Based On The Research Of P Wave Receiver Intermediate Frequency Variable Gain Amplifier And Design

The strength of the signal received by antenna varies a lot in a wireless receiver, for the satellite receiver, the difference of the strongest signal and the weakest signal is about40dB. Therefore, any constant gain receiver can’t demodulate such a signal with wide energy range correctly. In order to deal with this problem, the gain of the wireless receiver should be automatically adjusted according to the received signal strength. This function is usually realized by Automatic Gain Control (AGC) loop. The variable gain amplifier (VGA) is an important part in the AGC loop. The performance of the VGA is extremely critical to the performance of receiver.The article first describes the research status of the CMOS integrated variable gain amplifier and its applications, classifications and specifications before the circuit design. Several different structures of VGA are introduced, and the corresponding advantages and disadvantages are analyzed. The most common used structures of RF receiver and the structure of receiver in this project are elaborated. Finally, a wideband high linearity VGA based on P-band receiver is designed.The architecture of VGA is designed according to the specifications of P-band receiver and analysis the key points of designing a wideband high linearity VGA. The circuit design process of trans-conductance stage, trans-impedance stage, buffer stage and DC offset cancelling stage are detailed described.The overall circuit and each module are simulated through spectre after the analysis and design of the circuit. The simulation focus on the gain control range, bandwidth, linearity and noise of the variable gain amplifier.Simulation and test results show that the present work fully satisfy the design specifications.