (1):

F=1/(T/N)(1);

Wherein, F is the frequency of the output signal of the signal source under test, T is a given time, and N is the measured pulse number of the output signal of the signal source under test.

Step 1012: Generate a third frequency signal according to the frequency of the output signal of the signal source under test, where the frequency of the third frequency signal is an integer frequency closest to the frequency of the output signal of the signal source under test.

In this embodiment, the integer frequency may be in MHz (megahertz).

Step 1013: Perform frequency multiplication on the third frequency signal to obtain the first frequency signal.

Step 102: Using the first reference signal as a reference signal and using a set multiple of the frequency of the first frequency signal as a measurement bandwidth, measure the frequency of the first frequency signal.

Wherein, the measurement bandwidth is the frequency range of the first frequency signal that can be measured, and the measurement bandwidth is the set multiple of the first frequency signal frequency, which means that only the signals within the set multiple range of the first frequency signal frequency are measured, such as measuring If the equipment multiple of the bandwidth is 5, only the fifth harmonic of the first frequency signal is measured at most, which is equivalent to filtering out the part of the first frequency signal whose frequency is greater than the fifth harmonic, improving the accuracy of the measurement .

Specifically, the range of setting the multiple may be 1-5 times.

Preferably, the range of setting the multiple is generally 1 time, 2.5 times or 5 times. For example, if the frequency of the first frequency signal is 1KHz (kilohertz), the measurement bandwidth can be 1KHz, 2.5KHz or 5KHz.

Specifically, this step 102 may include: performing low-pass filtering on the first signal, and the filtering bandwidth is the measurement bandwidth; taking the first reference signal as the time base signal, measuring the output signal of the signal source under test within a given time Pulse number, and calculate the frequency of the signal under test according to the formula (1).

Step 103: Using the frequency of the first frequency signal, calculate the short-term frequency stability of the signal source under test according to the first variance formula.

Optionally, the first variance formula can be the Allan variance formula, and the Allen variance formula (2) is as follows:

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, σ _y is the Allan variance value, τ is the sampling period and sampling time, f _h is the high cut-off frequency of the signal source, N is the number of samples, y is the relative frequency deviation of the output frequency at each sampling time, f0 is the frequency of the reference signal, and f _i is the frequency of the output signal of the measured signal source.

Step 104: Perform frequency conversion on the output signal of the signal source under test to obtain a second frequency signal.

In this step 104, when performing frequency conversion on the output signal of the signal source under test, the output signal of a clock source (such as a voltage-controlled crystal oscillator) with high short-term frequency stability (such as the first reference signal) as the time base signal, and an output signal (such as the second reference signal in the embodiment of the present invention) of a clock source with high long-term frequency stability (such as an atomic clock) may also be used as the time base signal.

Specifically, this step 104 may include: taking the first reference signal or the second reference signal as the time base signal, counting and measuring the output signal of the signal source under test to obtain the frequency of the output signal of the signal source under test; The frequency of the output signal of the source generates a fourth frequency signal, and the frequency of the fourth frequency signal is the closest integer frequency to the frequency of the output signal of the measured signal source; the fourth frequency signal is multiplied to generate a second frequency signal .

Step 105: Using the second reference signal as a reference signal, measure the frequency of the second frequency signal.

Specifically, referring to Fig. 3, this step 105 includes:

Step 1051: collect the instantaneous phase difference between the second frequency signal and the third reference signal, and obtain a digital signal representing the change of the phase difference.

Preferably, the acquisition of the instantaneous phase difference between the second frequency signal and the third reference signal can be triggered by a rising edge of the signal.

Optionally, the digital signal is a digital square wave signal representing a phase difference change between the second frequency signal and the third reference signal.

Step 1052: Integrate the digital signal to obtain a DC voltage signal.

Step 1053: Perform analog-to-digital conversion on the DC voltage signal to obtain the phase difference between the second frequency signal and the third reference signal.

Step 1054: Obtain the frequency of the second frequency signal according to the phase difference and the third reference signal.

Step 106: Using the frequency of the second frequency signal, calculate the long-term stability of the signal source under test according to the second variance formula.

Specifically, the second variance formula can be the Allan variance formula, or the Hadamard variance formula; preferably the Hadamard variance formula, and the Hadamard variance formula (3) is as follows:

$\mathrm{<span\; class="notranslate">\; h</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Among them, Hσ _y is the Hadamard variance value, τ is the sampling time, m is the number of samples, and y _k is the relative frequency deviation of the output frequency.

