KR101458610B1 - Method for performing correlation concerning delay tracking and fringe rotation in vlbi correlation subsystem - Google Patents

Abstract

The present invention relates to a correlation processing method for the delay tracking and fringe rotation of VSC (very long baseline interferometery correlation subsystem). The correlation processing method for the delay tracking and fringe rotation of the VSC according to the present invention comprises: a first step in which a data serialized module receives observation data of a celestial body observed in a multi observation station and serializes the same; a second step in which a delay tracking module performs the delay tracking of the observation data received in the multi observation station with a delay prediction parameter applied by a parameter conversion module and corrects a delay time of each observation data; a third step in which a fringe rotation module performs the fringe rotation regarding a frequency phase of each observation data with the delay prediction parameter applied by the parameter conversion module and corrects a fringe rotation phase; a fourth step in which a fast Fourier transform (FFT) module performs the FFT regarding each observation data in which the delay tracking and the fringe rotation are performed; and a fifth step in which a correlation integral module performs the correlation integration for each observation data by using the observation data in which the FFT is performed. In the third step, the fringe rotation module lets the fringe rotation phase jump at an angle of 90° if a bit shift is generated in the delay tracking module.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of correlating delayed tracking of a VCS with a fringe rotation,

The present invention relates to a delay tracking method and a correlation processing method for fringe rotation of a Very Long Baseline Interferometry Correlation Subsystem (VCS), and more particularly, to a very long baseline interferometry correlation (VLBI) The present invention relates to a delay tracking method and a correlation processing method for fringe rotation in a VCS, which can obtain accurate correlation results by performing Fast Fourier Transform (FFT) and correlation processing (Cross-correlation).

VLBI (Very Long Baseline Interferometry) is a radio interference technique that uses a radio telescope far away from each other to obtain an accurate position and image of a celestial object. It records the radio signal received by each radio telescope on a special magnetic tape, By gathering the radio wave signal by using a computer, accurate position and image of the object can be obtained.

Korea Astronomy Observatory and National Astronomical Observatory of Japan (VLBI Exploration of Radio Astrometry (VLBI)), as shown in "2008 Korea-Japan joint VLBI Correlator and Receiver Development Report (Korea Astronomy Observatory, pp.3-100, 2008" Korea-Japan Joint VLBI Correlator (KJJVC) was developed to handle radio wave observation data by using the Korea-Japan Joint VLBI Correlator.

The VLBI Correlation Subsystem (VCS), which is a core configuration of the Korean-Japanese joint VLBI correlator shown in FIG. 1, performs correlation processing with FFT (Fast Fourier Transform) on observation data of up to 16 observation stations, The correlation result of the output channel can be obtained.

The correlation processing of VLBI data such as VCS can deal with signals of very weak celestial bodies than signal system noise unlike general signal processing. Particularly, in order to detect this signal, it is necessary to integrate for a long time after correlation processing to remove random noise of the receiver system which is an analog device.

However, if the correlated data is integrated for a long period of time in the correlator, the amount of data becomes very large, which increases the processing time.

In order to improve the signal to noise ratio (SNR) of the correlation result by finding only the noise added independently at the receiver of each observing station without attenuating the signal from the object, "Very Long Baseline Interferomiter, Ohmsha , pp.35-55, 2000. "Correlation by Delay Change and Doppler's Effect between observation stations for a certain time, for example, 25.6 ms to 102.4 ms, in the correlation system hardware. And correcting the phase change of the values while integrating them.

However, in the above conventional techniques, the correlation result is analyzed by AIPS (Astronomical Image Processing System) to perform more correlation integration than the correlation system, so that the phase is not stabilized. In the analysis of the correlation result, There is a problem that an error is generated.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a VCS system and a VCS system, which are capable of performing delay tracking for arrival signals among distant observing stations through a delay tracking module and a fringe rotation module The purpose of this paper is to provide a correlation tracking method for fringe rotation and delay tracking of VCS which can improve the correlation with observed data by correcting the fringe phase.

