The X Band Sampling Phase Locked Dieletric Oscillator Based On Microwave Dieletric Ceramics

The frequency synthesizer is widely used in various types of microwave and millimeter wave system and wireless communication system. It is the core part of the whole system, its performance directly determines the quality of the system. The main function of frequency synthesizer is to provide the excellent vibration for the receiving system.When in the transmitter, it is used to provide emission source.In all types of frequency synthesizer, dielectric resonator oscillator is very special.The advantages and disadvantages of dielectric resonator oscillator is very obvious. It can only provide fixed frequency, but its phase noise is very good when comparing to other frequency synthesizer.its performance depends on the quality of the dielectric resonator, and dielectric resonator is usually made by microwave dielectric ceramics with high performance. x Ca Ti O3-(1-x)Nd Al O3 ceramics have excellent microwave dielectric properties and can be used to manufacture resonator, but its temperature performance is not very good. We can consider that using another dielectric material with opposite temperature coefficients Nd Al O3 ceramic to reunite with it. Now we use the solid state sinter to prepare the dielectric ceramics. To obtain the best performance,the multiple sintering temperature and multiple groups doping are usually adopted.Dielectric resonator oscillator is usually combined with the sampling phase locked loop, Then we can own a phase-locked dielectric resonator oscillator with high performance. The nearby noise performance of dielectric resonator oscillator can be improved by using this PLL, So the PDRO can meet the stringent requirements on noise performance. Because the output voltage of the sampling phase detector phase is very small, so we must design a reasonable peripheral circuit. To help the PLL lock, we must design an auxiliary lock circuit. Firstly, we use the HFSS software to build the model and simulate the dielectric resonator oscillator. We use the Multisim to design the auxiliary lock circuit: Venturi oscillation circuit. Finally use the Auto CAD software to design PCB. The result is that the output frequency is 10.2GHz, and the phase noise from the carrier 10 k Hz is-90 d Bc/Hz.The sampling phase locked dielectric oscillator can only be used to export the point frequency. In order to get the broadband frequency source, we can consider use the double loops structure. The main loop output uses integrated voltage controlledoscillator chip, and then a part of power transformed from the output terminal of the directional coupler to mix with output of the dielectric resonator oscillator. The output intermediate frequency signal enter the phase detector of the digital PLL chip, the reference frequency choose DDS. The final output frequency range is10.45GHz~11.45 GHz with step 1k Hz, the phase noise at frequency of 11.45 GHz reaches-90 d Bc/Hz@10k Hz. The results show that using this structure can realize small step, low phase noise,and wide band frequency source.