KR102187064B1 - Method for calculating filter length - Google Patents

Abstract

An embodiment includes calculating a filter parameter; Calculating a first state filter length using the calculated filter parameter; Setting a second state filter length and a third state filter length to be the same as the first state filter length; Calculating the length of the second state filter which is one of N times and 1/N times the length of the first state filter so as to be smaller than the length of the first state filter; Calculating the third state filter length which is one of M times and 1/M times the second state filter length to be smaller than the second state filter length; Disclosed is a method of measuring a filter length comprising the step of comparing a reference value and an error-compensated value to determine the calculated first state filter length, the calculated second state filter length, and the calculated third state filter length. .

Description

How to measure filter length {METHOD FOR CALCULATING FILTER LENGTH}

The embodiment relates to a filter length measurement method.

GPS appeared in the late 1980s and provides usefulness in various fields such as navigation, positioning, surveying, and time. Among them, the viewpoint related to the present invention has contributed to innovative development in the IT field including mobile communication by providing very excellent performance even in its accuracy. As a result, the expansion of the field of application and the development of the use technology are deepening the dependence on GPS. However, 　GPS is a satellite developed for military purposes by the US Department of Defense, so there is no guarantee that it can always be stably provided in Korea.

In addition, this navigation signal, which is vulnerable to radio interference due to the nature of radio waves, is a situation where the same thing as communication disruption occurs every year in the domestic communication network using GPS in the vicinity of Gyeonggi Province due to the intentional interference of North Korea. In addition, if a clock mounted on a satellite is abnormal, it takes several hours or more to detect and cope with it on the ground.

Accordingly, there is a disadvantage that the GPS signal is vulnerable to unintentional or deliberate jamming because it has a relatively very low signal level when received on the ground.

In addition, when the GPS signal is disturbed, the GPS signal receiver loses the reference timing signal, and the oscillation unit built in the receiver is freely driven, so there is a problem that the timing error increases as time passes. Accordingly, technology development for a method to maintain timing accuracy is in progress.

The embodiment provides a method of measuring filter length.

In addition, a filter length measurement method with improved precision is provided.

In addition, it provides a filter length measurement method that improves the stability of a holdover state.

The problems to be solved in the embodiments are not limited thereto, and the objectives and effects that can be grasped from the solutions or embodiments of the problems described below are also included.

A method of measuring a filter length according to an embodiment includes calculating a filter parameter; Calculating a first state filter length using the calculated filter parameter; Setting a second state filter length and a third state filter length to be the same as the first state filter length; Calculating the second state filter length, which is one of N times and 1/N times the first state filter length to be smaller than the first state filter length; Calculating the third state filter length which is one of M times and 1/M times the second state filter length to be smaller than the second state filter length; And determining the calculated first state filter length, the calculated second state filter length, and the calculated third state filter length by comparing a reference value and an error-compensated value.

The filter parameter may be a q-parameter according to a clock amount.

In the step of calculating the first state filter length,

The first state filter length may be calculated by Equation 1 below.

[Equation 1]

,

은 백색 주파수 변조(WFM: White Frequency Modulation) 클럭 잡음,

는 랜덤 워크 주파수 변조(RWFM: Random Work Frequency Modulation) 클럭 잡음,

은 측정 잡음의 분산이다)(Here, the first state filter length is

,

Is the white frequency modulation (WFM) clock noise,

Is the Random Work Frequency Modulation (RWFM) clock noise,

Is the variance of the measurement noise)

In the step of calculating the second state filter length,

N is a value at which the error is minimum,

In the step of calculating the third state filter length,

The M may be a value at which an error is minimized.

The reference value may satisfy Equation 2.

[Equation 2]

는 위상 오프셋,

은 주파수 오프셋,

는 주파수 드리프트, 그리고

는 추정 에러 확률)(here,

Is the phase offset,

Is the frequency offset,

Is the frequency drift, and

Is the estimated error probability)

The step of calculating the second state filter length that is any one of N times and 1/N times the first state filter length so as to be smaller than the first state filter length,

The second state filter length, which is any one of N times and 1/N times the first state filter length, is compared with a visual error value of the first state filter length, and N is increased in a direction in which the visual error value is small. The second state filter length can be calculated.

Calculating the third state filter length, which is one of M times and 1/M times the second state filter length so as to be smaller than the second state filter length

The visual error value of the third state filter length, which is one of M times and 1/M times the second state filter length, is compared with the second state filter length, and M is increased in a direction in which the visual error value is small. The third state filter length can be calculated.

