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Research on CPT Atomic Clock、Space Atomic Clock and New Technologies in the Time-Frequency Measurement and Control Field

Author: QuBaYi
Tutor: ZhouWei
School: Xi'an University of Electronic Science and Technology
Course: Measuring Technology and Instruments
Keywords: CPT bell Spaceborne bell Transmission delay Phase Coincidence Point Time Interval Measurement Frequency-locked loop
CLC: TH714.14
Type: PhD thesis
Year: 2010
Downloads: 402
Quote: 3
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Abstract

The atomic clock is based on the phenomenon of CPT (Coherent Population Trapping, Coherent Population Trapping) in recent years, a hot research topic in the international and domestic. CPT phenomenon can be developed in two different atomic clocks the CPT-Maser atomic clock and the passive CPT bell, the former is characterized by a complex structure, but accuracy and stability is very high, the latter is characterized by a very simple structure, can be realization of miniaturized atomic clocks one. Circuit subsystem described Rb CPT maser atomic clock works, the functions of the three subsystems, design and testing, the focus of research and achieve. The role of the chain circuits of CPT-Maser clock frequency is to contact the user's frequency (typically 5MHz and 10MHz) and the modulation frequency of the laser (usually half the atomic ground state hyperfine transition frequency). Low noise frequency synthesis techniques are used in high-performance atomic clocks. CPT-Maser clock in the design and implementation of a user's frequency to 100MHz phase-locked multiplier circuit 100MHz to 3.417GHz frequency synthesizer circuit, the frequency synthesizer circuit performance reached advanced domestic level. CPT-Maser atomic clocks is achieved through the power change of the detection signal of CPT-Maser locked, while CPT-Maser signal is usually less than-90dBm, a frequency of approximately 6.834 GHz, so the design of a heterodyne receiver and a detector circuit to achieve power detector . This circuit, the detector resolution, temperature stability, has a high demand to solve the above problems, by selecting a high-performance device. The analysis shows that the relationship between this part of the circuit and the whole closed-loop output frequency accuracy and stability. The servo circuit cost of the error signal processing of the output of the detector circuit to the oscillator control voltage. Designed and implemented mainly constituted by the A / D, MCU, D / A, digital servo, its main advantage is the use of the software will be able to complete the commissioning and traditional analog servo atomic clock does not have such software compensation and expanded catching function. For a 10-13 frequency accuracy and stability, the theoretical analysis of the digital servo design method. The atomic clock frequency temperature coefficient is an important parameter, the parameters of the foreign Spaceborne Rubidium has reached 10-14 orders of magnitude, while the the CPT-Maser 10-12 middleweight. The design and implementation of a software-based compensation frequency temperature coefficient. Expanding fishing circuit loop can not lock the capture of the local oscillator frequency wide atomic clock with traditional atomic clock to solve. The design and implementation of the CPT-Maser atomic clocks expanding fishing circuit. Around passive CPT bell miniaturized design suitable for miniaturization requirements of the whole design it in detail, it has the following four characteristics: First, using a VCSEL laser; using small frequency chain circuit; using digital lock laser and lock the local oscillator circuit; output using a rubidium bubble the lock lasers and lock the local oscillator. DDS, MCU PLL chip was developed based on an adaptation of miniaturization the CPT bell or other miniaturized atomic clock frequency synthesizer circuit. By means of a high-speed digital component, simplifying the design of the frequency synthesizer, with digital output frequency can be high-precision software adjustable and software to generate the FSK modulation and at the same time can be output synchronous demodulation signal, etc.. The the passive CPT bell intelligent and digitized, theoretically digitized atomic clock has the advantage of ease of production, testing, software compensation, the compensation of the temperature coefficient of frequency, non-real-time control of atomic clocks, frequency-locked loop based phase coincidence point detection and other content made experimental studies. Elaborate the spaceborne bell design features foreign spaceborne bell performance and major research units, the development level of spaceborne bell and abroad gap, foreign spaceborne minutes to the development of the technical details, and some are expected to improve We of spaceborne bell development level recommendations. Time-frequency test equipment developed and a new time-frequency signal processing techniques are time-frequency field of another research direction. The time quantization technique is a lot of test equipment based on the requirements of the resolution reached its ps middleweight. CMOS gate delay time quantitative techniques to achieve more complex, the resolution will be very difficult to continue to use the technology to improve. The use of signal delays this phenomenon time to quantify the feasibility and characteristics of the transmission medium. First analyzes the theoretical resolution and the technology for time quantization error, and affect the stability factor, and then the wire delay the resolution, accuracy, linearity experimental verification, and the temperature, signal attenuation and dispersion do the same amount of delay stability experimental study. The analysis and experiments show that quantitative techniques are based on the propagation delay time can obtain high-resolution time a new quantitative techniques, and also pointed out some of the features of the method and its application. Designed a new clock insertion technology to achieve high-resolution time interval measurement instrument. The clock insertion technology utilizes signal transmission will be stable, the law's delay characteristics, the clock signal delay section of transmission line, the transmission line is set according to the size of the design resolution discrete detection of delay completion of the D flip-flop after the clock signal and the measured time interval to begin or end signal of the coincidence detection, the size of the start or end signal of the clock signal and the measured time interval the time difference based on the location of the coincident point appears projections. The the FPGA chip EP2C5Q204 and above clock insertion technique to achieve a high-precision time interval measurement instrument to achieve the time interval measuring instrument has the advantages of high resolution, good stability. The demand for greater stability test equipment. Mainly based on DDS technology and measuring the difference frequency cycle method developed the a stable measuring instruments. Background stability better than 4.5 × 10 ^{-13 / 1s, 1.5 × 10 ^{-13 / 10s, its measurement range is 1MHz to 30MHz. Comparison with foreign products, it has the advantages of low-cost high-resolution. The current time than the pair of commonly used time interval measuring instrument as a measuring instrument, the resolution of the measuring instrument in the time interval under such conditions restricting the resolution of the time comparison. Longer than the time than the relationship between the phase matching and frequency source, proposed the use of the frequency source phase measurement indirectly completion time than on ideas and the completion of the experiments to verify the above ideas, also pointed out that this Indirect measurement advantages. Analysis of the relative phase of the frequency signal change characteristics, proposed a new generation of the second signal as a standard time signal namely the use of two frequency phase coincident points of the signal periodicity. The description and preliminary experiments on the use of dual-frequency signal phase coincidence point standard time signals, the result is that the method can be used to generate the second signal and produce a second signal stability better than 200ps. Elaborated advantage of the new method in the process of timing and that further research content. Phase-locked loop using a widely used technology to achieve locking between the two frequencies, due to their frequency relationship is often not related to that achieved by means of a frequency conversion circuit, the two the Irrelevant frequency signal processing having the same frequency or with an integer multiple of the relationship between signals. Cyclical phenomenon of phase coincidence and phase coincidence cycle and the frequency of the signal of the two frequencies appears closely related to contact between two arbitrary frequency signal, based on this principle to achieve a new type of frequency-locked loop. The general PLL advantage of the principle of state-of-the-art, easy to adjust the output frequency. The way to do theoretical description and experimental studies, the experimental results with theoretical expectations. The paper describes the working principle and design of the circuit.}}

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CLC: > Industrial Technology > Machinery and Instrument Industry > Instruments, meters > Measuring instruments > Time - measuring instruments > Benchmark ( standard ) timing equipment > Atomic clock
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