CN103592645A

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Info

Publication number: CN103592645A
Application number: CN201310593940.1A
Authority: CN
Inventors: 陈镜; 卫青春; 刘兵; 白秀茹; 夏烨巍; 孙悦; 姚剑; 赵向阳; 刘振芳; 高跃清; 陈旸; 师本慧
Original assignee: CETC 54 Research Institute
Current assignee: CETC 54 Research Institute
Priority date: 2013-11-22
Filing date: 2013-11-22
Publication date: 2014-02-19
Anticipated expiration: 2033-11-22
Also published as: CN103592645B

Abstract

Translated fromChinese

本发明公开了一种伪随机码调相连续波雷达速度模糊解算方法，它涉及连续波雷达领域中用作对目标速度进行测量。它是一种距离不模糊、速度模糊的设计方法，采用参差伪随机码对载波进行相位调制，并交替轮法，利用两次测量到的目标速度余数进行速度模糊解算，从而可以确定目标的真实速度。该方法保证了在雷达量程范围内距离测量是不模糊的，从而可以通过距离分段目标检测提高雷达对远处目标的探测能力，可以通过距离-灵敏度控制方法降低因近处地、海杂波引起的虚警，提高雷达在复杂环境中对慢速目标的检测能力。The invention discloses a pseudo-random code phase modulation continuous wave radar velocity fuzzy solution method, which relates to the field of continuous wave radar and is used for measuring the target velocity. It is a design method of unambiguous distance and ambiguous speed. It uses staggered pseudo-random codes to modulate the phase of the carrier, and uses the alternate wheel method to solve the speed ambiguity by using the remainder of the target speed measured twice, so that the target can be determined. real speed. This method ensures that the distance measurement is not ambiguous within the range of the radar, so that the detection ability of the radar for distant targets can be improved through the range-segmented target detection, and the distance-sensitivity control method can be used to reduce the distance caused by nearby ground and sea clutter. The false alarms caused by the radar improve the detection ability of the radar for slow targets in complex environments.

Description

Translated fromChinese

一种伪随机码调相连续波雷达速度模糊解算方法A Velocity Fuzzy Resolution Method for Phase Modulation Continuous Wave Radar with Pseudo-random Code

技术领域technical field

本发明涉及在连续波伪随机码调制雷达领域中的一种用于解算目标速度的方法，特别适用于小型化伪随机码调制连续波雷达的速度测量。The invention relates to a method for calculating target velocity in the field of continuous wave pseudo-random code modulation radar, and is especially suitable for speed measurement of miniaturized pseudo-random code modulation continuous wave radar.

背景技术Background technique

目前，在国内外伪随机码调制连续波雷达中采用多普勒目标检测体制，没有速度模糊，但距离模糊严重，其优点是在多普勒较高的检测区是无杂波区，检测性能优越，但在多普勒较底的检测区，杂波、目标经距离相关后往往混叠在一起，难以区分。At present, the Doppler target detection system is adopted in domestic and foreign pseudo-random code modulated continuous wave radars. There is no velocity ambiguity, but the distance ambiguity is serious. Superior, but in the lower Doppler detection area, clutter and targets are often aliased together after distance correlation, making it difficult to distinguish.

发明内容Contents of the invention

本发明所要解决的就是在雷达量程范围内距离不模糊，而速度模糊的问题，采用参差伪随机码对载波进行相位调制，并交替轮法，利用两次测量到的目标速度余数进行速度模糊解算，从而可以确定目标的真实速度。该方法保证了在雷达量程范围内距离测量是不模糊的，从而可以通过距离分段目标检测提高雷达对远处目标的探测能力，可以通过距离-灵敏度控制方法降低因近处地、海杂波引起的虚警，提高雷达在复杂环境中对慢速目标的检测能力。What the present invention is to solve is the problem that the distance is not ambiguous but the velocity is ambiguous within the range of the radar. The phase modulation of the carrier wave is carried out by using the staggered pseudo-random code, and the alternate wheel method is used to solve the velocity ambiguity by using the remainder of the target velocity measured twice. calculation, so that the true speed of the target can be determined. This method ensures that the distance measurement is not ambiguous within the range of the radar, so that the detection ability of the radar for distant targets can be improved through the range-segmented target detection, and the distance-sensitivity control method can be used to reduce the distance caused by nearby ground and sea clutter. The false alarms caused by the radar improve the detection ability of the radar for slow targets in complex environments.

