Research On Low Phase Noise And Low Spurious Multi-channel Frequency Source In Frequency-diverse Array Radar

Frequency diverse array radar is a new radar technique proposed in recent years.By adding small frequency offsets to each channel transmitted by the radar,the pattern of the frequency diverse array radar has characteristics of changing with position,angle and time in far field.Unlike the phased array radar,this new beam feature of the frequency diverse array radar has many unique practical advantages and broad applied backgrounds.The frequency source is a crucial component of the entire frequency diverse array radar.Its performance determines the signal quality of the entire system.Therefore,developing a high-performance frequency source has great significance for designing a frequency diverse array radar.A 9.6GHz-10 GHz eight channels coherent frequency source system,designed in this thesis,is the crucial part of project "Eight channels coherent frequency source system of frequency diverse array radar ".It adopted DDS-excited PLL structure and out-of-loop mixing structure.The switching between frequency bands can be controlled by computer software,which satisfies the system requirements.The key point of this scheme is to generate a low-phase and low-spurious 2.4GHz point-frequency signal because this signal acts as both a DDS system clock and a ring-mixed local oscillator signal.The main contents are as follows:1.The project background,the research status of frequency diverse array radar theory,and frequency synthesis technology are introduced.2.The common frequency synthesis techniques are Compared,and the DDS-excited PLL and ring out-mixing structure are chosen ultimately.3.The hardware circuits of the entire phase locked loop and the microstrip filter are designed.The whole components of frequency source are assembled completely.4.The output performances of frequency source are measured.The difficulties met in measurement are analyzed and solved.Finally,through reasonable frequency selection and loop bandwidth optimization,the output phase noise of the 2.4GHz phase-locked loop is-109dBc/Hz@1kHz,-116dBc/Hz@10kHz,and the final X-band point-frequency output achieves a phase noise of-96 d Bc/Hz@1k Hz,-105dBc/Hz@10kHz.Use the coupled microstrip filter to reduce output signal spurious and achieve-55 dBc spurious suppression.