S波段低噪声VCO的研究

发布时间：2018-05-10 17:48

本文选题：可调开环滤波器 + 压控振荡器　；参考：《电子科技大学》2015年硕士论文

【摘要】：频率合成器是射频和微波测量/测试以及通信系统中的重要组成部分,而压控振荡器(VCO)是频率合成器的核心器件。射频和微波领域对频率覆盖范围宽、线性度好、相位噪声低的VCO的追求从未止步。本文首先介绍了VCO的历史及发展现状,分析了现有的几种以微带带通滤波器为谐振网络的振荡器的优缺点。接着介绍了一种宽带VCO,这种结构的VCO由以可调开环滤波器为谐振网络的反馈型振荡器扩展而来,具有频率覆盖范围宽、相位噪声低的特点。接着,本文详细介绍了可调开环滤波器以及以它为谐振网络的振荡器的设计步骤。根据振荡器的相位噪声模型,综合考虑滤波器的群时延和插损对相位噪声的影响,引入了一个衡量滤波器对振荡器相位噪声影响的参数PNFOM。以PNFOM最小为目标仿真设计了一个中心频率为2GHz的开环带通滤波器并将其扩展为可调滤波器,调谐范围的中心频率为1.7~2.3GHz。以所设计的开环滤波器为谐振器,以复数品质因数最高的频率为输出频率仿真设计了一个输出频率为1.871GHz的振荡器,并将其扩展为VCO。通过实际测试测得VCO的输出频率为1.61~2.10GHz,相位噪声为-113~-104dBc/Hz@100kHz,且线性度较高。其次,设计了一个DDS驱动混频锁相环结构的小步进频率合成器对VCO进行锁定测试。对方案进行了详细的论证,详细介绍了抑制频率合成器杂散的多种方法,证明该方案具有频率步进小,相位噪声低,杂散抑制度高的特点。最终测得频率合成器的输出频率为1620~1838MHz,频率步进为11Hz,相位噪声优于-115dBc/Hz@10kHz,杂散优于-47dBc。最后,对设计和测试中所遇到的问题进行了分析,并提出了解决方法。特别是对低噪声放大器MGA-68561严重恶化恒温晶振相位噪声的问题进行了进一步的实验研究。通过测试发现,所设计的三种基于硅BJT管的低噪声放大器对恒温晶振相位噪声的恶化小于2dB。替换了低噪声放大器之后,频率合成器的相位噪声得到了改善。
[Abstract]:Frequency synthesizer is an important part of RF, microwave measurement / test and communication system, and VCO is the core device of frequency synthesizer. The pursuit of VCO with wide frequency coverage, good linearity and low phase noise in RF and microwave fields has never stopped. In this paper, the history and development of VCO are introduced, and the advantages and disadvantages of several kinds of oscillators with microstrip bandpass filter as resonant network are analyzed. Then a wideband VCO is introduced, which is extended by a feedback oscillator with tunable open-loop filter as the resonant network. It has the characteristics of wide frequency coverage and low phase noise. Then, the tunable open-loop filter and the design steps of the oscillator with it as the resonant network are introduced in detail. Based on the phase noise model of the oscillator, a parameter PNFOM is introduced to measure the effect of filter on the phase noise of the oscillator, considering the influence of the filter group delay and the insertion loss on the phase noise. An open-loop band-pass filter with a center frequency of 2GHz is designed and expanded to tunable filter with the minimum of PNFOM as the target. The center frequency of the tunable range is 1.7 ~ 2.3GHz. Using the designed open-loop filter as the resonator and the frequency with the highest complex quality factor as the output frequency, an oscillator with an output frequency of 1.871GHz is designed and extended to VCO. The output frequency of VCO is 1.61 ~ 2.10 GHz and the phase noise is -113 ~ 104dBc / Hz-104dBcr / Hz-10kHz, and the linearity is high. Secondly, a small step frequency synthesizer driven by DDS is designed to test the VCO. The scheme is demonstrated in detail, and several methods to suppress the spurious of frequency synthesizer are introduced in detail. It is proved that the scheme has the characteristics of low frequency step, low phase noise and high spurious suppression degree. Finally, the output frequency of the frequency synthesizer is 1620t 1838MHz, the frequency step is 11Hz, the phase noise is better than -115dBc / Hz-10kHz, the spurious is better than -47dBc. Finally, the problems encountered in the design and test are analyzed, and the solutions are put forward. In particular, a further experimental study is carried out on the low noise amplifier (LNA), which seriously deteriorates the phase noise of the thermostatic crystal oscillator. It is found that the degradation of phase noise of the three kinds of low noise amplifiers based on silicon BJT transistor is less than 2 dB. The phase noise of the frequency synthesizer is improved by replacing the low noise amplifier.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN74

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