【作者】 王迪；

【导师】 张歆东；

【作者基本信息】 吉林大学 ， 电路与系统， 2023， 博士

【摘要】 随着微波技术的快速发展,与其相关的卫星通信、电子战、雷达、导航定位、无线通信等领域都实现了重大突破。在各个领域中,国内外学者针对如何实现微波信号的高性能测量这一难题也提出了众多的解决方案。然而,由于在军事战争中需要对周围环境进行实时、精准、快速的侦查与警戒,加之各种辐射源信号工作频段展宽、频率捷变灵活、有效信号微弱,这就要求接收机不仅需要具备超宽带频谱感知能力,而且在测量精度、速度、动态范围、分辨率等方面具有良好性能。这给传统的微波测量系统带来了极大压力。基于上述需求,为解决传统系统无法突破的瓶颈问题,研究者们在接收机中引入了微波光子学以适应复杂电磁频谱环境,有效提高接收机的信号识别效率,增强军事打击和防御能力。作为一个新兴的研究领域,光子辅助的微波技术展示出了明显的优势,如频率覆盖面广、传输损耗小、抗电磁干扰能力强等,于是研究人员开始将其应用在微波测量系统中以实现卓越的性能,满足应用的需求。目前的微波光子测量系统仍存在很多问题,其性能有待于进一步提高。本文围绕微波光子频率测量系统,结合微波光子移相技术、频谱叠加技术、下变频技术,针对频率测量范围、测量精度、分辨率、多参数、多频信号以及动态范围等关键问题进行研究,为微波光子频率测量系统的进一步应用提供了有力的参考方案。本文的主要研究内容如下:1.针对相位与频率信息同时提取在实际应用中的重要意义,提出了一种结合受激布里渊散射(stimulated Brillouin scattering,SBS)效应和映射技术的频率/相位双参数测量系统。该系统以SBS效应的移相技术为基础,通过调节输入信号的频率改变光载波的相位,进一步建立灵活可调的功率响应函数,使系统的测量范围与精度可灵活重构。另外,系统中存在一个相位可变的参考信号,可将接收信号的相位信息转换为功率信息,最终完成对接收信号相位与频率的提取。在18 GHz的带宽下频率测量误差小于0.15 GHz,相位测量的分辨率在0.05°以下,测量范围为0～2π。2.为了降低系统的测量误差,提出了基于布里渊相移增益比(Brillouin Phase Shift-Gain Ratio,BPGR)的高精度频率测量系统。利用未知信号频率与系统中已知信号增益和相移的关系,建立单调递增的BPGR曲线,进一步实现频率的映射,完成对未知信号频率信息的提取。应用SBS效应将整个测量范围进行信道化分割,打破了测量范围和精度之间的掣肘,进而使测量误差减小到5 MHz以下。在保证系统结构简单的前提下,该系统还具有对多频信号的测量能力,以及相对较好的稳定性。3.为了满足不同应用场景下对带宽的要求,提出了基于光频梳泵浦的带宽灵活可调的测量系统。通过光频梳泵浦激发SBS效应,构建了一个与未知信号相关并且测量范围可调的线性相移曲线,实现对未知信号频率信息的提取。更重要的是,通过简单控制光频梳的数量与位置,可以使测量频段在VHF波段、S波段、X波段和Ku波段之间灵活切换。经过实验验证,在测量带宽灵活切换的情况下,误差稳定在35 MHz以下。4.针对多频信号测量时系统频率分辨率受限的问题,引入频谱叠加技术实现具有高分辨率的测量系统。设计将SBS过程中产生的一个增益谱和两个损耗谱叠加,达到使携带未知信号信息的频谱变窄的目的,既实现了对未知信号频率的提取,也提高了系统的分辨率。此技术使响应带宽降低为原来的40%左右,将系统分辨率从30 MHz降低到14.5 MHz。另外,在保证测量误差低于8MHz的情况下,通过调整扫频信号的起始频率,使频率测量范围增加一倍。5.为了减轻后续采集与数据处理的压力,在保证系统性能的同时,引入下变频技术实现高性能的信道化频率测量系统。在这部分,以空间与时间域为基础,研究了两种信道化系统。首先,应用频移器阵列在空间域中构建信道化测量系统,实现对宽频信号的分割与变频,具有瞬时测量的优势。其次,通过引入变化的参考信号从时域上建立信道化测量系统,对于任意频率的输入信号,系统输出均可在固定的低频点采集,避免了高速器件的使用。同时,采用平滑去噪算法优化了系统的噪声特性、提高了系统的频率分辨率。提出的信道化系统在测量范围、精度、时间、动态范围以及多频测量能力等方面都具有一定的优势,为射频信号接收系统整体性能的提升提供了新的解决思路。更多还原

