Broadband Low Phase Noise Frequency Synthesis Technology Research

Frequency synthesis technology is one of the key components used inelectronic instruments. Now almost every electronic instrument withfantastic performance is achieved by frequency synthesis. This technologyis also widely used is many professional fields, such as communication,navigation, electric scout, disturb and anti-disturb, distant control andtest, modern instruments, and so on. Synthesizers with low phase noise,highly pure spectrum, high resolution and fast frequency jump speed arethe dominating development direction of the frequency synthesistechnology. This thesis is based on the aim of low phase noise, highresolution to study and analyze the wideband frequency source.First, this thesis presents the three frequency synthesistechnologies which are direct analog frequency synthesizer (DS), phaselocked loop (PLL) and direct digital frequency synthesizer (DDS) by theirdevelop time. After stress analyzing the characteristic of the last twomethods, we get a new way to reach the goal. It can be seemed a complexPLL. The DDS’s output is the reference of the PLL. In the loop there isan offset mixer between VCO and the integer-N divider, it is helpful toreduce the number of N which can help reduce the phase noise. In this system,the DDS part support high resolution and fast frequency jump speed, thePLL part gives low phase noise, highly pure spectrum and wide band. Theoutput of the frequency synthesizer can be3-6GHz.Second, we model the system, then simulation and optimization byprofessional software. The simulation proved the method in this paper isuseful and suitable. After the optimization we get the best loop band anddevices. At last we test the frequency synthesizer and it can reach the aim.