为解决以上提出的问题，本发明提出了一种伪随机码调相连续波雷达速度模糊解算方法，包括以下步骤：In order to solve the above problems, the present invention proposes a pseudo-random code phase modulation continuous wave radar velocity ambiguity solution method, comprising the following steps:

（1）雷达采用a、b两组时钟频率不同的伪随机码在波束驻留时间内完成一次交替轮发；(1) The radar uses two groups of pseudo-random codes with different clock frequencies a and b to complete an alternate rotation within the beam dwell time;

（2）雷达分别接收目标反射回来的电磁波信号，并从中提取出目标参数，目标参数包括：距离、方位、速度余数和测量时刻；(2) The radar receives the electromagnetic wave signal reflected by the target separately, and extracts the target parameters from it. The target parameters include: distance, azimuth, speed remainder and measurement time;

（3）同一目标的判断：若目标的距离、方位和测量时刻满足数据关联条件，则为同一目标；(3) Judgment of the same target: if the distance, azimuth and measurement time of the target meet the data association conditions, it is the same target;

步骤（3）具体包括以下三个步骤：Step (3) specifically includes the following three steps:

301、时间相关判断：若满足时间相关条件，继续进行下一步骤的相关判断；301. Time-related judgment: if the time-related condition is satisfied, proceed to the next step of related judgment;

时间相关条件为：T₁-T₂≤Δt；The time-related condition is: T₁ -T₂ ≤Δt;

其中：Δt为目标测量周期；Where: Δt is the target measurement cycle;

T₁为a组伪随机码测量周期内的目标测量时刻；T₁ is the target measurement moment in the measurement period of group a pseudo-random code;

T₂为b组伪随机码测量周期内的目标测量时刻；T₂ is the target measurement moment in the measurement period of group b pseudo-random codes;

302、方位相关判断：若满足方位相关条件，继续进行下一步骤的相关判断；302. Orientation-related judgment: if the orientation-related conditions are met, proceed to the next step of related judgment;

先计算出方位门限：First calculate the azimuth threshold:

方位门限： $G_{A} = \frac{Δt v_{\max}}{r_{pk}} + k_{A} + σ_{A};$ Azimuth Threshold: $G_{A} = \frac{Δt v_{\max}}{r_{pk}} + k_{A} + σ_{A};$

其中v_max为目标运动最大速度，Δt为目标测量周期，σ_A为方位角度误差，k_A分别为方位门限系数；Where v_max is the maximum speed of target movement, Δt is the target measurement period, σ_A is the azimuth angle error, and k_A are the azimuth threshold coefficients;

方位相关条件为：|A₁-A₂|≤G_AAzimuth-related conditions are: |A₁ -A₂ |≤G_A

式中：A₁为a组伪随机码测量周期内的目标方位值；In the formula: A₁ is the target orientation value in the measurement period of group a pseudo-random code;

A₂为b组伪随机码测量周期内的目标方位值；A₂ is the target azimuth value in the measurement period of group b pseudo-random code;

303、距离相关判断：若满足距离相关条件，则认为是同一目标；303. Distance-related judgment: if the distance-related conditions are met, they are considered to be the same target;

距离相关条件：Conditions related to distance:

|R₁-R₂|≤Δtv_max+k_Rσ_R|R₁ -R₂ |≤Δtv_max +k_R σ_R

式中：v_max为目标运动最大速度，Δt为目标测量周期，k_R为距离门限系数，σ_R为距离误差，R₁为a组伪随机码测量周期内的目标距离值，R₂为b组伪随机码测量周期内的目标距离值。In the formula: v_max is the maximum speed of the target movement, Δt is the target measurement period, k_R is the distance threshold coefficient, σ_R is the distance error, R₁ is the target distance value in the measurement period of group a pseudo-random code, R₂ is b The target distance value within the group pseudo-random code measurement period.

