Ultra Broadband Fine Step High Stability Of Microwave Frequency Source

Frequency synthesizer is the key unit in modern electronic systems, and as the core component which determines the performances of the electronic devices. Not only applied in the field of communication, satellite, radar and electronic defense, it also plays a very important rule in the fields of airdrome, aviation, weather and medical devices. Super-wideband fine resolution frequency synthesizer exhibits its importance both in military and in public, so it is necessary to carry out the research.A C-band wideband frequency synthesizer is designed in the thesis, which is based on the technique of DDS and PLL. External reference source is multiplied by PLL, be the reference of the PLL by the dividers, DDS is employed in the manner of quadrature mixing, and intermediate frequency is fed through to the PLL directly without being filtered. Taking the measure of arranging the frequency logically, aliased frequencies occurring in the DDS can be avoided and low spur can be attained in the whole frequency band.First, the development of the frequency synthesizer is expatiated in the thesis, then it analyses the principle of the super-wideband mini-step frequency synthesizer in the design, especially explaining the DDS and PLL in detail. The modules of the frequency synthesizer are complemented in the design, including multiplier, circuit of DDS, circuit of PLL and circuit of quadrature mixing ect. Finally, the hardware circuit and measure results are demonstrated, the output frequency range is from3000MHz to6000MHz, and spur suppressed below-65dBc and output power is greater than10dBm. In the meanwhile, summary of the work in the paper and the improving suggestions for further research are proposed at last.