Microwave Phase-locked Source Dbf System Design And Realization

The frequency synthesizer is an important part of the radar system. Its performance affects the overall system performance directly. With the development of radar technology, the requirements on performances of phase noise, spur, frequency conversion speed of frequency synthesizer are becoming higher and higher. In this thesis, research on X band frequency synthesizer for a digital beam forming radar is carried out. Main research works include:(1)According to the requirements of system, the implementation scheme for an X-band frequency synthesizer program based on phase-locked loop technology is proposed. It is with low phase noise, can cover the entire operating band, and has the ability to adjust the continuous reusable frequency, and its frequency can be tuned in high accuracy according to the data of speed tracking loop. In the proposed frequency synthesizer, a multi-loop mixing method is used. In the main loop, the output of direct digital frequency synthesis (DDS) is used to excite the phase-locked loop (PLL), and is mixed with microwave signal with ultra-low phase noise from the second loop. To achieve the frequency hopping function of local oscillator (LO) signal, low phase noise local oscillator signal in the second loop is generated by a digital PLL. A microwave calibration signal is generated by a down-converter in the third loop.(2) Active circuits design for the proposed frequency synthesizer is accomplished, including:three PLL and DDS circuit, an active loop filter circuit and power-supply circuit. Schematic design and PCB design are finished for all these active circuits. Then passive circuits in the proposed frequency synthesizer are designed, including:a micro-strip filter and a power splitter. Meanwhile, the structure design of the proposed frequency synthesizer is accomplished.(3)Simulation, implementation and measurement of the proposed frequency synthesizer are finished. The simulations of the micro-strip filter and the power splitter are carried out by ADS software, and the simulations of the performance of the whole loop are carried out by ADIsimPLL software. Performance of phase noise, spur, and the output power of the proposed frequency synthesizer are measured with equipments. The measurement results verify the correctness of the design.