CN103874192B - Pseudo code ranging time delay estimation method - Google Patents
Pseudo code ranging time delay estimation method Download PDFInfo
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- CN103874192B CN103874192B CN201210534022.7A CN201210534022A CN103874192B CN 103874192 B CN103874192 B CN 103874192B CN 201210534022 A CN201210534022 A CN 201210534022A CN 103874192 B CN103874192 B CN 103874192B
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Abstract
The invention provides a pseudo code ranging time delay estimation method. The method comprises that: a receiving end samples the received baseband signal so that a sampling signal is obtained, and digital matching filtering is performed on the sampling signal so that a digital filtering signal is obtained; a first extreme value point of the digital filtering signal is searched and acquired; and estimation values of coefficients a, b and c of Taylor series near the position of the first extreme value point are defined, the extreme value point is selected to be the center, and least square estimation is performed on the coefficients a, b and c by 2m+1 sample value points of extreme value points of distance of two sides within a code element period of being not greater than 1/4 so that the estimation values (img file='DDA00002566275600011. TIF' wi='157' he='58 /) are obtained, and signal arrival estimation time (img file='DDA00002566275600012. TIF' wi='61' he='58 /) is obtained. Complexity of exiting methods is reduced by the method. Meanwhile, non-ideal factors in channels are considered so that the delay estimation method is wider in range of application.
Description
Technical field
The present invention relates to radio distance-measuring and field of locating technology, more particularly to a kind of time of digital pseudo-random code ranging prolongs
When method of estimation.
Background technology
Current radio distance-measuring technology mainly has Doppler ranging method, pseudo-random code ranging method, and carrier wave telemetry etc..Its
In, pseudo-random code ranging can be divided into unidirectional range finding and bidirectional ranging, and either which kind of metering system, is required for entering time of arrival (toa)
Row estimates that it is following several to be estimated that arrival time (i.e. Delay Estima-tion) method mainly has according to the signal for receiving：
Maximum Likelihood Estimation Method
Maximum Likelihood Estimation Method is the asymptotic optimization method in the known estimation technique, can be reached in the case of high s/n ratio
Cramér-Rao lower bound (Cramer-Rao Bound), it is calculated under white Gaussian noise multi-path environment.Although Maximum Likelihood Estimation Method
It is asymptotic optimization method under white Gaussian noise, but due to needing to do the optimization and a large amount of mathematical operations of polytomy variable, it is multiple
Miscellaneous degree is higher, and hardware realizes more difficulty, so practical degree is not high.
Simplified maximum-likelihood method
For digital baseband system, the base band pseudo-code signal after waveform shaping after receiving end is accepted, is passed through by channel
Pseudo-code matched filtering and forming filter are crossed, the result that obtains and the in the analog case sampling to matched filtering result are of equal value
's.
Have document carries out matched filtering after signal is sampled through A/D, then using Signal Matching filter result in maximum
Point nearby carries out secondary Taylor expansion, is then estimated using sample point, and then Maximum-likelihood estimation simplifies under awgn channel
For：
Wherein, t is one section of vector of continuous sampling time point composition, and R is the autocorrelation matrix of signal, and h is to be filtered in matching
Sample value of the ripple result in t.Although this method is simple, noise is not fully thermal noise (Gauss white noise in practice
Sound), in the system for have carrier wave also have phase noise (non-gaussian white noise) and non-linearity of power amplifier etc. non-ideal because
Element, so not necessarily asymptotic optimization in this case.
In sum, or current method complexity is high, it is difficult to realize；Excessively simplify, do not consider non-in channel
Desirable factors, narrow application range.
The content of the invention
(1) technical problem to be solved
The purpose of the present invention is to propose to a kind of time delay estimation method for being suitable for pseudo-random code ranging, meter is this method reduce
Complexity is calculated, while considering non-ideal factor in channel, makes time-delay estimation method use scope wider.