In the Hadamard variance formula (3), y _k+2 -2*y _k+1 +y _k ＝(y _k+2 -y _k+1 )-(y _k+1 -y _k ), due to the previous bracket (y _k+2 -y _k+1 ) contains the influence of frequency drift on frequency stability, and the latter bracket (y _k+1 -y _k ) also contains the influence of frequency drift, so the former bracket and the latter A bracket subtraction can eliminate the influence of frequency drift on frequency stability.

The following is a brief introduction to the relationship between measurement bandwidth and frequency stability in conjunction with Figure 4. As shown in Figure 4, the vertical axis represents the stability, and the horizontal axis represents the sampling time. The three curves in the figure are respectively in different measurement bandwidths. The frequency stability measured below. It can be seen from Figure 1 that when the sampling time is less than 1s, the frequency stability is related to the measurement bandwidth, and when the sampling time is greater than 1s, the frequency stability is basically independent of the measurement bandwidth. Since the time used for short-term frequency stability measurement is generally less than 1s, and the time used for long-term frequency stability measurement is generally greater than 1s, the embodiment of the present invention performs bandwidth control when performing short-term frequency stability measurement, so the measured The frequency stability accuracy is high.

In the embodiment of the present invention, the short-term frequency stability and the long-term frequency stability of the signal source under test are respectively measured, and the two frequency stability are used to measure the performance of a signal source with high accuracy. Moreover, when measuring the short-term frequency stability, the measurement bandwidth is controlled, and the relationship between the short-term frequency stability and the measurement bandwidth is considered, which improves the accuracy of measuring the short-term frequency stability.

Embodiment two

The embodiment of the present invention provides a frequency stability measurement device, referring to Fig. 5, the device includes a first frequency conversion module 1, a second frequency conversion module 2, a first measurement module 3, a second measurement module 4, and a processing Module 5. The first frequency converting module 1 is used for frequency converting the output signal of the signal source under test to obtain a first frequency signal. The second frequency converting module 2 is used for frequency converting the output signal of the signal source under test to obtain a second frequency signal. The first measurement module 3 is used to measure the frequency of the first frequency signal obtained by the first frequency conversion module 1 by using the first reference signal as a reference signal and using a set multiple of the frequency of the first frequency signal as a measurement bandwidth. The second measurement module 4 is used for measuring the frequency of the second frequency signal obtained by the second frequency conversion module 2 by using the second frequency signal as a reference signal. The processing module 5 is used to adopt the frequency of the first frequency signal measured by the first measurement module 3, determine the short-term frequency stability of the measured signal source according to the first variance formula, and adopt the second frequency signal measured by the second measurement module According to the second variance formula, determine the long-term frequency stability of the signal source under test.

Wherein, the first frequency conversion module 1 is electrically connected with the first measurement module 3 and the processing module 5 respectively, the second frequency conversion module 2 is electrically connected with the second measurement module 4 and the processing module 5 respectively, and the processing module 5 is respectively connected with the first measurement module The module 3 and the second measurement module 4 are electrically connected.

Optionally, the setting multiple can be 1-5 times.

Optionally, the first frequency conversion module 1 and the second frequency conversion module 2 may be the same module.

Optionally, the device may further include a first signal source for providing a first reference signal, and the first signal source is electrically connected to the first frequency conversion module 1 and the first measurement module 3 respectively.

Specifically, the first signal source may be a crystal oscillator.

Optionally, the device may further include a second signal source for providing a second reference signal, and the second signal source is electrically connected to the second frequency conversion module 2 and the second measurement module 4 respectively.

Specifically, the second signal source may be an atomic clock, such as a hydrogen atomic clock, a rubidium atomic clock or a cesium atomic clock.

Preferably, the device may further include a DDS (Direct Digital Synthesizer, Direct Digital Synthesizer) for frequency dividing the second reference signal to obtain the third reference signal.

Specifically, the processing module 5 may include a central processing unit, a single-chip microcomputer, a microcontroller or a microprocessor.

