Effective signal extraction method for multi-cycle linear optical sampling signal with extremely low duty ratio

Abstract

The invention discloses an effective signal extraction method for a multi-cycle linear optical sampling signal with an extremely low duty ratio. The method comprises the following steps: judging a time position of a first pulse energy maximum value in a multi-period extremely-low duty ratio linear optical sampling signal, and extracting all complete single-period signals in the multi-period extremely-low duty ratio linear optical sampling signal by using a position iteration method; setting an interception energy threshold value by utilizing the maximum energy value of each single-cycle linear optical sampling signal, and estimating the full width at half maximum of the main energy part of the pulse signal; and accurately covering the effective signal in each single-cycle linear optical sampling signal by taking the time position of the maximum energy value as the center and the multiple of the full width at half maximum as the coverage range so as to identify and extract the effective signal in the multi-cycle linear optical sampling signal with the extremely low duty ratio.

Description

Technical Field

[0001] This invention relates to the field of high-precision time measurement in information science and communication, and particularly to an effective signal identification and extraction method for multi-period linear optical sampling signals with extremely low duty cycles. Background Technology

[0002] Time is currently the most precisely measured physical quantity, and a high-precision time standard is crucial for a country's high-tech applications, military applications, economy, and social life. Furthermore, high-precision measurement of absolute time intervals is fundamental to many practical research and applications. Therefore, high-precision measurement of absolute time intervals has immense scientific research value and application prospects.

[0003] Time is defined in relation to the duration of a specific selected phenomenon. A clock is an instrument for measuring and displaying time. The earliest clocks were sundials, which had extremely low accuracy in measuring absolute time intervals and were easily affected by the environment. The advent of atomic clocks fundamentally improved this measurement capability. Currently, atomic clocks have been developed into various types, including cesium clocks, rubidium clocks, and hydrogen clocks. The typical stability of a rubidium atomic clock is around 10⁻⁶. -11 @1s in magnitude, cesium atomic clock close to 10 -12 @1 second level, hydrogen clock in 10 -13 The atomic clock, on the order of 1 second, provides a powerful technological guarantee for high-precision absolute time interval measurement.

[0004] Measuring the absolute time difference by measuring the relative time difference between two pulses is currently a hot research topic internationally. In recent years, researchers have proposed a linear optical sampling scheme (also known as dual-comb technology) to overcome the limitations of traditional electrical measurements, thereby achieving high-precision time difference measurement. The basic idea is to introduce a third optical comb, the frequency of which is the same as the frequency f of the optical comb under test. r The difference is a small amount Δf r This is used to amplify the time interval between the pulse signals of the two optical combs under test. The linear optical sampling signals (linear optical sampling signals) obtained by the third optical comb performing linear optical sampling with the two optical combs under test are used to accurately calculate the amplified time interval using the centroid position of the signal envelope, and then divided by the amplification factor, f. r / Δf r This allows us to obtain the precise time difference between the two optical combs under test.

[0005] However, the effective duty cycle of linear optical sampling signals is extremely low. Simultaneously processing most of the invalid signals is a huge waste of computational resources and slows down the processing speed. More seriously, these data portions that do not contain pulse signals are mainly composed of electrical signals. The introduction of a large amount of this data will deteriorate the estimation results of time information, thereby worsening the measurement stability of the system.

[0006] On the other hand, in high-speed time difference measurement technology, single-cycle sampling of linear optical sampling signals will cause interruption of time data. Therefore, it is necessary to continuously sample the interference signal for multiple cycles to finally obtain a linear optical sampling interference signal containing multiple cycles. Directly calculating the envelope centroid of the multi-cycle linear optical sampling signal cannot obtain the accurate time position of each interference wave packet. Summary of the Invention

[0007] To address the technical problems existing in the prior art, the purpose of this invention is to propose an effective signal identification and extraction method for multi-period ultra-low duty cycle linear optical sampling signals. This invention proposes an effective signal identification and extraction method to process multi-period ultra-low duty cycle linear optical sampling signals, in order to obtain the accurate time position of each interference packet.

