Design And Implementation Of Low Phase Noise Frequency Synthesizer Based On Chain Mixing Phase Locking Technique

Today,with the continuous development of test and measurement technology and communication technology,the local oscillator signals are more important for these electronic systems,frequency synthesizer with broadband,low phase noise and high resolution is becoming more and more important.The most important requirement of the frequency synthesizer designed in this paper is to output a frequency signal with broadband(5GHz~10GHz)and low phase noise.Phase-locked loop is a common method to design frequency synthesis,this paper determines the structure of the feedback loop of the phase-locked loop to achieve the design requirements through the analysis of its principle and structure and combined with the calculation of the index designed.In the design of the system scheme,the structure of the feedback loop is introduced from the N-divider,the interpolating mixer and the chain cascade two mixers,and the advantages and disadvantages are continuously pointed out according to the design indicators.Finally this paper chose the design of the frequency synthesizer in the structure of the feedback loop chain cascaded two mixers.This structure not only covers the entire output frequency band range well,but also reduces the 20 logN deterioration of the phase noise caused by the equivalent frequency multiplication of the reference frequency with respect to the output frequency by the structural change.This structure also uses the VCO as the frequency output of the phase-locked loop,which makes the whole system module more compact and consumes less power.The most important thing is that the frequency conversion speed is faster.The use of the reference module enables the control of wideband signal output with narrowband signal inputs.In the hardware implementation of the whole scheme,it is divided into four modules,which are a power module,a control module,a preset module,and a main loop module.In the continuous debugging of the test board,through further testing,the frequency synthesizer designed in this paper finally realizes the frequency output of 5GHz~10GHz,and its frequency switching time is satisfied within 200 us,which can realize the frequency stepping of 1Hz,the wave of non-harmonic spur is below-50 dBc,and the phase noise of each frequency band also reaches the corresponding design index.