一种用于宽带系统的可重构模拟基带电路

A Reconfigurable Analog Base Band Circuit Used in Wide Band System

介绍了一种应用于宽带系统中的可重构模拟基带电路.该电路采用全CMOS工艺,由低通滤波器和可变增益放大器2个模块构成.低通滤波器可通过模拟控制电压调谐转折频率,调谐范围130~430 MHz,不仅兼容了WiMedia与中国标准,而且适用于更高频率的模拟基带信号处理;跨导放大器采用适用于低电压和高频率的Nauta结构,讨论了该跨导结构的共模稳定电路的设计参数对滤波器频率准确性的影响.整个模拟基带链路可以通过数字控制调节增益,其可变增益范围0~44 dB,增益步长1 dB,适用于不同的传输距离.为了避免高链路增益情况下失调的影响,加入了直流失调校正电路,并讨论了直流失调校正电路对主电路增益准确性的影响以及优化设计.设计采用0.18μm CMOS工艺,1.8 V电源电压.在实现可重构功能的同时,仍然拥有零增益时12.5 dBm的IIP3,在同领域处于领先水平.

A reconfigurable analog base band circuit used in wide band system is presented.The circuit adopts all CMOS process and is composed of low pass filter（LPF） and variable gain amplifier（VGA）.The LPF can be tuned by an analog voltage to change the cutoff frequency from 130 to 430MHz,compatible for not only the WiMedia and Chinese standards but also other higher frequency standards.The operational transconductance amplifier（OTA） used in the LPF adopts the Nauta＇s architecture which is suitable for low power and high frequency.The influence of the common mode stability circuit in the OTA on the LPF performance is discussed and an optimized design is presented.The circuit has a variable gain ranging from 0 to 44dB with a 1dB gain step.The DC offset cancellation（DCOC） circuit is used to avoid offset.The impact of the DCOC on the main circuit is also discussed with the corresponding optimized design.This design uses 0.18μm CMOS process with 1.8V power supply.The circuit has a quite good IIP3 of 12.5dBm.