Design And Research Of Low Phase Noise Frequency Hopping Source Based On Comb Spectrum Frequency Multiplication

The frequency source is the core component of the electronic system,and it plays a very important role in aerospace,medical,wireless measurement and control,national defense,and wireless communications.With the continuous development of electronic technology,the requirements for performance indicators of frequency sources in various systems are becoming higher and higher.Frequency sources with low phase noise,miniaturization,low spurious,ultra-wideband and frequency agility have become the focus and hotspot of current research.Among them,the influence of phase noise index on each system is particularly important.It affects the receiver signal receiving sensitivity,the bit error rate and carrier frequency tracking density of the communication system,and the target discovery ability of the radar system.This paper studies and designs a low-phase noise frequency source for Doppler radar system,aiming to realize the output of low-frequency 20 MHz,200MHz,400 MHz and 1100 MHz low-phase noise frequency source and X-band 8080MHz~8180MHz in the same module.Low phase noise frequency hopping source output.It is proposed to use two-stage comb spectrum frequency multiplication and phaselocked signal mixing to achieve low phase noise frequency source output,which can be divided into the following four parts to achieve the final output result:1.Adopt step diode MP4063 to construct the first-stage comb spectrum frequency doubling circuit.A crystal oscillator with a frequency of 100 MHz and a phase noise of-155 d Bc/Hz@1k Hz is used as the reference source of the frequency doubling circuit.The strong nonlinear characteristics of the diode are used to implement the power spectrum filtering after the comb spectrum output,which achieves a low phase noise frequency source of 200 MHz,400MHz and 1100 MHz output,also provide a 600 MHz reference source for the second-stage comb spectrum doubling,to meet the development trend of miniaturization and low phase noise index requirements.2.The MP4023 step diode is used to construct the second-stage comb spectrum frequency doubling.The 600 MHz reference source provided by the first-stage frequency doubling circuit is frequency doubled to 8400 MHz,and then filtered and amplified to provide a low phase noise local oscillator signal for the X-band frequency hopping output.3.The output of the intermediate frequency hopping signal is realized by phase-locked frequency multiplication.The output frequency is 220MHz~320MHz,the frequency resolution is 10 MHz,a total of 11 frequency points,mixed with the local oscillator signal to achieve the final low phase noise frequency hopping signal of 8080MHz~8180MHz.4.Use D flip-flop to construct a five-divider circuit.The digital square wave signal divided from 100 MHz to 20 MHz is converted into a sine wave signal through an LC low-pass filter and output.In the paper,the schematic design and PCB drawing design for the scheme,and physical production and debugging,the final output result shows: the output power of 20 MHz is +10d Bm,the phase noise is better than-140 d Bc/Hz@1KHz,the output power of 200 MHz and 400 MHz +10d Bm,phase noise is better than-130 d Bc/Hz@1KHz,1100 MHz output power is 0d Bm,phase noise is better than-125 d Bc/Hz@1KHz,X-band frequency hopping signal output power is not less than +3d Bm,phase noise is better than-110 d Bc/Hz@1KHz.The test results meet the index requirements of multi-channel multi-band frequency sources,and can be applied to Doppler radar systems to provide technical support for the development of national defense technology.