随着通信技术的不断提高，越来越多的通信系统正在蓬勃发展，例如物联网系统正向便携化、智能化迈进，全球卫星导航系统正向多模式兼容型、民用领域延伸。有限的频谱资源加剧了不同通信系统之间的串扰，消费类电子的兴起对电量的需求日益增高。以上这些都对射频接收机的设计提出了新的要求，在此背景下，本文研究了低功耗射频接收机模拟基带电路的关键技术，并应用于短距无线接收机与多模GNSS导航接收机两个项目当中。本文设计的短距无线接收机应用于物联网系统，属于窄带应用，设计难点在于低频的闪烁噪声与电路内部直流失调，对此本文采用了两级滤波器中间插入一级可编程增益放大器的新结构。电路主要工作包括：可编程增益放大器（PGA）、直流失调校准（DCOC）、IQ校准电路。PGA共三级，提供60dB动态范围，增益步进1dB。其中PGA2采用增强型有源负反馈结构，大大提高了增益精确度。为实现低功耗设计，DCOC采用RC隔直与数字辅助DAC相结合的方法，代替传统环路消除法；IQ校准电路采用电阻输入结构替代了传统的跨导单元输入；采用AB类运放代替传统两级密勒补偿运放以增强驱动能力。多模GNSS接收机属于宽带应用，本文主要工作是采用双二次结结构代替了传统的滤波器加PGA结构，双二次结同时实现滤波与增益控制功能，可节约一个电路模块的功耗。双二次结通过内部电阻切换，实现带宽增益可配置；通过IQ交叉电阻，实现低通与复带通模式切换。为进一步优化低功耗设计，运放设计时采用了带宽展宽技术以增大GBW。由于不同工艺拐角下RC值的变化，二次结带宽最大波动达到30%，对此本文设计了带宽调谐电路，保证RC乘积恒定。后仿与测试结果很好的验证了设计要求。短距无线接收机中，PGA增益范围5-65dB可变，最大增益误差0.15dB，功耗3.1mW。DCOC校准后电路的最大直流误差小于20mV，IQ校准下接收机镜像抑制比达到46dB，接收机噪声系数6.86dB。多模GNSS接收机中，双二次结实现最大带宽19M，提供44dB动态范围，功耗3.6mW。带宽调节电路开启后，不同工艺角下的带宽误差小于5%。通过与其他参考文献的对比，可知本文所设计的模拟基带在满足设计指标的同时，具有低功耗的优势。
With the improvement of communication technology, more and more communication systems are booming. For example, the Internet of things is becoming portable and intelligent, the global satellite navigation system is becoming multi-mode compatible, extending civilian areas. The limited spectrum exacerbates crosstalk between different communication systems, the rise of consumer electronics increases demand for power consumption. In this case, this thesis studies the key technologies of low-power analog baseband circuit. It is applied in short distance wireless receiver and multimode GNSS navigation receiver. Short distance wireless receiver is used in the Internet of things system, for narrow band application. Designing difficulty lies in the low frequency flicker noise and DC-offset. To solve this problem, this thesis adopts a new structure of two-stage filter with programmable gain amplifier inserted. Main work includes: programmable gain amplifier (PGA), DC-offset calibration (DCOC), IQ mismatch calibration. PGA provides 60 dB dynamic range with 1dB step. PGA2 uses improved source degenerated architecture, greatly improving the gain accuracy. To achieve low-power design, three improvements are made. First, RC-blocking and digital-assisted DCOC are used instead of the traditional loop elimination. Second, resistor-input IQ calibration circuit replaces the traditional transconductance-input structure. Third, Class-AB op-amp instead of traditional two-stage miller compensation op-amp is adopted to enhance driving ability. Multimode GNSS receiver belongs to broadband application, this thesis replaces the traditional filter and PGA structure with the Biquid structure. The Biquid structure realizes filtering and gain control functions at the same time, so power of one circuit module will be saved. Through internal resistor, gain and bandwidth can be configured. By IQ coupling resistor, low pass and complex band pass mode can be switched. To optimize low-power design, an Anti-Pole-splitting technique is adopted to increase GBW of op-amp. Due to the changes of RC value under different process corner, the maximum bandwidth fluctuation reaches 30%. A bandwidth tuner circuit is designed to ensure the product of RC constant.Simulation and test results verified the designing requirements very well. In short distance wireless receiver, PGA provides 5-65 dB gain range, the largest gain error is 0.15 dB，power consumption is 3.1mW. After DCOC calibration, the maximum DC-offset can be reduced to 20 mV. Image rejection ratio reaches 46dB by IQ calibration. NF of the receiver is 6.86dB. In multimode GNSS receiver, the maximum bandwidth of Biquid is 19MHz, providing 44 dB dynamic range, power consumption is 3.6mW. By bandwidth tuner circuit, the largest bandwidth error is less than 5%. Comparing with other references, the analog baseband in this thesis has the advantage of low power consumption while satisfying designing requirements.
