For The Application Of Satellite Navigation Receiver Automatic Gain Control Loop Design

With the rapid development of wireless communication, it makes a high requirement of RF front end circuit. Such as low power, small size, highly integrated. System on Chip (SoC) has become the main focus of wireless communication area. The structure and the performance of the RF receiver will directly affect the entire communication system.Based on the receiver RF front end of the satellite navigation system, two active image rejected Automatic Gain Control (AGC) circuit applying in a low-IF receiver system, which works under the S-band are designed using the TSMC 0.35μm SiGe BiCMOS process.In this paper, the advantage of low-IF receiver structure and the characteristic of TSMC 0.35um SiGe BiCMOS are introduced firstly; Secondly, the principal, the classification and the specification of VGA, compares different types of VGA and finally chooses the topology of VGA with linear-in-dB characteristics according the system specification. The thesis analyzes the linearity, conversion gain, noise figure, isolation and etc. affected by the topology. Because the linear-in-dB characteristic is the most important specifications of a VGA, several design techniques for VGA are discussed.The AGC loop is mainly composed of VGA with linear-in-dB characteristics, negative peak detector, loop filter and an integrator. A differential cascade type as a VGA unit cell is utilized to meet the requirement of large gain, low noise figure and so on. The AGC loop is fed from a single 3V power supply and achieves a linear gain range of 70dB. The AGC loop can settle down with its constant amplitude 1Vpp. The equivalent input noise is3.7 nV /Hz at 60dB gain. Its 3-dB bandwidth is 49MHz and power consumption is 21mW.