CN112964930A - Rubidium clock-independent device frequency stability measuring method - Google Patents

Rubidium clock-independent device frequency stability measuring method Download PDF

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CN112964930A
CN112964930A CN202110317740.8A CN202110317740A CN112964930A CN 112964930 A CN112964930 A CN 112964930A CN 202110317740 A CN202110317740 A CN 202110317740A CN 112964930 A CN112964930 A CN 112964930A
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frequency
signal
signal acquisition
clock
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CN112964930B (en
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郭淑霞
高颖
刘宁
吴义春
王江宇
白倩
侯泽宇
高培伟
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Northwestern Polytechnical University
Xian Aisheng Technology Group Co Ltd
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Northwestern Polytechnical University
Xian Aisheng Technology Group Co Ltd
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    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
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Abstract

The invention relates to a rubidium clock-independent device frequency stability measuring method, which is based on an external synchronization method and adopts a vector signal source SMU200A to generate an input signal and simultaneously provides an external clock reference for a clock module of a signal acquisition device. After a test system is built according to a test principle block diagram, an input signal with the sampling frequency difference of 0.1Hz with 1GHz is generated by a vector signal source SMU200A and injected into a signal acquisition device, signal data acquired by the signal acquisition device is subjected to time domain drawing, and the frequency stability of the signal acquisition device, which is obtained by analyzing a time domain diagram, reaches 10‑10And (4) concluding. The method has the beneficial effects that the dependence on measuring equipment (such as a rubidium clock, a time interval counter and other high-precision measuring instruments) is reduced on the basis of ensuring the accuracy and credibility of the frequency stability measuring result of the equipment. The measurement system is easy to set up and the data legend for the analysis is easy to understand.