Specifically, referring to FIG. 6 , the first frequency conversion module 1 includes a travel time counting unit 11 , a DDS12 and a PLL (PhaseLockedLoop, phase-locked loop) 13 . The travel time counting unit 11 is used for counting and measuring the output signal of the signal source under test by using the first reference signal or the second reference signal as a reference signal to obtain the frequency of the output signal of the signal source under test. The DDS 12 is used to generate a third frequency signal under the control of the control module 5 . The frequency of the third frequency signal is an integer frequency closest to the frequency of the output signal of the measured signal source obtained by the travel time counting unit 11 . The PLL13 is used for multiplying the third frequency signal generated by the DDS12 to generate the first frequency signal. The travel time counting unit 11 is electrically connected to the DDS 12 through the processing module 5 . The PLL13 is electrically connected to the DDS12 and the processing module 5 respectively.

More specifically, the frequency of the frequency signal obtained by the DDS12 and the multiplication ratio of the PLL13 are controlled by the processing module 5 . The processing module 5 can rewrite the internal frequency register of the DDS12 by sending the command control word to the DDS12, so that the DDS12 output frequency is the frequency signal of the closest integer to the measured signal frequency obtained by the travel time counting unit 11, and the command control word is the frequency signal of the processing module 5 It is obtained according to the frequency of the signal under test obtained by the travel time counting unit 11. It is 11.0592MHz to obtain the frequency of the measured signal as the travel time counting unit 11, and the processing module 5 obtains the integer closest to the frequency as 11MHz according to the frequency, and the processing module 5 sends the command control word corresponding to 11MHz to the DDS12, rewriting the inside of the DDS12 The frequency register makes the DDS12 output a frequency signal with a frequency of 11MHz. According to the frequency multiplication ratio of the processing module 5 , the PLL 13 multiplies the frequency signal of 11 MHz to obtain a frequency signal of a desired frequency, such as a frequency signal of 1 KHz.

Correspondingly, the first frequency conversion module 2 includes a travel time counting unit 21 , a DDS22 and a PLL23 . The travel time counting unit 21 is used for counting and measuring the output signal of the signal source under test by using the first reference signal or the second reference signal as a reference signal to obtain the frequency of the output signal of the signal source under test. The DDS22 is used to generate a fourth frequency signal under the control of the control module 5 , the frequency of the fourth frequency signal is the closest integer frequency to the frequency of the output signal of the measured signal source measured by the travel time counting unit 21 . The PLL23 is used for multiplying the fourth frequency signal generated by the DDS22 to generate a second frequency signal. The travel time counting unit 21 is electrically connected to the DDS 22 through the processing module 5 . The PLL23 is electrically connected to the DDS22 and the processing module 5 respectively.

Specifically, referring to FIG. 7 , the second measurement module 4 includes a phase difference acquisition unit 41 , an integration circuit 42 and an analog-to-digital conversion unit 43 . The phase difference acquisition unit 41 is used to acquire the phase difference acquisition unit 41 of the instantaneous phase difference of the second frequency signal and the third reference signal, is used to integrate the digital signal, obtains the integration circuit 42 of the DC voltage signal, and is used to integrate The DC voltage signal obtained by the circuit 42 is analog-to-digital converted, and the analog-to-digital conversion unit 43 obtains the phase difference between the second frequency signal and the third reference signal. The phase acquisition unit 41 is electrically connected to the second frequency conversion module 2 . The phase acquisition unit 41 is electrically connected to the integration circuit 42 through the processing module 5 . The integration circuit 42 is electrically connected to the analog-to-digital conversion unit 43 . The analog-to-digital conversion unit 43 is electrically connected to the processing module 5 .

Wherein, the digital signal is obtained by the processing module 5 according to the instantaneous phase difference between the second frequency signal and the third reference signal.

Correspondingly, the processing module 5 is configured to determine the frequency of the second frequency signal according to the phase difference obtained by the analog-to-digital conversion unit 3 and the third reference signal.

In the embodiment of the present invention, the short-term frequency stability and the long-term frequency stability of the signal source under test are respectively measured, and the two frequency stability are used to measure the performance of a signal source with high accuracy. Moreover, when measuring the short-term frequency stability, the measurement bandwidth is controlled, and the relationship between the short-term frequency stability and the measurement bandwidth is considered, which improves the accuracy of measuring the short-term frequency stability.

