L-band Fractional Frequency Ask / Bpsk Hopping Source

The research and practice of a synthesizer based on fractional technology with no trade offs between step size and phase noise, reference feed through spurs and tuning speed, and the designing and debugging of the ASK/BPSK modulation circuits are achieved in this article.The synthesizer is based on fractional technology. Since the ordinary fractional technology exists a serious problem——fractional spurs, the basic theory of fractional synthesizer and the exact mechanism that precipitates fractional spurs are discussed in detail, on the base, an effective technology that avoid fractional spurs—ΔΣtechnology is introduced, and the mechanism of the technology is deeply analysis. Based on the theory analysis, according to analysis and summarize the feature of the spurs of the integrated synthesizer chip——SKY72300, a frequency synthesis scheme based on the chip is proposed, and the feasibility of scheme is proved, followed, the corresponding circuits are designed.According to analysis the goal of the system comprehensively, the ASK/BPSK modulation scheme based on the radio frequency SPDT switch——HMC194MS8 is proposed, and the corresponding circuits are designed and debugged.The whole system is carefully tested. The phase noise of the synthesizer measured at 10KHz is lower than -96dBc/Hz in the output frequency range, and the fractional spurs are all buried in the phase noise, only integer-N boundary spurs occur at a few output frequency. The ASK/BPSK modulation module works well.Finally, summary of the whole works are proposed, and suggestions for further researching and improving are given.