Research And Design Of Silicon-based Variable Gain Amplifiers

With the emergence of various intelligent devices,wireless transceiver systems such as wireless communication systems and radar systems have attracted widespread attention from academia and industry.In these wireless transceiver systems,the variable gain amplifier(VGA)is a very important module,which has the function of adjusting the magnitude of the signal and has a great impact on the sensitivity and dynamic range of the receiver.Therefor the research on VGA is of great significance.In order to facilitate system integration and reduce costs,the silicon-based process with the advantages of high integration,low power consumption and low cost becomes a good choice for on-chip VGA design.In addition,different application scenarios have different requirements for the gain range,bandwidth,additional phase shift and other performances of the VGA.Therefore,the design of the silicon-based VGA also has different focuses.Based on the current research results at home and abroad,this thesis proposes two silicon-based VGAs with different characteristics for different application requirements:(1)In response to the requirements of a hybrid system of radar and communication for adjustable bandwidth,a dual-mode VGA with broadband mode and narrowband mode is proposed based on the 55 nm CMOS technology.A switchable load consisting of two parallel PMOS transistors is applied in the cells of dual-mode VGA,thereby realizing adjustable bandwidth,which means that the VGA can be switched between the broadband and narrowband modes.The measured result shows that the dual-mode VGA has realized a bandwidth wider than 2.45 GHz in the broadband mode and the bandwidth in the narrowband mode is wider than 240 MHz.The core area of the chip is only 0.0256 mm2.(2)Aiming at a wireless communication system with high linearity and phase requirements,a wideband VGA with high linearity and low additional phase shift which can be used for both the transmitter and receiver is proposed based on the0.13 μm Si Ge Bi CMOS technology.The VGA achieves broadband and high linearity with the assistance of a feedback topology.The structure combining the VGA and the switching attenuator is applied for a wide gain range and low additional phase shift.The simulated results show that the VGA achieves a gain range of 32 d B in the frequency range of 3.5～11 GHz.The additional phase shift of the VGA is less than ±5 ° and the output power at 1 d B compression point is better than 12 d Bm.The VGA reduces the additional phase shift while ensures a sufficiently wide gain range,and provides a sufficiently high output power at the same time.The VGA can not only be used in both the transmitter and the receiver,but also be used as a gain compensation module in a phased array system.