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提出了一种新型低噪声、宽跟踪范围的集成分数频率合成器。该合成器采用3位3阶Σ-Δ调制器和对数字信号进行粗调、对模拟信号进行微调的宽频开关电容阵列LC压控振荡器,其中,数字和模拟调谐控制信号由4位2级并行流水线A/D转换器产生。详细分析了该合成器的结构和实现电路,并采用0.25 μm CMOS工艺实现。测试结果显示,电路在偏离载波频率10 kHz处带内相位噪声为-86.2 dBc/Hz,在偏离载波频率2 MHz处的带外相位噪声为-130 dBc/Hz,且具有小于5 Hz的频谱分辨率。
A new integrated fractional frequency synthesizer with low noise and wide tracking range is proposed. The synthesizer uses a 3-bit 3rd-order Σ-Δ modulator and a wideband switched capacitor array LC voltage controlled oscillator for coarsely adjusting the digital signal and finely adjusting the analog signal. The digital and analog tuning control signals are controlled by a 4-bit, 2-stage Parallel pipeline A / D converter. The structure and circuit implementation of this synthesizer are analyzed in detail, and implemented in 0.25 μm CMOS process. The test results show that the in-band phase noise of the circuit is -86.2 dBc / Hz at a deviation of 10 kHz from the carrier frequency and -130 dBc / Hz of the out-of-band phase noise at a frequency offset of 2 MHz from the carrier frequency with spectral discrimination of less than 5 Hz rate.