A high-performance low-power CMOS AGC for GPS application

Abstract

A wide tuning range, low power CMOS automatic gain control (AGC) with a simple architecture is proposed. The proposed AGC is composed of a variable gain amplifier (VGA), a comparator and a charge pump, and the dB-linear gain is controlled by the charge pump. The AGC was implemented in a 0.18 m CMOS technology. The dynamic range of the VGA is more than 55 dB, the bandwidth is 30 MHz, and the gain error is lower than ˙1.5 dB over the full temperature and gain ranges. It is designed for GPS application and is fed from a single 1.8 V power supply. The AGC power consumption is less than 5 mW, and the area of the AGC is 700 450 m 2 .

A digitally controlled AGC loop circuitry for GNSS receiver chip with a binary weighted accurate dB-linear PGA

“…The control word B varies from 0 (B 2 B 1 B 0 D 000) to 7 (B 2 B 1 B 0 D 111). Equation (10) shows that the gain varies following the squared pseudoexponential function to realize the dB-linear gain. Compared with the pseudo-exponential function expressed as A v D [(1 C t/ / (1 t /] 1=2 e t in Reference [14], the proposed FGC can provide a twice dB-linear gain range.…”

“…Simultaneously, the FGC can achieve a low gain error according to the squared pseudoexponential function. The ideal gain error for the 8 dB gain variation range of the FGC is shown in Table 2, which is calculated using Equation (10). The gain variation range of the FGC can be controlled by changing c to match the gain step of the CGC.…”

“…The ideal gain error is less than 0.03 dB according to the squared pseudo-exponential function, as shown in Table 2. Moreover, the gain of FGA is determined by B and c and is independent from process and temperature variations, according to Equation (10).…”