[0008] The technical solution of this invention is as follows:

[0009] An effective signal identification and extraction method for multi-period ultra-low duty cycle linear optical sampling signals, the steps of which include:

[0010] 1) Acquisition of multi-period ultra-low duty cycle linear optical sampling signals: the frequency of the reference optical comb and the frequency f of the optical comb under test. r Phase difference setting Δf r Linear optical sampling is performed on the reference optical comb and the optical comb under test. The oscilloscope is used to acquire multi-period extremely low duty cycle linear optical sampling signals with a time interval of (0, mT), where m is the number of periods and T is the period of the linear optical sampling signal (equal to 1 / Δf). r );

[0011] 2) Single-cycle signal extraction: Extract the first single-cycle linear optical sampling signal with a time interval of (0, T) from the multi-cycle extremely low duty cycle linear optical sampling signal;

[0012] 3) Signal maximum value search: Locate the magnitude V′ of the energy maximum point in the first single-cycle signal obtained according to the method in step 2). max And find the corresponding time position t′. max ;

[0013] 4) Energy peak time determination: Determine the energy peak time t′ of the signal. max To make a judgment, when When the signal peak is determined to be left-biased, When the signal's main peak position is determined to be normal, When the signal peak is determined to be right-biased;

[0014] 5) Periodic Truncation Correction: When the discrimination result in step 4) is that the signal peak is left-biased, the truncation time interval for correcting the first single-cycle linear optical sampling signal is... When the signal peak is determined to be right-biased, the truncation time interval for correcting the first single-cycle linear optical sampling signal is: If the position of the main peak of the signal is determined to be normal, no correction processing is performed. The signal maximum value search operation is repeated to obtain the correct peak value V. max and time position t max ;

[0015] 6) Full width at half maximum (FWHM) estimation: A single-cycle linear optical sampling signal is a pulse signal with an extremely low duty cycle. The effective signal portion consists of one main lobe and four side lobes. A threshold energy V is set for extraction. threshold =V max / 2, determine all values ​​greater than or equal to V within a single periodic time interval. threshold The data is recorded in ascending order of time (t1, t2…t). n ), calculate the full width at half maximum (FWHM) T of the main lobe of the effective pulse signal. FWHM =t n -t1;

[0016] 7) Effective signal range coverage: The intercepted time interval is (t max -lT FWHM , t max +lT FWHM The signal is used as the effective linear optical sampling signal within a single period, where l is a multiple of the full width at half maximum (FWHM) and l is automatically adjusted according to the size of the main lobe of the effective signal.

[0017] 8) Update the cutoff interval: based on the current correct energy peak time position t max The signal capture time interval for automatically updating the next single-cycle signal is... The correct energy peak time avoids signal main peak shift in subsequent cycle truncation, and subsequent cycle truncation no longer needs to execute steps 4 to 5), thus improving processing speed and efficiency.

[0018] Furthermore, when acquiring the 2nd, 3rd, ... xth single-cycle signal, only steps 2-3) and steps 6-8) need to be performed. At this time, the truncation time interval in step 2) is the same as the truncation time interval updated in step 8) of the (x-1)th single-cycle truncation operation. t max (x-1) represents the time position of the peak energy of the (x-1)th single-cycle signal. Simultaneously, since no further discrimination and correction operations are needed, step 3) directly yields the correct peak value V of the xth single-cycle signal. max (x) and time position t max (x); Set the energy threshold V. threshold (x)=V max(x) / 2, representing all data V greater than or equal to the x-th single-cycle linear optical sampling signal in ascending order. threshold At time (x), calculate the full width at half maximum (FWHM) T of the main energy component of the corresponding pulse signal. FWHM (x); then the time interval is t. max (x)-lT FWHM (x), t max (x)+lT FWHM The signal (x) is used as the effective linear optical sampling signal in the xth single-cycle linear optical sampling signal.

[0019] Furthermore, when the time position t is the maximum energy of the x-th single-cycle signal... max When (x) > (m-1.5)T, the (x+1)th single-cycle signal is no longer truncated. Here, x satisfies 2≤x≤m or m-1. When it is determined that the main peak of the signal is left-biased or right-biased, the maximum number of single-cycle linear optical sampling signals is m-1.

