The Design And Implementation Of High-precision RF Signal Source Of The Ion Imprisoned System

RF signal source is the essential integral part of modern electronic field, noiseperformance and spurious suppression of the signal source directly determine theaccuracy and reliability of modern electronic system. Currently, the design of RFsignal source mainly adopts the DDS technology. DDS technology is combined withmodern digital signal processing theory and microelectronics technology, compared tothe traditional frequency synthesis technology, the frequency resolution of DDS ishigh and phase noise is low.This paper based on the application background of ion imprisoned, using DDStechnology, designs a high precision and high stability RF signal source. The signalsource system uses AD9910as the signal synthesis core chip, based on the ARM7chip STM32F103VE for controller, with excellent features of high output frequency,frequency spectrum stable, fast frequency agility, good spurious suppressionperformance and so on, and can adjust and scan the frequency, amplitude and phase,using flexible, can be well applied to the ion imprisoned.(1) Introducing the basic principle of DDS technology, analyzes thecharacteristics and spurious performance of DDS, and proposes some methods ofspurious suppression, then according to the requirements of the RF signal sourceindex, gives the overall design of the system.(2) The design of the system mainly includes hardware design and softwaredesign two parts, the hardware circuit design mainly includes clock multiplier circuit,DDS module, sub-octave band-pass filter circuit, gain amplification, NC attenuation,buffer amplifier circuit and human-computer interaction circuit.(3) Clock multiplier circuit uses external multiplier chain of×5×5×2×2tomake the10MHz reference clock double to1GHz as the system clock signal; DDSmodule uses AD9910as the core chip,;the whole output frequency band is dividedinto four small frequency for the design of filter circuit, using4road4orderButterworth sub-octave band pass filter,covering the DDS working frequency rangeby shunt selector; gain amplification and buffer amplifier all use GALI–74to design;HMC307is used to design the NC attenuation circuit;human-computer interactioncircuit includes4*4matrix keyboard, LCD12864liquid crystal display and communication with PC through USB2.0interface.(4) Software design part mainly includes the control of liquid crystal display,keyboard scanning input frequency/phase/amplitude, DDS module, sub-octave filterfrequency band selection and NC attenuation based on ARM7chip STM32F103VE.The control of DDS module is to convert the keyboard input data into frequency/phase/amplitude control word after processing, and send it into AD9910chip, then bythe processing of AD9910, looking up table, finally output sine wave signal.(5) Finally tested the system, all test results reached the source indexrequirements.