S-band Dds And Its Application In W-band Frequency Source

Frequency synthesis is a key technique of radar, communication and other electrical systems for high performance implementation. The performance of many modern electrical devices and systems greatly depends on that of frequency synthesizers. Direct synthesis (DS), phase-locked loop (PLL) and direct digital synthesis (DDS) are three common techniques of frequency synthesis. DDS has advantages as high frequency switching speed and excellent frequency resolving. However, it also has disadvantages as low output frequency, narrow bandwidth and bad spur levels.First, several frequency agility projects based on DDS has been analyzed in this dissertation. With the consideration to the targets of the W-band frequency source in the system, the system project of the frequency synthesizer based on DDS and up-converting to its operating frequency band has been proposed, and the specifications of the S-band DDS was obtained according to it. Then the project of the S-band DDS has been reasoned roundly, and the feasibility about the mainly specifications as phase noise, spurious suppression has been analyzed. According to the request of the system, the DDS chip AD9858 has been chosen and the implementation of frequency hopping was controlled by the FPGA XC3S50 under the tool of Xilinx ISE using Verilog HDL coding. The power controlling chip HMC470LP3, the amplifiers, the mixers and so on have been chosen to establish the S-band up-conversion chain. Several key filters of the chain were customized after the feasibility of the specifications of the project was analyzed in detail; others were simulated and designed by software ADS and Filter-Solution.The results show that the phase noise of both two channel DDS output are less than-117dBc/Hz@10kHz. The power of the output 15xMHz is 9dBm with spurious suppression larger than 75dBc. And the power of S-band DDS output is-7.5dBm with spurious suppression superior to 55dBc, and good power varied linearity during the variation range of 0～31dB is achieved.55dBc spurious suppression caused by DDS was obtained when this S-band DDS applied to the W-band pulse frequency source; and-20.33dBm output power with good power varied linearity,50dBc spurious suppression within the range of 200MHz offset the center frequency were obtained when used in the W-band pulse hopping frequency source.