Pilot assisted timing interpolation based adc sampling offset compensation method and system
By using pilot-assisted timing interpolation, the sampling time is reconstructed in the time domain, solving the problem of synchronous suppression of carrier and upper and lower sideband phase noise, achieving high-precision signal compensation, and meeting the measurement requirements of space gravitational wave detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-05-08
- Publication Date
- 2026-07-21
AI Technical Summary
In space gravitational wave detection, existing technologies struggle to universally suppress carrier and upper/lower sideband phase noise in complex mixed signals. Traditional phase domain correction methods cannot effectively eliminate phase errors of multiple frequency components, thus limiting measurement accuracy.
By using a pilot-assisted timing interpolation method, the sampling time is reconstructed in the time domain using the Farrow structure and Horner nested algorithm, directly repairing the sampling offset and achieving synchronous suppression of carrier and upper and lower sideband phase noise.
It achieves complete repair of carrier and upper and lower sideband phase noise, meets the requirements of subsequent algorithms for sideband phase accuracy, reduces hardware resource consumption, and improves signal purity and phase stability.
Smart Images
Figure CN122437545A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of digital signal processing and space gravitational wave detection technology, specifically relating to an ADC (analog-to-digital converter) sampling offset compensation method and system based on pilot-assisted timing interpolation. Background Technology
[0002] In extremely precise measurement missions such as space gravitational wave detection, the accuracy requirements for measuring the minute phase changes caused by gravitational waves reach the sub-milliradian level. At the receiver, the sampling clock provided by the ultra-stable oscillator (USO) is subject to physical jitter, while the transient response of thermal noise in the switching devices inside the ADC causes aperture jitter. The superposition of these two jitters causes a deviation in the amplitude of the signal captured by the ADC at any ideal sampling moment. For the sampled high-frequency signal, this time uncertainty is amplified into a significant phase error (i.e., clock phase noise), severely limiting the lower limit of measurement.
[0003] Existing technologies typically employ a "result compensation" approach in the phase domain, extracting the phase error at the carrier frequency through the pilot branch and then subtracting it in the back-end algorithm to cancel it out. However, the scientific measurement target of space gravitational wave detection is not only the main carrier; the core data processing heavily relies on the upper and lower sideband signals distributed on both sides of the main carrier. Since phase error is proportional to frequency, traditional phase domain correction methods can often only accurately cancel a single carrier frequency point. In complex mixed signals containing the carrier and upper and lower sidebands, phase domain compensation cannot guarantee complete and synchronous cancellation of phase noise from multiple frequency components, resulting in residual phase noise in the upper and lower sidebands still exceeding the limit.
[0004] In contrast, sampling offset is physically a non-uniform jitter in the time domain. According to the sampling theorem, if the deviation in sampling time can be directly corrected in the time domain, the correction will apply to all frequency components in the mixed signal. Therefore, how to achieve universal suppression of carrier and upper / lower sideband phase noise using time-domain reconstruction techniques in the front-end digital domain is a key problem that urgently needs to be solved in the field of precision space measurement. Summary of the Invention
[0005] To address the problems and needs existing in the background technology, this invention provides an ADC sampling offset compensation method and system based on pilot-assisted timing interpolation. This invention utilizes a Farrow structure in the front-end digital domain to accurately reconstruct the jittered sampling sequence in the time domain, eliminating sampling time offset from the physical time base, thereby significantly improving signal purity and phase stability.
[0006] The specific technical solution adopted in this invention is as follows:
[0007] In a first aspect, the present invention proposes an ADC sampling offset compensation method based on pilot-assisted timing interpolation, the method comprising the following steps:
[0008] The process involves acquiring a first scientific beat signal carrying gravitational wave information; linearly superimposing the first pilot signal and the first scientific beat signal to form a hybrid measurement signal, which is then input to an analog-to-digital converter for common-path digital sampling to obtain a discrete sampling sequence; wherein the module generating the first pilot signal and the sampling clock of the analog-to-digital converter are from the same source; then, separating the second pilot signal and the second scientific beat signal from the discrete sampling sequence, and extracting the instantaneous phase noise sequence from the second pilot signal; finally, based on the instantaneous phase noise sequence, reconstructing the second scientific beat signal in the time domain to obtain a third scientific beat signal.
[0009] Furthermore, the first scientific beat frequency signal includes a carrier beat frequency signal, an upper sideband beat frequency signal, and a lower sideband beat frequency signal.