[0020] Compared with the prior art, the positive effects of the present invention are as follows:

[0021] (1) Through operations such as single-cycle signal truncation, energy peak time discrimination, cycle truncation correction, and truncation interval update, each single-cycle interference wave packet signal is accurately extracted from the multi-cycle extremely low duty cycle linear optical sampling signal. The range of the first single-cycle signal is the truncation time interval obtained in step 5), and the ranges of the second, third, ..., xth single-cycle signals are... t max (x-1) is the time position of the peak signal energy of the (x-1)th single-cycle signal;

[0022] (2) The effective signal of each interference wave packet is accurately identified and extracted from the multi-period extremely low duty cycle linear optical sampling signal through operations such as signal maximum value search, half width at half maximum (WHM) estimation and effective signal range coverage, i.e. the signal obtained in step 7). Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the invention.

[0024] Figure 2 This is a flowchart of the effective signal recognition and extraction method of the present invention. Detailed Implementation

[0025] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings.

[0026] The acquired signal is a periodic pulse signal, such as Figure 1As shown. The repetition frequency difference between the reference optical comb and the optical comb under test is 1 kHz, so the period of the linear optical sampling interference signal is 1 ms. Due to local noise interference from the photodetector and sampling equipment, the effective part of the linear optical sampling interference signal consists of the main peak and four side lobes on both sides, accounting for approximately 0.6% (6‰) of the entire period, while the invalid signal accounts for 99.4% of the entire period. Multi-cycle ground voltage data acquisition is performed using a high-performance oscilloscope. The method flow of this invention is as follows: Figure 2 As shown, consider the entire process:

[0027] 1. Control a high-performance oscilloscope to acquire m cycles of linear optical sampling interference signals, for example, 100 cycles, with the acquisition time interval being (0, 100 ms). Control methods for the oscilloscope include, but are not limited to, serial communication and USB flash drive acquisition.

[0028] 2. Determine the number of processing iterations. If this is the first time processing this segment of multi-cycle linear optical sampling data, extract a single cycle of linear optical sampling signal within a time interval of (0, 1ms). If the number of processing iterations is greater than or equal to 2, extract a single cycle of linear optical sampling signal within the time interval updated in the previous processing iteration.

[0029] 3. Detect the magnitude V′ of the energy maximum point in a single-cycle linear optical sampling signal. max And find the corresponding time position t′. max ;

[0030] 4. For the time position t′ of the maximum value max Perform discrimination and correct the intercepted time interval: when t′ max When <0.5ms, the signal main peak is determined to be left-biased, and the truncation time interval for correcting a single-cycle linear optical sampling signal is (t′). max +0.5ms, t′ max +1.5ms); when t′ max When the value is greater than 0.5ms, the main peak of the signal is determined to be right-biased, and the truncation time interval for correcting a single-cycle linear optical sampling signal is (t′). max -0.5ms, t′ max +0.5ms); when t′ max When the time is 0.5ms, the signal peak position is determined to be normal, and no correction is performed. The magnitude V of the maximum energy point of the single-cycle linear optical sampling signal is then recalculated. max and the corresponding time position t max ;

[0031] 5. Set the energy interception threshold V threshold =V max / 2, record all values ​​greater than or equal to V in ascending order. threshold The data time points (t1, t2…t)n ), calculate the full width at half maximum (FWHM) T of the main energy component of the pulse signal. FWHM =t n -t1;

[0032] 6. The time interval to be extracted is (t) max -lT FWHM , t max +lT FWHM The signal is used as the effective linear optical sampling signal, where l is a multiple of the full width at half maximum (FWHM), for example, l = 3;

