K Band Frequency Synthesizer With High Stability And Its Application

With the background of microwave phase locked loop (PLL) frequency synthesizerand its application on microwave Doppler radar for respiration and heartbeat vital signsdetection, this thesis launches the research on high stability K band PLL frequencysynthesizer key technique and takes experiments of the Doppler radar for vital signsdetection.Microwave PLL frequency synthesizer is the critical components of the radar,communications, electronic countermeasures, and microwave test and measurementsystems. To achieve the twin goals of miniaturization and high stability of the K bandsignal generator, the thesis adopted a single loop PLL frequency synthesizer method.The phase noise performance is a significant indicator of its electronic equipmentsand electronic systems performance. Based on the dual-modulus prescaler architecture,this thesis analyses the principal theory of the PLL. To optimize phase noise performance,this thesis adopts the method of modeling and simulating with ADS software to guide theschematic design and circuit debug.Based on the simulation of the phase noise behavioral model, high stability K-band24.128GHz microwave signal synthesizer was realized with a single feedback loop. Thesynthesizer contains the phase and frequency detector (PFD) charge pump device, thepassive filter, and adopts fourth-order feedback topology. With the small overallsize 2cm×3.5cm×4cm, the high performance as well as output power of 7.9dBm, phasenoise of -67dBm/Hz deviating 1 kHz from the center frequency was realized. To enhancethe stability performance, lock detect circuit was adopted. The miniaturized PLL microwave signal source solved the problems such as small volume, low phase noise,high stability and high reliability.This thesis presents a novel solution of the frequency modulated triangular wavesignal by step synthesis adopting a fast-lock fractional ADF4193 single chip PLLfrequency synthesizer to overcome the problem of nonlinear triangle wave in FMCWradar. Meanwhile, this thesis designed and realized the two-way (305MHz, 1795.5MHz)PLL frequency synthesizer for the application of one certain type super heterodynereceiver oscillator signals.Combining K band PLL frequency synthesizer in the application of vital signsdetection by Doppler radar, this thesis introduces the Doppler Effect and its application,presents the principle of vital signs detection by Doppler radar, and specific analysis ofbase band signal characteristics of the Doppler micro vibration signal. Vital Signs signaldetection involves RF microwave technology, radar technology, biomedical engineeringtechnology, and it is able to penetrate non-metallic substances, no need of any sensor orelectrode for life and physical contact at a distance of physiological signals. In this thesis,the simple direct-conversion Doppler radar system architecture was adopted and theband-pass filter was designed for physiological signals. Finally, the thesis gives thehuman heartbeat signal test results and the theory explanation of the results as well.The consistency of the experimental results with the human physiological signalsindicates that high stability K band PLL frequency synthesizer used as oscillator signal ina microwave Doppler radar system for vital signs detection is effective. The thesispresents the direction of improvement of radar system structure and performancepolishing of the modules, the Doppler radar can be used for respiration and heartbeatvital signs detection of human life.