Description

Rubidium clock-independent device frequency stability measuring method
Technical Field
The invention belongs to frequency stability measurement of signal acquisition equipment, and relates to a method for measuring the frequency stability of equipment independent of a rubidium clock.
Background
With the rapid development of the information age, electronic warfare has become an important fighting mode of the information age. Complex electromagnetic signals in the electronic warfare are invisible, unknown and have dynamic characteristics, and whether the acquisition equipment can comprehensively and accurately acquire complex electromagnetic information of a battlefield is of great importance. The credibility of the signal frequency acquired by the acquisition equipment is influenced by the frequency stability of the equipment. The accurate acquisition of the interference signal frequency can provide effective battlefield information for the combat commander, and plays an important role in assisting decision.
The measurement of the frequency stability is a comparative measurement method, and common measurement methods can be divided into frequency domain measurement and time domain measurement. The frequency stability frequency domain shows spectral impurities, which are mainly affected by internal noise of the frequency source, resulting in random phase fluctuation or frequency fluctuation, i.e. phase noise. Common methods for measuring phase noise include measuring the power spectral density of relative frequency fluctuations with a spectrum analyzer, heterodyne counting measurement, frequency discriminator measurement, phase discriminator measurement, and the like. The time domain characterization of frequency stability is the magnitude of the difference in the individual frequency values with respect to the frequency average caused by noise, i.e. the random fluctuation of the frequency average. The frequency stability of the time domain is often characterized by using the allen variance.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a device frequency stability measuring method independent of a rubidium clock.
Technical scheme
A rubidium clock independent device frequency stability measuring method, characterized by the steps of:
step 1: connecting a 10MHz clock output port of the vector signal source with a clock synchronization port of an external clock of the signal acquisition equipment through a low-loss cable, and setting the sampling frequency of the signal acquisition equipment to be 1 GHz; connecting a radio frequency output port of the vector signal source with a radio frequency input port of the signal acquisition equipment through a low-loss cable, and setting the frequency of a signal to be 1GHz +0.1 Hz;
step 2, setting relevant parameters on an operation interface of the signal acquisition equipment: the frequency of the electronic clock is 1000 MHz; external clock synchronization is adopted in the signal acquisition software interface selection equipment, and the frequency is 1000 MHz; setting the size of signal acquisition data as 15000 MB;
and step 3: transmitting signal 1GHz +0.1Hz with reference frequency f0Is 1 GHz; obtaining a signal with the frequency of 0.1Hz after frequency mixing by signal acquisition equipment; collecting the signals, wherein the collected signals take 10 seconds as a period to obtain the length of collected data of 15G;
converting the acquired 12-bit signal original data into 16-bit MATLAB, and extracting sampling points at equal intervals from the converted data to draw an MATLAB time domain graph of the signal;
the formula for extracting the data at equal intervals is as follows:
X＝x(n)
Y＝x(n)*δ(k*ts)， k＝0,1,···,N
wherein X is the data point after data conversion, Y is the data point after sampling at equal intervals, tsThe sampling interval is set, and N is the number of sampling points;
and 4, step 4: if a time domain graph obtained by drawing the converted signal data by the MATLAB is a sine wave signal of one period, the signal acquisition equipment can distinguish a signal with the frequency of 0.1 Hz;
calculating the frequency stability of the equipment: k ═ Δ f/f0Wherein K is the frequency stability, and Δ f is the maximum deviation value between the measured frequency and the reference frequency，f0Is the reference frequency.
The data conversion is: the conversion formula of the data with 8 high bits is as follows: adrh — Adrh 16, the conversion formula of the lower 4 bits of the data is: adrl is _ Adrl/16, where Adrh is the upper 8-bit data after data format conversion, _ Adrh is the upper 8-bit data in the AD data, _ Adrl is the lower 4-bit data after data format conversion, and _adrlis the lower 8-bit data in the AD data.
The vector signal source adopts an SMU200A vector signal source.
Advantageous effects
The method for measuring the frequency stability of the equipment independent of the rubidium clock is based on an external synchronization method, adopts a vector signal source SMU200A to generate an input signal, and provides an external clock reference for a clock module of signal acquisition equipment. After a test system is built according to a test principle block diagram, an input signal with the sampling frequency difference of 0.1Hz with 1GHz is generated by a vector signal source SMU200A and injected into a signal acquisition device, signal data acquired by the signal acquisition device is subjected to time domain drawing, and the frequency stability of the signal acquisition device, which is obtained by analyzing a time domain diagram, reaches 10-10And (4) concluding.
The method has the beneficial effects that the dependence on measuring equipment (such as a rubidium clock, a time interval counter and other high-precision measuring instruments) is reduced on the basis of ensuring the accuracy and credibility of the frequency stability measuring result of the equipment. The measurement system is easy to set up and the data legend for the analysis is easy to understand.
Drawings
FIG. 1: signal acquisition equipment frequency stability measuring and analyzing system flow chart
FIG. 2: a signal acquisition device frequency stability measurement system block diagram;
FIG. 3: an external clock module parameter setting diagram;
FIG. 4: a signal acquisition interface;
FIG. 5: MATLAB analysis result chart.
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
the method comprises the following steps
Frequency stability measurement system set-up
The method is used for measuring the frequency stability of the signal acquisition equipment, and the required instruments and equipment are shown in table 1. The measurement system is built according to the test principle block diagram shown in fig. 2.
TABLE 1 measurement instrumentation
Figure BDA0002991561860000041
Step 1: frequency stability measurement system setup
Connecting a 10MHz clock output port of the vector signal source SMU200A with a clock synchronization port of an external clock of the signal acquisition equipment through a low-loss cable, and setting the sampling frequency of the signal acquisition equipment to be 1 GHz; and the radio frequency output port of the vector signal source SMU200A is connected with the radio frequency input port of the signal acquisition equipment through a low-loss cable, and the frequency of the signal is set to be 1GHz +0.1 Hz.
Step 2: signal data acquisition
And setting related parameters on an operation interface of the signal acquisition equipment. Setting the frequency of an electronic clock to be 1000 MHz; external clock synchronization is adopted in the signal acquisition software interface selection equipment, the frequency is 1000MHz, and the method is shown in figure 3;
observing the frequency domain waveform of the signal, and setting the size of signal acquisition data as 15000 MB; 15G data acquired by the 12-bit AD is stored in a high-bit alignment mode, and the format is converted into low-bit alignment for direct processing by MATLAB, as shown in FIG. 4.
And step 3: data processing
The original data size of the test signal acquired by the signal acquisition equipment is 15GB, and the data size obtained after data format conversion is about 20 GB. And extracting sampling points at equal intervals to draw an MATLAB time domain graph of the signal.
The time delay of the time domain can cause the phase change of the frequency domain, and the phase change of 20G data points is finally reflected on the waveform of the signal. A full period of 0.1Hz can be drawn from the collected data and the phase change of the data points is represented on the time domain plot, as shown in fig. 5.
The time domain plot drawn by MATLAB is the acquired mixed signal (0.1Hz), i.e. a periodic sine wave signal, indicating that the device can distinguish 0.1Hz at a reference frequency of 1 GHz.
And 4, step 4: analysis of results
The transmitting signal is 1GHz +0.1Hz, the signal with the frequency of 0.1Hz is obtained after frequency mixing by signal acquisition equipment, the signal is acquired, one cycle of the acquired signal is 10 seconds, and the length of the acquired data is 15G.
The data conversion is implemented as follows:
the conversion formula for obtaining the high 8 bits of the data is as follows:
Adrh＝_adrh*16
the conversion formula for obtaining the lower 4 bits of the data is as follows:
Adrl＝_adrl/16
adrh is the high 8-bit data after data format conversion, _ Adrh is the high 8-bit data in the AD data, Adrl is the low 4-bit data after data format conversion, and _adrlis the low 8-bit data in the AD data.
The specific implementation mode of the data equal interval extraction is as follows:
the formula for extracting the existing data at equal intervals is as follows:
X＝x(n)
Y＝x(n)*δ(k*ts)， k＝0,1,···,N
wherein X is the data point after data conversion, Y is the data point after sampling at equal intervals, tsThe sampling interval is N is the number of sampling points.
The calculation formula of the frequency stability is as follows:
K＝Δf/f0
wherein K is the frequency stability, Δ f is the maximum deviation value between the measured frequency and the reference frequency, f0Is the reference frequency.
The transmitted signal is 1GHz +0.1Hz, wherein the reference frequency f0At 1GHz, the frequency deviation Δ f was 0.1 Hz. Passing the transmitting signal throughAnd obtaining a signal with the frequency of 0.1Hz after frequency mixing by signal acquisition equipment, and acquiring the signal, wherein one cycle of the acquired signal is 10 seconds, and the length of the acquired data is 15G. If the time domain graph obtained by drawing the converted signal data by the MATLAB is a sine wave signal of one period, the fact that the signal acquisition equipment can distinguish the signal with the frequency of 0.1Hz indicates that the frequency stability of the equipment reaches 10-10。

