The Design Of The Automatic Gain Control Circuit In The Wireless Receiver

Automatic gain control system is the basic component which is widely used in many aspects of mobile phone terminal, hearing aids, multimedia, digital cameras,radar, satellite navigation, the intermediate frequency automatic gain control circuit is a vital part in the wireless receiver. However, the input signal of receiver, which of the signal intensity range can be changed very widely, due to the impact of a variety of factors outside, so in order to meet the requirement of reducing the input dynamic range of A/D conversion circuit and achieving the correct signal demodulation,we must adopt the automatic gain control circuit(AGC) to maintain the output signal at the constant level.In integrated circuit design, the work of analog circuit design is very difficult to achieve, because there is a compromise between linearity, signal swing, supply voltage, power, bandwidth, gain, speed, in addition, the effects of noise also need to be considered. While the digital circuit is easy to realize, because only power consumption and speed need to be considered, which is more and more get the interest of scholars in recent years. The structure of digital circuit is so simple,flexible, and easy to implement that makes the design of automatic gain control system develop from analog AGC to digital AGC, mixture AGC.The work on this paper focus on the design of automatic gain control circuit in the wireless receiver, the paper mainly includes the following five aspects:(1) Elaborate the research of background and significance of the automatic gain control system, and analyze the present situation of research and development directions at home and abroad.(2) Introduce the basic principle of the AGC, and analyze the advantages and disadvantages of the analog AGC technology and the digital AGC technology. Discuss the requirements and quality indicators of the AGC circuit design.(3) Using the TSMC 0.35 um CMOS process, a programmable generator of CMOS exponential function for AGC applications and a 106 d B wide range of CMOS current mode exponent function circuit, which can be applied to the AGC are designed and implemented, the work of simulation and verification of all circuits are achieved by using the PSPICE software.(4) Achieve the design of the unit circuit of AGC, expound the theoretical basis and the basic design requirements of the VGA core module,the PSPICE software are used to simulate and analyses the VGA circuit and the AGC circuit.(5) Introduce the layout basic processes, common tools platform and design rules,based on the TSMC 0.35 um CMOS process, the main unit layout and the AGC loop circuit layout are completed.