An X-Band Ultra-Low Phase Variation Variable Gain Amplifier With Capacitive Compensation Technique
Dongwei Pang, Yan Wang, Biao Deng, Yongfeng Gui, Zongming Duan, Gang Wang
Abstract
To achieve a large gain range while minimizing the phase variation, two-stage cascaded variable gain amplifiers (VGAs) are demonstrated to achieve 31.5 dB-gain-control and 0.5 dB-linear-step at X-band in this brief. Two complementary numerical-control differential amplifiers are cross-connected to form the basic gain-cell of VGA, which can significantly enhance the differential stability, improve the isolation between the input and output ports and keep the input and output impedance constant at different gain state. Besides, a capacitive compensating network (CCN) is proposed to observably reduce the phase variation while tunning the VGA amplitude. The VGA, implemented in 130-nm CMOS technology, shows outstanding amplitude accuracy with the root mean square (rms) error of ¡ 0.2 dB, while the phase variation and rms phase error is ¡ ±2.44° and 1.2° over the frequency range of 8–12 GHz, respectively.