(2) technical scheme
The invention provides a kind of time delay estimation method of pseudo-random code ranging, the method includes：
S1, receiving end to the baseband signal for receiving sample and obtain sampled signal, and numeral is carried out to sampled signal
Digital matched filtering signal is obtained with filtering；
S2, the first extreme point searched for and obtain digital matched filtering signal；
S3, the secondary term coefficient a, one that are defined on first Near The Extreme Point simulation matched filtering signal the second Taylor series formula
The estimate of secondary term coefficient b and constant term c is：Centered on extreme point, two lateral extent extreme points are no more than 1/ for selection
2m+1 sample point p (n in 4 code-element periods-m),p(n-m+1)…,p(n-1),p(n0),..., (nm) to coefficient a, b, c does most
A young waiter in a wineshop or an inn multiplies estimation：Obtain estimateThen the extreme point of signal is estimated as：
Wherein, m >=1, X is the column vector of sample point composition：X=[p (n-m)p(n-m+1)…p(nm)]T, H is measurement
Matrix：
Preferably, the receiving end in the step S1 is two line structures for having in-phase component and quadrature component.
Preferably, also include carrying out two models to the digital matched filtering signal that two-way matched filtering is obtained in the step S1
Number computings, the step of remove frequency deviation and skew.
Preferably, also include carrying out Low-pass interpolation to digital matched filtering signal in the step S1, sample rate is more than 5
Divided by code-element period.
Preferably, the m values are fixed, then (HTH)-1HT=C is constant matrices, and coefficient is estimated as：Time delay
It is estimated as：Wherein TsIt is sample rate, n '0It is n0Moment true moment value.
(3) beneficial effect
The present invention by providing a kind of time delay estimation method of pseudo-random code ranging, make estimation time delay when do not need iteration
Extreme value is sought in optimization, instead only Linear Algebra Operation, the estimation computing of time delay of great abbreviation.Precision is higher,
When the increase result of the increase with sample rate and signal to noise ratio tends to optimal, it is highly suitable for real-time system and complexity is not high
System, therefore have broad application prospects.
Brief description of the drawings
The step of Fig. 1 is the method provided by the present invention flow chart；
Fig. 2 is receiver structure schematic diagram in specific embodiment；
Fig. 3 is matched filtering result schematic diagram in specific embodiment；
Fig. 4 is the performance chart being used under Gaussian channel of the invention in specific embodiment.
Specific embodiment
The present invention is described in further details with specific embodiment below in conjunction with the accompanying drawings.
The invention provides a kind of time delay estimation method of pseudo-random code ranging, as shown in figure 1, its step mainly includes：
S1, receiving end to the baseband signal for receiving sample and obtain sampled signal, and numeral is carried out to sampled signal
Digital filtered signal is obtained with filtering；
S2, the first extreme point searched for and obtain digital filtered signal；
S3, the secondary term coefficient a, one that are defined on first Near The Extreme Point simulation matched filtering signal the second Taylor series formula
The estimate of secondary term coefficient b and constant term c is：Centered on extreme point, two lateral extent extreme points are no more than 1/ for selection
2m+1 sample point p (n in 4 code-element periods-m),p(n-m+1)…,p(n-1),p(n0),...,p(nm) to coefficient a, b, c does most
A young waiter in a wineshop or an inn multiplies estimation：Obtain estimateThen the extreme point of signal is estimated as：
Wherein, m >=1, X is the column vector of sample point composition：X=[p (n-m)p(n-m+1)…p(nm)]T, H is measurement
Matrix：The distribution of noise can't be done using least square method it is assumed that simply in the measurement phase
Between noise held stationary, this causes that the range of application of this method is more extensive.
Wherein, the receiving end in step S1 is the structure for having in-phase component and quadrature component two-way.
Wherein, also include carrying out two norm fortune to the digital matched filtering signal that two-way matched filtering is obtained in step S1
Calculate, the step of remove frequency deviation and skew.
