Base band time difference estimating method under off-site local oscillator conformity error

A technology of time difference estimation and error estimation, which is applied in the field of time difference high-precision measurement, can solve problems such as oscillator consistency error, influence time difference estimation results, and fail to meet engineering needs, and achieve the effect of improving performance

Active Publication Date: 2013-08-21
成都电科慧安科技有限公司
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AI Technical Summary

Problems solved by technology

[0004] The most commonly used and effective time difference estimation method is the generalized cross-correlation method, but in the face of practical engineering problems, the accuracy of time difference measurement directly using the classical time delay estimation method will be limited by the time interval between baseband data sample points, due to the baseband sampling rate low, the precision of the time difference estimation results of integral multiple sample point intervals given by the traditional correlation method obviously cannot meet the actual engineering needs; at the same time, in the process of down-converting the RF signal to the baseband, it is necessary to achieve a strict carrier in the receiver. Synchronization or high consistency of local carrier frequency and phase between receivers is very difficult, and the local oscillator (LO) in the two remote receivers will have consistency errors, which will cause the baseband signals of the two receivers to The change of the extension relationship will affect the final time difference estimation result

Method used

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  • Base band time difference estimating method under off-site local oscillator conformity error
  • Base band time difference estimating method under off-site local oscillator conformity error
  • Base band time difference estimating method under off-site local oscillator conformity error

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Embodiment 1

[0038] 1. In the radiation source location, baseband time difference estimation is analyzed, and the influence of frequency and phase consistency errors between local oscillators in different places on the time difference relationship is analyzed, and the radiation source signal under the existence of consistency errors in different places local oscillators is obtained. The signal time difference relationship model after frequency conversion to baseband is as follows:

[0039]

[0040] Expressed in a digital baseband system as:

[0041]

[0042] here x i [n]=x i (nT δ ),i=1,2,T δ is the time interval between adjacent sample points in the baseband;

[0043] 2. According to the baseband signal time difference relationship model under the existence of local oscillator consistency error, a three-dimensional search maximum likelihood time difference estimation method based on the principle of maximum relief estimation is given.

[0044] Three-dimensional search maximum l...

Embodiment 2

[0068] Since the given maximum likelihood time difference estimation method requires a three-dimensional search with high computational complexity, which is not conducive to engineering implementation, a two-dimensional search after dimensionality reduction is given to realize time difference estimation:

[0069] pair matrix Decompose to get the matrix Φ f (f 2,1 ,τ t,2,1 )as well as

[0070]

[0071]

[0072] I represents the identity matrix whose diagonal elements are all 1s. So similar to the time delay estimation of the correlation method, we can get the objective function L 2 :

[0073]

[0074]

[0075] = | y 2 H Φ f ( τ t , 2,1 , f 2,1 ) y ...

Embodiment 3

[0104] The above problem of transforming the three-dimensional search into a two-dimensional search to realize the time difference estimation greatly reduces the amount of computation. If it is necessary to compress the amount of computation to improve the estimation speed, this embodiment proposes to further reduce the dimensionality of the two-dimensional search into a one-dimensional search Methods:

[0105] Without considering the noise, it can be known from the previous derivation:

[0106]

[0107] Considering the influence of noise, the approximate expression is as follows:

[0108]

[0109] The right side of the above equation can be directly calculated by using the observation data. For the convenience of description below, it is called indirect observation data here. This equation constitutes a linear regression model, and the unknown frequency consistency error f 2,1 is the model parameter to be estimated, which can be estimated by the least square method as...

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Abstract

The invention provides a base band time difference estimating method under an off-site local oscillator conformity error. The method comprises the following steps: carrying out lower frequency conversion processing on RF signals received by a first receiver and a second receiver to obtain base band digital signals, carrying out mean value removing and normalization processing on the base band digital signals to obtain base band observation data needed by time difference measurement, introducing a frequency conformity error and a phase conformity error between the mixing local oscillators of two separated receivers to construct an objective function carrying out time difference estimation, carrying out peak value search on the objective function, and obtaining a time difference estimated value through a time difference value corresponding to the searched peak point of the objective function. The method takes the frequency conformity error and an initial phase conformity error between off-site receivers into account when the time difference is estimated, and takes the errors into a data model of the time difference measurement, the consistency requirements on the frequency and the phase of off-site local oscillators by a time difference measuring system are reduced, and the performance of time difference estimation can be improved.

Description

technical field [0001] The invention belongs to signal processing technology, in particular to high-precision measurement of time difference in a time difference positioning system. Background technique [0002] Time difference estimation technology is widely used in radar, sonar, voice enhancement, automatic camera tracking, etc., especially in radiation source location, time difference estimation technology has important application value. For the radiation source time difference positioning system, the electromagnetic signal radiated by the radiation source is intercepted by two receivers in different places, and the time difference of arrival (TDOA) between the two intercepted signals is measured by the time difference estimation algorithm. [0003] Time difference estimation technology can generally be realized in the IF or baseband of the receiver. The main disadvantage of IF time difference estimation is that the IF data flow is too large, which brings great difficult...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L7/00H04L25/03
Inventor 钟森夏威安琦
Owner 成都电科慧安科技有限公司
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