However, the object of the present invention is not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, a method of correlating delay tracking and fringe rotation in a Very Long Baseline Interferometry Correlation Subsystem (VCS) according to an embodiment of the present invention is a method in which a data serialization module observes a celestial object observed in multiple observation stations The delay tracking module performs delay tracking on the observation data received from the multiple observation stations with the delay prediction parameters applied through the parameter conversion module to correct the delay time of each observation data, A third step for the fringe rotation module to perform fringe rotation on the frequency phase of each observation data with the delay prediction parameter applied through the parameter conversion module to correct the fringe rotation phase; ) For each observation data for which delay tracking and fringe rotation have been performed, the module performs a fast Fourier transform And a fifth step of performing a correlation integration for each observation data using the FFT-transformed observation data, and in the third step, the fringe rotation module calculates the delay And when the bit shift occurs in the tracking module, the fringe rotation phase is jumped by 90 degrees.

The correlation processing method according to the present invention is characterized in that the phase of the fringe rotation module is aligned with the direction of 90 degrees jumping.

The correlation processing method according to the present invention is characterized in that the parameter conversion module applies delayed prediction parameters as hardware parameters usable in the delay tracking module and the fringe rotation module.

Further, the correlation processing method according to the present invention is characterized in that the delayed prediction parameter is defined by the following relational expression.

Here, sample # indicates the position of the sample in the 1-clock, and T _s indicates the sampling period.

The correlation processing method according to the present invention is characterized in that, in the second step, an initial delay value of delay tracking is defined by the following relational expression.

Here, F _s represents a sampling rate, D _o represents an initial delay value, and floor () represents rounding.

The correlation processing method according to the present invention is characterized in that, in the third step, an initial phase ( ₀ ) of fringe rotation is defined by the following relational expression.

Where φ is the phase of the observed frequency, Fo is the observed frequency, and floor () is the rounding.

The correlation processing method according to the present invention is characterized in that, in the second step, the delay tracking module tracks the delay value while moving by 1 bit with respect to the observation data.

In the correlation processing method according to the present invention, in the third step, the delay tracking is applied at the boundary of the fast Fourier transform segment, and when a bit shift occurs during the fast Fourier transform segment, The shift is characterized by being applied to the next fast Fourier transform segment boundary.

The correlation processing method according to the present invention is characterized in that, when a bit shift occurs, a first bit shift timing interval (T ₀ ) is defined by the following relational expression.

Here, D ₀ represents the initial delay value, and N _clk represents 32 samples per clock.

In addition, the correlation processing method according to the present invention is characterized in that the generated bit shift interval T is defined by the following relational expression.

Where N _clk represents 32 samples per clock.

According to the delay tracking of the VCS (Very Long Baseline Interferometry Correlation Subsystem) of the present invention and the correlation analysis method for the fringe rotation, the delay tracking module and the fringe rotation module in the VCS allow the far- There is an advantage that the accuracy of correlation with the observation data can be improved by correcting the fringe phase and the delay tracking for the arrival signal between the signals.

Brief Description of the Drawings Fig. 1 is a diagram schematically showing a configuration of a very long baseline interferometry (VLBI) correlator.
2 is an exemplary diagram showing the principle of VLBI.
3 is an exemplary diagram showing an example of a general FX (Fourier transform and multiplier) correlator.
FIG. 4 is an exemplary diagram showing an example of an observation signal at each observation station by the Doppler effect. FIG.
Fig. 5 is an exemplary diagram illustrating fringe rotation (stop) in an observation signal for correlation processing.
6 (a) to 6 (d) are exemplary diagrams illustrating fringe rotation and partial bit correction.
7 is a block diagram schematically showing a configuration of a correlation processing unit for delay tracking and fringe rotation in a VCS according to an embodiment of the present invention.
8 is a flowchart illustrating a correlation processing method for delay tracking and fringe rotation according to an embodiment of the present invention.
9 is a diagram showing delay tracking in the VCS.
10 is an exemplary diagram illustrating the application of delay tracking when a bit shift occurs in the middle of an FFT segment in a VCS.
11 is a diagram showing bit shift generation and 90 degree fringe phase jump in the fringe rotation module.
12 is a diagram showing the initial phase determination of the fringe rotation.
13 (a) to 13 (d) are diagrams for explaining a correlation processing method according to the present invention by using a software simulator.
14 (a) to 14 (b) are views showing the results before and after fringe fitting in the VCS correlation result according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description of preferred embodiments of the present invention will be given with reference to the accompanying drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Embodiments in accordance with the concepts of the present invention can make various changes and have various forms, so that specific embodiments are illustrated in the drawings and described in detail in this specification or application. It is to be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms of disclosure, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. As used herein, the terms "comprise", "having", and the like are intended to specify that there is a feature, a number, a step, an operation, an element, a part or a combination thereof, , &Quot; an "," an "," an "