[0010] Further, the extraction of the instantaneous phase noise sequence from the second pilot signal includes:
[0011] After digital down-conversion processing of the second pilot signal, the pilot baseband signal is obtained; then the pilot baseband signal is input into a second-order pilot phase-locked loop, which tracks the phase fluctuation of the pilot single-tone signal in real time, thereby extracting the instantaneous phase noise sequence.
[0012] Further, the step of reconstructing the second scientific beat frequency signal in the time domain based on the instantaneous phase noise sequence to obtain the third scientific beat frequency signal includes:
[0013] Convert the instantaneous phase noise sequence into a fractional delay parameter. Then, based on the decimal delay parameter The second scientific beat frequency signal is reconstructed in the time domain to obtain the third scientific beat frequency signal.
[0014] Furthermore, the instantaneous phase noise sequence is converted into a fractional delay parameter. ,include:
[0015] The instantaneous phase noise sequence is mapped to the instantaneous time jitter at the ADC sampling moment, and then the instantaneous time jitter is normalized to the sampling period of the analog-to-digital converter to obtain the fractional delay parameter. .
[0016] Furthermore, after low-pass filtering the discrete sampling sequence, the second pilot signal is obtained; after high-pass filtering the discrete sampling sequence, the second scientific beat frequency signal is obtained.
[0017] The second invention proposes an ADC sampling offset compensation system based on pilot-assisted timing interpolation, the system comprising:
[0018] The signal acquisition module is used to acquire the first scientific beat frequency signal carrying gravitational wave information and combine it with the first pilot signal to generate a mixed measurement signal. The analog-to-digital converter performs common-path digital sampling on the mixed measurement signal and outputs a discrete sampling sequence.
[0019] Pilot phase noise extraction module, used to extract instantaneous phase noise sequence from discrete sampling sequence;
[0020] The time-domain correction module is used to reconstruct the second scientific beat frequency signal in the discrete sampling sequence in the time domain based on the instantaneous phase noise sequence.
[0021] Furthermore, the signal acquisition module includes:
[0022] A photoelectric conversion device is used to acquire the first scientific beat frequency signal carrying gravitational wave information;
[0023] Pilot signal generator, used to generate a first pilot signal based on a local reference source;
[0024] An adder is used to linearly superimpose the first scientific beat frequency signal and the first pilot signal to output a mixed measurement signal;
[0025] An analog-to-digital converter is used to perform common-path digital sampling of mixed measurement signals to obtain discrete sampling sequences.
[0026] Furthermore, the pilot phase noise extraction module includes:
[0027] A digital low-pass filter is used to separate the second pilot signal from the discrete sampling sequence;
[0028] A digital downconverter is used to perform digital downconversion processing on the second pilot signal to obtain the pilot baseband signal;
[0029] A second-order pilot phase-locked loop is used to track the phase fluctuations of the pilot single-tone signal in real time based on the input pilot baseband signal, thereby extracting the instantaneous phase noise sequence.
[0030] Furthermore, the time-domain correction module includes:
[0031] A digital high-pass filter is used to separate the second scientific beat frequency signal from a discrete sampled sequence;
[0032] The sampling mapping module is used to map the instantaneous phase noise sequence to the instantaneous time jitter at the ADC sampling moment;
[0033] The normalization module is used to normalize the instantaneous time jitter to the sampling period of the analog-to-digital converter, thereby obtaining the fractional delay parameter. ;
[0034] The time-domain reconstruction module is used to reconstruct the second scientific beat frequency signal in the time domain based on the instantaneous phase noise sequence to obtain the third scientific beat frequency signal.
[0035] Compared with the prior art, the beneficial effects of the present invention include at least the following:
[0036] Complete Time Reference Restoration: This invention directly restores the physical time reference through time-domain interpolation reconstruction. Since the sampling offset is consistent across all frequency components in the time domain, this invention eliminates carrier phase noise while simultaneously suppressing phase noise in the upper and lower sideband signals. This solves the technical problem that phase-domain compensation schemes cannot account for sideband frequency offsets, and meets the stringent requirements of subsequent algorithms such as TDI for sideband phase accuracy.
[0037] Eliminating common-mode error interference: By using a common-path sampling design for the scientific beat signal and the pilot signal, it is ensured that both undergo the same clock jitter and aperture jitter environment, enabling the pilot signal to serve as a precise "ruler" for characterizing the sampling deviation of the scientific signal.
[0038] Low hardware resource consumption and high real-time performance: By using a fixed coefficient matrix of the third-order Farrow structure in conjunction with the Horner nested algorithm, complex online filter coefficient calculations are avoided, significantly saving multiplier resources in programmable logic devices, and enabling real-time high-precision compensation at high sampling rates. Attached Figure Description
[0039] Figure 1 This is a system overall framework diagram of the present invention.