（4）对同一目标的目标参数，分别取a，b两组伪随机码的速度余数和整数倍模糊速度模值相加，获得a，b两组伪随机码各自对应的目标可能速度值：(4) For the target parameters of the same target, the velocity remainders of the two groups of pseudo-random codes of a and b are added together with the integral multiple fuzzy velocity modulus, and the possible velocity values of the targets corresponding to the two groups of pseudo-random codes of a and b are obtained:

${\overset{^^}{V V}}_{ai ai} = = i i \times \times {V V}_{mod mod a a} + + {V V}_{11};;$

${\overset{^^}{V V}}_{bj bj} = = j j \times \times {V V}_{mod mod b b} + + {V V}_{22};;$

式中：i、j=0,1,……,N，i、j、N均为自然数；In the formula: i, j=0,1,...,N, i, j, N are all natural numbers;

V₁为发射a组伪随机码时测量到的速度余数；V₁ is the velocity remainder measured when transmitting a group of pseudo-random codes;

V₂为发射b组伪随机码时测量到的速度余数；V₂ is the velocity remainder measured when transmitting group b pseudo-random codes;

V_moda为a组伪随机码覆盖的模糊速度模值；V_moda is the fuzzy velocity modulus covered by a group of pseudo-random codes;

V_modb为b组伪随机码覆盖的模糊速度模值；V_modb is the fuzzy velocity modulus covered by group b pseudo-random codes;

为利用a组伪随机码计算到的目标可能速度值； is the target possible speed value calculated by using a group of pseudo-random codes;

为利用b组伪随机码计算到的目标可能速度值；

is the target possible speed value calculated by using group b pseudo-random codes;

（5）对a组伪随机码对应的目标可能速度值和b组伪随机码对应的目标可能速度值

取差值：(5) The possible speed value of the target corresponding to the pseudo-random code of group a The target possible speed value corresponding to group b pseudo-random code

Take the difference:

$Δ Δ {d d}_{ij ij} = = | | {\overset{^^}{V V}}_{ai ai} - - {\overset{^^}{V V}}_{bj bj} | |;; i i,, j j = = 0,1 0,1,, . . . . . . . . . . . .,, N N;;$

当差值Δd_ij≤3σ_v，其中σ_v为速度测量误差，即满足速度误差压缩关系，则对应的i、j为目标速度对应的真实速度模糊模值，记为m、n，目标速度就可以表示为：When the difference Δd_ij ≤3σ_v , where σ_v is the speed measurement error, that is, the speed error compression relationship is satisfied, then the corresponding i and j are the real speed fuzzy modulus corresponding to the target speed, denoted as m and n, and the target speed is It can be expressed as:

V＝m×V_moda+V₁或V＝n×V_modb+V₂；V=m×V_moda +V₁ or V=n×V_modb +V₂ ;

式中：V为目标速度；In the formula: V is the target speed;

m为a组伪随机码对应的目标真实速度模糊数值；m is the fuzzy value of the target's real speed corresponding to the pseudo-random code of group a;

n为b组伪随机码对应的目标真实速度模糊数值；n is the fuzzy value of the target real speed corresponding to group b pseudo-random code;

完成目标速度解算。Complete target speed solution.

本发明与背景技术相比，具有以下优点：Compared with the background technology, the present invention has the following advantages:

1.采用距离分段目标检测方法，近距离杂波不会干扰远距离目标的检测，远距离目标检测能力增强；1. Adopting the detection method of distance segmented targets, the short-distance clutter will not interfere with the detection of long-distance targets, and the detection ability of long-distance targets is enhanced;

2.可通过距离-灵敏度控制方法降低因近处地、海杂波引起的虚警，提高雷达在复杂环境中对慢速目标的检测能力。2. The false alarm caused by nearby ground and sea clutter can be reduced through the distance-sensitivity control method, and the radar's ability to detect slow targets in complex environments can be improved.

具体实施方式Detailed ways

一种伪随机码调相连续波雷达速度模糊解算方法，通过合理选择调制伪码的重复频率，使得在雷达量程范围内距离不模糊，而速度是模糊的，具体包括以下步骤：A pseudo-random code phase modulation continuous wave radar speed ambiguity resolution method, by reasonably selecting the repetition frequency of the modulation pseudo code, so that the distance is not ambiguous within the range of the radar, but the velocity is ambiguous, specifically comprising the following steps:

