导航接收机中混频器的设计研究

发布时间：2018-04-21 23:14

本文选题：卫星导航系统 + 混频器　；参考：《西安电子科技大学》2015年硕士论文

【摘要】：北斗卫星导航系统是我国自主研发建设的导航系统,它的建设和完善势必对国民经济和社会发展产生巨大的推动作用。地面接收终端是导航实现的关键环节,混频器作为导航接收机中的核心模块之一,其电路性能与导航接收机系统的总体性能息息相关,因此对接收机中混频器模块的设计研究具有重要意义。本文基于TSMC 0.18um RF CMOS工艺设计了一种折叠正交双平衡结构的混频器。该结构的混频器与传统的吉尔伯特单元混频器相比具有以下优点:采用折叠的开关级,提高了端口间的隔离度;采用电流源做负载,提高了混频器增益;采用共模反馈电路为混频器各个关键节点提供稳定的工作点,提高了混频器的线性度;采用同相和正交两个混频器支路共用一组射频输入端口,在实现了正交混频的同时降低了电路的功耗。本文首先阐述了接收机和混频器的理论知识。在混频器电路设计过程中,本文对传统的吉尔伯特单元混频器进行理论分析,然后对其进行了优化和改进,从而设计完成了一种折叠正交双平衡结构的有源混频器。随后本文对折叠正交双平衡混频器电路的转换增益和噪声系数两个重要指标进行了详细的理论分析,推导出影响转换增益和噪声系数的关键因素和相关参数;根据晶体管跨导效率与过驱动电压的关系曲线以及晶体管参数对增益和噪声的影响,从而确定了电路中晶体管的过驱动电压和跨导;通过分析工艺条件和晶体管参数对混频器性能的影响,确定了电路中各晶体管的沟道长度;设计共模反馈电路为混频器各个关键节点提供稳定的共模电压。本文使用ADS与Cadence软件分别对于所设计的混频器进行了前仿真、版图设计以及后仿真。ADS前仿真结果显示,在射频输入信号频点1.561GHz处,所设计的混频器转换增益为24d B,噪声系数9.3dB,三阶互调截点-19dB,线性度良好,隔离度大于150dB,功耗为3.8mA×1.8V,前仿真显示论文所设计的混频器电路完全满足设计要求。使用Virtuoso工具所设计的混频器版图面积为230um×320um,后仿真结果显示:混频器转换增益为22dB,噪声系数11dB,三阶互调截点-18dB,隔离度大于70dB,功耗3.8mA×1.8V,后仿真结果变化的主要原因是版图中寄生参数的加入影响了仿真性能。本文的研究对导航接收机中混频器的设计具有借鉴意义。
[Abstract]:Beidou satellite navigation system is a navigation system developed independently in China, and its construction and improvement will certainly have a great role in promoting the development of national economy and society. The ground receiving terminal is the key link of navigation. As one of the core modules of navigation receiver, the circuit performance of mixer is closely related to the overall performance of navigation receiver system. Therefore, it is of great significance to study the design of mixer module in receiver. Based on TSMC 0.18um RF CMOS process, a folded quadrature double balance mixer is designed in this paper. Compared with the traditional Gilbert cell mixer, the mixer with this structure has the following advantages: the folded switch level is used to improve the isolation between ports, the current source is used as the load, and the mixer gain is improved. The common-mode feedback circuit is used to provide stable operating points for each key node of the mixer, which improves the linearity of the mixer. The quadrature mixing is realized and the power consumption of the circuit is reduced. In this paper, the theoretical knowledge of receiver and mixer is introduced. In the design of mixer circuit, the traditional Gilbert unit mixer is analyzed theoretically, then optimized and improved, and an active mixer with folded quadrature dual balance structure is designed. Then, the conversion gain and noise coefficient of folded quadrature double balanced mixer circuit are analyzed in detail, and the key factors and related parameters that affect the conversion gain and noise coefficient are deduced. According to the relation curve between transistors' transconductance efficiency and overdrive voltage and the influence of transistor parameters on gain and noise, the overdrive voltage and transconductance of transistors in the circuit are determined. By analyzing the influence of process conditions and transistor parameters on the performance of the mixer, the channel length of each transistor in the circuit is determined, and a common mode feedback circuit is designed to provide stable common-mode voltage for each key node of the mixer. In this paper, ADS and Cadence software are used to simulate the mixer, layout design and post-simulation. Ads simulation results show that the RF input signal frequency point 1.561GHz, The designed mixer has a conversion gain of 24 dB, a noise coefficient of 9.3 dB, a third-order intermodulation intercept point of -19 dB, a good linearity, an isolation degree of more than 150dB and a power consumption of 3.8mA 脳 1.8 V. the pre-simulation results show that the mixer circuit designed in this paper fully meets the design requirements. The layout area of mixer designed with Virtuoso tool is 230um 脳 320um. The simulation results show that the conversion gain of mixer is 22 dB, the noise coefficient is 11 dB, the third order intermodulation intercept point is -18 dB, the isolation degree is greater than 70 dB, and the power consumption is 3.8mA 脳 1.8 V. The addition of parasitic parameters affects the simulation performance. The research in this paper can be used for reference in the design of mixer in navigation receiver.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN773;TN965.5

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