射频有源正交混频器的设计

【作者】 薛茹燕；

【导师】 郭炜； 李章全；

【作者基本信息】 上海交通大学 ， 电路与系统， 2007， 硕士

【摘要】 随着CMOS工艺的发展,基于CMOS工艺的射频单片集成电路成为可能。混频器是射频前端的一个重要的模块,它的性能影响着整个系统的性能。在接收机中,混频器的噪声系数在很大程度上决定了系统的灵敏度。本文首先介绍了射频收发系统和射频接收机中的混频器,跟着介绍了本文所用到TSMC 0.18um RF CMOS工艺库,噪声的分类以及混频器的常用结构和性能参数。随后对于有源混频器中的噪声产生机制进行了深入的学习,以及由本振开关对的非理想性造成的混频器的非线性进行了学习和分析。在此基础研究了近年来提出的改善噪声系数的方法并分析了这些方法的优缺点,提出了一种基于Gilbert Cell的低噪声正交混频器的改进方法。最后,在Cadence Spectre RF环境下,使用TSMC 0.18um RF CMOS仿真显示本文提出的方法和传统的正交混频器相比在本振为5.51GHz,中频输出为10MHz时噪声系数得到了2.4dB的改善。更多还原

【Abstract】 Riding the rapid technological advancement, RFIC using CMOS technology has been increasingly popular. Among the various building blocks of an RF system, the mixer is certainly one of the most important, with its performance having a huge impact on the system performance. In a receiver, the noise figure of a mixer is crucial to the sensitivity of the overall system. This research addresses the noise issue in an active mixer design.In this paper, a general description of an RF system with various building blocks, including the mixer, is given first, followed by the TSMC 0.18um RF CMOS models used in this paper and then a summary of noise. Next is a general introduction to mixer and Gilbert Cell active mixer, which is widely used in RF system is presented. Some further study about the physical mechanism noise appear in the active mixer is described. Moreover, some analysis of the nonlinearity in local oscillator (LO) switch is present. After an expensive research work on the noise figure (NF) improvement methods in recent years, a new quadrature mixer with an inductor which is used to cancel out the effect of parasitic capacitance on noise figure is presented. Finally, some simulation results in cadence Spectre RF using TSMC 0.18um RF CMOS models are given. The simulations show that the NF of the new quadrature mixer achieved 2.4dBbetter than conventional quadrature mixer at LO and intermediate frequency (IF) are 5.51GHz and 10MHz respectively.更多还原