实施例中，雷达量程为25km，雷达波长为0.03m，伪随机码a时钟频率选为2.5MHz，伪随机码b时钟频率选为3MHz，伪随机码码长选为511位，对应的无模糊距离是：25.5km；伪随机码a对应的无模糊速度为73.39m/s，伪随机码b对应的无模糊速度为88.06m/s；伪随机码a、b交替轮发，轮发时间间隔为20ms；In the embodiment, the radar range is 25km, the radar wavelength is 0.03m, the pseudo-random code a clock frequency is selected as 2.5MHz, the pseudo-random code b clock frequency is selected as 3MHz, the pseudo-random code length is selected as 511 bits, and the corresponding unambiguous The distance is: 25.5km; the unambiguous speed corresponding to the pseudo-random code a is 73.39m/s, and the unambiguous speed corresponding to the pseudo-random code b is 88.06m/s; the pseudo-random code a and b are sent alternately, and the time interval 20ms;

（2）雷达分别接收目标反射回来的电磁波信号，并从中提取出目标参数，目标参数包括：距离、方位、速度余数和测量时间；(2) The radar receives the electromagnetic wave signal reflected by the target separately, and extracts the target parameters from it. The target parameters include: distance, azimuth, speed remainder and measurement time;

其中：Δt为目标测量周期；Where: Δt is the target measurement cycle;

302、方位相关判断：若满足方位相关条件，继续进行下一步骤的相关判断；302. Orientation-related judgment: if the orientation-related conditions are satisfied, proceed to the next step of related judgment;

先计算出方位门限：First calculate the azimuth threshold:

303、距离相关判断：若满足距离相关条件，则认为是同一目标；303. Distance-related judgment: if the distance-related conditions are satisfied, they are considered to be the same target;

距离相关条件：Conditions related to distance:

|R₁-R₂|≤Δtv_max+k_Rσ_R|R₁ -R₂ |≤Δtv_max +k_R σ_R

实施例中，a码发射时间段的回波目标参数为R₁=9350m，A₁=35.6°，V₁=60m/s，T₁=10.06s；b码发射时间段的回波目标参数为R₂=9330m，A₂=35.6°，V₂=3m/s，T₂=10.08s；通过计算得到所测量到的距离、方位、时间参数满足数据关联关系，可以认为是同一个目标；In the embodiment, the echo target parameter in the code a transmission period is R₁ =9350m, A₁ =35.6°, V₁ =60m/s, T₁ =10.06s; the echo target parameter in the code b transmission period is R₂ =9330m, A₂ =35.6°, V₂ =3m/s, T₂ =10.08s; through calculation, the measured distance, azimuth, and time parameters satisfy the data association relationship, which can be considered as the same target;

为利用a组伪随机码计算到的目标可能速度值；

is the target possible speed value calculated by using a group of pseudo-random codes;

为利用b组伪随机码计算到的目标可能速度值；

实施例中，计算

In the example, the calculation

${\overset{^^}{V V}}_{a a 00} = = 00 \times \times {V V}_{mod mod a a} + + {V V}_{11} = = 00 \times \times 73.39 73.39 + + 6060 = = 6060 m m / / s the s$

${\overset{^^}{V V}}_{a a 11} = = 11 \times \times {V V}_{mod mod a a} + + {V V}_{11} = = 11 \times \times 73.39 73.39 + + 6060 = = 133.39 133.39 m m / / s the s$

${\overset{^^}{V V}}_{a a 22} = = 22 \times \times {V V}_{mod mod a a} + + {V V}_{11} = = 22 \times \times 73.39 73.39 + + 6060 = = 206.78 206.78 m m / / s the s$

${\overset{^^}{V V}}_{a a 33} = = 33 \times \times {V V}_{mod mod a a} + + {V V}_{11} = = 33 \times \times 73.39 73.39 + + 6060 = = 280.17 280.17 m m / / s the s$

${\overset{^^}{V V}}_{a a 44} = = 44 \times \times {V V}_{mod mod a a} + + {V V}_{11} = = 44 \times \times 73.39 73.39 + + 6060 = = 353.56 353.56 m m / / s the s$

${\overset{^^}{V V}}_{a a 55} = = 55 \times \times {V V}_{mod mod a a} + + {V V}_{11} = = 55 \times \times 73.39 73.39 + + 6060 = = 426.95 426.95 m m / / s the s$

${\overset{^^}{V V}}_{a a 66} = = 66 \times \times {V V}_{mod mod a a} + + {V V}_{11} = = 66 \times \times 73.39 73.39 + + 6060 = = 500.34 500.34 m m / / s the s$