【Abstract】 With the rapid development of microwave technology,major breakthroughs have been made in satellite communication,electronic warfare,radar,navigation and positioning,wireless communication,and other related fields.In various fields,domestic and foreign scholars have put forward many solutions to the problem of how to achieve high performance measurement of microwave signals.However,due to the need for real-time,accurate,and rapid detection and warning of the surrounding environment in military war,coupled with the gradual broadening of the working frequency band of various radiation sources,flexible frequency and weak effective signals,the receiver is required not only to have ultra-wideband spectrum sensing capability,Moreover,it has significant advantages in measurement accuracy,speed,dynamic range,and resolution.Therefore,this puts great pressure on the traditional microwave measurement system.Based on the above requirements,in order to solve the bottleneck problem that the traditional system cannot break through,microwave photonics is introduced to adapt to the complex electromagnetic spectrum environment,effectively improve the signal recognition efficiency of the receiver,and enhance the military attack and defense capabilities.As a new research field,photonics-assisted microwave technology shows obvious advantages,such as wide frequency coverage,low transmission loss,strong anti-electromagnetic interference ability,so researchers began to apply it in microwave measurement system to achieve excellent performance,to meet the needs of applications.The current microwave photonic measurement system still has many problems,and its performance needs to be further improved.This paper focuses on the microwave photonic frequency measurement system,combines microwave photonic phase shifting technology,spectrum stacking technology,down conversion technology and other technologies,and studies the key problems of frequency measurement range,measurement accuracy,resolution,multi-parameter,multi-frequency signal and dynamic range,which provides a powerful reference scheme for the further application of the microwave photonic frequency measurement system.The main research contents of this paper are as follows:1.Aiming at the significance of simultaneous extraction of phase and frequency information in practical applications,a frequency/phase dual-parameter measurement system combined with stimulated Brillouin scattering(SBS)effect and mapping technology is proposed.Based on SBS effect phase shifting technology,the system changes the phase of the optical carrier by adjusting the frequency of the input signal,and further establishes a flexible and adjustable power response function,so that the measurement range and accuracy of the system can be flexibly reconstructed.In addition,there is a reference signal of phase change in the system,which converts the phase information of the received signal into power information,and finally completes the extraction of the phase and frequency of the received signal.At the bandwidth of 18 GHz,the error of frequency measurement is less than 0.15 GHz,the resolution of phase measurement is less than 0.05°,and the measurement range is0～2π.2.In order to reduce the measurement error of the system,a high precision frequency measurement system based on Brillouin Phase Shift-Gain Ratio(BPGR)is proposed.Based on the correlation between the unknown signal frequency and the known signal gain and phase shift in the system,the monotone increasing BPGR curve is established to further realize the frequency mapping and complete the extraction of the unknown signal frequency information.Because the SBS effect is applied to channel the whole measurement range,the constrained relationship between measurement range and accuracy is broken,and the measurement error is reduced to less than 5 MHz.Under the condition of ensuring the simple structure,the system also can measure multi-frequency signals and relatively good stability.3.In order to meet the requirements of bandwidth in different application scenarios,a flexible and adjustable bandwidth measurement system based on optical frequency comb pump is proposed.The SBS effect is excited by optical comb pump spectrum,and a linear phase shift curve is constructed which is related to unknown signal and the range is adjustable,and the unknown signal frequency information is extracted.More importantly,by simply controlling the number and position of optical frequency combs,the measurement frequency band can be flexibly switched between VHF band,S band,X band and Ku band.The experimental results show that the error is stable below 35 MHz when the measurement bandwidth is switched flexibly.4.In order to solve the problem of limited frequency resolution in multifrequency signal measurement,spectrum stacking technology is introduced to realize the high-resolution measurement system.In the design,a gain spectrum and two loss spectra generated in the SBS process are superimposed to narrow the spectrum carrying unknown signal information,which not only realizes the extraction of unknown signal frequency but also improves the system resolution.This technique reduces the response bandwidth to about 40% of the original,and reduces the system resolution from 30 MHz to 14.5 MHz.In addition,the measurement range of the frequency is doubled by adjusting the initial frequency of the sweep signal while keeping the measurement error is as low as 8 MHz.5.In order to reduce the pressure of subsequent collection and processing,down conversion technology is introduced to realize a high-performance channelized frequency measurement system while ensuring the above performance.In this part,two channelization systems based on space and time domain are proposed.Firstly,the channelized measurement system is constructed by using frequency shifter array in space domain to realize the segmentation and conversion of broadband signals,which has the advantage of instantaneous measurement.Secondly,the channelized measurement system is established in the time domain by introducing the variable reference signal.For the input signal of any frequency,the output of the system can be collected at a fixed low frequency point,avoiding the use of high-speed devices.Meanwhile,the smooth denoising algorithm is used to optimize the noise characteristics and improve the frequency resolution of the system.The channelized system has some advantages in measuring range,precision,time,dynamic range and multifrequency measuring capability,which provides a new solution for improving the overall performance of the RF signal receiving system.更多还原