A Two Stage Variable-Gain Low-Noise Amplifier for X-Band in 0.18 A mu m CMOS

摘要

In this paper a variable gain low noise amplifier (VG-LNA) is designed and analyzed for X band in 0.18 A mu m CMOS technology. A two-stage structure is utilized in the proposed VG-LNA and its gain, which is controlled by an on-chip voltage (V-cnt), has continuous and almost linear variations. The required range for V-cnt can be initiated from 0.5 V, also the variations of gain doesn't ruin reflection loss (S11), return loss (S12) and noise figure (NF). The best performance of this VG-LNA is at 10 GHz frequency with 1 GHz bandwidth. In the center frequency, the maximum gain is 20.8 dB that continuously and linearly decreases to 4 dB by increasing V-cnt. Also S11 and S12 in this frequency are lower than -27 and -38 dB, respectively. NF is lower than 2 dB in the mentioned frequency range and NFmin is equal to 1.2 dB, while the third-order intercept point (IIP3) equals to 8.27 dBm in the best condition and always stays above -10 dBm. The main advantage of the proposed structure in compare with the similar structures is not only the key parameters don't ruin by the gain variations, but also increment of V-cnt operation range (0.5 V to V-dd), leads to expanding gain control range. These results are achieved while the power consumption is 8.4 mW with 1.8 V supply voltage and the chip area is 0.56 mm(2).