Millimeter wave frequency synthesizer is one of the key parts of millimeter wave radar. It is necessary and important for us to study it. In this paper, based on the analysis of the phase noise of millimeter wave PLL frequency synthesizer, the study on the W-band frequency synthesizer is made.The main contributions of this paper are presented as follows:Based on the analysis of frequency synthesis technique, three PLL schemes are discussed. Especially, the design of an X-band PLL frequency synthesizer is taken as an example in order to analyze the method of PLL with mixer. Then, the phase noise relation among the microwave RF signal, the local frequency and the PLL interim frequency is carefully studied and pointed out by the author.Phase noise is one of the most important performance indexes of frequency synthesizer. Due to the fact that millimeter wave PLL frequency synthesizer is complicated, different part's phase noise has different effect on the output signal's phase noise. In this paper, based on the phase noise analysis of millimeter wave double PLL frequency synthesizer, a new method to estimate the phase noise of millimeter wave PLL frequency synthesizer is presented by the author. In comparison with the conventional method, the new method only makes use of interim frequency without extra millimeter wave frequency source, which is very simple. In order to prove its feasibility, a 95GHz double PLL frequency synthesizer is designed. The final analysis shows that the phase noise estimated by the new method and that by the conventional method agree well.Based on the analysis of millimeter wave double PLL frequency synthesizer, the relation among the PLL interim frequency, the microwave local frequency and the millimeter wave RF signal is definitely pointed out by the author. The phase noise of millimeter wave PLL frequency synthesizer could be improved by improving the phase noise of microwave local frequency. In order to verify the conclusion, a low phase noise microwave local frequency achieved by multiplier is used in the design of a new 95GHz PLL frequency synthesizer that is based on the method of harmonic mixing. Compared with that of the conventional 95GHz double PLL frequency synthesizer, the phase noise of the new one is lower than -90dBc/Hz@10kHz, which is superior to that of the present technology using PLL in open report.DDS is an effective method to achieve hopping frequency synthesizer. In the paper, with a low phase noise microwave multiplier source as the local oscillation frequency and the output signal of DDS as the reference frequency of PLL, a microwave hopping frequency synthesizer is designed.In W-band, the frequency synthesizer can not be achieved by the sole use of DDS because of the high frequency. In this paper, with the combination of the technique of PLL, DDS and multiplier, an X-band frequency synthesizer with low phase noise is designed. Then, the microwave local frequency and the basic frequency of millimeter wave VCO are mixed through harmonic mixing to obtain millimeter wave interim frequency. After the interim frequency is locked by PLL, the W-band frequency synthesizer is finally achieved. Such W-band frequency synthesizer is characterized by nice performances, which has good foreground for its application in millimeter wave radar. |