Wherein, step S1 also includes carrying out Low-pass interpolation to digital matched filtering signal, makes sample rate more than 5/ code element week
Phase.
Wherein, m values are made to fix, then (HTH)-1HT=C is constant matrices, and coefficient estimate is：Time delay is estimated
Evaluation is：Wherein TsIt is sample rate, n '0It is n0Moment true moment value.So, estimate to be only line
Property algebraic operation, greatly simplify the estimation computing of time delay.
Specific step and principle：
, to being sampled after baseband signal r (t) that receives, sample rate is more than or equal to Nyquist Nyquist for S1, receiving end
Sample rate, obtains r (n), then carries out digital matched filtering to r (n), obtains matched filtering result p (n).For there is same phase point
Amount (In-phase Component, I roads) and quadrature component (Quadrature Component, Q roads) system, it is incoherent under
Can there is frequency deviation and skew during frequency conversion, two norm computings can be carried out to I, Q two-way matched filtering result so as to remove frequency deviation and phase
Partially.Then, Low-pass interpolation is carried out to p (n), makes sample rate more than 5 divided by code-element period, so make the result of matched filtering more
It is good；If sample rate alreadys exceed 5 divided by code-element period, row interpolation can be entered；
S2, first extreme point is searched for signal p (n) after interpolation, it is located at time point n0, due to the spy of pseudo-code signal
Property, first extreme point roughly indicates Shou Dajing positions in time；
The maximum of corresponding analog signals p (t) of p (n) may not be adopted due to sampled point, so needing to utilize p
Estimate position of the value of (n) to p (t) maximum points in time；
S3, be defined on first extreme point position nearby secondary term coefficient a, the Monomial coefficient b of the second Taylor series formulas and
The estimate of constant term c is：Centered on extreme point, two lateral extent extreme points are no more than in 1/4 code-element period for selection
2m+1 sample point p (n-m),p(n-m+1)…,p(n-1),p(n0),...,p(nm) to coefficient a, b, c does least-squares estimation：Then the extreme value point estimate of signal is：
Wherein, m >=1, X is the column vector of sample point composition of the matched filtering result near extreme value：X=[p (n-m)p
(n-m+1)…p(nm)]T, H is matrix：
The principle of step S3 is：Because the pseudo-code signal after Waveform shaping is by matched filtering, can be presented in its extreme point
Convexity, then, even if the nonlinear device such as power amplifier can cause distortion to signal, but convexity will not change, so can
Taylor expansion is done in Near The Extreme Point, for simulation matched filtering signal p (t), in its extreme point t0Neighbouring Taylor expansion expression
Formula is：
P (t)=a (t-t0)2+b(t-t0)+c+o(t2)+n(t)
Wherein, a, b, c are respectively Taylor expansion coefficient, and n (t) is noise, o (t2) it is the second order dimensionless of t, can neglect
Omit.So just utilize least square method to coefficient a using Near The Extreme Point, b, c estimates, obtains estimateSo as to
The coefficient of the quadratic function for obtaining, then the time location where its symmetry axis can be used as time location where p (t) extreme points
It is accurate to estimate, so just obtain propagation delay.The distribution of noise can't be done due to least square method it is assumed that simply in measurement
Period noise held stationary.This causes this method range of application more extensive.
Although expression formula：It is more complicated in form, it is in fact possible to make n-m=-m, n-m+1=-m+
1,…,n0=0, nm=m..When m is fixed, the system being commonly designed this condition is typically all satisfaction, (HTH)-1HT=C
It is constant matrices, can precalculates out, so just it is believed that p (t) is wanted on a timeline to be translation n0, when then again
Stretch 1/T on countershafts, the maximum point t for estimating can calculate with following expression：
ThenWherein TsIt is sample rate, n '0It is n0Moment true moment value.
