应用于2G/3G移动通信的多模发射机芯片的研究

【作者】 韩科锋；

【导师】 闵昊；

【作者基本信息】 复旦大学 ， 微电子学与固体电子学， 2011， 博士

【摘要】 当前,移动通信网络呈现出多模式、多频段、多速率的趋势,而现有单模手机已经不能满足这种变化,因此通过单个移动终端实现对各通信协议的支持成为现阶段的研究热点,这其中最为关键的部分是多模收发机芯片。在此背景下,本论文针对应用于2G/3G移动通信的多模发射机进行了如下研究：首先,分析了GSM、WCDMA和TD-SCDMA等现有主流移动通信的频带分布、信道划分、双工方式等,着重研究了各种制式下的数字调制方式及滤波特性；第二,分析比较了现有的发射机架构,确定采用直接变频方案作为多模发射机实现架构,针对该方案提出了基于ADS的系统级模型,并对发射机在多模应用时所需满足的各个关键指标进行了详细分析和讨论,为后续系统方案及模块电路优化提供了有价值的参考；第三,针对发射链路中的关键模块功率放大器进行了研究,包括对MOS管进行了非线性建模与分析,设计了一种输出阻抗匹配网络,其不仅可以提升功率放大器的输出功率和效率,还具有良好谐波抑制特性,然后采用0.18μm CMOS工艺完成了一款工作在1.8V、频率为900MHz的两级高效率线性功放：第四,分析了直接变频发射机中载波泄漏的原因和来源,在现有载波泄漏消除算法的基础上,提出并验证了一种基于两点估计方法的载波泄漏消除新算法,测试结果表明,该算法对载波泄漏的改善达到了31dB。同时,在分析功率检测器噪声的基础上,采用前置宽带低噪声放大器的方法实现了一款适用于载波泄漏消除应用的高性能宽带功率检测器；第五,在SMIC 0.13μm工艺下实现了一款可应用于GSM、TD-SCDMA(或WCDMA)的多频多模发射机芯片。在发射机模块电路设计中,为满足发射机较低的输出噪底要求,充分考虑了各模块电路线性度和噪声的优化,其中指出了可配置滤波器中输出噪声的优化方案；提出了一种低噪声、低失调和高线性度的可变增益中频放大器；采用源级负反馈结构混频器实现了一款低噪声、高线性度的调制器。测试结果表明,该多模发射机芯片在线性度、功率控制、输出噪底以及调制精度等方而均可满足2G/3G移动通信对多模发射机芯片的指标要求。更多还原

【Abstract】 Nowadays, mobile communications are characterized as multi-mode, multi-band and multi-rate, as a result, single user equipment (UE) can be no longer available for this trend. The UE which can support multimode applications becomes a hot topic recently both in companies and universities. The key of this UE is the transceiver that can deal with multi-mode signals. This dissertation focuses on the design of multi-mode transmitter for 2G/3G communications, espically for GSM, TD-SCDMA and WCDMA system.Firstly, the frequency bands allocations, channel definations and work modes of 2G/3G system are summarized, the digital modulation schemes for 2G/3G system is analyzed in detail.Secondly, the architectures of transmitter are discussed, among which, direct conversion transmitter (DCT) is adopted for our multi-mode transmitter solution. A system model based on DCT is proposed with the help of ADS to verify the key parameters of the transmitter chain and this way of analysis is helpful for both system design and circuit optimization.Thirdly, the design of CMOS linear power amplifier (PA) is presented which is a great challenge to a transmitter. With some explorations for non-linearity sources and analysis on output matching networks that can boost the output power of a power amplifier and reject the output harmonics, a two-stage high efficienct CMOS PA is realized in a 0.18μm CMOS technology with a 1.8V supply.Fourthly, the research on carrier leakage for DCT is also given. The reasons for carrier leakage is mathematically analyzed which reflects the sources of carrier leakage including even distortion from analog baseband. Based on the present algorithm for carrier leakage calibration, a new method with two-point estimation for carrier leakage calibration is presented and verified, as a result, a 31dB improvement is achieved. Meanwhile, a wideband power detector (PD) with high dynamic range for carrier leakage calibration is presented with a preceding LNA after noise analysis.Finally, a multi-mode, multi-band transmitter chip for GSM and TD-SCDMA (or WCDMA) applications is realized in SMIC 0.13μm CMOS 1P8M mixed-signal process. The methods for noise and linearity optimization are emphasized for the building blocks of transmitter. The work includes the noise analysis for LPF, proposal of a low noise, high linear analog variable gain amplifier and the realization of a modulator with resistive feedback. According to the measurements, the designed multi-mode transmitter can provide a high dynamic power control range of 78dB, the noise floor can also meets SAW-less requirements for TD-SCDMA and WCDMA systems. The experimental results show that the designed multi-mode transmitter can meet the requirements of design specifications in ACLR, EVM, power control range, output noise and so on for 2G/3G mobile communication applications.更多还原