The Small Step Of The S-band, Low Phase Noise Frequency Synthesizer

The subject "S-Band Frequency Synthesizer with small frequency-step and low phase noise", derives from the local oscillator source in emission channel from the project of××TTC(Tracking, Telemetering and Command) system. The integrative frequency synthesis technology of DDPLL+Douber+Mixer is adopted in the final scheme. The scheme is innovative and original not only in the technology but also in some module circuits.The hybrid frequency synthesis technology—DDS+PLL used in the subject have many advantages. Using this method, the merits of DDS such as super fine frequency resolution,easy programmed can be in combination with the excellent character of narrow-band tracing filter merits of PLL. Thereby, small frequency-step, low phase noise and specification of the frequency synthesizer can be realized. In addition, compared with the manner of direct phase-locked doubling to S-Band, the subject adopts the method of mixing two-way L-Band signal up to S-Band, which obviously reduced the deterioration of the phase noise and spurious signal output.The principle of frequency synthesis,DDS frequency synthesis,phase-locked loop frequency synthesis,DDS+PLL frequency synthesis are introduced at first in this paper. Subsequently, some questions in DDS+PLL frequency synthesis system about the concrete design are discussed. At last, the scheme of the Frequency Synthesizer, the functional realization of each module, some questions which must be paid attention to in the system design, and the ultimate testing result of this subject are represented and analyzed in detail.