Here, using receiver as shown in Figure 2：
From antenna receive signal by after bandpass filtering, by I, Q two-way down coversion, low-pass filtered and A-D converter
ADC is sampled, and ADC sample rates are 1GHz, then by matched filter：Including forming filter and pseudo-code matched filter,
Formed filter uses square root raised cosine filter in this example, then obtains I, Q two-way output signal.
Output signal carries out carrier auxiliary or directly does two norm computings elimination carrier wave influence, then carries out Low-pass interpolation and arrives
More than 5 times character rates, finally give matched filtering result：As shown in figure 3, wherein abscissa is the time value of matched filtering,
Ordinate is matched filtering result value, wherein the signal to noise ratio for using is 0dB, pseudo- code length is 127.
Choosing three maximum sampling points [111.4590,127.3509,111.8500] carries out least-squares estimation, wherein H
Matrix can be used：
That is n-1=-1, n0=0, n1=1, n0Real correspondence moment n '0=2.7300 × 10-07S so now, constant square
Battle array：
Obtain：
So just it is estimated that less than the time delay of chip period, increasing the precision of time delay.
It can be seen that only needing to do simple multiply-add operation under this numerical procedure, multiplication, addition complexity are with estimation point
Several increases is O (n2)。
Fig. 4 is directed to the performance curve of use the inventive method of Fig. 1 receivers, the simulation result under awgn channel.
For other situations, it is also possible to obtain similar results.It can be seen that, can be reached in the case of medium SNR and estimated well
Meter precision.For general range finding application, mean square error is less than 10-10S, respective distances error the 3cm (light velocity × 10-10s)
Can be very good to meet demand.
The above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
For member, on the premise of the technology of the present invention principle is not departed from, some improvement and replacement can also be made, these improve and replace
Also should be regarded as protection scope of the present invention.
Claims (4)
1. a kind of time delay estimation method of pseudo-random code ranging, it is characterised in that the method includes：
S1, receiving end to the baseband signal for receiving sample and obtain sampled signal, and numeral matching filter is carried out to sampled signal
Ripple obtains digital matched filtering signal；
S2, the first extreme point searched for and obtain digital matched filtering signal；
S3, the secondary term coefficient a, the first order that are defined on first Near The Extreme Point simulation matched filtering signal the second Taylor series formula
The estimate of coefficient b and constant term c is：Centered on extreme point, two lateral extent extreme points are no more than 1/4 yard for selection
2m+1 sample point p (n in first cycle-m),p(n-m+1)…,P(n-1),p(n0),...,p(nm) to coefficient a, b, c does minimum
Two multiply estimation：Obtain estimateThen the extreme point of signal is estimated as：
Wherein, m >=1, X is the column vector of sample point composition：X=[p (n-m)p(n-m+1)…p(nm)]T, H is measurement matrix：
Wherein, the m values are fixed, then (HTH)-1HT=C is constant matrices, and coefficient is estimated as：Delay Estima-tion
For：Wherein TsIt is sample rate, n '0It is n0Moment true moment value.
2. method as claimed in claim 1, it is characterised in that receiving end in the step S1 is to have in-phase component and quadrature component
Two line structures.
3. method as claimed in claim 2, it is characterised in that also include in the step S1：Two-way matched filtering is obtained
Digital matched filtering signal carries out two norm computings, removes frequency deviation and skew.
4. the either method as described in claim 1-3, it is characterised in that also include in the step S1：To digital matched filtering
Signal carries out Low-pass interpolation, makes sample rate more than 5 divided by code-element period.
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| US7403559B1 (en) * | 2003-01-03 | 2008-07-22 | Benjamin Fisher | Binary-valued signal modulation compression for high speed cross-correlation |
| CN102256352A (en) * | 2011-07-06 | 2011-11-23 | 清华大学 | Positioning method based on physical layer pipeline technology |
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| US7403559B1 (en) * | 2003-01-03 | 2008-07-22 | Benjamin Fisher | Binary-valued signal modulation compression for high speed cross-correlation |
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