宽调谐范围低相位噪声的小面积VCO设计与实现

Design and Implementation of a Small-Area Voltage-Controlled Oscillator Using Wide Tuning Range and Low Phase Noise

为了解决压控振荡器的调谐范围、相位噪声、功耗和芯片面积等指标难以多重优化的问题,本文基于TSMC40 nmCMOS工艺,通过设计改进型开关电容阵列、高Q值LC谐振电路和大滤波电容等结构,实现了一种宽调谐范围低相位噪声的小面积压控振荡器.采用NMOS型负阻结构,以适应于0.9 V的低电源电压电路.将改进型开关电容阵列与可调电容相结合,获得8条工作于不同频率的子频段,通过选择合理的电容,使8个子频段首尾重叠,从而获得一段连续的振荡频率.与传统结构相比,改进型开关电容阵列添加了两个上拉电阻和一个输入端反相器,既能获得更宽的调谐范围,又可以抑制电源噪声,从而优化相位噪声.通过大滤波电容与尾电流MOS管并联构成低通滤波器,滤除共模点处的高频分量,抑制偶次谐波噪声,同时使输出波形更加对称,仿真结果表明,添加大滤波电容后相位噪声降低了3.02 dB.在满足电路要求的情况下,选择Q值更高的电感和电容提高谐振电路的品质因数,从而降低功耗.版图采用抽头电感,减少电感的使用个数,节省版图面积,降低成本.测试结果表明,在0.9 V电源电压下,压控振荡器的频率调谐范围为2.65~3.84 GHz,中心频率为3.24 GHz,在1 MHz频率偏移处的相位噪声为-109.71 dBc/Hz,功耗为10.81 m W,芯片核心面积仅为0.13 mm~2.

To obtain the multiple optimizations of the voltage-controlled oscillator’s tuning range,phase noise,power consumption,and chip area,a small-area voltage-controlled oscillator with a wide tuning range and low phase noise was realized in a TSMC 40 nm complementary metal oxide semiconductor(CMOS)process.Structures such as an improved switched capacitor array,high-Q LC resonant circuit,and large filter capacitors were used.The negative resistance structure of an N-channel metal oxide semiconductor(NMOS)was adopted to adapt to a 0.9 V low power supply voltage circuit.The improved switched capacitor array was combined with varactors to obtain eight subbands working at different frequencies.The eight sub-bands were overlapped end to end to obtain a continuous oscillation frequency by selecting reasonable capacitors.Compared with the traditional structure,the improved switched capacitor array includes two pull-up resistors and an input inverter,which can not only obtain a wider tuning range but also suppress power supply noise,thereby optimizing the phase noise.A low-pass filter was formed by connecting a large filter capacitor in parallel with the tail current MOS tube to filter out high-frequency components at the common-mode point,suppress even harmonic noise,and make the output waveform more symmetrical.Simulation results showed that the phase noise was reduced by 3.02 dB after adding a large filter capacitor.In the case of meeting the requirements of the circuit,the inductor and capacitor with a higher Q value were selected to improve the quality factor of the resonant circuit,thereby reducing power consumption.The layout used tapped inductors to reduce the number of inductors used,thereby saving the layout area and reducing costs.The measurement results showed that the tuning range of the voltage-controlled oscillator is 2.65—3.84 GHz,the center frequency is 3.24 GHz at a working supply voltage of 0.9 V,a phase noise of-109.71 dBc/Hz at a frequency offset of 1MHz can be obtained,the power consumption is 10.81 mW,and the core area of the chip is 0.13 mm2.