Claims (3)

1. A rubidium clock independent device frequency stability measuring method, characterized by the steps of:
step 1: connecting a 10MHz clock output port of the vector signal source with a clock synchronization port of an external clock of the signal acquisition equipment through a low-loss cable, and setting the sampling frequency of the signal acquisition equipment to be 1 GHz; connecting a radio frequency output port of the vector signal source with a radio frequency input port of the signal acquisition equipment through a low-loss cable, and setting the frequency of a signal to be 1GHz +0.1 Hz;
step 2, setting relevant parameters on an operation interface of the signal acquisition equipment: the frequency of the electronic clock is 1000 MHz; external clock synchronization is adopted in the signal acquisition software interface selection equipment, and the frequency is 1000 MHz; setting the size of signal acquisition data as 15000 MB;
and step 3: transmitting signal 1GHz +0.1Hz with reference frequency f0Is 1 GHz; obtaining a signal with the frequency of 0.1Hz after frequency mixing by signal acquisition equipment; collecting the signals, wherein the collected signals take 10 seconds as a period to obtain the length of collected data of 15G;
converting the acquired 12-bit signal original data into 16-bit MATLAB, and extracting sampling points at equal intervals from the converted data to draw an MATLAB time domain graph of the signal;
the formula for extracting the data at equal intervals is as follows:
X＝x(n)
Y＝x(n)*δ(k*ts)，k＝0,1,···,N
wherein X is the data point after data conversion, Y is the data point after sampling at equal intervals, tsThe sampling interval is set, and N is the number of sampling points;
and 4, step 4: if a time domain graph obtained by drawing the converted signal data by the MATLAB is a sine wave signal of one period, the signal acquisition equipment can distinguish a signal with the frequency of 0.1 Hz;
calculating the frequency stability of the equipment: k ═ Δ f/f0Where K is the frequency stability, Δ f is the maximum deviation of the measured frequency from the reference frequency, f0Is the reference frequency.
2. The method of measuring frequency stability of a rubidium clock-independent device according to claim 1, wherein: the data conversion is: the conversion formula of the data with 8 high bits is as follows: adrh — Adrh 16, the conversion formula of the lower 4 bits of the data is: adrl is _ Adrl/16, where Adrh is the upper 8-bit data after data format conversion, _ Adrh is the upper 8-bit data in the AD data, _ Adrl is the lower 4-bit data after data format conversion, and _adrlis the lower 8-bit data in the AD data.
3. The method of measuring frequency stability of a rubidium clock-independent device according to claim 1, wherein: the vector signal source adopts an SMU200A vector signal source.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1963543A (en) * 2006-11-23 2007-05-16 江汉大学 Improved method and apparatus for measuring stability of frequency of time domain signal
WO2012062207A1 (en) * 2010-11-11 2012-05-18 国网电力科学研究院 Standard frequency and time adjusting method based on rubidium oscillator
CN104935329A (en) * 2015-06-29 2015-09-23 大唐电信（成都）信息技术有限公司 Multi-channel reference source soft switching method and system of time synchronizer
CN109309541A (en) * 2018-10-10 2019-02-05 西北工业大学 One kind being based on the jamproof half physical varification system of Unmanned Aerial Vehicle Data Link and verification method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1963543A (en) * 2006-11-23 2007-05-16 江汉大学 Improved method and apparatus for measuring stability of frequency of time domain signal
WO2012062207A1 (en) * 2010-11-11 2012-05-18 国网电力科学研究院 Standard frequency and time adjusting method based on rubidium oscillator
CN104935329A (en) * 2015-06-29 2015-09-23 大唐电信（成都）信息技术有限公司 Multi-channel reference source soft switching method and system of time synchronizer
CN109309541A (en) * 2018-10-10 2019-02-05 西北工业大学 One kind being based on the jamproof half physical varification system of Unmanned Aerial Vehicle Data Link and verification method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
王学玲;王华力;曾显华;郭克锋;: "稀疏多带信号的压缩采样技术的研究", 通信技术, no. 09 *

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