Abstract
With the rapid growth of higher data rate, integrating the analog circuit block with wide bandwidth in the baseband will be an indispensable trend in the future. On the other hand, a single circuit block which can be used for multi-standard receiver is an economic implementation way to enhance the usability of the cell phone. A CMOS variable gain amplifier (VGA) for multi-standard receiver described in this thesis aims to meet these two demands. In general, VGA is controlled by an automatic gain control (AGC) loop. As the data rate increases, the data slot which is used for the AGC loop to settle is getting smaller. A fast gain settling of the AGC loop becomes more and more important to make sure the data transfer is correct. The performance of the AGC loop can be characterized not only by a fast gain settling, but also the precise gain settling, the stable gain settling, and a low-distortion output signal. Alinear model of the AGC loop is set up and simulated with the performance of VGA modeled as the proposed one to see the dynamics of the loop. In this thesis, a proposed VGA for the multi-standard receiver is analyzed, designed, and implemented using the standard 0.18um 1P6M CMOS technology. The output signal of the VGA can be of constant signal level and contant group delay. The bandwidth of the VGA is extended from GSM 100KHz, WCDMA 2MHz to WLAN 10MHz, and designed to be adjustable for the noise and linearity concern of the total architecture. The gain of tha VGA ranges from -10dB to 20dB, and the constant bandwidth peroperty with different gain settings helps the simplification of DSP circuitry in the baseband. The total power consumption of the VGA is 2.43mW at 1.8V supply voltage. The chip area is 0.645mm x 0.465mm.