The error-compensated value may be an output value filtered using the first to third state filter lengths.

After the step of determining the calculated first state filter length, the calculated second state filter length, and the calculated third state filter length by comparing a reference value and an error compensated value, the error compensated value is If it is less than the reference value, the first state filter length, the calculated second state filter length, and the calculated third state filter length are determined, but if the error-compensated value is greater than the reference value, the filter parameter is calculated. You can go back to the stage.

According to an embodiment, a filter length measurement method may be implemented.

In addition, a filter length measurement method with improved precision can be manufactured.

In addition, a filter length measurement method that improves the holdover state stability can be manufactured.

Various and beneficial advantages and effects of the present invention are not limited to the above-described contents, and may be more easily understood in the course of describing specific embodiments of the present invention.

1 is a diagram illustrating a holdover state in connection with a method for measuring a filter length,
2 is a flowchart of a method for measuring a filter length according to an embodiment.

The present invention is intended to illustrate and describe specific embodiments in the drawings, as various changes may be made and various embodiments may be provided. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers, such as second and first, may be used to describe various elements, but the elements are not limited by the terms. These terms are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a second component may be referred to as a first component, and similarly, a first component may be referred to as a second component. The term and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. Should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Does not.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, but the same reference numerals are assigned to the same or corresponding components regardless of the reference numerals, and redundant descriptions thereof will be omitted.

1 is a diagram illustrating holdover in connection with a method of measuring a filter length.

Referring to FIG. 1, as described above, the satellite 10 provides a space navigation signal (GPS, hereinafter described as a GPS signal), and the GPS signal is used for time synchronization in various fields. For example, the GPS signal may be a 1-second pulse signal, and will be described below based on this.

The satellite 10 may include a clock having time information. For example, the satellite 10 has an atomic clock mounted therein, and the atomic clock is synchronized with the Universal Coordinated Time (UTC). Accordingly, since the satellite 10 transmits the GPS signal reflecting the synchronized world agreement to the ground, the GPS signal can be received through the signal receiver 20 on the ground and used as a reference synchronization signal. In addition, in the synchronous mode, which can be called a normal state, synchronization is maintained using a GPS signal, but in an abnormal holdover state, a correction value is made using time difference information between the comparison signal of the oscillator and the GPS signal as described later. May be calculated, and an estimate value for a frequency offset and a drift may be calculated using the information on the correction value and reflected to the oscillator. Here, the holdover state may be a case in which the oscillator loses a control input and operates with data obtained during synchronization, so that a time difference exists between the GPS signal and the comparison signal. In addition, the holdover state may start when the comparison signal, which is an output of the oscillator, does not reflect an external reference signal (eg, a GPS signal), and may end when the output of the oscillator recovers to be driven in a synchronous mode.

Next, the signal receiver 20 may include an oscillation unit 21, a comparison unit 22, a correction unit 23, a filter unit 24, a switch unit 25, and a converter unit 26.

First, the oscillator 21 may generate a comparison signal corresponding to a GPS signal. Like the GPS signal, the comparison signal may be a 1-second pulse. Further, the oscillator 21 may include, as an oscillator, an oven controlled crystal oscillator (OCXO) or rubidium, but is not limited thereto.

The comparison unit 22 may compare the GPS signal and the comparison signal. In this case, the comparison unit 22 may compare the GPS signal and the comparison signal due to the presence of a phase difference between the GPS signal and the comparison signal. For example, the comparison unit 22 may provide a control signal to the switching unit 25 such that the GPS receiver operates in a synchronous mode when there is no phase difference, and in a holdover state when there is a phase difference.

The correction unit 23 may receive phase difference information between a comparison signal that is a pulse of 1 second and a GPS signal from the comparison unit 22, and calculate a correction value using the phase difference information. Specifically, the correction unit 23 may calculate a phase correction value that matches the time of the GPS signal using an algorithm such as a moving average in order to correct the phase of the oscillator 21. In this way, the phase correction value calculated from the correction unit 23 can be used to directly control the oscillator 21 in the synchronous mode. As described above, the phase correction value may be directly connected from the correction unit 23 to the switch unit 25 in the synchronous mode. In addition, the phase correction value is used by the filter unit 24 to estimate the coefficient of the filter in the holdover state.

