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云计算-基于中国余数定理及全相位理论的高精度频率估计算法研究.pdf
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云计算-基于中国余数定理及全相位理论的高精度频率估计算法研究.pdf
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ABSTRACT
The frequency estimation and detection of high-frequency signal is one
critical issue in signal processing such as Radar communications, sonar,
seismic monitoring, fault diagnosis, Medical Health Care and so on.
However, limited by the Nyquist theorem, estimating the frequency of one
real-valued signal accurately requires at least two samples in one signal
cycle, indicating that the sampling rate must be equal to or larger than twice
the frequency of the measured high-frequency signal. Therefore, the
hardware cost is very high. This dissertation aims to solve the problem of
high-accuracy frequency estimation of the high-frequency signal, under the
condition of multiple undersampled signal paths (if signal frequency is f
0
, it
requires that the sampling rate f
s
<<2f
0
). To achieve this goal, the ancient
Chinese Remainder Theorem (CRT) is introduced in this dissertation.
Frequency estimation based on the reconstruction algorithm of Chinese
remainder theorem is one of the frontier focuses in the fields of signal
processing, electromagnetism and optics etc. However, the existing studies
can only realize the rough frequency estimation of complex exponential
signals. So this dissertation firstly needs to complete accurate frequency
estimation of the complex signals. Therefore the original all-phase FFT
spectrum analysis theory is introduced. Through employing apFFT/FFT
phase difference spectrum correction method to provide the exact frequency
remainders to the Chinese Remainder Theorem, this dissertation realizes
accurate frequency estimation of complex exponential signal. This algorithm
is also successfully applied to the Doppler shift estimation.
In order to further generalize undersampling frequency reconstruction
from complex exponential signals to sinusoidal signals, this dissertation
presents two remainder screening methods based on two different measures
of correcting spectrums. Then, the accurate frequency estimation of
sinusoidal signals can be realized in combination with them. The proposed
estimation scheme process is as follows: (1) Detect zero crossing point on
the high-frequency sinusoidal waveform to determine the phase information;
(2) Implement Fast Fourier Transform(or All-phase Fast Fourier Transform)
on each path’s undersampled signal, and then use Candan estimator(or
All-phase-based ratio spectrum correction) to correct the frequencies at the
peak FFT(or apFFT) spectral bins so that the frequency biases can be
extracted to realize phase correction; (3) Use the proposed classification
method based on phase features to screen the corrected remainders;
(4)Substitute the filtered frequency remainders into the closed-form robust
Chinese remainder theorem to obtain the high-accuracy frequency estimate
of the original signal. Additionally, this dissertation also deduces the
theoretic expressions of the frequency estimation variance. Numerical result
not only verifies the correctness of this theoretic expressions, but also
reflects that the proposed scheme possesses high precision and high
robustness to noise.
Key words:
Chinese Remainder Theorem, undersampled, spectrum correction,
remainder screening
I
目 录
目 录..................................................................................................................... I
第一章 绪 论....................................................................................................... 1
1.1 本课题的研究背景和意义...................................................................... 1
1.2 研究现状.................................................................................................. 2
1.3 本文研究内容.......................................................................................... 3
第二章 中国余数定理重构算法及其改进算法................................................... 5
2.1 引言.......................................................................................................... 5
2.2 经典中国余数定理重构算法.................................................................. 6
2.2.1 中国余数定理的由来................................................................... 6
2.2.2 经典中国余数定理算法............................................................... 8
2.3 传统的中国余数定理重构算法............................................................ 10
2.4 基于搜索的鲁棒性 CRT 重构算法 ...................................................... 12
2.5 闭合解析形式的 CRT 重构算法 .......................................................... 14
2.6 本章小结................................................................................................ 17
第三章 结合全相位谱分析法的多普勒偏移估计............................................. 19
3.1 引言........................................................................................................ 19