Delay tracking

Long-term line data obtained through very long baseline interferometry (VLBI) between radio telescopes installed in a large number of observation stations greatly changes the delay time due to the earth rotation. Therefore, when the correlation value is integrated, It is necessary to correct the delay time variation.

2 shows an example of the VLBI principle, in which the positions of two observation stations (X, Y) located on the equator of the earth and a radio souce as a celestial object are viewed from the north pole direction. 2, assuming that t = 0 when the angle between the X observation station, the Y observation station, and the center of the earth is 2 alpha, the speed of light is c, the radius of the earth is r, and the propagation source is in the vertical direction of the XY line segment , The delay times τ _g of two observation stations X and Y can be defined by the following relational expression.

[Formula 1]

Here, ωt represents [2π / (24 × 3600)] · t [sec] as the rotational angular velocity. Equation 1 shows that τ _g is one rotation per day and its maximum value is (2r / c) · sinα, and the range that can be observed without entering the shadow of the earth is as follows.

[Formula 2]

FIG. 3 is an example of a typical Fourier transform and multiplier correlator; the Y observing station of FIG. 2 arrives later than the X observing station. Therefore, as shown in FIG. 3, the delay time due to the delay tracking is corrected, the fringe phase due to the fringe rotation of the X observation station and the Y observation station is corrected, and then the Fourier transform and the correlation processing of the two observation station signals are performed can do.

The delay trace can track the delay value by shifting the observation data represented by the digital signal by one bit by using a shift register. Bit shift may implement a delay circuit according to the programmed with (Field Programmable Gate Array) FPGA technology, in the bit shift delay circuit implemented in FPGA BOPP (Begin by T _0, the value of T is assigned a separate control computer of Parameter Period) after the date T ₀ bit, the delay amount in the delay circuit in the, FPGA, and generating a bit-shifted signal every T-bit can be changed every one bit.

Fringe rotation

FIG. 4 is an exemplary diagram showing an observation signal at each observation station by the Doppler effect. As shown in FIG. 4, when the delay time change rate is positive, the Y observation station is gradually getting It may be in a distant state. At this time, the signal received at the Y observation station due to the Doppler effect can be observed at a frequency lower than that of the signal received at the X observation station.

Therefore, as shown in FIG. 5, if the frequency of the received signal of the X observing station is not lowered, correlation with the Y observing station is not generated. Therefore, the fringe phase should be reversed and correlated with the Y observing station.

For example, to perform frequency conversion at the receiver, the signal (f _LO ) from the local oscillator can be multiplied by the observed frequency (f _RF ) to convert to the intermediate frequency of the frequency f _RF + f _LO or f _RF -f _LO . It is the reverse rotation (or stop) or fringe phase correction of the fringe phase to change the oscillation frequency as much as the effect of the Doppler effect, in addition to the delay tracking before performing the correlation integration.

The delay time τ _g changes because the earth rotates and changes between the object and the observing station, and the observed amount of change in the celestial signal phase can be a function of the observation frequency f. If the phase change frequency is referred to as fringe rotation frequency F _r , it can be defined by the following relational expression.

[Formula 3]

Partial bit correction

Since the fringe rotation frequency F _r continuously changes on the frequency axis, the correlation processing is performed on the time axis, and since the observation signal has a bandwidth, the fringe rotation correction on the time axis does not correct only the single frequency, A phase error called a partial bit of the correlation value may be generated and the correlation value may be lowered. Therefore, in the correlation processing apparatus, when τ _g is made to be 1/2 bit difference from the predicted value, a 1-bit shift is generated in the delay unit in the program, and at the same time, the value of the fringe rotation phase register is jumped by 90 degrees.