The serial numbers of the above embodiments of the present invention are for description only, and do not represent the advantages and disadvantages of the embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (8)

1. A method for measuring frequency stability, characterized in that the method comprises: performing frequency conversion on the output signal of the signal source under test to obtain a first frequency signal; Using the first reference signal as a reference signal and using a set multiple of the frequency of the first frequency signal as a measurement bandwidth, measure the frequency of the first frequency signal; Using the frequency of the first frequency signal, determine the short-term frequency stability of the measured signal source according to the first variance formula; performing frequency conversion on the output signal of the signal source under test to obtain a second frequency signal; Using the second reference signal as a reference signal, measuring the frequency of the second frequency signal; Using the frequency of the second frequency signal, determine the long-term frequency stability of the measured signal source according to the second variance formula; The measuring the frequency of the first frequency signal by using the first reference signal as a reference signal and using a set multiple of the frequency of the first frequency signal as a measurement bandwidth includes: performing low-pass filtering on the first frequency signal, and the filtering bandwidth is the measurement bandwidth; Taking the first reference signal as the time base signal, measuring the number of pulses of the first frequency signal filtered within a given time; Calculate the frequency of the first frequency signal according to the following formula: F=1/(T/N); Wherein, F is the frequency of the first frequency signal, T is the given time, and N is the measured pulse number of the first frequency signal after filtering; The measuring the frequency of the second frequency signal by using the second reference signal as a reference signal includes: collecting the instantaneous phase difference between the second frequency signal and the second reference signal, and obtaining a digital signal representing the change of the phase difference; Integrating the digital signal to obtain a DC voltage signal; performing analog-to-digital conversion on the DC voltage signal to obtain a phase difference between the second frequency signal and the second reference signal; Determine the frequency of the second frequency signal according to the phase difference and the second reference signal. 2. The method according to claim 1, characterized in that the set multiple is 1-5 times. 3. The method according to claim 1 or 2, characterized in that, the first variance formula is an Allan variance formula, and the second variance formula is a Hadamard variance formula. 4. A measuring device for frequency stability, characterized in that said device comprises: A first frequency conversion module for performing frequency conversion on an output signal of a signal source under test to obtain a first frequency signal; A second frequency conversion module for performing frequency conversion on the output signal of the signal source under test to obtain a second frequency signal; A first measurement module for measuring the frequency of the first frequency signal obtained by the first frequency conversion module with the first reference signal as the reference signal and the set multiple of the frequency of the first frequency signal as the measurement bandwidth; a second measurement module for measuring the frequency of the second frequency signal obtained by the second frequency conversion module using the second reference signal as a reference signal; and The frequency of the first frequency signal measured by the first measurement module is used to determine the short-term frequency stability of the measured signal source according to the first variance formula, and the frequency of the first frequency signal measured by the second measurement module is used to determine the short-term frequency stability of the signal source under test. The frequency of the second frequency signal is a processing module for determining the long-term frequency stability of the measured signal source according to the second variance formula; The first frequency conversion module is electrically connected to the first measurement module and the processing module respectively, the second frequency conversion module is electrically connected to the second measurement module and the processing module respectively, and the processing module respectively electrically connected to the first measurement module and the second measurement module; The first measurement module is used for, performing low-pass filtering on the first frequency signal, and the filtering bandwidth is the measurement bandwidth; Taking the first reference signal as the time base signal, measuring the number of pulses of the first frequency signal filtered within a given time; Calculate the frequency of the first frequency signal according to the following formula: F=1/(T/N); Wherein, F is the frequency of the first frequency signal, T is the given time, and N is the measured pulse number of the first frequency signal after filtering; The second measurement module includes: a phase difference acquisition unit for acquiring the instantaneous phase difference between the second frequency signal and the second reference signal; An integrating circuit for integrating a digital signal to obtain a DC voltage signal, the digital signal is obtained by the processing module according to the instantaneous phase difference between the second frequency signal and the second reference signal; An analog-to-digital conversion unit for performing analog-to-digital conversion on the DC voltage signal to obtain a phase difference between the second frequency signal and the second reference signal; Correspondingly, the processing module is used for, The frequency of the second frequency signal is determined according to the phase difference obtained by the analog-to-digital conversion unit and the second reference signal. 5. The device according to claim 4, characterized in that the set multiple is 1-5 times. 6. The device according to claim 4, wherein the first frequency conversion module and the second frequency conversion module are the same module. 7. The device according to any one of claims 4-6, wherein the device further comprises a first signal source for providing the first reference signal and a signal source for providing the second reference signal A second signal source, the first signal source is electrically connected to the first frequency conversion module and the first measurement module respectively, the first signal source is a crystal oscillator; the second signal source is respectively connected to the first signal source The two frequency conversion modules are electrically connected to the second measurement module, and the second signal source is an atomic clock. 8. The device according to any one of claims 4-6, wherein the first variance formula is the Allan variance formula, and the second variance formula is the Hadamard variance formula.