晶体振荡器温度补偿技术的研究

发布时间：2018-09-17 08:28

【摘要】：晶体振荡器广泛应用于宇航、仪器仪表、雷达、通信等领域。温度补偿晶体振荡器具有功耗低、启动迅速、便于集成等优势,是目前常用的振荡器之一。本文首先研究了晶体谐振器串联负载电容的等效变换。前人们采用近似计算,并对此等效变换做了一些研究。本文在推导过程中发现:提取复阻抗方程的隐含条件后,即使不采用近似计算,一个方程也能求解四个未知数。其中的隐含条件为:复阻抗方程对任意频率皆成立。最终,本文证明了此种等效变换的适用范围与谐振器Q值、谐振频率、电容比等都无关,且适用于符合Butterworth-Van Dyke(BVD)模型的所有压电谐振器。然后,本文研究了基于零相位频率的晶体谐振器等效参数测量方法。早期人们采用晶体阻抗计测量等效参数,目前国际电工委员会推荐使用矢量网络分析仪测量等效参数。由于采用了近似计算,在谐振器Q值较低时,上述方法的理论误差变大。本文提出了一种基于谐振频率、反谐振频率、负载谐振频率、负载反谐振频率测量晶体谐振器等效参数的方法。由于推导过程中没有近似计算,所以本方法不受谐振器Q值影响,仿真实验也验证了这一点。通过相位-频率曲线的导数方程解决了频率随机游动与负载电容标称值不精确问题之后,本文测量了一个5MHz晶体谐振器与一个10MHz晶体谐振器的等效参数。测试结果表明,本文方法所测等效参数与供应商提供的等效参数基本一致。由于这两个谐振器的M值、Q值皆较高,因而供应商的测试误差也会较小。因此,实测实验间接证明了本方法的有效性。本方法通过频率测量动态电阻R1,而频率是目前测量最准的物理量之一,因此本方法对提高测试精度有一定的益处。除此之外,比较成熟的频率测量方法也使得本方法操作较为简便。本文在理论上验证了此方法的优势,初步实验也验证了其可行性。接下来,本文分析了影响温度补偿晶体振荡器频率温度稳定度的主要因素——温滞效应。通过分析发现,传感器一维温度信息不能完整描述谐振器四维温度分布。这导致了同一温度对应不同的输出频率。在此基础上,本文提出了一种实时温度补偿方法,以保持测试环境的一致性。然后,本文设计了一种100MHz低相噪温度补偿晶体振荡器。实验结果表明,本实验原型的频率温度稳定度、相位噪声达到或超过国际同类产品。文末,本文分析了Trim效应。通过分析发现:Trim效应的原因是压控振荡器压控特性曲线的非线性。一个初步的实验也验证了此种推断。最后,本文分析了二维补偿技术使温度补偿晶体振荡器输出多个频率的可能性。
[Abstract]:Crystal oscillators are widely used in aerospace, instrumentation, radar, communications and other fields. Temperature-compensated crystal oscillator is one of the commonly used oscillators because of its advantages of low power consumption, quick starting and easy integration. In this paper, the equivalent transformation of the series load capacitor of crystal resonator is studied. Previous people used approximate calculation, and did some research on the equivalent transformation. In this paper, it is found that after extracting the implicit conditions of complex impedance equation, even if the approximate calculation is not used, one equation can solve four unknowns. The implicit condition is that the complex impedance equation holds for any frequency. Finally, it is proved that the applicable range of the equivalent transformation is independent of the resonator Q value, resonant frequency, capacitance ratio and so on, and it is suitable for all piezoelectric resonators in accordance with the Butterworth-Van Dyke (BVD) model. Then, the method of measuring the equivalent parameters of crystal resonator based on zero phase frequency is studied. In the early stage, the crystal impedance meter was used to measure the equivalent parameters, and the current International Electrotechnical Commission recommended the use of vector network analyzer to measure the equivalent parameters. Because of the approximate calculation, the theoretical error of the above method becomes larger when the Q value of the resonator is low. In this paper, a method for measuring the equivalent parameters of crystal resonator based on resonant frequency, antiresonant frequency and load antiresonant frequency is presented. Since there is no approximate calculation in the derivation, the method is not affected by the resonator Q value, and the simulation results show that this method is not affected by the Q value of the resonator. After solving the problem of random walk of frequency and imprecision of nominal value of load capacitance by derivative equation of phase frequency curve, the equivalent parameters of a 5MHz crystal resonator and a 10MHz crystal resonator are measured in this paper. The test results show that the equivalent parameters measured by this method are basically consistent with those provided by suppliers. Because the M value and Q value of the two resonators are both high, the testing error of the supplier will be smaller. Therefore, the effectiveness of the method is proved indirectly by the experimental results. The dynamic resistance R1 is measured by frequency, and the frequency is one of the most accurate physical quantities, so this method can improve the precision of measurement. In addition, the more mature frequency measurement method also makes this method easier to operate. In this paper, the advantages of this method are theoretically verified, and the feasibility of the method is verified by preliminary experiments. Then, the temperature hysteresis effect, which is the main factor affecting the temperature stability of the temperature compensated crystal oscillator, is analyzed. It is found that the one-dimensional temperature information of the sensor can not completely describe the four-dimensional temperature distribution of the resonator. This results in a different output frequency at the same temperature. On this basis, a real-time temperature compensation method is proposed to maintain the consistency of the test environment. Then, a 100MHz low phase noise temperature compensated crystal oscillator is designed. The experimental results show that the frequency and temperature stability and phase noise of the prototype reach or exceed those of the international products. At the end of the paper, the Trim effect is analyzed. It is found that the reason of the ratio Trim effect is the nonlinearity of the voltage-control characteristic curve of the VCO. A preliminary experiment also verifies this inference. Finally, the possibility of using two-dimensional compensation technique to output multiple frequencies of temperature compensated crystal oscillator is analyzed.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN752

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