[0040] Figure 2 This is a sampling offset jitter error diagram extracted by the pilot phase-locked loop in an embodiment of the present invention.
[0041] Figure 3 This is a comparison diagram of the phase error distribution before and after timing interpolation compensation in an embodiment of the present invention. Detailed Implementation
[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.
[0043] The present invention proposes an ADC sampling offset compensation method based on pilot-assisted timing interpolation, which includes the following steps:
[0044] The first scientific beat frequency signal carrying gravitational wave information is acquired through a photoelectric conversion device; the first pilot signal and the first scientific beat frequency signal are linearly superimposed in the electrical domain using an adder to form a mixed measurement signal, which is then input to an analog-to-digital converter (ADC) for common-path digital sampling to obtain a discrete sampling sequence. The module generating the first pilot signal shares the same sampling clock as the analog-to-digital converter (ADC). Specifically, the pilot signal generator and the ADC's sampling clock are generated from the same local reference source. The local reference source simultaneously drives both the ADC's sampling control terminal and the pilot signal generator via a physical clock distribution network. Then, the discrete sampling sequence... The second pilot signal and the second scientific beat frequency signal are separated from the second pilot signal. The instantaneous phase noise sequence is extracted from the second pilot signal. Finally, the second scientific beat frequency signal is reconstructed in the time domain based on the instantaneous phase noise sequence to obtain the third scientific beat frequency signal, thereby realizing ADC sampling offset compensation.
[0045] In one feasible implementation, the first scientific beat frequency signal includes a carrier beat frequency signal, an upper sideband beat frequency signal, and a lower sideband beat frequency signal.
[0046] It should be noted that common-path digital sampling refers to sampling the mixed measurement signal input to the physical sampling channel of the ADC so that the first pilot signal and the first scientific beat frequency signal in the mixed measurement signal can simultaneously carry the same system clock jitter characteristics.
[0047] In one feasible implementation, from discrete sampling sequences The second pilot signal and the second scientific beat frequency signal are separated from the signal, including:
[0048] For discrete sampling sequences After low-pass filtering, the second pilot signal is obtained; the discrete sampling sequence is then processed. After high-pass filtering, the second scientific beat frequency signal is obtained.
[0049] In one feasible implementation, extracting the instantaneous phase noise sequence from the second pilot signal includes:
[0050] After digital down-conversion processing of the second pilot signal, the pilot baseband signal is obtained. The pilot baseband signal is then input into a second-order pilot phase-locked loop. The second-order pilot phase-locked loop tracks the phase fluctuation of the pilot single-tone signal in real time, thereby extracting an instantaneous phase noise sequence that accurately tracks the clock jitter characteristics.
[0051] This invention, based on the shared origin of the pilot signal and the sampling clock, extracts an instantaneous phase noise sequence that characterizes the combined effects of local reference source jitter and ADC internal aperture jitter. .
[0052] In one feasible implementation, the second scientific beat frequency signal is reconstructed in the time domain based on the instantaneous phase noise sequence to obtain the third scientific beat frequency signal, including:
[0053] Convert the instantaneous phase noise sequence into a fractional delay parameter. Then, based on the decimal delay parameter The second scientific beat frequency signal is reconstructed in the time domain to obtain the third scientific beat frequency signal, thereby eliminating the offset generated at the sampling time in the beat frequency signal.
[0054] In one feasible implementation, the second scientific beat frequency signal is reconstructed in the time domain based on the fractional delay parameter μ to obtain the third scientific beat frequency signal, specifically including:
[0055] The third-order Farrow interpolation structure is based on the fractional delay parameter corresponding to each beat frequency component. Time-domain reconstruction is performed on the corresponding beat frequency component in the second scientific beat frequency signal.
[0056] The process of temporal reconstruction includes:
[0057] For each sampling point in the second scientific beat frequency signal, a vector is constructed by acquiring the data of its four adjacent consecutive sampling points; a coefficient vector is generated using a fixed-tap coefficient matrix pre-stored in read-only memory (ROM); and the fractional delay parameter is completed using Horner nested multiplication logic. Polynomial fitting is used to obtain the corrected sampling points; after traversing all sampling points in the second scientific beat frequency signal, the corresponding corrected sampling points are obtained, and a correction sequence is generated based on all corrected sampling points. That is, the third scientific beat frequency signal.
