C-band frequency synthesizer
|School||University of Electronic Science and Technology|
|Course||Electromagnetic Field and Microwave Technology|
|Keywords||C-band PLL Phase Noise Frequency Synthesizer Mixing|
The frequency synthesizer is a key circuit, modern communication system is essential is the main source of the electronic system . The frequency synthesizer has a very wide range of applications in the field of digital communications , satellite communications , radar , navigation , aerospace , remote telemetry and high-speed instrument instrument . Countries in the world attach great importance to the study of the frequency synthesizer . Wide operating band , high frequency stability , low phase noise , low spurious , small step and high-speed frequency is the the contemporary frequency synthesizer development trend . Research C-band frequency synthesizer in satellite communications, digital television , medical equipment and other aspects of great importance , it is on this basis , the subject will be C-band low phase noise . Low spurious , high stability frequency synthesizer , a transceiver front-end local oscillator . This article briefly describes the history of the development of the frequency synthesizer , domestic and international profile , then the basic principles of the phase-locked loop frequency synthesis , phase noise , as well as traditional phase-locked loop combinations , compare their advantages and disadvantages , decided to adopt a double lock the phase ring external mixer program to achieve the C-band frequency synthesizer, the final details of the methods of analysis of this issue , it works , the debugging process and experimental results . The subject comes from a project , its transceiver module provides two levels of the local oscillator signal frequency point 1112.5MHz the first local oscillator and a frequency range of 4.7 to 5.5GHz second local oscillator . According to the requirements of system indicators , the first local oscillator phase-locked loop synthesis output directly to the desired frequency , the second local oscillator mixer program using the dual phase-locked loop outside the ring , by a reasonable choice of the frequency of the two rings , so to ensure low the spurious performance while improving the level of phase noise . This article focuses on the specific analysis of the two local oscillator circuit indicators at all levels , accounting, device selection , electromagnetic compatibility analysis , as well as in the post - circuit during the experiment encountered problems and solutions . Finally, the experimental test of two local oscillator phase noise, spurious curve . From the test results we can see , the two local oscillator are studied to meet the system indicators . The second stage of the vibration in the 4.7 to 5.5GHz 800MHz band 0.5MHz step, better than 65dBc spurious suppression in off-center carrier 10KHz phase noise better than -86dBc/Hz .