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本文提出了一种用于数字电视调谐器的宽频带分数-N频率合成器，覆盖975至1960MHz。通过自适应带宽控制和4/4.5预分频器设计，实现了快速锁定和低相位噪声，满足DVB-T标准对相位噪声和相位误差的严格要求。
Ratio Microelectronics, Shanghai, China 1 2 There is a high demand for high-performance tuners to meet the digital video broadcasting-terrestrial (DVB-T) standard. Often the DVB-T tuners employ a double-conversion zero-IF (DZIF) architecture that demands a wideband fractional-N synthesizer as the first local oscillator (LO1) to cover the frequency range of 975 to 1960MHz. This LO1 needs to meet a stringent phase-noise requirement with an adequate target phase noise of –87dBc/Hz at a 10kHz offset and integrated rms phase error less than 1° [1]. Because of the very wide frequency range, the variation of loop bandwidth may affect the phase-noise performance and loop stability. This paper presents a wideband fractional-N synthesizer whose loop bandwidth is controlled adaptively. A fast automatic frequency-control (AFC) technique which selects the subband of the VCO is proposed to reduce the residual fractional error to 1/16 of the reference frequency fref. A new 4/4.5
Lei Lu1,2, Zhichao Gong1,2, Youchun Liao2, Hao Min1, Zhangwen Tang1
Fudan University, Shanghai, China