The filter unit 24 may include an unbiased finite impulse response (UFIR) filter to calculate values for parameters for driving control of the oscillator 21 from the correction unit in the holdover state. In addition, the calculated parameters may be provided to the oscillation unit 21 through the switch unit 25 and the converter unit 26. The parameters for driving control of the oscillator 21 described above are, for example, major factors that affect the performance of the oscillator, and may include frequency offset, drift (aging), temperature stability, and the like.

The switch unit 25 may switch according to a synchronous mode or a holdover state. Specifically, the switch unit 25 may switch whether to apply the parameter calculated through the filter unit 24 to the oscillation unit 21.

For example, the switching unit 25 may be connected to the converter unit 26 and the oscillator unit 21 without passing through the filter unit 24 through the correction unit 23 in the synchronous mode. Accordingly, by not passing through the filter unit 24, since a parameter that affects the driving control of the oscillator 21 is not provided to the oscillator 21, synchronization using a GPS signal can be maintained.

In contrast, the switching unit 25 may be connected to the converter unit 26 and the oscillator unit 21 through the filter unit 24 through the correction unit 23 in the holdover state. Accordingly, a parameter affecting the driving control of the oscillator 21 is provided to the oscillator 21 to compensate for the timing error of the GPS signal that increases as time passes, and even if the GPS signal is disturbed by jamming or the like, the signal receiver 20 The timing accuracy can be maintained by blocking) from free driving.

The converter unit 26 may convert a parameter provided through the filter unit 24 and the switch unit 25 into an analog signal so that the oscillator unit 21 can recognize the error in order to compensate for the error. The converter unit 26 may include a digital-analog converter (DAC).

2 is a flowchart of a method for measuring a filter length according to an embodiment.

The filter unit 24 may be an Unbiased Finite Impulse Response (UFIR) filter as described above. In addition, this filter is a three state applied filter, and can estimate three coefficients, which are phase offset, frequency offset, and frequency drift, and use individual filters for each of the estimated coefficients. In addition, a phase offset can be estimated in one state, a frequency offset can be estimated in a two state, and a frequency drift can be estimated in a three state.

Referring to FIG. 2, the method of measuring a filter length according to an embodiment includes calculating a filter parameter (S31), calculating a first state filter length using the calculated filter parameter (S32), and the first state filter. Step of setting the second state filter length and the third state filter length equal to the length (S33), which is one of N times and 1/N times the first state filter length so as to be smaller than the first state filter length Calculating the second state filter length (S34), calculating the third state filter length which is one of M times and 1/M times the first state filter length so as to be smaller than the first state filter length Comprising a step (S35) and determining the calculated first state filter length, the calculated second state filter length, and the calculated third state filter length by comparing a reference value and an error-compensated value (S36). do.

First, it is possible to calculate the filter parameter (S31). The filter parameter may be calculated as a q-parameter value according to a clock specification in the oscillator 21. In relation to these Q-parameters, the manufacturer of the oscillator 21 provides information on the phase noise different from the frequency and the Allan variance for the frequency stability according to the average time for the clock specification, and the state used to obtain the filter length. You can convert the Allan variance from the bar clock specification, where the matrix is a cue-parameter, to a cue-parameter. In this case, the clock specification may be different depending on the oscillator 21 and may be pre-stored data. Accordingly, the clock specification may calculate a queue parameter value using an Allan variance value.

)는 아래 수학식 1에 의해 산출될 수 있다.The first state filter length may be calculated using the calculated filter parameter (S32). Specifically, the first state filter length (

) Can be calculated by Equation 1 below.

,

은 백색 주파수 변조(WFM: White Frequency Modulation) 클럭 잡음,

는 랜덤 워크 주파수 변조(RWFM: Random Work Frequency Modulation) 클럭 잡음,

은 측정 잡음의 분산이다.Here, the first state filter length is

,

Is the white frequency modulation (WFM) clock noise,

Is the Random Work Frequency Modulation (RWFM) clock noise,

Is the variance of the measurement noise.

)와 동일하게 제2 상태 필터 길이(

), 제3 상태 필터 길이(

)를 설정할 수 있다(S33).And the first state filter length (

) Equal to the second state filter length (

), the third state filter length (

) Can be set (S33).

Accordingly, the initial state filter length may be set by Equation 2 below.

, 제2 상태 필터 길이는

로, 제3 상태 필터 길이로

나타낸다.Here, the first state filter length is

, The second state filter length is

To the third state filter length

Show.