[0058] In one feasible implementation, the instantaneous phase noise sequence is converted into a fractional delay parameter. ,include:
[0059] The instantaneous phase noise sequence is mapped to the instantaneous time jitter at the ADC sampling moment, and then the instantaneous time jitter is normalized to the sampling period of the analog-to-digital converter to obtain the fractional delay parameter. The specific formula is as follows:
[0060]
[0061]
[0062] in, The center frequency of the first pilot signal; The sampling period of the analog-to-digital converter is represented by the negative sign, indicating that the interpolation compensation direction is opposite to the sampling deviation direction. This refers to the instantaneous time jitter. It is an instantaneous phase noise sequence.
[0063] like Figure 1 As shown, the ADC sampling offset compensation system based on pilot-assisted timing interpolation proposed in this invention includes:
[0064] The signal acquisition module acquires the first scientific beat frequency signal carrying gravitational wave information and combines it with the first pilot signal to generate a mixed measurement signal. The analog-to-digital converter (ADC) performs common-path digitization sampling on the mixed measurement signal and outputs a discrete sampling sequence. ;
[0065] Pilot phase noise extraction module, used to extract phase noise from discrete sampled sequences Extract the instantaneous phase noise sequence;
[0066] The time-domain correction module is used to correct discrete sampled sequences based on the instantaneous phase noise sequence. The second scientific beat frequency signal in the time domain is reconstructed.
[0067] The signal acquisition module includes:
[0068] A photoelectric conversion device is used to acquire the first scientific beat frequency signal carrying gravitational wave information;
[0069] Pilot signal generator, used to generate a first pilot signal based on a local reference source;
[0070] An adder is used to linearly superimpose the first scientific beat frequency signal and the first pilot signal to output a mixed measurement signal;
[0071] Analog-to-digital converters are used to perform common-path digitization sampling of mixed measurement signals to obtain discrete sampling sequences. .
[0072] The pilot phase noise extraction module includes:
[0073] A digital low-pass filter (LPF) is used to separate the second pilot signal from a discrete sampled sequence;
[0074] A digital downconverter is used to perform digital downconversion processing on the second pilot signal to obtain the pilot baseband signal;
[0075] A second-order pilot phase-locked loop is used to track the phase fluctuations of the pilot single-tone signal in real time based on the input pilot baseband signal, thereby extracting the instantaneous phase noise sequence.
[0076] The time-domain correction module includes:
[0077] A digital high-pass filter (HPF) is used to separate the second scientific beat frequency signal from a discrete sampled sequence;
[0078] The sampling mapping module is used to map the instantaneous phase noise sequence to the instantaneous time jitter at the ADC sampling moment;
[0079] The normalization module is used to normalize the instantaneous time jitter to the sampling period of the analog-to-digital converter, thereby obtaining the fractional delay parameter. ;
[0080] The time-domain reconstruction module is used to reconstruct the second scientific beat frequency signal in the time domain based on the instantaneous phase noise sequence to obtain the third scientific beat frequency signal.
[0081] In an example of a space-based gravitational wave detection scenario, the system parameters are configured as follows:
[0082] The sampling clock is 80MHz, and the first scientific beat frequency signal includes a 15MHz carrier beat frequency, a 16MHz upper sideband beat frequency, and a 14MHz lower sideband beat frequency; the first pilot signal has a frequency of 5MHz. In addition, the system faces Doppler frequency offset peaks of ±100Hz (maximum rate of change 300Hz / s), ADC aperture jitter of 3ps / Hz, and ultra-stable clock (USO) Allan variance. Complex noise environment.
[0083] The method proposed in this invention exhibits outstanding performance in the following key indicators:
[0084] Extraction precision: such as Figure 2 As shown, the instantaneous phase noise sequence extracted by the second-order pilot phase-locked loop, after sampling and mapping, has an instantaneous time jitter error peak value that is less than 5 ps compared to the actual jitter error peak value.
[0085] Compensation effect: such as Figure 3 As shown, the phase error of the jitter signal without time-domain interpolation compensation still has a distribution at 60 mrad, while the phase error of the signal after time-domain interpolation compensation converges to within 20 mrad. The method of this invention eliminates the divergence of error distribution from the physical time reference. The gray bars in the figure represent the overlapping part of the phase error of the jitter signal without time-domain interpolation compensation and the phase error of the signal after time-domain interpolation compensation.
[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for compensating ADC sampling offset based on pilot-assisted timing interpolation, characterized in that, Includes the following steps: The process involves acquiring a first scientific beat signal carrying gravitational wave information; linearly superimposing the first pilot signal and the first scientific beat signal to form a hybrid measurement signal, which is then input to an analog-to-digital converter for common-path digital sampling to obtain a discrete sampling sequence; wherein the module generating the first pilot signal and the sampling clock of the analog-to-digital converter are from the same source; then, separating the second pilot signal and the second scientific beat signal from the discrete sampling sequence, and extracting the instantaneous phase noise sequence from the second pilot signal; finally, based on the instantaneous phase noise sequence, reconstructing the second scientific beat signal in the time domain to obtain a third scientific beat signal.