Phase correction for the fringe rotation is performed at the beginning and center of the bandwidth, and when performed at the beginning of the bandwidth, the phase change becomes severe at the end of the bandwidth, causing a loss.

Figs. 6 (a) to 6 (d) illustrate exemplary fringe rotation and partial bit correction. Fig. 6 (a) shows frequency versus phase when the correction for fringe rotation is performed at the bandwidth center, 6 (b) to 6 (d) show the phase difference for each frequency together with the change of the time t. In the drawing, the solid line represents a case of shifting the fringe rotation phase by 90 degrees at the same time, and the dotted line represents a case where the shift occurs by one bit difference without performing the 90 degree jump.

As shown in Figure 6 (a), when the time that when the phase difference is zero in the observation zone _{t = 0, t = t s} / 2 (1/2 bit time) by ① and the operation, t = t _s / 2 The phase of f = 0 to -45 degrees and the phase of f = f _B to +45 degrees are changed. At this time, if the bit is shifted by one bit, the phase does not change when f = 0 and changes by -180 degrees at f = fB as in the case of?.

This is the reason why the sampling frequency is twice the observation bandwidth (2f _B ) and the phase is inverted by the bit shift at f = f _B.

If the + 90 ° phase jump of ③ is performed at the same time as ②, the phase changes by + 90 degrees around the whole band, and then the phase change shown by ④dp from t = t _s / 2 to t _s is performed.

Figure 6 Figure 6 (b) to Fig. 6 (d) is, for each _{time, f = 0, f B /} 2, represents the phase change with respect to f _B. As shown in the figure, it can be seen that the phase difference of the solid line is remarkably small as compared with the dotted line. This method is simple and the area of the phase difference becomes small, and the coherence loss of the correlation processing system can be reduced to about 3.4%.

<Examples>

FIG. 7 is a block diagram schematically illustrating the configuration of a correlation processing unit for delay tracking and fringe rotation in a VCS according to an embodiment of the present invention, and FIG. 8 is a flowchart illustrating a correlation processing method for delay tracking and fringe rotation.

The correlation processing unit 100 for delay tracking and fringe rotation in the VCS according to the embodiment of the present invention includes a data serialization module 110, a parameter conversion module 120, a delay tracking module 130, a fringe rotation module 140, A fast Fourier transform module 150 and a correlation integration module 160. [

Referring to the drawing, in the data serialization module 110, 1 Gsps ^{8 (1} Gsps) of observation data input from multiple observation stations (not shown) The data is serialized into 4 Gsps x 2 bits x 1-stream data in x2 bit x4-stream (S101).

In the VCS of the present invention, the delay prediction parameter is transmitted through a separate control computer or a control unit in units of a set correlation integration time (for example, 2.048 sec). In the parameter conversion module 120, To the hardware parameters usable in the fringe rotation module 140, and this parameter can be transferred to each module designed in the FPGA in units of 1.02 msec (S102).

Is converted to a hardware parameter of 102.4 ms, which is an internal parameter period (iPP) applied through the parameter conversion module 120, and can be calculated through the following relational expression.

[Formula 4]

At this time, t can be defined by the following relation.

[Formula 5]

Here, τ (t) is a geometric delay value (τ _{g in} FIG. 3), τ '(t) is a first derivative of a geometric delay value (t) The second derivative value of the value ((t)), sample # indicates the position of the sample at the 1-clock, and T _s indicates the sampling period.

Each part of the hardware operates on a clock by hardware parameter basis and each operation result can be applied to the observed data after being latched at the boundary of the FFT segment.

The delay tracking module 130 performs delay tracking on the observation data received from the multiple observing stations using the delay prediction parameters applied through the parameter conversion module 120. The delay tracking module 130 calculates 1 The delay value is tracked while moving bit by bit, and the delay time of each observation data can be corrected (S103).

