Research On Technology Of The Low Spurs Microwave Frequency Source

With the rapid development of frequency synthesis and phase-locked loop technology,it has been widely used in radar communication,electronic measuring instruments and other fields in recent years.The high demanding of frequency synthesis technology need wider band,lower phase noise and spurs,smaller frequency steps,shorter frequency conversion time,the output power within the band is controllable and output power with small fluctuations.This paper designed a low spurs and broadband microwave frequency source operating at 0.04~6GHz based on the phase-locked loop frequency synthesis technology,active frequency doubler technology and switching filter array structure.The balanced active frequency doubler module was designed to realize frequency expansion of 6~12GHz.In this paper,the development status of frequency synthesis technology is summarized,and the development status of phase-locked loop technology and direct digital frequency synthesis technology are briefly summarized.And the research results of frequency source at home and abroad in recent years are introduced.The basic principle and main part of the loop of proposed PLL synthesis in system are analyzed in detail.The spurious frequency source and the phase noise characteristics are analyzed,emphatically.Expanding technologies of wide band,ultra wide band signal frequency are introduced and compared.Finally,the frequency doubling mechanism of active double frequency of bipolar transistor is analyzed.Then,the detailed frequency division of the system scheme were carried out.Four steps-Estimating analysis,reasonable selection,simulation design,and simulation verification on the Spurious and phase noise of the PLL chip and other subcircuits,are employed to prove the proposed scheme.The circuits are manufactured and debugged to verify the correction of each sub circuit.Finally,the proposed system is basically meet the requirements after reasonable circuit layout,electromagnetic compatibility designing and debugging.The test results of the 0.04~6GHz low spurs microwave frequency source show that the system can realize: the phase noise is better than 87 dBc/Hz@10kHz,frequency step for 10 MHz,the proximal spur level is less than-65 dBc except for some are about-55 dBc,harmonic spurious rejection is greater than 50 dB,the output power is greater than 9.6 dBm,the power fluctuation is ?2.5dB,the dynamic change of adjustable output power is 10 dB.The test results of 6~12GHz balanced active double frequency divider show that when the input power is 0dBm,the output power is greater than-2.5dbm,the basic wave suppression is greater than 25 dB,and the third harmonic suppression is greater than 30 dB.