)의 방향성을 설정하기 위하여 제1 상태 필터 길이(

)의 N배 및 1/N배(이하 2배 및 1/2배로 설명 함) 중 어느 하나인 제2 상태 필터 길이(

)를 산출하고, 제1 상태 필터 길이와 산출된 제2 상태 필터 길이의 시각 오차 값을 비교하여 더 작은 시각 오차 값을 갖는 값에 대해서 방향성을 설정하고, 제2 상태 필터 길이를 산출할 수 있다(S34). 즉, 제2 상태 필터 길이를 제1 상태 필터 길이의 2배로 산출하는 경우에 시각 오차가 더 작으면 방향성은 증가하는 쪽이고, 반대로 시각 오차 값이 더 크면 방향성은 감소하는 쪽이다. 이로써, 방향성이 설정되면(예컨대, 증가하는 쪽) N의 값을 증가시켜가며 시각 오차가 최소가 되는 값으로 N의 값을 결정할 수 있다. 그리고 제2 상태 필터 길이를 산출할 수 있다.And the second state filter length (

To set the directionality of the first state filter length (

) Of N times and 1/N times (hereinafter referred to as 2 times and 1/2 times), which is the length of the second state filter (

), and comparing the visual error value of the first state filter length and the calculated second state filter length to set a directionality for a value having a smaller visual error value, and calculate the second state filter length. (S34). That is, when the second state filter length is calculated as twice the length of the first state filter, if the visual error is smaller, the directionality increases, and when the visual error value is larger, the directionality decreases. As a result, when the directionality is set (eg, the increasing side), the value of N may be determined as a value at which the visual error is minimized while increasing the value of N. In addition, the second state filter length may be calculated.

)의 방향성을 설정하기 위해 먼저 M배 및 1/M배(이하, 2배 및 1/2배로 설명함) 중 어느 하나인 제3 상태 필터 길이(

)를 산출하고, 제2 상태 필터 길이와 산출된 제3 상태 필터 길이의 시각 오차 값을 비교하여 더 작은 시각 오차 값을 갖는 값에 대해서 방향성을 설정하고, 제3 상태 필터 길이를 산출할 수 있다(S35). 즉, 제2 상태 필터 길이의 2배로 산출하는 경우에 시각 오차 값이 더 작으면 방향성은 증가하는 쪽이고 더 크면 방향성은 감소하는 쪽이다. 이로써, 방향성이 설정되면 M의 값을 증가시켜가며 시각 오차가 최소가 되는 값으로 M의 값을 결정할 수 있다. 그리고 제3 상태 필터 길이를 산출할 수 있다.In addition, the third state filter length (

In order to set the directionality of ), first, the third state filter length (which is one of M times and 1/M times (hereinafter, described as 2 times and 1/2 times)) (

), and comparing the visual error value of the second state filter length and the calculated third state filter length to set a directionality for a value having a smaller visual error value, and calculate the third state filter length. (S35). That is, in the case of calculating as twice the length of the second state filter, if the visual error value is smaller, the directionality increases, and if it is larger, the directionality decreases. Accordingly, when the directionality is set, the value of M is increased, and the value of M can be determined as a value at which the visual error is minimized. And it is possible to calculate the third state filter length.

)을 비교하여 보상이 적절하게 이루어졌는지를 판단 할 수 있다.(S36)In addition, the output value of the filter unit after filtering using the calculated first to third state filter lengths as described above is a value for which an error is compensated, and the error compensated value and a reference value (

) Can be compared to determine whether the compensation has been properly performed (S36)

)은 아래 수학식 3을 만족할 수 있다.Reference value (

) May satisfy Equation 3 below.

는 위상 오프셋,

은 주파수 오프셋,

는 주파수 드리프트이며 이러한 값들은 클럭 사양에 나와 있는 값들을 사용하고,

는 추정 에러 확률이다.here,

Is the phase offset,

Is the frequency offset,

Is the frequency drift and these values use the values given in the clock specification,

Is the estimated error probability.

)은 0.2 이하로 적용될 수 있으며, 예컨대, 0.1(10 % 에러)로 적용될 수 있다.Estimated error probability (

) May be applied to 0.2 or less, for example, 0.1 (10% error).

)보다 작은 경우에 상기 산출된 제1 상태 필터 길이, 상기 산출된 제2 상태 필터 길이 및 상기 산출된 제3 상태 필터 길이가 타당하다고 판단할 수 있다. And the error-compensated value (filter output value after filtering) is the reference value (

), it may be determined that the calculated first state filter length, the calculated second state filter length, and the calculated third state filter length are valid.

