近年來，隨著科技的發展，頻率合成器在通訊系統中除了要有良好的相位雜訊外，也需要有寬的可合成範圍，在本論文中設計了一個適用於WiMAX通訊系統中且具有寬頻合成範圍的分數型頻率合成器，其中包含了相位頻率檢測器(PFD)、充電泵(CP)以及迴路濾波器(LF)、互補式LC交錯耦合壓控振盪器(VCO)、脈衝吞噬除頻器、三角積分調變器(SDM)。在壓控振盪器的部份，加入了二進位權重式開關，已達到可調頻寬夠大；在三角積分調變器的方面，為了避免電路的不穩定發生，使用多級雜訊整形(MASH)架構。整體的鎖定時間經由模擬大約16μs，可合成的頻率為3.4~4.2GHz，適用於WiMAX通訊系統中。 Recently, with the technology develop, the frequency synthesizer has not only a good phase noise performance but also a wide synthesizable range. In the thesis, the author designs a fractional frequency synthesizer with a wide bandwidth for WiMAX communication system. This frequency synthesizer includes the phase frequency detector, charge pump, loop filter, complementary LC cross couple voltage control oscillator, pulse swallow counter divider, sigma-delta modulator. In the VCO, a binary weighted band switching capacitors skill is used to make the tuning range wide enough; in sigma-delta modulator, in order to avoid the circuit unstable, the Multi stAge Noise Shaping(MASH) architecture is adopted. The locking time in this work is about 16μs, and it can synthesize the frequency from 3.4 to 4.2 GHz and it is suitable for WiMAX communication system.
