Design Of 8-10G Low Phase Noise Frequency Synthesizers

Frequency Synthesizer is one of the core technologies in communication and electronic system. With the development of modern communication technology, frequency synthesizers are required to have wider band, higher resolution, faster frequency switching speed and lower spurious level. The design tried to develop high performance frequency synthesizers especially fine resolution and. low phase noise frequency synthesizers.Frequency synthesis mainly concerns about the generation of clean signals. Then we create the phase noise model and analyze the spurs of the main elements used in frequency synthesizer, such as DDS, PLL, mixer, frequency multiplier and frequency divider. By analyzing and comparing different schemes, we present a DDS+PLL scheme. DDS has the merits of high-resolution, high-accuracy, easily-control-of-frequency-variance. PLL has the excellent narrow-band-tracking-filtering characteristic. In this scheme, we combine the merits of DDS and PLL.The scheme, layout and structure are particularly thought about to achieve the high performance. Finally, suggestion was given on existing problems.