The calculation of the initial delay value D ₀ used for delay tracking is defined by the following relation and can be calculated from the delayed prediction value.

[Formula 6]

Where D is the product of the geometric delay value τ (t) and the sampling rate (F _s ), F _s is the sampling rate, D _o is the initial delay value, and floor () is the rounding.

The first bit shift timing interval T ₀ is defined by the following relationship.

[Equation 7]

Here, D ₀ represents the initial delay value, and N _clk represents 32 samples per clock.

Further, the interval T of the bit shift can be defined through the following relationship.

[Equation 8]

Where N _clk represents 32 samples per clock.

Thereafter, the fringe rotation module 140 performs fringe rotation on the frequency phase of each observation data using the delay prediction parameter applied through the parameter conversion module 120 to correct the fringe rotation phase (S104).

In the case of fringe rotation, the initial phase &lt; RTI ID = _0.0 &gt; ₀ &lt; / RTI &gt;

[Equation 9]

Here, φ represents the phase of the observed frequency, F ₀ represents the observation frequency, floor () represents rounding (rounding), Scl represents a scaling factor for integer conversion of 232, And the number of bit shifts, respectively.

The delay tracking algorithm described above can be applied as shown in FIG. In Fig. 9, the straight line is the ideal delay trace, and the step shape represents the delay trace applied and calculated in the actual VCS. T represents the case where the acceleration is greater than 0 (when the actual τ "> 0) in order to reflect this as an acceleration period.

The delay tracking can be applied at the boundaries of the FFT segment, as shown in FIG. If a bit shift occurs during an FFT segment, that bit shift can be applied to the boundary of the next FFT segment. In addition, when the length of the FFT segment is larger than the bit shift period, two or more sample shifts are generated.

Further, when a bit shift occurs in the delay tracking and fringe rotation module 140, a 90 degree phase jump can be applied as shown in FIG. In the drawing,? Represents the phase acceleration.

In particular, when bit shift occurs in the delay tracking, if the direction of the 90-degree jump is reversed in the function of jumping the phase of the fringe rotation module 140 by 90 degrees, the fringe is not detected and the cross power spectrum as a whole is adversely affected . Therefore, in the present invention, the phase of the fringe rotation module 140 is aligned with the direction of 90 degrees jumping.

As described above, since the fringe phase of the fringe rotation must be jumped 90 degrees when the bit shift occurs in the delay tracing, it must have information of the phase jump that occurred before. As shown in Fig. 12, when the correlation processing is started, ₀ iPP is entered, and the D ₀ value of Equation 6, which is the phase value of delay tracking, is input to n, which is the total number of bit shift occurrences in Equation 9, The D ₀ value should be applied even in 1 ipP after 102.4 ms.

Therefore, the initial phase? ₀ of the fringe rotation can be calculated by the following relationship.

[Equation 10]

8k (8192) is generated for each observation data subjected to the delay tracking and fringe rotation through the delay tracking module 130 and the fringe rotation module 140 in the Fast Fourier Transform (FFT) module 150, After performing fast Fourier transform of ~ 256k (262144) -points (S105), the correlation integration module 160 can perform correlation integration on each observation data using fast Fourier transformed observation data (S106) .

<Experimental Example>

13 (a) to 13 (d) are diagrams for explaining a correlation processing method according to the present invention by using a software simulator. The correlation value and the correlation fringe phase change were confirmed using the value of n (the total number of bit shifts generated in the delay trace) together with the D ₀ value.

The left side of the drawing shows the visibility (blue real number, red imaginary number), and the right side shows the phase.

13 (a) to 13 (d), when the simulation is performed by arbitrarily adding 0, 1, 2, and 3 together with the D ₀ value, it can be seen that the feasibility and the phase at that time are rotated by 90 degrees . This uses the D ₀ value to determine the phase of the fringe rotation, so that when the fringe phase in the fringe rotation module with the delay tracking is applied to each FFT segment, the fringe rotation is performed while maintaining the previous phase value, And it can be confirmed that a normal value is output.

