适用于频率综合器的宽带低相噪VCO设计

针对频率综合器在宽调谐范围下相位噪声变差的问题,设计了一款适用于频率综合器的宽调谐范围低相位噪声的压控振荡器；采用180nm BiCMOS工艺,运用可变电容阵列和开关电容阵列实现宽调谐范围；通过加入降噪模块,滤除压控振荡器产生的二次谐波和三次谐波,增大输出振幅,降低相位噪声；并在压控振荡器输出端加入输出缓冲器,降低频率综合器其他器件对压控振荡器的影响；通过Cadence软件对压控振荡器进行仿真,仿真结果表明：调谐电压为0.3~3V,压控振荡器的输出频率范围为2.3~3.5GHz；当压控振荡器的中心频率为3.31GHz时,在偏离中心频率10kHz、100kHz和1MHz处的相位噪声分别为-93.21dBc/Hz,-117.03dBc/Hz,-137.41dBc/Hz,功耗7.66mW；在较宽的频率范围内,取得良好的相位噪声抑制,提高压控振荡器的噪声性能,满足宽带低相噪频率综合器的应用需求。

Design of Broadband Low Phase Noise VCO for Frequency Synthesizer

A voltage controlled oscillator with wide tuning range and low phase noise for frequency synthesizer is designed to solve the problem of phase noise deterioration in wide tuning range. A wide tuning range is achieved by using 180nm BiCMOS process with variable capacitor array and switched capacitor array. By adding a noise reduction module, the second and third harmonics generated by the voltage controlled oscillator are filtered out, the output amplitude is increased, and the phase noise is reduced. An output buffer is added to the output of the VCO to reduce the influence of other devices of the frequency synthesizer on the VCO. Cadence software is used to simulate the VCO. The simulation results show that the tuning voltage is 0.3~3V and the output frequency range of the VCO is 2.3~3.5GHz. When the center frequency of the VCO is 3.31GHz, the phase noise at 10 kHz, 100 kHz and 1 MHz offset from the center frequency is -93.21dBc/Hz, -117.03dBc/Hz, -137.41dBc/Hz, and the power consumption is 7.66mW. In a wide frequency range, good phase noise suppression is obtained, which improves the noise performance of VCO and meets the application requirements of broadband low phase noise frequency synthesizer.