应用于OFDM超宽带系统中的0.18μm G_m-C滤波器和可变增益放大器的设计

0.18μm G_m-C Filter and VGA for OFDM UWB Systems

设计了一种应用于OFDM UWB系统中的完全采用CMOS工艺的滤波器和VGA.滤波器采用5阶Chebyshev近似、G-mC biquad结构,转折频率为264 MHz,OTA采用伪差分结构以提高滤波器的线性度;VGA采用跨导增强型源级负反馈结构来控制增益,并加入源级负反馈电容进行高频补偿以拓展带宽.采用DC OffsetCorrection电路降低直流失调,并通过数字控制电容阵列(DCCA)来实现滤波器的转折频率的调谐.电路采用0.18μm CMOS工艺,1.8 V电源电压.电路的仿真结果表明滤波器和VGA系统的增益为6~48 dB,可变增益为42 dB,6 dB/step,在输入电压峰峰值为100 mV时THD小于-54 dBc,线性度为-6.35 dBV,噪声系数在通带内小于25 dB,消耗电流为30 mA.

Full CMOS filter and VGA for OFDM UWB systems are designed.5th order Chebyshev approximation and Gm-C biquad architecture are adopted the filter.The cutoff frequency is 264 MHz.OTA(Operational Transconductance Amplifier) is realized in pseudo differential topology to maximize the linearity of the filter.Architecture of transconductance enhanced source degeneration is adopted for the VGA to control the gain,together with a source degeneration capacitance to widen the bandwidth.DC offset Correction(DCOC) circ...