2. The ADC sampling offset compensation method based on pilot-assisted timing interpolation according to claim 1, characterized in that, The first scientific beat frequency signal includes a carrier beat frequency signal, an upper sideband beat frequency signal, and a lower sideband beat frequency signal.
3. The ADC sampling offset compensation method based on pilot-assisted timing interpolation according to claim 1, characterized in that, The extraction of the instantaneous phase noise sequence from the second pilot signal includes: After digital down-conversion processing of the second pilot signal, the pilot baseband signal is obtained; then the pilot baseband signal is input into a second-order pilot phase-locked loop, which tracks the phase fluctuation of the pilot single-tone signal in real time, thereby extracting the instantaneous phase noise sequence.
4. The ADC sampling offset compensation method based on pilot-assisted timing interpolation according to claim 1, characterized in that, The step of reconstructing the second scientific beat frequency signal in the time domain based on the instantaneous phase noise sequence to obtain the third scientific beat frequency signal includes: Convert the instantaneous phase noise sequence into a fractional delay parameter. Then, based on the decimal delay parameter... The second scientific beat frequency signal is reconstructed in the time domain to obtain the third scientific beat frequency signal.
5. The ADC sampling offset compensation method based on pilot-assisted timing interpolation according to claim 1, characterized in that, The instantaneous phase noise sequence is converted into a fractional delay parameter. ,include: The instantaneous phase noise sequence is mapped to the instantaneous time jitter at the ADC sampling moment, and then the instantaneous time jitter is normalized to the sampling period of the analog-to-digital converter to obtain the fractional delay parameter. .
6. The ADC sampling offset compensation method based on pilot-assisted timing interpolation according to claim 1, characterized in that, After low-pass filtering the discrete sampled sequence, the second pilot signal is obtained; after high-pass filtering the discrete sampled sequence, the second scientific beat frequency signal is obtained.
7. An ADC sampling offset compensation system based on pilot-assisted timing interpolation, characterized in that, include: The signal acquisition module is used to acquire the first scientific beat frequency signal carrying gravitational wave information and combine it with the first pilot signal to generate a mixed measurement signal. The analog-to-digital converter performs common-path digital sampling on the mixed measurement signal and outputs a discrete sampling sequence. Pilot phase noise extraction module, used to extract instantaneous phase noise sequence from discrete sampling sequence; The time-domain correction module is used to reconstruct the second scientific beat frequency signal in the discrete sampling sequence in the time domain based on the instantaneous phase noise sequence.
8. The ADC sampling offset compensation system based on pilot-assisted timing interpolation according to claim 7, characterized in that, The signal acquisition module includes: A photoelectric conversion device is used to acquire the first scientific beat frequency signal carrying gravitational wave information; Pilot signal generator, used to generate a first pilot signal based on a local reference source; An adder is used to linearly superimpose the first scientific beat frequency signal and the first pilot signal to output a mixed measurement signal; An analog-to-digital converter is used to perform common-path digital sampling of mixed measurement signals to obtain discrete sampling sequences.
9. The ADC sampling offset compensation system based on pilot-assisted timing interpolation according to claim 7, characterized in that, The pilot phase noise extraction module includes: A digital low-pass filter is used to separate the second pilot signal from the discrete sampling sequence; A digital downconverter is used to perform digital downconversion processing on the second pilot signal to obtain the pilot baseband signal; A second-order pilot phase-locked loop is used to track the phase fluctuations of the pilot single-tone signal in real time based on the input pilot baseband signal, thereby extracting the instantaneous phase noise sequence.
10. The ADC sampling offset compensation system based on pilot-assisted timing interpolation according to claim 7, characterized in that, The time-domain correction module includes: A digital high-pass filter is used to separate the second scientific beat frequency signal from a discrete sampled sequence; The sampling mapping module is used to map the instantaneous phase noise sequence to the instantaneous time jitter at the ADC sampling moment; The normalization module is used to normalize the instantaneous time jitter to the sampling period of the analog-to-digital converter, thereby obtaining the fractional delay parameter. ; The time-domain reconstruction module is used to reconstruct the second scientific beat frequency signal in the time domain based on the instantaneous phase noise sequence to obtain the third scientific beat frequency signal.