Design Of Rf Front-End For Multi-Mode Dual-Band Gnss Receivers

In the representative of Global Positioning System (GPS) the single receiver of traditional mode cannot meet the growing demand for precision, how combing the other GNSS system and GPS to achieve a high-precision and real-time navigating and positioning of more stable, reliable and secure has become a hot issue in today's research. As a result, researching for multi-mode multi-band GNSS receiver is of great significance.This dissertation presents the circuit design and implementation of a multi-mode multi-band RF front-end for Global Navigation Satellite System (GNSS) receivers. The multi-mode multi-band RF front-end is composed of a pseudo-differential low noise amplifier (LNA) and down-conversion mixers, and can be configured to operate at 1.2GHz and 1.57GHz, respectively.In this thesis, a brief introduction of the navigation receiver is presented, including GNSS signal characteristics, features of sub-micron CMOS process and receiver topology. Following that, a detailed design procedure of the proposed LNA is presented. The pseudo-differential LNA incorporates an active single-ended to differential conversion using capacitive coupling compensation to improved phase and amplitude imbalance. A constant-gm biasing circuit is used to achieve a relative constant gain over process, voltage and temperature variations. Besides, the operation frequency of this LNA can be easily configured at two frequency bands to receive various navigation satellite signals. The down-conversion mixer is based on Gilbert topology. Current-bleeding technique is adopted to reduce noise figure (NF) and improve linearity performance. The proposed RF front-end circuit is implemented in TSMC 0.18μm CMOS process, occupying a die area of 0.8×0.5mm~2. Simulation results show the proposed RF front-end achieves a maximum voltage gain of 30.8dB/33dB, a NF of 2.6dB/2.64dB, and an input-referred 1dB compression point of -26dBm/-33dBm at 1.2GHz/1.57GHz band. The receiver front-end draws 4mA current from a 1.8V power supply.