[0033] 7. Based on the time position t of the energy peak max Update the signal truncation time interval for the next single-cycle signal as follows: Wherein, the intercept time interval for the x-th single-cycle linear optical sampling signal is set to t max (x-1) represents the time position of the energy peak of the linear optical sampling signal in the (x-1)th single-cycle period, where x ≥ 2; then, the maximum energy V in the linear optical sampling signal in the xth single-cycle period is located. max (x), and calculate the corresponding time position t. max (x); Set the energy threshold V. threshold (x)=V max (x) / 2, representing all data V greater than or equal to the x-th single-cycle linear optical sampling signal in ascending order. threshold At time (x), calculate the full width at half maximum (FWHM) T of the main energy component of the corresponding pulse signal. FWHM (x); then the time interval is t. max (x)-lT FWHM (x), t max (x)+lT FWHM The signal (x) is used as the effective linear optical sampling signal in the xth single-cycle linear optical sampling signal.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention. The scope of protection of the present invention should be determined by the claims.

Claims

1. An effective signal extraction method for multi-period ultra-low duty cycle linear optical sampling signals, comprising the following steps: 1) Compare the frequency of the reference optical comb with the frequency f of the optical comb under test. r The frequency difference is set as Δf r Linear optical sampling was performed on the reference optical comb and the optical comb under test, and the oscilloscope was used to acquire multi-period extremely low duty cycle linear optical sampling signals with a time interval of (0, mT); where m is the number of periods, T is the period of the linear optical sampling signal, and T = 1 / Δf r ; 2) Extract the first single-cycle linear optical sampling signal with a time interval of (0, T) from the multi-cycle extremely low duty cycle linear optical sampling signal; 3) Locate the maximum energy V′ in the first single-cycle linear optical sampling signal. max And find the corresponding time position t′. max ; 4) When When the signal's main peak is determined to be left-biased, When the signal's main peak position is determined to be normal, The signal is determined to be right-biased by the main peak. 5) When the judgment result of step 4) is that the main peak of the signal is left-biased, the truncation time interval for correcting the first single-cycle linear optical sampling signal is: When the discrimination result indicates that the main peak of the signal is right-biased, the truncation time interval for correcting the first single-cycle linear optical sampling signal is: When the position of the main peak of the signal is determined to be normal, no correction processing is performed; the maximum energy V in the first single-cycle linear optical sampling signal is repositioned. max and the corresponding time position t max ; 6) Set the energy interception threshold V threshold =V max / 2, determine all values ​​greater than or equal to V within a single periodic time interval. threshold The data is recorded in ascending order of time (t1, t2…t). n ), calculate the full width at half maximum (FWHM) T of the main lobe of the effective pulse signal. FWHM =t n -t1; 7) The intercepted time interval is (t max -lT FWHM , t max +lT FWHM The signal is used as the effective linear optical sampling signal within a single period; where l is a multiple of the full width at half maximum (FWHM), and l is automatically adjusted according to the size of the main lobe of the effective signal. 8) Based on the time position t corresponding to the energy peak of the current single-cycle linear optical sampling signal max Update the truncation time interval for the next single-cycle linear optical sampling signal; where the truncation time interval for the x-th single-cycle linear optical sampling signal is set to... t max (x-1) is the time position of the peak energy of the linear optical sampling signal in the (x-1)th single cycle, where x≥2; 9) Locate the maximum energy V in the x-th single-cycle linear optical sampling signal. max (x), and calculate the corresponding time position t. max (x); Set the energy threshold V. threshold (x)=V max (x) / 2, representing all data V greater than or equal to the x-th single-cycle linear optical sampling signal in ascending order. threshold At time (x), calculate the full width at half maximum (FWHM) T of the main energy component of the corresponding pulse signal. FWHM (x); then the time interval is t. max (x)-lT FWHM (x), t max (x)+lT FWHM The signal (x) is used as the effective linear optical sampling signal in the xth single-cycle linear optical sampling signal.

2. The method according to claim 1, characterized in that, When the time position of the maximum energy in the x-th single-cycle linear optical sampling signal is t max When (x)>(m-1.5)T, the (x+1)th single-cycle linear optical sampling signal is no longer truncated; where x satisfies 2≤x≤m or m-1.

3. The method according to claim 2, characterized in that, When the signal is determined to be left- or right-biased, the maximum number of linear optical sampling signals in a single period is m-1.

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