Correlation processing tests were performed on scan267 (about 19 minutes observation data) based on the observation station for the data of Table 1 for KVN 3 stations (YS, US, TN).

Item Contents Observation frequency 22.098 GHz Observation data r11027b_No00267 Observation mode C5 (16 MHz BW, 16 stream) Correlation processing stream 5, 9 Correlation processing baseline KVN Yonsei, Ulsan (US), Tamra (TN) Integral time 2.048 seconds Data Analysis iplot SW, AIPS Correlation output integral 32ch integration in the frequency direction
Output 8129ch by 256ch

Correlation processing is performed for stream 9 among 16 streams of C5 mode. The correlation result is analyzed by AIPS, and 8192 output channels are integrated by 16 channels to output 512 channels.

14 (a) and 14 (b) show correlation results before and after application of fringe fitting in AIPS. As can be seen from FIG. 14 (a), the phase slowly changes and stabilizes within the bandwidth, It can be confirmed that the amplitude bandwidth is stable within the bandwidth.

Further, as shown in Fig. 14 (b), it is confirmed that the phase after fringe fitting is determined to be constant.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. will be. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

100: Correlation processor
110: Data serialization module
120: Parameter conversion module
130: delay tracking module
140: Fringe rotation module
150: FFT module
160: Correlation integral module

Claims (10)

A data serialization module for receiving observation data of a celestial object observed at multiple observation stations and serializing the data;
A second step of the delay tracking module performing delay tracking on the observation data received at the multiple observation stations with the delay prediction parameters applied through the parameter conversion module to correct the delay time of each observation data;
A third step of the fringe rotation module correcting the fringe rotation phase by performing fringe rotation on the frequency phase of each observation data with the delay prediction parameter applied through the parameter conversion module;
A fourth step of a fast Fourier transform (FFT) module performing a fast Fourier transform on each observation data subjected to delay tracking and fringe rotation; And
And a fifth step of performing a correlation integration on each observation data using the fast Fourier transformed observation data by the correlation integration module,
In the third step, the fringe rotation module jumps the fringe rotation phase by 90 degrees when a bit shift occurs in the delay tracking module,
Wherein a direction of jumping 90 degrees with a phase of the fringe rotation module is made coincident with a direction of a fringe rotation of the fringe rotation module.
delete The method according to claim 1,
Wherein the parameter conversion module applies delayed prediction parameters as available hardware parameters in the delay tracking module and the fringe rotation module.
The method of claim 3,
Wherein the delay prediction parameter is defined by the following relation: &lt; EMI ID = 17.0 &gt;

(T) is a geometric delay value (tau _{g in} Fig. 3), τ '(t) is a first order derivative of the geometric delay value τ (t) a second order derivative, of the sample # delay value (τ (t)) represents the position of the sample as a 1-clock, T _s is the sampling period)
The method according to claim 1,
Wherein in the second step, the initial delay value of the delay trace is defined by the following relationship: &lt; EMI ID = 17.1 &gt;

(Where D is the geometric delay value τ (t) multiplied by the sampling rate (F _s ), F _s is the sampling rate, D _o is the initial delay value, and floor ()
The method according to claim 1,
Wherein in the third step, the initial phase ( ₀ ) of the fringe rotation is defined by the following relation: &lt; EMI ID = 17.1 &gt;

(Where φ is the phase of the observed frequency, Fo is the observation frequency, and floor () represents the rounding)
The method according to claim 1,
Wherein, in the second step, the delay tracking module tracks the delay value while moving by 1 bit with respect to the observation data.
The method according to claim 1,
In the third step, delay tracking is applied at the boundary of a fast Fourier transform segment,
Wherein when a bit shift occurs during a fast Fourier transform segment, the generated bit shift is applied to the next fast Fourier transform segment boundary.
The method according to claim 1,
Wherein when a bit shift occurs, a first bit shift timing interval (T ₀ ) is defined by the following relation:

(Where D ₀ is the initial delay value, and N _clk represents 32 samples per clock)
The method according to claim 1,
Wherein the generated bit shift interval (T) is defined by the following relational expression.

(Where N _clk represents 32 samples per clock)

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