Applied To The Sdr If Amplifier And Agc Circuit

With the development of wireless communication, there have been various mode of communication protocols and standards, and almost every six months a new standard for wireless applications will be proposed. On the other hand, the increasing requirements for a variety of different services and seamlessly link between different applications of end-user makes the handheld mobile device manufacturers need to include as many other wireless standards and protocols as possible, thereby increasing the design difficulties and cost for equipment manufacturers. It is difficult to keep up with the pace of development for the device manufacturers.This paper presents the research and design of Programmable Gain Amplifier and Automatic Gain Control (AGC) circuit for the GSM/TD_SCDMA multi-mode receiver, and a MATLAB model is built to verify the design.In the condition that the existing structures of Programmable Gain Amplifier cannot fully meet the requirements of multi-mode receiver in the noise, linearity, power consumption and so on, this work presents a programmable gain amplifier structure by combining close-loop and open-loop structure together to get balanced performance. The structure has the advantage of larger bandwidth and lower power while maintaining a moderate degree of linearity and noise performance.Based on the above analysis, this paper presents the design of programmable gain amplifier circuit and other relevant modules of Automatic Gain Control (AGC) circuit including Received Signal Strength Indicator (RSSI) and DC offset cancellation module. The circuit has been integrated and verified both in GSM/TD SCDMA multi-mode receiver and LTE receiver. And the test results show that its performance satisfies the spec requirements.