The Research Of J-Band Wideband Low Phase Noise Frequency Synthesizer

As the most crucial techniques that apply in electronic systems, a high performance frequency synthesizer is absolutely necessary that ensure modern electronic systems such as radar and communication systems to achieve high performance. The quality of frequency synthesizer will have an effect on performances of instruments,radar, navigation, communication and space systems. Along with the development of modern radar technology, high performance frequency synthesizer is required, especially for those used in the fire control radar that operates with low altitude antimissile weapon system. Because the fire control radar will extract very small target information at low altitude or extra-low altitude detection, the frequency synthesizer in the radar should provide very low phase noise and very pure spectrum signal to make sure that higher improvement factor can be got. The frequency synthesizer should have wide band and fast frequency agility for low altitude searching and low-angle tracking, so the technical development of frequency synthesizer with wide band, low phase noise and low SFDR should be paid much more attention.This paper deals with study and analysis of the wideband low phase noise frequency synthesizer at J-band. Firstly, we describe the basic theory and characteristics of various frequency synthetic technologies as well as phase noise, SFDR characteristics, and design technique of low noise and low SFDR of frequency synthesizer. Then based on the above work, we demonstrate the scheme of the J-band wideband low phase noise frequency synthesizer, give specifications of each module and circuit in the frequency synthesizer, and do research on some crucial techniques of frequency synthesizer, such as low phase noise, low SFDR, etc.. Finally, the electromagnetic compatibility design, experiment and manufacture are performed in layout and installation case of each module and circuit. The measured results show that the wideband low phase noise frequency synthesizer at J-band can achieve the following specifications:in the range of J-band, the RF signal phase noise is superior to-95dBc/Hz@1kHz, and SFDR suppression is better than-70dBc; in the range of X-band, local oscillator signal phase noise is superior to-100dBc/Hz@1kHz; SFDR suppression is better than-80dBc; and the frequency conversion time is less than or equal to1.5μs. All of these specifications have met requirements of system design are proposed in this paper:The technology of low phase noise:In design scheme, some methods including appropriate frequency distribution, selection of the crystal oscillator with ultra-low phase noise and the frequency multiplication circuit with low additional phase noise, careful design and adjustment of filtering circuit, optimization of circuit impedance match and a reduction in transmitting loss of phase noise, are used to make the phase noise of the J-band wideband low phase noise frequency synthesizer be less than or equal to-95dBc/Hz@1kHz and-100dBc/Hz@10kHz when at J-band.The technology of low SFDR:some methods including appropriate frequency distribution frequency in each module, optimization of circuit layout, strengthening the design of electro magnetic compatibility especially mutual interference among signals, appropriate design of mixing ratio, appropriate selection of filter, and effective suppression of SFDR near end, are used to make RF SFDR level of the wideband low phase noise frequency synthesizer at J-band be less than or equal to-70dBc, and SFDR level of local oscillator at X-band be less than or equal to-80dBc.The technology of standardizing design:The modules are appropriately divided according to function and frequency of each unit, and are designed according to the navy standard. The elements used in schematic circuit are appropriately selected to make the size of the wideband low phase noise frequency synthesizer be400x300x200mm3.