)보다 큰 경우에 산출된 각 필터 길이가 타당하지 않다고 결정하고,

값을 조절하여 기 기술한 단계(S31 내지 S36)를 다시 수행한다. In contrast, the error-compensated value is the reference value (

If it is greater than ), it is determined that the calculated length of each filter is not valid,

By adjusting the value, the previously described steps (S31 to S36) are performed again.

Accordingly, the method for measuring the filter length according to the embodiment is required by estimating and compensating the frequency offset and drift values that affect the synchronization performance of the oscillator using the UFIR filter when the signal receiver receiving the GPS signal is in the holdover state. High-precision time synchronization can be maintained. In addition, it is possible to improve the precision for maintaining the time synchronization required in the holdover state, and thus this method can be usefully used in mobile communication base stations, power systems, and defense-related systems.

The term'~ unit' used in this embodiment refers to software or hardware components such as field-programmable gate array (FPGA) or ASIC, and'~ unit' performs certain roles. However,'~ part' is not limited to software or hardware. The'~ unit' may be configured to be in an addressable storage medium or may be configured to reproduce one or more processors. Thus, as an example,'~ unit' refers to components such as software components, object-oriented software components, class components and task components, processes, functions, properties, procedures , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, database, data structures, tables, arrays, and variables. The components and functions provided in the'~ units' may be combined into a smaller number of elements and'~ units', or may be further divided into additional elements and'~ units'. In addition, components and'~ units' may be implemented to play one or more CPUs in a device or a security multimedia card.

The embodiments have been described above, but these are only examples and do not limit the present invention, and those of ordinary skill in the field to which the present invention belongs are not illustrated above within the scope not departing from the essential characteristics of the present embodiment. It will be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be modified and implemented. And differences related to these modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

Claims (9)

Calculating a filter parameter of an oscillator generating a comparison signal to correct a time difference with the GPS signal;
Calculating a first state filter length using the calculated filter parameter;
Setting a second initial state filter length and a third initial state filter length to a value equal to the calculated first state filter length as an initial state filter length;
Calculating a second state filter length that is one of N times and 1/N times the first state filter length so as to be smaller than the first state filter length having the same length as the second initial state filter length;
Calculating a third state filter length that is one of M times and 1/M times the second state filter length to be smaller than the calculated second state filter length; And
Comprising the step of comparing the reference value and the error compensated value to determine the calculated first state filter length, the calculated second state filter length, and the calculated third state filter length,
The N and M are 2,
The error-compensated value is an output value after filtering using the calculated first state filter length, the calculated second state filter length, and the calculated third state filter length,
The reference value satisfies Equation 2,
In the step of calculating the second state filter length, the second initial state filter length is converted to the calculated second state filter length,
In the step of calculating the third state filter length, the third initial state filter length is converted into the calculated third state filter length.
[Equation 2]

(here,

Is the phase offset,

Is the frequency offset,

Is the frequency drift, and

Is the estimated error probability)
The method of claim 1,
The filter length calculation method wherein the filter parameter is a q-parameter according to a clock amount.
The method of claim 1,
In the step of calculating the first state filter length,
The filter length calculation method of the first state filter length is calculated by Equation 1 below.
[Equation 1]

(Here, the first state filter length is

,

Is the white frequency modulation (WFM) clock noise,

Is the Random Work Frequency Modulation (RWFM) clock noise,

Is the variance of the measurement noise)
The method of claim 1,
In the step of calculating the second state filter length,
N is a value at which the error is minimum,
In the step of calculating the third state filter length,
The filter length calculation method where M is a value at which the error is minimum.

delete The method of claim 1,
The calculated second state filter length is a value calculated in a direction in which a visual error value between any one of N times and 1/N times the first state filter length and the first state filter length is small.
The method of claim 1,
The calculated third state filter length is a value calculated in a direction in which a visual error value between any one of M times and 1/M times the second state filter length and the self-calculated second state filter length is small.
The method of claim 1,
The error-compensated value is an output value filtered using the first state filter length to the third state filter length.
The method of claim 1,
After comparing the reference value and the error-compensated value to determine the calculated first state filter length, the calculated second state filter length, and the calculated third state filter length,
If the error-compensated value is less than the reference value, it is determined as the first state filter length, the calculated second state filter length, and the calculated third state filter length,
When the error-compensated value is greater than the reference value, the method of calculating the filter length returns to the step of calculating the filter parameter.

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