相位噪声测量中的关键算法及实现

发布时间：2018-09-06 13:55

【摘要】：相位噪声是衡量频率源优劣的一项重要技术指标,对其进行准确测量在航空航天、微波链路及通信领域有着重要意义,相位噪声测量技术已成为电子测量领域的重要研究内容。随着对测量实时性和灵活性的要求不断提高,数字化的相位噪声测量系统具有良好的应用前景。本课题的研究是在鉴相法相位噪声测量系统的硬件基础上开展,该系统包括前端鉴相电路、数字处理模块以及主机部分,其中数字处理模块使用了DSP和FPGA硬件平台。本课题主要工作是研究相位噪声测量中的关键技术和算法,并在数字处理模块上实现,通过这些技术和算法改善测量系统的性能。本课题主要研究工作包括以下几个部分：1.对环路滤波器设计技术进行了研究。在鉴相法相位噪声测量系统中,锁相环是整个测量系统中的关键技术之一,而环路滤波器是锁相环的重要一环,对鉴相后的信号起到了抑制噪声及高频分量的作用。本文选用级联梳状(CIC)滤波器与FIR滤波器级联的形式,完成了高抽取率的窄带环路滤波器的程序设计,并在FPGA平台上实现,该设计能满足相位噪声测量系统的指标要求。2.对互相关算法进行了研究。本文将互相关算法应用在相位噪声测量系统中,研究该算法对噪声底部的影响,并完成了互相关算法的程序设计,将该程序应用在系统的DSP中,本课题研究的相位噪声测量系统具有两路信号采样结构,可以在同一个采样时钟控制下进行两路同步采样,采样获得的两路数据送入DSP进行互相关算法的处理。实验结果表明,在运算次数达到一定程度时,互相关算法对测量电路带来的非相关性噪声有抑制作用,使用该算法获得的功率谱密度曲线具有更低的噪声底部。3.对功率谱估计算法进行了研究。本系统将鉴相后的信号送入DSP进行功率谱估计以获得相位噪声的功率谱密度曲线。本文使用周期图谱估计法作为功率谱估计方法,并设计了相应的频谱分段以及拼接的方式,使测量系统在能够满足测量精度要求的同时减少运算资源的消耗,完成了功率谱估计算法的仿真试验和程序设计,并在DSP上实现。4.对低频缺损补偿算法进行了研究。使用鉴相法获得的相位噪声功率谱密度曲线会出现低频处被削减一部分的现象,这种现象被称为低频缺损。本文研究了低频缺损现象产生的原因及补偿方法,设计了低频缺损补偿程序,通过建立测量电路模型进行仿真,验证了程序的可行性。
[Abstract]:Phase noise is an important technical index to measure the quality of frequency source. Accurate measurement of phase noise is of great significance in the fields of aerospace, microwave link and communication. Phase noise measurement technology has become an important research content in the field of electronic measurement. With the increasing demand for real-time and flexibility of measurement, the digital phase noise measurement system has a good application prospect. The research is carried out on the basis of the hardware of the phase noise measurement system, which includes the front-end phase detection circuit, the digital processing module and the host part, in which the digital processing module uses DSP and FPGA hardware platform. The main work of this paper is to study the key techniques and algorithms of phase noise measurement and implement them on the digital processing module to improve the performance of the measurement system. The main research work includes the following parts: 1. The design technology of loop filter is studied. Phase locked loop (PLL) is one of the key techniques in the whole measurement system, and the loop filter is an important link of PLL, which plays an important role in suppressing the noise and high frequency components of the phase discrimination signal. In this paper, the concatenated comb (CIC) filter and FIR filter are selected to complete the program design of narrow band loop filter with high decimation rate, and it is implemented on FPGA platform. The design can meet the requirement of phase noise measurement system. The cross correlation algorithm is studied. In this paper, the cross-correlation algorithm is applied to the phase noise measurement system. The effect of the algorithm on the bottom of the noise is studied, and the program of the cross-correlation algorithm is designed. The program is applied to the DSP of the system. The phase noise measurement system studied in this paper has a two-channel signal sampling structure, which can be controlled by the same sampling clock to carry out two synchronous sampling. The two channels of data obtained from the sampling are sent into DSP to process the cross-correlation algorithm. The experimental results show that the cross-correlation algorithm can suppress the non-correlated noise brought by the measuring circuit when the number of operations reaches a certain degree, and the power spectral density curve obtained by the algorithm has a lower noise base. 3. The power spectrum estimation algorithm is studied. In this system, the phase discrimination signal is sent to DSP for power spectrum estimation to obtain the power spectral density curve of phase noise. In this paper, the periodic spectrum estimation method is used as the power spectrum estimation method, and the corresponding spectrum segmentation and splicing method are designed, so that the measurement system can meet the requirements of measurement accuracy and reduce the consumption of computing resources. The simulation experiment and program design of the power spectrum estimation algorithm are completed, and the implementation of. 4. 4 on DSP. The low frequency defect compensation algorithm is studied. The phase noise power spectral density curve obtained by phase discrimination method can be reduced at low frequency, which is called low frequency defect. In this paper, the cause of the phenomenon of low frequency defect and the compensation method are studied, and the program of low frequency defect compensation is designed. The feasibility of the program is verified by the simulation of the measuring circuit model.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN911.4

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