计算

calculate

${\overset{^^}{V V}}_{b b 00} = = 00 \times \times {V V}_{mod mod b b} + + {V V}_{22} = = 00 \times \times 88.06 88.06 + + 33 = = 33 m m / / s the s$

${\overset{^^}{V V}}_{b b 11} = = 11 \times \times {V V}_{mod mod b b} + + {V V}_{22} = = 11 \times \times 88.06 88.06 + + 33 = = 91.06 91.06 m m / / s the s$

${\overset{^^}{V V}}_{b b 22} = = 22 \times \times {V V}_{mod mod b b} + + {V V}_{22} = = 22 \times \times 88.06 88.06 + + 33 = = 179.12 179.12 m m / / s the s$

${\overset{^^}{V V}}_{b b 33} = = 33 \times \times {V V}_{mod mod b b} + + {V V}_{22} = = 33 \times \times 88.06 88.06 + + 33 = = 267.18 267.18 m m / / s the s$

${\overset{^^}{V V}}_{b b 44} = = 44 \times \times {V V}_{mod mod b b} + + {V V}_{22} = = 44 \times \times 88.06 88.06 + + 33 = = 355.24 355.24 m m / / s the s$

${\overset{^^}{V V}}_{b b 55} = = 55 \times \times {V V}_{mod mod b b} + + {V V}_{22} = = 55 \times \times 88.06 88.06 + + 33 = = 443.3 443.3 m m / / s the s$

${\overset{^^}{V V}}_{b b 66} = = 66 \times \times {V V}_{mod mod b b} + + {V V}_{22} = = 66 \times \times 88.06 88.06 + + 33 = = 531.36 531.36 m m / / s the s$

（5）对a组伪随机码对应的目标可能速度值

和b组伪随机码对应的目标可能速度值

取差值：(5) The possible speed value of the target corresponding to the pseudo-random code of group a

The target possible speed value corresponding to group b pseudo-random code

Take the difference:

式中：V为目标速度；In the formula: V is the target speed;

m为a组伪随机码对应的目标真实速度模糊数值；m is the fuzzy value of the target real speed corresponding to the pseudo-random code of group a;

完成目标速度解算。Complete target speed solution.

实施例中，计算Δd_ij，表示为矩阵形式如下：In the embodiment, the calculation of Δd_ij is expressed as a matrix as follows:

$Δd Δd = = |\begin{matrix} 5757 & - - 31.06 31.06 & - - 119.12 119.12 & - - 207.18 207.18 & - - 295.24 295.24 & - - 383.3 383.3 & - - 471.36 471.36 \\ 130.39 130.39 & 42.33 42.33 & - - 45.73 45.73 & - - 133.79 133.79 & - - 221.85 221.85 & - - 309.91 309.91 & - - 397.97 397.97 \\ 203.78 203.78 & 115.72 115.72 & 27.66 27.66 & - - 60.4 60.4 & - - 148.46 148.46 & - - 236.52 236.52 & - - 324.58 324.58 \\ 277.17 277.17 & 189.11 189.11 & 101.05 101.05 & 12.99 12.99 & - - 75.07 75.07 & - - 163.13 163.13 & - - 251.19 251.19 \\ 350.56 350.56 & 262.5 262.5 & 174.44 174.44 & 86.38 86.38 & - - 1.68 1.68 & - - 89.74 89.74 & - - 177.8 177.8 \\ 423.95 423.95 & 335.89 335.89 & 247.83 247.83 & 159.77 159.77 & 71.71 71.71 & - - 16.35 16.35 & - - 104.41 104.41 \\ 497.34 497.34 & 409.28 409.28 & 321.22 321.22 & 233.16 233.16 & 145.1 145.1 & 57.04 57.04 & - - 31.02 31.02 \end{matrix}|$

设雷达测量误差σ_v=2m/s，则满足条件Δd_ij≤3σ_v的只有：Assuming that the radar measurement error σ_v =2m/s, the only ones that satisfy the condition Δd_ij ≤3σ_v are:

Δd_ij＝-1.68（i=4，j=4）Δd_ij = -1.68 (i=4, j=4)

所以有：m=4，n=4。So there are: m=4, n=4.