3.2 全相位谱分析原理................................................................................ 20
3.2.1 离散傅里叶变换(DFT)在测定相位和幅度中的缺陷 .......... 20
3.2.2 由 DFT 到 apDFT 的推导 .......................................................... 22
3.2.3 apDFT 的性能 ............................................................................. 23
3.2.4 apDFT 的简化过程 ..................................................................... 26
3.3 相位差频率校正法................................................................................ 28
3.4 多普勒偏移估计方案............................................................................ 29
3.4.1 多普勒偏移估计的理论原理..................................................... 29
3.4.2 多普勒偏移估计具体实施方案................................................. 31
3.5 本章小结................................................................................................ 37
第四章 结合全相位谱分析法的高频余弦信号的频率估计............................. 39
4.1 引言........................................................................................................ 39
4.2 余弦信号的 CRT 模型 .......................................................................... 40
II
4.3 结合全相位谱分析法的频率估计方案................................................ 42
4.3.1 频率估计总流程......................................................................... 42
4.3.2 各处理步骤的详细过程............................................................. 43
4.4 本章小结................................................................................................ 47
第五章 结合 FFT 谱分析法的高频余弦信号的频率估计 ................................ 48
5.1 引言........................................................................................................ 48
5.2 结合 FFT 谱分析法的频率估计方案 ................................................... 48
5.2.1 频率估计总流程......................................................................... 48
5.2.2 频率估计子过程分析................................................................. 50
5.3 本章小结................................................................................................ 53
第六章 实验结果及分析..................................................................................... 55
6.1 结合全相位谱分析法的多普勒偏移估计方案.................................... 55
6.1.1 性能指标..................................................................................... 55
6.1.2 实验结果及其分析..................................................................... 55
6.2 结合全相位谱分析法的高频余弦信号的频率估计方案.................... 58
6.2.1 性能指标..................................................................................... 58
6.2.2 实验结果及其分析..................................................................... 58
6.3 结合 FFT 谱分析法的高频余弦信号的频率估计方案 ....................... 62
6.3.1 性能指标..................................................................................... 62
6.3.2 实验结果及其分析..................................................................... 62
6.4 本章小结................................................................................................ 67
第七章 总结与展望............................................................................................. 68
7.1 全文总结................................................................................................ 68
7.2 展望未来................................................................................................ 69
参考文献............................................................................................................... 71
发表论文和参加科研情况说明........................................................................... 76
致 谢................................................................................................................. 78
第一章 绪 论
1
第一章 绪 论
1.1 本课题的研究背景和意义
高频信号频率的精确估计与检测是信号处理
[1-5]
、雷达系统
[6-17]
、导航测距
[18-21]
、地震监测
[22-24]
、故障诊断
[25, 26]
、医学医疗
[27, 28]
、密码学
[29]
及图像处理
[30, 31]
等领域中至关重要的问题,引起国内以及国外相关学者的普遍关注。对于高频信
号,如果要精确地估计或者测量信号的频率,这就要求采样率必须达到很高的频
率。因为奈奎斯特定理
[32]
要求一个信号周期内采到 2 个以上样点,这样必然要
求采样速率大于等于两倍的待测高频信号的频率,随着信号频率升高,必然要求
其采样速率相应升高,这就会对模数转换器(Analog to Digital Converter,简记为
ADC)的转换速率、功耗以及硬件成本提出更高要求,在某些特定场合,甚至是
不可实现的。而在无线电等工程领域,却越来越频繁涉及频率值处于百兆(MHz)、
千 兆 (GHz) 、 万 兆 (10GHz) 数 量 级 的 信 号 采 样 、 分 析 与 处 理 问 题 。 如 在
IEEE802.15.3a、IEEE802.15.4a 等标准方案中,物理层信号采用了超宽带 UWB
技术,为实现室内精确定位及高速信息传输,要求其脉冲信号频率最高值达到
3.1GHz 以上
[33]
。毫无疑问,高频信号处理首先要求进行高速采样,这样在工程
上必然对模数转化设备及其后期的 FPGA 等数字处理器件的性能及成本提出高
的要求。因而,在无法满足密集均匀采样的情况下,如何实现高分辨率地识别并
分离出密集谱成分是学术界和工程界迫切需要解决的问题。仅靠改进硬件设备的
数据采集性能,其作用是非常有限的,只有在信号处理领域提出新的谱分析理论
方法,才能根本上解决这类问题。
为解决在低速欠采样条件下(假设信号频率为 f
0
,要求采样速率 f
s
<<2 f
0
)的高
频信号的频率估计问题,将我国古老的中国余数定理
[1, 29]
(Chinese Remainder
Theorem, CRT)引入该领域中。中国余数定理研究的是这样的一个问题:为重构
某一未知整数 N,给定的只有一组相互之间满足互素关系的整数模值:M
1
, M
2
, … ,
M
L
,及其未知整数 N 对各模值 M
i
的模除结果 r
i
(即余数 r
i
, 满足 r
i
=N mod M
i
),
i=1,…, L,从这些个余数 r
i
重构未知整数 N 的问题。作为一种纯粹的数学理论,
许多学者对其进行了较为系统的研究和证明,在数论等相关书籍中可以找到详细
的数学表述和证明。它是一种无权的数值表征系统,也就是用部分来代表整体的
数学思想,这种思想的广泛应用最初是在密码学中。由于其独立并行特性,使得
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