目标速度可计算如下：The target velocity can be calculated as follows:

$\begin{matrix} V V = = \frac{11}{22} [[((m m \times \times {V V}_{mod mod a a} + + {V V}_{11})) + + ((n no \times \times {V V}_{mod mod b b} + + {V V}_{22}))]] \\ = = \frac{11}{22} [[((44 \times \times 73.39 73.39 + + 6060)) + + ((44 \times \times 88.06 88.06 + + 33))]] = = 354.4 354.4 m m / / s the s \end{matrix}$

完成目标速度解算。Complete target speed solution.

Claims

1. the fuzzy calculation method of pseudo-random code phase modulating continuous wave radar speed, comprises the following steps:

(1) radar adopts a, pseudo-random code that two groups of clock frequencies of b are different in wave beam residence time, to complete an alternate wheel to send out;

(2) the radar electromagnetic wave signal that receiving target reflects respectively, and therefrom extract target component, target component comprises: distance, orientation, speed remainder and measurement are constantly;

(3) judgement of same target: if the distance of target, orientation and measurement meet data correlation condition constantly, be same target;

(4) target component to same target, gets respectively a, and the speed remainder of two groups of pseudo-random codes of b and the fuzzy speed mould of integral multiple value are added, and obtains a, each self-corresponding target possible speed value of two groups of pseudo-random codes of b:

{\hat{V}}_{ai} = i \times V_{\mod a} + V_{1};

{\hat{V}}_{bj} = j \times V_{\mod b} + V_{2};

In formula: i, j=0,1 ..., N, i, j, N are natural number;

V₁the speed remainder measuring during for transmitting a group pseudo-random code;

V₂the speed remainder measuring during for transmitting b group pseudo-random code;

V_modafuzzy speed mould value for the covering of a group pseudo-random code;

V_modbfuzzy speed mould value for the covering of b group pseudo-random code;

for the target possible speed value of utilizing a group pseudo-random code to calculate;

for the target possible speed value of utilizing b group pseudo-random code to calculate;

(5) to target possible speed value corresponding to a group pseudo-random code

with target possible speed value corresponding to b group pseudo-random code

get difference:

Δ d_{ij} = | {\hat{V}}_{ai} - {\hat{V}}_{bj} |; i, j = 0,1, . . . . . ., N;

As difference DELTA d_ij≤ 3 σ_v, σ wherein_vfor data noise, meet velocity error compression context, corresponding i, j is the fuzzy mould value of true velocity corresponding to target velocity, is designated as m, n, target velocity just can be expressed as:

V=m * V_moda+ V₁or V=n * V_modb+ V₂;

In formula: V is target velocity;

M is target true velocity Fuzzy Number Valued corresponding to a group pseudo-random code;

N is target true velocity Fuzzy Number Valued corresponding to b group pseudo-random code;

Completing target velocity resolves.

2. the fuzzy calculation method of a kind of pseudo-random code phase modulating continuous wave radar speed according to claim 1, is characterized in that: step (3) specifically comprises following three steps:

301, time correlation judgement: if meet time correlation condition, proceed the correlated judgment of next step;

Time correlation condition is: T₁-T₂≤ Δ t;

Wherein: Δ t is the target measurement cycle;

T₁for the target measurement moment of a group pseudo-random code in measuring period;

T₂for the target measurement moment of b group pseudo-random code in measuring period;

302, orientation correlated judgment: if meet orientation correlated condition, proceed the correlated judgment of next step;

First calculate orientation thresholding:

Orientation thresholding:

G_{A} = \frac{Δt v_{\max}}{r_{pk}} + k_{A} + σ_{A};

V wherein_maxfor target travel maximal rate, Δ t is the target measurement cycle, σ_afor orientation angles error, k_abe respectively orientation thresholding coefficient;

Orientation correlated condition is: | A₁-A₂|≤G_a

In formula: A₁for the target side place value of a group pseudo-random code in measuring period;

A₂for the target side place value of b group pseudo-random code in measuring period;

303, Range-based judgement: if meet Range-based condition, think same target;

Range-based condition:

|R₁-R₂|≤Δtv_max+k_Rσ_R

In formula: v_maxfor target travel maximal rate, Δ t is the target measurement cycle, k_rfor distance threshold coefficient, σ_rfor distance error, R₁for the target range value of a group pseudo-random code in measuring period, R₂for the target range value of b group pseudo-random code in measuring period.